DEPARTMENT OF HEALTH
AND HUMAN SERVICES
FOOD AND DRUG
ADMINISTRATION
This transcript has
not been edited or corrected, but appears as received from the commercial
transcribing service. Accordingly the
Food and Drug Administration makes no representation as to its accuracy.
79th Meeting of:
BLOOD PRODUCTS
ADVISORY
COMMITTEE
March 18, 2004
Holiday Inn
2 Montgomery
Village Avenue
Gaithersburg, Maryland
Reported By:
CASET Associates
10201 Lee Highway, Suite
160
Fairfax, Virginia 22030
(703) 352-0091
TABLE OF CONTENTS
Page
Welcome, State of Conflict of Interest, Announcements 1
Open Committee
Discussion
Clinical Trials
for Licensing hepatitis B Immune Globulin Intravenous as Treatment to Prevent
HBV Liver Disease Following Liver Transplantation in HBV+ Recipients.
- Introduction and Background - Basil Golding, MD 6
- Presentation - Anna S. Lok, MD 11
Open Public Hearing 74
Open Committee
Discussion (Continued)
- FDA Current Thinking and Questions for Committee 99
- Committee
Discussion and Recommendations
Committee Updates:
- Current thinking on Variances to Address the 136
Specificity of Ortho HBsAg 3.0 Assays
- Gerardo Kaplan, PhD
- Summary of meeting of PHS Advisory Committee on 155
Blood Safety Availability - Jerry Holmberg,
MD
- Summary of Meeting of Transmissible Spongiform 163
Encephalopathies Advisory Committee Meeting
- David Asher, MC
- Current Thinking on Draft Guidance for Nucleic Acid 173
Testing for HIV and HCV: Testing, Product
Disposition
and Donor Deferral and Re-entry - Paul Mied,
PhD
- Current thinking on Final Guidance for Use of Nucleic 191
Aid Testing on Pooled and Individual Samples
from Donors
of Whole Blood and Blood Components to
Adequately and
Appropriately Reduce the Risk of
Transmission of HIV-1 and HCV -
Pradip Akolkar, PhD, Judy Ciaraldi, BS, MT
Open Committee
Discussion:
Supplemental
Testing for Human Immune Deficiency Virus
and Hepatitis C
Virus.
- Introduction and Background, Robin Biswas, MD 203
Indira Hewlett, PhD
- Performance of HIV and HCV Supplemental Assays
- Wendi Kuhnert, PhD 208
- Dale J. Hu, MD, MPH 224
- Susan Stramer, PhD 231
- Michael Busch, MD, PhD 255
Open Public Hearing 282
Open Committee Discussion 287
- Questions for the Committee
- Committee Discussion and Recommendations
COMMITTEE
MEMBERS:
KENRAD NELSON,
MD, Chair. Johns Hopkins
University, School of Hygiene and Public Health, Baltimore, Maryland
LINDA SMALLWOOD,
PhD, Executive Secretary.
CBER, FDA
PERLINE K.
MUCKELVENE, Committee Management Specialist. Scientific Advisors and Consultants Staff, CBER, FDA
JAMES R. ALLEN,
MD, MPH, American Social
Health Association, Research Triangle Park, North Carolina
CHARLOTTE
CUNNINGHAM-RUNDLES, MD, PhD, Mount
Sinai Medical Center, New York, New York
KENNETH DAVIS, JR,
MD, University of Cincinnati
Medical Center, Cincinnati, Ohio
DONNA M. DI
MICHELE, MD, Weill Medical
College and Graduate School of Medical Sciences, Cornell University, NY, New
York
SAMUEL DOPPELT,
MD, The Cambridge Hospital,
Cambridge, MA
JONATHAN GOLDSMITH,
MD, Immune Deficiency
Foundation, Towson, Maryland
HARVEY KLEIN, MD,
Magnuson Clinical Center,
NIH, Bethesda MD
SUMAN LAAL, PhD, New York University School of Medicine, NYC
JUDY LEW, MD, University of Florida, Gainesville, Florida
NON-VOTING INDUSTRY
REPRESENTATIVE.
MICHAEL STRONG,
PhD, BCLD, Puget Sound Blood
Ctr, Seattle WA
TEMPORARY VOTING
MEMBERS:
MARY CHAMBERLAND,
MD, MPH. NCID, CDC, Atlanta,
Georgia
LIANA HARVATH,
PhD, NHLBI, NIH, Bethesda,
Maryland
BLAINE F.
HOLLINGER, MD, Baylor
College of Medicine, Houston, Texas
JAY HOOFNAGLE,
MD, NIDDK, NIH, Bethesda,
Maryland
KATHARINE
KNOWLES, Health Information
Network, Seattle, WA
T. JAKE LIANG,
MD, NIDDK, NIH, Bethesda,
Maryland
JEANNE V. LINDEN,
MD, MPH, New York State
Department of Health, Albany, New York
DANIEL MC GEE,
PhD, Florida State
University, Tallahassee FL
KEITH C. QUIROLO,
MD, Children's Hospital and
Research Center at Oakland, Oakland, California
GEORGE B. SCHREIBER, ScD, Westat, Rockville, Maryland
DONNA S.
WHITTAKER, PhD, Lt. Colonel,
United States Army, Brooke Army Medical Service, Fort Sam Houston, Texas
P
R O C E E D I N G S (8:00 a.m.)
Agenda Item:
Welcome, Statement of Conflict of Interest, Announcements.
DR. SMALLWOOD: Good morning, and welcome to the 79th meeting of the Blood
Products Advisory Committee. I am Linda Smallwood, the executive secretary.
At this time, I will read the conflict of
interest statement regarding this meeting.
This announcement is part of the public record for the Blood Products
Advisory Committee meeting on March 18 and 19, 2004.
Pursuant to the authority granted under the
committee charter, the director of FDA's Center for Biologics Evaluation and
Research has appointed the following individuals as temporary voting members:
Drs. Mary Chamberland, Liana Harvath, Jay
Hoofnagle, Blaine Hollinger, Jake Liang, Jeanne Linden, Daniel McGee, Keith
Quirolo, George Shreiber, Donna Whittaker, and Ms. Katherine Knowles.
Based on the agenda, it has been determined
that there are no specific products being considered for approval at this
meeting.
The committee participants have been screened
for their financial interests. To
determine if any conflicts of interest existed, the agency reviewed the agenda
and all relevant financial interests reported by the leading participants.
The Food and Drug Administration has prepared
general matters waivers for the special government employees participating in
this meeting who required a waiver under Title XVIII, United States Code 208.
Because general topics impact on so many
entities, it is not prudent to recite all potential conflicts of interest at
they apply to each member.
FDA acknowledges that there may be potential
conflicts of interest but, because of the general nature of the discussions
before the committee, these potential conflicts are mitigated.
We would like to note for the record that
Dr. Michael Strong is participating in this meeting as the non-voting
industry representative, acting on behalf of the regulated industry.
Dr. Strong's appointment is not subject to
Title XVIII United States Code 208. He
is employed by Puget Sound Blood Center and, thus, has a financial interest in
his employer. He is also a researcher
for two firms that could be affected by the committee discussions.
In addition, in the interests of fairness,
FDA is disclosing that his employer, Puget Sound Blood Center, has associations
with regional hospitals and medical centers.
With regard to FDA's invited guests, the
agency has determined that the services of these guests are essential.
These are interests that are being made
public to allow meeting participants to objectively evaluate any presentations
and/or comments made by the guests.
For the discussions of topic one, related to
clinical trials for licensing hepatitis B immune globulin as a treatment to
prevent hepatitis B virus liver disease, Dr. Anna Lok is employed by the
University of Michigan Medical Center.
She is a researcher with the National
Institute of Diabetes and Digestive and Kidney Diseases, that collaborates with
NABI.
She also consults with, and is a scientific
advisor for two firms that could be affected by the committee discussions.
For the discussion of topic two, on the
effectiveness of supplemental testing, methodologies for human immune
deficiency virus, and hepatitis C virus, Dr. Susan Stramer is employed by
the American Red Cross, National Reference Laboratory of Infectious Disease.
She is a researcher, a scientific advisor,
and has financial interests in firms that could be affected by the discussions.
Dr. Wendi Kuhnert is employed by the CDC in
Atlanta, Georgia.
Dr. Michael Busch is employed by the Blood
Center of the Pacific. He is a
scientific advisor for firms that could be affected by the discussions. He also receives speaker and consulting fees
and is a principal investigator on contracts and grants with firms that could
be affected.
Dr. Dale Hu is employed by the CDC in
Atlanta.
For the discussions on topic three, on the
review of data supporting FDA's current thinking on product standards, quality
assurance, and submission requirements for platelets pheresis, Dr. German
Leparc is employed by the Florida Blood Services.
In addition, there may be speakers making
industry presentations and speakers giving committee updates on regulated
industry and other outside organizations.
These speakers have financial interests
associated with their employer and with other regulated firms. They were not screened for these conflicts
of interest.
FDA participants are aware of the need to
exclude themselves from the discussions involving specific products or firms
for which they have not been screened for conflicts of interest. Their exclusion will be noted for the public
record.
With respect to all other meeting
participants, we ask, in the interests of fairness, that you state your name,
affiliation, and address any current or previous financial involvement with any
firm whose products you wish to comment upon.
Waivers are available by written request under the freedom of
information act.
At this time, I would like to ask if any of
our participants, our committee members, or our invited consultants, if there
are any additional declarations that would need to be made.
Hearing none, I would move forward. I would
like to introduce to you the members of the Blood Products Advisory
Committee. I will call their names as
they appear on the roster and, when I call your name, would you please raise
your hand.
Chairman, Dr. Kenrad Nelson, Dr. James Allen, Dr. Kenneth Davis, Dr.
Samuel Doppelt, Dr. Harvey Klein, Dr. Suman Laal, Dr. Michael Strong.
We have with us several temporary voting
members: Dr. Mary Chamberland, Dr. Leanna Harvath, Dr. Jay Hoofnagle, Ms.
Katherine Knowles, Dr. Jake Liang, Dr. Jeanne Linden, Dr. Daniel McGee, Dr.
Keith Quirolo, Dr. George Schreiber, and Dr. Donna Whittaker. Did I omit anyone?
I would just like to bring to your attention
that out on the table there is a flyer announcing a forthcoming workshop on
radiolabeled platelets for assessment of in vivo viability of platelet
products.
This will take place on May 3, 2004, at the
Lister Hill Auditorium, and you may pick one up on the table outside.
With regard to the meeting, again, as always,
we have a very full agenda. We have
identified the topics and the expected times for those.
We will try as best we can, and probably even
better, to keep everyone on time. So, we would ask that you would adhere to
your time frames, and the committee chair will also help to see that this
happens.
At this time, I will turn the proceedings of
this meeting over to the chairman, Dr. Kenrad Nelson.
DR. NELSON:
Thank you, Dr. Smallwood.. The first topic for today is clinical trials
of licensing of hepatitis B immune globulin IV, the treatment for patients
receiving liver transplants. Dr. Basil
Golding from FDA.
Agenda Item:
Open Committee Discussion.
Clinical Trials for Licensing Hepatitis B Immune Globulin Intravenous as
Treatment to Prevent HBV Liver Disease Following Liver Transplantation in HBV+
Recipients. Introduction and
Background.
DR. GOLDING:
Good morning. Before I give my
brief presentation, I would just like to thank Dr. Anna Lok and the two other
experts who are here, Dr. Jake Liang and Dr. Jay Hoofnagle, for joining us for
this session.
Their expertise is highly valued, and I think
they will make a big difference in helping us come to the right decisions
regarding these questions, in particular Dr. Anna Lok, who is going to provide
a background to the subject.
My job, really, is to give you an idea of
what the regulatory issues are, and to indicate up front what questions are
going to be asked of the committee so that, during the actual presentation, you
will be able to have the questions at the back of your mind and you will be
able to put them in better focus.
Hopefully, that will make the process a lot easier.
So, what we are talking about are clinical
trials for hepatitis B immune globulin intravenous and, in particular, it is in
the post-transplant situations.
In terms of background, we are talking about
hepatitis B virus, which is a major cause of both acute and chronic liver
disease worldwide.
Occasionally, infection with this virus will
cause a fulminating hepatitis, or it could go on to chronic liver disease,
cirrhosis and end in liver failure. The
liver failure would then be treated by liver transplantation.
Orthotopic liver transplantation, or OLT,
often results in failure due to recurrent HBV infection of the new liver.
It is believed, by the people in the field,
that the rate of recurrent liver infection by HPV can be significantly reduced
by treatment with high dose hepatitis B immune globulin given intravenously,
either alone, or in combination with an antiviral drug.
So, hepatitis B immune globulin is a product
that is for intramuscular use. It is licensed for post-exposure to hepatitis B
virus. It could be sexual exposure,
needle stick, accidental transfusion, mucosal splash. It is given as prophylaxis.
It is also given for infants born to
hepatitis B surface antigen positive mothers, and it is used off label,
intravenously and intramuscularly to prevent recurrence following OLT.
The current standard of care for OLT in HBV
patients involves use of both HBIGIV and an antiviral drug. The FDA has not
approved either the HBIGIV alone, or in combination with the antiviral drugs.
So, trials with either modality alone may be
difficult to do prospectively because of ethical and feasibility concerns.
So, the questions that we are going to ask to
the committee, this is the first question:
In clinical trials to show efficacy for HBIGIV treatment, can hepatitis
B surface antigen seronegativity be used as the primary end points of clinical
outcome, indicating prevention of recurrent HBV disease in the transplanted
liver?
The second question: Is a single arm study for safety and
efficacy during the maintenance period -- that is, avoiding the perioperative
period -- following OLT sufficient for licensure?
The study would compare either HBIGIV with an
historic control of no treatment for 12 months, or HBIGIV plus lamivudine --
one of the antivirals, or another antiviral -- for 24 months with an historical
control of lamivudine or appropriate antiviral alone.
The reason for the difference in time is that
the breakthrough cases to the antivirals usually take at least a year to become
apparent. That is why you need a longer
follow up in this kind of trial.
The third question: What PK or pharmacokinetic studies are required for licensure:
A. To test quality of immune globulin in
normal volunteers intramuscularly or intravenously, depending on available
comparators.
So, if there is a licensed product out there
that is given IM, you would probably want to use that product and compare your
new product to the previous product using the IM route, or you could, if you
had a comparative that had been licensed for IV use, you could compare it by
doing a PK study comparing your new product to the old product by that route.
B. To
collect data that can be used to establish the frequency and level of dosing by
studying the target population. That
is, PK data in HBs Antigen-positive OLT recipients during the maintenance
period following transplant.
These PK studies would probably be different
from those, because very low levels of hepatitis B surface antigens in these
patients could conceivably change the PK profiles.
You would want to know what kind of PK
profiles you are actually getting in the target population to try to decide on
the dosage regimens.
C. Lastly, to determine whether trough levels
are useful in titrating the HBIGIV dose in individual patients.
The idea is that individuals, normal or
infected, would have different metabolic rates of immune globulin, and it may
be useful to individualize this based on some PK parameter in a particular
patients, and trough levels may be a way of doing this.
So, this concludes my presentation, and I
will now hand it over to Dr. Anna Lok.
Agenda Item:
Presentation - Anna S. Lok, MD.
DR. LOK:
Thank you very much for inviting me here. I hope that, in the next hour
or so, I will be able to provide an overview on a very complex subject that is
rapidly evolving.
First of all, I am going to talk a little bit
about the history of liver transplantation for hepatitis B with historically
poor results.
Then, the evolution of prophylaxis for
recurring hepatitis B post-liver transplantation, showing you how far we have
come in the last 10 to 15 years.
Then, what is considered to be standard of
care right now, so that hopefully this would help the panel make the necessary
decisions.
As many of you know, historically, in the
absence of any prophylactic therapy, liver transplantation for hepatitis B
results in a very high reinfection rate, approximately 80 percent when defined
as reappearance of hepatitis B surface antigen.
In those patients with recurrent infection,
they tend to have extremely high levels of virus replication, they are Antigen
positive, with very high HBV DNA levels.
In a setting of immunosuppression, these
patients progress very rapidly, with severe hepatitis, and oftentimes
progressing to cirrhosis and liver failure within the next year or two.
This therefore results in a very high
mortality, a 50 percent mortality, within one or two years
post-transplantation.
Because of the initial poor results, medicare
did not approve payment for transplantation for hepatitis B until only a few
years ago.
We have come a long way. This is largely led by the European
investigators showing that the use of hepatitis B immune globulin dramatically
changes the outcome of these patients.
Hepatitis B immune globulin in this setting
is believed to work largely by neutralizing circulating virus. This tends to be given at a time when the
patients are still in the operating room, when the damaged liver is removed,
and before the new liver is anastomosed, in the so-called anhepatic phase.
The idea is the IV infusion would mop up
unneutralized circulating virus that is preventing infection of the newly grafted
liver.
However, the early European studies have
shown that, if we give HBIG only for a short period of time -- days or a couple
of months -- what it does is only delays, and does not prevent, re-infection.
Long-term infusion, on the other hand,
decreases HBV recurrence, and also is associated with improved survival.
So, this is some data from European studies
of more than 300 patients transplanted from hepatitis B. As you can see, in the
left panel, the risk of recurrence is in the region of 75 to 80 percent, if
there is no prophylaxis, or if HBIG is only given for a short period of time.
In contrast, if HBIG is given for at least
six months, there is a dramatic reduction in the recurrence rate, down to about
30, 35 percent.
This is associated with improvement of
long-term survival such that, at a five-year time point, you get about a 75
percent survival compared to only about 45 percent survival.
Note also that, in the absence of
prophylaxis, most of the recurrence actually occurs within the first six months
and that, even in the absence of prophylaxis, there are very few cases of
recurrence after the first two years.
As I mentioned, we have really come a long
way. We started in the mid-1980s, late
1980s, using short-term HBIG.
When we realized that this only delayed, but
did not prevent, infection, people started using HBIG long term. Until very
recently, most of us would plan on suing HBIG indefinitely.
With the availability of new antiviral
agents, lamivudine, people started exploring the efficacy of antiviral agents
alone, starting before the patients get transplanted, and continuing
post-transplant.
As we have heard, the problem with lamivudine
is that the virus can select for resistant mutation. Therefore, the efficacy may be lost.
When we realized the problems with lamivudine
and drug resistance, everybody started combining lamivudine and HBIG, because
they work through different mechanisms and may have additive or synergistic
effect.
As we started using combination therapy, we
also started asking ourselves the question, with the use of antivirals, do we
still need to use HBIG forever, and do we need to use such high doses. So, some investigators started exploring a
combination, but using tapering doses of HBIG.
By 2000, by the late 1990s, when we began to
see more and more problems with lamivudine resistance, and with the
availability of new antiviral agents that are effective against lamivudine
resistant virus, we are beginning to see that sometimes patients receive triple
therapy.
They may have been started on lamivudine
initially, developed resistance to lamivudine either before or after transplant
and, therefore, got put on an additional antiviral agent that combat the
lamivudine resistant mutants, and again, HBIG is frequently used, at least
initially post-transplant.
Since the approval of adefovir, various
investigators are also exploring the use of adefovir as a first line antiviral
agent, and we really don't have much data on adefovir when used de novo.
This is really complex, as you can see. We are dealing with a moving target, which
makes design of studies very difficult, and which also makes interpretation of
data somewhat complicated.
Because of all these improvements, we have
seen dramatic improvement in survival. This is data from the European
transplant registry, taking into account all the patients transplanted from
January 1988 to December 2001.
As you can see, even though patients
transplanted in the late 1980s, early 1990s, were included in this slide,
patients transplanted for hepatitis B actually have better survival compared to
patients transplanted for hepatitis C at a 10-year time point.
That is because we really don't have the
equivalent of HBIG and effective antivirals for hepatitis C, and the 10-year
survival is in the region of 70 percent.
If we confine this data to only patients
transplanted from the mid-1990s onward, the survival is actually much better.
So, let me talk about each of these
prophylaxes individually, and focusing mostly on HBIG. As mentioned, from the
late 1980s to the late 1990s, most centers would use HBIG monotherapy.
This is, again, the European data from the
early 1990s, the initial slide that I show you, showing that, although HBIG is very
effective at reducing recurrence rate overall, there are different populations
of patients within the hepatitis B patients.
Hepatitis B is an extremely heterogeneous
disease, and the lowest of recurrence actually occurs in the patients
transplanted for fulminant hepatitis, as well as patients who have HBC
co-infection.
If you look, however, at the patients of
hepatitis B cirrhosis, the pink line here, and the yellow line here, the
patients who have hepatitis B positive cirrhosis and who are either DNA positive
or D antigen positive, still had a very high rate of recurrence, despite the
use of long-term HBIG. This actually
has 60 to about 85 percent recurrence rate in the highest risk groups.
These European studies tell us a few things.
HBIG is effective in reducing recurrence and in improving survival.
Within the whole big basket of hepatitis B
patients, the outcome varies, depending on several factors, patients with very
high levels of hepatitis B virus replication prior to transplant, those who are
antigen positive, those who are HBV DNA positive.
I note that HBV DNA positive, in the 1990s,
really means HBV DNA detection, using hybridization assays, with detection
limit of 100,000 or 1,000,000 copies per ml.
We also know that the indication for liver
transplant is an important factor. Patients transplanted for cirrhosis tend to
have a higher rate of recurrence, compared to those with fulminant hepatitis.
That is because we think that patients with
fulminant hepatitis usually have very aggressive immune response and, by the
time they present to us, frequently HBV DNA is no longer detectable. So, these patients tend to have low levels
of virus.
We also know that patients co-infected with
hepatitis D or delta tend to have a lower rate of recurrence, and that is
because delta suppresses hepatitis B virus replication.
So, one key message that we have learned is
that, the higher the level of virus replication, the more likely recurrence is
going to occur.
This is actually an update from the European
data. This is from one single center in
France, D. D. Samuel's group, where they specifically looked at patients
transplanted for cirrhosis only.
So, now they have excluded the patients with
delta co-infection and the patients with fulminant hepatitis, and 81 patients
received IV HBIG monotherapy, and the aim of maintaining anti-SB titer of more
than 100 iu per liter.
As we can see, the DNA positive patients had
a very high rate of recurrence, compared to the DNA negative patients, about 90
percent compared to 35 percent, and the DNA detection is a much better
predictor compared to e antigen.
As you can see, even in the e antigen
negative patients, if they are DNA positive before transplantation, the
recurrence rate is still very high.
Note again that most of the recurrence
occurred within the first year, with a small increase in the second year.
How do we use HBIG? This is really a complex issue.
There are, broadly, two different ways of using HBIG within the
transplant community.
Some of us use the fixed dose regimen, in
which 10,000 international units are given intravenously through an infusion
through the anhepatic phase. That is when the old liver had gone out and the
new liver hasn't been anastomosed.
We then subsequently follow by giving, again,
another 10,000 international units daily for the next seven days.
We believe that that is a time when there is
still a lot of uncirculating virus, and it is important to protect the newly
grafted liver. This is subsequently
followed with monthly doses of 10,000 international units.
The idea of using a fixed dose regimen is
really simplicity. We understand that
not all patients are alike, but given the fact that it is very difficult to
give patients a titrating dose regimen, in particular when the patients have
been discharged and they are outpatients, and they might not necessarily be
coming back to the transplant center for the HBIG dosing, it is extremely
difficult to wait for a result, and then call in to a local community hospital
a home nursing team and adjusted dose of HBIG.
Actually, there are more centers in the
United States using fixed dose regimens than a titrated dose regimen.
The titrated dose regimen appears to be more
sensible, though, although no one really has published data on how to titrate a
dose in the era where we have antiviral agents.
So, most of the data really comes from the
pre-lamivudine, pre-adefovir era. The
Europeans have decided that they would use a trough anti-HBs titer of 100 iu
per liter.
Studies at the University of Virginia have
shown that this may not be sufficient, particularly during the early
post-transplant period, and they advocate that a trough titer of more than 500
is necessary is necessary during the first week, and a trough titer of more
than 250 is necessary actually from day eight to day 90. After day 90, 100 might be sufficient.
As I have mentioned, there is a subtle issue
in whether we use a fixed dose or a titrating dose. Titrating dose is probably more logical, although logistically
more difficult.
As I will show you, fixed doses have some
problems because of marked inter- as well as intra-patient variability in the
anti-HBs titer, and the half life of the HB.
There are a number of factors that contribute
to variability. First of all, as we
would anticipate, the concentration of circulating HBs antigen -- perhaps this
is more important than the virion, because we know that the HBV makes a lot
more HBs antigen than it does the virion.
Certainly, during the first few days
post-transplant, there is still a lot of circulating virus and a lot of
circulating HBs antigen, and we expect that over time that would decline. This obviously would affect the half life.
In particular, during the perioperative, or
immediate post-operative period, this also can be affected by transfusion of
blood products, as well as also drains that we put into the patient's body to
drain out abdominal fluid.
For those of you who don't deal with
transplantation, you might see patients in whom you only had one or two units
of blood product transfusion, or you could have a disastrous situation when a
patient had 50 to 60 units of whole blood, in addition to plasma and platelets
and also some other products.
As I have mentioned, the half life of HB is
variable depending on the time in post-transplant. It is important that we really study the pharmacokinetics in the
setting of the target population, as Basil had mentioned.
If you look at half life of HB in a normal
subject, this is how long it is going to last.
If you look in the post-transplant setting, the first few days
post-transplant, the half life is extremely short, because there is still a lot
of uncirculating virus, whenever HB infusion might be going out in the
abdominal drain and being diluted out by all the blood products and bleeding.
As the patients progress further along
post-transplant, the half life becomes longer, but even after three months
post-transplant, the half life is still shorter than in a normal subject.
There is also some difference in a half life
between an e antigen positive patient, which is shorter, and an e antigen
negative patient.
I am sure if the data had been available on
HBV DNA positive versus negative, we would see an even bigger difference in the
half life.
I have also mentioned about the variability
of anti-HBs titer. This is data from a
UC San Francisco study, where they plot out 20 patients.
This really shows you how much the anti-SB
titer can vary with a fixed dose regimen.
So, 10,000 units can give you a trough titer that is almost undetectable,
to a trough titer that is more than 2,000 iu per liter, and these vertical
lines represent a spread for each individual patient.
There are also patients that you are never
able to maintain a very good titer, despite the fact that you give them the same
doses, and these few patients out here actually turn out to be patients who
subsequent develop re-infection.
This is actually a very useful tell tale
sign. Generally speaking, when a
patient is beginning to have signs of re-infection, we notice that we are not
able to maintain the titer.
As a result of all these studies, the U.S.
centers tend to say, well, we looked at the European data, they told us to use
HBIG. They are not getting the best
results, maybe because they are not using enough HBIG.
So, U.S. centers tend to use more HBIG and,
as I mentioned, most of use a fixed dose regiment. With the fixed dose regimen that I mentioned, most of the
patients are able to maintain trough titer of more than 500.
We do see a lower infection rate overall of
about 20 percent, compared to an overall re-infection rate of 35 percent in the
European studies.
The difference might be, in fact, even bigger
because, in the European centers they tend to have more patients with delta
infection, whereas delta infection is far less common in the United States.
So, let me summarize the use of high dose IV
HBIG monotherapy. Using the dose regimens that most U.S. centers use, up until
the mid to late 1990s, before antivirals became popular, using HBIG monotherapy,
we were able to decrease recurrent hepatitis B to about 20 percent and improve
survival to about 90 percent at two years.
So, an improvement from 50 percent survival
to 90 percent survival is really a major improvement, and that was really the
reason why medicare decided to reimburse transplantation for hepatitis B.
This comes at a huge price, because HBIG is
very expensive. I can never really quite figure out how much it costs, because
no one will tell you how much things cost.
We only know how much we charge outpatients or their insurance. Therefore, every medical center reports a
different figure.
With the doses that we use in the first year,
if we take into account HBIG plus the cost of IV infusion, please all this
monitoring that go into it, the charges in general would exceed $100,000.
In subsequent years when we give monthly
doses, it would be in the region of about $50,000. You can see that, if you plan on lifelong, indefinite therapy,
this is going to break the bank of most people.
We also show that HBIG monotherapy, while it
has a significant benefit overall, it has limited efficacy in cirrhotic
patients, who are antigen or DNA positive.
If you use HBIG only therapy, long-term
treatment is needed. Despite all this, we do have failures, and some of the
failures are related to S escape mutants.
These are mutations in the HBV S protein,
which reduces bonding to the anti-HBs and, therefore, these patients can still
get reinfected.
So, what are the reasons for failure? There are several reasons. One is inadequate neutralization, because
the patients have too much virus in the circulation prior to transplant, and
you are just not giving them enough HBIG.
These patients tend to develop recurrence
very early, most times within the first two or three months, and certainly
within the first six months, post transplant.
As I mentioned, sometimes, with long-term
usage of HBIG, you get selection of S escape mutants. These patients tend to develop recurrence a little later, because
you need to give HBIG for long enough to select for those resistant mutations.
There are also instances when the patients
are non-compliant, if they don't come back, they forget to show up for the HBIG
dosing. They can certainly develop
recurrence.
What about these S escape mutants? These are mutations that cluster around the
'a' determinant, which is the immunodominant epitope of the S protein. The most common mutation is a glycine to
arginine substitution, which reduces binding to the antibody.
These mutants are detected in some patients,
not everyone, because in some of them the failure is really due to inadequate
dosing.
So, the mutant S is detected in some patients
who develop recurrence, even though they keep coming back, and you know, you
document, that they have received the HBIG therapy.
We have found that these mutants are more
common in the early days, in a study using monoclonal anti-HB, not
surprisingly, compared to HBIG, which is a polyclonal antibody.
As I have mentioned, mutations tend to occur
with longer duration of therapy.
Earlier on, we had a study which showed that these mutations can be
reversed when HBIG is stopped.
Let me now move on to antivirals. As I have mentioned, one important lesson
that we have learned from the use of HBIG is that high levels of HBV
replication is the most important factor in determining whether the patient
developed recurrence or not.
So, it made sense to put the patient on an
antiviral agent that would suppress the level of virus prior to the patient
going forward to transplant.
So, we have currently two FDA approved
antiviral agents. One is lamivudine or
adefovir, and the other is adefovir dipivoxil, or hepsera.
These agents inhibit HBV replication by
competing with cCTP and, in the case of adefovir, dATP. Now, for incorporation into hepatitis B
virus DNA, they are orally administered antiviral agents that have been
approved by FDA for treatment of chronic hepatitis B, and adefovir is also
effective both in vitro and in vitro against lamivudine hepatitis B virus.
So, let's just compare these two antiviral
agents. They are administered
orally. They both are very effective in
suppressive HBV DNA, decreasing serum HBV DNA levels by about three to four
log.
In the treatment of immunocompetent patients
with chronic hepatitis B who are e antigen positive, one year of lamivudine
results in HBe antigen seroconversion in about 15 to 18 percent of patients.
Adefovir, in the dosage approved by the FDA
of 10 milligrams daily, results in an e antigen seroconversion rate of 12
percent after one year.
Lamivudine has really negligible side
effects. It is extremely well tolerated.
Adefovir, on the other hand, has been shown to be nephrotoxic at high doses,
and when used for long durations of time.
So, there are really some potential concerns
in a setting of patients with decompensated cirrhosis, who are already very
prone to develop renal problems because of the side effects of diuretics and
the potential for hepatorenal syndrome in a post-transplant setting, where they
are concomitantly receiving other nephrotoxic medications, such as cyclosporins
or tetralimers.
The problem with lamivudine, though, is that
there are big issues with drug resistance, 15 to 25 percent in year one and,
with continued therapy, up to 70 percent in year five.
With adefovir dipivoxil, the 10 milligram
dose, we have not seen drug resistance at the end of year one, but drug
resistance begins to emerge later on and, at year two, it has been reported in
the region of two to three percent.
Well, have these drugs been used in patients
with decompensated cirrhosis and recurrent hepatitis B post-transplant?
The answer is yes although, in the case of
adefovir, the data is really mostly on patients who have developed lamivudine
resistance, and adefovir was added as a sort of salvage therapy.
Well, let me now then share some of the data
on lamivudine monotherapy. As I have
mentioned, initially when lamivudine became available, everyone was very
optimistic. This is a wonder drug, it
rapidly reduces the level of virus and maybe lamivudine alone is going to take
care of the job and, boy, wouldn't life be easy. One pill a day and it is a lot cheaper.
Well, this, as I mentioned, is orally
administered, negligible side effects, and effective in reducing the viral
level.
You say, so what. Well, the suppression of viral level is not just a cosmetic
effect. In fact, it does reduce, in both biochemical as well as clinical
improvement of liver disease.
We, as well as many other centers, have
observed that this improvement might allow us to delay the need for transplant
and, in some patients, actually take them off the transplant waiting list, because
they are doing so well, they don't need the transplant any more.
So, we do see improvement in survival, and we
certainly see that, in some patients, this results in reduced risk of
recurrence after transplantation, because the patients go to the operating room
with less virus in their circulation.
So, let me share with you one study. This is one of the early studies from a
Canadian group, where they looked at 35 patients with decompensated cirrhosis.
They were put on lamivudine therapy. These
were patients who were all about to die.
Quite naturally, some of these patients don't make it.
So, early on, during the first six months,
five patients die from liver failure, and seven patients went ahead and had
liver transplant, because they needed it.
Of the 23 patients who actually toughed it
out and were on treatment for at least six months, 22 out of these 23 patients
had improvement based on decrease in the Chow Turcott Peer(?) score.
For those of you who are not familiar with
this, this is actually a scoring system which includes two clinical variables,
a situs, encephalopathy, and three laboratory variables -- albumen, bilirubin
and perfromen time.
So, this is actually a measure of clinical,
as well as biochemical, improvement.
One of these patients then went on to transplant.
These 22 patients have been followed for more
than a year, and 20 patients were still alive. Three of them had resistant
mutants, but there were two late deaths, one with spontaneous bacterial
peritonitis, and one with hepatocellular carcinoma.
So, this is one of those studies that show
that we can bring about clinical improvement. We can reduce the need for
transplantation, but some of these patients who are extremely sick might not
have a chance to benefit from the treatment.
This is another study. It is a retrospective analysis of 133
patients with decompensated cirrhosis put in lamivudine therapy.
You can see that, overall, the survival was
very impressive. These were patients
who were looking like they were on death's door at a time when they were
started on treatment and yet, at a three year time point, they still had 75
percent survival.
In fact, if you look carefully, the patients
split into two groups. There were some
patients who died very rapidly, within the first six months, and then there is
a group that went on and did extremely well.
These were the patients who were very, very
sick at the time of presentation. They had higher bilirubin levels. They already had some impairment in renal function
and more of these patients were HBV DNA positive.
Another issue with lamivudine in treating
patients prior to transplant is, it is not just that it takes time to work, but
we have talked about the issue of resistance.
Some of these patients have been placed on
treatment too long and they develop resistance prior to transplant. It can be a problem.
We really don't know exactly how big a
problem this is, but when you look at the case in series, you do find that they
have a higher rate of developing recurrence.
In these two European series where HBIG was
rapidly tapered post transplant, of the two patients that they followed, both
developed recurrence and here,of the three patients that they followed, three
developed recurrence.
This brings up one of the issues, that if you
identify patients with lamivudine prior to transplant, do we need a higher dose
of HBIG.
I should, however, mention that these studies
were all performed in the era before we had adefovir dipivoxil available. So, there was no other antiviral agent that
we could use as a salvage therapy in these studies.
So, lamivudine can help some patients, but
there are some limitations. As I
mentioned, there is genotypic resistance, 15, 20, 25 percent at the end of year
one, and it certainly increases with the duration of treatment.
When a patient develops resistance, there is
a risk of hepatitis flair. Liver
enzymes can go up and we can push the patients into liver failure. Now, there is also a problem of increased
risk of recurrence post-transplantation.
It does seem that, even though we improve on
the hepatic decompensation or complications of cirrhosis, the risk of
hepatocellular carcinoma persists, although it may be reduced, but this risk
does persist.
For some patients, the clinical improvement
is just way too slow. If you don't get the patients early enough, these
patients would not have a chance to benefit.
So, this is looking at the use of lamivudine
while the patients are waiting for transplants. What about continuing
lamivudine post-transplant, that you continue to suppress virus.
Even if a few virus escape and get into the
newly grafted liver, if we are able to prevent a virus from replicating and
making new virus, that would be useful.
Certainly if this approach works, it would be
far more economical, and it is a lot more convenient compared to HBIG.
However, the studies to date show that, even
though the results are pretty impressive at year one, and certainly not all
that different from HBIG monotherapy -- recurrence rate of 10 to 30 percent --
but because of issues of resistance, you get more breakthrough infection over
time.
So, recurrence rates go up to 30 or 40
percent at three years, and this is certainly not an acceptable monotherapy in
this day and age.
When patients develop resistant mutants
post-transplant, they can have rapidly progressive liver disease and die.
So, this is a slide showing several studies,
now, using lamivudine monotherapy. So,
HBIG was not given to these patients.
These patients received varying durations of
lamivudine prior to transplant, they were continued on the lamivudine post
transplant, with a single dose of HBIG.
You can see that most of these studies
involve a small number of patients, except for this study, and some of these
studies involve very short durations of follow up.
