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UNITED STATES OPF AMERICA
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FOOD AND DRUG ADMINISTRATION
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CENTER FOR BIOLOGICS EVALUATION AND RESEARCH
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BIOLOGICAL RESPONSE MODIFIERS ADVISORY
COMMITTEE
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34th MEETING
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FRIDAY,
FEBRUARY 28, 2003
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The
Advisory Committee was called to order at 8:01 a.m. in the Kennedy Ballroom of
the Holiday Inn- Silver Spring, 8777 Georgia Avenue, Silver Spring, Maryland, Dr. Daniel R. Salomon, Chairman,
presiding.
PRESENT:
DANIEL R. SALOMON. M.D. Chairman
JONATHAN S. ALLAN, D.V.M. Member
BARBARA BALLARD Patient Representative
JOHN COFFIN, Ph.D. Temporary Voting Member
KENNETH CORNETTA, M.D. Temporary Voting Member
JOHN E. FRENCH, Ph.D. Temporary Voting Member
DAVID M. HARLAN, M.D. Member
KATHERINE A. HIGH, M.D. Member
JOANNE KURTZBERG, M.D. Member
ALISON F. LAWTON Industry Representative
WARREN LEONARD, M.D. Temporary Voting Member
CRYSTAL MACKALL, M.D. Temporary Voting Member
ABBEY S. MEYERS Temporary Voting Member
RICHARD C. MULLIGAN, Ph.D. Member
THOMAS MURRAY, Ph.D. Temporary Voting Member
PRESENT:
(CONT.)
MAHENDRA S. RAO, M.D., Ph.D. Member
BRUCE E. TORBETT, Ph.D. Temporary Voting Member
ANASTASIOS A. TSIATIS, Ph.D. Member
LINDA WOLFF, Ph.D. Temporary Voting Member
ALICE J. WOLFSON, J.D. Consumer Representative
GAIL DAPOLITO Executive Secretary
NIH REPRESENTATIVES:
STEPHEN M. ROSE, Ph.D.
GUEST SPEAKERS:
CLAUDIO BORDIGNON, M.D.
MARINA CAVAZZANA-CALVO,M.D., Ph.D.
ADRIAN THRASHER, M.D., Ph.D.
PRESENTERS FROM FDA:
PHILIP NOGUCHI, M.D.
RAJ K. PURI, M.D., Ph.D.
CYNTHIA A. RASK, M.D.
CAROLYN WILSON, Ph.D.
PUBLIC SPEAKERS:
PAUL GELSINGER
RICHARD JUNGHANS, Ph.D., M.D.
CHRISTOF VON KALLE, M.D.
DONALD B.KOHN, M.D.
RACHEL SALZMAN, M.D.
Morning Session
Welcome
and Introductory Remarks ............... 4
Daniel
Salomon, M.D., Chair
Meeting
Statement .............................. 4
Gail
Dapolito, Executive Secretary
Guest Presentations
Dr. Marina Cavazzana-Calvo............... 34
Dr. Claudio Bordignon ................... 92
Dr. Adrian Thrasher..................... 119
Discussion.............................. 132
Committee
Discussion of Questions............. 166
Public Hearing
Donald Kohn............................. 177
Rachel Salzman.......................... 187
Richard Junghans........................ 191
Paul Gelsinger.......................... 197
Discussion
and Voting......................... 199
Adjourn....................................... 304
P-R-O-C-E-E-D-I-N-G-S
(8:01
a.m.)
CHAIRMAN
SALOMON: I want to welcome everyone
here to the second day of Meeting Number 34 of the BRMAC, which of course
doesn't mean anything to anyone, including me.
What
does mean something is the topic for today, which is to update the Committee,
and to provide advice to the FDA on retroviral gene therapies, particularly
focused obviously on the cases of severe combined immunodeficiency
disease. But certainly the discussions
need to range somewhat beyond that narrow focus at some point. The nature of the topic is absolutely
important and critical, and I think that does not need any introduction, so I
will spare you that.
The
day is relatively compressed, just because it is Friday, and with the snow and
trying to get to airports, I would like to be done at 3:00. Otherwise, I am not making it back to
California this evening.
So
you have got a Chair who is engaged in finishing on time, which is usually a
good thing. So without any other
introduction at the moment. We will pick up with the FDA's introduction in a
moment.
I
would like to turn to Gail Dapolito, our Executive Secretary, to read a
statement into the minutes.
MS.
DAPOLITO: Good morning, everyone. This announcement is part of the public
record for the Biological Response Modifiers Advisory Committee meeting on
February 28, 2003. Pursuant to the
authority granted under the Committee charter, the Director of the FDA's Center
for Biologic Evaluation and Research has appointed Ms. Barbara Ballard and Ms.
Abbey Meyers, and Drs. John Coffin, Kenneth Cornetta, John French, Warren
Leonard, Stewart Orkin, Crystal Mackall, Thomas Murray, Bruce Torbett and Linda
Wolf as temporary voting members for today's discussions.
Based
on the agenda, it was determined that there are no products being approved at
this meeting. The Committee
participants were screened for their financial interests to determine if any
conflicts of interest exist.
The
Agency reviewed the submitted agenda and all financial interests reported by
the meeting participants. As a result
of this review the following disclosures are being made.
In
accordance with 18 USC 208, Drs. John Coffin, Kenneth Cornetta, and
Warren Leonard were each granted a waiver that permits them to participate in
today's committee discussions.
Dr.
Richard Mulligan was granted a limited waiver for today's discussions that
permits him to participate in the discussion without a vote. We also note for the record that Ms. Alison
Lawton serves as the non-voting industry representative member acting on behalf
of a regulated industry.
She
is employed by Genzyme, and thus has interests in her employer and other
similar firms. With regard to FDA's
invited guest speakers and guests, the agency has determined that the services
of these speakers and guests are essential.
The
following interests are being made public to allow meeting participants to
objectively evaluate any presentation and/or comments made by the speakers and
guests. Dr. Claudio Bordignon is
employed at the Institute of Science in Milan, Italy. He is a researcher in gene therapy clinical trials, especially
ADA-SCID, and has associations with firms involved with retroviral vectors.
Dr.
Marina Cavazzana-Calvo is employed at the Necker Hospital in Paris,
France. She is involved in retroviral
vector gene therapy studies to treat patients with X-SCID.
Dr.
Adrian Thrasher is employed at the University College in London, England. He is a researcher in gene therapy clinical
trials to treat patients with SCID.
Dr.
Cristof von Kalle is employed at the University of Cincinnati, and is involved
in gene therapy research. Drs. Amy
Patterson and Stephen Rose are employed with the Recombinant DNA Program,
Office of Biotechnology Activities, NIH.
NIH funds gene therapy research.
Members
and consultants are aware of the need to exclude themselves from discussion
involving specific products or firms for which they have not been screened for
conflict of interests. Their exclusion
will be noted for the public record.
With
respect to all other meeting participants, we ask in the interest of fairness
that you state your name, affiliation, and address any current or previous
financial involvement with any firm whose product you wish to comment upon.
Waivers
are available by written request under the Freedom of Information Act, and as a
courtesy to the committee discussion and those in the audience, and we ask that
you silence your cell phones and pagers.
Thank you.
CHAIRMAN
SALOMON: Before I turn to Phil and
Carolyn to provide an FDA introduction, I just wanted to share with you sort of
a brief strategy for today as far as I am concerned as Chair.
We
have many of us sitting around the table right now, with a few additions to increase
the expertise here, but most of us have heard the first round of this issue,
with the first child that developed leukemia from the retroviral insertion in
the LMO-2 site just before the first of the year.
And
so I think it is very important that the focus of this meeting begin solidly on
the framework that the committee set at that time and ask the major question;
and that is, what has changed?
At
the time, we talked about what would happen if a second case was found. How would that change the risk/benefit ratio
calculations that we made? How does
that serve the community and affect the stakeholders with severe combined
immune deficiency disease? How does
that affect the broader stakeholder community that now includes anyone who
might benefit from various kinds of retroviral gene therapy and the companies
and academia, et cetera, that are involved.
So
I think the key thing here is to take the foundation of what we did last time.
It is perfectly appropriate to say, well, we were right about this, and it
incrementally changed in such and such a way, or that we were wrong, and we
need to see it.
But
I'd like to see the focus building on what we set up previously, rather than
starting all over again and taking everything apart and taking a really long
time to go over what I think -- we already plowed a lot of ground here, and I
would like to see us go forward from this point onward. Phil.
DR.
NOGUCHI: Thank you, Dan, and I would
like to thank everyone who is participating today on behalf of the Center for
Biologics. Our grateful thanks for coming here.
This
is extraordinarily difficult and is one of a number of things that I would like
to just introduce. I presented something like this at the last meeting, but why
are we here?
We
are here to acknowledge that there continues to be extraordinarily difficult
diseases and the treatment of them remain hopeful, but are always a problem in
terms of balancing risks and benefits.
And
we are here to affirm that the way to get at this ideal is to do rigorous
clinical trials. As we do this, and as
we are seeing today, this is not a static evaluation, but it is a continuous
balancing of risks and benefits.
We
are here to further learn about adverse events as they occur, and as they are
scientifically researched, and I think some of our discussion should be
oriented towards taking what we now know and thinking of strategies for
mitigation and elimination of these particular side effects, as well as
strategies for side effects in general, where we know more on a molecular basis
than we did even just a few months ago.
And
really we are here to confirm that this is exactly where we should be, and we
look forward to a very vigorous, a very timely and a very important
discussion.
Dr.
Wilson will now follow this and really step us through a little bit of the
background from the last meeting and lay out the framework and the pathway for
our discussion today.
DR.
WILSON: While they are getting it set
up, I am just going to introduce that what I will be doing today is to try to
provide an update for the committee since our last meeting in October.
And
that update will include, actually, a revisiting of the discussion that this
committee had, so that analogous to what Dr. Salomon was just saying, we can
remind the committee what we said in October, and then move forward from there.
(Brief
pause.)
CHAIRMAN
SALOMON: This is a new California thing
where you kind of start the meeting off with a Zen meditation. I hope you appreciate that.
DR.
WILSON: Thank you, everyone, for your
patience. And so, again, what I am
going to do for you this morning is to try to provide an update so that you can
have all the information at hand in terms of what has happened since the
October meeting, so that you can move forward in your deliberations on these
important safety issues regarding the clinical use of retroviral vectors for
gene therapy.
My
update will include, as I mentioned, a review of the consensus points from the
discussion of the October meeting, subsequent FDA actions that we have taken
both in response to the October meeting as well as to the subsequent
notification in late December from Dr. Fischer's group of the second child with
the T-cell expansion.
I
am going to provide a quick overview of active clinical trials that are under
U.S. IND that use retroviral vectors, and then provide some information from
other committees that have been deliberating on these issues, in particular the
recommendations from the Recombinant DNA Advisory Committee that met earlier
this month, as well as some of the reports from various international bodies as
well.
And
then finish with just a quick read-through of the questions for the committee
so that you can have these in your mind as we move forward with today's agenda.
So
to start off, the one general consensus of the committee in October was that
the T-cell expansion seen in the X-SCID patient treated in France was likely
due to an insertional mutagenesis effect of the retroviral vector used in the
gene therapy.
With
this as a premise in terms of a major conclusion, then you move forward to
address the following question which we asked you in October; namely, are there additional data or
measures that clinical investigators need to provide before future and present
clinical trials in SCID patients should proceed in the U.S.?
Please
consider in your discussion each of the following as they pertain to X-SCID or
other forms, such as ADA. And we asked
you to discuss six different issues: risk/benefit, informed consent,
alterations to cell dose or vector dose, mapping of vector insertion sites, and
alterations in vector design.
And
what I would like to do in the next few minutes is just provide for you, again,
your committee consensus on each of these points so that you know where you
were in October.
So
regarding risk/benefit, all agreed that, with HLA-identical donors for SCID
indications, the benefits of this
particular treatment far outweighed the potential risks of using gene therapy.
So
the committee recommended that patients who have available HLA-identical donors
should be excluded from gene therapy clinical trials. However, the case for haploidentical transplants was not as
clear-cut, in that you do get 90 percent survival if the transplant is done in
the newborn period.
Survival
rates are lower, depending on the transplant center, when it is done later in
life. But in both cases, you don't seem
to get B-cell reconstitution requiring life-long administration of an IgIV.
And
there was a general consensus that the quality of life for even those patients,
quote, "who are surviving" is suboptimal, with recurring infectious
episodes and other complications.
The
other major point that was brought up in the discussion of risk/benefit issues
was the analogy to cancer treatments, which often carry risk of secondary
cancer, yet are very effective at treating cancer and would not be thought of
as being eliminated because of the risk of secondary cancer.
As
far as the risk of gene therapy, all acknowledged the obvious statement that if
you don't get gene transfer, then, of course, it is a safe procedure. But in the case of the trial in France,
clearly there is gene transfer and it is having a therapeutic effect.
And
there is actually 100-percent survival at this time, even now with the second
child having a leukemia-like illness.
And the other important point that was brought out was that the success
of Dr. Fischer's trial may be related to the fact that he treats patients de
novo, and he is not using patients who had failed haploidentical
transplants.
So
the committee felt it was important that gene therapy in this context not be
considered a salvage therapy but that families be given a choice to have a
haploidentical or gene therapy.
And
so, essentially, in October the committee consensus was that trials in SCID
indications should proceed, but there were some caveats on that conclusion;
namely, that clearly changes to informed consent documents needed to be made. You felt it was important that all
retroviral vector clinical trials should have these revisions to reflect this
event.
The
informed consent document should be written in clear language. It should not
include mitigating factors, such as issues regarding multiple hits, or number
of patients treated, and that it should be clear in saying that gene therapy
caused the leukemia, while still emphasizing the unknown quality regarding the
risk to an individual patient.
On
the third part of this question regarding cell dose, there was some information
provided by the committee regarding, for example, use of cord blood, that you
may be able to reduce the numbers somewhat and still maintain engraftment.
