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:
March 18, 2004
2 Montgomery Village Avenue
10201 Lee Highway, Suite 160
Fairfax, Virginia 22030
TABLE OF CONTENTS
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
- 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- Current Thinking on Draft Guidance for Nucleic Acid 173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
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.
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.
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. 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.
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.