The studies with shorter rates of follow up
report better results with lower recurrence rates, where some studies with
longer duration of follow up show a recurrence rate of 35, 40 percent would be
seen, and that is why lamivudine monotherapy is no longer acceptable.
As I have mentioned, if HBIG alone, if
lamivudine alone, work, why don't we combine the two together?
Well, this is a busy slide, but all you
really need to do is focus on the blue columns. This slide really illustrates many different studies using a
combination of lamivudine and HBIG in preventing HBV recurrence after
transplant.
In all these studies, patients were put on
lamivudine for varying durations of time during transplant. Lamivudine was continued post-transplant.
HBIG was given in the operating room and
continued post-transplant. When you
look at recurrent rates, we note that you have several studies, most of them
small studies, where they reported some sero recurrence rates.
In these two studies with a higher recurrence
rate, all of the recurrence occur in patients with prior lamivudine resistance.
So, patients who did not have prior
lamivudine resistance did not develop recurrence. So, with combination therapy, we are actually able to get the
recurrence rate down to extremely low levels.
What is interesting, though, is to look at
how much HBIG is used in the era of combination therapy. This study from UCLA continued to use very
high dose HBIG, 80,000 international units during the first month and 10,000
international units for each subsequent month.
Now, this is a cheap version of the regimen.
. This is an Australia New Zealand study.
The Australian New Zealand government says, okay, for every patient you
transplant, you get a fixed sum of money and you figure out how to do it.
So, our colleagues down south decided they
would ration out the HBIG. You can see
they were using very little.
They were using 1,600 to 3,200 in the first
month and 600 to 800 units in each subsequent month, compared to 10,000 units
here. Yet, the results appear to be
very comparable.
Before you jump to the conclusion that a
sprinkle of HBIG is going to be sufficient, we have to really understand that
somehow they managed to get the patients transplanted very quickly down south,
and most of the patients had only been on lamivudine a couple of months prior
to transplantation.
So, they weren't really dealing with issues
of lamivudine resistance by and far, and that might allow them to use less
HBIG, I think.
Graft in patients survival now is similar, if
not better, than patients transplanted for other liver disease. We certainly have much better results than
transplantation for hepatitis C patients.
A big question these days is, well, if we
have lamivudine and we have adefovir and maybe next year FDA approves another
antiviral agent for hepatitis B, how much HBIG is really needed.
Can we ever discontinue HBIG and maintain the
patients on antiviral? If so, who are
the patients that we can cut out HBIG, when should we be cutting it out, and
how should we maintain the patients on long-term prophylaxis. These are questions for which we don't have
very good answers yet.
Let me share with you some attempts at
addressing those questions. This is data from the UC San Francisco group.
They used some combination therapy and they
said, gee, if we use combination therapy, all that we need to do is really give
HBIG for six months and then we can stop.
They had 26 patients, with a mean follow up
of about two years post-transplant, and two of the 26 patients developed
recurrence. We don't really have
long-term follow up data on those patients.
So, after they had two cases of recurrence
they said, well, maybe six months isn't quite enough. Let's stretch the HBIG out to 12 months.
This is some data that was reported about a
year and a half ago. They had 25 patients. Lo and behold, they had identical
results, and in fact, maybe even worse results, because the follow up here is a
little shorter.
The investigators actually tried to explain
the data because, if you give a little more HBIG, you don't get any better
results.
I think it is because of the changing
field. Now lamivudine is more widely
available. Now we have patients who
have been taking lamivudine two years, three years, before they come to
transplant. So, you are dealing with a
bigger problem of lamivudine resistance.
Those two patients who had recurrence were
patients who had lamivudine resistance prior to transplant and, of course, when
you stop the HBIG, you essentially weren't giving them any prophylaxis at all.
These two patients were in the era before we had adefovir therapy.
There are other people who are even more
courageous, and these data from a Spanish group, although they are very
selective, they tried to look at lamivudine and long-term HBIG versus much
shorter term HBIG.
In this case, what they did was, they
selected for patients who were either HBV DNA undetectable at the time of
presentation or, if they were DNA positive when they put the patients on
lamivudine, the patients actually became HBV DNA negative prior to transplant.
The patients received, again, very short
durations of lamivudine prior to transplant.
They had the transplant. They
continued the combination therapy for four weeks.
So, they had one dose in the operating room,
they had daily doses for six days, and then weekly doses during the first
month.
Then the patients were randomized to stop
HBIG right after one month, or to continue the combination therapy.
What you can see, they had 32 of these
patients who went to transplant.
Twenty-nine were randomized, 14 to lamivudine only and 15 to
combination.
At month 18 post-transplant, all the patients
remained surface antigen negative, but note that they do have three patients in
one group and one patient in another group that were HBV DNA positive by PCR
assay in the serum.
I will come back to look at HBs antigen
versus HBV DNA by PCR, and they did have some patients with lamivudine
resistance.
So, longer follow up is going to be important
to find out what happened to these patients with lamivudine resistance,
although very likely, in this day and age, these patients would have been put
on adefovir therapy.
Well, there are other ways of short cutting
on HBIG, and many of us are switching to using what FDA approved. We give it IM.
Now, of course, we can't get the same
dose. What most of us do is, we give IV
initially during the early transplant period, when we most worry about patients
and, over time, as we try to taper down the dose, we switch from IV to IM.
The switch occurs at varying time points in
different studies in difference centers, but many of us who have tried to
switch when the patients are at least one year post transplant, giving the
patients doses of 1,000 to 1,500 iu, have found that we are able to maintain a
titer of 80 to 250 iu per liter, but this is in the setting of patients
receiving concomitant antiviral therapy.
We really don't know what is going to happen
if we start using this approach immediately post transplant, and in patients
and hope they have not developed resistance to antiviral in which we did not
suspect and put a patient on an appropriate second line antiviral.
So, I talk about prevention, but we can never
really get 100 percent success. So,
what happens when we fail?
When we fail, this day and age, in 2004, we
don't wait for the patients to develop bad liver disease, cirrhosis,
re-transplant them or let them die. We treat them.
We treat them because we really have good
antivirals. I really just focus on them
here, because these days the recurrence rate is only five to 10 percent, and
this is really a small number of patients that we need to treat.
It is important to really know what
prophylaxis the patients have received prior to them developing the recurrence,
to assist us in choosing the right treatment.
These days, the treatment will be mostly
lamivudine or adefovir dipivoxil therapy for patients who have not received
lamivudine before.
This slide is actually a North American
multi-center study. We are looking at
the treatment of patients who fail, who develop recurrence, because they
received HBIG only.
So, these were patients transplanted in the
1990s. They received HBIG only. When
they developed recurrence, since they have not seen lamivudine before,
lamivudine would be an effective treatment for them. As you can see, you can get a dramatic drop in the viral level,
as well as improvement in liver enzymes.
Overall, when you look at week 24 or week 52,
there is some drop in the proportion of patients who remain e antigen positive,
as well as a drop in the proportion of patients who are HBV DNA positive when
you put them on treatment.
More important, it is not just the virus
suppression. There is also improvement in liver histology. The light blue represents the patients with
reductio in necro-inflammation, and reduction in fibrosis, when you put them on
antiviral therapy and you do a re-biopsy.
So, we can improve the clinical outcome, even
in patients with recurrence, although we obviously prefer not to have
recurrence in the first instance.
Unfortunately, with lamivudine alone, you are
going to have patients who develop resistance. In this particular study, 27
percent of the patients developed resistant mutations, and when the patients
developed resistant mutations, some of them would have clinical deterioration,
due to progression of liver disease..
So, lamivudine, as a treatment for recurrent
hepatitis B, it is safe, it does suppress the virus. It can improve liver chemistry as well as liver histology, but
the issue is with resistance. When the
patients develop resistance, things can go down south very quickly.
So, what do we do with patients with
lamivudine resistance? Fortunately, we
do have new antiviral agents with proven in vivo advocacy.
Adefovir has been FDA approved, and entevacir
is being evaluated, it is still an investigational drug at this time.
Both drugs have been shown, in clinical
trials, to suppress HBV DNA levels and result in stabilization or improvement
of liver disease.
What we are going to need to deal with in the
next five years is what would be the recurrence of hepatitis B post transplant
among patients with lamivudine resistance, if we can optimally manage
them. If we recognize the patients
early and put them on salvage therapy, would we be able to reduce recurrence.
Do the patients with lamivudine resistance
need more HBIG than patients who do not have lamivudine resistance? Again, I think this would be in the context
of whether we have a second line antiviral agent or not.
So, let me show you some adefovir data. This is really data from patients who
develop recurrent hepatitis B post transplant.
They were put on adefovir and you can see that there is a dramatic drop
in the HBV DNA level.
These were patients who initially were on
lamivudine and were recognized to have breakthrough infection, and there is a
drop in the HBV DNA level.
In this study, which is recently studied, on
adefovir therapy in pre and post transplant patients with lamivudine
resistance, this is more than 300 patients, you can see that a large proportion
of these patients have normalization of liver enzymes and a drop in HBV DNA of
about 3.5 to 5.0 log.
There is also associated improvement in the
CTP score, which I have mentioned is a combination of asitis encephalopathy,
albumen, performin time, and bilirubin.
Side effects, they were treatment related,
were considered to be uncommon, but there were issues with adefovir.
As I mentioned, it is a potentially
nephrotoxic drug, and 28 percent of the pretransplant patients had increasing
serum creatinine of more than .5 milligrams per deciliter in the
post-transplant patient.
It is, however, extremely difficult to
interpret these data, because the pretransplant patients would be compensated
cirrhosis, and asitus on diuretics and are already very prone to develop renal
insufficiency, because of the diuretic therapy, as well as progressive liver
disease and hepatorenal syndrome.
Certainly, in post transplant patients, even
in the absence of adefovir, we do see some increasing creatinine over time,
because we put the patients on ne nephrotoxic antirejection therapy,
cyclosporin and tecrikuners(?). So,
whether these increases are related to adefovir or to other issues is really
difficult to sort out.
This, again, shows the proportion of patients
with increasing creatinine over time in the pre as well as the post transplant
patient. At the one year time point, it
is in the region of 15 to 25 percent.
So, in terms of adefovir in liver transplant
patients with lamivudine resistance, it does suppress the virus level. It is
associated with clinical and biochemical improvement in liver disease, but
there are issues with nephrotoxicity.
So far, all the data that we have on adefovir
in the transplant setting has been in patients with prior lamivudine
resistance. We don't really have data
on adefovir as a single antiviral in this situation.
Let me then come to the questions the FDA
posed and see what my take would be on some of these questions. I don't have very good answers.
Some of these questions are, what should be
the primary end point, when should end point be assessed, what is the standard
of care, how should studies be designed, and what is the role of PK studies.
Well, when we think of looking at prevention
of HBV re-infection post transplant, we can think of it as occurring in
difference steps.
The first step would be when the virus
reappears. The virus re-infects the new
liver. How do we know that? Well, we can find it out by testing for HBV
DNA by PCR, or we can use a very simple, old fashioned assay, testing for
hepatitis B surface antigen.
I will explain which one I would pick. If we notice, if we follow the patients very
carefully, and we realize that the virus has reappeared, we could intervene.
In fact, that should also appear here. We could interfere before the patients
develop bad liver disease. We could intervene with antiviral therapy and stop
this cascade from happening.
Of course, if we don't intervene, the
patients would then develop recurrent hepatitis, which is manifested as
elevated ALT and histological liver disease.
Again, if we stop, and we don't intervene,
the patients can go into cirrhosis, liver failure, and they can die.
A small proportion of patients can have a
very aggressive form of liver disease called fibrosin incoistatic(?) hepatitis,
which can kill them in days to weeks.
In 2004, if we were following our patients,
we would not allow our patients to go down this path. We will be monitoring the patients and, when we notice something
bad is going, we would intervene and we would start the patients on antiviral
therapy, so that this cascade is not going to happen.
Therefore, it is no longer possible to use
clinical events as end points unless you are dealing with physicians who do not
take care of their patients.
So, we have to use reinfection, not recurring
hepatitis, not death, as clinical end points.
Now, with reinfection, I would prefer -- and I think this is the
standard of care worldwide -- that we use re-detection of HBs antigen in a
serum after one month post transplant.
The first few days, no matter what you do, if
you try to test a patient for HBs antigen on day two, it might still be
detectable because you might not have completely cleared the circulating HBs
antigen. So, typically we will give it
a month.
Why do I use HBs antigen? Because it is a readily available,
standardized test. It doesn't really
matter if the patient lives 300 miles away.
We can get a test and we know that we can get
a reliable test. Any HBs antigen test
in this country, it is a fairly meaningful result.
We know that all the patients that develop
clinically significant hepatitis, if you follow the patient, HBs antigen is
detected first, before you have clinically significant hepatitis.
In fact, sometimes we see HBs antigen become
positive, and the liver enzymes are still normal, and it is two or three months
later, when the virus has sufficiently built up, that the patient now has
elevated liver enzymes and bad liver disease.
So, a key is really monitoring the patients.
Well, why don't I pick HBV DNA assays? Well, first of all, we don't have any FDA
approved HBV DNA assay. So, we don't
have any standardized assay.
The second problem is that, because of the
lack of standardization, we don't really know what we are talking about when
people say that HBV DNA is detectable, because detection in one assay might be
undetectable using another assay.
We also know that, from PCR assays, sometimes
you pick up patients in home that are intermittently positive by PCR, and then
the next time it is undetectable.
We really don't know what it means, unless it
is persistently detectable and above a certain level, and we don't really know
exactly what level is associated with clinically significant hepatitis.
I think we should have better standardized
assays, and I think we should really address this issue in terms of what level
is associated with clinically significant hepatitis. Until we have that information, I would not recommend using this
as an end point.
Let me just illustrate to you an issue of
using DNA by PCR, and this is data from D.D. Samuel's group in France, where
they have followed a large group of patients who have been maintained on HBIG
for 10 years.
These were patients who remain HBs antigen
negative, 10 years post transplantation, 44 patients. When he tried to detect HBV DNA by PCR, using the serum liver of
PBMC, you can see that anywhere from between 30 or 40 of these patients would
be PCR positive, but only one of these patients, now, who did not have
co-infection with hepatitis C actually had clinically relevant hepatitis on
liver biopsy.
So, these are surface antigen negative with
DNA detectable by PCR, but they don't really have significant liver disease
unless they have concomitant HCV co-infection, and that is the reason why I
mentioned, I am not sure how to interpret HBV DNA detection by PCR.
When do we assess the end point? HBV recurrence can occur any time after
transplantation but, as I have shown you on several slides, most of the
recurrence occurred within the first year post transplant, 80 percent
recurrence in the first year and, by the second year post transplant, you will
have picked up more than 90 percent of the recurrence.
Now, designing a clinical study using one
year or two years would be a reasonable end point. We don't necessarily need to go all the way to 10 years.
Well, what is the standard of care? I think the standard of care in 2004, and
likely in the next couple of years, would be combination prophylaxis. Most of us would put a patient on antiviral
therapy while they are waiting for transplant with the hope of decreasing virus
load prior to transplant.
Post transplant we would use the combination
therapy. We will continue the
antiviral. We will use the HBIG.
There are several potential advantages of
using combination therapy. There is
additive or synergistic antiviral effects.
We might circumvent antiviral or HBIG resistance.
It may be that we can use a much lower dose
of HBIG or shorter duration of HBIG and, therefore, increase the cost
effectiveness.
Let me share with you some of the concepts
that we have in an NIDDK-sponsored study, of which I am the PI. Our approach is that, pre-transplant, we
will check everyone for HBV DNA.
If they have extremely low or undetectable
HBV DNA, we will monitor the patients.
We are not sure how much benefit antiviral therapy would have on these
patients.
We do know that hepatitis B is a fluctuating
disease. In the course of follow up, some of these patients, who initially had
undetectable HBV DNA might now have higher levels of HBV DNA, and if we catch
them then, we will put them back into this high DNA group, and we will put them
on antiviral therapy.
Once the patients get to transplant, we
actually categorize the patients into low risk patients and high risk patients.
The low risk patients are the patients with
very low viral level prior to transplant, and who have no evidence of
lamivudine resistance.
Our concept is to test if just a very short
perioperative course of HBIG and antiviral maintenance would be sufficient.
With the high risk patients, these are
patients who have high viral load prior to transplant, or patients with
lamivudine resistance prior to transplant.
We advocate using combination therapy during
the first year and, at the end of the first year, we are actually randomizing
the patients to either stop HBIG and be maintained on antiviral therapy only,
or to continue combination therapy, but using a much lower dose of HBIG. We are actually using the IM dose of HBIG.
I can tell you that we have had numerous
problems with this study, in terms of patient enrollment. Part of the problem is that none of the
companies that make these products are willing to support the study.
So, we get the money from the NIH but,
because we don't have study medication to give out, it is very difficult to get
participating centers to follow a protocol when you don't provide a very
expensive study medication.
So, this study is fraught with problems, and
I have been constantly threatened by the DSMB that the study will be closed, if
I don't manage to find more patients.
So, how would I envision study designs? I don't really know exactly how we can do it
properly, because this is a very complex field and it is a rapidly moving
field.
Ideally, if you are really trying to address
what good does HBIG do, you want to compare with nothing. This is impossible.
Unless we can turn the clock back to the
early 1980s, we cannot do a study where we compare with nothing. We can do a study where we compare with
historical controls, but again, I have mentioned that there are many factors.
So, if you compared with historical controls,
you need to be careful that you match for pre-transplant HBV replication
status.
The indication for transplant, because
whether you have a bunch of fulminant hepatitis patients in a study population
or very few makes a difference. You
need to match for HBV co-infection if you want to compare with historical
controls.
Well, is a study looking at HBIG only
feasible? As I mentioned in our study,
I was actually analyzing our data about two months ago at a time we had
enrolled 212 patients into the data base.
Of these 212 patients -- these are all U.S.
centers, by the way -- 40 percent of the patients were receiving antiviral
therapy at the time they were being evaluated for transplant.
The majority of these patients were put on
antiviral therapy by their local gastroenterologist, before they even came to a
transplant center.
This is one of the problems. We have no controls. Patients come on certain regimens before
they come to our door, and you cannot take the patients off therapy and do
something different.
Clearly, after we have seen a patient and
evaluated a patient, we realize that some of these patients do have very high
activity, high DNA level. We put some
of our patients on antiviral therapy.
At the time of transplant, 65 percent of our
patients are actually receiving antiviral therapy. You can imagine that there is no way that you can do a study of
HBIG alone if two thirds of your patients are already taking antiviral therapy
at the time of transplant.
So, in 2004, when 65 percent of the patients
are receiving antiviral therapy at the time of transplant, what can you do?
Well, if you want to know if HBIG has any
role, you can potentially have a study where you look at antiviral plus HBIG,
compare with historical data on antiviral only.
This, again, is not going to be easy to
analyze, because the historical data would be patients who received lamivudine
only. Patients, when we knew they had
lamivudine only, we weren't able to do anything about it.
In this day and age, we wouldn't. If we knew
that a patient had resistance, we will put them on a second antiviral agent.
So, the data analysis is going to be pretty
complicated. Again, what antiviral will we be using in 2004? Will we be using lamivudine in the study
design, or will we be using adefovir in a study design because it has less
issue of resistance but it might have more issue of renal toxicity?
So, that all complicates matters and, of
course, we don't have adefovir alone as historical data for a control.
I think this is my last slide. I have never been a big fan of PK
studies. I think they are great for
publishing papers, but they are impossible to use clinically.
I can tell you, for those of you who don't
manage these patients, we in transplant programs take care of patients who
travel up to eight hours to come and see us.
So, right after the initial post transplant
period, you cannot get your patient to drive eight hours to come back and see
you on a monthly basis. So, we rely a
lot on long-distance care.
So, trying to get a titer, draw a blood
sample, get a titer, get the result, and then adjust the next dose and, when
HBIG is not something you give subcutaneously or take by mouth, when you have
to liaise with home nursing care, local clinics, it is a nightmare which is
impossible to really implement.
So, it is great for getting information, but
it is impossible in clinical practice, but they have certain roles.
In evaluating a product, I think the most
important thing is really to show quality control. If you say you have X,Y and Z in a bottle, does it really contain
X,Y and Z in a bottle is something else.
When we look at these PK studies, we need to
take into account intra- as well as inter-patient variability. We need to take into account confounding
factors, viral load how long after transplant.
So, when you compare with previous studies,
you don't really look at data two years out versus six months out.
In the immediate post transplant period,
there are all these factors of blood products and drainage, three different
drains draining fluids from the patient's body.
I have given you an overview from my
perspective. I am not really sure that I have actually clarified the issues or
confused you.
This is certainly a very complicated topic,
for which we don't have simple answers, and I am not sure if there is time for
questions. I would be glad to take some
questions, then.
DR. NELSON:
Thank you for a very comprehensive review.
[Applause.]
DR. NELSON:
Are there questions from the committee?
DR. MC GEE:
How big is the study that you are having trouble recruiting on?
DR. LOK:
How big is the study?
DR. MC GEE:
Yes, what is the sample size.
DR. LOK:
Well, we were hoping to get about -- actually, initially we wanted to
get about 150 patients for the high risk group and 50 patients in the low risk
group.
NIDDK has already shut down my low risk
clinical trial because we are too slow in enrollment. The high risk studies are actually on life support, and it is
very hard to do these studies.
So far we have only enrolled 13 patients. We
want to get 150. It has taken us two
years to get 13 patients. Part of the
problem is, with most clinical trials, when you compare one treatment against
another treatment, you provide the study medication.
This is a study in which we don't provide
study medication. So, it is very hard
for people to stick to a protocol, if you don't give them the study
medication. Then they say, well, we
will go back and do whatever we want to do.
So, they don't follow the protocol and they don't enroll the patients.
DR. STRONG:
A question about your monitoring for surface antigen or surface
antigen. What level of sensitivity are
the DNA PCR assays that are being used now?
You mentioned that they weren't standardized, but what is their
sensitivity?
DR. LOK:
The assay that we use is the Roche Amplicor monitor assay. Its sensitivity is less than 200 copies per
ml.
DR. STRONG:
So, there are assays in the works that have more sensitivity than
that. You mentioned that the surface
antigen assays are standardized, but there are also newer assays with better
sensitivity there as well. I am
wondering about standardization for both.
DR. LOK:
That is not true. The surface
antigen assays in general are sort of more uniform than the DNA assays, because
the DNA assays, first of all, in dealing with the NIDDK funded study, we
realized that there are still a lot of centers that don't even use a PCR assay.
They use a branch DNA assay, a hybridization assay.
There you are talking about a very major
difference, two logs versus six logs
With surface antigen, I don't believe that any of these assays will vary
that much.
It is true that with PCR assays, there are
now real time PCR assays. Again, the
problem is, even with the real time PCR assays, that there is really no
standardization, and they are not as widely available in clinical practice.
There are a few commercial diagnostic
reference labs that use real time PCR assays, and they claim a certain level of
sensitivity, but no one has validated their claims. So, you don't really know what you are dealing with.
One of the problems with doing these studies,
for the NIDDK funded study, we had the samples shipped in and we ran it
centrally.
So, at least for the study, we used one
assay. It may not be the best assay,
but we used one assay so we could really figure it out.
In clinical practice, a lot of times we don't
have any choice as to what assay. The insurance companies dictate where the
patients get their blood draw. Therefore, they also dictate what assay the
patient is going to get.
DR. HOOFNAGLE: I think maybe it wasn't clear from your presentation, but I think
a very important occurrence occurred when the U.S. group started studying HBIG,
and they found that higher doses were needed for patients with higher levels of
virus.
Of course, it made sense. We all felt very
stupid that we didn't know that. That
was the reason from Samuel from Europe.
They had a very high rate of recurrence in e
antigen positive patients, and you wondered whether HBIG was working alone.
What McGrory showed was that those patients
had this very rapid disappearance of anti-HBs after infusion. By measuring the disappearance rate, he
showed that you needed more HBIG for people with e antigen and with high levels
of virus.
Of course, it makes all the biological sense,
and they were really the first ones to achieve a 90 percent prevention of
occurrence, even in people with very high levels of virus. He treated some of my patients, and these
patients today, 10 years later, are still on HBIG every month.
So, one of the generations of Anna's study
that she has been a real trouper trying to get this going, was the fact, can we
ever stop HBIG. This is very expensive.
How do we know whether we can stop it or not.
So, as you heard, this was the first use of
the word control in her presentation. There haven't been control trials.
It was an attempt to do a control trial, and
it has been plagued by the fact that we can't provide the HBIG. The patient has to pay for it.
So, there is an enormous resistance to get
into the standardized trial. It is an
attempt to try to figure out whether you can ever stop HBIG.
DR. LIANG:
Thank you for that very comprehensive review. One thing I thought maybe
you can help us with is the question of a vaccine escape mutant. Do you think
that potentially would be a problem in HBIG treatment.
I think that is a sort of important issue,
and maybe you can kind of tell us a little bit about what the risk of immune
escape, or vaccine escape mutants in a patient with HBIG treatment.
DR. LOK:
The s escape mutant appeared to be more of a problem in the HBIG
monotherapy era. Right now, when we are
dealing with combination therapy, by and far, are really patients who either
are non-compliant and they weren't taking the medicine after a while, but more
commonly it is really due to lamivudine resistance.
Unfortunately, what we have observed is that
sometimes transplant centers are not necessarily monitoring HBV DNA level often
enough, and some of these patients were not noted to be lamivudine resistant
prior to transplant.
They were put on combination therapy
initially and, when the patients were receiving a very high dose of HBIG
together with lamivudine, you get away.
After a while, as you titrate down, you find
that the patients develop recurrence.
We haven't actually systematically looked at s escape mutants in the
current studies that we are doing.
Of the patients who have developed
recurrence, I think we have about 130, 140 patients who have been transplanted,
and seven patients have developed recurrence out of 130, which still gives us a
less than 10 percent recurrence rate.
All except one had lamivudine
resistance. The one patient who did not
have lamivudine resistance actually had an extremely high viral load before
transplant and, despite me picking up the phone and calling the investigator,
please put the patient on an antiviral therapy before transplant, the patient
didn't have antiviral therapy while waiting, and developed very rapid
recurrence within two or three months post-transplant. I think that one is really insufficient therapy
post transplant.
DR. LIANG:
As you are aware, some of the lamivudine resistant mutants actually can
confer resistance to HBIG.
I just want to know your perspective in terms
of dealing with mutants that could potentially be double resistant to either
antiviral or HBIG.
DR. LOK:
You are right. Jake is really raising a complex issue. Because of the overlapping, open reading
strain, the polymerase gene and the s gene actually overlap.
When you get a resistance in the polymerase
gene, you might actually change the surface gene as well, and that might
diminish the response to HBIG.
I haven't actually gone and analyzed every
one, because we use a simple screening method to pick up the 1DD mutation.
We haven't actually sequenced all of them and,
because we haven't sequenced them, it is more difficult for us to interpret
what the changes in the s gene are.
DR. CHAMBERLAND: Thank you. I had a couple
of questions about your last few slides. When you talked about the issues
around a study design to assess efficacy of HBIG, you mentioned, in the context
of HBIG monotherapy versus historical controls, some of the issues that would
have to be addressed in terms of trying to make sure that the controls were
comparable to those folks who got monotherapy.
You mentioned some of the really important sort of clinical factors.
I wondered about also, since I think you said
that HBIG monotherapy started in the late 1980s, early 1990s, would there be
other factors that would need to be taken into consideration that have changed
over time, such as perhaps either pre or inter or post operative care or
techniques and things that would also potentially influence outcome and, hence,
contribute to the difficulty of trying to use historical controls that far
back.
DR. LOK:
Certainly, transplant is a field where we have a lot of improvement,
both in terms of anti-rejection therapy as well as the technique of
transplantation itself.
Those can influence survival of the patients,
if you use survival as the end point. However, if you use HBV markers as the
end point, I don't think they would play a major role.
DR. CHAMBERLAND: Then I wanted to ask you, I wasn't sure if I heard you correctly,
in the slide in which you looked at design issues looking at HBIG plus an
antiviral, versus antiviral alone using historical data, did I understand you
to say that those data just are not available.
Are there historical data using antivirals alone?
DR. LOK:
There is very limited data, and those limited data would be lamivudine
only. We do not have data on adefovir
only.
One of the reasons why I caution the group
here is that the historical data on lamivudine only would make lamivudine only
look bad, largely because, when the patients developed resistance, we were not
able to salvage them. So, some of these
patients rapidly go downhill.
So, in this day and age, when we are moving
forward, it depends on which antiviral we use for the combination group.
Now, if you use a different antiviral with
less problems with resistance, let's say you use HBIG plus adefovir, but you
use lamivudine only as your historical control, then you will be comparing
apples and oranges.
DR. NELSON:
You didn't mention patients co-infected with hepatitis C and B. Are these patients just not transplanted?
DR. LOK:
These patients are transplanted but, in most clinical studies, patients
who are co-infected are not included in clinical studies, or they are sort of a
very small group and they tend to be separately analyzed.
There are really tremendous problems with
analyzing those patients. In this day and age, if they are co-infected with B
and C, the problem that we deal with afterwards is really the recurrence of
hepatitis C. That is what causes the
recurrent disease and the recurrent cirrhosis.
So, they tend to be separately analyzed.
DR. KLEIN:
I hope this is not too naive a question, but I appreciate the fact that
we have no controls, but we have a lot of data, and you told us what the
standard of care is.
It seems to me that this is a safe and
effective therapy. It is the standard
of care. The question is how best to
use it and the details. Is that not the
case? I know that we are not being
asked that question.
DR. LOK:
That is the case. The standard of care is to use therapy. We can't have no therapy. The standard of care is to use combination
therapy.
The devil is in the details. The devil is
when to start antivirals. Do we start
antivirals in everyone. Which one do we
use first. Do we use them sequentially or do we pick a different one.
We know that some HBIG is going to be
necessary post transplant. I think very few of us are comfortable enough to say
that, in this day and age, antivirals are so good that you don't need even a
sprinkle of HBIG.
I think many of us are thinking that, in this
day and age, we should be thinking of tailoring to the patient. There are some patients who are going to
need more and some patients who are going to need less.
Even in the high risk patients, there is room
for gradually tapering, either in terms of cutting down on the dose or actually
stopping after the most vulnerable period, the first year or the first two
years, is over. So, the devil is in the details.
DR. HOOFNAGLE: One thing that would solve the problem is if you could immunize
the patient with hepatitis B vaccine, so that they would make their own
anti-HBs.
The difficulty is these people don't respond
to hepatitis B vaccine. The people on lamivudine alone will have no anti-HBs.
They will be s negative and anti-HBs
negative, but they will have low levels of virus in the liver or
something. That would be the perfect
group to immunize, but they usually don't respond to vaccine.
There will be advances here with the use of
new adjuvants and understanding of tol-like receptors and the innate immune
system. Eventually, that might be the
solution.
DR. KLEIN:
Do you think in the transplant setting, that the immunization is going
to work with these patients who were immunosuppressed in the transplant
process?
DR. HOOFNAGLE: They are
immunosuppressed. Most of them are on
two agents. Some you can get off
prednisone.
DR. LOK:
Actually, there are separate attempts with immunizing these patients
with varying success. There is a paper from Spain a couple of years back.
These are very highly selective patients. So,
they picked patients who had extremely low levels of virus prior to transplant.
They waited until the patients were more than
one year post transplant, and they vaccinated them, and they had fairly
successful results.
An Italian group, using the same approach,
giving more doses of vaccine, found that it doesn't work. I think this is an
unresolved issue.
There are people now who say, well, instead
of using the conventional vaccines for prophylaxis in healthy people, we should
use more potent vaccines with perhaps more potent atruvin, maybe higher doses,
maybe intradermal administration versus intramuscular administration.
We have actually approached a couple of
vaccine manufacturers, but no one is interested, because they see that the
market is way too small for them to be worth working with us.
DR. LIANG:
I think one of the problems is also not so much the immune suppressive
agent they are on because, very often, after a year or so, you can really taper
off to a minimal dose and they will do fine.
I think the issue is that most of these
patients are already non-responsive to HBV, because they were chronic infected
prior to transplant.
So, they are basically immune tolerant. So,
it would be very difficult to induce an immune response when they are already
nonresponsive to the antigens. I think
that is really the major problem.
DR. LAAL:
Is HBIG standardized based on antibody titers or neutralizing antibody
titers? Could that be one of the reasons that you have this intra-patient
variation?
DR. LOK:
You mean the labeling of the product?
DR. LAAL:
Well, the product has to be standardized in terms of, either it has so
much titer of the antibody.
Is it neutralizing titers? I mean, all antibodies that are made do not
necessarily neutralize the virus. I am
just curious.
DR. LOK:
I think this is probably a question that is best answered by the
manufacturers.
DR. HOOFNAGLE: There is no neutralizing assay.
It is just an antibody assay using surface antigen as the capture. It is a licensed assay.
DR. NELSON:
One of the manufacturers is going to testify or give a speech in a few
minutes in the open public hearing.
DR. HOOFNAGLE: The HBIG is a polyclonal antibody. It is made from donors with anti-HBs. So, the escape mutants are less a problem because it is
polyclonal.
When groups use monoclonal antibodies, that
is when you get the escape mutants, because you select. It is just a gmish. Here is our expert on anti-HBs.
DR. NU:
I am from CBER, FDA, May Ling Nu(?) speaking. We licensed intramuscular hepatitis B immune globulin.
So, every lot has to meet the
specification. Usually -- we have a
CBER standard, and also WHO currently depends on the manufacturer, because of
the PK studies and so forth, what the manufacturer has to meet, at least one
CBER standard. That is usually around 210 iu, international units, per ml, or
another manufacturer, it depends on the PK study, the specifications for
anti-HBs has to be 312 iu per ml.
I hope I have -- the anti-HBs, it is a
binding assay, it is an ELISA or radioimmuno assay. It is not a neutralizing assay, but they have been
characterized. It is a licensed kit.
DR. LIANG:
How much lot to lot variation do they see?
DR. NU:
What we have now, you have to take into consideration the potency assay
variation and also the dating period.
When we license or release the lot,
throughout the dating period, the lot has to meet that minimum specification,
which is either 210 iu per ml, or 312 iu per ml.
DR. HOOFNAGLE: Do you allow anti-HBC to be present in the HBIG? Are these people who have had natural
infection or are they all immunized?
DR. NU:
They are immunized either by plasma derived or recombinant -- well, the
manufacturer is here. Of course, these are from source plasma donors.
So, the anti-cor is not screened out. Most
likely, anti-cor is there. In fact, it
is there, because it is by plasma pheresis donors.
DR. STRONG:
I just wonder if it is really possible to have an historical control in
this setting, with the changes in immunosuppression and surgical procedures.
For example, we certainly see the dramatic
decrease in the use of blood components in this setting. Is it really possible
to have an historical control?
DR. LOK:
I am not as concerned about the blood product. I think it has some
influence and, like I said, perhaps all the evolution in the transplant field
could affect survival fairly significantly over a 10 year period of time, a 20
year period of time.
If we are measuring HBs antigen, I don't
think that that is going to be a major difference, whether you use cyclosporin
or whether you are using tecrilimers, or whether you are using serolomers. I think if there is a difference, it may be
a very trivial difference.
I think the other issues of comparing data
that we have in this country versus those in Europe, for example, can pose a
major problem.
If you look at any European series of
hepatitis B transplantations, they certainly have a lot more delta infection.
So, they should have a much lower rate of
reinfection compared to the rate that we see here, where delta infection is
extremely uncommon.
Again, if you have a series where you have a
lot of fulminant hepatitis B patients versus a series where you have mostly
cirrhotic patients, the data can be completely skewed.
Those are probably more important in
influencing the results than the changes in immunosuppression and the surgical
technique.
DR. HOOFNAGLE: One more comment, and this is theoretical, about HBIG. The
question that I had asked was, do you use donors who have recovered from
hepatitis B who have been boosted, or do you use people who have just been
vaccinated against hepatitis B?
This may be important because the vaccine is
a recombinant vaccine. So, it is one species of surface antigen, and it is the
small s, not the entire s.
The person who has recovered has been exposed
to quasi-species of hepatitis B and the whole surface antigen. There is the
theoretical issue that hepatitis B immune globulin made from vaccinees may be
somewhat like a monoclonal antibody.
That is theoretical, I know, but that is why
I think it is important to not exclude patients with anti-cor from the donor
pools, because they have the real immunity and the broad spectrum of antibody
reactivity that might be important.
We have no idea about this because there is
no system for neutralizing this. This virus doesn't grow in cell culture and
the animal models are chimpanzees and it is much too difficult to look at true
neutralization on a large scale. That
is a theoretical issue..
DR. LIANG:
I guess just a corollary to that, I guess one of the problems with
including samples from naturally recovered individuals is that there is a small
percentage of them that actually still carry low level virus.
So, I guess you would have to screen out that
unit that contains potentially a low level of virus, despite evidence of
antibodies to both cor and surface.
DR. HOOFNAGLE: That study has been done, and immune globulin made from surface
antigen positive source material is not infectious for hepatitis B. I am not
sure why, but it doesn't seem to be.
The low levels of virus are so low that they
are neutralized by the presence of antibody. So, I wouldn't worry about that
too much, just because of history. It
hasn't been infectious for hepatitis B.
DR. NELSON:
That was an issue in the early days of the hepatitis B vaccine and the
HIV issue at that time, too.