The
number that was thrown out by the committee was one times ten to the fifth CD34
positive cells per kilogram. I
recognize that you had extensive discussions of this yesterday, so you probably
are much more informed on this, at this point, than I am, and so I will just
leave it at that.
But,
essentially, after going about this issue, the committee felt that based on 30
years of experience that there are certain acknowledged minimum cell doses that
are required in order to get engraftment, and that to go below those doses
would provide -- would put these children at risk of additional infectious
disease complications.
So,
actually, the committee recommended moving forward on researching how to better
target the true hematopoietic stem cell, and that would be a more effective way
to reduce the cell dose.
Regarding
vector dose, this was really felt to be a research question. People also felt this wasn't a huge issue at
that time because most retroviral vectors hit about one copy per cell.
However,
CBER does want to point out that we are starting to see novel vector systems
that reach significantly higher copy numbers per target cell, and that this is
an issue that the committee may need to revisit.
In
terms of insertion site mapping, the way that we had phrased the question was
regarding lot release of ex vivo transduced cells. The committee quickly pointed out that this was not
scientifically or technically feasible, and this was obviously rejected.
However,
there was a strong recommendation from the committee that patient samples
should be monitored closely for outgrowth of single clones, and that if a
monoclonal integrant is observed, that it should be sequenced, following with
additional phenotypic analyses. And it
was pointed out that this information regarding the integration site may inform
clinical treatment, and it may allow earlier treatment.
The
committee recommended that this type of monitoring be performed at
approximately a 3- to 6-months interval.
It was thought that this should be done on an active basis, rather than
archiving of samples. And, obviously,
if there is no vector positive cells in the peripheral blood, then there is no
need to perform this monitoring. But
the committee recommended that each protocol needs to develop a monitoring
plan, including trigger points, for additional analyses.
And,
finally, the committee left a caveat that if a particular sponsor felt that it
wasn't justified to do this monitoring in their clinical trial, then the FDA
should consider this, obviously on a case-by-case basis.
Regarding
vector design, the question here was whether or not you could increase the
safety of retroviral vectors by minimizing the effect of an enhancer to
activate neighboring or distal genes.
And while everybody on the committee felt this was an important research
question and made the recommendation that it should be further studied, nobody
felt that this was something that needed to be changed now for clinical trials
to proceed.
And,
in addition to that, it was strongly recommended that preclinical models be
developed to assess the risk of vector insertion for new vector designs.
Now,
following the meeting in October, CBER then sent out letters to sponsors
requesting first of all that all sponsors using retroviral vectors revise their
informed consent, and we actually have specific template language that we
recommended in that letter.
In
addition, we asked that, in a subset of those trials using CD34 cells, sponsors
submit plans for monitoring for integration clonality, and the interval that we
recommended was every six months for the first five years, and yearly
thereafter for the next ten years.
And
then when a predominant clone is identified, that there be a second test within
three months from the first, that the sequence be determined, and that you
monitor the subjects closely for signs of malignancy.
So
to summarize then, there were three sets of letters that were sent subsequent
to the October meeting. In the clinical
trials in SCID, which were the subset which were on hold at the time we met in
October, we required that they revise their informed consent and develop plans
to monitor clonality in order for those trials to proceed.
In
indications that use hematopoietic stem cells or other stem cells, these two
conditions were recommended, but not a requirement. And in all other retroviral vector clinical trials, we requested
only that they revise their informed consent, and at that time did not
recommend developing plans for monitoring clonality.
And
we confined this to hematopoietic stem cells, this issue of looking for
clonality, based on the idea that stem cells are by their very nature
long-lived, with high proliferative capacities, and therefore more at risk to
the effects of vector integration mutagenesis.
Now,
as you know, in late December, we received a second report from Dr. Fischer
that there was another subject in his X-SCID gene therapy clinical trial that
developed a leukemia-like illness at 34 months post treatment.
And
subsequent to that initial report, preliminary data was provided to us by Dr.
Fischer that there seemed to be, again, a monoclonal retroviral vector
integration 5' to the LMO-2 locus, which I am sure you recall is the same
locus, but a slightly different site within that locus, that was observed in
Patient No. 4.
And
so these preliminary data suggested that we were probably looking again at an
incident where retroviral vector integration was likely playing a role in the
T-cell expansion.
So
in response to these data, we took the following actions: We again sent three sets of letters to
sponsors. In this case now, we changed
the issues of informed consent and clonality -- monitoring clonality plans to a
requirement.
In
other words, all clinical trials that used hematopoietic stem cells as their
target for ex vivo transduction were now put on hold until they met these
conditions.
Inactive
trials that use hematopoietic stem cells were told that if they ever wanted to
resume their trial, that again they would need to meet these conditions. And then all other retroviral vector
clinical trials, we didn't put these on hold, but we made a recommendation that
they now would also need to develop plans to monitor for clonality.
Now,
what are the clinical trials that we are talking about? In terms of target cells, you can see that really
fully half of the current active clinical trials are in either CD34
hematopoietic stem cells or bone marrow cells.
The
next largest category are in lymphocytes of various types. Then we have a few
in fibroblasts. The other category includes smooth muscle cells as well as a
number of different tumor cell types.
And
then we have two each that are either direct administration of vector producer
cells, or of the retroviral vector itself.
In terms of indication, I have broken this down for you two ways. One by total active clinical trials using
retroviral vectors, and in the blue bars, this shows that subset that are in
the CD34 bone marrow target cells.
So
in cancer, we have 8 out of 28 total trials using CD34 cells for the ex vivo
transduction, 8 out of 12 in HIV. The
miscellaneous, these two are osteogenesis imperfecta and multiple sclerosis.
And
almost all of our trials in genetic disease target CD34 cells. And these include, of course, the SCID
indications, chronic granulomatous disease, and Fanconi's anemia.
So
at this juncture then, it is obviously prudent to ask whether or not there are
additional modifications that we need in order for these types of clinical
trials using retroviral vectors to proceed safely.
And
what I would like to do for you now is to just outline some considerations,
some which are more theoretical and would require more research before they
could be immediately implemented in clinical trials, and others which are
potentially more practical and could be implemented more directly.
So
the first, which is a more practical solution, is again to revisit the issue of
dosing with the idea that if you reduce the total load of vector integrants
that this reduces the risk of integration into a potentially, quote, "bad
locus"; a locus that might be tumorigenic.
And
one could envision doing this by reducing the dose of vector used in the
transduction, reduce the dose of cells given back to the patient, or
potentially changing the dose so it is based on a total number of vector
integrants.
In
addition, as was recommended by the committee in October, we want to consider
whether or not we might need to have additional preclinical studies to assess
the carcinogenic potential of a particular vector backbone-transgene target
cell combination.
And
there is one of two ways that one could envision doing this. One is to perform traditional
carcinogenicity testing at an earlier stage of clinical development. This type
of testing is usually done at the time a sponsor gets to licensure.
And
the reason for that is because these are multi-year, very expensive
studies. So we don't usually ask people
to do this for a Phase I trial.
Alternatively,
one might consider some of the newer accelerated models of tumorigenesis, such
as transgenic models carrying oncogenes or knockout models of tumor suppressor
genes. One might also consider a
complementary approach of both assays. One might consider doing these
concurrently with an early phase clinical trial.
In
terms of cell target or culture conditions, again these are much more on a
theoretical, but again coming back to if we could identify what is a true
hematopoietic stem cell.
One
issue that is acknowledged regarding retroviral vector or retroviral
integration in the genome is that it tends to occur in sites of
transcriptionally active genes.
So
if you could identify a transduction protocol, for example, by studying gene
expression by gene or protein microarray that has a fewer number of
transcriptionally active genes, this might reduce the number of integration
targets.
And
then, ideally, if you could actually identify cells with vector integrants into
known tumorigenic sites, this obviously would be nice to be able to do, but
clearly on the realm of way theoretical.
In
terms of modifications of the vector, again, these are things that are in the
research phase. People are starting to
look at the addition of insulator sequences.
These
have really been done more to look at the ability of these sequences to
insulate from the effect on the enhancer becoming silenced, and it has not
really been studied whether or not these elements would also have the effect of
blocking enhancer activation of neighboring genes.
But
that is something that probably should be studied. Deletion of retroviral vector enhancer elements within the LTR
would clearly reduce the risk of enhancer activation of neighboring genes, and
if you could develop a vector with targeted integration, this would be ideal,
but again much more on the theoretical.
And it is not known at this point whether or not specific transgenes
might also play a secondary role in the tumorigenesis.
So
I want to finish then with recommendations from other advisory committees. The first is the NIH Recombinant DNA
Advisory Committee.
They
have had two meetings on this topic. The first was in December of last year,
and the second was just earlier this month on February 10. And they made the following observations: The majority of children in this X-linked
SCID gene transfer study have had major clinical improvement to date.
The
gene transfer was a cause of both leukemias and the occurrence of leukemia in
this protocol is not a random event and constitutes an inherent risk in this
study.
So
based on these observations, the RAC recommended the following two main
points: Pending further data or
extenuating circumstances, retroviral gene transfer studies for X-linked SCID
should be limited to patients who have failed identical or haploidentical stem
cell transplantation.
And then secondly, there are not
sufficient data or reports of adverse events directly attributable to the use
of retroviral vectors at this time to warrant cessation of other retroviral
human gene transfer studies.
Such
studies may be justified contingent upon appropriate risk/benefit analysis,
accompanied by an implementation of appropriate informed consent and monitoring
plans.
The
French gene therapy working group met at the end of January of this year. They
have recommended that the X-SCID clinical trial maintain its clinical hold
status pending additional scientific investigations of the most recent event,
and they also recommended that safety of retroviral vectors should be improved
by, for example, deletion of enhancers, addition of insulators, and also by
development of relevant and predictable animal models.
Germany's
Commission for Somatic Gene Therapy has also met twice to consider these
issues. In their most recent meeting,
they went case by case through the active clinical trials using retroviral
vectors.
Based
on that analysis, they recommended that one protocol using hematopoietic stem
cells for the treatment of chronic granulomatous disease remain on hold pending
additional data, while the other four active protocols were recommended to
proceed, obviously requiring changes in informed consent to make patients and
their families aware of these events.
And in some specific cases, additional protocol changes were recommended
regarding patient inclusion criteria and so on.
Italy's
National Health Institute has recently come out with a continued ban on all
gene therapy for an additional four months, but they do say that they may
approve trials on a case-by-case basis. Likewise, the U.K. Gene Therapy Advisory
Committee is meeting in March of this year.
They are currently looking at trials on a case-by-case basis,
considering particular circumstances for each situation.
So,
finally, I just want to quickly go through the questions for the committee, and
the first question is specific to the subset of trials in SCID indications.
Please
discuss under what conditions clinical trials using retroviral vectors to
transduce CD34+ hematopoietic stem cells for the treatment of SCID may resume.
Currently,
before sponsors of these trials may proceed with clinical trials, they need to
provide a revised informed consent document and plans for monitoring of
peripheral blood cells for the clonality of vector integration.
So
the specific question then we have, is this sufficient, or should additional
conditions be placed on these trials. We ask you to consider whether dose
should be altered, whether we need to include additional pre-clinical studies,
whether we need to look at the particular target cells, or have alterations in
the vector design.
The
second question is identical to the first, so I won't read it, with the notable
exception that we are now asking you to consider really these same issues in
other clinical indications where retroviral vectors are used to transduce CD34+
hematopoietic stem cells.
And
then the third question regards the use of retroviral vectors for marking
studies where no direct therapeutic benefit is possible, whether or not these
should be allowed to proceed, again, considering issues regarding risk/benefit,
a particular vector design, or target cells.
And
then the final question, if time permits, that we would like you to consider
is: Given the properties of lentiviral
vectors to transduce and integrate into non-dividing cells and their increased
efficiency of transduction, please compare the current requirements for
clinical use of gamma retroviral vectors to those that should be in place for
use of lentiviral vectors.
We
currently are requesting that sponsors revise their informed consent and
monitor peripheral blood cells for the clonality of vector integration. Is this sufficient or should additional
conditions be placed on these trials?
So,
with that, I thank you for your attention.
I am going to ask that the committee hold questions after my talk so
that we can continue with our guest speakers, and there will be plenty of time
in the afternoon to ask myself or other members of the FDA questions about what
we have done. Thank you.
CHAIRMAN
SALOMON: Thank you very much,
Carolyn. That was excellent. Before we start with the guest presentations
this morning, I would like to go around the room and have everyone briefly
introduce themselves.
I
apologize for not having done that earlier.
It has just gotten a little mixed up, as we were here yesterday in the
same room, but it was a different group.
So, Rich, could you start us off.
DR.
MULLIGAN: I am Rich Mulligan from
Harvard and Children's Hospital, and my expertise is in gene transfer and in
stem cells.
DR.
ALLAN: I am Jon Allan from the
Southwest Foundation for Biomedical Research, and my expertise is in retroviral
pathogenesis in non-human primates.
DR.
KURTZBERG: I am Joanne Kurtzberg from
Duke University. I direct the Pediatric
Bone Marrow Transplant Program, and my expertise is in stem cell
transplantation and cord blood transplantation.
DR.
TSIATIS: I am Butch Tsiatis. I am from
North Carolina State University, and my expertise is biostatistics.
DR.
MURRAY: I am Tom Murray. I am from The
Hastings Center, and my expertise is in the ethics of research with human
subjects.
DR.
MACKALL: I am Crystal Mackall, and I am
from the Pediatric Oncology Branch of the Intramural Program of the NCI. I practice pediatric oncology and study
transplantation immunology.
DR.
COFFIN: I am John Coffin from Tufts
University and the National Cancer Institute.
My research interest is in molecular retrovirology.
MS.
LAWTON: I am Alison Lawton. I am the
Industry Rep., and I am head of regulatory affairs for Genzyme Corporation.
DR.
RAO: I am Mahendra Rao from the
National Institute on Aging, and my interest is in stem cells.