Agenda Item:
Open Public Hearing.
DR. NELSON:
Okay, I would like to open the open public hearing. There are four people who wanted to make a
presentation.
I think it is important that these be fairly
brief. Dr. Smallwood told me seven
minutes. I am supposed to read this statement from the FDA prior to the opening
of the open public hearing.
Both the Food and Drug Administration and the
public believe in a transparent process for information gathering and decision
making.
Therefore, to ensure such transparency at the
open public hearing session of the advisory committee meeting, FDA believes it
is important to understand the context of an individual's presentation.
For this reason, FDA encourages you, the
speaker, at the beginning of your written or oral statement, to advise the
committee of any financial relationship that you might have with any company or
group that is likely to be impacted by the topic.
For example, the financial information may
include the company's or group's payment of your travel, lodging or other
expenses in connection with your attendance.
Likewise, FDA encourages you, at the
beginning of your statement, to advise the committee if you do not have such
financial relationships.
However, if you choose not to address this
issue at the beginning of your statement, it will not preclude you from
speaking. So, that is a very complex
statement that I don't understand.
The first speaker is Dr. John Fung from the
University of Pittsburgh.
STATEMENT OF JOHN FUNG, MD, PhD, UNIVERSITY
OF PITTSBURGH:
DR. FUNG:
Thank you. My name is John Fung.
I am professor of surgery at the University of Pittsburgh. I have been a
liver transplant surgeon for 20 years.
I have been involved, as Dr. Lok mentioned,
in the very beginning, with some of the initial reports on adverse outcomes
associated with hepatitis B and liver transplantation.
Some of the early work with HBIG, then with
fairly poor results, because we did not appreciate the issue of dosing as well
as length of dosing.
We had been involved in some of the early
monoclonal antibody studies in hepatitis B using the OST 577 monoclonal
antibody, and also helped to identify the development of surface antigen
mutants with Dr. McMahon.
The frustration level with hepatitis B
recurrence in liver transplantation, through the 1980s, was the reason that two
attempts at liver transplantation from baboon to human were done in 1992,
because of the thought of the resistance of baboon liver to hepatitis B.
So, the data that Dr. Lok presented really
was something that, in this past decade, the decade of the 1990s, was really
what has turned around liver transplantation, and hepatitis B as an indication
for liver transplantation, as we heard.
I would like to do just for my few minutes is
just to comment on some of the points that were made. I agree entirely. I don't think there is anything that I didn't
agree with Dr. Lok.
We certainly -- I am not here to discuss the
use of hepatitis B in the pre-transplant setting, because I don't really think
there is an indication.
There have been some studies looking at the
use of monoclonal antibodies, some of the OST derivatives, for pre-transplant
hepatitis B, but that is not what I am here to talk about.
There are two different settings for
hepatitis B immune globulin in the post transplant setting. Dr. Lok talked
about using it as prophylaxis for those patients with surface antigen positive.
There is another indication, which is
something that I think is more controversial, which is potential use of this as
a prophylaxis in the use of hepatitis B cor antibody positive donors, in whom
reactivation of the latent hepatitis B from the donor organ has been reported
at approximately 50 percent into naive patients.
Again, this is not an indication that the
panel has been asked to convene on. So,
I would just like to mention a few comments about the use of hepatitis B immune
globulin for surface antigen positive patients.
Just to summarize, this was all mentioned,
again, by Dr. Lok and Dr. Hoofnagle, which is that the DNA positive patients
really represent a high risk patient.
The ones that are DNA negative, as I will
summarize our own practical use and as you already heard, are lower risk.
These patients are higher risk for
re-infection. They do have higher surface antigen titers to start with.
Therefore, they are going to require more hepatitis B immune globulin in the
perioperative period, leading to a shorter half life of the surface antibody and,
because of the use of the antiviral therapies, are more likely to develop the
YMDD mutation, as we have already heard.
So, these considerations for the DNA positive
patients, I think really make us look at this group of patients as the minimum
threshold for therapy.
In other words, since we have a very high
risk group of patients, the treatment should be tailored to provide the best
coverage for them, recognizing that the low risk patients are very easy to
convert.
The principles that we already heard, using
antiviral therapy to suppress viral replication pre-transplantation, to improve
liver function, decrease viral load.
It should be recognized that we do know
patients that are not going to benefit, in other words, those patients with
hepatomas that require early consideration for transplantation may not benefit
from a prolonged course of antiviral therapy.
Nevertheless, we do use it in many of our
patients, as Dr. Lok mentioned, and in post-transplant use to decrease extra
hepatic HBV replication.
It should be recognized that another pool of
hepatitis B exists in an extrahepatic reservoir, and may account for some of
the HBV PCR positivity in the post transplant period, as monocytes and
mononuclear cells are being released into the circulation from the extrahepatic
pool.
HUB use to neutralize circulating HBV is
critical to achieve therapeutic levels in the perioperative period in the
anhepatic and early postoperative periods.
From a practical standpoint, to summarize what
Dr. Lok mentioned, we have used suppressive titering monitor, although we
do try, by ease of administration, use a relatively fixed dosing schedule.
The combination, as she mentioned, really
does maximize protection, and this is currently the state of the art, current
standard of practice in the United States.
We have, in some cases, attempted to go to
monotherapy -- i.e., eliminate HBIG -- but this has really been limited to the
patients that are low risk -- i.e., no replicators or low replicators -- pre-transplantation,
in order to minimize the risk of re-infection.
Just an algorithm that we use, this is a
derivation of our own practice. The DNA
positive patients either will get preoperative, pre-transplant antiviral
therapy if there is enough time to wait, or skip this because of the risk of
YMDD mutations. In the DNA negative
patients, we do not use antiviral therapy.
They move to transplant using a fixed dosing
of hepatitis B immune globulin in the perioperative period, introducing
antiviral therapy as soon as they are orally able to take medication.
Then the DNA positive patients moving to
trough titers, as Tim Pruitt has done at the University of Virginia, trying to
achieve levels of 500 units per liter.
I am sorry, this should be milliunits per milliliter or units per liter,
trying to achieve levels, as I mentioned, for a total duration of 12 to 24
months IV, and then converting them to intramuscular dosing with fairly high
levels of 250 units per liter, with a combination antiviral therapy.
Then, DNA negative patients are lower
dosing. Then, as I mentioned, carefully
selecting those patients that can be taken off HBIG.
Just to summarize, we think that historical
controls can be utilized, but I do recognize what Dr. Chamberland mentioned,
that there have been some practice changes, and you can't compare survival.
Whether the ability to reduce corticosteroid
use in the current era of trocholomus(?), less rejection rates requiring less
steroids, less rejection rates requiring less steroids, we know that steroids
can aggravate HBV replication, is yet to be determined.
I don't know that. I am not entirely sure
that there isn't some role, but I think that historical controls can be used.
I do agree that surface antigen is a
reasonable end point and I think that, overall, it would be unethical and
impractical to expect a trial using HBIG to do anything else but a protocol
including HBIG. Thank you.
DR. NELSON: Thank you, Dr. Fung. Are there any questions from the panel? Okay, the next speaker is Dr. Gary
Horwith with NABI Biopharmaceuticals.
STATEMENT OF GARY HORWITH, MD, NABI
PHARMACEUTICALS.
DR. HORWITH:
While we are waiting for the first slide, let me just address a question
that was asked before regarding the hepatitis B immune globulin.
My name is Gary Horwith. I am the vice president of clinical research
and medical affairs at Nabi Biopharmaceuticals.
We manufacture one of the hepatitis B immune
globulin products. It is approved for
intramuscular use in post-exposure prophylaxis.
Our product is collected from professional
plasma donors. These donors, as has
already been mentioned, may have had natural hepatitis B infection. Others are vaccinated.
Those who are vaccinated at the present time
are vaccinated with a vaccine that was derived from the plasma material from
Merck many years ago.
So, it actually does represent a broader pool
of antigens, as opposed to the monoclonal recombinant vaccines. The immune globulin is all screened for the
presence of virus by NAT.
Dr. Lok went through a very exhaustive
summary of the data that has been generated on the use of hepatitis B immune
globulin.
I only highlight this mostly so that the
advisory committee has it on paper.
This is a summary of various studies that used either low dose hepatitis
B immune globulin or short interval therapy.
You can see that the recurrence was actually fairly high, as has already
been mentioned by Dr. Lok.
When investigators moved to a longer course
of therapy, the recurrence rate decreased substantially.
As Dr. Lok has already mentioned, when the
availability of lamivudine was the trend for monotherapy, the initial experience
indicated that the recurrence rate was actually fairly low.
The early studies, which were shorter term
duration had a lower recurrence rate but, as the experience increased, with
more data, longer duration of follow up, the recurrence rate that was seen
actually tended to increase. I will use this as the basis for the analysis that
I will show you momentarily.
Now, of course, as Dr. Lok also mentioned,
the standard of care is to use combination therapy of an antiviral, primarily
lamivudine, with hepatitis B immune globulin, which has resulted in a
substantial decrease in the recurrence rate.
So, going back to the questions that were
posed by the FDA, I tried to address this in terms of what is actually
necessary in order for the FDA, the advisory committee, that is, to make a
recommendation in terms of what should be used for an approval process for the
hepatitis B immune globulin.
Obviously, we have to have a basis for
efficacy. We have already heard that
monotherapy is no longer possible, due to the current standard of care.
So, efficacy has to be determined either
based upon some historical control information or compared to the combination
use of hepatitis B immune globulin and an antiviral, compared to the data that
is generated from lamivudine alone.
Then secondly, of course, we have to have a very nice safety profile for
the hepatitis B immune globulin.
Our own studies, which were conducted going
back to about 1997 to about 1999, includes a data base of about 153 orthotopic
liver transplant recipients.
Thirty-two of those individuals were new
transplant recipients, and 121 were what we refer to as chronic maintenance
phase patients.
These are individuals who, at the time they
entered the study, receiving the Nabi HP, they were at least three months post
transplantation.
Out of the new transplant patients, we had 32
who were evaluable. One patient was eliminated from the analysis I will show
you because the patient died within 24 hours of transplantation, due to complications
of transplantation.
We have a mean follow up for these
individuals of about 2.7 years, and you can see the range there. Of the 31 patients that are evaluable, there
is a recurrence in two patients, which gives us an efficacy rate of 78.5 percent,
based upon the recurrence rate in patients who received lamivudine monotherapy
being approximately 30 percent.
So, we are using as a basis here that
monotherapy with lamivudine results in 30 percent recurrence over the course of
one year.
That is why the efficacy here turns out to be
78.5 percent. In fact, analyzing that,
that is highly significant versus the monotherapy with lamivudine alone.
We took, in addition to the patients that
were in the expanded access program that I am showing you here, we also
included patients evaluated by Dr. Raleigh(?) Dixon at Mayo Clinic in a
prospective study. I will get to that
study momentarily. We have referred to
that as Nabi 4204.
Combining these patients, we have a mean
follow up of 1.9 years, and the recurrence rate for 60 patients in the combined
data set is three, which gives us an efficacy of 83.3 percent and, again, a
highly statistically significant p value.
Now, among the chronic maintenance phase
patients, there were 121 that were evaluable.
we have an extended follow up for 44 of those patients, which was
actually an additional data collection at the request of the FDA, bearing in
mind that these patients were initially enrolled in studies and evaluated
several years prior to the request to get additional information. We were able to retrieve information on 44.
There is a mean follow up of 3.8 years for
these individuals, and we had three recurrences out of 121 patients, giving us
an efficacy of 96.9 percent, compared to the test of zero efficacy, again, a
significant difference.
Nabi 4204, which I mentioned earlier, was an
open label studied that was conducted by Dr. Dixon. All of these were stage two or three surface antigen positive
liver transplant patients, or patients expected to go on to liver
transplantation within 12 weeks of enrollment.
Thirty patients received at least one dose of
100 milligrams of lamivudine prior to transplantation, but there was no upper
limit as to the number of doses of lamivudine they may have received prior to
transplantation.
In the first part of the study, the
individuals received 11 doses of 11,000 international units per dose. They got
two doses on the day of transplantation, as already mentioned, the first dose
usually being during the anhepatic phase.
Then they received one dose of immune
globulin daily for the next seven days, and then one dose on weeks four and
eight.
The second part of the study, which was
actually designed as a pilot to the study that Dr. Lok described earlier, these
individuals received 5,000 international units of Nabi HB intravenously every
four weeks between weeks 12 and 36.
In that study, there was a recurrence in one
out of 29 evaluable patients, giving an efficacy of 88.9 percent. Three of the 14 individuals, or 79 percent
of them, remained hepatitis e antigen positive.
What we concluded from that study, or what
Dr. Dixon and colleagues -- this was an 11 center study -- that
concomitant administration of lamivudine and Nabi HB was, indeed, safe and well
tolerated.
The adverse event profile that was observed
in the study was qualitatively quite similar to the adverse event profile that
has been seen with immunology globulin in other studies.
In the prospective trials, without regard to
relationship, there were 324 adverse events among 206 patients in the data
base, which constitutes a little over 1,300 infusions.
Eighty one percent of the adverse events were
mild or moderate and were self limited. Among those events with a frequency
greater than two percent, we have back pain, which seems to be quite a common
thread in the administration of immune globulin, no different for the individuals
who received hepatitis B immune globulin.
Nausea was reported in five percent, sepsis
occurred in three percent. This obviously is not related to the immune globulin
per se.
In our post marketing surveillance system,
based upon that, we have an estimate of about 51,000 infusions of 10,000
international units of hepatitis B immune globulin, that have been administered
since the product was approved in 1999 for post-exposure prophylaxis and
intramuscular administration.
In that data base, we have a total of 24
adverse events that have been reported, which is quite similar to the adverse
event profile that has been seen in the clinical trials.
So, in summary, Nabi HB, with or without
lamivudine, was highly effective in preventing the hepatitis B recurrence.
The efficacy is significantly greater than
that seen with lamivudine monotherapy, even assuming a recurrence rate of 30
percent.
The concomitant administration of lamivudine
and immune globulin is quite safe and well tolerated, and the adverse event
profile is really quite similar to the adverse event profile of IgG.
Now, one of the things I wanted to end with
was to address the question in terms of dosing. These are data generated by Dr. Tim Pruitt at the University of
Virginia.
This is quite consistent with what was
previously discussed today and what has been proposed by the data from Dr.
Samuel.
Dr. Pruitt looked at his hepatitis B positive
liver transplant patients over an extended period of time, and just simply
plotted the individuals with regard to their anti-HBs titer, based upon the
administration of the immune globulin.
He was able to determine that, during the
first seven days, the break point is basically at about 500 ius. The break point for those individuals
between days eight and 90 is about 200, 250, thereabouts and, beyond day 90,
the break point appears to be at about 100 ius.
You can see that there is, as was mentioned
previously by Dr. Lok -- actually, I don't have it here, but in another follow
up to this, Dr. Pruitt has looked at those who were e antigen positive, or
replicators and, of course, as Dr. Lok pointed out and Dr. Fung pointed out,
those who are replicators require much more immune globulin than those who are
not.
This is food for thought, if you will, for a
dosing recommendation. The initial
approval of hepatitis B immune globulin in Europe was for much lower doses of
immune globulin.
Recently, the EMEA, which is the advisory
group to the CPMP, the centralized agency for drug recommendations for the
European Union, has come out with a new guideline for use of hepatitis B immune
globulin in liver transplantation.
Their guideline reads as follows: Individuals should receive 10,000
international units on the date of transplantation and perioperatively.
They should receive 2,000 to 10,000
international units through day seven and then, as necessary, to maintain the
anti-HBs level at an adequate level.
That adequate level is defined as 100 to 150
IUs for DNA negative individuals, and greater than 500 ius for those who are
replicators, or DNA positive. Thank
you.
DR. NELSON:
Thank you, Dr. Horwith.
Questions?
DR. HOOFNAGLE: On that last slide, when you say DNA positive or negative, when
do you mean, before transplant DNA positive?
DR. HORWITH:
No, these are after transplantation. These are the individuals who --
the recommendation, I think, is actually based on the DNA or the replicative
status prior to transplantation.
Certainly, if an individual still had
evidence of DNA post transplantation, the recommendation is to consider them as
a replicator, obviously, and go with higher trough levels.
DR. HOOFNAGLE: I actually don't understand what you meant. Do you mean that you wanted to keep a higher
trough level in people who were DNA positive before transplant?
DR. HORWITH:
That is correct.
DR. HOOFNAGLE: The devil is in the detail again. If they are DNA positive,
negative on adefovir, is that DNA negative or is that artificial DNA negative?
DR. HORWITH:
They are not native DNA negatives, if you will, but they have been
converted to a non-replicative status, I suppose, and they are considered a
lower risk.
DR. HOOFNAGLE: Also, what test were they referring to, a PCR based test or the
old test?
DR. HORWITH:
I don't know what was the basis for the EMA recommendation. I don't know
which test they are referring to.
That final test was from the EMEA guidelines,
CPMP guideline, and I don't think there is a description in the guideline as to
which test should be used.
DR. KLEIN:
Is HBIG reimbursed in this country for this indication?
DR. HORWITH:
It is now currently reimbursed, yes.
DR. KLEIN:
So, why can't you do the trials?
Why can't they do the trials if this is being reimbursed? Will they not reimburse if it is under
study?
DR. HORWITH:
Do you not understand medicare?
If you are under medicare, you are not reimbursed for HP. You have to pay for it yourself.
DR. KLEIN:
That was the question you just asked.
DR. HORWITH:
Well, if you have a good insurance company.
DR. NELSON:
Perhaps Dr. Fung can address that.
DR. FUNG:
I think the monthly maintenance is considered as a prescription
benefit. Medicaid does not have
it. While you are in the hospital,
those are covered.
DR. HOOFNAGLE: You have the patient who has been on HBIG for years, gets
switched to medicare and can no longer at that point -- at that point has to
start paying for their HBIG. It is
devastating. Some of them quit, stop.
DR. KLEIN:
Is it likely it would be reimbursed if this were a licensed product?
DR. HORWITH:
It is reimbursed now. Most insurance companies will reimburse the HBIG
because it is a licensed product. It is
licensed, not for this indication, but for other things.
So, most insurance companies, regardless of
what the FDA has or hasn't done, will reimburse you for this. Maybe John Fung can address this.
DR. KLEIN:
:Again, trying to do the studies, if this were licensed for this
indication, would medicare reimburse and then let you look at the details?
DR. FUNG:
On the new drug prescription plan of President Bush --
DR. FUNG:
Anna, maybe you want to comment on it.
My understanding from our reimbursement people is that they do
reimburse.
Medicare does reimburse, but it is not done
because -- this is their formal policy -- they allow the intermediaries to make
their own determination. Our
intermediary allows it to be reimbursed from the medicare. Is that true in Michigan?
DR. LOK:
In general, there is no problem with reimbursement when a patient is in
the hospital. Once the patients are discharged, most insurance still don't have
a problem, but there are instances when this can be a problem, because it is
not a direct, straightforward reimbursement.
You have to go through intermediaries.
During the first initial post-transplant
period, depending on the transplant center, there is also another complicating
factor.
A lot of times insurance companies will pay a
transplant center a lump sum for the transplant. It will cover the transplant admission and for varying durations
post transplants, and that includes almost everything.
So, depending on the contract that you have
with the insurance company, if that lump sum covers a very extended period post
transplant, including medications, including readmissions and all that stuff,
then transplant centers would be in a situation where they would try to cut
back on the use of HBIG, which is an extremely expensive item.
One of the big problems with doing a clinical
trial, when you don't have the manufacturer supplying the product, is that
different transplant programs have different policies, different patients have
different insurance policies. So,
trying to standardize things makes it very difficult.
DR. LINDEN;
Can I just get clarification, though?
When you are talking about these usually are covered, do you mean if the
person's private insurance has a drug plan?
If it is medicare, at the present time, it
would not be covered, which is what Dr. Hoofnagle was saying, because at the present
time, medicare doesn't have a drug plan.
Am I understanding this correctly?
DR. HOOFNAGLE: John Fung pointed out, it varies from place to place.
DR. FUNG:
The demercs in this country have their intermediary determine that. Most of them that I know of will cover all
the inpatient costs for HBIG infusion, and in our intermediary they will cover
the outpatient infusion, or intramuscular injections.
This is the northeast. I am not sure if this is true -- I have
heard throughout the country that it isn't uniform, and I have heard of some
patients who have not been given the post transplant, outpatient coverage for
HBIG.
This is because of the off label use, based
on FDA guidelines, that they are not allowed technically to reimburse for off
label use of a medication.
DR. HOOFNAGLE: Let me also point out that, not only is it being used off label,
but in an inappropriate fashion.
The IM HBIG was being given IV. If you have
ever done this, you know it is extremely difficult. What they would do, they
would put it into a liter of D5W and run it in and give the patients morphine
and so forth, because of the systemic side effect of giving IM HBIG IV.
This was what was standard -- what was done
in the standard. You heard about McGory's data. A lot of that was using IM HBIG given IV.
So, it has been a very difficult field and
the availability of an IV product has been much needed. The Europeans have had it for some time. We
haven't had it in this country.
DR. HORWITH:
Let me just clarify that the original immune globulins were, in fact,
higher protein concentration. They were
about 16.5 percent protein, and they contained preservative.
The Nabi HB as well as the European products
that are approved for intravenous use is a five percent protein and has no
preservative.
DR. NELSON:
I would like to move on, now that we have solved all the drug
reimbursement issues. Dr. Garish Vyas
from the University of California.
STATEMENT OF GARISH VYAS, PhD, UNIVERSITY OF
CALIFORNIA.
DR. VYAS:
Good morning. My name is Garish
Vyas. I am a professor at the
University of California, San Francisco, and I am an investigator or PI of an
alternative approach to immunotherapy in post transplant patients who are
hepatitis B infected.
I have not prepared slides. Gordon Tompkins, who was a professor at
UCSF, gave a two-hour talk, and I don't intend to do that, without slides.
There are two studies that have been done,
one by our group at UCSF, to demonstrate the feasibility of making hepatitis B
immune plasma that costs less than 15 percent of that of HBIG.
Our primary motivation was, how can the cost
be reduced, particularly for patients who do not have resources to pay for
hepatitis B immune globulin.
As a blood banker -- and I am an alumnus of
this blood products advisory committee -- we considered immunizing or giving
booster to people who had been previously immunized with hepatitis B vaccine.
So, we took 100 donors, who were already
vaccinated previously, and tested their antibody titers. Those who had high antibody titers were given
one booster and then, post booster, six weeks later, they were entered into a
plasma pheresis program.
These plasma pheresis units were obtained in
500 to 600 ml, double plasma pheresis, and then aliquotted into subunits of 100
ml.
Each of the donations was standardized for
anti-HBs content by licensed assay, and labeled with the amount of antibody
content in 100 ml of this hepatitis B immune plasma.
This was an investigational new drug, permit
approved by FDA, and the committee on human research at UCSF.
We have shown that it is possible to do this
routinely to prepare such product, and everything that is done in the blood
bank is done, namely, the NAT testing and the antibody screening. These donors are certified to be suitable
for human use, like any fresh frozen plasma donors.
So, to make the long story short, I have
distributed to the committee a recent review that has been published in Clinics
in Liver Diseases, volume 7, 2003, page 537 through 550.
In one page, on 546, we have another
experience at UCSF on preparing hepatitis B immune plasma, and its clinical
trial done as phase I safety in nine patients.
So far, it has been very encouraging.
Dr. Mentha(?), in Geneva is doing -- we are
doing only anti-HBs containing plasma, that is, the donors are anti-cor
negative.
Dr. Mentha in Geneva has done studies with
hepatitis B infected, previously infected patients, who are anti-cor
antibodies, as well as anti-HBS.
As reported, a follow up period of 58 months
to show that 92 percent of the patients remain protected. With this, I would stop and let you ask any
questions that you have about hepatitis B and plasma.
DR. NELSON:
Thank you, Dr. Vyas. Questions?
DR. LINDEN: How many copies of your reprint
are there? It seems the other side of
the table got it and we didn't over here.
DR. VYAS:
My apologies. I looked at the
membership, which was nine or 10, and I brought 10 reprints. I apologize for not having brought more than
10.
DR. NELSON:
We can make copies. We will make sure everybody gets one. Any questions? Thank you. The last
person who was scheduled to speak, Dr. Forrest Dodson, director of
transplantation surgery, at Rush Hospital in Chicago. Dr. Dodson?
Okay, is there anybody else who wanted to
make any statement in the open public hearing?
Okay, so we are only 20 minutes behind. So, we can have a break and we
will reconvene at quarter of 11:00.
[Brief recess.]
Agenda Item:
Open Committee Discussion. FDA
Current Thinking and Questions for the Committee. Committee Discussion and
Recommendations.
DR. NELSON:
Dr. Golding, I wonder if you could restate the questions or tell us
really what you want us to do.
DR. GOLDING:
What I think I would like you to do is tell us how to go forward to
regulate this products. As we have
heard, we have a very complex situation and, because the field has moved quite
rapidly and we are far beyond the stage where hepatitis B immune globulin
products are used as monotherapy, we have a situation where, if these products
are submitted to the FDA, how do we approve them for safety and efficacy.
Even though this is difficult, we feel that
we need to find solutions and we need to find a path forward. I think the main
purpose, to present it to the committee, was to present them with the scope of
the problem, and to try to formulate some questions which would help us move
forward when we deal with these products at the FDA. So, I will go over the questions and see if we can get some
answers.
So, the first question, which I think is
relatively straightforward is, in clinical trials to show efficacy for HBIGIV
treatment, can HBs antigen seronegativity be used as the primary end point for clinical
outcome, indicating prevention of current HBV disease in the transplanted
liver.
DR. NELSON:
Is there discussion on this issue?
Do we need to vote?
DR. SCHREIBER: It seems, since DNA levels are important in terms of deciding
outcome, and also in terms of deciding the groups that get on the therapy with
the outcome of therapy, it would seem that, as opposed to the original write up
where it says a primary outcome, it is now the primary outcome.
I guess I would ask whether DNA measures
should also be considered as an outcome variable in any kind of clinical trial,
despite the fact that we heard that there is not standardization.
In fact, if you are going to do a trial, you
will standardize the measures and, if you are looking at outcomes, you should
be able to get a good measure.
DR. HOOFNAGLE: There are two difficulties. One is these low levels of HBV DNA
that you see in some patients of uncertain clinical significance. So, by itself, it is hard to use that as an
end point.
The people who develop surface antigen
generally will re-develop very high levels of HBV DNA. So, it is unequivocal.
The surface antigen kind of separates the men
from the boys or however you want to put it, as far as the seriousness of the
re-infection. Probably everybody gets
re-infected. What the antivirals and HBIG does is keep it suppressed.
I think you need to use surface antigen as an
end point and, in the current day, it is hard to use more than the surface
antigens, because of the therapies of hepatitis B.
DR. NELSON:
Do you want us to vote on this?
I guess that is the way it works.
Are we ready to vote? Do we just
hand vote?
DR. SMALLWOOD: The procedure for voting is by roll call. I will call your names, and you will answer
yes or no for the first question, which I will read again.
In clinical trials to show efficacy for
HBIGIV treatment, can hepatitis B surface antigen seronegativity be used as the
primary end point for clinical outcome, indicating prevention of recurrent HBV
disease in the transplanted liver. We
are ready to vote. Dr. Allen?
DR. ALLEN:
Yes.
DR. SMALLWOOD: Dr. Davis.
DR. DAVIS:
Yes.
DR. SMALLWOOD: Dr. Doppelt.
DR. DOPPELT:
Yes.
DR. SMALLWOOD: Dr. Klein.
DR. KLEIN:
Yes.
DR. SMALLWOOD: Dr. Laal.
DR. LAAL:
Yes.
DR. SMALLWOOD: Dr. Chamberland.
DR. CHAMBERLAND: Yes.
DR. SMALLWOOD: Dr. Harvath.
DR. HARVATH:
Yes.
DR. SMALLWOOD: Dr. Hoofnagle.
DR. HOOFNAGLE: Yes.
DR. SMALLWOOD: Dr. Liang.
DR. LIANG:
Yes.
DR. SMALLWOOD: Dr. Linden.
DR. LINDEN:
Yes.
DR. SMALLWOOD: Dr. McGee.
DR. MC GEE:
Yes.
DR. SMALLWOOD: Dr. Quirolo.
DR. QUIROLO:
Yes.
DR. SMALLWOOD: Dr. Schreiber.
DR. SCHREIBER: Yes.
DR. SMALLWOOD: Dr. Whittaker.
DR. WHITTAKER: Yes.
DR. SMALLWOOD: Ms. Knowles.
MS. KNOWLES:
Yes.
DR. SMALLWOOD: Dr. Nelson.
DR. NELSON:
Yes.
DR. SMALLWOOD: And our non-voting industry representative, how would you vote?
DR. STRONG:
If I were allowed, I guess I would vote yes.
DR. SMALLWOOD: The voting on question one is unanimous yes, with the non-voting
industry representative agreeing with the yes vote.
DR. NELSON:
Dr. Golding, the second question.
DR. GOLDING:
The second question is a little bit more complicated. Is a single arm study for safety and
efficacy during the maintenance period following orthotopic liver
transplantation sufficient for licensure.
The study would compare either HBIGIV with an
historic control of no treatment for 12 months, or HBIGIV plus lamivudine or
other antiviral for 24 months, with an historic control of lamivudine or
appropriate antiviral alone.
Part of the thinking here, and the reason for
the longer follow up in 2B is the observation as presented by Dr. Lok today,
that the resistance to lamivudine, at least, starts to -- you start to see
breakthrough cases starting at one year and increasing to three years, and that
you would need a longer follow up in order to be able to determine whether
there was an additive or synergistic role of the immune globulin when you had
the combination therapy.
DR. NELSON:
Any discussion about this?
DR. ALLEN:
I think, given all the information that was presented to us as
background materials, as well as the presentations and discussions today, it is
very apparent that the standard of therapy does include HBIG today.
There are still obviously some very important
unresolved questions. There is the
whole question of use of an intramuscular product, or primary use of an
intramuscular product in a different mode of administration, development of new
products and how they would be factored in and so on, a lot of very important
questions.
I guess I would prefer to see, instead of
stating a single arm study, to say that alternative study designs other than a
placebo controlled study, because I am not sure that single arm is the only
study design that would be satisfactory for this.
I will vote yes on this, but I wish it were a
little bit broader without necessarily saying that it had to be a placebo controlled
study.
DR. LIANG:
I guess the question is, is there any particular design that you would
think would be appropriate if you wanted to design another group for
comparison?
DR. ALLEN:
Study design is not really my forte.
I wouldn't want to be the restricting factor on that one. As we heard from the presentation earlier,
you might come up with an absolutely -- not you personally, but the principal
investigator might come up with an absolutely -- wonderful study design and
there would be other limitations such as the inability of patients to come in
or comply with it, as was described today, the travel factors, the factor of
people already being on certain courses of therapy prior to the enrollment in
the trial.
This is a very complex field. As I said, I will vote yes on this, but my
preference would have been to see it slightly broader.
DR. HOOFNAGLE: I agree with the question about the single arm, just maybe non
controlled. You might study two different doses, for instance, or different
regimens.
What I wondered about, what do you mean by
maintenance period? Do you mean a study
in which people are already on an unlicensed product and are switched to the
new product, or do you mean taking people from the time of transplant with a
new product?
DR. GOLDING:
The difficulty is that, when you are doing the perioperative period, a
lot of things are going on.
The actual dosage is usually a lot higher and
there are a lot of concomitant things going on besides the antivirals. There is also the immunosuppression and so
on.
What we thought, that during the maintenance
period, if the trial is done during that period, which is three months or maybe
even six months after the transfer, that you have less variability between
patients and between regimens.
What we have heard is that different centers
are using different dosages at different frequencies in the perioperative
period, but it seems like it is easier -- maybe not completely standard -- but
it is easier to expect that, during a maintenance period, there would be
agreement between the treatment centers in terms of what doses and what
frequency would be used. So, it would
be easier to set up a study during that period rather than to include the
perioperative period.
DR. DOPPELT:
I have a question. I am a little
bit confused. On group A, the HBIGIV, are these patients who would never have
been previously on an antiviral, or they had been but, at the time of
transplant, then you switched them to the HBIGIV only?
DR. GOLDING:
The idea is that these patients would not have been on antivirals. It
would have to have happened at a time when antiviral treatment was not being
used, or in a study where antiviral treatment had not been used.
This is a retrospective study. It is data that was collected some time back
before antivirals became part of the standard of care, so that you could look
at that study and compare that to a time further back when there was no
treatment, no antibody or antiviral treatment.
The numbers are that, prior to any treatment,
in this scenario, you had 70 percent recurrence in the first year and, with
HBIGIV or HBIG monotherapy, you had somewhere in the region of 30 percent
recurrence in the first year.
If you could show that your product had that
kind of effect compared to no treatment control, would that be sufficient for
licensure?
DR. LIANG:
I think Dr. Lok has correctly pointed out, really, at this stage, almost
40 percent of the patients coming to transplant are already on some kind of
antiviral therapy.
I think potentially that is a problem for the
option A, to just expect that we are going to be able to do the study with HBIG
without the patient ever having been on antiviral therapy.
DR. GOLDING:
Yes, I don't think that study is practical, feasible, ethical at this
point in time. I am saying, if data was collected previously when this study
was practical, that could be submitted to the FDA.
Does the committee think that that is
reasonable, that we can go back and say that, even though the standard of care
today is very different, could we go back in time and say, well, that showed at
that particular period of time, that that product, that immune globulin
product, was safe and effective, because it was more effective than no
treatment.
DR. NELSON:
Presumably the measurement of the end point, which we decided in vote
number one would be surface antigen, presumably that has been standard since
the early days of the liver transplant.
Now, whether the same methods were used and
whether it was done at the same time after the transplant was done, I don't
know, but I presume that it is probably comparable.
That is another argument for using surface
antigen rather than DNA, which may have varied quite a bit over time.
I would think that the end points, if we used
what we had voted on for question one, probably would be available in an
historic control that had no treatment other than -- it seems to me that since
now all of the HBIG patients, or certainly the vast majority, are getting
antivirals as well, there is no way we can not use those patients and require,
for licensure, only those that get HBIG.
DR. LIANG:
Are you also trying to answer the question of whether the use of
antivirals should be licensed for prophylaxis for transplant as well? Is that something that you are trying to
address as well, of just the HBIG.
DR. GOLDING:
Our task in the office of blood, we regulate immune globulins, plasma
derived products. The drugs are
regulated in the center for drugs.
My understanding is that these antiviral
drugs, although they are licensed, or lamivudine is licensed, it is not
licensed for the indication of OLT.
So, what we are dealing with is a complex
situation. We are not usually in the business of getting submissions where you
are using two products, neither of which is licensed, and you want to know
whether you have a safe and effective treatment.
The simple way of doing this is to license
each product on its own or its own merit, and then do a combination treatment.
We have gone far beyond that in terms of
standard of care. This is where we are now. We are going to have to deal with
that, and that is why it makes it much more complicated.
DR. LIANG:
I think that, if that is the case, it probably is not going to be
possible to conduct just HBIG alone in a study. I assume that you are going to have to look at historical
studies.
DR. GOLDINg:
Well, we are saying 2A is for retrospective analysis of data, 2B is for
prospective studies, could we conceive of studies where you are doing HBIGIV
plus an antiviral, and compare that again to historical data.
I don't think, from what I am hearing, that
anybody is going to do a study with the antiviral by itself. That is not acceptable.
Again, it would have to be a comparison to
historic controls, the combination therapy compared to the antiviral by itself.
We have seen data, and I am not sure how well
that would stand up to rigorous review, that antiviral studies on their own
have been performed, and there is data out there, but can we now go ahead and
ask a company to do -- or a sponsor to do -- a study that would have combined
therapy, and have to show in that trial that the combined therapy is better
than the antiviral alone.
DR. HOOFNAGLE: Again, we are talking about different things. What I am talking
about is two different types of studies.
One is, you have someone who has been
transplanted in the past and is on HBIG.
You do a study where you switch him to the product that you are
interested in.
In that type of study, all you can really get
is, you get the same levels of antibody.
As far as efficacy, we don't know at that point what the efficacy would
be.
The efficacy studies have to start with the
time of transplantation, as was shown by the Nabi data, where they had the
patients from the Mayo Clinic, the 37 patients or whatever, that were given
their product right up front and followed and shown to have a lot rate of
response.
That is the group from the start, from the
time of transplant forward, to either 12 months or one year, to show
efficacy. The other is just showing
equivalency of reaching antibody levels and side effects.
While that is a little bit helpful, what it
seems to me you need is someone who is started on the new HBIG or the HBIG you
are interested in at the time of transplant, and then show at 12 months that
the rate of re-infection is 10 percent or less or something like that, or the
controls were 30 percent.
DR. GOLDING:
Maybe makes sense to me. If the committee and everybody else agrees, I
think we should strike the word maintenance.
What you are saying is that you want studies from the time of the liver
transplant and throughout.
DR. HOOFNAGLE: Right, because it addresses this issue of what dose do you give
around the transplant period, which is probably the most critical dosing
period.
Thereafter, you know, you have got a stable
situation and the dose may not be as important. So, I think that, as far as
efficacy, you have to start from the transplant.
It seems to me that you can use both of those
historical controls for the patients who don't need an antiviral, who are PCR
negative. They can use HBIG alone. The
real tough group are those that are going to be on both, the Bs.
DR. GOLDING:
Did I catch or misunderstand -- did you say that if you had a patient
today who is HBV DNA negative, who is HBe antigen negative, that you would
think that it is reasonable to put that person on monotherapy during the
transplant? Could you conceive of
having a trial of that design?
DR. HOOFNAGLE: I wouldn't subject HBIG to that situation. That is a situation where you may get away
with antivirals alone, which would be cheaper and easier, like Dr. Lok showed,
in what we call her low replicative phase.
These are people who are not on antivirals,
are on nothing, and they are PCR negative at transplant. Those people can probably get away with
monotherapy using an antiviral. That is
what Anna's study was, but she couldn't enroll it much.
The problem patients are those who are HBV
DNA positive at transplant, or they are HBV DNA negative and on an antiviral
agent already. So, they are being suppressed. You don't know, if you took them
off, but that HBV DNA would come back.
That is the target population where I think
you should aim your efficacy trial. Frankly, the standard of care now includes
an antiviral agent, I think.
DR. NELSON:
I think this comparison with a control would also have to take into
account the prevalence in the control group of the other risk modifiers, such
as delta, cirrhosis, level of HBV, et cetera, et cetera.
Hopefully, those data are available on an
historical control in such a way that it could be comparable. I think probably
they are, but I am not sure.
DR. HOOFNAGLE: I am saying the study A, you are just not going to have any
patients in that group, because the transplant surgeons are not going to be
willing to do that, except for this very special group that probably doesn't
need very much anyway.
DR. GOLDING:
Right, so what I have said is that group is only a group that is viable
based on data that was collected prior to this era, and it is not a viable
design for this point in time, that we passed that point.
DR. LIANG:
So, for B, my understanding is that you were trying to ask us whether we
should endorse a study to look at the option B, the combination.
DR. GOLDING:
Correct, and the historic control there would be the antiviral itself. As was pointed out by Dr. Kenrad, there is
certain data that you would look at in the historical data to make sure that
the two groups were comparable, especially for critical things such as HBV DNA
and the D virus and so on.
DR. LIANG:
So, are any of the pharmaceutical companies making these antivirals
trying to license their antiviral for OLT use at all?
DR. GOLDING:
I don't know about that. We
would have to ask people in CDER. I don't know about that.
DR. LIANG:
I am just saying, if you plan to do the study, perhaps it would be a
good idea to get together with them and see if there is a coordinated
effort. Basically you are trying to
approve or license both drugs, if there is an effort to do that.
DR. GOLDING:
Yes, it is more complicated, but you are right. It is a good point. We should do this together with CDER,
especially if they have sponsors that are wanting to do that.
DR. LIANG:
Rather than come back later and try to address the issue again.
MS. KNOWLES:
I have a question. The question is, in the briefing materials, this
question number two states, is an open label study during the maintenance
period, and then it goes on.
Yet, in the materials we have today it has
been changed to, is a single arm study.
Can you help clarify that for me, please?
DR. GOLDING:
After the discussion I heard, I am beginning to think that our previous
form of it is a better form.
So, thanks for pointing that out. I think we should change it back to either
an open label study, rather than confining it to a single arm study.
DR. NELSON:
Are we ready to vote on this one?
AUDIENCE PARTICIPANT: At the risk of adding complexity here, part
of why this was posed as the maintenance period was also the fact that much of
the retrospective data were only generated for new products in the maintenance
period. In other words, the product was
switched.
I guess there is a question whether we should
even consider approved labeling for maintenance, independent of whether that
same product was used perioperatively.
I just want to be clear here, Jay, I
understood your comment to imply that that would not be appropriate because it
wouldn't have real clinical meaning. It
suggests that we would be striking also the idea of maintenance.
DR. HOOFNAGLE: The studies that do show that you can switch are valuable for
labeling, for instance, because you might want to say that, in the typical
patient who has been on HBIG, you can achieve a titer of 250 with this dosing
every month or something like that.
So, I think those studies are helpful, and
they are probably the preliminary studies that should be done, if a new product
comes along, try switching patients before you embark upon the critical study,
which is starting at the time of transplant.
So, I am not saying they shouldn't be done,
but I am saying that what they tell you is something a little bit different.
AUDIENCE PARTICIPANT: The question is whether one could
extrapolate from a study that showed efficacy in the maintenance phase to
approval of that product for perioperatively and maintenance use.
The argument would be that, if it has the
right pharmacokinetics, and you are going to get there in the next question,
that you would assume that, if it was equally efficacious in maintenance it
would have been a suitable product to be used perioperatively at a comparable
dose.
So, it is a little bit more complicated, and
it is not meaningless to ask the question whether we can validate these
products by studies in the maintenance period.
DR. HOOFNAGLE: Remember what Anna Lok's study now is. She is taking people a
year out on HBIG, surface antigen negative, and taking them off HBIG.
If you switch them to another HBIG, it might
be equivalent to taking them off, and you wouldn't know as far as efficacy.
You would only know that you are achieving
the same antibody titers. I am saying
that you can't really judge efficacy after you are out a year on HBIG and an
antiviral.
DR. GOLDING:
What if you switched a lot earlier than that, if the switch is occurring
at one month or two months or three months, when the incidence of recurrence is
much higher than at a year.
DR. HOOFNAGLE: I think after six months, from the UCSF data you saw, the
majority of people don't have a problem when you take them off and, the few
that did, that may occur anyway. That
is why I think it is difficult to judge completely on maintenance.
Now, when you have two or three products on
the market and someone else comes along with their products, and you have to
judge it the way you do regular immunoglobulin, you don't make them do big
efficacy trials. I think that is a
little bit down the road.
You saw from the Nabi data that studies with
30 or 40 patients are usually adequate to show significance. So, you are not asking them to do enormous
studies.
DR. LIANG:
If I understand correctly, typically, if you have a new product, you
would probably do the maintenance study first just to make sure that it still
works and, if it does, you would move ahead with doing the whole study of doing
the peritransplant area.
I agree with Jay in the sense that you don't
really need a large number to show efficacy.
I think maybe that should be the way to pursue.
DR. EPSTEIN:
What I am hearing is that there is a general sense that studies during
the maintenance period further out from one month may have value and may be
preliminary studies, but that the definitive study in question two shouldn't
say during the maintenance period.
DR. ALLEN:
Do we need the words, during the maintenance period? That doesn't preclude doing that if the
words aren't there. Does the FDA need
those words in there?
DR. GOLDING:
What you were getting from Jay Epstein is that that is an issue, because
some of the studies we are looking at only have treatment during the
maintenance period.
If we are saying that, studies during the
maintenance period are not sufficient for licensure and are only preliminary
studies, and that is what I am hearing from the hearing, then we can change the
sentence to an open arm study for -- is an open label study for safety and
efficacy following OLT sufficient for licensure, and strike out during the
maintenance period.
Unless there is a way of showing -- and it is
obviously complicated -- showing that during the maintenance period you were
really showing efficacy, and that you would have had to have started very early
after the transplant, and you would have to have enough patients to show that
during that period -- because there is a recurrent rate, a low recurrent rate,
that is occurring on antivirals, that is occurring at one year, it is higher at
three years.
I think it is still possible, but very
difficult, to show that even after the perioperative period, your product is
effective.
It is a much more difficult trial to do and
it could involve a lot more patients. I think maybe for clarity and getting
past the part of the question phase, we should change this, if everybody
agrees, to an open label study for safety and efficacy following OLT sufficient
for licensure.
DR. NELSON:
Does everybody agree with that?
DR. LIANG:
Can we vote on separate parts of the same question?
DR. NELSON:
What do you mean separate?
DR. LIANG:
Should we just vote on this question first to strike out the maintenance
period?
DR. NELSON:
Sure. Could we just have a hand vote on this? Does everybody agree with this change?
[Hands of all voting members raised in
agreement.]
DR. NELSON:
So, the change is, a single arm study for safety and efficacy following
OLT sufficient for licensure.
DR. HOOFNAGLE: I think there are two changes.
We are striking a single arm and making it an open label study.
DR. NELSON:
Oh, it is, is an open label study for safety and efficacy following OLT
sufficient for licensure. That is the
new question.
DR. LINDEN:
I think we are eliminating the peritransplant. That disappeared already and we are just keeping that out.
DR. GOLDING:
By not saying the maintenance period it implies, I think, that it is
during the entire period following transplant.
DR. LINDEN:
The wording, excluding the peritransplant period was in there before,
and that has been taken out and we are leaving that out. I was just clarifying.
DR. NELSON:
Okay, do you want to vote on this one, on this revised question?
DR. SMALLWOOD: The revised question reads, is an open label study for safety and
efficacy following OLT sufficient for licensure. Dr. Allen?
DR. ALLEN:
Yes.
DR. SMALLWOOD: Davis?
DR. DAVIS:
Yes.
DR. SMALLWOOD: Dr. Doppelt?
DR. DOPPELT:
Yes.
DR. SMALLWOOD: Dr. Klein?
DR. KLEIN:
Yes.
DR. SMALLWOOD: Dr. Laal?
DR. LAAL:
Yes.
DR. SMALLWOOD: Dr. Chamberland?
DR. CHAMBERLAND: Yes.
DR. SMALLWOOD: Dr. Harvath?
DR. HARVATH:
Yes.
DR. SMALLWOOD: Dr. Hoofnagle?
DR. HOOFNAGLE: Yes.
DR. SMALLWOOD: Dr. Liang?
DR. LIANG:
Yes.
DR. SMALLWOOD: Dr. Linden?
DR. LINDEN: Yes.
DR. SMALLWOOD: Dr. Mc Gee?
DR. MC GEE:
Yes.
DR. SMALLWOOD: Dr. Quirolo?
DR. QUIROLO:
Yes.
DR. SMALLWOOD: Dr. Schreiber?
DR. SCHREIBER: Yes.
DR. SMALLWOOD: Dr. Whittaker?
DR. WHITTAKER: Yes.
DR. SMALLWOOD: Ms. Knowles?
MS. KNOWLES:
Yes.
DR. SMALLWOOD: Dr. Nelson?
DR. NELSON:
Yes.
DR. SMALLWOOD: Dr. Strong, your preference?
DR. STRONG:
Yes.
DR. SMALLWOOD: The results of voting for the modified question two is a
unanimous yes.
DR. GOLDING:
We need to vote on 2A or 2B, I guess.
No?
DR. NELSON:
It is an either or, which is one question rather than two, I think.
DR. HOOFNAGLE: You mean we have to pick one or the other? We can't just say either one would be
okay? I would just like to point out that
A isn't practical, and you are not going to be able to do it. A is retrospective and B is prospective, I
assume. Both of them are retrospective
controls.
DR. EPSTEIN:
The study -- the idea is that the data from the active arm would be
retrospective data, because that is what people did in the past.
So, by accepting A, you are saying we can
analyze data that existed in the past from trials done in the past. No one proposes A as a prospective study
design, but if you reject A, it means that data the companies previously
accrued could not be used.
DR. GOLDING:
So, question three, what pharmacokinetic studies are required for
licensure. This question is in three
parts: To test quality of immune
globulin in normal volunteers, IM or IV, depending upon available comparisons.
Just to say a couple of words about this, our
current thinking for specific immune globulins that are against an infectious
disease or toxin, it is a standard regulatory requirement that we ask the
sponsors to do pharmacokinetic studies in normal individuals to show that the
pharmacokinetic profiles are similar to what we expect from these products.
That gives us added assurance that the
quality of the product is retained in vivo and has normal clearance and half
life in other PK parameters. So, this
is a standard requirement for immune globulin products.
3B is to collect data that can be used to
establish the frequency and level of dosing by studying the target population,
i.e., PK in hepatitis B surface antigen positive OLT recipients, during the
maintenance period following transplant.
Now, the perioperative period, I think we
will all agree, is almost impossible to do any kind of PK study and get any
kind of useful information, because of the variability of the HBV load in a
particular patient.
The idea is that, when you have a patient
following transplantation, there is a low level of virus in the patient.
It cannot be detected by the standard HBs
antigen assay but, because it is there, it would interfere with the regular PK
assessment.
Now, talking to Dr. Lok and Jay Hoofnagle
during the break, it is apparent to me that the most important population to
study is the population where you would expect problems.
So, if you have a subset population where the
HBV DNA was positive at the time of transplant, HBe antigen was positive, or
you have evidence of resistance to the antiviral, those are the most likely
cases that are going to have recurrence.
I think what a PK study in that subset
population would give you is some idea of how to vary the dosing and the
frequency of dosing so that you could ensure that they have the right levels of
the antibody in the serum to protect them from recurrence.
So, this is the thinking behind that kind of
PK study, to try and get data that would help in the labeling that would guide
physicians how to use the product, especially when you have patients that you
think are at high risk of recurrence.
Question 3C is to determine whether trough
levels are useful in titrating the HBIGIV dose in individual patients.
Some studies, they actually use trough levels
to determine dosage in the patients, and the way they titrated the dose was
against a particular trough level.
We saw data from Dr. Lok where the Europeans
were targeting a trough level of 100 IU per ml and then, in some American
studies, they were targeting a level of 500 iu per ml.
The question is, should the studies that are
performed look at trough level, look at the dosages, and see if this is also
useful information that should be in the label and should be provided to
physicians who are looking after these patients.
DR. NELSON:
It seems like A is going to be -- it is pretty much standard procedure
for the FDA and for licensure of a product, and I don't think we would want to
vary that for this particular product.
B and C are the real issues here.
DR. LIANG:
I just have a question for A.
Should that be IM or IV or IM and IV?
Would you want to require them to do PK on either or both?
DR. GOLDING:
It depends on what they want their license for. If they want their license for an IV
administration, then they should do a PK study using the IV route.
If they want to use both routes, we may have
to settle on one route that could be used, but there would have to be some
basis for saying that the IV and the IM routes are equivalent.
One of the things that has happened in the
past is that the product that has already been licensed is only given IM and
then someone comes up with an IV product and we have to show that the IV
product is somehow equivalent to the IM administration.
There could be different combinations here in
terms of which route would be used, but obviously the preferred PK study that
we would ask for would be the one that they would want to have in their label
as the licensed route of administration.
DR. LIANG:
The reason I asked the question, I was just thinking that maybe, during
the early phase peritransplant you would use IV but, in the subsequent follow
up and maintenance, whether that could be switched to IM.
I don't know whether that question has been
posed. If that is the case, I guess you would have to ask for both types of PK
study.
DR. GOLDING:
I think we need to think about that. I don't know if I want to answer
that now. We have some information and
we are looking at this in other studies, whether we can equate IV and IM
without asking for the studies.
The easy answer is to say, yes, you need to
do both IV and IM, but I am not absolutely sure that we can require it.
DR. HOOFNAGLE: I favor both B and C. I think the trough levels can be helpful in
deciding how frequently to give the infusions.
If they come back in a month and the levels
are greater than 1,000, you can spread out to five weeks or six weeks.
Then the patient can eventually reach a level
where they are getting the HBIG infusions every eight weeks or every 10 weeks,
in some situations. I think that data
would be helpful in labeling, helpful to patients to have.
DR. KLEIN:
I just wanted to ask the experts, the data that we saw showed such
variability, both from patient to patient and within the same patient on the
same dose. Do you think that those
kinds of data really are possible to generate?
DR. HOOFNAGLE: You have to remember that is with the old products that were
sometimes given in strange ways. It hasn't been brought up here, but the IM
HBIG products were over-filled.
So, when they gave the full dose, it wasn't necessarily
what it said on the vial. It might have been more. These types of variabilities make it hard to say.
DR. GOLDING:
That is true, that the spec was equal or greater than a certain dose.
DR. KLEIN:
What you are saying is that you don't necessarily think that that was
patient variability, but it may well have been what was in the bottle.
DR. HOOFNAGLE: Remember, the pharmacokinetics change over the first six month as
the virus is completely cleared. So,
then they reach a steady state.
It is at that point, usually after six
months, that the dose can be modified, decreased, usually, and you still
achieve the same levels.
Of course, things may happen to the patient
that makes the thing turn over faster, like an infection or blood letting or
whatever.
DR. NELSON:
How much variation is there on the amount of binding immune globulin in
the preparations that are available?
It seems like a strange requirement that it
be equal or greater than. That is not the way drugs are usually licensed.
DR. LIANG:
I think you base everything on activity. So, you certainly could have a lot more immunoglobulin and have
the same activity as some other lot that has a lower concentration of immunoglobulin. That could certainly affect the PK, although
the unit's activity could be the same.
DR. NELSON
The way I interpreted what Jay said is, the amount of hepatitis B
binding immune globulin varies, not only the total amount of globulin. Isn't that right? Isn't that what you said?
DR. HOOFNAGLE: I think it is just in the preparing from the plasma product, this
pool that they make. They don't know what the titer is going to be until they
get the pool, and then they have to dilute it up with non-immune globulin to
reach a titer that is close.
Then, they don't want to undershoot, so the
FDA allows it to be above a certain amount.
It seems that it is just a biologic that is hard to make exact.
DR. NU:
I just want to address the fill size.
We only set the product specification.
That is, minimally, it should be greater than -- like for one
manufacturer, approximately 210 iu per ml, the other one will be however iu per
ml.
Of course, the fill size has to be greater
than that. As I said earlier, the
potency variation and the assay variation of the potency assay, and also the
PK, the dating period, some are -- it depends on the dating, three years or
more or less. That you have to take
into consideration.
So, we do not say, how much iu per ml
initially. At the time of release we
just specify, minimally you shall have such dose.
DR. NELSON:
Thank you for the clarification.
Are we ready to vote?
DR. QUIROLO:
Can I just ask one question? Is
the maintenance period defined universally?
Is that always the same, a month after the transplant, or does that
vary, depending on the clinician?
DR. GOLDING:
I would ask Dr. Lok to answer that.
DR. QUIROLO:
Do some people call the maintenance period three months, one month?
DR. LOK:
I don't think that there is some standardization, because maintenance
may start at a month on trial.
I don't think anyone would anyone call month
three as maintenance, but somewhere between six and twelve onward would be
called maintenance.
Six to 12 months is still a vulnerable
period. So, I think you might want to
define what maintenance period is.
DR. GOLDING:
In terms of treatment with HBIG, from what you presented, it seemed like
after the first few weeks, there was a monthly dose or four weekly dose starting
very soon after -- even a month after -- the perioperative treatment. You were giving a single dose throughout the
postoperative.
DR. LOK:
You are right. In terms of the
pharmacokinetics, maintenance probably starting from month three is probably
reasonably stable, and that is also substantiated by Tim Pruitt's data, which
shows that, beyond day 90, then there is less variability.
DR. QUIROLO:
Is it a role of this committee to define what maintenance is, or is that
just left up to the study?
DR. NELSON:
I think that might be difficult, because we might have 12 different
opinions, I suppose. I think that the experts in the field probably have more
agreement than disagreement as to what maintenance is, and that may also
include the FDA. I think we can leave
it vague. That is my opinion.
DR. LIANG: I am still a little puzzled about
the C part. I agree with Jay that the trough levels are useful in titrating the
HBIG dose, but what are we voting for here?
Are we mandating that, if there is going to
be a study that they have to measure the trough level accordingly? That could be quite variable. It is really a
clinical judgement. It is the
clinician's purview.
DR.NELSON:
It is, but here we are talking about licensure, not about use. I don't think we are mandating that every
clinician has to use trough levels.
I
think that, for a product -- it is my interpretation, Dr. Golding can correct
me -- that when a product is being licensed for this use, there should be some
data on trough levels.
DR. LIANG: That is what B is going to
provide; right? B is going to provide
that, that the PK study in the surface antigen after OLT, you can see what your
trough is, what your peak levels are, et cetera.
DR. NELSON:
Not necessarily. B doesn't actually
use the word, trough levels.
DR. GOLDING:
The B data would be PK parameters such as c max, area under the curve,
trough levels, elimination times. It
would include trough levels.
The idea of B is to capture information that
would allow you to come up with some general principles regarding the use of
the drug, the dose and the frequency.
The trough levels, as such, is part of that,
you are correct but, as such, it would be useful for physicians to know the
variability of trough level from individual to individual so that, if it was on
the label, they would know, in a particular patient, well, can I just rely on
the dose?
Is there such variability that I need to
actually measure the trough levels in this particular patient because of some
risk factors and, therefore, should I measure them and titrate the dose using
the trough levels.
So, it is more going from a general idea of
what the PK profile looks like in this group to individualizing it to a
patient.
DR. NELSON:
Let's vote on these three together. Anyone who votes no, we will then
ask which of the three or which component of it you disagree with. That might
save a little time.
DR. SMALLWOOD: The committee is now voting on question three, parts A, B and
C. What PK studies are required for
licensure.
A, to test quality of immune globulin in
normal volunteers, IM or IV, depending on available comparitors.
B, to collect data that can be used to
establish the frequency and level of dosing, by studying the target population,
i.e., PK in hepatitis B surface antigen positive OLT recipients during the
maintenance period following transplant.
C, to determine whether trough levels are
useful in titrating the HBIGIV dose in individual patients. Dr. Allen?
DR. ALLEN:
Yes.
DR. SMALLWOOD:
DR. DAVIS:
Yes.
DR. SMALLWOOD: Dr. Doppelt?
DR. DOPPELT:
Yes.
DR. SMALLWOOD: Dr. Klein?
DR. KLEIN:
Yes.
DR. SMALLWOOD: Dr. Laal?
DR. LAAL:
Yes.
DR. SMALLWOOD: Dr. Chamberland.
DR. CHAMBERLAND: Yes.
DR. SMALLWOOD: Dr. Harvath?
DR. HARVATH:
Yes.
DR. SMALLWOOD: Dr. Liang?
DR. LIANG:
Yes.
DR. SMALLWOOD: Dr. Linden?
DR. LINDEN:
Yes.
DR. SMALLWOOD: Dr. McGee?
DR. MC GEE:
Yes.
DR. SMALLWOOD: Dr. Quirolo?
DR. QUIROLO:
Yes.
DR. SMALLWOOD: Dr. Schreiber?
DR. SCHREIBER: Yes.
DR. SMALLWOOD: Dr. Whittaker?
DR. WHITTAKER: Yes.
DR. SMALLWOOD: Ms. Knowles?
MS. KNOWLES:
Yes.
DR. SMALLWOOD: Dr. Nelson?
DR. NELSON:
Yes.
DR. SMALLWOOD: Dr. Strong, your preference?
DR. STRONG:
Yes.
DR. SMALLWOOD: The results of voting on question three in its entirety is a
unanimous yes.
DR. NELSON:
It is amazing, when the questions are so diffuse we all agree on the
answer. The next session is some
committee updates on recent issues and meetings. First is Dr. Kaplan to talk
about current thinking on variances to address the specificity issues of Ortho
HBsAG 3.0 assays.
Agenda Item:
Committee Updates: Current
Thinking on Variances to Address the Specificity Issues of Ortho HBsAg 3.0
Assays.
DR. KAPLAN:
Good morning. I will present the FDA current thinking on variances on
address the specificity issues of Ortho hepatitis B surface antigen 3.0 assays.
So, these assays were approved for licensing
in 2003 by the FDA. There are basically
two assays. One is a screening assay, which is an ELISA-based test, and the
other one is a confirmatory test, a neutralization test, which is also an
ELISA-based assay.
The testing algorithms for these assays is as
follows: The samples are tested using the Ortho EIA System 3.0. This is the ELISA test. If samples are not reactive, the unit is
used and the donor is retained.
However, if the sample is initial reactive,
the index sample is retested in duplicate.
If both duplicates are non-reactive, the unit is used and the donor is
retained, and this we call the rule of three.
However, if one or both duplicates is
reactive, repeat reactive, the index sample is tested with the Ortho 3.0
confirmatory test, which is a neutralization test.
If the neutralization is negative, the donor
is deferred for eight or more weeks, and the sample is retested and, if it is
negative for all the markers, the donor can be reinstated according to the 1997
guidance. If the neutralization is
positive, the donor is deferred indefinitely.
During licensure of this project and the
clinical trials, it was clear that the initial reactive rate was .28 percent,
and that the repeat reactive rate was .0 percent.
However, after licensure and implementation
by blood establishments, a very different scenario was observed. One of the
problems is that there is a big range.
Some centers have more or less what the
product claims. Other centers have a
much, much higher rate. The observed
range was between .2 to 3.5 percent, and this was center to center.
It is not a total rate. It is center to
center. I point out this because you
will see additional data that will give you an idea of the overall rate.
The repeat reactive rate was also much, much
higher, between .1 and .38 percent. An
additional problem, that many of these repeat reactive in great proportion were
confirmed, and those were false positives.
So, on December 23 of last year, Ortho issued
a use and notification alert, which acknowledged the high levels of repeat
reactivity, cross reactivity, of this ELISA test, and also provided some
guidance to reduce that reactivity.
So, what are we doing? What is the action plan? Basically, Ortho Clinical Diagnostics and
the FDA are continue working to resolve the high initial reactive, repeat
reactive and false neutralization tests.
The FDA will grant time-limited variances to
reduce the impact of the ORTHO hepatitis B surface antigen test false positive
rates.
The FDA is proposing two options or two
variances. I will go through the first
one. The samples are tested using the
ORTHO 3.0 screening and confirmatory assays, and I showed you the algorithm
before on a previous slide, showing how that test proceeds.
The neutralization positive index samples are
tested with the genetic systems hepatitis B surface antigen EIA system
screening assay using the shaker method.
If the sample is repeat reactive, the donor
is deferred indefinitely, and it could be confirmed by the GS system to counsel
donors.
However, if this is not reactive, the donor
can be retested at eight or more weeks for surface antigen using the GS EIA
system 3.0. Also, anti-cor antibody and
an anti-hepatitis B surface antibody.
If all the three markers are negative, the
donor can be re-entered. If the surface
antigen on the anti-cor antibodies are repeat reactive, the donor is deferred
indefinitely.
If only the surface antibody is positive, the
donor can be tested with a single unit investigation of hepatitis B NAT which,
if it is not reactive, the donor can be reentered. However, if it is reactive, the donor has to be deferred
indefinitely.
I will walk you through the second option now
and make a little comment that it is -- the second option is simpler, and it
deals more with the problem at the screening level, which is different from the
option one, which deals with the problem at the reentry level.
So, according to the option two, the samples
are tested with the ORTHO surface EIA system 3.0. If they are not reactive so that the unit is used, the donor
retained. If they are initial reactive,
the index samples are tested in duplicate now with the GS system, not with the
ORTHO, using the shaker methods.
If both duplicates are nonreactive, the unit
is used and retained. Here is again the rule of three. If one or both
duplicates is reactive, it is tested by a confirmatory test assay, the
neutralization assay, using the GS system.
If the neutralization is negative, so the
donor is reinstated via the 1997 guidance.
If the neutralization is positive, the donor is deferred indefinitely.
So, this is as of yesterday. Two blood establishments requested the
variances and the FDA granted the requested variances. Today there is a new variance that was
logged into document control. So, we
have a third request.
DR. NELSON:
Any questions?
DR. STRONG:
At this stage, only the GS assay is accepted. If another manufacturer comes along with an equally sensitive test
that is licensed, will that be also accepted?
DR. KAPLAN:
I think we need to see what they come with, which level of
sensitivity. This is more sensitive
than the ORTHO. That is the reason why
it is recommending this, the GS.
DR. NELSON:
Steve, did you have a question?
DR. KLEINMAN: Dr. Steve Kleinman. One
question about the provision in the algorithm for needing to do anti-HBs as
part of requalifying the donor. Can you
give us some rationale for why that is necessary?
I bring this up because we could have donors
who received hepatitis B vax. I know there is a way to get the anti-HBs
positive donor back in by doing the investigational NAT, but I question why it
should even be part of the algorithm.
DR. KAPLAN:
It has to have a third marker, because you are outruling a positive
test. The whole ORTHO screening and
confirming test has to be outruled. So, we wanted to include a third marker.
DR. KLEINMAN: I understand that, but if you can't duplicate the surface antigen
on the same unit, and you can't duplicate anti-cor which, as far as I know, is
a marker that should be present in recent infection or in HBV infection in
general, and chronic infection, why do you need that third marker to reassure
you, given the fact that you may have donors who had received vaccine, and you
now have a confounder.
I guess I don't know why the anti-HBs is
necessary to ensure that the donor is safe, since you are doing a repeat surface
antigen and an anti-cor.
I understand you want more assurance, but I
don't understand the scientific rationale for needing the more insurance.
DR. KAPLAN:
We wanted to be at the very safe side of the equation.
DR. EPSTEIN:
I think the answer to the question is that we know that there is a small
percent of infections that have a positive anti-HBs and negative anti-cor. It is a very small percent, but it exists.
DR. KLEINMAN: And we think those people could be infectious?
DR. EPSTEIN:
We also know that there are infectious people who have negative HBsAg,
yes. They are also a small percent, but
they also exist.
So, what we are trying to figure out is, we
want to rule out all the potentially infectious people, but then we want to
readmit the people who probably only got vaccinated.
DR. KLEINMAN: Would you include a history of vaccination in that? Let's say a person had a history of having
received hepatitis B vaccine and tested positive. Would that be in the
algorithm, too, or not?
DR. EPSTEIN:
We debated that, but the general feeling was that the test is better
than the history, because someone could have been vaccinated and they actually
did have antecedent hepatitis B.
There are many scenarios in which people are
not prescreened for antibody before they are vaccinated. If they are thought to be at risk, they are
vaccinated. They may have already
actually had hepatitis B.
We thought that testing for negative single
unit DNA in the presence of anti-HBs is a better indicator that they were a
vaccinee than their history.
DR. KLEINMAN: Jay, I want to push your explanation a little bit. Obviously, we
don't do anti-HBs for all blood donors.
So, we are not worried about anti-HBs positive donors, having to remove
them all from the donor pool.
So, why are we worried in this case, where we
are only -- we are basically hypothesizing that someone would have to have had
true surface antigen only eight weeks prior, and their anti-HBs would have to
be the result of a seroconversion in that eight week period, with no anti-cor,
in the face of an assay that we know gives false positive results.
I don't see -- the fact that there are some
people who are hepatitis B infected, who only have anti-HBs, it is true, but I
don't see why this population has anything to do with that more general
finding.
DR. EPSTEIN:
I think part of the reason is there are sins of omission and sins of
commission. If you have deferred a donor and you are reentering a donor, you
want to be very, very sure that you are reentering an uninfected donor.
That is why the current reentry algorithm
does require anti-HBs screening, even though the risk of -- even though the
likelihood of finding an infectious donor based on the anti-HBs is low.
The greater risk is reentering an infectious
donor, who you have already once deferred.
So, part of the idea was to maintain consistency with the existing
reentry algorithm, to avoid a reentry error.
So, if you will, the answer is that we have a
higher standard when we reenter a donor than when we first screen one, because
we don't want to make the error of reentering an infectious donor that was once
deferred.
DR. NELSON:
There were three people who wanted to make a statement in regard to
this. First is Dr. Brian Snyder from
ORTHO Diagnostics. These should be brief, like five minutes.
STATEMENT OF BRIAN SNYDER, PhD,
ORTHO-CLINICAL DIAGNOSTICS.
DR. SNYDER:
I am Brian Snyder. I am an employee of Ortho-Clinical Diagnostics, the
manufacturer of the system 3.0 assay.
My organization is responsible for
investigations of the field performance of our products and, based on the
previous talk, I just wanted to give you an update on our investigation of our
product performance.
As was stated, we have had high reactive
rates since the product launch of last year.
To give you a perspective, our product claims, as was stated from the
10,849 volunteer blood donors, was .28 initial reactive, .05 repeat reactive.
Our observed data -- this is averaging over
all sites -- for greater than 4.5 million field samples through February of
this year, was 1.19 percent initial reactive, and .19 percent repeat
reactive. So, that represents about
9,000 repeat reactives in that time frame.
As was stated, our repeat reactives do vary
higher and lower at each site, although generally, even at our best sites, they
are higher than our label claims.
A high proportion of the repeat reactors do
not confirm. Also, the distribution of
optical density values that we get for our samples is not normal, in the sense
that we have a tail down near the bottom end of our OD.
Probably the most frustrating thing is that
many of the repeat reactive samples come from long-term healthy donors.
We have worked very closely with the FDA to
provide potential short-term mitigations. As was stated, we sent a customer
letter in December of last year.
Among those recommendations were limiting
substrate use to less than two hours. It is labeled for eight-hour use.
We proposed increased frequency and enhanced
maintenance for automated equipment, the ORTHO sonic(?) processor.
We reinforced sample handing and reagent
preparation procedures. If available, we suggested that if sites did get lower
reactive rates for semi-automated equipment, they should use it.
Lastly, we altered the stringency of the
confirmatory algorithm to reduce false confirmations due to the natural
statistical variation of the neutralization assay.
At the same time, we looked at our own
internal processes and raw materials for improvement. The bottom line is that these recommendations, in total, were
largely ineffective in reducing the reactive rates significantly, only
producing minor improvements.
We have completed now our investigation into
the root cause of those high reactive rates. The first thing to be stated is
that this system 3 assay was to replace a system 2 assay, and we have confirmed
that the risk of false negatives with this assay is significantly improved over
our system 2 assay, both with respect to the detection of confirmed clinically
positive samples, and analytical detection of AD and AY subtypes.
However, a high proportion of the donor
samples do show false reactivity, indicating a specificity issue with the
assay.
Right now, our investigation is focused on
specific limitations to the design and specification of our concentrate and
conjugate dilutant as the primary source of that poor specificity. Here, the conjugate is the conjugation
between the antibody and our detection enzyme horseradish peroxidase.
So, based on our findings, we believe that
the system 3 assay does exhibit a specificity issue leading to the higher than
expected false reactive rates, and reactive rates that are not associated with
the presence of surface antigen.
We support the concept of a variance protocol
for donor reentry for donors linked to this false reactivity. We will continue to work with the FDA and
CBER to provide both long and short term improvements to the performance
characteristics of the assay we provide.
DR. NELSON:
Thank you, Dr. Snyder. Any comments, questions? Next is Dr. Susan Stramer, American Red
Cross.
STATEMENT OF DR. SUSAN STRAMER, AMERICAN RED
CROSS.
DR. STRAMER:
I have one slide, a new record.
Hopefully you can see the numbers.
We converted to ORTHO System 3 using the new automated method for
testing. Those two changes occurred
simultaneously.
So, we converted from ORTHO system 2 to ORTHO
system 3, including their new automation, for which clinical trials had not
been done.
The clinical trials for the product had been
done on the manual mode, but the system launched on the automated mode. So, we had two variables in place.
We began screening, as I said, on August 18
and, since that time, to February 13, when we began conversion to the Abbott
test, we screened 3.58 million donations.
We had over 8,500 repeat reactives and, as
shown by Dr. Kaplan, we had a range by lot, which we see as the greatest
variable with the test, is lot to lot variability.
By lot the rates varied from .13 to .30
percent repeat reactive rate. I
neglected to mention, our initial reactive rates went anywhere from .38 percent
to 2.27 percent.
As shown by Dr. Kaplan, following the
generation of a repeat reactive result, which we had a mean of .24 percent
which, going from System 2, was a .05 percent, so we saw a significant increase
when we converted.
What was particularly disturbing, then, was
the neutralization results. Where we
are used to seeing over 80 or 85 percent of the samples neutralized, in this
case, with the use of the test, only 17.7 percent neutralized, leaving the vast
majority of the samples non-neutralized.
I just want to go through the stars here,
before I get too far. This first star
here, which is written in the tiny print, but I will read, we have been
converting to Abbott, which was actually completed on the 9th of March.
So, we had a one-month conversion and, during
that time, our repeat reactive rates dropped back to .02 percent, which is
historically where we used to run on the Abbott product.
Of those samples tested by neutralization,
rather than having 17 percent neutralized, we are back to the run rate of 85
percent neutralized, as we would expect.
Then, if you divide the donors into anti-COR
reactivity, indicating that, if someone is HBV invested, they should also be
anti-cor reactive, unless they are recently infected, what we see here is only
about 60 percent of those neutralized are repeat reactive.
What our historic rate for this number is,
rather than 57 percent, is a rate of over 96 percent. So, there is another indication that we were seeing false
positive neutralizations.
These samples, the vast majority, at 97
percent, were also repeat reactive on the genetics system shaker method.
Going on to those that were non-cor reactive,
here we had three quarters of these samples that didn't exhibit cor reactivity,
and were neutralized positive, that did not demonstrate reactive on a second
licensed HBSAG test with greater sensitivity.
So, these are the donors, about 500 of them, that we will reenter the
variance as outlined by Dr. Kaplan.
Here you see the pool of non-neutralized
samples. These will be able to reenter
based on the guidance document of December 1987.
There certainly are, when you drill down
through those donors that become eligible, we have a pool of close to 6,500
donors that we have to reenter by one method, or reinstate by one method, and
then about 500 donors that we have to reinstate by another method.
Even though, during the time that we were
using the ORTHO product, we followed all the instructions provided by the
manufacturer, we were observed by the manufacturer, and we put in all the
permutations that they outlined -- you know, standing on your head, whistling
Dixie -- and we could not get the test to work.
As we saw the overriding issues with lot to
lot variability, we felt that the only course of action was to switch vendors,
which did fix that problem. Thank you.