CHAIRMAN
SALOMON: Dan Salomon, from the Scripps
Research Institute. I am in organ and cell transplantation and
xenotransplantation. We do gene transfer studies as well.
MS.
DAPOLITO: Gail Dapolito, FDA, Center
for Biologics, Executive Secretary for the
committee.
DR.
HARLAN: I am David Harlan. I am an
intramural investigator with the National Institute of Diabetes, Digestive and
Kidney Diseases, and my interest is in transplantation immunology in diabetes.
DR.
HIGH: I am Kathy High. I'm at the
Children's Hospital of Philadelphia, and my interests are in gene transfer for
hematologic disease.
MS.
LEONARD: I am Warren Leonard in the
National Heart, Lung, and Blood Institute. My lab discovered the genetic defect
in X-linked SCID, JAK-3 deficiency, and IL-7 receptor deficiency, and my
expertise relates to gamma-c-dependent cytokine interactions.
DR.
ROSE: Stephen Rose. I am in charge of
the recombinant DNA activities in the Office of Biotechnology Activities in the
Office of the Director of NIH, and Executive Secretary of the NIH Recombinant
DNA Advisory Committee.
DR.
RASK: Cynthia Rask from FDA, in the
Clinical Evaluation and Pharmacology/Toxicology Division, in the Office of
Cellular Tissue and Gene Therapies.
DR.
WILSON: Carolyn Wilson in the Division
of Cellular and Gene Therapies.
DR.
NOGUCHI: I am Phil Noguchi, Acting
Director of the Office of Cellular, Tissue and Gene Therapies.
DR.
PURI: I am Raj Puri. I am the Acting Director of the Division of
Cellular and Gene Therapies.
DR.
CORNETTA: I am Ken Cornetta from
Indiana University. My interest is in retroviral gene transfer, and I
coordinate the National Gene Vector Lab for the NCRR, and I am also a clinical
bone marrow transplanter.
DR.
FRENCH: Jeff French from the National
Institute of Environmental Health Sciences.
My interest and expertise is in alternative models for studying
carcinogenicity.
DR.
WOLFF: Linda Wolff from the National
Cancer Institute. My expertise is in
retroviral pathogenesis in small animal models.
DR.
TORBETT: Bruce Torbett from the Scripps
Research Institute. My interest is in HIV vector design as well as myeloid
transcription regulation.
MS.
MEYERS: Abbey Meyers, President of the
National Organization for Rare Disorders. I am the Consumer Rep.
MS.
BALLARD: I am Barbara Ballard. I am
here to represent the SCID families, and I am also on the Board of Trustees for
the Immune Deficiency Foundation.
CHAIRMAN
SALOMON: Just a point for those of you
who are not used to it: when you are
done speaking, if you will shut the mic off, it prevents feedback from
happening. Thanks. So if you see me doing something like this,
it is not, you know, be quiet, it's to shut your light off.
Okay. Let's get started then. It is my pleasure to introduce our first
guest speaker from the Hospital Necker, Marina Cavazzana-Calvo.
DR.
CAVAZZANA-CALVO: Good morning,
everybody. First of all, I would like
to thank Dr. Carolyn Wilson and Ms. Dapolito to give me this great opportunity
to share with you our updated results concerning all the trials and the two
side adverse events.
Nevertheless,
I would like to just make one comment before I initiate my talk. This protocol is under the authority of the
French government, and each public disclosure of this data must be made with
our approval. Thank you very much.
So
let me remind you that X-linked severe combined immune deficiency is
characterized by the complete absence in the peripheral blood of natural killer
cells and T-cells. This is due to the
fact that there is a gene mutation on the gamma-common chain that is shared by
IL-7 and IL-15.
The
gamma-common vector, retrovirus vector, we used is described here. The gamma-common cDNA is under the
transcription counter of LTR of the retrovirus, and we used an MFG vector
kindly provided by Dr. Richard Mulligan, and the classical psi-crip packaging
cell line set up by Olivier Danos.
The
envelope of this retrovirus is an amphotrophic one, and no other relevant
characteristic of this retrovirus vector can be underlined.
So
I resumed here the pre-clinical studies that we conducted in order to obtain
the approval through the clinical trial.
First
of all, we have demonstrated as have two other groups in the world, that the
B-lymphocyte transformed by EBV, derived from the patient and the gamma-c
negative, can be efficiently transduced by our retrovirus vector.
This
demonstrates the feasibility of protein expression and the function in terms of
gamma-c transduction signaling and the stability of the retrovirus expression
over time. This cell line has been
followed over six months.
The
second step was to demonstrate almost in vitro that the CD34 positive cells
gamma-c negative, obtained from the patient at the time of general anesthesia
through the central line, can be efficiently transduced in vitro and can
restore, almost in vitro, NK and T-cell differentiation.
In
parallel, Gemmady Santos in our laboratory set up a knockout mouse model
without the gamma-common chain, and this model was indispensable to demonstrate
no toxicity. This is correction
selective advantage.
Just
some details on the animal model to implement the discussion. The bone marrow site was derived from the
donor gamma-c deficient animals. The
animals had been pre-treated by 5-FU and the whole bone marrow has been
transduced with a retrovirus vector very similar to that used in the clinical
trial, and for this model he carried a marking gene that is the human CD2
molecules.
The
recipient of the double transgenic --double knockout mice gamma-c deficient
animals was low irradiated.
This
is the survival curve of treated animals in comparison with non-treated
animals. Non-treated animals in the
standard animal facilities died within 15 weeks. Conversely, the treated animals are 100 long-term survival
course.
How
long have these animals been observed before sacrifice? For the primary transplantation up to 47
weeks and the animals show no toxic effect.
The same cells have been used from the primary transplantation of
eight-weeks-old aged animals to transplant secondary mice to demonstrate again
the efficacy of the transduction of the stem cells, and here again we obtained
a correction of animal disease with no toxic effect.
So
on the basis of this preliminary design completed by the translation medicine
to make a scale-up study, we obtained the approval from the French authorities
to go to the clinical study with this protocol.
Patients
were eligible for these trials when they have gamma-c gene mutation, of course,
and in the case where they have no HLA gene-identical familial donors, and the
presence of informed consent from the family.
The
protocol is the following one. Marrow
is harvested under general anesthesia and very small quantities of bone marrow
cells are harvested, around 50 up to 150 ml per child.
CD34
positive cells are selected by immunomagnetic microbeds, and pre-activated in
vitro for one day in the presence of the stem cell factor FLT-3 ligand, MGDF
and IL-3. I underline the fact that we
used very high doses of stem cell factor FLT-3 ligand following the protocol
described previously by Eve Sconis in the Vancouver laboratory, 300 milligram
per milliliter.
MGDF
was used at a nanogram per milliliter and IL-3 in very low doses.
After
this 24 hours of preactivation, the cells are transduced with a supernatant
containing the vector in bags precoated with fragments of fibronectin. And it is made each day for three
consecutive days. At the end of the
treatment, which began on Monday morning and finished Friday evening, the cells
are extensively washed and transfused intravenously into the patient without
any additional therapy.
These
are the 10 patients, the 10 newborn patients with classical SCID form, that
have been enrolled so far in this clinical trial. As you can see the age is under one year, and the severe adverse
event occurred in two patients, the youngest.
One was one month, and the three-months was without any infection at the
time of treatment. Conversely, all the
other patients had severe infection at the time of diagnosis
And
I would just like to stress that these two patients -- because I think it is
fruitful for discussion -- these patients had been admitted to the hospital
with a disseminated varicella-zoster infection which affected the central nervous system.
And
we know there is no way to obtain a definition that this varicella also
disseminates infection with the classical haploidentical bone marrow
transplantation.
In
the second case also there is lympthoproliferative disease with the spleen and
the lung affected, with a very, very poor prognosis for the haploidentical bone
marrow transplant.
Four
patients had maternal T-cells at the time of diagnosis, with graft vessels
soft-like lesion on the skin: this
patient, and this one, and these two.
And
two patients had an endogenous gamma-C process expression, and we tested before
gene therapy for the presence of transforming into a negative effect.
This
is the characteristic of infused cells for these nine patients, and so this is
the mean and the standard deviation.
Each
patient received, except for one patient that I will describe in detail, a huge
number of CD34 positive cells, 24 million per kilogram with a large variation
between the patients.
The
total gamma-C transfused cells is also very huge, with a mean of 17 million per
patient with a huge standard deviation, and the double-positive CD34 gamma-C
per patient is 9 million plus-minus 7, because there is one patient, Patient 6,
that received a very low number of CD34+ cells.
But
you can see that the B cell reconstitution is less good and the percent of CD34
gamma positive cells is finished one year after transplantation. So a discussion of the dose of this patient
can be very interesting.
The
proliferation rate for bone marrow cells is very high, and then you have a fold
increase in the number at the end of a manipulation of 6 up to 10-fold. And in particular, I'll describe the two
patients who experienced the side effects, P4 and P5 patients.
And
in these cases, the cells proliferated even more. The proliferation rate was up to 8 and 9.5 for these two patients
who were the youngest ones, and I think that for these newborn patients, aged
similar to these ones, that the biological characteristics of stem cells are
more close to cord blood than to bone marrow cells. And it is important to stress that for this discussion.
The
number of CD34 positive cells that they received was very high: 44 million per kilogram for the first one,
and the 42 million for the second one.
The total gamma-common positive cells was even more huge, 31 and
24. You can have here CD34 negative
cells, but active lymphoid precursor cells.
And
the double-positive hematopoietic precursor cells is up to 20 million per
kilogram for this patient, with a high proliferation rate.
What
about the kinetics of lymphocyte T-cell reconstitution in this different
case? This is the patient that we
followed actually, and this is P4 and P5 patients that have experienced the
side effects.
In
this case, the kinetics of T-lymphocyte recovery is quite light, and it begins
75 days after transplantation of the gene-modified stem cells. And they grow within the first three
months. They can recover a normal
number of T-cells that permitted the discharge of this patient from the
hospital.
Recovery
increases for the first year, and then it goes down, as is usual for patients
of this age.
Strangely,
for these two patients, the kinetics of the T-lymphocyte recovery is quite
different. First of all, the appearance
of T-cells in the peripheral blood is very fast. Within the first month, they recovered a high number of T-cells,
and the other difference is the shape of the curve. This table remained high over the time, and at this moment we
have no worry about this.
And,
abruptly, pretty much at the same time the number of T lymphocytes goes up, and
the patient is cured of the lymphoproliferation.
So
the characteristics of the transduced T-cells for all the patients enrolled in
this trial are the following ones:
normal count and subset distribution; normal repertoire, analyzed by two
technologies, immunofluorescence and immunoscope; and normal phenotype. The T-cells are the naive phenotype, not a
memory one. This is normal for a new appearance of a neurological system.
They
present a good thymopoiesis, with the presence of recent thymic emigrants in
the same number as normal patients.
This is another element for discussion for the comparison between
haploidentical bone marrow transplantation and gene therapy.
They
have a normal function, and by Southern blot analysis, they contain one copy of
a provirus per cell. NK cells after
gamma gene transfer, you know that this lymphocyte subset is missing in this
population.
And
we observed the correction for the first year after gene therapy, and then we
observed a decline over the time. And
it is quite comparable to that observed after haploidentical bone marrow
transplantation.
So
from a natural killer cells point of view, this result is very similar to that
obtained by bone marrow transplantation.
The good news from this clinical trial, and which was not expected at
all, is the correction of B cell compartment.
For
these children, we had stopped at six months after gene therapy the
immunoglobulin substitution, and they recovered a normal level of serum IgM
,IgG, and IgA antibodies.
This
is the follow-up data as of February 1, 2003.
These are the two patients with the adverse effects. The other one, the follow-up, is closer to
four years for the first two patients treated.
This
is the failure of gene therapy treatment.
This patients never restored a T-cell compartment. He has been grafted with a match unrelated
donor, and he is doing well. All the
other patients, the follow-up is variable between 1.7 years and down to less
than one year after gene therapy. All
of them are doing well, with a complete restoration of immunological function,
and at the end of this talk I will give you much more information about the
immunological state of all these patients.
Questions
about the gene therapy are how many cells were efficiently transduced to obtain
a T-cell compartment, the characteristics of the transduced cells, and the
duration of the immunodeficiency correction.
For
the first question, it is important for us to have a diverse repertoire of
T-cells because a restricted T-cell repertoire does not permit these children
to defend against infection. So the
T-cell repertoire after gamma gene transfer for all the children that restored
a T-cell compartment has been a diverse one, with no abnormalities detected so
far for the treated children, either by immunofluorescence or immunoscope analysis
of the CDR3 lengths.
The
other point is the integration of the transgene more than one year post gene
therapy. You can observe here that we
demonstrate once again that there is a strong selective advantage for T-cells
and NK cells over the other hematopoietic cell lines.
One
hundred percent of T-cells and NK cells have integrated and express the
transgene, and less than one percent, or around one percent of B-cells, but
this can be important for B cell reconstitution, and it is variable between 1
percent and 5 percent, and less integration for monocytes and polymorphonuclear
cells.
I
would like to stress that the polymorphonuclear cells that express the
gamma-common chain persist over the time at the same level that you can detect
a few months after gene therapy. So
stated as a concept, probably we have obtained a transduction of CD34
autorenewal of stem cells, or a very primitive one in any case.
Worries
about the T-cell reconstitution of these patients. This is a magnetic resonance imaging of the P5 thymus one year
after transplantation, kindly provided by Dr. Sorensen.
And
you can see, not very well, but there is a thymus, a sizeable thymus that is of
normal size. The other point is the
function of the thymus that we have studied by the investigation of the TREC. That is that an episome drives it from the
DDG recombination in the nucleus that
can be measured and tracked for the patient.
And
all these patients have normal thymopoietic activities. This is in contrast with the decline of
thymopoiesis over the year for the patient transplanted from a haploidentical
donor.
About
the duration of the correction of this immune deficiency, we have performed
some studies on the CD34 positive cells recovered one year after
transplantation for some of these children.
Here
we see the LTC-IC frequency in P2 and P4 patients 22 months and 30 months after
gene therapy. We have a normal
frequency of CD34 immature cells. And
five weeks after long-term culture and limiting dilution analysis, we have
detected a high number of gamma-c expressing CFU-GM up to five percent. This is another proof of the idea that we
have transduced some stem cells.
This
is the study about this patient, realized thanks to the great collaboration
that we have with Christof von Kalle's group.
We can see here this mirror of the high number of integration sites for
CD3 cells at 13 months after gene therapy for the P4 patient, and he has been
able to track the same integration site in the CD3, CD15, and LTC-IC on the basis
of the diagram that I presented previously.
So
we can say that in this trial we have transduced some T-cells,
polymorphonuclear cells, and the monocytes.
So the idea is that we can transduce the common lymphoid precursor cells
with common myeloid precursor cells.
And
if we can track the same integration site, this can lead us to conclude that we
have transduced pluripotent progenitor cells.
The
persistence of these effects up to two years after gene therapy and the fact
that Christof von Kalle has been able to detect the same integration site
permits us to conclude that we have transduced hematopoietic stem cells with
high proliferative capacity and probably with self-renewing ones.
Limitations
of gene therapy. We have had a failure
in a child with an enlarged spleen that received the VZV vaccination before
diagnosis, and the two side effects in two children.
This
is the situation for the first patient up to month 30 after transplantation. He
showed rapid T-cell development with the polyclonal repertoire, and the
development of T and B cells immune responses, including to varicella-zoster
infection at month 30.
Christopher
can detect about 40, up to 60, integration sites in T-cells, and is doing well
up to this date. What happened
after? He showed an increase in the
T-cell count, overall for the gamma-delta T-cell compartment and the TCR, this
particular clone of gamma delta positive cells, had a slight increase of 7,000
per microliter over the time and overall after the chicken pox infection.
Nevertheless,
after he cured this infection, the number of these clones continued to grow
during the summer, and at the end of August of last year, they went up to
300,000 lymphocytes per milliliter with evident clinical signs. At this moment we began the chemotherapy,
the classical one for high-risk acute lymphoblastic leukemia because we don't
have available at this moment the monoclonal
actibodies against this clonal proliferation, but now we have one for
him.
The
plan for this child is that he has been treated with a conventional
conditioning regimen this week, and he
is to be transplanted next week with a match unrelated donor, ten-out-of-ten
antigen identical.
The
analysis of this monoclonal proliferation -- and you know some data already --
is that he is a monoclonal gamma-delta T-cell clone. And he has a signature for the coming of this clone from the
proliferation of one single cell, because, both by immunoscope and by TCR
sequences, all the cells have the same TCR.
The cells have the appearance of blast cells. They are extremely mature because they have only the marker of
gamma-delta mature T-cells of a memory phenotype.
They
are CD3, 5, 7, 28, and 45RO positive, and they all express gamma-c, and they
don't express any antigen for immature cells.
In vitro, they proliferate in the presence of IL-7 and IL-15. And these cells present chromosomal
abnormalities with a translocation of 6 and 13 at the time of the
treatment.
And
the first question raised by the authorities and by everyone in the scientific
world of gene therapy was the detection of the replication of competent
retrovirus. There is a
contamination. And we have performed --
these children are forwarded for six months for the detection in the biological
fluid of RCR, and all the detections made are negative, of course.
And
so we performed the classical mobilizing test on the master donee, and Philippe
Leboulch in Boston helped us with the match with other tests because we were
afraid that the test was not sensitive enough to detect some competent
retrovirus.
So
he did a Southern blot analysis. This
is the patient, the P4, and this is the B cell count. We then entered a probe and an RT-IN probe, and in all the cases,
he was unable to detect any RCR.
And
the question arose from our authorities and even in the first meeting that we
had with you about the possibility that at the time of the production of a
retrovirus some murine VL-30 retrotransposon are packaged with the retrovirus.
So,
again, Philippe LeBoulch in Boston helped us with this test. We sent him the cells, and he was unable to
detect VL30 in the blast cells of this patient with this probe.
So
these cells have one provirus integration site detected by LAM-PCR in
chromosome 11 in the short time within the LMO-2 locus. There is another expression of LMO-2, and
this integration site is detectable at least from month 13 and it is not
detectable at all in the CD34 positive cells, but it is normal.
We
have freed some of these CD34 positive cells just at the end of the
transduction protocol, and we have sent some cells to Christof. But probably the technology is less
sensitive, or is not sensitive enough to detect this integration site on the
CD34 positive cells. We can conclude
that the analysis, immediately after the transduction, is unable to detect the
"dangerous" integration sites.
This
is the structure as it is known so far for the human LMO-2 gene, and this is
the integration site for the P4 patient in the first intron in the reverse
position.
So
the question was: What is the mechanism
of hyperexpression of the LMO-2 gene?
And before speaking about the aberrant expression of this gene, this is
the sequential immunoscope study of the TB delta one population for this child.
And
you can see here that for the SCID disease where we are required to
reconstitute or to restore the immunological compartment, you can follow this
patient, or this type of patient, by immunoscope.
You
can see here the growth and distribution of the gamma-delta T-cell repertoire
for the control people. This is the
situation of this patient at month six, and you can see here that
retrospectively, we can detect a very, very mild incrementation of the size of
these TCR, 11 percent.
But
this clonal type increases much more between the 6th and 13th month after gene
therapy, up to 70 percent. But much
more than an increase of this clone, we can observe the decrease of
polyclonality of the gamma-delta T-cell population.
So
the much more striking data is the loss of polyclonality, more than the
appearance of a clone. And over time
this clone increases, at month 17 up to 52 percent, and you can follow this
clone. This is the only one at month 34
after gene therapy.
And
these results by immunoscope are strictly concordant with the analysis made by
Christof von Kalle of this type of integration site. So I think it could be alternate way to follow the immunological
reconstitution of this patient. And we can roughly build this type of curve
where we can see that this clone increases over time in a linear way, and that
it abruptly goes up after the chicken pox infection.
If
you come back to the aberrant expression of this oncogene, we have made a
quantification of the LMO-2 RNA messenger transcript in the patient's
peripheral blood leukocytes by real time PCR.
The
LMO-2 transcripts are ten times greater in patient cells versus normal control
cells. You have here the patient, and
this is the normal control industry standard.
And as you can see, slight contamination by monocytes in the peripheral
blood leukocytes can give a positive result.
This
is -- the question was: Is LMO-2
hyperexpressed by the same allele that has been integrated by the
provirus? And the answer is yes. This is the RNA-FISH study for the P4
patient, and there is a co-localization of the gamma-c probe and the LMO-2
probe.
This
is the gamma-c probe in the red, and this is the LMO-2 detected with the green
fluorescence probe, and there is a co-localization of the two in the same cell.
The
other question was: Is there an
aberrant splice of the RNA messenger from this integration? And the answer is no. Only one significant RNA species of the
respective size for the provirus on SCID is detected by Northern blot analysis with two different probes.
And
the reason for the normal splicing of the RNA messengers, despite the
integration of the provirus within Intron 1, is that in this site there is the
same splice locus that is present in the physiological intron.
This
study has been performed by Philippe Leboulch with our help.
We
did help out with the greatest research in the world that has studied the LMO-2
gene. He is permitted to us to be with
him in the UK. We have conducted a
study on the LMO-2 protein expression by Western blot analysis, and you can see
here that we have a tremendously high expression of this protein on the patient
P4.
And
it is equivalent to what we can detect in murine erthyroleukemic cells and very
comparable to that obtained in the CHO cell line, transected with the LMO-2
plasmid.
So
for the mechanism of LMO-2 activation by integrated provirus, we arrived at
this conclusion: RNA of the normal size
contains both the first and last exons and the correct junction.
LMO-2
RNA is monallelic. There is
Cis-activation by provirus of a normal endogenous LMO-2 promoter with a normal
splicing of Intron 2. Two possibilities
still remain, but it is much more likely that the first one is the correct one,
that there is a Cis-activation by the proviral LTR announcer.
And
even if at this point we can't exclude it completely, there is a disruption of
a provirus LMO-2 silencer with normal
slicing of Intron 1.
This
second possibility is under study and in collaboration with Dr. Kathleen
Anderson at Cincinnati University.
So
what about the overall interpretation of the side effects for Patient 4? The crucial point is insertional mutagenesis
with the aberrant LMO-2 expression. But
we are always looking for additional factors, such as aberrant clonal gamma-c
signaling, the role of varicella-zoster infection, and genetic associativity to
the cancer.
What
about the gamma-c expression? This is
the same as we obtained in the knockout animals treated by gene therapy, and
you can see here that it has been deeply investigated by us that the expression
of this protein on T-cells, B lymphocytes, and the natural killer cells is
strictly normal.
And
that there is no hyperexpression in the membrane of this protein. What about -- but we can have normal
expression of the gamma-c chain and the hyperactivation of the signaling
pathway, but we have no JAK-3 phosphorylation detectable in vivo.
This
is the control cells, and we can have the phosphorylation of the JAK-3 tyrosine
kinases exclusively after activation with the appropriate cytokines IL-7 and
IL-15. This is the control cells for the patient, and if we have no activation
in the steady state, just when we bring out of the body the cells, and we have
phosphorylation of the JAK-3 tyrosine kinases after simulation. And this is the control.
So
far we have no overexpression of gamma-c common chain. The sequence of the provirus of the cDNA is
strictly normal. We can't detect any
abnormal activation of JAK-3 Stat5 activation, and the study of Stat5, that it
could be much more sensitive than JAK-3, is pending. And in the blast cells of this patient, apoptosis is strictly
normal.
So
at the first meeting that we had with you and with Alain Fischer, we described
to you the pedigree of these families.
And something that everyone around the table found very interesting was
the fact that this family has two cancers, and one sister and one cousin of the
affected child. And we investigated at
least for this child the possibility that there is a genetic associativity to
the cancer.
So
we sequenced the p53 protein, the complex interesting in reparation of DNA as
the MLH1 gene, and we sequenced thoroughly the ATM gene, and everything is
normal as expected.
What
about the follow-up of Patient 4 because we are much more interested in the
clinical causes for this side effect.
This is the bone marrow of this patient at the end of January.
And
we can consider that this bone marrow is in complete remission, even if we can
detect some cells in the bone marrow after Fikol that still express the
gamma-common chain. And we can detect a
very low percentage, 0.1 percent, of the TCR gamma9. This is the TCR that is responsible for the clonal expansion at
the beginning.
We
gave these samples to Christof von Kalle, and he provided us with these
extremely interesting results that show that this child recovered a
polyclonality between the few T-cells he has.
He has no immunological reconstitution, of course.
This
child is now conditioned for his transplantation and he is doing well, but we
decided that theoretically the persistence of gamma-c positive cells in bone
marrow can be expected to restore or it could restore an immunological system
by these few cells.
But,
naturally, everybody prefers not to run any risk for the clinical status of
this patient. And on the basis of the
consideration that the appearance of this lymphoproliferation with the
characteristics of a high-risk one, we recommended to be as cautious as
possible and to perform the bone marrow transplantation.
CHAIRMAN
SALOMON: Was that the peripheral blood,
the flow cytometry you showed?
DR.
CAVAZZANA-CALVO: It is the same, 0.1
percent of this TCR gamma-9 positive.
CHAIRMAN
SALOMON: Is that a bone marrow sample?
DR.
CAVAZZANA-CALVO: This is a bone marrow
sample.
CHAIRMAN
SALOMON: But it was the same?
DR.
CAVAZZANA-CALVO: The same. We have some more details here. The malignant characteristics for this
patient are blastic appearance at the time of diagnosis, the presence of
translocation of 6 to 13, and the detection of the hyperexpression of the LMO-2
protein.
This
is all present at high levels at the time of the occurrence of this
disease. Two months later, after
high-dose chemotherapy, we have a complete disappearance of the blastic clone,
the disappearance of the translocation, but the persistence of a significant
number of T-cells that are hyperexpressing LMO-2 protein.
So
we decided to reinforce the obtaining of a complete remission because one month
after, the blastic cells can appear again, and we can again detect the
translocation. So we reinforced the
obtaining of complete remission with three more months of chemotherapy.
Actually,
we are in February, and this is 40 months after gene therapy and six months
after the occurrence of a leukemic effect, and we have no blastic cells, no
translocation either detected with a very accurate method.
We
have not done this exploration on the basis that we have 0.1 percent of
T-cells, and they are polyclonal in terms of the integration site. So even if we think there is a very, very
small quantity of gamma9 positive cells, this is less than the residual
leukemic cells normally detected in a leukemic patient.
The
therapeutic plan. You know we are at
month 40, the patient is under a conditioning regimen, and we have prepared
over six months monoclonal antibodies of a clinical grade in order to be able
to treat the residual leukemic cells eventually persisting in bone marrow.
We
have obtained this clone through a very kind company in France, and we have
produced in real time monoclonal antibodies against the TCRV delta-1. These antibodies are now finished, and we
have enough quantity to treat the patient in the next month.
We
have approval that these monoclonal antibodies can target this specific TCR,
and we plan to inject it as soon as we have received the test for eventually
the viral contamination of these monoclonal antibodies.
Patient
5 had gene therapy at three months of age, had a huge number of CD34 positive
cells infused, and is alive and well up to month 31 with multiple integration sites. He came to the hospital at 34 months with
splenomegaly, an enlarged mediastinum, and a huge number of white blood cells,
80 percent of blast.
And
chemotherapy has been initiated by Ricardo Sorensen without any delay. The marker for this Patient 5 is they are
CD8 TCR alpha-beta positive cells, gamma-c positive, no myeloid markers, and no
NK or B cell markers.
We
have -- and this is the greatest difference between the two patients -- 3 TCRV beta peaks, with only one integration
site. No proliferation is present with
the gamma-c dependent cytokines, another difference with the previous
patient. And the chromosomal
abnormalities appear at the time of diagnosis at trisomy 10.