DR. NELSON:
These results were all done on the initial sample, or was the genetics
systems done on a second sample from the same patient?
DR. STRAMER:
This is the index, yes. It is
part of the reentry algorithm, when we bring the donor in for follow up, is to
repeat this whole litany of tests.
I should say, we will reenter by option
one. We didn't use option two, and
Sally will probably reinforce this but, in an operational setting, with
qualified and validated software, there is no option to take an initial
reactive from one sample and reflex it onto the other test. The software requires you to complete the
algorithm.
DR. NELSON:
Thank you. Questions? Okay, Dr. Sally Caglioli from Blood
Systems.
DR. CAGLIOLI: Thank you. Web Systems
Laboratory sent the implementation of this test in late July of 2003. We have tested about 1.5 million
donations. We have seen the same thing
that Susan just reported.
We have an initial reactive rate depending on
lot of anywhere from .6 percent to 1.1 percent. We have seen a lot range of .13 percent to 1.3.
The repeat reactive rate is variable as
well. We have seen lots that react as
low as .06 percent, and then up to .19 percent.
The disturbing part here, again, is that, of
these repeat reactives, of which we have seen about 1,800, 62 percent of these
were non-neutralized.
Again, these donors can be reentered via the
curtain guidelines, but obviously this is a process that we would prefer not to
have to go through.
Of the repeat reactives, only 33 percent were
neutralized. The disturbing part here
is that, of these, about 26 percent were anti-cor negative, indicating most
likely false positive neutralizations.
We are in the process of implementing the
genetic system shaker method in order to do reinstatement. Unfortunately, we had also implemented all
the things that the vendor had suggested that we do. They are on the next
slide.
They were summarized previously, but they are
things like holding samples, performing weekly cleaning daily, and various
numerous other things, holding substrate for a couple of hours.
We have done everything. My staff is
threatening to get chicken bones to shake over the instruments at this point.
We are currently in a lot -- we thought we
saw some improvement with one lot. We
are currently in a lot that reacts with a repeat reactive rate of .11 percent,
which is three times higher than any of the tests we have used in the past.
So, unfortunately, we are not in a place
where we can convert to the Abbott test because we do not have that technology
in our lab. So, we are continuing to
work with ORTHO. We do encourage the
FDA to approve the method for reentering our donors.
DR. NELSON:
Questions?
DR. EPSTEIN:
Since you are still using the ORTHO test, can you comment on whether the
percent that are neutralized anti-cor negative has now declined? There was a modification the neutralization
test.
DR. CAGLIOLI: Correct, and we have been using that calculation method for about
a month. Unfortunately, because there
is such variation from lot to lot with the screening method, we have only seen
about a two percent decrease.
MS. FORD:
Kendra Ford, vice president of operations at the Oklahoma Blood
Institute. Ditto, ditto, ditto. We are one of the two variances, I believe,
that were approved, and I brought a copy of it.
Our situation is that our variance that we
requested -- and we appreciate very much the quick turn around time from FDA --
while at the time I was thinking about this, I didn't want to bring in another
manufacturer and thought that we were going to be able to get through this,
planned on shipping out our samples.
Currently, we have 100-plus donors that are
in limbo that are very healthy donors and cor negative and same old story.
What I didn't realize was, at the time I was
doing this that, so far, as of yesterday morning, I can't find a U.S.
laboratory that has a genetic system shaker 3.0 approved form of testing. So, we are in a real pickle.
I just wanted to make everyone aware of that
and, if there is a lab available, this would be a time that I would like to be
proven wrong but, so far, our variance hasn't done anything for us.
DR. STRAMER:
I just wanted to mention for Kenrad, for our samples we sent them to the
manufacturer for testing.
I am not sure they are in a position to want
to test the entire nation's blood supply in their reference lab, but at least
for the purposes of reentry --
DR. NELSON:
The next committee update is a summary of the meeting of the Public
Health Service Advisory Committee on Blood Safety and Availability, Dr. Jerry
Holmberg.
Agenda Item:
Summary of Meeting of PHS Advisory Committee on Blood Safety
Availability.
DR. HOLMBERG: I am going to give you an update on our committee meeting that
took place on the 28th and 29th of January.
Just as this committee had problems back in
September with the weather, we also faced weather challenges in January, but we
succeeded to have our meeting.
The topic that we looked at was the role of
government in the national blood supply, whole blood and plasma, plasma
fraction, both in daily medical/surgical use and local/national disaster.
If you would like to look at the transcripts
and also the slide presentations, they are listed on our web sites. It is under past meetings January 2004.
The areas of discussion were national blood
policy of 1974. We felt that after 30
years it was time for us to go back and take a look at the national blood
policy.
Also, national blood programs in developed
countries. An overview was given by Dr.
McCullough. Also, Canada shared with us
their experience, Israel with Dr. Shinar, and the United Kingdom with Mr. Gorham.
We also looked at the national blood reserve
as proposed by the interorganizational task force from the AABB.
Some key elements of the 1974 national blood
policy were to eliminate paid donors, to collect data on blood banking, encourage
regionalization and resource sharing, account publicly for charges, and support
professional training and basic/applied research.
The outcome of that is that the committee
reviewed the policy and concurred that the goals of the policy were adequate,
and that the goals of supply, quality, accessibility and efficiency remain
applicable today.
As an overview of the national blood programs
developed in other countries, I said Dr. McCullough presented an overview of 18
developed countries.
These were ideal national programs. These
countries collected 42 to 59.6 units per 1,000 population, as compared to the
United States, which is 53.6.
Most of these followed a national blood
program fostered by the World Health Organization and also the European Union,
which I must add, is totally different than in our country, in which we have a
pluralistic approach to our blood supply.
In looking at the Canadians, the Canadian
Blood Service was founded in 1998. This
was after the Creaver report, and is fully funded by the provinces including,
what we found very interesting, was a contingency fund to support necessary
advances in their blood supply, additional testing, new testing as it was
added.
Since 1998, annual donations per donor have
increased from 1.6 to over 2.1, but only 3.6 percent of the eligible donors
donate each year, but that is up from 3.0 percent.
At the Magan David Adom Blood Service in
Israel, they collect 45-50 red cell units per thousand population annually,
which provides about a two day blood supply.
Their supply is centers supplies, which are
located in two sites, and most of the hospitals receive daily shipments and the
hospitals maintain a three to five day blood supply.
What was very interesting, with the talk
about Israel, was that 6,000 casualties per year, and about 1,300
multi-casualty events, with 800 deaths.
So, here was a country that dealt with disaster on a daily basis.
The National Blood Service of the United
Kingdom was transformed in 1995 into a national and nationalized program.
It serves England, Scotland, Wales and
Northern Ireland, and these are all an integral part of the national health
service.
They ensure centrally set fees paid by the
hospitals for products or services, and services support necessary costs.
They also do a centralized inventory
management, and also a national data collection, which allows for accurate
planning and forecasting.
This led the committee to a discussion on the
national blood reserve. The
Interorganizational Task Force on Domestic Disasters and Acts of Terrorism
prepared plans for a national blood reserve, to respond to the sudden and
unpredictable civilian or military needs from loss of donor donations or
increased use.
The proposal that was coming from the
interorganizational task force was that it would be a combination of a
government and private sector reserve.
Two thousand units would be controlled by the
government, held by the government through the Department of Defense, and 8,000
units would be controlled by the interorganizational task force, held in
regional blood centers.
This is sort of an overview of what the
Interorganizational Task Force Proposed.
There would be a capability of immediate support through the 2,000 units
that would be held at the Department of Defense Armed Service Whole Blood
Processing Laboratory.
An immediate support would be blood that
would be coming from the regional blood centers, 8,000 units, and then
sustained support would be information to get donors in to re-supply the
inventory.
Some of the characteristics of the reserve,
as it is proposed by the Interorganizational Task Force, is that blood would be
shipped to the ASWBPL to be held for two weeks, and then it would be sold to
the hospitals in the blood regions.
It would be collected by designated blood
centers, held for two weeks, and then sold to other regional blood centers as
needed.
Then, also, information and data sharing
would be very critical. The goal would
be to maintain a five to seven day blood supply across the nation.
So, what the Interorganizational Task Force
was recommending was that we would have a source of supply from the regional
blood centers that would feed into either two sources -- the government through
the armed services whole blood processing lab, and the private sector,
basically, eight regional blood centers that would hold 1,000 units each. At the end of two weeks, these would be
rotated out and sent on to different facilities.
Some of the characteristics of this reserve
would be a public private partnership, real units on the shelf. It would be
secure, and it would have access to distribution.
Some of the operational, a federal depot
would be the Armed Services Whole Blood, and then designated regional blood
centers under contract to the government.
The blood would rotate through the depots and
centers, and then be available as reserves and, after two weeks, they would be
distributed to help with the blood inventory across the nation.
As I said, the recommendations from the
Interorganizational Task Force were recommendations to the committee, and the
committee made recommendations to take steps to increase the national daily
available inventory to five to seven days.
They also recommended to the assistant
secretary for health that the department fully fund the Department of Health
and Human Services' Blood Action Plan in the area of private and government
monitoring, and increase the blood supply.
I highlighted a word that was emphasized by
the committee. So, that is my addition
to the commission's wording, but the committee recommended that the department
address funding needs at all levels of the blood system to support product
safety, quality, availability and access, through targeting of additive
resources and appropriate reform of the CMS reimbursement system for blood and
blood products, including plasma-derived therapeutics and their recombinant
analogs.
Also, the committee recommended to the
department that they establish a National Blood Reserve -- consistent with the
committee's recommendation of January 2002 -- by increasing daily collections
through an enhanced program to expand and sustain volunteer donations.
The committee endorses the elements of the
National Blood Reserve as developed by the AABB Interorganizational Task Force.
These recommendations have gone forward to
the Assistant Secretary for Health, and we are currently looking at these
recommendations with an action plan.
Our next meeting will be April 7 and 8, 2004
and, contrary to what the Federal Register said yesterday, there was a mistake
in that, and I would like to publicly make a correction.
It had plasma products, and it should have
been platelet products, but the topic is the impact and assessment of methods
to reduce the risk of bacterial contamination of platelet products.
So, we are looking forward to an exciting
meeting to discuss some of these issues.
Unfortunately, that is right at the time of Passover and Good Friday is
the next day. So, I apologize to the
inconvenience that this will place on certain people. Any questions?
DR. ALLEN:
I assume, because it wasn't in the hand out, that the committee really
did not address the issue either of increasing the supply of frozen red cells
or use of artificial products under certain circumstances.
DR. HOLMBERG: Let me first address the frozen red cells. The Interorganizational Task Force looked at
the possibility of having a frozen reserve.
They felt that it was, at this point in time, not feasible to do so.
Now, one of the advantages, though, if the
department goes forward with this government capability, is that we do have
frozen blood, or the military does have frozen blood, at these two depots that
we are talking about.
The general theme was not to get into the
frozen blood, primarily because, in an emergency situation, you have to get
that blood out the door immediately, within four to six hours. Frozen blood, the committee felt, was more
of a back fill.
The other question that you had was in regard
to the blood substitutes. The committee
really didn't address that, because that is not a licensed product.
DR. NELSON:
Thank you, Dr. Holmberg. Next is a report on the TSE, transmissible
spongiform encephalopathies, advisory committee meeting, by David Asher.
Agenda Item:
Summary of Meeting of Transmissible Spongiform Encephalopathies Advisory
Committee Meeting.
DR. ASHER:
Thank you, Dr. Nelson. We are running almost 40 minutes late. So, I am
going to try to rush through some of these.
The fifteenth meeting of the TSE advisory
committee was convened on the 12th and 13th of February, to address the
implications for the FDA of two recent TSE-related events, both in December,
one the recognition of a presumptive transmission of variant CJD by transfused
red blood cells in the United Kingdom.
The second, diagnosis of BSE, bovine
spongiform encephalopathy, in a Canadian born U.S. dairy cow on December 23.
The committee was asked to discuss whether
additional risk reducing actions are needed, likely to prove effective, or
feasible for FDA-regulated medical products, specifically, human blood
components or other biological products made with human blood or tissues, and
medical products containing or manufactured with bovine-derived materials.
There is very little doubt now that variant
CJD is a human infection with the agent causing mad cow disease. Most cases have been considered to be food
borne.
There are 156 cases reported to date. Of those, all but seven in life long, or
long-term residents of the United Kingdom.
Of three people who are presumed to have been
infected in the United Kingdom and left, it is possible to estimate incubation
periods somewhere between five years and 21 years, which would not be unusual
for spongiform encephalopathy.
The good news is that, in the United Kingdom,
the epidemic seems to have peaked. New
cases peaked in 1999, and annual deaths peaked in the year 2000.
So, the maximum number of estimated cases in
the outbreak has dropped from a possible excess of 13 million down to something
under 500.
Of course, we haven't seen people, except
with one genotype, come down, and we don't know whether there will be a second
wave.
As many of you know, over the years,
epidemiological studies attempting to investigate the hypothesis that
conventional forms, other forms of Creutzfeldt Jakob disease are spread by
blood, have all been negative.
However, going back to the mid-1980s, a
number of animal studies have found evidence of infectivity in the blood, first
of experimentally infected animals, and later of naturally infected animals.
The most recent report was presented to the
meeting, blood of the chimpanzee infected with familial spongiform
encephalopathy, with features of both the Gerrisman Stroisler Schankman(?)
syndrome and familiar Creutzfeldt-Jakob disease, had transmitted infection to a
squirrel monkey, as assayed with separated leukocytes.
The most convincing study, epidemiological
study, has been one done by the American Red Cross with the CDC and the
National Blood Data Resource Center, data from 1959 through 2002.
One hundred sixteen recipients of blood
components from donors who were later found to have Creutzfeldt-Jakob disease
have survived more than five years, and none of those have had
Creutzfeldt-Jakob disease.
Because of differences in clinical
presentation and pathology of variant Creutzfeldt-Jakob disease and other TSEs,
and because the disease has been recognized so recently -- the first case just
had onset in 1994 -- the uncertainty, the uncertainty regarding this disease
was much greater than that for conventional forms of Creutzfeldt-Jakob disease.
So, it was felt, both by UK authorities and
by the United States, that precautions were needed to reduce opportunities of
exposure to blood from donors who might be incubating Creutzfeldt-Jakob
disease.
Of course, the theoretical possibility of
transmitting Creutzfeldt-Jakob disease by blood was recognized by the FDA as
early as 1987, based on concern with animal studies.
Very different results were obtained by a
joint study presented by Robert Will, the head of the study, by the UK
Creutzfeldt-Jakob disease surveillance unit, and the UK National Blood
Services.
The study began in 1997. They looked at the history of donating blood
for every variant Creutzfeldt-Jakob disease patient older than 17, and set up a
registry to be followed.
They found 15 donors who were later diagnosed
with Creutzfeldt-Jakob disease.
Fifty-eight recipients of transfusable blood components from those
donors are being followed.
Ten of the recipients have lived for more
than five years after transfusion. One of the recipients became ill, diagnosis
of dementia six-and-a-half years after transfusion from a patient who had been
perfectly healthy at the time of the donation, but who became ill something
over three years after the donation.
The recipient lived for 13 months after receiving the red blood cells,
which had not been leukoreduced.
The recipient is the second oldest person to
be diagnosed with variant Creutzfeldt-Jakob disease in an age group that has
been largely spared by the epidemic.
UK authorities estimated the chance that this
recipient would have had a food borne infection varies somewhere between one in
15,000 for the whole United Kingdom or, age adjusted, about one in 30,000.
Looking at the numbers, comparing -- which I
am sure is not legitimate -- but Steve Anderson did a quick comparison of the
two studies that I just presented.
Although the numbers in the variant CJD study
are too small for statistical significance, if there is going to be a blood
borne spread, this is pretty much what you would expect it to look like at this
point in the variant CJD epidemic.
Just intuitively, this has to be considered a
presumptive blood borne spread of the infection until proven otherwise.
There is no external way of demonstrating
where this infection came from. If it
is blood borne, unfortunately, we can expect that there are going to be other
cases that come down.
Again, starting in 1987, the agency
recommended deferring donors at increased risk of Creutzfeldt-Jakob disease
from donating components.
That definition has increased over the
years. Guidelines deferring persons who
spent more than six months in the United Kingdom during the bad years were
implemented, or published, in 1999, and the most recent revised guidance
reducing the time acceptable to spend in the United Kingdom, and adding some
other high risk places, were published early in 2000. They are in the handout and available through the web.
Bovine spongiform encephalopathy has now been
recognized in 23 countries, the most recent of which in Canada, in two older cows
in May, a beef cow over the age of six, and in December of last year, in a U.S.
dairy cow that had been imported from Canada in 2001.
That cow was about age 6-1/2 years, which
means that it was born before the feed bans, which are the single most important
public health step to protect cows from infection and, by protecting cows,
protecting human beings who are exposed to their tissue.
The cow was classified by the Department of
Agriculture as disabled, although I know that the slaughterhouse has disputed
that claim, since the case was first reported.
A piece of brain tissue sent to the USDA
veterinary services laboratory in Ames, Iowa unequivocally showed both
histopathology and immunohistochemistry positive diagnosis of spongiform encephalopathy
on the 23rd of December, and it was confirmed by the world reference center in
the United Kingdom on the 25th of December.
It wasn't at all equivocal. It was a florid case of bovine spongiform
encephalopathy.
The USDA has done trace back of the 80 cows
that entered the United States with the original cow. They have been able to find about 27 of them. None of them had bovine spongiform
encephalopathy.
The meat prepared in the slaughterhouse on
the same day has been traced forward. Some of it was retrieved, and the
rendered product has been traced forward by the Food and Drug Administration.
In January, the Food and Drug Administration
issued an official press release in which it stressed that we still rely on,
and intend to enhance, five regulatory safeguards, that should provide a high
level of protection for the public against exposure to the agent of bovine
spongiform encephalopathy, the so-called five fire walls.
The first of these are the import
prohibitions that have been in place for more than 10 years, controlled by the
USDA.
The second, a surveillance system for cattle,
which has been in place for 14 years and is now to be increased.
The third is the prohibition of feeding of
most mammalian proteins to ruminants, and enhancements in that feed ban have
been announced by the FDA.
USDA has increased the precautions, making
all disabled cattle now inedible, requiring removal of CNS material from all
cattle over the age of 30 months, and tonsils and iliums from animals of all
ages, prohibiting a product called mechanically recovered meat that is likely
to be contaminated with neural tissue, and prohibiting a form of slaughter that
tends to embolize brain tissue throughout the carcass.
The FDA has announced an intention to issue
interim final guidance that will incorporate the same kinds of precautions into
requirements for FDA regulated food products.
Both agencies have a BSE response plan that
includes trace back and trace forward of the affected products.
We asked the committee to discuss the
possibility of requiring additional safeguards. Oh, by the way, the agency
recognizes that those five sets of safeguards are not perfect, that they are
not foolproof but, taken together, they would seem to provide a high level of
safety, even if there is more BSE in the country now.
We asked the committee to discuss whether
additional safeguards might be considered for bovine materials used in, or to
manufacture, injectable biological products.
Those might include selected herds of cattle
that would be fully traceable, even before the national tracing system goes
into effect.
It would have to be certified that they had
never been fed or otherwise exposed to prohibited protein, and any source heard
would have to have an active surveillance program.
There is a possibility we might consider
having selected individual cattle and tissues, perhaps requiring that materials
come from younger animals, that risk materials be removed even before the age
of 30 months, and that animals above some age, where it is reasonable to do so,
be tested for the abnormal prion protein that is the rapid diagnostic tool for
bovine spongiform encephalopathy.
To conclude, the suggestions of the
committee, as I understood them, were as follows:
Although the committee is not advisory to the
CDC or the Department of Agriculture, they felt very strongly that the CDC
should intensify its CJD surveillance efforts, and the USDA should intensify
its BSE efforts.
I was interested to see that, at the time of
the meeting, the USDA was planning to examine the brains of 40,000 cattle a
year, which was double the rate last year, and that is concentrating on
disabled cattle.
They have now decided to spend some --
according to the newspapers -- $70 million to increase surveillance to over
100,000 cattle a year, and to examine some normal appearing older cattle, as
well as disabled cattle.
The committee concluded that the recognition
of a presumptive transfusion transmitted case of variant CJD doesn't require a
change in current U.S. blood donor deferral policies, because we took the
theoretical possibilities quite seriously, as you know, from the beginning.
They also commented that, although
leukoreduction and perhaps removal of plasma from blood in experimental systems
shows some promise, that the existing science does not suggest that we should
rely on leukoreduction alone to reduce TSE risk. That is not the substitute for a donor deferral policy.
They agreed that the recognition of BSE in a
cow in the United States is of concern, and that our efforts to reduce BSE risk
in FDA-regulated products are justified.
They suggested that the Center for Veterinary
Medicine and the field office improve compliance with the feed ban, especially
on farms, and expressed a special concern for the safety of dietary supplements
containing bovine materials.
They also agreed that additional precautions
may be justified for bovine materials used in order to make injectable and
implantable products, and I will close there.
Thank you.
DR. NELSON:
Thank you, Dr. Asher. Any
questions or comments?
DR. HOLMBERG: Do you have any comments on the most recent deferments out of the
United Kingdom on people who have received transfusions after 1980?
DR. ASHER:
It is consistent with our policy, as it has been for several years. We have recommended deferral of anyone who
had a blood transfusion in the United Kingdom after 1980 to the present.
DR. NELSON:
Thank you. Next is Dr. Paul
Mied, current thinking on draft guidance for nucleic acid testing for HIV and
HCV.
Agenda Item:
Current Thinking on Draft Guidance for Nucleic Acid Testing for HIV and
HCV: Testing Product Disposition, and
Donor Deferral and Re-entry.
DR. MIED:
Thank you, Dr. Nelson. I have been asked for hard copies of my slides.
They are available out on the table.
I would like to briefly outline FDA's current
thinking on implementation of NAT for HIV-1 and HCV RNA. FDA intends that our current thinking on NAT
testing, product disposition, and donor management form the basis for a draft
guidance document to be issued for comment, that will provide recommendations
to blood and plasma establishments that have implemented, or are implementing a
licensed HIV-1 and HCV NAT method for source plasma or whole blood.
Our current thinking is that there is a need
for generalized testing algorithms to be used when NAT reactive results are
obtained on a pool of samples, or on individual samples of source plasma, or
plasma from whole blood donations.
Now, these testing algorithms should be
consistent with the manufacturers' instructions in the package inserts of NAT
tests that are already licensed, as well as for NAT tests to be licensed in the
future.
Our current thinking is that these algorithms
should also contain recommendations on unit management and labeling, look back,
and donor deferral and notification, that you don't find in the package
inserts.
We also intend to provide generalized
algorithms for donor reentry, that combine NAT and serologic test results.
Now, in general, for a master pool of plasma
samples, if you obtain a reactive, multiplex NAT -- that is a NAT that
simultaneously detects HIV-1 RNA and HCV RNA -- or a reactive NAT result for
HIV or HCV on separate NAT assays, you must perform subsequent testing, to
identify the individual unit that is NAT reactive, as the basis for the NAT
reactive result on the pool.
There are two approaches that you may employ
to resolve a NAT reactive master pool. You can test sub-pools or directly test
individual donations that made up the master pool.
This is the algorithm for resolution of a
multiplex, HIV-1, HCV NAT reactive master pool by testing sub-pools.
Now, this is essentially the same generalized
NAT testing algorithm for source plasma and whole blood that FDA presented at
BPAC in March of 2001.
However, you will see here that we have
superimposed on the testing scheme the appropriate actions for unit management
and donor management.
You may perform a resolution of the multiplex
NAT reactive master pool by testing original or freshly pooled subpools, to
identify the reactive individual donation.
Now, this resolution of the master pool can
involve testing of several layers of sub-pools. This first algorithm is more
likely to be used by establishments in deconstruction of a master pool that
contains a larger number of donations, for example, 96 or 512.
If all sub-pools are non-reactive, our
current thinking, consistent with BPAC recommendations, is to permit release of
all donations in those sub-pools, provided, of course, all serologic tests on
those donations are negative.
However, as part of an overall quality
assurance program, we would encourage you to conduct additional testing, to
determine the cause of the initial reactivity of the master pool.
When at least one reactive sub-pool is found
in each test of sub-pools, you may release all units in the non-reactive
sub-pools.
You should then go on to test individual
donations in the reactive sub-pool, using the same multiplex NAT method that
was used on the master pool and the sub-pools.
Now, in some cases, a different sample
preparation procedure may be used, according to the manufacturer's
instructions, and that is okay.
However, the primers and the probes should be
the same as those used in the multiplex NAT on the master pool and the
sub-pools.
If all individual donations are non-reactive,
our current thinking, again consistent with BPAC recommendations, is to permit
the release of all of those individual donations. If one or more of the individual donations is reactive, you may
release the non-reactive donations.
Now, this algorithm is actually three
algorithms rolled into one, one, two and three. This part of the algorithm, shown in white, which differs from
the previous slide which was mostly an algorithm in yellow, is more likely to
be used by establishments in deconstruction of a multiplex reactive master pool
that contains a smaller number of donations, for example, a pool of 16 samples,
since they would like to directly test all individual donations to resolve that
master pool, that are in the reactive master pool.
Here is also where the algorithm becomes the
same as when you are directly screening individual donations, using a multiplex
test. So, I have shown the rest of the algorithm for individual donation
testing in white.
If you obtain a NAT reactive individual
donation, you must not use that reactive donation for transfusion or for
further manufacturing into injectable products, but you should discard the
unit, or release it with labeling for research or further manufacture, with
written approval from FDA.
You must defer the donor. However, since false positive NAT results
have been known to occur, the donor is eligible for reentry, if all serologic
tests are negative.
You should test the reactive donation using a
discriminatory NAT, which is essentially the same NAT test for the RNA of the
individual viruses.
If the discriminatory NAT is positive for
HIV-1 RNA and/or HCV RNA, you must notify the donor of the deferral, and the
basis for their deferral, including test results, and perform look back for HIV
and/or HCV, to identify potentially infectious prior donations from that donor,
and to do product retrieval of those prior collections, and notification of
transfusion recipients of products from those prior collections.
If the donation is negative on the discriminatory
NAT for both HIV-1 RNA and HCV RNA, we recommend that you perform one of the
following two options.
First of all, you may proceed without further
testing and notify the donor of their deferral, and perform look back for HIV
and HCV. Secondly, for purposes of
donor notification, you may perform another NAT test on a sample from the
donation.
If you test a new sample from the original
donation, you may use the original NAT or the discriminatory NATs, or an
additional NAT, and that is a NAT that uses an amplification technology and/or
primers that are different from those that were used in the original NAT in the
master pool. Alternatively, you may
test the same sample, as in the previous NAT test, for example, using an
additional NAT.
If you perform another NAT test on the same
sample or a new sample from the donation and it is reactive, you must notify
the donor of their deferral and the basis of the deferral, and perform look
back for HIV and/or HCV.
If another NAT test on a sample from the
donation is non-reactive, you may explain to the donor that the first test
result, while reactive, was not conclusive, and that the donor is probably not
infected with HIV-1 or HCV. However, there is a slight risk that the initial
test result was a positive result, but cannot be excluded without follow up
testing of the donor.
So, as a precautionary measure, we would
recommend that you retrieve products from prior collections from this donor.
However, due to the low probability that any
of the prior collections was infectious, we do not recommend that you notify
transfusion recipients in this case.
Now, the second generalized algorithm that I
will show today is the algorithm for resolution by testing sub-pools of a
master pool that was reactive, not on a multiplex test, but on separate tests
for HIV-1 RNA or HCV RNA.
Now, in this case, by initially doing
separate tests for HIV-1 and HCV on the master pool, you have essentially
already done the discriminatory NATs.
So, the algorithm is much simpler.
As I described before, you would test
sub-pools and release units, then test the individual donations, using the same
NAT method for the individual virus that was reactive on the master pool.
Now, when you obtain a reactive individual
donation by that separate HIV-1 or HCV NAT test, all you need to do is discard
or re-label the unit, defer the donor, notify the donor, and perform look back
for HIV or HCV, whichever is appropriate.
Now, as before, this algorithm is also
actually three algorithms rolled into one.
This short portion which I am showing here in white, which is more
likely to be used by establishments in deconstruction of a separate test
reactive master pool, that contains a smaller number of donations -- for
example, a pool of 16 samples -- since they would like to directly test all
individual donations in a reactive master pool.
Here is also where the algorithm becomes the
same as when you are directly screening individual donations using separate
tests. So, I have shown this part of
the algorithm for individual donation testing in white.
Now, FDA's current thinking is that there is
also a need to develop schemes for reentry of donors, deferred because of
falsely reactive NAT test results.
These algorithms could be used by those establishments that choose to
perform donor reentry.
With implementation of NAT, we see the need
to update and supersede the previously recommended reentry algorithms for
donors deferred because of serologic HIV or HCV test results, since the reentry
procedures for those donors should also integrate both NAT and serology.
Our current thinking on possible reentry
schemes, which I am about to show you, is essentially the same as what FDA
proposed at BPAC in June of 2001, with one exception that I will describe.
Our current thinking is to recommend reentry
procedures for three groups of donors, deferred because of HIV test results.
The first group consists of donors who had
NAT reactive results but were seronegative, such as those deferred in the NAT
testing algorithms that I just described.
This includes donors previously deferred because of reactive results on
an investigational HIV-1 NAT.
The HIV-1 p24 antigen EIA may not have been
performed, if it was replaced by a licensed NAT that was validated to replace
the HIV-1 p24 antigen test.
The HIV discriminatory NAT on the donation
may have been either positive or negative.
If an additional NAT was performed, it must have been negative.
The second group consists of donors with
non-reactive NAT who had a repeatedly reactive screening test for HIV antibody,
and an HIV-1 western blot or IFA that was negative, or was not performed, or an
HIV-1 western blot result that was indeterminant, and viral bands may be
present.
This includes donors previously deferred
because of repeatedly reactive anti-HIV test results prior to the initiation of
testing by NAT.
Donors with negative, or indeterminant,
western blots are eligible for reentry only if the HIV-1 p24 EIA, if it was
done, was negative, and if a second, different licensed HIV-2 EIA was negative
or, if that second HIV-2 EIA was repeatedly reactive, then an investigational
HIV-2 supplemental test was not positive.
The third group of donors eligible for
reentry would be those who were non-reactive on NAT, and who were negative on a
screening test for HIV-1 antibody, but who were repeatedly reactive on an HIV-1
p24 antigen EIA, with a positive or an indeterminant result on the
neutralization test.
Now, this is a change from what FDA
previously proposed at BPAC. Donors
with a positive result on the HIV-1 p24 antigen neutralization test may also be
considered eligible for reentry, since we know that there are many donors who
had false positive neutralization test results, who are currently non-reactive
by HIV-1 NAT, and negative by anti-HIV-1, 2 EIA.
For all three groups of donors deferred
because of HIV NAT or HIV antibody or antigen test results, we are considering
recommending that a follow up sample be taken from the donor after a minimum
time period of eight weeks, for follow up testing by both a licensed HIV-1 NAT,
and a licensed HIV antibody EIA.
If both the HIV NAT and the anti-HIV-1, 2 EIA
test on the follow up sample, taken at least eight weeks later, are negative,
the donor may be reentered, that is, becomes eligible for future donation.
A donation then taken at a later date would
then be tested using the usual battery of required screening tests.
Therefore, two NAT tests and two EIA tests
would be performed and must be negative, before a unit from that donor could be
used.
FDA's current thinking is also to recommend a
reentry procedure for two groups of donors deferred because of HCV test
results.
The first group consists of donors who had
NAT reactive results, but were seronegative.
This includes donors previously deferred because of reactive test
results on an investigational HCV NAT.
The HCV discriminatory NAT, again, on the
donation may have been either positive or negative but, if you did an
additional NAT, it must have been negative.
The second group consists of donors with a
non-reactive NAT who had a repeatedly reactive screening test for HCV antibody,
with an HCV RIBA that was indeterminant or negative, or was not performed.
This includes donors previously deferred
because of a repeatedly reactive anti-HCV test result prior to the initiation
of testing by NAT.
Now, for purposes of reentry, we are
considering recommending that a follow up sample be taken from the donor after
a minimum time period of six months, for testing by both a licensed HCV NAT and
a licensed anti-HCV EIA.
If both the NAT and the EIA test on the
follow up sample, taken at least six months later, are negative, the donor may
be reentered, that is, becomes eligible for future donation.
A donation then taken at a later date would
be tested using the usual battery of required screening tests. Therefore,
again, two NAT tests and two EIA tests would be performed, and must be
negative, before a unit from that donor could be used. I think I will stop there and take any
questions you have.
DR. LINDEN:
Can you go back to the third algorithm slide, the one at the bottom of
page two of the handout?
If the follow up testing is negative for
HIV-1 and HCV, what are you notifying the donor and why are you performing look
back, if the test is negative, the lower left-hand quadrant there.
DR. MIED:
That is one of the options. You may just decide to do that, as in the
case as if it were positive, or go on to perform an additional test.
DR. LINDEN:
So, you are saying that look back is conservative, but you are
presumably then telling the transfusion service of the test results, and they
are probably not going to do anything with it, and what -- would you be
notifying the donor then?
DR. MIED:
You would be notifying the donor of their deferral.
DR. LINDEN:
On their deferral based on these negative test results.
DR. MIED:
If you go back one slide, you have two reactive NATs. You have a
reactive donation NAT and, before that, you had a reactive master pool, if you
were deconstructing a master pool.
So, you still haven't explained the reason
for this, even though you have a negative discriminatory NAT. So, yes, it is precautionary.
It is an option, for donor notification
purposes, to make it more clear what you tell the donor, you may selection
option two of those two options, and do an additional NAT.
DR. BUSCH:
If I can follow up on that, as you know, Paul, we have done a large
study where we turn these non-discriminative reactants.
They came to a pool but, because of the false
positivity of the assay, a subset of these resolved pools have a reactive multiplex,
and then they don't discriminate.
We followed up over 500 of these, and none of
these donors proved to be infected and, on follow up, they are all negative on
re-testing. So, the potential that
these may be infected is extremely low.
If you go conservative, I could see that, but
I certainly don't think it is warranted to be notifying and alarming
recipients.
In general, I think the reentry algorithms
are very good, and they are clearly allowing a lot of donors to reenter.
What I don't understand, though, is the
option of screening individual donations coming into this. If you are concerned
that those non-discriminative reactors, where you can't -- you not only can't
discriminate, but you rerun the multiplex and you can't repeat the reactivity
on those samples, you are concerned that they may have some very low risk of
infection. Therefore, you are deferring
those donors and requiring that they be reentered.
Yet, if you screen by individual donation and
you similarly don't discriminate, you are actually allowing those units to be
used, to be transfused, and not deferring those donors.
It is basically, if your initial reactive,
non-repeatable on individual donation screening, you are allowing those units
to be transfused. Yet, for the same reasons of very low viral load, it is
theoretical that one of those could be infectious.
For west nile, such units have to be
discarded and the donor deferred. It
seems to me that there is a disparity in the policy, whether you do individual
donation or pooled testing.
DR. MIED:
I go back to the recommendation made by BPAC in June 2001, which said
that it is all right to release all non-reactive donations because the data
that we saw when the NAT tests were under IND showed that, invariably, it was
the master pool that was contaminated, and that you can rely on this individual
donation test.
Now, if you go to the next slide, and the
next one, I think you are talking about where you have had a non-discriminated,
and now you come down to non-reactive. You are still not releasing the unit.
DR. BUSCH:
No, I am going back to that same slide. I understand that, if you have
done pool testing and then you are building in a dramatic increased
concentration.
If you go back to the previous two slides, it
is a negative individual should be release-able. It is that right colored orange kind of bar coming in.
That implies that, if you did individual
donation screening and you were initial reactive, on the right, the orange on
the right. It is allowing you to do individual donation screening. If that is reactive and then you re-test and
it is non-reactive --
DR. MIED:
You mean, it doesn't discriminate?
DR. BUSCH:
It even doesn't repeat, or it doesn't discriminate, either one.
DR. MIED:
I think we discussed this at BPAC.
The concern was raised about repeating, time after time, the multiplex
test that you performed initially. You
should go to the discriminatory NAT.
DR. BUSCH:
Then both are discriminated as negative. Then you are allowed to release
that unit.
DR. MIED:
Go to the next slide. No, you are not. This is a concern raised because
we have had a couple of instances -- one was the San Antonio case -- where a
unit did get through and, even though it was non-discriminated, turned out to
be infected. So, we are not allowing
release of the unit even with performing another test.
DR. BUSCH:
If I am understanding correctly -- I was just trying to understand how
you were sort of having three algorithms kick in.
So, if you are doing individual donation
testing on a multiplexed assay, you are reactive, you do the discriminatory and
they are negative, now that unit has to be discarded, the donor deferred and
reentered.
DR. MIED:
Yes, that is correct.
DR. BUSCH:
That is not what the package insert allows today.
DR. MIED:
Yes, I know. This is going to
require some slight modification to the package insert, to take care of this
rare event that we are talking about. The inserts do not go as far as this.
MS. KESSLER:
Debbie Kessler, New York Blood Center. Two quick questions. In the past,
a donor was not eligible for reentry if they were ELISA repeat reactive on two
donations.