I
would like to stress the fact that these chromosomal abnormalities are not
typical at all, even in the first cases, with the chromosomal abnormalities
that we can detect in typical ALL.
This
is the repertoire of the beta chain for Patient 5 at month 34. The peripheral blood still remains
polyclonal, but we have the emergency of three clones, Vbeta1, 15 percent of
the total and Vbeta2, 64 percent, and Vbeta23 that we can't detect at the
surface is 70 percent.
So
these three Vbeta clones make up the totality of the T-cell count in the
peripheral blood. And we have tracked
this clone by immunoscope in direct respective study, and you can see very
easily that at month 30th that we have a very diverse repertoire for these
clones. Vbeta1 and Vbeta2, there is no
worry about.
At
month 31, Vbeta2 is also polyclonal; no increase. Month 31 is September.
The leukemia occurred in December.
And we just -- this alteration in the immunoscope analysis lost the
polyclonality of the beta-1 family.
And
at month 34, we have 50 percent of this clone and 64 percent of this one. And thanks to the analysis performed by the
Funkel group we can detect the presence of the provirus upstream of Exon 1 in sense orientation in these
cases.
So
here again we have a normal hyperexpression of LMO-2 gene, with exactly the
same result in the P4 patient even. We
did an RNA-FISH study, where we can see merge between the probe for gamma-c and
the probe for LMO-2.
And
the other red point that you see is the gamma-c physiological gene, the two
alleles.
The
evolution of the P5 lymphoproliferation.
It is blastic, there is a trisomy 10, there is hyperexpression of an LMO
messenger, and he has three clones, two of them detectable by
immunofluorescence.
Everything
is present at month 34, and there is a disappearance just one month after the
chemotherapy. This is another
difference with the P4 patient: this
second case is much more sensitive to chemotherapy than the first one.
And
the medical doctor in charge of this child detected a disappearance of the
blastic cells, and a complete disappearance of the chromosomal
abnormalities. We can detect in
significant quantity the clone involved in this lymphoproliferation.
Now
we are up to 36 months after gene therapy, two months after the beginning of
the treatment. There is the
disappearance of the blasts and the chromosomal abnormalities.
We
can detect some Vbeta1 and Vbeta2 cells that have the same integration
site. There is a very significant
decrease in terms of the quantity of cells, but we can't formally conclude that
this patient is in complete remission but has a normal course for a child who
is treated for acute lymphoblastic leukemia.
Just
to finish this talk, you have here the immunological analysis of patients with
T-lymphocytes, the other one that does well so far.
And
you have the months of follow-up here.
The first two patients are more than four years after gene therapy, and
this is the number of T-lymphocytes for the first patient treated.
And
the last determination was made yesterday, and he has 1,000 lymphocytes so
strictly normal, probably slightly decreasing over the time. This is the curve that you probably noticed
in the first kinetic T-cell reconstitution, that it dropped down much faster
than the other patient.
For
the other patient the lymphocyte count is strictly normal. This patient even -- this is the patient
with the sort of lymphoma proliferation at the time of the diagnosis that I
stressed to you at the beginning, and he had a varicella infection two months
ago.
We
hospitalized him because we were very worried about the varicella-zoster
complication, taking into account the first cases, but he was cured completely
from his varicella-zoster without any complication, and with a very mild
increase of the gamma-delta T-cell compartment that decreased over time after
the resolution of the infection.
And
this is the blood cell count for the other patient. In terms of activity, these cells proliferate normally to the
T-cell stimuli, such as the PHA anti-CD3 monoclonal antibodies, or antigens to
the tetanus toxoid and Candinine.
I
think that there has been trouble with the patient called by Christof Patient
A, and some worries in the scientific journals. This is the patient -- the follow-up of this patient as of
February 26th. He had a normal physical
examination, normal peripheral blood cell count, normal subset distribution,
and normal repertoire.
So
to conclude this long talk, just two or three slides on haploidentical
hematopoietic stem cell transplantation versus gene therapy for SCID-X1 patients.
Two
points to consider from my point of view.
Kinetics of immunological reconstitution: twelve months to obtain a protective number of the CD3 positive
cells versus three months for the gene therapy-treated patient.
This
is extremely important, because in the case of a patient that arrive at the
time of the diagnosis with a severe infection disease, this is the sort of run
gain where we normally lose because of the viral infection in comparison with
that.
So a faster immunological reconstitution
for CDF-6 patients is a very important parameter to consider. The second one is the quality of the
immunofunction, and always a long term follow-up can permit us to conclude
about this.
I
would like you to remember the European result of haploididentical
hematopoietic stem cell transplantation in an identical condition in a SCID
patient.
We
have as each one in the world an extraordinary improvement in the long-term
survival curve for patients with a B plus SCID form over the time, and this is
the time of the first transplantation in Europe.
And
we are now up to 18, and we can say 70 percent survival. All patients are confused, and so even the
patients that go at the time of transplantation and the patients have a severe
infection.
In
any case, you can have a poor T-cell function in some case with a partial
T-cell reconstitution and as reported by Dr. Blakely, we have in fact the same
result, and a long-term decline in T-cell function, and low NK cell count, and
infrequent T-cell immunity.
The
quality of the immunofunction, I feel we can make a comparison between
hematopoietic stem cell transportation and gene therapy. Or regards of the T-cell function, the time
created over 10 years is a decline in this patient, and we don't know exactly
why because we don't observe, so far, any decline in T-cell reconstitution for
SCID treated patients, is probably leaked infection from one side, and
incompatability, allogenic response against chemokapithalium thymopoiesis in
the other cases.
This
is the situation for gene therapy. The question is, are we able to transduce
stem cells to guarantee a long term restoration of immunological function in
this case.
And
each case the restoration is the same in all the cases, and low for
hematopoietic stem cell transportation, and low for gene therapy.
In
terms of B cells reconstitution, it is infrequent in this case, and frequent,
but, and as you know, we have a low figure.
This
is the gamma-c transgene persistence in a patient with CD34 positive cells, at
a different follow-up. For Patient 1,
we have only one data that amounts to six after gene therapy.
For
Patient 2, we have a two determination in the bone marrow, and positive at 5
months, and positive at 21 months after
June 30.
Patient
4 is still positive in spite of the chemotherapy, and so I think we have some
doubt on the fact that we have transduced some stem cells, and these doubts are
now finished. He has sample cells
detected at the same extent after 6, 13, and 39 months after gene therapy.
For
Patient 5, we have just one detection one year after gene therapy and not
evaluable at this time. We preferred to
privilege the detection of the malignant clone by integration site.
P6,
this is a patient that had an extensive varicella infection at the time of
diagnosis. He was restored to complete
immunologic function, but the very cells that destroyed the -- we know that
what fights the infection are very toxic for bone marrow, because of cells, and
at the time of the harvest of bone marrow, we can have very few CD34 positive
cells, in comparison to the other patients who are free of the virus infection
at the time at the time of diagnosis.
And
in this case the kinetics of the immunologic reconstitution was very slow, and
the patient has a very slow increase in T-cell number, and the CD34 detection
up to one year after gene therapy is negative.
So
in the debate on how many cells you must transfuse, these data can be extremely
important.
Patient
9, we only have one determination 5 months after gene therapy, and the patient
then is not evaluable because it is in Europe but not in France. And why there is an apparently increased
role of insertional mutagenesis in a SCID patient, we can assess the gamma-c
more than the interaction of the gamma-c with LMO-2, and that the role of every
block in that T-cell differentiation pathway with the accumulation of immature
CD34 cells ready to go.
There
is a massive proliferation of a transducer because of cells tend to selective
advantage, and probably we have an induction of gamma-c expression of function
in pre-CLP cells.
In
all of age, I think it could be very important in these cases with a distant
pattern of hematopoiesis, and the accessability of active gene loci. So
different -- gets a function of the disease and their agents. So phenotyping of gama-c negative cells
between CD34 positive cells between 3 months and over 3 months is under
investigation now in our laboratory.
And
gene inspection pattern is ongoing on the inspection of an proto-oncogene as a
function of the age, and integration sites as part of a falling gamma-c
transfer, and we are coming back to the gamma-c negative murine mammal with new
experiments in newborn mice.
This
is the possible identification that everyone would like to know, and lastly, I
would like to thank the large quantity of people that are studying in detail
these two side effects, and the follow-up of the patients treated.
First
of all, at the Necker Hospital, with Peter Cooper, Alain Fischer, Salima Hacein
Bey, and Francoise Le Deist, who permitted us to sort the immunological
reconstitution of these patients.
Out
of Paris, we have a great collaboration of LMO-2 expression studies with Dr.
Terry Rabit. And we have performed some
experiments in transgenic mice carrying this transgene; and Karen Osbourne and
Peter Fraser for the RNA-FISH analysis.
And
Philippe Leboulch and Roberta Powlack in Boston for the study of eventory
presence of replication of recombinant retrovirus, and RNA splicing of the
LMO-2 protein.
And
the VSV studies by Jeffrey Cohen in Bethesda, and Erika Avivi in France. And we have made, but have no time, to
explain all the data and transcription for the phy-level gamma delta T-cell
clone in relationship to the gamma-delta control T-cell made by Francois Cigaud
and Delain Rigas in Paris.
And
we make also the immunoscope analysis that doctor permitted to follow very
tightly, the patient treated by Annika Lim in Paris.
And
all the medical doctors that followed up the patients that were treated in
Paris, the patients elsewhere in the world, especially at Alexander in
Melbourne, Australia; and at Winterstein in Munich. And Ricardo Sorenson, that which the collaboration with whom is
very fruitful.
Of
course, I would like to thank the group of Christof von Kalle and Manfred
Schmidt on the work on the integration site.
And we are performing some studies on the cell cycle of B-cells in Paris
with Papadapaluas involved in gene study and the reparation of genes. Thank you very much for your attention.
(Applause.)
CHAIRMAN
SALOMON: It is obviously impossible to
cut discussion off at this point and go on to a break, but what I would like to
do is keep it focused for 15 minutes, and then go to a break at 10:00.
Otherwise,
we will not get to the important part of the discussion this afternoon, and I
feel responsible for that. So I would
like to open this very informative presentation on the patients for discussion. I had one -- just to start one
question. Is it Patient One then that
had the -- is it the third patient with an LMO-2 integration site?
DR.
CAVAZZANA-CALVO: Yes, I think it is
Patient One in our service.
CHAIRMAN
SALOMON: And that patient, if I
remember right, is around 3 to 3.9 years?
DR.
CAVAZZANA-CALVO: Four years.
CHAIRMAN
SALOMON: Four years. Okay. John.
DR.
COFFIN: A couple of things. I guess I just lost it as it went by, but
could you quickly indicate the relevant integration sites of the vector in
these three patients that have --
DR.
CAVAZZANA-CALVO: For the -- I know in--
the question is can I indicate very precisely the integration site for the
three patients, and this is the question?
DR.
COFFIN: Yes.
DR.
CAVAZZANA-CALVO: This first patient,
and I speak under the control of Christof von Kalle, who performed the study,
but for Patient 1, it is within the intron, and in spite of this has a normal
LMO splicing.
DR.
COFFIN: That is a common feature in
MLVs. It's not that unusual.
DR.
CAVAZZANA-CALVO: But we have it two
sites.
DR.
COFFIN: Yes, of course.
DR.
CAVAZZANA-CALVO: And for the P-5
patient, it is extreme, about 5 kb before the first exon, and the third patient
I know nothing in detail.
Dr.
Von Kalle: Okay. Maybe I can briefly
comment on this. As I have stated
previously, we have no indication that there is any lymphoproliferation
associated with LMO-2 integration in any other than the two patients that
Marina described.
The
data that we have presented was with regards to the chance of an LMO-2
integration into the vicinity of the LMO-2 locus and we have specifically
searched for such integrations, and we have found a couple of instances.
One
was located 40 kb upstream of the locus, and the other one was in reverse
orientation, about 2 kb upstream of the start codon of the distal promoter.
And
again we have no indication whatsoever that there is lymphoproliferation from
either of these clones. Of course, we
are looking closer with regards to patient safety in the other patients.
DR.
CAVAZZANA-CALVO: But I have a
comment. I think you can have one, only
one integration site near to the dangerous site. But the much more important criteria is the clinical one; the
physical examination of the number of peripheral blood cell count, and
immunoscope analysis, and the other characteristics because if I remember
correctly from the study of Don Kohn for ADA patients, there is only one
integration site, and there is only one in one patient with an extremely large
T-cell repertoire.
DR.
COFFIN: Yes, I would completely agree
with that point, but I think it is important I think to get on the table
exactly what we are seeing in the total set right now, so that we can get the
back of the envelope calculations if nothing else.
CHAIRMAN
SALOMON: Crystal.
DR.
MACKALL: Two clarification
questions. First off, I thought there
were 11 patients in the initial study.
DR.
CAVAZZANA-CALVO: Which patient?
DR.
MACKALL: I thought that there were 11
patients initially treated that were discussed last fall.
DR.
CAVAZZANA-CALVO: I think on the 11th
patient there was a compassionate treatment for a 15- year-old boy, because he
had an affected biology form, and he had a little T-cell repertoire that
permitted him to live in between a lot of virus, and parasitic infection, and
bacteria infection.
And
we described this and discovered that he had a gamma-c mutation very recently,
two years ago or something like that.
But the gene therapy treatment has been a failure because the child has
been largely infected. So he has no
restoration of T-cell function.
DR.
MACKALL: Okay. So 9 out of the 11 patients that received
the treatment had initial benefit at this point?
DR.
CAVAZZANA-CALVO: I think I prefer to
consider the newborn infants as a homogeneous group, and 9 of these were
successful. And in one patient, who was
15 years old, was also a failure.
DR.
MACKALL: Okay. And a second question. When you were showing the T-cell numbers on
the two groups, separating out Patient 4 and 5 from the others, it seemed to me
that those patients from 10 months or so on had about 10,000 circulating
T-cells. Is it clear that they did not
have super-physiologic levels of T-cells before the development?