Is that now wiped out, that we can start with
historical donors, reentering them, donors who had never had NAT done, for
example?
DR. MIED:
I don't believe that is the case for either HIV or HCV. As soon as they are repeatedly reactive on
either of those antibody tests, they were deferred.
MS. KESSLER:
But they were eligible for reentry if they were repeat reactive only on
one donation. If they were repeat
reactive on a second donation, they are not eligible for reentry. Can we now go to those historically deferred
donors and reenter them.
DR. MIED:
Yes.
MS. KESSLER:
My second question is, have you discussed the length of look back? How far back do you go based on the NAT
only?
DR. MIED:
Yes, we have discussed that. I
believe, to be extra precautionary, for HCV, I think we are going back one
year, for both HIV and HCV. You are
talking about a NAT reactive?
MS. KESSLER:
NAT only.
DR. MIED:
Yes.
MS. KESSLER:
Thank you.
DR. NELSON:
Okay, I would like to move on.
The last update is current thinking on final guidance for use of nucleic
acid testing on pooled and individual samples.
We have two people presenting.
Agenda Item:
Current Thinking on Final Guidance for Use of Nucleic Acid Testing on
Pooled and Individual Samples from Donors of Whole Blood and Blood Components
to Adequately and Appropriately Reduce the Risk of Transmission of HIV-1 and
HCV.
DR. AKOLKAR:
I am Pradip Akolkar. I am with FDA. I am going to present today the
current thinking about the implementation of HIV-1 and HCV NAT for screening
donors of whole blood, blood components, including source plasma and source
leukocytes. The final guidance on this
subject will be published very soon.
This final guidance document will combine the
published draft guidance documents for source plasma and another for whole
blood and blood components.
We believe that implementation of HIV-1 and
HCV NAT for donor screening will improve the safety of the nation's blood
supply, since NAT can detect the evidence of HIV-1 and HCV infection
significantly earlier than the currently licensed tests, using antibody and
antigen detection technology.
We recently licensed HIV-1 and HCV NAT for
donor screening for whole blood and blood components, including source plasma
and source leukocytes. The HIV-1 NAT
has also been approved to replace the HIV-1 p24 antigen testing.
FDA is considering limiting the requirement
for NAT to the units that are negative for HIV-1 and NCV antibody tests.
We believe that HIV-1 and HCV NAT should be
included in the screening of blood donations, including the donations of whole
blood and blood components, including source plasma and source leukocytes.
This is in addition to the FDA licensed HIV-1
and HCV antibody tests, unless those donations are to be discarded on the basis
of their reactive results on antibody to HIV-1 and HCV tests.
We also believe that, for donations that are
reactive for HCV antibody, HIV-1 NAT should be performed, and those that are
reactive for HCV antibody, HIV-1 antibodies should be performed and HCV NAT
also.
On implementation of HIV-1 NAT, it is
approved for replacing the HIV-1 p24 antigen testing. You may discontinue testing for HIV-1 p24 antigen.
To identify the donations in the window
period, all donations of whole blood and blood components, including source
plasma and source leukocytes, that are non-reactive for HIV-1 or HCV antibody
tests, should be screened with the licensed HIV-1 and HCV NAT. This testing may occur concurrently with
antibody tests.
We recommend that all donations of whole
blood and blood components that are initially reactive for HIV-1 and HCV
antibody tests should be screened for HIV-1 and HCV-NAT unless such donations
are to be discarded.
We considered that, in the case of HIV-1 and
HCV antibody tests, especially reactive donations that are discarded, NAT may
provide useful information about the infection status as part of donor
notification, especially in the whole blood setting, due to large intervals
between the donations, and you may want to confirm about the false reactivity
on the antibody tests.
On the other hand, we believe that, in the
setting of source plasma collection, the short inter-donation intervals, which
is sometimes as little as 48 hours, high frequency of donations and delay in
getting NAT results, it is likely that the infected donor has been found
reactive for antibody tests -- found reactive at HIV-1 or HCV NAT tests. As a result, it is likely that such donors
will be deferred prior to obtaining NAT results.
Consistent with this existing requirement,
donors who test reactive by any of the donor screening tests must be deferred
from donating.
You also must perform supplemental testing
and you must make reasonable attempts to notify donors of their deferment.
We understand that the HIV-1 and the HCV NAT
testing samples of donors of whole blood and blood components, including source
plasma, may involve complex pooling and testing systems, and recognize that
this may require time to implement the systems.
We therefore are allowing six months from the
date of publication of the notice in the Federal Register, announcing the
availability of final guidance, for the implementation of the licensed NAT for
HIV-1 and HCV.
Judy Ciaraldi will present now current practices
for reporting by blood establishments of the NAT testing results. Thank you.
MS. CIARALDI: Good afternoon. Blood and
plasma establishments have started to implement NAT testing of their blood and
plasma donors.
What I am going to do today is describe the
procedures that we have been following for them to report this change to
us. Except where I note, blood
establishments refers to both blood and plasma establishments.
Only licensed blood establishments are
required to report changes in their operations to CBER. Such a change in operation would be adding
NAT testing of their donors, or dropping HIV antigen testing.
The types of reports that we expect to see
are those coming from licensed blood establishments that will be performing the
NAT procedures within their facility, or those that will contract with another
facility to perform the NAT procedures.
As a footnote, all facilities that perform
manufacturing steps, including NAT testing and NAT pooling, must register with
the FDA.
We have asked the blood establishments to
submit the following information to supplement their license, to include NAT
testing.
First, a cover letter that describes their
request to us, and includes whether or not they are going to drop the HIV
antigen and replace it with the HIV NAT.
The 356 biologics license application form
always must be included with any submission sent to FDA. Labeling is also included, and I am going to
go into this in more detail later.
We have also asked blood establishments to
include information about their NAT procedures, and where the NAT procedures
will be performed.
After this, I am going to go over how the
blood establishments report to us when they do implement NAT. Keep in mind, as Pradip said, that there are
some very complex systems out there used to perform the NAT procedures.
Just to bring it down a level in complexity,
there are two basic types of scenarios, a test kit scenario, where the testing
and the pooling were validated together as a kit, and a testing and pooling
service scenario, where the testing and validated have been pooled
independently, and can be performed or provided as a service by a specific
establishment.
I am going to start with the test kit
scenario first. In this case, the licensed blood establishment can implement
this within their own facility.
If they are currently approved to perform
infectious disease testing on donors, and they are adding that, we have
recommended that they can report this to us in their annual report.
If they are creating or setting up a brand
new laboratory to do infectious disease testing, with or without NAT, we
recommend that that be reported to us as a prior approval supplement.
Just to streamline this presentation, any
time a new laboratory is being set up, we always recommend that that come in to
us as a prior approval supplement. You will see it on subsequent slides.
Licensed blood establishments will often send
their samples to an outside test lab that is performing the service for them
under contract.
In some cases, the current outside contract
test lab that a licensed blood establishment has, will be adding, or has added,
the NAT procedures to their regular testing profiles.
When that happens, when a previously approved
contractor that is part of their licensed application is adding NAT, we have
told the blood establishments that they can report this to us in an annual
report.
In some cases, blood establishments have had
to change contractors or add contractors in order to implement NAT testing on
their donors.
In that case, that comes in as a changes
being effected in 30 days SOP limit.
Lastly, if it is a new laboratory, it is a prior approval SOP limit.
In this case here, we are talking about the
testing and pooling service scenario.
Under this scenario, the testing and pooling can be performed at the
same facility or at different facilities.
Currently, this process is in place for
testing source plasma donors, and you will see that this is focused on them.
The use of a testing facility right now can
only be arranged as a contract. There is only one facility that performs the
testing for source plasma donors in this manner.
So, the licensed source plasma establishments
will be contracting with this testing service facility to perform their NAT
testing as a change is being effected in 30 days.
Now, the pooling can be implemented within a
facility or it can be contracted by the blood establishment and be performed at
a pooling facility.
In the scenario where the blood establishment
will be performing pooling within their own facility, and they already perform
infectious disease testing but they are adding pooling, we have recommended
that this type of change come in to us as a change that is being effected in 30
days SOP limit.
If they are setting up a new lab, again, to
incorporate the pooling, that would come in as a prior approval SOP limit.
The most common scenario is that the licensed
blood establishment will contract with an outside facility to perform their
pooling for them.
In this case here, the contractor is an
infectious disease test lab that is adding pooling, or it is a separate
independent pooling facility that has been approved to perform pooling.
In these situations, the licensed blood
establishment, if they use these facilities, will report to us that a change is
being effected in 30 days. If a
contractor is setting up a new lab, again, that is a prior approval SOP limit. The pooling and the testing can be reported
to us within the same submission.
We are going to focus on the testing
statement that is incorporated into the labeling. All blood and blood components must be labeled with their test
results.
In the case of transfusible products, the
test statements about NAT and all the other viral markers are included in the
instruction circular, known as the circular for information. The latest one, published in July 2002, does
contain verbiage pertaining to the NAT testing.
Components for further manufacture have their
test statements directly on their label.
This includes source plasma products and recovered plasma products.
The label test statement that we have been
approving is non-reactive for HIV-1 RNA and HCV RNA. Now, a product may contain the negative test statement label if
they are, indeed, fully tested and found negative.
In the case of source plasma, they can be
pending their testing, contain this label pending testing, waiting for the
results, and stored on site in the facility, or stored at an off site storage
facility under contract to the source plasma establishment. They are still under the licensed source
plasma establishment's control.
If any blood establishments still have not
reported to us, any blood or plasma establishments, still have not reported
their NAT implementation to CBER, we urge you to call your consumer safety
officer and discuss the details of the submission.
The plasma industry has asked CBER to
consider approving source plasma establishments to ship source plasma to a
fractionator that is operating under a different license than the original
collector, prior to receiving the NAT results.
We responded in a letter back to the plasma
industry in July of last year, that we consider these types of requests to be
variances of our regulations, and we would consider approving these variances
under the following conditions:
That the units be negative for all the
regular screening tests before they are shipped; that the fractionator will
store, remove and destroy unacceptable units as a contract service to the
licensed plasma collector; and that if, for any reason, the fractionator is
trans-shipping, or shipping that product to another fractionator, they have to
re-label it.
Re-labeling is needed because the plasma
collection centers will be labeling their source plasma as pending the net
results.
So, once the net results are negative, and
they are now being transferred to another fractionator, they have to be labeled
as being totally negative.
Again, anyone that is interested in requesting
this variance should discuss this with their consumer safety officer.
This has just been a brief overview of our
reporting categories for the blood and plasma establishments for implementing
the NAT testing of their donors. Thank you very much.
DR. NELSON:
Thank you, Judy. Any
comments? I think Dr. Michael
Fitzpatrick wanted to make a brief statement -- quite brief, because we want to
get lunch. Oh, okay. Why don't we break and come back at 2:00
o'clock.
[Whereupon, at 1:30 p.m., the meeting was
recessed, to reconvene at 2:15 p.m., that same day.]
A
F T E R N O O N S E S S I O N (2:25 p.m.)
DR. NELSON:
For desert, we are going to discuss supplemental testing for human
immunodeficiency virus and hepatitis C virus.
Robin Biswas.
Agenda Item:
Open Committee Discussion. Supplemental Testing for HIV and HCV.
Introduction and Background.
DR. BISWAS:
Thank you, Dr. Nelson. Well, for
the rest of the day, the remains of the day, we will be discussing supplemental
testing of donors for HIV and HCV. I am Robin Biswas. These slides were put together by myself and Indira Hewlett, and
I will be giving the presentation.
We are going to be discussing the utility of
various supplemental testing strategies to confirm a repeatedly reactive enzyme
immunoassay screening test result for HIV, using a western blot, nucleic acid
tests, or a second EIA, sort of dual EIA strategy and, for HCV, using the RIBAR
-- that is the recombinant immunoblot assay -- nucleic acid tests, and a high
signal to cut off ratio in the screening EIA, and this will be gone into great
more detail by the next speaker.
Now, the reason for discussing this is that,
in a 1998 MMWR, CDC recommended that, in the clinical laboratory diagnostic
setting, an anti-HIV reactive -- read, repeat reactive -- screening test result
should be verified by a more specific supplemental test such as the RIBA, and
that is exactly what is also done in the blood donor setting as well.
Now, in 2003, CDC, in that particular MMWR,
repeats and emphasizes the desirability of performing more specific
supplemental testing on screen reactives.
However, they offered an option for reporting
positive test results using high signal to cut off ratios in the screening
test, again, in a clinical laboratory diagnostic setting.
Now, just to go through this again briefly --
Dr. Kaplan went through something very, very similar earlier today -- the
current testing of blood donations for antibodies to HIV and HCV and, of
course, for anti-cor and HBsAg, you test a single sample using an EIA screening
test.
If it is non-reactive, you use the unit and
retain the donor. If it is reactive
above the cut off, it is called initially reactive.
At that stage, you test the sample, that
sample, initially reactive sample, in duplicate. If both duplicates are non-reactive, you use the unit and retain
the donor, and test sample in duplicate.
Things begin to happen if either or both
duplicates test reactive. The unit is then stated to be repeatedly reactive,
not positive by the way. The unit is
not used, and you defer the donor, and the donor is evaluated by more testing
using supplemental assays.
Now, the supplemental testing on EIA
screening test repeat reactives, for anti-HCV you use RIBA and, for anti-HIV,
you use a western blot or an IFA, followed by an anti-HIV EIA-2, if you have an
indeterminant result in the western blot. I should have had the western blot
indeterminant, if western blot indeterminant results are obtained. The IFA, you just get positive or negative
results, no indeterminants.
Now, it is important to note that each
screening test reactive donation must be tested by a supplemental test if
approved for such use by FDA, and that is enshrined in that regulation up
there.
Also, the donors must be notified of their
deferral. Also, supplemental test
results, also an attempt must be made to obtain supplemental test results prior
to the donor notification, and all of that is also enshrined in the regulations.
Alternative donor testing algorithms in the
donor setting, in the donor testing setting, not using supplemental tests,
would conflict with the regulations.
We are of the opinion that confirmation by
so-called orthoganol testing -- that is really testing using a different
technique -- is advantageous over statistical validation methods, such as using
a second EIA, or using a high EIA sample to cut off ratio, rather than using a
blot test, for example, if you are testing with EIA.
Now, why perform supplemental testing on
donors in particular? Well, providing
deferred donors with accurate information about their disease status and
deferral helps ensure a healthy donor population, and this impacts directly on
blood safety and presenting communicable disease transmission.
Information from supplemental testing can be
used to evaluate the donor for possible reentry into the donor pool. So, requalification of donors contributes to
blood availability.
Now, testing in different settings. The donor
setting and the medical diagnostic setting where this testing is going on is a
really very, very different situation.
In the donor setting, you are testing highly
selected, very low risk population, as tested outside the health care
environment.
In the medical diagnostic setting, there is a
higher risk population. There is a medical index of suspicion, and there is the
doctor patient relationship, which permits additional considerations.
Also, evidently in the points of care where
rapid HIV testing is performed, there is really an inability to perform delayed
confirmatory testing, which takes a long time to do.
So, we would like the committee to discuss
the scientific merit and public health benefit of supplemental testing in a
blood donor setting.
So, we are just concentrating on testing
blood donors and we are not discussing in a medical laboratory diagnostic
context.
We would like you to discuss the relative
performance of supplemental testing strategies for HIV and HCV.
For HIV, that will include western blot,
nucleic acid testing and a second EIA. For HCV, the RIBA, NAT testing and high
sample to cut off ratio in the screening EIA.
Now, these really aren't questions for the
committee to vote on, but they are really sort of discussion points for the
committee to focus on.
We would like you to comment on the relative
performance of RIBA versus HCV, and RIBA versus signal to cut off ratio, in the
EIA screening test for anti-HCV, to confirm or validate a screening test result
in the blood donor testing setting.
We would like you to comment on the relative
performance of western blot versus HIV NAT, and western blot versus a second
EIA for anti-HIV, to confirm or validate a reactive screen test result in the
blood donor testing setting.
That is all I have to say. We have four speakers. Two of them are from CDC. Dr. Wendi Kuhnert will be talking about HCV
testing in diagnostic setting, and Dr.Hu will be talking about HIV
testing. We have Susan Stramer and Mike
Busch, who will have a lot of data gathered from blood donors. Thank you.
Agenda Item:
Performance of HIV and HCV Supplemental Assays. Wendi Kuhnert.
DR. KUHNERT:
Good afternoon. As Robin said, I
am going to be talking about the published guidelines, the laboratory
guidelines that CDC published about a year ago, instructing labs on how to
report results for anti-HCV test results.
Before I begin, I want to emphasize that,
when we published these guidelines, we did explicitly state, on a couple of
occasions, that these are not supposed to be applied for the blood donor
setting and, when we tested them, we were only looking for, as Robin said, the
clinical and diagnostic setting.
So, these guidelines were developed with a
large working group, and you can see the members on this slide. We included members from a variety of
federal agencies, as well as numerous professional organizations. We also included other experts from
university and VA medical center laboratories.
Then, before publishing these documents, we
also included collaborators from blood centers, as well as the manufacturers
for each of the assays.
Just to reiterate, these guidelines are not
intended to do a few things. They are not intended for the screening or
notification of blood, plasma or other donors, as this testing is provided for
under current FDA guidance and regulations.
These guidelines are also not intended to
change the manufacturer's labeling for the performance of a specific
assay. That is, there is no requirement
for the change in the package insert that has already been approved by the FDA.
Finally, it is not meant to dictate medical
practice, that is, what test a physician can and should order for appropriate
medical follow up.
So, just to review a little bit, testing for
anti-HCV, it is currently recommended to screen for anti-HCV, to identify
persons with HCV infection.
These antibody screening assays are then
followed up with a more specific assay for any screen test positive result that
is obtained.
This algorithm is the algorithm that has been
recommended by CDC since 1998, and is similar to the algorithms for hepatitis B
surface antigen, as well as anti-HIV testing.
We believe that verifying the presence of
anti-HCV with a supplemental test will minimize unnecessary medical visits, as
well as psychological harm for persons who test falsely positive.
In addition, verifying these data will ensure
counseling and medical referral and evaluation, that is targeted for persons
who are serologically confirmed as having been HCV infected and, therefore,
eliminate follow up of the numerous false positives that do exist.
One of the factors that we believe is very
important to keep in mind when looking at any screening assay is its
performance characteristics.
One of the most important is positive
predictive value, or PPV. This is
defined as the probability that a person with a positive test is a true
positive.
One of the things that any laboratory would
need to keep in mind, when looking at a screening assay, is that this value can
vary greatly, depending upon the prevalence of infection within the population
being screened.
We have shown, within this document as well
as other studies that, for hepatitis C, even with a very high sensitivity and
specificity, the positive predictive value can fall to 50 percent in a low
prevalence population.
This variation in the positive predictive
value leads to my next slide, where we discuss some of the venues in which
anti-HCV testing is used.
Obviously, it is used for the clinical
diagnosis of the etiology of liver disease.
It is also used for post-exposure management.
This assay has been used very commonly and
routinely in the screening of asymptomatic persons. It is this situation where
the positive predictive value of this test comes into play.
These asymptomatic persons are most likely
being tested for the first time and, because of this, their risk for infection
is highly variable.
These screening situations may be screening
high risk patients, or the worried well, which is a very low risk population.
In these lower risk populations, with a
positive predictive value of 50 percent, it becomes very necessary to follow up
an anti-HCV positive with a supplemental assay.
Finally, another location for anti-HCV
testing is public health surveillance.
In this situation it would be used to monitor the incidence and
prevalence, to target and evaluate further prevention efforts.
So, with this information on the anti-HCV
test, I would like to now look at some of the current testing practices.
As Robin mentioned, in 1998, the CDC
published recommendations that all screen test positives should undergo more
specific testing in a supplemental format.
At that time, the CDC attempted broad
educational programs to target physicians and other health care providers to
try to get this message out.
Unfortunately, this has little impact on
testing practices, and we found that there was substantial variation in
algorithms used by a number of laboratories.
We found that many laboratories were
reporting screen test positive results without performing any supplemental
testing.
Those laboratories that did perform
supplemental testing used a variety of different methods, and there really
wasn't any routine algorithm that was used across laboratories.
We believed at the time that, without the
additional information -- i.e., a supplemental test result -- the physician, as
well as the laboratory, is not able to determine the true antibody or HCV
infection status.
To show you what we found, when we looked at
some of these testing practices, this slide is showing two surveys that were
performed in 2002.
We surveyed testing practices in state and
territorial public health labs, as well as VA medical center laboratories.
Some of the initial questions we asked, we
were looking at what tests were offered by these labs. What we can see is that 65 percent of public
health labs, and 100 percent of the VA medical center laboratories were
offering anti-HCV screening tests at that time.
However, what we can see is that, when we
look at the supplemental tests, such as the RIBA or the qualitative or
quantitative NAT assays, the numbers were quite varied.
Basically, the take home point was, not all
laboratories were even performing supplemental tests, let alone performing them
on each anti-HCV positive result.
Another question that we asked within this
survey was what type of algorithm was being used, did the lab have reflex
testing set up for their anti-HCV positive results.
We asked if laboratories were performing
supplemental testing on all screen test positives, as was recommended in the
1998 recommendations.
We can see that 35 percent of public health
labs, and only 22 percent of VA medical center laboratories, were following the
CDC recommendations.
We also asked if they were performing testing
on low positives only, and those would be the weaker positives. Not many labs
were performing testing in this method.
Then we asked if they were only offering
supplemental testing based on a physician request. Seventeen percent of public health laboratories were following an
algorithm such as this, whereas the majority of the VA medical center
laboratories were relying upon the physician requesting the testing to perform
a supplemental assay.
So, with our review of the testing practices,
and our belief that the recommendations were not being followed, we decided to
look into publishing new guidelines.
We wanted to propose an algorithm, a standard
algorithm, that could be used by all laboratories that performed in vitro
diagnostic testing.
As I said earlier, this was never intended
for the screening or notification of blood donors. We believe that the use of the supplemental tests on all screen
test positives, as recommended in the 1998 recommendations, was the best method
for the blood donor setting.
So, we believe that this standard algorithm
would ensure that the results would reflect the true antibody status of the
patient, and that this result would be a true positive, independent of clinical
information or origin of the sample.
What we mean by this is that, independent of the prevalence of disease,
the algorithm would perform the same.
We also proposed in these guidelines that
further education needed to be undertaken.
We needed to emphasize the importance of more specific testing, as well
as the accurate interpretation of screening and supplemental test results.
We wanted to define when more specific
testing should be used, as well as which assays were best to use.
Finally, for the diagnostic setting in which
supplemental testing is very costly, we wanted to eliminate cost as a barrier,
or at least limit cost as a barrier to more specific testing.
Within our guidelines, we offered two
options. The first option, as Robin
stated, is to follow the original 1998 recommendations, which stated that more
specific testing should be performed on all screen test positives.
However, in these guidelines we were also
able to offer a second option, which included performing supplemental testing
on samples that had a screen test positive signal to cut off ratio of a certain
value or less.
As I said earlier, we wanted this cut off to
perform identically, regardless of the population being tested. So, in screening situations, as well as in
the diagnostic hospital laboratory, the algorithm would perform the same way.
So, to get into a little bit of the data that
we showed in these guidelines, we evaluated anti-HCV signal to cut off ratios
from all of the platforms that were currently available for diagnostic testing.
These were the ORTHO 3.0 enzyme immunoassay,
the Abbott 2.0 enzyme immunoassay, as well as the ORTHO vitros enhanced
cumuluminescent assay, which I will refer to as the CIA.
We also looked at these assays in conjunction
with more specific tests. We looked at
the RIBA 3.0 as well as a few different nucleic acid amplification techniques.
Just to reiterate, we wanted this cut off to
perform well regardless of the population. So, it was important for us to look
at study populations that covered a range of anti-HCV prevalence.
As you can see, we looked at patients that
were selected for risk and had an anti-HCV positive percentage of greater than
25 percent, all the way down to college students that were anti-HCV positive
less than one percent.
As you can see, we also looked at a variety
of populations in between, so that we could ensure that our cut off would
perform the same.
This slide is looking at some of the data
that we obtained, looking at all of the populations. What we can see is that
the percent RIBA positive was plotted according to its EIA signal to cut off
ratio.
What is very clear, if we look at the far
right-hand side of the slide, samples with a signal to cut off ratio of greater
than 3.8 were RIBA positive greater than 90 to 95 percent of the time, whereas
samples with a signal to cut off ratio of less than 3.8 were variably positive,
but generally speaking, were positive less than 20 percent of the time.
So, for the EIA, we chose this 3.8 as the cut
off for our further evaluation. If we look at the next slide, here we show a
summary of the data that we obtained with all of our populations.
This time, instead of looking at the specific
populations according to their study, I have grouped them by the prevalence of
anti-HCV positivity.
Again, we were looking at the percentage of
samples that were RIBA or NAT positive, stratified by their EIA signal to cut
off ratio. As I said, that ratio we set at 3.8.
What we can see is that samples with a cut
off greater than or equal to 3.8 were RIBA or NAT positive greater than 80
percent of the time. Generally
speaking, for the RIBA, they were actually positive greater than 95 percent of
the time.
Then, if we looked at the samples with the
lower signal to cut off ratios, these were rarely positive and, generally
speaking, were positive less than five percent of the time.
So, just to reiterate, one of the reasons
that we believe that these guidelines should be limited for diagnostic testing
is based on the fact that it isn't 100 percent.
When these test results are reported out, we
suggest they are accompanied by a comment indicating that only about 95 percent
of the time would a signal to cut off ratio of greater than or equal to 3.8 be
representative of a true positive and, thus, refer the requesting physician to
refer that patient on for further medical evaluation.
The next slide is looking at the same data,
but this time with the CIA assay. As
you can see, we chose a signal to cut off ratio of 8.0 for this assay, due to
the fact that its linear range is quite different from that of the EIA.
Again, we saw the same results. If we picked
an appropriate cut off, the assay would perform the same, regardless of the
population prevalence.
In this situation, with a cut off of greater
than 8.0, if the cut off was greater than this, then the sample, or these
results, were then highly indicative of a true positive, whereas, samples with
a result less than 8.0 were indicative of a false positive.
So, this is just summarizing some of the data
that was actually very important to the diagnostic labs, because one of their
big questions is, okay, how much is this going to cost.
This just summarizes that, in a typical
diagnostic setting, a laboratory would have probably moderate to high rates of
HCV prevalence, shown here as 10 to 20 percent.
In these type situations, the laboratory
would only be required to perform supplemental testing on less than 15 percent
of their samples.
This is where we hoped the laboratory would
see a cost savings over the other algorithm, which required supplemental
testing on all positives.
So, we propose that, using a screen test
positive signal to cut off ratio can determine the need for additional testing.
Positives with high ratios can be reported
out based upon the screen test positive alone, as long as their is an
accompanying explanation.
We do state this fairly clearly in the
guidelines, that only greater to or equal to 95 percent will be RIBA positive,
and that these patients should be referred on, for further medical evaluations.
Our guidelines also stated that low
positives, or samples with a low signal to cut off ratio would require
additional, most specific testing, due to the fact that most of these are false
positives.
It was our hope that this would limit costs,
while improving the accuracy of reported results, as compared to labs that were
performing no additional testing at all.
So, within our document, we also addressed
implementation. Each laboratory would
need to determine that reflex testing option they would be using, and then
revise any standard operating procedures that they had, to reflect the
algorithm that they chose, as well as define the procedure for reporting
results, and provide an adequate interpretation for these results.
We also believed it was important to educate
staff and customers, as well as to modify the requisition form so that, when
the physician requested, the requisition would clearly state that they would be
obtaining an anti-HCV screen testing, along with a supplemental assay.
So, the implications are that patients and
physicians can reliably interpret results, and that further clinical evaluation
would be limited to true positives.
It would also limit unnecessary medical visits,
as well as psychological stress on patients who did test falsely positive.
Finally, we believed that it would
substantially improve the ability to establish public health surveillance
systems to monitor the effect of prevention and intervention activities.
So, that was all for my presentations. I would like to take any questions, if there
are any questions pertaining to how these guidelines would be utilized in the
laboratory setting.
DR. KLEIN:
I might have missed it, but the high cut off, what percentage of those
would have been NAT positive?
DR. KUHNERT:
I did have a slide that indicated that, and we only looked at that in
comparison to the EIA. We have not done
any testing compared to the CIA. For
the EIA, it depended on the prevalence, but generally, between 80 and 100
percent would be true positives. So, it
was high, but not quite as high as the RIBA assay.
Dr. ALLEN:
For the patients whose sample had a very high signal to cut off ratio,
but they were RIBA negative, were you able to go back and look at additional
specimens on those people, or do re-testing, at least on the initial specimen
to sort of see if that was repeatable, or perhaps due to a laboratory or sample
error in some way?
DR. KUHNERT:
Unfortunately, in most of these populations we weren't able to get an
additional sample. That was not possible, but we did do re-testing on most
everything that we questioned, and generally found that we couldn't necessarily
find a good reason, but the results did remain.
Like I said, we did do the Abbott as well as
the ORTHO assay and, many times, for the EIA, we would follow up with the other
assay as well, just to confirm, with a different platform.
DR. NELSON:
The survey that you did, you asked about supplemental testing, but did
you ask, in that survey, whether labs were reporting signal to cut off ratio,
which is not really a supplemental test?
In other words, I guess that survey was done and then you published the
MMWR.
DR. KUHNERT:
Correct. Actually, we were involved from the outside on those
surveys. We did not actually directly
perform those surveys.
Like you said, at the time, the document was
not published. Many labs were aware of it, especially the state and public
health labs, and that is why we did ask the question, were they performing it
on low signal to cut off ratios.
In the document, we don't recommend when the
result is reported, to report that signal to cut off ratio. We recommend that reflex testing be based
upon it, but not necessarily provide that information to the physician.
DR. NELSON: There have been publications
going back quite a few years, looking at this issue of the signal to cut off.
Those of us doing research, where we can't
afford a RIBA test on a high prevalence population, have been using the signal
to cut off to estimate prevalence and incidence for some time. I am surprised that some labs weren't doing
that as well, prior to 1998.
DR. KUHNERT:
I think, like you said, it was the difference between a research setting
and the clinical setting.
In the clinical setting, it didn't say you
had to do anything else, so it was strictly reported out as the EIA result
alone, and that is really what we found, that most labs were reporting out
that.
Even after the recommendation, that still remains. I think we have made a difference with the
public health laboratories. I am not
sure we have made as much of a difference with the other labs.
DR. NELSON:
Thank you very much. Next is
Dr. Dale Hu, to talk about, I guess, HIV testing.
Agenda Item:
Performance of HIV and HCV Supplemental Assays. Dale J. Hu.
DR. HU:
Thank you, Dr. Nelson, members of BPAC.
This afternoon I have the opportunity to present some data from Dr.
Steve McDougel's lab at CDC, the HIV immunology and diagnostics branch.
While Steve, unfortunately, could not be here
this afternoon, Dr. Michelle Owen is in the front row and actually performed
the analysis of this study, and will be available to provide any detailed
responses to questions.
Although there have been a number of national
and international guidelines for HIV testing, what is the rationale for
considering alternatives to western blot?
Well, first of all, there is the question of
cost and efficiency. Western blots are generally much more expensive and also,
in the international setting, especially in resource limited settings,
sequential EIAs have been effectively used.
The second area is about western blot
availability, and that is another consideration, as with the nucleic acid
testing, the issue of accuracy.
Finally, what is very important is to reduce or eliminate indeterminant
western blots.
The purpose of the CDC alternative algorithm
study was to evaluate the possibility of either using sequential EIAs or NAT
testing as an alternative to western blot in the HIV diagnostic or surveillance
setting.
For this evaluation, we obtained specimens
from the following sources. We had
1,000 specimens from Boston Biomedica from mainly U.S. sources.
Approximately half of these tested positive
by either the Abbott or Genetic Systems 1, 2.
There were also an additional 62 specimens from non-U.S. sources, and
most of these were non-subtype B.
Finally, there were 96 specimens from a blood
bank study from Cameroon. Again, all of
these were non-subtype B. These were units that were discarded for screening
positive on either HIV, HBV, HCV. All
these samples were collected and processed according to the local condition.
For the testing, all these specimens were
tested with six different EIAs, two rapid tests, and three NAT. I will explain those on the subsequent
slide.
Any of the specimens that were found reactive
by the above tests were then tested by western blot. The sample was considered positive if it was western blot
positive, which is the convention, and it was considered negative if either it
was negative by all of the 11 tests or it was western blot negative.
All these tests were performed by trained
laboratory personnel and certified for Gen-Probe and AmpliScreen NAT testing.
Here is a list of the six EIAs, the two rapid
tests, the two licensed NATs, and one in-house NAT. Then, for the western blot,
the Cambridge was used to test the ones from Boston Biomedica, and Biorad was
used to test the ones from Cameroon.
When compared to western blot positive, this
was the single test sensitivity and specificity for each of these tests.
As you can see, the Biorad -- among the six
EIAs, the Biorad plus 0 and the Vironostika plus 0 had the highest
sensitivities. Among the NAT tests,
Genprobe had the highest sensitivity and specificity.
Taking the Genprobe alone, and comparing that
to western blot positive, western blot negative, and western blot
indeterminant, we had concordant results in 97 percent, or a sensitivity of
97.3 percent.
We had 17 individuals that were NAT negative
and western blot positive. I will go into these in more detail. We also had a
number of 25 western blot indeterminants, but I won't go into this, as Dr.
Stramer will describe the issue of western blot indeterminants.
The other issue that I want to bring up right
now is that one of the limitations of our evaluation is that we didn't have
follow up data for these specimens, or the individuals that contributed to
these specimens. For that reason, we
don't know the actual status of these western blot indeterminants.
Here we have a line listing of those 17
discordant specimens, namely, Genprobe negative and Western Blot positive. As you can see, all 17 of these, with the
exception of one in-house NAT were negative.
Then we looked at the six EIAs. As you can see -- probably you can't see
from the back of the room -- but most of these have fairly high signal to cut
off ratios.
I also want to mention that four of these 17
specimens are non-subtype B. These are
indicated in blue and in the asterisks.
One of them was from India. The
other three were from the Cameroon blood bank study.
If we look at the western blot patterns, we
can see that all of these specimens have a number of bands and would be defined
as positive, or true positive.
In the next slide, we decided to take the two
most sensitive EIAs, the Biorad plus cell and the Virinostic plus cell.
Obviously, there is a large number of
different combinations of two tests, but these two are shown for illustration.
Again, we have the three columns of western
blot positive, western blot negative, and western blot indeterminant.
As you can see, the sensitivity of the two
different EIAs sequentially, was 99.8 percent, and the specificity was 99.4
percent.
Finally, we took the combination of looking
at one of the EIAs, followed by the Genprobe NAT. Again, we can see, in the three columns, that there was a 97.3
percent sensitivity among those that were concordant, NAT positive, western blot
positive, or EIA NAT positive, western blot positive. Again, these are the same 17 individuals that I showed the line
listings earlier.
In summary, the EIA plus NAT had a
sensitivity of 97.3 percent, and the discordant samples, as shown by the two
line listings, had high signal to cut off ratios, and positive western blot
patterns.
Overall summary of those three tables that I
showed, NAT by itself, which obviously you would not do, had a sensitivity of
97.3 percent, specificity of 99.6 percent.
The dual EIA, 99.8 percent sensitivity, 100
percent specificity. Then, EIA followed by NAT, 97.3 percent sensitivity, 100
percent specificity.
I just want to conclude by re-emphasizing
some of the caveats of this evaluation, or some of the limitations. As I mentioned earlier, there were no follow
up samples for any of these, especially for the discordant specimens.
We had limited demographic and epidemiology
data. The collection and processing and
storage of the specimens was done according to whatever setting they were
collected. So, some of them may have been out for a while.
In this case, we do know that there was only
one freeze style cycle prior to NAT testing, and one to two freeze cycles prior
to serologic testing.
Finally, those discordant, western blot
positive, NAT negative specimens, we wouldn't consider these as necessarily
that uncommon in cases where we have very low viral copy number, such as very
early in an infection, or being on antiretroviral therapy, in which case we
doubt very many of these individuals were on antiretroviral therapy or, if they
happened to be slow progressors or long term non-progressors.
Also, there are similar reports in other
settings. As outlined earlier, the
positive predictive value of a positive test will be determined by the
prevalence.
Dr. Bernie Branson from CDC is present as
well. He actually has done a study in collection with the Department of
Defense, where they looked at over 570,000 Department of Defense beneficiaries,
and I think it is over 1,300 that were initially reactive by EIA. So, if Bernie wants to comment on that,
Bernie is also available. Any
questions?
DR. NELSON:
What was the limit of the NAT tests that were done? Is it 500 copies or lower, that were used in
this study?
DR. HU:
I believe it was 500 copies.
DR. STRAMER:
Ten.
DR. ALLEN:
I am sorry, perhaps I missed it.
The western blots indeterminants, how were those handled, since you were
using the western blot as the standard here?
In other words, you had a number that were
western blot indeterminant. Most of
them were NAT negative. That seems --
the indeterminants seem to be one of the big limitations of the western blot,
other than the laboratory technique itself.
Does that create a problem when you are trying to come up with a
definitive answer?