DR.
CAVAZZANA-CALVO: It is very difficult
to answer, because as you probably know, a child less than one year has a
physiological lymphocytosis. So after
to 10,000 lymphocytes, an upper airway infection can determine lymphocytosis,
and this is considered normal.
And
even a small infection, a virus infection, upper airway infection can determine
a lymphocytosis. And these only after
one year that they showed the classical version of the cell hematological
number, with an increase in the neutrophil count and a decrease in lymphocyte.
This
is -- if you go see the identification tabs at 6 months late in the treatment,
you have a 12 months plus 6, and you
can consider that after or around 2 years, we can tolerate a number of
lymphocytosis, mild lymphocytosis, but it is normal in comparison to the age.
DR.
MACKALL: But they certainly had higher
lymphocyte counts than anyone else in this study even early on looking back
now?
DR.
CAVAZZANA-CALVO: Well, looking back
now, yes, you can say yes. But if you
have a newborn with 8,000 lymphocytes, what do you do with it.
CHAIRMAN
SALOMON: Rich.
DR.
MULLIGAN: Marina, two questions. On the kinetics of the T-cell recovery, did
I get that right; that those two patients, that they recovered their T-cells
much more quickly?
DR.
CAVAZZANA-CALVO: Yes. This is
impressive.
DR.
MULLIGAN: And is that different than a
person given a transplant, a bone marrow transplant?
DR.
CAVAZZANA-CALVO: Completely different.
DR.
MULLIGAN: Okay.
DR.
CAVAZZANA-CALVO: Never can we get two
cervical -- with haploidentical bone marrow transplants.
DR.
MULLIGAN: Okay. Secondly, the issue of -- is there a
different target cell for infection?
You mentioned potentially that there were CD34 plus cells, quote, ready
to go.
Can
you tell us anything you now know about the CD34 plus cells from those patients
before infection, versus normal patients?
Is there any sense that they are more replicating CD34 plus cells?
Is
there any strange characteristics? Do
you have a sense that after they are cultured under the conditions for
infection that they give different counts?
And
particularly LMO-2, I think, is supposed to be pressed in primitive
hematopoietic stem cells. Is there any
sense that these patients have more LMO-2 expression in their CD34 plus cells?
DR.
CAVAZZANA-CALVO: Yes, the question is
crucial and very interesting, but unluckily I have no clear answer to give
you. Lastly, I can answer that in this
patient the number of CD34 positives out of a viral infection is higher than
other bone marrow cells.
And
other bone marrow cells in the mononucleated fashion, and you have 3 percent of
CD34 positive cells, and in newborns, we had upwards to 10 percent of CD34
positive cells. So this is the first
great differences without, and I can't underline any biological differences
between the two.
And
the other one is the proliferative analysis, and for the scale-up protocol, we
have set up an experiment in cord blood.
And roughly for these two patients, the biological characteristics of
the bone marrow is much more closer to cord blood than the bone marrow
cells.
And
we can also say that to the other patients that are oldest have a less
proliferation during the transaction, but I am not sure that the difference is
significantly relevant.
I have no other data to share with you
about LMO-2.
CHAIRMAN
SALOMON: I need some help with two
technical questions. The first is, and
it is just me being ignorant, but I don't understand this proliferation rate
that you referred to. It had no units,
and so there was a 7.7 and a 9.5 in two patients.
So,
I apologize, but I just don't understand what that is.
DR.
CAVAZZANA-CALVO: It is a stupid
calculation, but you have 1 million cells and you have 10 million at the end,
and I say that you have a 10-fold incremental of the number itself.
CHAIRMAN
SALOMON: And so that is over what
period of time in culture?
DR.
CAVAZZANA-CALVO: The five days. I
explained that we began on Monday morning to purify the cells and injected back
the cells on Friday evening, Friday afternoon.
And so during this period you can from 5, up to 10-fold expansion of the
initial number of cells that are put in a culture.
CHAIRMAN
SALOMON: Okay. So maybe we will come back to that.
DR.
CAVAZZANA-CALVO: CD34 positive.
CHAIRMAN
SALOMON: Yes. And the other question that I had would be if I -- and again if I
got this right, these two patients got 44 to 40 million CD34 per kilo? I realize that they are small, and that
these kids were infants, but that seems to me an extraordinary high CD34 dose.
DR.
CAVAZZANA-CALVO: Yes, but per
kilo. But we come from the experience
in identical bone marrow transportation, and you must remember that during this
period that we know nothing about gene cells.
And all of the clinical trial so far realizing that the world was
negative in terms of results.
And
from the haplo condition we know that T-cell constitution is very slow. And
that even when we injected a mega dose of CD34 positive cells, in some cases,
although not in identical situations, you have a normal constitution.
And
so we were very worried about efficacy than toxicity at this time. So this is the reason that in face of all of
these proliferating cells that we injected back everything without knowing
anything about toxic effect.
DR.
COFFIN: Could I follow that up a little
bit? So do these two patients then get
more? I mean, how do these two patients
compare to the others? Were they the
ones that got the most cells?
DR.
CAVAZZANA-CALVO: Yes, sir.
DR.
COFFIN: And had the most rapid rates of
cell reconstitution?
DR.
CAVAZZANA-CALVO: Yes, sir. Correct.
DR.
COFFIN: Did they also get -- could you
compare the numbers of transduced cells?
DR.
CAVAZZANA-CALVO: They are much higher.
DR.
COFFIN: I'm sorry?
DR.
CAVAZZANA-CALVO: The higher --
DR.
COFFIN: These two were the two that had
the highest?
DR.
CAVAZZANA-CALVO: Yes.
DR.
COFFIN: So quantitatively how many
transduced cells were in these two patients compared to what in general was in
the others?
DR.
CAVAZZANA-CALVO: I can say that they
have two times the number of the other patients roughly.
DR.
COFFIN: So the average for the other
patients --
DR.
CAVAZZANA-CALVO: Except for P6, because
P6 is a strange patient -- We know the
toxicity of the various viruses on born marrow cells, and so we could not have
very few CD34 positive cells at the time of treatment.
And
this patient received around 1 million of transduced 34CD positive cells per
kilogram. And so 10 times less than the
other, and has a very slow T-cell reconstitution probably. And we are looking attentively for B cells
because the level of immunoglobulin is going down, and it is not perfect.
And
they have no CD34 positive set transduced detectable today.
DR.
COFFIN: I'm sorry to keep hitting on
this, but these numbers I think are going to become very important in our
discussions later on, and so I wanted to make sure that we were very clear on
them.
So
you said before the average total number of transduced cells per patient on
average is 17 million per patient? I
took that number.
DR.
CAVAZZANA-CALVO: No. There is 10 patients, and so we have 8
million and 20 million for P4 and P5, okay?
DR.
COFFIN: Okay. Total transduced cells.
DR.
CAVAZZANA-CALVO: Gamma-c transduced set
cells. The total transduced cells are much more. I think it is about double, about 40.
DR.
COFFIN: But successfully transduced
cells.
DR.
CAVAZZANA-CALVO: CD34.
CHAIRMAN
SALOMON: John, I calculated about 70
percent transduction.
DR.
CAVAZZANA-CALVO: No, it is not 70
percent. It is 40 percent.
DR.
COFFIN: I don't want twice as
many. I want to know what the numbers
are. That's what I am trying to get at.
DR.
CAVAZZANA-CALVO: But I think that your
comment is right, because in reality they received a huge number also of
gamma-c positive cells, CD34 negative.
And we don't know if they are committed for the precursor cells that the
other patients received less then.
DR.
COFFIN: All right. So just for either patient, either Patient 4
or Patient 5, once more, can we get the numbers. So the total for that patient, the total number of gamma-c
positive cells transduced in the whole population of transduced cells was
what? Was it 20 million, or --
DR.
CAVAZZANA-CALVO: Forty million.
DR.
COFFIN: Forty million.
DR.
CAVAZZANA-CALVO: The total number.
DR.
COFFIN: The total number of gamma-c
positive cells.
CHAIRMAN
SALOMON: John, just for the interest of
getting done here, can we break on that, and then during the break, which is
going to come in a minute, can we make some calculations together.
DR.
COFFIN: Yes.
CHAIRMAN
SALOMON: And then present it to the
group?
DR.
COFFIN: That's fine.
CHAIRMAN
SALOMON: So before the break, I would
like -- Joanne, did you -- and Warren, and Kathy, and Ken, you get the
last. And can we keep these kind of
short and brief, because I don't want to completely lose the track here, but I
do certainly appreciate how important this part of the discussion is.
DR.
KURTZBERG: I have a couple of
questions. One is did you change
anything about the separation of the marrow cells to select the 34 cells
between any of the patients?
DR.
CAVAZZANA-CALVO: Nothing. Everything is reproducible and we have made
the same conditions, exactly the same for all of the patients treated. And we obtained in term of a transaction of
a CD34 positive cell exactly the same results.
DR.
KURTZBERG: Did you look for EBV
infection in any of these patients?
DR.
CAVAZZANA-CALVO: Yes, negative.
DR.
KURTZBERG: Okay. And what happened to Patient 8? I lost track of that.
DR.
CAVAZZANA-CALVO: Patient 8?
DR.
KURTZBERG: Yes.
DR.
CAVAZZANA-CALVO: What is the problem
that you have with Patient 8, because I don't remember the all the patients in
this way.
DR.
KURTZBERG: I just thought that I saw Patient 8 missing from a lot of the
graphs, and maybe it was me. I can look
after.
DR.
CAVAZZANA-CALVO: It is narrow, but he
is doing well. In the kinetics -- well,
it is a patient that is not in France, and so it is impossible for us to solely
monitor the kinetic reconstitution.
CHAIRMAN
SALOMON: Kathy.
DR.
CAVAZZANA-CALVO: And also for Patient
5, the approximate kinetic strength is not so precise as this patient does not
live in France, and we cannot follow at the same time period of the
patient. This is the reason. Kathy.
DR.
HIGH: I wanted to ask you one question
about gamma-c subunits. And so I think
you showed one slide where you showed that the levels of expression, of protein
expression, were essentially normal of gamma-c. Is that right?
DR.
CAVAZZANA-CALVO: Well, even knowing
that for the other patients, normal or low.
DR.
HIGH: Normal or low for all patients.
DR.
CAVAZZANA-CALVO: I decided that the
best one is normal.
DR.
HIGH: Okay. And is the gamma-c subunit usually limiting for assembly of the
cytokine receptor, or is it the other subunit?
DR.
CAVAZZANA-CALVO: I have not performed
the study of this type, and I don't --
CHAIRMAN
SALOMON: Warren, why don't you answer
that? You have the next question.
DR.
CAVAZZANA-CALVO: Well, just a
second. In the EBV study, we quantified
the number of gamma-c receptor on each cell, and it was 150 gamma-c receptors
present.
And
the normal EBV cell line has up to 200 gamma-c receptors present. So this is the only answer we can give you,
and Dr. Leonard can give more of an explanation.
DR.
LEONARD: Yes. My question had also related to the level of gamma-c expression,
and whether perhaps Patients 4 and 5 had any more than the other patients.
But
related to the level of gamma-c versus the other cytokine receptor chains, I
don't think that anyone really adequately knows the answer to that, because no
one has ever done rigorous scat charts comparing with mononuclear bodies
comparing the level of each of the various components.
And
one of the underlying questions is whether gamma-c is overall limiting or
whether it is available in excess, and is there enough to go around for all of
the different cytokine receptors simultaneously, or is it perhaps limiting some
situations which would allow for competition?
And
the answers are really not rigorously known for primary cells, and particularly
if you are considering thymic precursor cells or early pre-genitor cells, and
certainly no one has done any experiments on those sorts of cells that would
rigorously address that sort of question.
DR.
MULLIGAN: Can I just ask him something
about this point, which is that there is a point where gamma-c isn't normally
on in the very earliest cells I would assume, and so wouldn't this -- there
definitely is a novel case here in principal, where the addition of the
gamma-chain to a cell that might be making or using another beta-chain of these
other cytokine receptors. Isn't that
the case?
So
you are introducing, you are having gamma-c at a point where it wouldn't
normally be.
DR.
LEONARD: All I can really say is that
when we were making our own gamma-c knockout nest with Paul Love, and looked at
early thymic precursor from wild type mice, they made a Northern blot with
identifying thymic promordial cells at the earliest points they could look at,
gamma-c was expressed everywhere.
So
we really never found in the thymus an early enough place where it was not
evident in the mouse.
DR.
CAVAZZANA-CALVO: And just a piece of
information. I don't know if everyone
knows that a transgenic mouse does exist for gamma-c that is under a CD2
promoter. And that is a little bit
later than ours, and the mice did not develop any leukemia. That is information just to complete your
information.
CHAIRMAN
SALOMON: Ken.
DR.
CORNETTA: I actually have a question
about the animal stuff that you just presented earlier. You said that you had in your animal model
study out to 47 months.
DR.
CAVAZZANA-CALVO: No, 47 weeks.
DR.
CORNETTA: So, 47 weeks. Okay.
47 months, I wish. How many
animals and what kind of analysis was done at the end to have confidence that
there was not a leukemic process going on?
DR.
CAVAZZANA-CALVO: How many animals we
studied after the 47 weeks, I don't remember, but I can check when I come back
home. And conversely I know what we
studied extensively is the thymus, spleen, gastrointestinal tract, and the
peripheral lymph node for each animal after the necropsy.
And
we studied these because as you know in gamma-c knockout mice, there is -- the
gastrointestinal lymphoid compartment is depleted. And the restoration of this compartment is a sign of good
restoration. So it permitted us to see
very small histological modification for the mice.
DR.
COFFIN: Just very quickly. The real question there would be how many
transduction events, how many integration events did you actually study in
total in those mice as compared to what you see in these patients?
It
would be interesting, and you probably don't have that information, but it
would be interesting to dig that back out again and see how that compares.
DR.
CAVAZZANA-CALVO: Yes, but there is a
gap in the sense that we performed no study on the integration of profiles in
the mice. I have no information. When we performed the study on the mice, we
didn't think to look at the integration site.
Sorry.
CHAIRMAN
SALOMON: Okay. The last question before the break, and then
we are going to have a break.
DR.
TORBETT: I just would like to ask Dr.
Leonard a question. He addressed the
question of where gamma-c is expressed, but I would like to know how early is
it expressed, and is it expressed in hematopoietic compartment? Getting back at Richard's question, because
what you are doing is transducing 34 cells at or in supposedly a very primitive
stage.
And
what I would like to know, getting back at this question of inappropriate
expression, at a stage that might be critical to send it on its way to an
oncogenic event.
DR.
LEONARD: We have not looked, and I am
not sure that anyone has looked really early in bone marrow derived cells. So I can't really answer.
DR.
MACKALL: I want to make a comment. I mean, early T-cell progenitors in the bone
marrow are known to be IL-7 receptor positive.
And so I presume that means that they are gamma-c now. Those are already
somewhat committed to a lymphocyte lineage.
DR.
CAVAZZANA-CALVO: I know that --
CHAIRMAN
SALOMON: We will get back to this. This is kind of like holding back a hundred
thoroughbred horses. I mean, there is
just a lot of brainpower around the table, and I respect that.
And
I wish that we just had hours and hours, but this is really where it ought to
go. I just think from the whole
committee and everyone here that I want to thank Marina for coming here.
I
mean, you had an adverse event, and you really handled it well. That is me speaking personally. You presented your data, and you shared it
with us in October, and you are sharing it with us now.
I
hope that you hear directly from me, and I just have a lot of respect for how
well you have handled it, to me it has been an example. To the whole world, how
gene therapy ought to deal with its problems, as well as its successes. Thank you for being here.
DR.
CAVAZZANA-CALVO: Thank you.
(Applause.)
CHAIRMAN
SALOMON: So, 10 minutes, guys.
(Whereupon,
at 10:08 a.m., the meeting was recessed and resumed at 10:29 a.m.)
CHAIRMAN
SALOMON: Okay. I would like to get started again. What we have planned now are two 25 minute
talks to further expand our database, and then we will go into a Q&A
period, and then an open public hearing.
My
recommendations would be to everyone to stay hydrated. We have been known to forego lunch, and I
have sort of the sneaking suspicion that may be necessary today as well.
So,
getting started again, I would like to introduce Dr. Claudio Bordignon from the
Institute of Scientifico of Raffaele.
DR.
BORDIGNON: Thank you. Thank you for this opportunity of sharing
our data. I have really preferred a
talk that is more oriented to analyze the overall data that we have available,
rather than getting into the scientific details.
Of
course, all the scientific details are here, and so if there is time, we can go
back to the specifics during the questions.
The scope of my presentation is really to review all the data that are
in our hands, meaning my group and in collaboration with those that are directly working on some of our projects;
retroviral vectors, hematopoietic stem cells, and peripheral blood lymphocytes.
And
to share the results of the initial analysis of the integration process and to
take a look at whether or not this is meaningful, and how much we need, and
what kind of direction we should go.
I
will be reviewing data from 21 independent groups, including pre-clinical
studies and clinical data. Two main
fields, clinical trials of gene therapy of ADA-deficient SCID. Our group, the collaborators in Brescia,
Luigi Notarangelo and others; and the collaborators in Israel, Shimon Slavin
and co-workers, and I have one slide from Fabio Candotti, who has been so nice
to give me one of the long term follow-up of the lymphocyte ADA studies and
making one of the points that I am trying to make at the end.
The
second set of group are pre-clinical and clinical studies of the use of the
suicide genes. This is an independent
group and there is a large European consortium founded by the European Union,
and that is allowed to study very similar parameters in different models and
different animal models for clinical and patients.
The
reason why I decided to include this data, if there is time, of course, is
because it is probably the largest communitive experience in the use of
retroviral vectors in hematopoietic stem cells and lymphocytes.
And
in addition to the large European consortium, there were collaborators from the
U.S. and from Israel, and from Japan.
The
first is ADA-deficient SCID. Of course,
it is a different disease than gamma-chain, but definitely we don't have the
time to review all the differences.
It
is sufficient to say that probably that the selective event that is described
in this type of disorder is probably not as pressing, as strong as it is in the
gamma-chain deficiency. Here the defect
is a housekeeping enzyme adenosine deaminase.
Now,
in order to have a reasonable evaluation of the risk benefits and this was one
of the points raised at the beginning of the presentation today, and in the
first discussion today, I would like very briefly to come back to the point by
Marina discussed in relation to the gamma-chain study.
Here the available treatment are HLH matched
transplant, and I will not discuss this, but I will come back to this
point.
Initially,
no identical transplantation, and the range in Europe has been updated fairly
recently in the EBMT in 2002. And the
results are really not encouraging.
Twenty-three percent overall survivor from the long experience. Of course, this has improved over time, but
in any single selected center studies, you don't get higher than 60 to 70
percent. And if this is as a result of
transplantation with conditioning.
If
you go to non-conditioning, without conditioning, then the largest series comes
from Dr. Buckley in this country, and it is about 53 percent.
Of
course, there is PEG-ADA available, but this I think is also somehow a
misconception in the general perception, because PEG-ADA doesn't really work in
every patient, and does not offer the same level of reconstitution.
And
if you look at the last survey by Mike Herschfield, who presented ESID in 2002
-- 83 percent is the survival of this patient, and 73 percent if you include
the patient with failing PEG-ADA, and then go on to receive the transplant.
So
these are the reference points, and what we are going to review as quickly as
possible is our ten, eleven years experience of gene therapy and deficient
bodies recombining immune deficiency, and this was mainly down at our center in
collaboration with the group in Brescia more recently, and with Shimon Slavin
in Jerusalem.
What
were the main milestones of this research?
In 1990, we published the pre-clinical data for what was available at
that time as animal models, and I will not discuss any of those data today.
In
1992, we started a combination of stem cells, meaning total bone marrow
actually, and the peripheral blood lymphocytes transduction, and this was
published back in 1995.
And
in '99, we published the first discontinuation of PEG-ADA in one patient. And in 2002, the more recent study based on
CD34, and so when I say stem cell here, it is selected CD34 in combination with
non-myeloblative conditioning, and this was also reported last year.
And
these are the 12 patients that are enrolled in the study, and with a different
protocols -- the PBL. There is not much
that I want to make in relation to this, with the exception of a couple of
relevant points.
The
patient who received the treatment of multiple injections, and we don't have
the total number here, but as Fabio conducted for this patient, it is still a
huge number of lymphocytes and a huge number of integration. This is relevant and we will come back in a
minute to the analysis of integrations.
The
patient discontinued PEG-ADA, and what happened in that sense went from about
10 percent, less than 10 percent, to nearly a hundred percent of the transduced
lymphocytes, and the curve continued.
And
together with this effect, the majority of the lymphocytes that were present
were transduced in increased numbers to increase the level of ADA, and the ADA
present in the transduced population and the reconstitution of immune
functions.
If
you look at this, this is the first comparison of the response, and if you take
a vaccine in this patient, and you analyze the response, you see that it is
definitely better than the HLA mismatched transplant and comparable to the HLA
matched transplant.
And
this the slide that I made and referenced several times. It is important for the total number of
lymphocytes that you see down here, and for the people that are not close in
the room, this is 10 to the 11th, and I am sure that Fabio will be happy to
comment on the duration, the number of integration and the survival of such
cells for 13 or 14 years now.
Of
course, please consider Patient 1 is on the original slide, and so this is
Patient 1 of the overall experience, and it is not Patient 1 in our study.
Conclusions
that I can draw at this point, and I apologize because I only gave you a quick
touch of what was studied, but all patients had a total wealth of normal growth
and development.
Gene
therapy with PBL stands for safe and efficacious and optimal, as compared to
hematopoietic stem cell gene therapy.
This is mostly due to the failure of the total population of the
peripheral blood lymphocytes to toxify the whole system.
So
although you have an immune constitution, you have a number of other elements
that are not optimal, at least if you compare to the data that you will see
with CD34 purified cells.
And
you have the restoration of lymphocytes polyclonal repertoire, and so it is
included in the repertoire, the protection of infection is pretty good.
A
very large number of transduced lymphocytes have been injected and have
survived for more than a decade, both in the NIH study and in our study. No apparent safety reasons are present to
reduce or contain the number of transduced lymphocytes that are injected into
patients.
I
wanted to make this point because the discussion on those integration events
and the total number of integration per cell and so on, came up into the
discussion, and if you look at the number, apparently for lymphocytes there is
no such concern.
The
CD34 positive study is very, very similar to what you have seen from Marina,
and the protocol was inspired by their study.
There are two main differences.
One is technical and it is related to how we do the transplant, and the
cell dose is much lower, the cell dose that is injected.
And
the patient -- well, it is about one log less, between 1 and 2 logs less,
depending upon the patient. The
patients are also conditioned with non-myeloablative conditioning with
Busulfan. You will see that this is an
ambitious definition, because actually one of the patients went into
myeloablation.
This
is the story of the last four patients of the 12 that I indicated in the
summary slide. And here is present are
the age of gene therapy, in months, and so you see the patient, with the
exception of the first patient, is slightly older.
And
this is the follow-up available as of today, or well, yesterday, or the day
before; 29, 23, 9, and 4 months. So the
full follow-up is not as long as the French study.
As
you see, some of these patients had already failed after transplantation. This is the total number of cells infused
total. And this is the dose per kilo,
and so you can have your idea. This was
particularly low and it is important to keep in mind that this is Patient 2 of
the hematopoietic stem cell, and you will see that this shows in integration a
number of other issues.
So
this is probably, I would say definitely the maximum dose. The percent of transduction ranges around 13
and 40 percent, and the degree of myeloablation.
As
I said, essentially all patients were maintained on the same dose, and at least
we tried our best to maintain the same dose, but the level of myeloablation,
depending upon the condition of the patient, was very different, and actually
this patient received myeloablative treatment.
This is the patient, and you see here that there is a profound
difference.
The
other patient actually recovered very quickly, and also this patient, I have
not updated the slides, but none of them needed to be transfused for platelets,
with the exception of these patient obviously.
I
think we figured out what was the clinical reason for this, and it is not too
relevant for today. How about the
correction of the immune defect? Well,
this has a level of a total account of lymphocytes, and the different lineages,
and as Marina described, in about 3 months you see the reconstitution of
lymphocytes.
Of
course, all these studies, the hematopoietic stem cell studies are done without
PEG-ADA, and so only gene therapy is responsible for this reconstitution.
This
occured B-Cells and T-cells, NK-cells, the different sub-population and so on,
and I will not show any of the other patients, because the story is essentially
the same. Naive cells, thymic
emigrants, and that is an indication of thymic function, and you see there is
nothing before, and then you go into the range of the age-matched control.
The
reconstitution is fairly convincing, and also the functionary constitution,
this is pre-gene therapy, and this is after gene therapy, and in relation to
the age-matched control, and that is the last --
And
you see that this is true for RPHA candidates, and so on and so forth, and this
is also for the correction of overall immunity, and you see here a different
type, and the level of IgG here, of course, the patient was using IgG and so
forth.
I
refer to pre-clonal, and the complete correction that we get with the
hematopoietic stem cell also relates to the metabolic defect. This is actually more relevant than if it
was normal, and it was perceived before gene therapy, and actually although we
never reached the level of normal individuals in the different cell lineage,
this more than sufficient to detoxify the system.
Again,
not through normal levels, but to levels that are very similar to the
heterozygous parents, and therefore, influential for the health of patient.
Now,
let's take a quick look to the engraftment, because this is probably in
relation to the total number of cells and the integration event. It is probably relevant to have a sense of
how the different cell doses are working for the patient.
This
is Patient 1, and these are the days in the range for these numbers. And T-cells are a hundred percent, and K,
and so on, and so forth. But also the
other lineages are pretty good even at a relatively long period after the
procedure.
This
is the second patient, and do you remember the patient who got the 0.9 dose,
the lowest dose, despite this low dose, selective pressure was sufficient to
get nearly a hundred percent of transduced T-cells.
But
in K-cells and B-cells, and all the other non-lymphoid lineages, are very, very
low. This patient, without the serious
adverse events reported probably was going to receive a second dose, but since
he is clinically well and doing fine, we decided to postpone a second
procedure.
Patient
3 is similar to Patient 1, and Patient 4 was actually receiving gene therapy
during the banned suspension that is ongoing in Italy, with the specific
permission to treat this patient on a single patient basis, is now in the phase
of reconstitution, and the numbers for the time look pretty good.
This
should not worry because we usually see the cells taking off after 3 months,
and the patient is in Saudi Arabia, and so we cannot do the controls all the
time.
But
the level of lymphocytes are climbing, and all the other patients are predicted
with the climbing of the level of lymphocytes to the proportion of new cells
should also go up.
Conclusion. A restoration of lymphocyte counts and
corrections of humoral and cellular response, and correction of the ADA and
metabolic defect, and this is what makes together with the full immune
reconstitution, and this was perceived better than the lymphocytes.
Multi-lineage
stable engraftment of the new cells, no adverse effects. Clinical benefit. PEG-ADA. How good is the
clinical benefit. How does this compare
with allogenic bone marrow transportation.
This data are due to the courtesy of Shimon Slavin, and collaborators
Memet Aker, and Shoshana Morecki.
The
have family that has obviously the same genetic background, a Palestinian
family, in which you can compare in that sense a normal individual, and an
ideal transplant, and gene therapy, because the family has all three cases.
So
this is Patient 1, and our Patient 1 from gene therapy, and the second sibling
is a healthy one, the blue one, and the middle is a patient four years after
umbilical cord blood with a full HLA match.