DR. HU:
Actually, I am going to defer that question to Dr. Alben(?), if I can.
DR. ALBEN:
Yes, that definitely is a problem. Unfortunately, because of the way the
study was set up, we can't go back and find out what the true status is of
those people who are indeterminant.
That is the major weakness of what we have done.
DR. HU:
I don't know if that answered your question.
DR. EPSTEIN:
Do you have peripheral blood lymphocyte cell palette that you could
probe with NAT?
DR. HU:
I actually didn't do this study, and I don't believe we did.
Agenda Item:
Supplemental Testing for HIV HCV.
Susan L. Stramer.
DR. STRAMER:
I am going to review both HIV and HCV supplemental testing algorithms,
the way we do them today, and some options for the future.
Today, HIV and HCV confirmatory algorithms
utilize immunoassays. The HIV-1 uses the western blot, as we have just heard
about, which contains electrophoresed, whole viral lysate. HCV uses RIB, which contains painted
recombinant HCV antigens.
As has already been alluded to, there are
many issues with supplemental assays, most significant of which is poor
performance.
As I will show you, in many cases we have
unreadable tests, uninterpretable, or invalid.
The supplemental tests generate both false positive and false negative
results.
We also have high rates of indeterminants
which, to a donor and counseling, means a no test basically, because we tell
them you are neither positive nor
negative. These are most frequently given to healthy individuals.
Other issues include high cost, inconsistent
availability, as has already been highlighted for HIV. Then, a question that we ask is, is all the
testing necessary, or are we performing redundant testing. Lastly, can
alternate algorithms be validated. That
is my job, is to show you alternate algorithms.
In summary, the types of algorithms that I am
going to review for HCV, are the use of HCV NAT. We already perform HCV, and HCV NAT is a screening test for all donations. So, it is already there.
We have integrated NAT results into our donor
counseling messages, and the sensitivity and specificity are both high relative
to RIBA, even though we are only doing mini-pool testing.
As already has been discussed by the CDC, the
use of NAT in lieu of RIBA, if NAT reactive, is already recommended by the CDC.
A second alternate that we looked at is that,
since we already have NAT results and EIA results, what would be the benefit of
adding signal to cut off ratio evaluation to the algorithm, to see if the
number of RIBA results could be further reduced.
For HIV, I did the same thing, looking at NAT
or looking at signal to cut off ratios.
Secondly -- and hopefully this will be the one that you all approve or
discuss the scientific merits of -- if a donor is NAT reactive, we would
perform no further testing.
If the donor is HIV non-reactive, we would
apply that sample to what is called the dual EIA algorithm, where we would use
a second EIA, or if it scored an EIA reactive -- that is, reactive by EIA one,
which is the test of record, but non-reactive by EIA two, would not be further
tested. These individuals are not HIV
infected. A second screening test could
not demonstrate reactivity.
Now, the feasibility of doing this for HIV --
that is, why am I presenting this HIV and not HCV -- is because the antibody
tests for HCV that are licensed use the same recombinant antigens, for the most
part, the same assay formats. Therefore,
they do have overlapping populations of false positives.
In contrast, for HIV, licensed screening
tests use very different antigens, combinations of viral lysate recombinants
and peptides, and the populations of false positives are unique.
I would also like to say, regarding the dual
EIA algorithms, that the EIAs that we use for screening undergo much more
stringent validations than do the supplemental tests, and they have gone
through a number of improvements over the years, which has not occurred for the
supplemental tests. What are the issues
if we change our algorithms? Would we
misclassify donors?
So, the current algorithms, we feel pretty
comfortable with, in that we have a lot of information that we are able to
provide specific counseling messages to.
If we have discordance by these several tasks, we can further
investigate with donor follow up.
Secondly, as mentioned by Dr. Biswas, the
kits will require labeling for their intended use, and probably changes to the
CFR.
21 CFR 61040(e) cites that you must further
test each donation, including autologous donations found to be reactive by a
screening test.
Whenever a supplemental -- that is,
additional -- more specific test, has been approved for such use by FDA. Well,
in fact, the use of more specific may be a misnomer, according to the data that
I will show you and Dr. Busch will show you.
So, for those of you who can see this, this
is our HCV current testing algorithm for the Red Cross for which data I am
showing you.
It spans the period of time from September 8,
1999 to the end of June 2003. So, it is
almost four years of data.
We generated, from 25.6 million donations,
34,656 repeat reactives. Just to show
you the cells that are of most importance, here if you are RIBA negative, NAT
non-reactive, that is a large proportion of our population, 34 percent.
Here we have the other large population which
are RIBA positive, reactive individually by NAT, and these would be considered
HIV infected. I put question marks here
with the other categories, which represents discordant cells.
Now, if we take that same population and say,
what is the benefit of, first, culling out those that are NAT reactive, and
only performing RIBA on those that are non-reactive, here we have been able,
then, to be able to do RIBAs on about 40 percent of our donations.
So, that is, in this population, 13,407, for
which no further testing is required, and that has a positive predictive value,
then, of 98.4 percent. That is
reasonably high.
If you then look at the other arm, where we
do have to perform RIBA, there are relatively small numbers. Only 15.6 percent, then, of this population
represents RIBA positivity.
Putting this all together, because we have
RIBA positives here that probably represent resolved infection, we have an
overall sensitivity of about 80 percent, but recognizing that all of these that
are RIBA positive are potentially low level NAT positives that were not
detected here, that would have the benefit of a RIBA.
Now, taking that same algorithm, and just,
instead of adding RIBA immediately to the NAT non-reactives, we insert a review
of the S to CO values.
We still have the same 40 percent of the
population who wouldn't require further testing, because they are NAT
reactive. That, again, was the 98.4
percent positive predictive value.
Now, if you look at, of those samples, how
many had high signal to cut off ratios, which I believe was the question that
was asked, 98.8 percent of these had a high S to CO, and were RIBA
positive. So, that is a 99.8 percent
sensitivity.
Now, going over here to the non-reactives, if
we review S to CO values, it doesn't really benefit us because, of 21,000
samples, we only have a quarter of them that would not require RIBA based on a
high signal to cut off ratio and, of those, only about half of those are RIBA
positive.
So, these other samples that have high signal
to cut off ratios, they may also represent resolving infection or false
positives.
Right now, looking at this algorithm, it only
gives us 55.8 percent positive predictive value and, if you combine the two
sets of positives, it does give us a relatively good sensitivity, though, with
83 percent. It still doesn't really
have an advantage.
Now, if you combine all of our current
results together -- and I didn't dwell on a lot of the individual pieces of
data on the flow diagram, but I will go into more detail here -- these are all
the samples that I just presented, 34,656, integrating the RIBA result with their
NAT result.
So, there are these samples here. About half of them are RIBA positive, and
about 80 percent of the RIBA positives are also NAT reactive.
One very important item here -- and you can
see these tiny numbers here with the three asterisks -- we have a subset of
samples that are classified as RIBA indeterminant, and I believe that is 15 in
this study population, that really are RIBA positive samples.
Based on the fact that they still have
carrier protein reactivity on the blot -- that is, the way the recombinant
antigens are produced with a carrier protein -- because that reactivity is also
exhibited on the RIBA strip, these are erroneously called indeterminant. So, I have given both sets of numbers.
Leaving that caveat aside, if we talk about
the data, here we have about one to two percent that score NAT reactive.
If we ask, of these NAT reactive samples, how
many are truly NAT reactive -- that is, how many discriminate and how many are
PCR positive -- it is 80 percent of this population and 32 percent of this
population.
I have included all NAT reactives in these
tables because we still counsel all NAT reactives, whether they discriminate or
not, and this is part o four HCV subset.
Just recognizing that 80 percent of these are truly positive, and about
30 percent of these are positive.
Then we are left with this discordant cell
which are RIBA positive and NAT non-reactive.
What is the significance of those?
Are they false positive RIBAs, false positive NATs, or individuals who
have resolved infection?
Regarding whether they truly are NAT reactive
or not, we have taken a subset of those samples, about two thirds of those
samples, and re-tested them individually.
What these three cells show you is how the
samples were selected. They were all RIBA positive, again, and NAT negative
when they were tested individually.
They were either screened as individual
samples originally, screened in pools on these two cells, and their results
were either NAT negative as a need sample, NAT negative after a pool was
resolved, or pool negative without individual NAT testing being done.
Recognizing that there is only one sample
here, let's focus on these two cells.
Interestingly, whether the samples were neat NAT negative or pool NAT
negative, when we re-tested these samples, about two percent of both
populations demonstrated NAT reactivity simply by just re-testing. Our algorithm was re-test twice, and they
were considered positive if one of two tests scored positive.
The viral loads in these samples, 70 percent
of them, have low viral loads. Others had high viral loads and, in fact, one
had 5.2 million copies per ml. We don't
have an explanation for this, but we know it happens with HCV.
Looking at the signal to cut off ratio, now,
with all of the NAT reactive samples, what you see is that, for the NAT
positives, very high signal to cut off ratios.
98.9 percent of the RIBA positive NAT
reactives have an S to CO ratio of greater than or equal to 3.8, the value that
CDC used.
Here, for indeterminants and negatives, we
see a distribution of S to COs, but remember that these contained 80 percent
that were truly NAT reactive, which probably represents the high signal to cut
off ratio and, here, about 30 percent which, again, are probably the higher S
to COs, with more of the false positives dropping off at the lower signal to
cut off ratios.
These are the NAT non-reactive. What is important in this slide, showing the
same thing for RIBA negative, RIBA indeterminant and RIBA positive, here 87.8
percent of the RIBA negatives are indeterminants that were NAT non-reactive,
had a low S to CO. So, S to COs are
really beneficial in combination with the other test results for donor
counseling.
So, in summary for HCV, the use of NAT is the
first step of the supplemental testing algorithm. It will reduce the number of
RIBA tests performed by approximately 40 percent.
In HCV NAT reactive samples, even using
pooled NAT for screening, it had an overall sensitivity of 80 percent. Those
not detected by NAT in this population will be tested by RIBA, as we do today.
98.4 percent of the NAT reactives were RIBA
positive. That is a positive predictive
value, again, of 98.4 percent of these, and the remainder, or small percent of
NAT reactive samples, likely are representing early seroconversion, which are
the RIBA indeterminants or negatives.
The use of a high signal to cut off ratio --
that is, 3.8 -- can be applied following separation of the repeat reactive
samples into NAT reactives and NAT non-reactives.
However, they didn't provide as much benefit,
because they would only eliminate about 23 percent of RIBAs performed, with
relatively poor performance, a positive predictive value of 55.8 percent.
In the CDC population, the stratification was
done a little bit differently. So, all comers are in there. They are not separated by NAT negative or
NAT positive. So, the sensitivity and PPV are much higher.
As I did say, one benefit of the high signal
to cut off ratio, or using the signal to cut off ratio, is it is very
beneficial for donor counseling.
Again, those with a high signal to cut off
ratio that were RIBA positive and NAT reactive, 99 percent of them had high signal
to cut off ratios and, similarly, a similar proportion of NAT non-reactive RIBA
negative or indeterminants had low signal to cut off ratios.
Now, I am going to go through the same type
of data for HIV. The last time we
talked about HIV and western blots was at the March 16, 2000 BPAC, where we
tried to eliminate the interpretation of reading of non-viral bands. We were not successful in doing that.
The definition here of a non-viral band is
provided per one of the package inserts for western blots. Unfortunately, anyone who doesn't score
positive or negative on a blot is given the determination of indeterminant, and
that includes anyone with a non-viral banding pattern.
In that BPAC, I showed about 50 percent of
all the samples that are repeat reactive for HIV are indeterminant. Of those that are indeterminant, two thirds
do have some viral banding, but there is a large percent that either will be
scored as indeterminant because of non-viral bands or because of background.
If there is background on the strip and you
can't read the area of the strip, we have to interpret that strip as
indeterminant.
This shows you an example of a p70 band. It is a very clear band and difficult to
miss. Here you have background. So, this blot would have to be scored as
indeterminant.
Here you have more blots with indeterminant
clearly in the area of 120, 160. There
is background here. So, you can't read
through that.
I show this -- I don't know if you can see
this all the way through -- but the end of the gel scores as a band here on
every single strip. Because that is a
band on a licensed, valid test, every donor on this run had a score of
indeterminant.
Now, looking at the same 25 million donations
screened over a four-year period of time, we had 17,090 repeat reactives.
Looking at the breakdown, how many were
western blot negative, NAT negative. That is a big bolus of our population, 44
percent.
Looking at those who were western blot
indeterminant, HIV non-reactive, again, NAT negative. Here is the other large population, again, hovering around 50
percent. So, we are seeing here the vast
majority of our population not HIV infected.
Of those western blot positive, we only have
about five percent, and they divide into the majority that are RNA positive,
with a minority here, and this 59 that I am going to bring up repeatedly, 59
contains western blot positives that are RNA negative, but about two thirds of
these are probably false positive western blots based on a myriad of repeat
testing for RNA and donor follow up.
Inserting NAT reactivity to say, well, how
many, based on NAT reactivity, could we avoid, and then only perform the
western blot on the NAT negative, we only save, as I said in the previous
slide, five percent of western blots.
So, just dividing the population into NAT
reactive versus NAT non-reactive, and saying we will do western blots on the
NAT non-reactives doesn't really help, because we are only eliminating five
percent of the population.
Now, clearly, 90 percent of those are western
blot positive. So, that is a good positive predictive value and, overall, the
algorithm as high sensitivity. It
doesn't help with the western blot problem.
It further complicates if you add the signal
to cut off ratio into this equation. This is the same population over here,
again, about 90 percent positive predictive value and, of those, 99.6 percent
of the western blot positive NAT reactive samples have high signal to cut off
ratios. So, everything fits together
nicely.
If you come over here, the NAT non-reactive
samples, if you first review signal to cut off ratios, you are only going to
get less than two percent that you are eliminating by using a high S to CO
here.
We used 15 in a similar way that CDC
validated in S to CO 3.8. Based on
positive predictive value and sensitivity, we chose 15 to do this
evaluation. The bottom line here is poor
positive predictive value and overall poor sensitivity.
Again, integrating all of the results
together, we had 17,090 repeat reactives.
Only about five percent of those were western blot positives. Of the western blot positives, 90 percent
being NAT reactive.
Here we have the population of 59 that were
western blot positive, NAT non-reactive, and I am going to talk more about
those.
First, go to these same two cells that I
highlighted for HCV, the indeteminants and the negatives. With HCV, I told you, about 80 percent of
these were truly RNA positive, and about 30 percent of these were.
Well, for HIV, only six samples -- that is
less than .05 percent of the total -- were RNA positive here, and none of these
were truly RNA positive.
Really, the message for indeterminants and
negatives by HIV western blots that are RNA multiplex reactive, that don't
further discriminate is really these are not infected, as well as the vast
majority of these being -- well, all of these not being infected, the vast
majority of indeterminants and negatives not being infected.
So, of HIV western blot negative or
indeterminant, only six of the total 16,362, or about one in 127,000, were
truly infected with HIV.
Now, looking a little bit more at this 59, I
just show some examples of line listings of these. You can clearly see, other
than I highlighted so there are two colors here, here we have the ones that are
western blot false positives.
This is the test of record whether they were
screened in a pool or neat. Their signal to cut off ratio with HIV, so we have
high S to COs versus low S to COs. We
had weak band patterns that frequently lacked p31, and frequently or only one
gene product versus total banding.
Then, HIV PCR was repeated and, in several
cases of the 59, we did get four that did have low level virus when we repeated
them.
The majority of those, even of those that we
think are positive, we couldn't cull any HIV RNA out of. So, these are either
people perhaps on antiretroviral therapies, long term non-progressors, or
people with extremely low viral loads.
This shows the same type of data. So, what we have seen so far in western blot
failures are false negatives. I mention only about one in 2,700 were NAT
confirmed positive or western blot indeterminants or negatives.
I started to discuss western blot false
positives. Of 59 western blot
positives, NAT non-reactive, 37 had low S to CO values, incomplete band
patterns, repeat NAT non-reactive, and follow up demonstrating lack of HIV
infection. So, those are false positive.
A net rate in our population is about one in
700,000. In contrast, 22 did have high
signal to cut off ratios, complete band patterns, including p31, but only four
of those with RNA very low level positives.
These are the signal to cut off rate distributions. The only ones even in NAT reactive samples,
considering that all but six of these were truly positive, 99.6 of these
western blot positive NAT reactives had S to COs greater than or equal to 15
Conversely, in the NAT non-reactive
populations, these are all uninfected individuals. These that were western blot
positive distribute into two groups that I told you about, those with true
western blot positive, and those with false positives.
Of these two cells here, 98.5 percent of
negatives and indeterminants were non-reactive with an S to CO of less than 15.
So, the use of NAT is the first step in the
supplemental test algorithm will reduce the amount of HIV western blots
performed by only five percent.
NAT reactive samples, using the testing
methods we used today, relative to the western blot, has high sensitivity, but
those not detected immediately by western blot or by NAT, I should say, would
be detected by western blot, but the trouble is we wouldn't be eliminating
enough of the western blots, and we still have issues of false positive western
blots.
The only use of the high S to CO for HIV,
just like with HCV, is for donor counseling.
SO, let's just review quickly the last option, which is the dual EIA
algorithm, where NAT non-reactives, rather than evaluating signal to cut off
ratios, we would test them by a second EIA.
The feasibility is based on what I mentioned
earlier. If two assays with comparable sensitivity are composed of differing
rare reagents and have different formats, the false positive population should
have limited cross over.
The more unique the test, the greater the
separation of false positives. We have
been using this algorithm successfully for HTLV, where there is no licensed,
confirmatory test, to eliminate about 60 percent of samples that need further
testing.
So, we qualified this algorithm with the two
licensed tests at the time that were available. That is the genetic systems test, the PEIA, and the Abbott HIV-1,
2 test.
We switched samples. That is, we looked at both the collaborative
study between BSL, that started with genetic systems, and then went to Abbott.
Then we took the Abbott samples and reflexed onto genetic systems testing.
The populations were the same time period,
2000 through March 31, 2002. We had a
total of 7,884 samples for the evaluation.
All samples were tested by the Genprobe NAT
Method in pools of 16, and all the second EIA testing was performed centrally
at Blood Systems.
So, this is the results, now, of looking at
the genetics system screen of EIA 1.
So, if you split the sample into western blot positive and negative and
then determine it, look at how many, then, were non-reactive or reactive by
second EIA, and then ask the question, how many of those were RNA positive, here
are the non-reactives with zero, zero, zero, zero.
We don't see any RNA positives until we get
to concordant EIA repeat reactives that are western blot positive.
We only had one sample here, of 80 total,
that was RNA negative, and that one sample did have a very high EIA S to CO on
both EIAs, and did have all nine bands on western blot.
Now, looking at the other side of the house,
where Abbott was the selection criteria, and then we reflexed onto Genetic
Systems, here are the western blot negatives, indeterminants, positives, the
results of Genetics System screening, and then the results of NAT testing.
Here we have, again, in the western blot
negative category, whether they were concordant or discordant EIA reactive,
zero RNA positives, zero, the western blot indeterminants, zero.
Here we had one western blot indeterminant
sample that was concordant, EIA repeat reactive. So, it would have been selected, and also it was RNA
positive. The indeterminant was p24
weakly and GP160.
Here, if we go now to the western blot
positives that are concordant EIA reactive, there were 13 that were EIA
reactive but RNA negative, and I will show you a line listing of those.
Here represent the false positive blots that
we select out with the use of this EIA that is the envelope enriched
samples. So, we had 16 of those.
So, these are first, the 13 that were
concordant EIA reactive, NAT non-reactive, and western blot positive. With the exception of three, they all have
very high signal to cut off ratios, and relatively full band width and
relatively full banding patterns.
We don't have follow up samples on these
three samples, so their status is unknown.
However, they would have been selected as repeat reactive by either EIA.
These are now the 16 samples that were
classified as western blot false positives -- Genetic Systems non-reactive, NAT
non-reactive. When we retested them by NAT, they were non-reactive, and follow
up subsequent to that, one individual was in an HIV vaccine trial. I don't know why they were a blood donor.
This individual, we don't have that
documentation from, and we didn't have follow up but, when tested by the Roche
assay, NGI, and TMA again, each time they were RNA negative.
So, we conclude that all of these would come
from RNA non-reactive individuals. So,
if we put all of this data together in a workable algorithm, which Dr. Busch
will show as far as an option, we would do NAT first.
These are NAT reactives versus NAT
non-reactives. NAT reactives would undergo no further testing, 316 of these 317
were western blot positive. The one western blot indeterminant was still
concordant EIA reactive, and RNA reactive.
Here we then have the vast majority of
samples that would undergo the second EIA.
We would cull out the repeat reactives for western blot testing.
These were the 13 and one that were western
blots, most of them strongly positive.
Then this site here, 94.5 percent that would undergo no further testing,
we still have the discussion about the 16 false positive western blots.
So, if we applied an algorithm like that, we
would, in fact, eliminate most of those false positive western blots.
So, this is my last slide. The feasibility of NAT combined with the dual
EIA algorithm for HIV confirmation was demonstrated.
The sensitivity using NAT as the gold
standard was 100 percent, with this confidence interval. Specificity was 98.4 percent.
We were able to eliminate 98.5 percent of the
western blots performed, which then eliminated 98.6 percent of the
indeterminant results.
The majority of western blot false positive
results, which are the sticky issue in the algorithm, were selected by the use
of one particular EIA, were eliminated.
Then, changes to EIA's more sensitive or
specific versions, as history shows us that we do with new testing license,
should not require extensive validations.
This is a bullet that Roger Dodd made me put
into my presentation. Western blot is
shown to be of little, if any, value.
Thank you for your attention.
DR. NELSON:
Any comments or questions?
DR. EPSTEIN:
For the dual EIA non-reactive western blot positive, NAT non-reactive,
you have argued that those are false positive blots.
We have seen elsewhere in the data that you
can, in fact, have false negative NAT.
So, why are you sure they are false positive blots as opposed to low
level infections?
DR. STRAMER:
The ones that were the opposite sides of the question, the RNA positives
-- one side of the cell was EIA concordant, and those EIA concordant samples,
that may have had weak banding patterns would have been detected because they
were concordant by both EIAs.
They had high signal to cut off ratios, were
detected strongly by both EIAs, even though -- and most of them, the vast
majority, had nine bands on western blots.
There were three that I can't account for,
but those three both were concordant by EIA. The 13 that were western blot
positive, but were discordant by EIA and only reacted by the added EIA, in
follow up we couldn't demonstrate any HIV when RNA and antibody testing was
repeated.
In the index sample, when we repeated NAT,
they were RNA negative by TMA and by NGI.
So, regardless of whether we retest the index sample or we have follow
up samples from those 16, we cannot demonstrate any persistent, or any evidence
of HIV infection. That only comes out
of a subset of 25.6 million donations.
I mean, those are the worst case samples.
Agenda Item:
Supplemental Testing for HIV and HCV.
Michael Busch.
DR. BUSCH:
I am representing Blood Systems. Sally Cagliotti is here, who runs the
laboratory where these data were all generated.
I wanted to actually start by just showing a
little bit of data that is in press, a paper from the Reds group, and Steve
Kleinman, who is here, is the lead author on this paper, to just emphasize the
impact that these notifications can have on donors.
In this study, we sent letters, or
questionnaires, about the impact of notification to a fairly large number,
about 1,500 donors who had been notified in the prior six months about
reactivity in the donor test screening assays.
Just a couple of tidbits of data. We were
looking here at the question of, were the donors confused by the notifications.
These donors had received routine
notifications from Red Cross or Blood Systems, Oklahoma Blood Institute. You can see that it is particularly emphasizing
here that the donors that are getting these indeterminant and false positive or
confirmation negative results, half of these donors indicate that they are very
confused by these notification messages.
Whether these donors were upset at these
notifications? Again, understandably,
donors who were being told they were infected with these viruses are upset, but
the important message here is that the donors who are getting these
indeterminant and negative notification messages are equally upset, about half
of them.
Many of these donors seek subsequent testing.
So, they drive costs within the health care system. So, I think minimizing false positive notifications from donor
screening is important.
As you are seeing for, particularly, the
numbers from Red Cross, which you could double to get the annual rates, we are
talking about tens of thousands of donors who have been notified about these
false positive test results.
So, I think we have struggled now for a
decade and a half with HIV and then HCV, these tests in place, and these
contributory assays that leave us with large numbers of indeterminant and blot
negative, non-confirmed donors.
Fortunately, we now have NAT in place for
routine screening, but it also offers us, as you have seen, a lot of
information that could be better used to counsel these EIA reactive donors.
What I am walk through is the data from Blood
Systems, and then close with some very simple algorithms. Sue went through a
lot of data in the context of these algorithms.
I think, when you boil it all down, I think
it ends up being very simple recommendations, and we can really take advantage
of this NAT testing to better define the status of these donors for
notification purposes.
For example, RIBA positive donors, who are
RNA negative, could be counseled that they probably have resolved, if they are
RNA positive, persistent infection, and reassure the vast majority of donors,
who are negative on the RNA assays.
As she also indicated, the availability of
the NAT data on routine screening could actually reduce the costs and the
complexity of the confirmatory testing, particularly with respect to RIBA and
the potential alternate use of the EIA algorithm.
Then, as we heard earlier today from Paul,
the NAT data, I think, has allowed FDA to look at reinstatement a little more
comfortably, in terms of a negative RNA plus a negative serologic test on
donors, is making them comfortable reinstating donors with indeterminant or,
for example, false positive p24 antigen results.
So, the availability of routine NAT has
really opened up the paradigms around reinstatement as well as notification.
Similar to what Sue showed, data from blood
systems correlating for HIV repeat reactive donors, the western blot and the
NAT data, so this is about 6,000 repeat reactive donors from over seven million
donations.
What you can see here, what I have done,
unlike Sue, is to back out the donors who are reactive on a multiplex assay
day, but negative on a discriminatory, are not shown here, because those would
be identified.
If you are running your routine parallel
serology and NAT, if you have a donation that is multiplex reactive, you
immediately do the discriminatory. So,
you know whether or not this was truly related to HIV or not.
So, in this case, if we focus on the western
blot positive donors, you can see, of 286 western blot positive donors, 93
percent of them had reactivity observed by the discriminatory assay.
There were 18 that were western blot
positive, who had tested negative on the mini pool NAT assay, and we will look
at those in a little bit more detail.
As footnoted here, nine of these 18 donors,
who were HIV blot positive, but negative on mini pool NAT, were autologous
donors who were likely known HIV infected donors, and allowed to give
repeatedly. So, they were not
allogeneic donors.
We will get into the detail on the
others. One of them was a false
positive, and the others were low viral load cases, as we have heard about.
We had two donors over about 2,000 who had
indeterminant bloods, who were viremic and both of those, as I will show you,
had patterns that were suggested of early seroconversion. None of the donors who were blot negative
had positive RNA.
Like Sue, you have these sort of line
listings, showing the signal to cut off.
This is the 18 samples that we had identified that were classified as
blot positive, but had scored negative on mini pool NAT screening.
When we look at the banding patterns,
virtually all of these are full band patterns.
So, virtually every viral antigen is lighting up.
There is one exception which is just like the
one Sue talked about, a 160, 24 only case, a classic, what we call, false
positive western blot.
There have been several papers published from
our group, in red, that have really characterized these false positive blot
cases through follow up, proven they are non-infected.
You can actually block the reactivity to the
envelope protein with a very restricted, non-specific epitope. So, we are convinced that these donors who
have negative RNA and these very minimal blot patterns, which wouldn't have
been called positive back 15 years ago -- the original blot criteria required
three gene products, and the revision of the criteria to requiring only
envelope, or envelope and gag, has allowed these false positives to creep into
the system.
So, in the case of HIV, the majority of the
people who were blot positive, but negative by routine mini pool NAT are
infected people with very low viral load, but one can have these false positive
blots as well.
These are the two cases who were
indeterminant by western blot but NAT positive. You can see the second case has a 24, 255, 120, 160, but none of
the intensities were too low to score all these bands as positive. The other case had a strong p24 band. So, these were probably donors in early
seroconversion. So, the RNA was
probably correct.
Looking at the signal to cut off ratios, you
can see -- and this is a sequential group of 411 over a shorter period where we
derived the screening EIA S to C data.
The people that are blot positive and viremic
are all high level S to C. There were only a couple of cases of blot positive,
NAT negative. These were not the false
positive patterns, and these people had similar high S to Cs.
I think the important message here is that
the vast majority of the donors who were EIA reactive, and either blot negative
or blot indeterminant, had very low S to C ratios.
So, not only can we reassure these donors
that they are not infected, based on negative RNA data, but there is a very
high probability that they will be reinstatable on subsequent donations.
Their original reactivity was just at the cut
off. So, even with that same screening
test six months later, they are very likely to be negative and
reinstatable. Certainly, if you change
assays over time, these donors would all be able to be reinstated.
Just one slide. Mike Strong sent me a few slides from his blood center, and I am
not going to go into them in detail.
I think the important point here is that his
center is using different screening assays, and they are using the Roche NAT
system.
The data you have seen from the Red Cross and
from Blood Systems that I am presenting are using the GenProbe System.
I just want to emphasize that the
observations are completely consistent, whether you use different screening
EIAs or different RNA assays.
So, here they also have a small fraction of
their lot positives that are negative by mini pool NAT, and a small number of
indeterminants who are viremia, and picked up in early seroconversion.
Moving on to hepatitis C, the same kind of
correlation table. So, we have got
about 12,000 EIA repeat reactive donations, here screened with the ORTHO 3.0
EIA, and the NAT results are the routine mini pool screening, resolution,
discriminatory testing, as defined in the GenProbe algorithms.
You can see here, virtually identical to
Sue's data, that just correlating the RIBA and the NAT, that if the person was
serologically confirmed by RIBA, about 80 percent of those donations are
viremia, as detected by mini pool NAT with resolution to the discriminatory
assay at the single sample level.
There are about 20 percent of HCV confirmed
antibody positive people who are negative on RNA by mini pool NAT.
As we can see, the vast majority of these
have resolved infection. Over time, over decades, they will serorevert their
RIBA and their serology, but we will talk about those in a minute, the ones
that were RIBA positive but NAT negative.
We did pick up a number of people who were
indeterminant by RIBA, but had RNA, and I will walk through these in detail.
They kind of sort into several groups. A subset of these are actually positives,
with all the bands in RIBA, but were called indeterminant because of this
control band, the SOD band.
The others tend to be very high reactivity to
selected viral antigens. So, these are
truly infected people where the RNA result was right, and they are being called
indeterminant due to the incomplete seroreactivity on that assay.
Then there were six donors who were RIBA negative
who were viremic. Again, these donors, as I will show you also, have weak band
patterns on RIBA and the RNA results are actually the correct results.
Just this issue of donors who are -- Sue
addressed this as well -- donors who are mini pool -- who are RIBA positive,
but mini pool NAT negative. So, it is
particularly this top group here.
Leslie Tobler at the Blood Center has been
studying these cases, and has initially enrolled 167 donors into a study where
they had their index donation samples re-tested in duplicate by TMA.
These donors are now enrolled into a follow
up study to ask whether these donors have definitely cleared the infection, or
might some of them have low level viremia.
You can see, when subjected to duplicate
testing, that we do find virus at very low levels in six percent of these
donors who were originally considered to have probable resolved infection.
In most of these cases, the reactivity is
extremely low level. So, in that
re-testing, only one of the two duplicate reps was positive for RNA.
Then, on recall of these donors, what we are
finding is that those donors who were reactive, most of them stay low level
reactive, but a few additional donors who were negative even on the duplicate
retest, on follow up, at reactive on replicate retests.
So, some people have very low viral loads,
and the initial donor screening NAT or even serial follow up NAT may fail to
classify these people as low level carriers. So, we will come back to sort of
implications of that.
Then we had one donor who had an
indeterminant pattern, who was negative by mini pool NAT who, on re-testing,
was found to be viremic.
So, then just to walk through this sort of
three slides to sort of walk through these profiles, again, these were the 13
donors who were viremic.
So, they were NAT positive, but they were
called indeterminant. These are the examples where they have every band
lighting up with three and four band intensity. Then they have this SOD reactivity, and this is that carrier
protein, which is co-expressed on these other antigens.
So, if you are reactive for this, you are
required to call the result indeterminant, despite the fact that there is much
higher level intensity reactivity for all these other antigens. These are unquestionably infected people,
where it was really a test interpretation sort of mistake.
Another group, here are 22 of these donors
who were viremic, but classified as indeterminant. You can see, these cases, all of them had four-plus C-22
bands. So, this is a pattern that is
not unusually seen in some people with HCV infection, who just don't mount a
full broad reactivity to all the antigens.
Again, these are all infected donors.
The RNA test was right.
Another group of 14 where they had strong
C-22 bands accompanied by weak bands to other HCV antigens. Again, these are
all infected donors, either with incomplete antibody response or perhaps early
seroconversion.
Finally, there are six donors here who had
RIBA negative results, and yet they were being called viremic by RNA.
As we get to the algorithm, it would be these
that would be the concern because, if you didn't do RIBA in a donor who was EIA
reactive and positive for RNA, you would be concerned that you may have
misclassified some non-infected people as infected.
As you can see here, all these donors had
reactivity on RIBA except for one. So,
our belief is that these are probably, again, truly infected people in early
seroconversion.
Again, the S to C correlations, just to
follow up on the FDA suggestion, similar to Sue's data, the RIBA positives are
all blazing S to Cs that are viremic.
Among the RIBA positives that are not
negative, they really sort into two populations, one that has very high S to C,
and then some outliers that have low S to C.
Whether these are the false positive RIBAs,
or whether they are people with long standing, resolved infections, in whom the
reactivity has waned, is unclear.
Among the donors who were RIBA indeterminant
and NAT positive, you see a wide distribution with a generally higher S to C
ratio.
Most important, again, if you are RIBA
indeterminant, NAT negative, or RIBA negative, NAT negative, the vast majority
of these donors are right near the cut off.
These are the ones that, in Paul Mied's
presentation earlier, become eligible for reinstatement. So, it gives us a good, I think,
anticipation that most of these donors who will be eligible for reinstatement,
will be reinstatable, given that they will probably test negative on the EIA
after six months.
Just the last data is from Mike Strong from
his center. Just to emphasize, at his
center they run the Abbott HCV EIA and the Roche NAT assay, but you are seeing
virtually the same relationships.
They get about 80 percent of the RIBA
positives are viremic, an occasional RIBA indeterminant, and negatives that
have RNA. So, there is really very
similar data coming from the other assays that are widely utilized at blood
centers.
Just to kind of walk through the bottom line
conclusions, and then present the algorithms that have been evolved with
discussions with the blood centers and the Red Cross, I think the key new sort
of opportunity is really to fully incorporate NAT results both into the
notification and counseling messages, and into our supplemental algorithms.
Clearly, we now can tell donors who are both
serologically confirmed and RNA positive, that there is no question they are
infected and they need to be immediately followed up clinically.
Donors who are negative on serologic
supplemental and RNA, we can give them complete reassurance and, now with the
proposed FDA algorithms, these donors can be offered reinstatement.
Donors who are RIBA indeterminant and NAT
negative, probably also uninfected or blot indeterminant. Again, with the new algorithms, the FDA does
allow reinstatement of indeterminant donors.
We can flag problematic cases, and subject
those donor samples or donors to further testing. For example, the donors who are RIBA positive and mini pool NAT
negative, most of these probably are resolved infections, but they could
represent persons with low level viremia who, if you did multiple replicates or
follow up, you would find that RNA.
Some of these theoretically could be false
positive RIBAs. I would argue that this
is not something that donor centers can figure out.
These donors who are RIBA confirmed and NAT
negative really need to be referred to clinicians for serial follow up and
decisions about management of their probably resolved, but potentially low
grade, HCV infections.
If you are western blot positive but had a
negative NAT, these could represent persons with low level viremia, either
naturally or after HART treatment.
They could be cases of false positive western
blots or persons -- and low risk people do volunteer for early phase I vaccine
trials, and we have seen them come in to donor centers.
So, it could be any of these possibilities
again. There is no question that these people will be permanently
deferred. Through follow up, both RNA
and DNA testing and risk factor and history, you can sort this out.
Finally, the RIBA or the western blot
negative or indeterminants that are not positive, in general, I believe most of
these people are truly infected, and that they are probably in evolving
seroconversion, or people who have incomplete serologic patterns.
It is possible that they could be false
positive NATs in parallel with the false reactive EIA, but we really have not
seen this.
Again, these people, because of the positive
NAT reactivity, need to be immediately notified and worked up, and probably
indefinitely deferred.
The argument that Sue made that I fully
support, the elimination of RIBA in situations where we have positive RNA with
a reactive HCV EIA, these persons can be notified that they are infected.
We have two completely independent assays, an
EIA and an RNA assay, that are telling us that they are infected. This is what CDC is recommendation.
All the donor correlation and follow up data
supports that these people are infected.
Clearly, these cases, based on the RNA only data, is sufficient to
trigger look backs for prior donations.
If you are repeat reactive with a negative
mini pool NAT, I think we all agree that RIBA is important for counseling and
look back and, if they are RIBA positive -- if they were RNA negative and now a
RIBA is done and it is positive -- they should be notified of probable resolved
infection but, again, referred for follow up to discriminate whether they might
have a low grade persisting infection.
If the RIBA is negative, with a negative RNA,
these people should be notified as not infected and, the RIBA indeterminants,
probably not infected.
Then the alternate EIA algorithm that Sue
walked through, that basically uses an alternate licensed EIA on repeat
reactive donations and, by combining the EIA and the mini pool NAT data, we can
eliminate a lot of the confusion around western blots, eliminate a lot of
western blots.
Rather than walk through this, let me just go
to the last two slides. Again, these
two slides really sort of boil this all down into what turns out to be a very
simple recommended algorithm.
We have a donor who is HCF repeat reactive on
the antibody assay, and we have already, in our hands, the HCV NAT data.
If that is reactive, then we believe that
they are now RNA positive and were EIA reactive, that no RIBA should be
performed or required, and that these donors should be notified as
infected. That would amount to about 40
percent of all repeat reactive donations, would fall down this trail.
If the RNA is non-reactive by mini pool, then
we believe RIBA Is critical, to sort these EIA repeat reactive, RNA negative
donors, into the positive, negative and indeterminant groups.
You can see that about 15 percent of the
overall donations would fall into this group that is RIBA positive, RNA
negative, probable resolved infection, need to be referred for follow up.
If they are indeterminant, they are probably
not infected and could be considered for reinstatement. Certainly, if they are RIBA negative, they
definitely are not infected and can be reinstated.
For HIV, we have an identical flow. We have the EIA results that are repeat
reactive. In this case, if the RNA is reactive, these donors are almost
certainly infected, and we don't believe it should be required to do any
further testing.
However, it could be optional to perform a
western blot or an alternate EIA on these samples. These only amount to two percent of all donations and, of course,
these are donors that are told they could be HIV infected, immediately referred
for follow up.
So, one could consider it is such a small
fraction and the message is so important that perhaps a western blot is
justified, just to give some extra reassurance that, no question, these donors
are infected before you tell them they are HIV positive.
The vast majority of donations that were
reactive for HIV will be negative for RNA.
In this setting, we strongly feel that the alternate EIA option makes an
enormous amount of sense, to avoid the western blots, and particularly the
problems with the indeterminant notifications.
If the alternate EIA is non-reactive which
is, in our system, 97 percent of all reactive EIAs would run down this trail,
negative RNA, negative alternate EIA.
These people are not infected, could be notified as such, and entered into
a reinstatement protocol.
The small fraction of donors that have a
negative RNA and a reactive alternate EIA would then be subjected to the
western blot HIV-2 testing, and one could consider doing additional testing if
they are western blot positive, to look for low level RNA.
Clearly, again, this is a situation with a
very small fraction of donors who we can focus on and bring these people back
and figure out whether they are infected or not. It really only amounts to a very small number of donors who need
this more aggressive follow up. Thank
you. I will stop there..
DR. NELSON:
Thanks, Mike. That was very clear. It does seem like there is a real
role for the duplicate EIA and the signal to cut off application.
I read a recent paper that really is kind of
an outlier in a way. It is disturbing.
I don't know whether you saw it or not.
The title was Occult Hepatitis C. This was a
group of people that were persistently ALT or enzyme -- that were elevated,
that had both negative EIAs and NAT.
They did NATs on liver biopsies and on PBMCs,
and there were 100 patients studied.
Fifty six of them, they said, had low level positivity.
Obviously, as long as we are screening blood
donors for ALT, this wouldn't be an issue with regard to transfusion, as long
as the ALT is in the algorithm.
What do you think of this? I was concerned about, was some of this a
lab contamination issue or is this a real phenomenon?
DR. BUSCH:
I did see that paper, and there are other papers from good groups
recently on HIV that are finding occult infection. Again, it sort of harks back to 10 or 20 years ago, the whole
mess over ICL.
My personal bias is that these findings are
probably not going to be reproduced. In
this case, the ALT levels were elevated, but low elevated, and would not have
met the blood donor unit discard criteria.
In fact, those of us in blood banking don't
believe ALT should be continued, and FDA never required ALT in this
country. So, it is being disbanded as a
donor screening assay.
Again, certainly in terms of surveillance for
blood transfusion infections, we are not seeing occult donors that are
infecting recipients.
My personal feeling is that we have to look
at that data and probably interpret it as false positivity until it is
corroborated.
Again, you have to look critically at the
selection of the population. These tended to be high risk people who had
persistent elevated ALT.
DR. CHAMBERLAND: Thanks to you and Sue for two really nice presentations. You mentioned specifically, with respect to
the discordant individuals, you mentioned one instance in which Leslie Tobler
was doing a follow up study in which it sounded like people were brought back
for subsequent rebleeds.
It wasn't clear if that was the only
situation, either in your presentation or in the Red Cross data, whether
individuals who were discordant were brought back for specific follow up
testing to see if there had been any evolution or change in their markers.
Secondly, I was just curious if, when, in
Leslie's study, at least, individuals were brought back, if they were
questioned to see if there had been any epidemiologic information that perhaps,
as we know, sometimes donor histories are not as accurate as we would like.
I was just curious if you had some
supplemental information from that perspective as well, that might be helpful.
DR. BUSCH:
I think we have historically done follow up studies on various groups of
these false positives, or indeterminant donors.
For example, in the western blot false positive story, Steve and I are
involved in several studies where we followed up fairly large numbers of these
donors and really proved through follow up testing, as Sue summarized in her
own work with follow up, that these are non-infected people.
The subgroup that Leslie has focused on are
donors who were RIBA confirmed positive, but were negative on mini pool NAT.
The current sort of expectation is that these
people, most of them, have resolved their HCV infection, which we know people
do, about 20 percent, within the first year of infection.
What she is finding is that some of these
donors do have low level persisting viremia, or intermittently detectable very
low viral load, completely normal ALT.
They are getting risk factor information administered and, like most
RIBA positive donors, when they come back, 80, 90 percent of these people we
can elicit a remote risk factor.
So, they do have some risk, decades earlier,
often. Most of these are, again, we believe resolved infections.
The main message there, I think, is that one
consideration might be that if you have a donor who was EIA reactive and
negative on mini pool NAT, then we do the RIBA and the RIBA is positive.
The question is whether it should be the
blood bank responsibility to do an individual donation NAT or not, or try to
figure this out.
What the problem is, we cannot take on the
burden of following these people over time.
A single retest on the index donation is in no way definitive, even if
you do two replicates, et cetera.
The point, in my opinion here -- if you then
refer these people to the clinic -- and we did a bunch of replicate TMAs, they
don't have a test that could match the sensitivity of that assay.
So, they are going to end up saying the blood
bank was wrong, we can't find RNA. So,
I guess the point is, I think it is at that point that the blood bank's
responsibility for figuring this out is over, and they need to be referred to a
hepatology work up.
DR. QUIROLO:
How many of the donors who are reinstated, do you think, will fall back
into this scenario and be re-tested over and over again?
DR. BUSCH:
One of the things that we have learned from reinstatements in the past and
attempted reinstatements is that, unless you really begin to focus in on trying
to reinstate people who were really originally borderline reactive, or even
non-reproducible on the original screening assay, you are going -- or unless
you have changed screening assays -- all you are going to do is keep testing
these people as reactive.
I do think one of the realities is, since it
has been so long that these algorithms have been in limbo, that there is
literally a decade of deferred donors we haven't tried to reinstate.
During that decade, the screening tests have
changed several times, and many of these donors were borderline reactive. The ones that are NAT negative are
reinstatable.
So, my personal hope is that we are going to
see a much greater yield of reinstatement, than we experienced when we tried to
implement reinstatement a decade ago, when we were using the exact same tests
and just bringing these donors back six months later and they were reactive
again, a high fraction of the time.
I think, with time and changing improved
specificity or changing manufacturers of the screening tests, we shouldn't see
a lot of repeat deferral of false positives.
DR. NELSON:
I think the version 3.0 EIA for hepatitis C is more specific than the
version 2.0. So, some of these -- when
the 2.0 was licensed, they were picked up because of non-specificity.
DR. STRONG:
Actually, I think version 3.0 is more sensitive. We had more window cases with the version
2.0 assays for HCV.
Just to reiterate what has already been said,
I think we have suffered for a decade or more with these subjective tests.
In fact, the artistic point of view of
reading the western blot, we used to have people who were very good at that,
but a lot of that subjectivity, of course, has been taken away through GNPs,
and a lot of those bands that would have been called negative by the experts in
the old days actually made the test worse.
So, we have been stuck with this very large
number of donors who come to us with indeterminant western blots because of
false positives, because our assays, of course, are also designed to be more
sensitivity, and sometimes at the expense of specificity.
When the donor is then referred to their
physician, who is running a diagnostic test, it only makes the donor more
angry, because now they are saying there is nothing wrong.
We get angry calls from the donors saying,
what have you done to us, I have just gone through hell because I have been
told I have a positive HIV assay.
I think we can try to get away from this
western blot being the gold standard.
It is not the gold standard. In fact, it is a rather rusted, iron
standard, I think.
DR. SCHNEIDER: One quick comment. Mike, how many of these donors, do you think,
that have been deferred for a period, will come back?
I would think that the impact of what you
suggested would really be on the people who are recently infected or recently
detected as repeat reactive. We are not
going to defer them, and then they have the potential for keeping in the
system.
I can't imagine that a lot of the older
people who have been deferred will bother to come back. I don't know what your
history is of re-recruitment of deferred donors like that.
DR. BUSCH:
It has almost been a decade since we had an active reinstatement, a
really proactive reinstatement program.
It has really been because it was a little
bit unclear what the FDA policies would be with NAT coming into place.
When you are under consent decree, the first
thing FDA comes, when they come to your centers, they want to see the
reinstatement files, to catch you for reinstating somebody inappropriately.
Really, in my mind, there is not really very
contemporary data on the success of reinstatement. I don't think it is going to
be highly successful in terms of the cost benefit, but I think getting a
blanket message out to these thousands of donors that you are reinstatable, even
if that is all that happens, it is reassurance to them.
The reality of having to bring the donors
back, independent of a subsequent donation, and get a sample in order to go
through the testing, it is unfortunate -- I mean, I can understand the
position, but it is unfortunate that we can't simply tell these donors, who we
are sure they are not infected from my mind, the could be walking in off the
street as a first time donor and we wouldn't be asking them to go through a
pre-donation re-qualification step.
I certainly understand Jay's position about
what you know, but that step is a burden, not only in terms of getting the
people to come in and do that, but for the blood center programs to initiate a
large scale, expensive, bring the donors in, independent of a donation, get a
sample, route it through a special system to reinstate. So, it is complex. I don't think we are
going to see a massive increased donor return, for these reasons.
DR. STRONG;
However, just re-establishing the precedent of re-entry is an important
one. I think when we get to HBV DNA and better sensitivity, the opportunity to
reinstate anti-cor positive donors is huge.
I mean, that is probably hundreds of thousands of donors who I think
would come back.
AUDIENCE PARTICIPANT: I just have an example. When we went years ago from deferring ALT
permanently and changed it to one year, we sent thousands of letters out.
The same thing, some of them had been
deferred for many, many years, and the return of donors, where there wasn't any
requirement to come in for a special sample, was still very low.
DR. NELSON:
We are not too far behind today, for a change. Let's take maybe a five
or 10-minute break, and then we will come back.
[Brief recess.]
DR. NELSON:
Okay, we are now ready to open the open public hearing. First is Dr.
Fitzpatrick. Dr. Kleinman?
Agenda Item:
Open Public Hearing.
STATEMENT OF DR. STEVEN KLEINMAN.
DR. KLEINMAN: Good afternoon, and sorry for being a moment late. I am Dr. Steven Kleinman. I am chair of the American Association of
Blood Banks, Transfusion Transmitted Diseases Committee, and we wanted to make
a statement on the supplementary testing.
The American Association of Blood Banks is a
professional society for over 8,000 individuals involved in blood banking and
transfusion medicine, and represents approximately 2,000 institutional members,
including blood collection centers, hospital-based blood banks, and transfusion
services, as they collect, process, distribute and transfuse blood and blood
components, and hepatopoetic stem cells.
Our members are responsible for virtually all
of the blood collected, and more than 80 percent of the blood transfused in
this country.
For over 50 years, the AABB's highest priority
has been to maintain and enhance the safety and availability of the nation's
blood supply.
AABB strongly endorses the revision of
supplemental testing algorithms, such as those presented to the committee by
Dr. Busch, for donors testing EIA repeat reactive for HCV and HIV antibody.
The large amount of data presented to the
committee today clearly establishes the scientific validity of using reactive
nucleic acid tests to establish the existence of HCV or HIV infection in EIA
repeat reactive donors.
In such circumstances, HIV-1 western blot and
HCV RIBA add no useful information to the evaluation of the donor's status.
In addition, the data indicate that HIV-1
western blot has no usefulness in a donor with non-reactive HIV NAT and
negative alternate HIV EIA results.
It is not surprising that an alternative HIV
EIA is superior to a western blot for confirmation of HIV-1 infection.
This is a direct consequence of the continued
improvements in the sensitivity of HIV EIAs.
In contrast, no similar improvements have occurred since the first use
and licensure of the HIV-1 western blot.
We now, and have for some time, been in the
paradoxical situation in which the western blot, originally licensed as the
HIV-1 supplemental assay, is less sensitivity than the screening EIA.
While the scientific validity of using NAT as
a supplemental assay is a necessary prerequisite for making a change, there is
a much more compelling reason for such a revision to FDA's supplemental testing
algorithms.
Indeterminant test results create confusion
and anxiety for the donor. This is well
documented by Reds investigators, who survey donors about their perception of,
and reaction to, the notification process.
Responses were received from 203 donors with
indeterminant results for HIV antibody or p24 antigen, HCV antibody and HTLV
antibody.
These data, from a manuscript in press in
Transfusion, and presented in part earlier today by Dr. Busch, indicate
that the vast majority of such donors were both upset and confused when
initially notified of their test results, and remained upset and confused six
to 12 months later.
This is not surprising, when donors have been
told, based on indeterminant western blot results, that there is some
possibility that they are infected with HIV.
Unfortunately, such notifications are not
confined to only a handful of donors.
According to American Red Cross data, approximately half of all HIV EIA
repeat reactive donors have an indeterminant western blot result.
When the ARC data are projected nationally,
we estimate that over 5,000 donors receive this message annually in the United
States.
Instructions for carrying out the HIV-1,
HIV-2 combined EIA screening assays state:
It is recommended that repeatedly reactive samples be investigated by an
addition, more specific, or supplemental test.
Since the vast majority of donors with
indeterminant HIV western blot results are not infected with HIV-1, it is
apparent that the western blot assay is not achieving the enhanced specificity
expected of a supplemental assay.
Until recently, this situation was a
necessary but unfortunate outcome of the notification process. Given that there
were no alternate means of assessing the donor's infection status.
However, such disservice to the donor
community cannot be justified, when we have the tools available to do better.
If the committee agrees that revising
supplemental testing algorithms is the correct course of action, based on
scientific and ethical consideration, there still appears to be another hurdle
to cross.
Dr. Stramer, in her presentation, quoted 21
CFR 610.40(e), and Dr. Biswas mentioned this as well, that you must further
test each donation, including autologous donations found to be reactive by a
screening test, whenever a supplemental test has been approved for such use by
FDA.
NAT assays do not currently carry these
supplemental testing claims. However, these NAT assays have gone through
rigorous review by FDA for donor screening claims and, as such, meet all CGMP
requirements, including those for clinical and analytical sensitivity,
specificity and reproducibility.
Furthermore, five years of data established
the usefulness of NAT to confirm HIV and HCV infection status, supplemented by
HCV RIBA or HIV alternate EIA in circumstances in which the mini pool NAT is
non-reactive.
In addition, the use of an alternate HIV EIA,
coupled with NAT, will serve to reduce further, by about 95 percent, the number
of HIV-1 western blots that will need to be performed.
Considering these facts, we urge BPAC to
recommend to FDA that it find a way to allow both NAT and the HIV-1 alternate
EIA approach to be a major part of HIV and HCV supplemental testing algorithms
-- and this is important -- without requiring new clinical trials to establish
this claim.
To this end, we also encourage the
manufacturers of NAT and HIV EIAs to work with blood centers to submit the
required supplemental claim data to FDA for expedited review. Thank you.
DR. NELSON:
Thank you. Any questions? Okay, Dr. Fitzpatrick.
STATEMENT OF DR. MICHAEL FITZPATRICK
DR. FITZPATRICK: Mike Fitzpatrick from America's Blood Centers. I am paid by
America's Blood Centers, who represent 75 independent community based blood
centers, just to have that on the record.
We want to support Dr. Kleinman and the AABB
statement. We believe the algorithms
presented by Dr. Busch and Dr. Stramer, using NAT to confirm EIA test
results as a supplemental test, are accurate and should be used.
We have the support from our members, if
there is other data required for FDA, to allow a change in the literature of
the manufacturers that allows it to be used as supplemental tests, we would be
happy to support and help collect that data, so that we can accomplish this as
quickly as possible, should the committee recommend that we go forward with
this. That is all. Thank you.
DR. NELSON:
Thank you. Dr. Smallwood has a
comment.
Agenda Item:
Open Committee Discussion.
Question for the Committee.
Committee Discussion and Recommendations.
DR. SMALLWOOD: ORTHO Clinical Diagnostics wanted it to be read into the record,
for clarification, that the hepatitis antigen test for ORTHO Clinical
Diagnostics is called HBsAg System 3.0.
The hepatitis antigen test from Biorad
antigen test is called the Genetic System HBsAg EIA 3.0.
DR. NELSON:
Okay. Now back to Dr. Biswas,
can you clarify what you would like the committee to do or discuss or
contemplate?
DR. BISWAS:
Let's go to the questions. Let's
go through them one by one. What we
would like you to do is comment and discuss what you think about it.
Obviously, we have got a huge amount of
data. So, we, ourselves, will have to
pore over this data, as you have, in a very short time, but we would like input
into the questions, taking into account also the data and the algorithms that
have been suggested.
So, please comment on the relative
performance of, 1, RIBA versus HCV NAT to confirm or validate a reactive
screening test result in a blood donor testing setting.
So, we would like to hear your views on
that. What I heard personally is that,
for both HIV and HCV, NAT is taking a big step forward.
DR. NELSON:
Since NAT is performed routinely, and since EIA reactive donors will
have NAT results when they are blood donors, it had never made sense to me that
a RIBA test should be done on a donor who is Nat positive and EIA positive.
I guess that is the current algorithm, which
doesn't make sense, and I would like anybody to comment, if anybody thinks it
makes sense at this point.
DR. CHAMBERLAND: I think just as a general sort of umbrella comment, what at least
I have taken away from the presentations and, as you said, sort of just a
relatively superficial opportunity to review them, what you come away with
thinking is that we really have evolved to a point in time where we should be
able to take advantage of all of the testing that is routinely performed.
Then, if there should be consideration for
additional testing, be it a duplicate EIA or, in the instance in which you have
discordant results, trying to then bring in another assay or another approach,
it just seems to me that we really have reached that time when we really can
consider new algorithms in the blood collection setting.
Several have been proposed and will probably
require some detailed review, but I think I will be in agreement that the time
is here to really seriously do this and consider some of the specifics.
DR. NELSON: Is it currently a violation of
FDA procedure if a blood bank has a positive NAT and a repeat positive EIA and
doesn't do a RIBA? That is a violation?
DR. BISWAS:
Yes, it is.
DR. NELSON:
We can vote on what it shouldn't be.
DR. EPSTEIN:
We require that a supplemental test be performed, if available, and
labeled for that purpose. That doesn't
prevent us from labeling NAT tests as supplemental for EIA, if we think that is
the right thing to do.
Now, we would be creating a novel beast,
which is something that is both a screen and a supplemental test, but if that
is where the science goes, that is where the science goes.
DR. NELSON:
Of course, the other issue is, theoretically a supplemental test should
be definitive, did the patient have an infection or not, and 20 percent of
hepatitis C EIA positives really did have an infection, but they have cleared
it. Maybe I am misinterpreting what the
supplemental test means.
DR. EPSTEIN:
No, you haven't. It is just that we are really introducing a totally
different concept, which is to confirm infection rather than confirm the assay
for the analite.
If you run an NAT, after all, you are not
confirming that the antibody is real.
So, we are introducing a whole new concept here.
DR. ALLEN:
A number of thoughts. We had
gotten much of the material in advance, but it is sometimes difficult to
interpret it exactly, absent the commentary the presenters give.
You know, we have gone through an enormous
amount of data from many different presenters on two different infectious
agents this afternoon.
I am glad we are not voting on any questions,
but are being asked to make some commentary.
Let me make just a few comments.
First of all, in terms of the laboratory
tests themselves, in a setting such as a blood bank, where you have got a
fairly large -- and I hate the term, throughput, but you have got a large
number of samples that have to be done on a routine basis.
It is obviously better if the test can be at
least semi-automated, if not automated, so that any of the tests that really
require a lot of individual preparation, individual reading, that sort of
thing, are much less useful, much more difficult to standardize and so on.
I would much rather have a test system that
is being used every single day, and you run the specimen through a second time
or on the same platform or parallel platform using a different test as a
confirmatory or supplemental test. It is obviously extremely helpful.
We have gotten, today, technology to a point
that I think few of us would have imagined 20 years ago, when some of these
tests were first beginning to appear on the market.
That is the point where our routine screening
tests are as sensitive and as specific as any of the supplemental tests that
may be available.
That, in some ways, is beautiful. In other
ways, it does complicate the issue of trying to decide exactly what algorithm
one uses.
I am still humbled by the fact that, even
with the best of the tests available today, we still don't have 100 percent
sensitivity and specificity.
I think the algorithms that were presented by
many of the presenters today allow us to come very close to that. My
preference, obviously, is to use several different platforms, several different
combinations, always looking at the issues that are there.
I think, before one informs the patient, or
the donor, exactly, one needs to take into account what is happening in that
person's life. You don't like to take
the laboratory tests in isolation.
With regard to the question that is up there,
or the issue that is up there right now, I think the issue of signal to cut off
can be extremely helpful, but one would like to be able to use the test results
as they come, without having to factor in, was this a high signal or a low
signal.
Sometimes that can be helpful, but I would
prefer to see an algorithm that doesn't have that degree of flexibility in
there.
DR. BISWAS:
Thank you for that comment. Keep
in mind that the supplemental confirmatory testing is done for basically a
couple of reasons.
One thing is that you want to inform the
donor exactly where they stand, as far as their health status is concerned.
The other thing is that you might want to
reenter, and it is used as a reentry.
For reentry, of course, in addition to extra testing, keep in mind there
is a six, eight week, or six month period, when one can re-test again. I suppose, when one is counseling, one can
also, up to a point, do that, too.
In regard to the signal to cut off, in this
context, I think that it was Sue Stramer who said that it might help in
counseling.
DR. STRAMER:
Right.
DR. NELSON:
I think it is important for the donor to know if, in fact, an infection
has occurred, in addition to the issue of deferral. So, the signal to cut off.
You are talking in number two, I guess, about
signal to cut off in a repeat sample, or in the first sample?
DR. BISWAS:
I think the CDC -- I think Wendi Kuhnert is no longer here -- but my
understanding is that it is in the first, in that index sample.
DR. NELSON:
Her presentation was more in regard to clinical lab testing than it was
in regard to what we do in the blood bank.
So, there are some differences.
DR. BUSCH:
My point is that I think we have seen an enormous amount of data from
the blood centers that show that these tests are extremely accurate, and we can
use NAT in the blood center environment and it is extremely accurate.
I think we have to be cautious about
extrapolating that to a general confirmatory diagnostic claim for supplemental
testing for these assays.
We have been involved in studies -- you
probably have, too, Kenrad -- where you apply these RNA assays in high
prevalence settings in public health laboratories, and you get a fair amount of
false positivity often due to sample carry over, can't be reproduced. In study after study, it is kind of like
what we talked about earlier.
So, my concern about Jay's suggestion of
really trying to get supplemental testing, the solution being getting a
supplemental testing claim for these RNA assays, that would be generic and
applicable in all public health sectors, is that we haven't seen the data.
My personal expectation is that, were these
tests employed in lieu of confirmatory serology or alternate serology, there
would be some false positivity and problems.
The alternative would be to essentially
revive that earlier algorithm that stipulates that, for blood donor screening,
if there is a reactive screening test, and there is an available licensed
supplemental, you must do that.
Instead, we could revise that to allow
integration of the various data, because it is that, that gets us into the loop
mandating testing we don't necessarily think, in our low prevalence, extremely
GNP oriented testing settings, is giving us very accurate results.
DR. NELSON:
I guess, number two, the signal to cut off, would also include testing
it with a different manufacturer's EIA.
That is what is used in the third world rather than --
DR. BISWAS:
No, I think it was on --
DR. NELSON:
Just the initial sample. The
other alternative is to re-test it with a different manufacturer and look at
that signal to cut off as well.
DR. STRAMER:
Can I interrupt that? In the
beginning of my talk, when I talked about why a dual EIA algorithm would be
advantageous for HIV, but not HCV, the HCV tests are too similar. So, we are going to get false positive
overlap, and then you are telling a donor you are concordant repeat reactive.
DR. KLEIN:
I just think that the message we have heard is that we now have decades
worth of data on tests that we collect every day.
We don't seem to integrate them into
algorithms that would be very helpful, both for informing the donor and for
recalling donors who have not been infected.
I guess I would encourage the FDA to, having
heard all of this data, and analyzing it as we speak, to go back and look at
these algorithms and see whether it might be worthwhile to change a regulation
that clearly is out of date.
DR. BISWAS:
I think that the answer to that is to point out that this is the first
time we have looked at this data which has been sort of data, and cost Mike and
Sue hours, if not days, if not weeks, of getting all this together. I think everybody owes them a great debt.
Yes, the testing has been going on, now,
somebody said since 1999, using the NAT, the pooled NAT for whole blood. So, it is just now that a couple of people
have got together and put all the data together.
DR. KLEIN:
We also have follow up on donors, now, going back to 1985. We have data on new tests that have been
introduced. We have the signal to cut off ratios that have been looked at over
time. So, now we have an enormous
amount of data.
I think we sometimes get hung up on the idea
that we have a regulation and, boy, it is a lot of work to change that.
A lot of times, when a regulation is
outdated, at least we ought to keep our minds open to the concept of changing
the regulation rather than, perhaps, redefining what a test is. That is all I am saying.
DR. EPSTEIN:
I just wanted to push back a little bit because, you know, we
promulgated the requirement for supplemental testing, because supplemental
testing was not being universally tested on donors who were being deferred.
We felt that the public health good lay in
giving people confirmed results rather than unconfirmed screening results. I
think that principle remains sound.
The difficulty that we have gotten into is
that we now think that an alternative form of screening may be a better
supplemental test than those that have been previously approved.
I think we should keep an open mind and not
automatically think that the problem is the regulation, because the regulation
solved the problem that needed solving, in reporting unconfirmed screening
results.
DR. LINDEN:
Along the same lines, I am scientifically in agreement with
everyone. It seems that the solution is
really a different approach, that NAT really seems to be a superior
supplemental test.
I agree with Jay that the regulation is there
for a reason. Maybe we need to just
open our minds in terms of the definition of a supplemental assay.
Maybe we ought to look at a way that the NAT
could be considered a supplemental assay for purposes of blood donor screening
only, not getting into the whole issue of diagnostic testing.
There may be other ways of getting at the
same issue short of changing the regulation, but I think that is an issue FDA
can deal with, based on our recommendations that we basically agree with this
approach.
DR. KLEINMAN: I just wanted to mention that, in these new algorithms, neither
of the algorithms discards further serological testing.
It says that, in one arm of the algorithm,
NAT is enough because you have a positive NAT, you don't need to do any more.
Both HIV and HCV algorithms that were
proposed say that, if NAT is negative, then you still have to evaluate whether
the presence of antibody is there.
You can do it by RIBA, which seems to be a
good test, or you can do it in HIV. We
are hoping we can do it within alternative EIA, which seems to be a much better
test than a western blot.
I would hasten to say that, if the western
blot came to the market today and was submitted to FDA and had to undergo the
evaluation of, is this a good supplementary test, should this test be licensed.
These performance data don't justify
licensure, in my mind. It is just a
historical point, and we know that manufacturers don't bring confirmatory
antibody tests to market very frequently.
We are still waiting for one for HTLV, and
this has been talked about in front of BPAC quite frequently, that there is not
enough of a market.
Well, HIV Is different, because you have the
whole diagnostic testing market, obviously, but nobody has gone, to my
knowledge -- these tests have not evolved.
So, we are using a tool that was blessed with
FDA licensure circa 1985 or 1987, and it is the only tool we can use because,
at that time, there was an incentive for the manufacturer to go to the expense
and do the trials to get the test licensed.
I don't see that anybody is stepping forward
to do that now, so we are stuck with a bad tool. I just want to point out that the algorithm doesn't get rid of
serological confirmation, if NAT is negative.
So, we are really using a broader algorithm,
with more than one supplementary test, depending on where you fall on the
algorithm.
DR. SCHREIBER: I agree with Steve. I think the benefit of what has been proposed
is that it eliminates a lot of the uncertainty that exists in the supplemental
testing system that we have now.
In terms of the counseling for the donor, I
think it is a big plus. I think there
are some ideas to work through here.
We did get a lot of data from Sue and Mike
and it is really hard to digest all at once, but I think that the concept of
modifying the algorithm, at least in my mind, is certainly the right track.
DR. BISWAS:
Shall we look at the other slide?
Western blot versus HIV NAT?
There has already been a lot of comment.
DR. KLEIN:
Same comment.
DR. BISWAS:
Western blot versus a second EIA for anti-HIV. There has been a lot of discussion of that. Anything else?
DR. NELSON: I guess we don't have to vote,
but does anybody have any statements that don't agree with what has been said?
DR. ALLEN:
Just me just say that I Strongly agree with what Steve Kleinman said,
and I will reiterate the question that I had raised earlier, which is the
degree of indeterminants in western blot make that a highly problematic test,
and I think we really need to look at alternatives that don't have the problems
that exist with the indeterminant results.
DR. NELSON:
Thank you.
DR. STRONG:
Just to support Jay's comment about public health, I think in this
particular situation we may have done some harm with this particular
supplemental test.
I think if we can improve on that, we can
still accomplish the public health purpose, but perhaps in a much better and
more efficient way.
DR. EPSTEIN:
I just would like to comment on the issue of the problematic western
blot. The western blot is certainly
problematic, but if you look at the positive predictive value when it is
meeting positive criteria, all the data show that it is very, very high.
When you look at the negative predictive
value when it meets negative criteria, all the data show that it is very, very
high.
It isn't that it is intrinsically a bad test
when it meets the standard of being interpreted positive or negative.
The problem has been what to do with all the
noise in the assay. We actually
discussed this at great length at a conference at CDC, which I think was in
1991.
The point of view was brought forward that it
really needed a finer stratification, positive, probably positive, probably
negative, or even a finer gradation than that.
That was felt to be, you know, not off the
targeted map. After all, there were
things like PAP smears that were graded that way in public health laboratories,
and that that would give us the room to recognize that some of these patterns
carried more risk than other patterns.
So, if you had just non-viral bands, you
could probably say it was a highly probably negative test, even though it
didn't meet strict negative criteria.
If it has certain configurations of
presumptive viral bands without meeting strict criteria, you could say it was
highly probably positive, although it didn't meet positive criteria.
When you think about the data we just heard
today, Sue pointed all this out, and so did Mike. If you actually stratify the
western blot and the RIBA by pattern, you can actually remarkably enhance its
predictive value.
The bottom line was that there was enormous
objection from the clinical diagnostic community to going that direction with
the test.
They wanted the test to give a discreet
answer. There was a great deal of
pressure that we should relax the criteria for positive to a two-band criteria,
even allowing double on, to clear what was then the majority of the source of
the indeterminacy, and remove the indeterminants that were probably positive
into the positive category.
That change was later effected and it did it,
but at the price of a small but real false positive rate to the blot that
didn't exist before that.
As I reflect back on this, this was a test
that had significant limitations, but we imposed interpreting limitations on it
in order to accomplish simplicity, and that was at the cost of causing confused
messages.
Again, when we say it was a failed test, it
wasn't really. It is that we didn't,
sort of, adhere to its own nature. We
imposed a simplified interpretation on a test that actually had a fairly
complicated read out.
Be that as it may, I don't object to the
observation that NAT may be a better tool. I think we want to think about how
to integrate NAT in our other algorithms.
DR. NELSON:
The other issue was that, with the western blot, by following the
patient, you could eventually come to a clear conclusion. In the blood bank, that is not what they do.
You have got to tell the patient something
right after the test comes back at that time, that they may be infected, that
they are infected, that they are probably not infected. Again, I see that as a problem.
DR. EPSTEIN:
Again, the problem is not that one lost diagnostic information, because
you sort it out by doing other tests and following the patient over time.
The problem is that, among those who are told
they are indeterminant who are not infected, you needlessly scared people.
DR. STRAMER:
I would just like to add to what Jay said regarding NAT. For HIV, regarding the use of a second EIA,
we should be able to integrate a second EIA into a supplemental testing
algorithm.
Blood centers use one EIA, they pick any FDA
licensed test that fits into their criteria for their own blood center. They test it once in one wrap and blood is
transfused.
My question is why, if it is good enough for
transfusion, why wouldn't it be good enough to add to a confirmatory algorithm
as well?
DR. NELSON:
It should be. Is there any
discussion on that?
DR. EPSTEIN;
The question of whether you could use a second EIA to override an
initial EIA has been raised since the git go.
The historic answer has always been that we
are never sure, in this horse race, which is the right answer among two EIAs.
Now, adding the dimension of a third test,
which is negative NAT, may change that picture, but there is an inherent
problem with allowing a second EIA to override a first, because they may not
have identical sensitivity.
DR. BUSCH:
On this topic, I think we all know that the EIAs today are significantly
more sensitive than the blot on a seroconversion panel.
In addition, we now have HIV-1, HIV-2 EIAs,
which has required that, when we have a reactive EIA, we have to do both an
HIV-2 EIA and an HIV-1 western blot. If
the HIV-2 EIA we have to do an HIV-2 -- now we have group 0 enhanced.
The assays we are talking about are going to
be HIV-1, HIV-2, HIV-1 group 0. We
don't have supplemental tests. Are we
going to have to find some kind of group 0?
I think the alternate EIAs, more than ever,
become wanted. They are very sensitive,
third generation, they have these multi-viral strain detection capacities. It really is extremely appealing to
integrate an alternate EIA and avoid the supplemental problems.
DR. NELSON:
To get back to what Jay said, if you have got two EIAs with different
results, before you can reenter, don't you have to get a separate sample and
get negative tests again before you can use that donor?
So, it turns out not to be one versus another,
but there is one versus another, and then another testing on another sample.
DR. BISWAS:
At a later time, yes.
DR. STRONG:
I think after all this discussion, it really comes down to AABB's
recommendation, which is to recommend to FDA that it find a way to allow all of
these factors to be included in approaches for supplemental testing algorithms.
DR. NELSON:
Particularly when the NAT is positive and the EIA is positive, the
western blot and the RIBA is an added expense, but it really doesn't tell you
anything.
From what I interpreted, that was a pretty
large proportion of the western blots or the RIBAs that are done now. Maybe I am wrong. The data went quickly.
DR. BISWAS:
Forty percent for RIBA, I think.
DR. STRAMER:
HIV repeat reactives, only five percent are RNA positive. We still have 95 percent of the population
where we blot them.
DR. NELSON:
In the RIBAs it was different. It was a higher proportion.
DR. KLEINMAN: I just wanted to follow up on Mike Strong's comment and say that
the AABB realizes that these algorithms are being proposed essentially for the
first time now, and that they are going to need more discussion.
I think we wanted to strongly say to BPAC
that an endorsement in principle that the time has come to change the
algorithms and take into account what we have learned and the experience with
new technology is what we really wanted our position to be to BPAC.
I want to expand on that and say that
certainly the AABB, and I would speak for Red Cross and ABC as well, is
certainly willing to work with FDA to have further discussions to see what data
is actually needed to substantiate the presentations that are made today, and
to find a way to take all of the resources, as Mike Fitzpatrick said, from all
the ABC centers, and gather the data that is necessary, and present it in a
form that the FDA can evaluate and feel comfortable with.
We realize that manufacturers have to
participate in this as well. I think
the only caveat that we want to get here is that we are hopeful that we don't
have to start new, formal clinical trials to get licensure for another
indication for a test.
That would really fly in the face of this
massive data collection effort. It is 25 million units that were evaluated by
Red Cross. It would be a shame to say that wasn't collected under controlled
IND conditions. But it was.
So, I gave Sue a heart attack there in the
first row, but it is good, because it is 5:15 and everybody is getting tired,
but my point being, there is so much data out there and it has been presented
today, and any way that we can refine that data further, provide FDA with what
they need so that they feel comfortable that the algorithm revisions can be
supported and the claims can be made, I think everybody is committed to doing
that.
DR. NELSON:
Thank you. Any other comments or suggestions? All right, are you happy with our discussion?
DR. BISWAS:
Oh, very much so.
DR. NELSON:
So, tomorrow morning at 8:00 o'clock.
[Whereupon, at 5:25 p.m., the meeting was
recessed, to reconvene the following day, Friday, March 19, 2004.]