And
you will see that I am not going to argue that this is a bit better than this
or this, but in essence, with the difference of K-cells, all the different
parameters, the gene therapy is either the same or better than the transplant,
and often very close to the normal individual.
And
I am flipping very quickly for the second time through all the different
parameters, including the specific cell levels. So let's try to conclude from this comparison and from the rest
of the study.
All
patients are doing clinically well with normal growth and development. Gene therapy with CD34 cells, combined with
mild myeloblation, is safe and efficacious as a single therapy.
You
have multilineage stable engraftment, and restoration of the lymphocyte count,
correction of humoral and cellular defect, correction of ADA activity and
metabolic defects, clearly superior to mismatched transplantation, comparable,
or at least comparable to matched transplant.
These
are all the people who participated in my group in San Raffaele in Milano, and
there are a number of external collaborators without whom all the studies would
not be possible.
These
are the long term collaborators, with whom we started the vectorology, and the
initial studies. Now, let's go and take
a look at the preliminary data on the analysis of integration very, very
quickly, because these are definitely not complete data.
I
am sure that everybody here is familiar with the reverse PCR, and you can
essentially cut out, and amplify, and sequence upstream and downstream the
regions that are close, adjacent to the integration site.
And
you get this type of pattern. In T-cell
patients receiving hematopoietic stem cells, and this is Patient 1, and you
remember the good cell dose.
This
is the T-cells and all the different times, and here and there if you look carefully,
you may find an event, and this is the level of progression of transduced
cells.
Patient
2, you will remember the very low cell dose, and I apologize, as this is almost
impossible to read, but this are from -- two from the same patient, and you see
that there is some level of clonality.
Patient
3, again, is similar, and Patient 4, it has some level of clonality, but
certainly after reconstitution as we saw in every patient. So you can clone and sequence in a number of
different ways.
First
of all, you can clone the T-cells, and then you will produce a number of
clones, and then they are either single integration or at most a couple of
integrations and that would be related to the fact that they are not really
clone.
But
it is a clone with two integrations, but you can cut out and sequence the whole
thing. This is the study on integration
in peripheral blood granulocytes, and so this is the myeloid compartment.
Here
in all patients you see a limited number of clones, and that makes it easy
because you can cut out any one of these and sequence them all. So for this patient, I will show you that
they have the analysis on all the clones.
And
these are again in peripheral blood, and in bone marrow in different
lineages. And again you see fully
cloned, oligoclonal integration. This
is the patient who received -- and this is the only one I am going to show, the
patient who received peripheral blood
gene therapy.
And
as you see, this is 25 months after the last infusion, and 90 percent of the
cells are vector positive, and again you see a big smear with many, many
integrational doses, and a few of those are predominant.
If
you analyze this at different times, actually some of these switch, and so you
don't find the same immediately. How
can we do this, and how can we analyze integration. It is relatively simple.
You
have two possibilities. If you have
these discrete bands as you have seen in the granulacyte, then with the bands
you do direct sequencing, and with an algorithm that was prepared by our
bioinformatic people, you can go directly and analyze where it is on the
genome, if the region is known obviously.
But this is the case for the majority as you will see.
If
you are not in this situation, you can make a mini-library clone directly in
plasmid sequence, pick the positive one sequence and map the same way, and this
can be done with rubber, if that's justified, of course.
So
this is the preliminary analysis of 25 integration sites that for one reason or
another were selected because of the clinical predominance, because they were
appearing as more clonal in some patients, or in some phases of life in the
clinical follow-up of the patient.
These
are the number, the location of flanking regions and so on. So not containing genes are 11, and inside
known are predicted genes 70 introns and 20 exons.
The
draft genome region one, highly repetitive sequence, one; short
non-conformative sequences. We are
redoing the analysis of these four.
This is the analysis that I mentioned for the
granulocyte. This is in essence the
full feature of Patient 1 at a given stage.
These
are the number of identical clones identified, and this is the length of the
region, and this is the chromosome location, whether it is outside the gene,
inside the gene.
And
we are continuing with this analysis for all the other patients, and for the
different lineages. What can we
conclude after this? Not much really. Integration are highly pre-clonal in
circulating T-cells of three ADA SCID patients, Patient 1, Patient 3, and
Patient 4, and there is a single exception of Patient 2, but you remember
Patient 2 really got very, very few cells.
Several
different integrations are detected in granulocytes and other subsets, and
cloning of integration site and differentation to different subpopulation is in
progress. I will come back at the very
end of this.
Now,
in the last few minutes I will review the suicide gene therapy in hematopoietic
stem cell transplantation, and I apologize for those of you who are not
directly in the field of gene therapy, because at the speed I will be
presenting this data and the clinical protocol will probably not mean too much.
But
the purpose is to tell you that this is probably the largest study, both
pre-clinical and clinical levels, and therefore, I will show you the data from
the safety point of view.
Well,
why was this done? For the simple
reason that in allogenic bone marrow transplantation, T-cells that are present
in the graft really determine the outcome of the transplant in many ways.
If
you take the lymphocytes out, you get no graft-versus-host disease, no immune
reaction from the graft to the patient.
Unfortunately, when this was extensively utilized in the clinical
setting, this increased the risk of relapse, demonstrating that actually the
T-cells in the transplant to take care of the minimal residual leukemia
disease, or lymphoma, or other tumor.
When
you were doing the transplant, or we were going the transplant in a
conventional way, the idea was to find the balance between graft-versus-host
disease and relapse. This was done with
a total cell dose, but also with immune-suppressive agents: cyclosporine, methotrexate, and others.
Now,
it is so true that the lymphocytes are taking care of the leukemia that from
the middle 90s actually, the lymphocytes were extensively used to treat relapse
after transplantation in order to obtain maximum anti-leukemia activity,
unfortunately this was associated with significant graft-versus-host disease,
at least 11.
In
essence what you can do and what we did is to insert the gene in here so that
you can switch them off if the graft versus host disease runs out of control.
How
do you put it in and how do you select the cells through a transgene, truncated
form of the deltaLNGFR affinity receptor for the non-growth factor, and so that
you have the untransduced cells, and the transduced cells with a mixed
population, and these also contains the Swiss Ig, the thymidine kinase.
But
you cannot inject this, because you will only be able to kill those cells, and
this would still leave graft versus host disease. So thanks to the cell surface marker, you can fish out all the
cells and see how the protocol works.
The protocol is fairly simple I believe.
If
the patient relapses, you bring the donor of the bone marrow back to the
clinic, and you do a leukopheresis, and you get all the lymphocytes, and you
transfuse those, the transduced cells, and the little flag on the subsurface
marker with a monoclonal antibodies, and you select them all out, and then you
can give it for transplantation.
If
the patient goes into complete remission, great. If the patient goes into complete remission and develops
graft-versus-host disease, you can kill out all those cells by grancyclovir. This is the technology that is fairly
established, and was published in 1997 for the first time.
And
there are a number of groups throughout the world who are working on this. Now, you don't need to read all the names
and all the affiliations. Of course,
the majority of these as I mentioned is a consortium founded by the European
Union to demonstrate that this really actually works at the clinical
level.
What
is important is that there are some collaborators from outside the consortium,
again Shimon Slavin, and Phil Greenberg in this country, and Steve Kornblau
from MD Anderson, and a few others.
These
groups have been utilizing these tools both for pre-clinical models and for
marking studies, and for clinical studies altogether. Now, where are we in relation to numbers.
I
will not show you how efficacious this is.
This was not my point. The point
was not to find the right risk balance in this study, but to show you the size
of the study and what we can try to conclude out of this.
These
are pre-clinical studies all done in mice, utilizing human cells, human-mouse
chimera, so murine cells. And this is
the number of mice treated, 140; in the human chimera, 206; a total of 368, and
these are the total cell doses that have been reached.
This
is the follow-up in weeks, with several secondary and tertiary transplant
recipients. This is the total
accumulated time. The outcome after or
at the end of the study, all the animals were specifically controlled to check
whether there was anything abnormal in the hematopoiesis, and all the animals
appear to have a normal hematopoiesis.
So
the cumulative data on over 300 animals transplanted with the hematopoietic
stem cell, and transduced with delta-LNGFR-coding vector, revealed no adverse
event, with normal engraftment, persistence of differentiation of transduced
cells, secondary and tertiary successful transplants.
More
than a hundred of these mice were maintained for more than 20 weeks, and more
than 70 animals, including 16 recipients of secondary, were sacrificed over 28
weeks.
Risk
of oncogenic transgenic transformation by transduction with this vector system
is less than 1 in 10 to the 9th events is what we can say so far. What is happening in pre-clinical studies
supporting the safety of marking of T-lymphocytes with deltaLNGFR.
So
this summary was on hematopoietic and I hope I didn't confuse you. Hematopoietic, first, and lymphocytes
after. These are all done with
lymphocytes. This again is human into
mouse, 20 animals, mouse in mouse, rat in rat, and three long term dogs.
This
again are the total number of cells infused with the total cumulative dose, and
this is the follow-up in weeks, with a significant range for the dog. Of course, these are very precious experiments,
with a total cumulative follow-up.
Again,
the same condition. All animals were
analyzed for lymphopoiesis, and in this case it is written hematopoietic and it
should be lymphoiesis and no abnormality was observed.
So
no other toxic events related to the gene transfer procedure of the transgene
expression or differences in the ability to induce donor chimerism associated
with graft versus host disease were observed with this transduction system in
T-cells in 356 mice, 200 rats, and 3 dogs.
So,
let's try to again accumulate everything.
Studies supporting the safety of gene marking with a delta-LNGFR, a
total of 905 animals, 7,169 10 to the 6th for the number of transduced positive
cells, and the accumulative follow-up in weeks is 12,000 or so weeks.
And
the number of animals that were followed for over 20 weeks is 151; and for over
28 weeks, 74. In every single animal,
whether an hematopoietic stem cell was transduced for marking, or lymphocytes
were transduced for the graft versus leukemia approach, the hematopoiesis and
leukopheresis was normal.
The
analysis of 93 independent studies of human T-cells revealed no change in the
expression of markers of lineage activation of additional proliferative
capacity.
The
analysis of 102 independent consecutive transduction of human T-cells with two
different vectors, and a variation of the same construct, revealed that all the
cells remained strictly dependent on IL-2 for growth and survival.
These
are the clinical data. Twenty-three
patients treated with HLA identical sibling, so this is the graft versus
leukemia, these are lymphocytes only.
Eight are identical family donors, and these are the total number of
cells that have been injected, again you see here that we are in the 10th to
the 9th range, 105 times 10 to the 9, and the dose here is lower obviously
because the risk of graft-versus-host disease is much higher for this kind of
transplant.
Survival
of cells in patient months calculation.
The longest survival of the cells, the peak frequency that you see is
significant for the immediately post-transplantation period. And here are the cumulative numbers.
Again,
in the clinical study, not a single adverse toxic event, acute and chronic
related to the gene transfer procedure, or through transgene expression that
was observed during this trial, which involved the infusion of more than a
hundred-million cells generated by more than 15 independent in vitro
transductions.
What
do these data suggest? The data are
available to suggest that PBL gene therapy does not carry an increased risk of
tumor transformation.
Of
course, these are done, these studies are done with a limited number of
transgenes, and we were discussing the issue of gamma-chain before, but this
could be true for any gene.
Here
I am arguing on the issue of insertion on mutagenesis if you can call it this
way. So in that regard, for the ADA
gene, the TK gene, and the truncated form of the LNGFR apparently there is no
reason today to say we should limit the total dose of lymphocytes.
The
available data on hematopoietic stem cell gene therapy for ADA-deficient SCID
do not show an expansion of dangerous clonal integration. We have monitored the change over time there
is no expansion.
We
are sequencing, and we have not found anything. The analysis will continue.
The analysis will continue in my mind doesn't mean that this is really
useful. I am just giving you my
opinion. We are doing it.
And
whether or not we will get out anything I don't know, but I think that some of
the groups that have the possibility because of the size of the study of the
patient should do it, but whether this should really be mandatory for each
study at this stage for the data that we have in hand I am not really sure.
But
of course I am in a different position related to the one of this
committee. Instead of
transgene-specific risk, the discussion that has already started, it is not my
position to fuel the discussion also because as the Chairman already said, this
is fueling it enough.
How
extensive should be the monitoring of the integration sites, I don't know. We will definitely go on to analyze the
different technology, probably a few thousand sites, and hopefully it will make
for a nice paper, but if it will make for anything more, I don't know. Thank you very much.
(Applause.)
CHAIRMAN
SALOMON: We will return to this for
questions, Claudio, after Dr. Thrasher has given his presentation. So the second speaker is Dr. Adrian
Thrasher, from the Center for Gene Therapy and Childhood Diseases in the
U.K. Is it the Imperial Cancer Centre
in London?
DR.
THRASHER: I am actually an immunologist
at the Greater Ormond Street Hospital in London. We have one of the biggest immune deficiency services in Europe.
Okay. So we have several Phase-I clinical gene
therapy trials which were open and I am going to talk to you today a little bit
about our X-SCID study. Marina actually
introduced X-SCID and has given you most of the background excellently earlier,
and so I can be relatively brief.
I
will say that the other two studies that we have is for X-linked chronic
granulomatous disease, and in this study we have treated one patient, and the
ADA study is approved by our G-type, but we have not treated any patients yet
in that study.
I
just want to reinforce what Marina first said and Claudio said with the
importance of reference points, because when we are trying to devise a new
therapy, we need to compare that with the existing therapies.
Now,
the European study has been extensively collected since 1968 and has been
recently published in The Lancet as Claudio has said, and I just want to
show you a couple of slides. The first
one is the probability of survival after a mismatched transplant in SCID
patients according to conditioning regime.
And
many of you will know that the preference treatment of SCID in Europe and in
most centers in the U.S., I believe, is to use conditioning in the mismatch
setting. And since 1968 in the
transplants the survival rate has been measured at about 50 percent.
Now,
of course, we have gotten a lot better at transplanting these patients, and
this is not accurate data for today's transplants. Now, we can also break down these transplants into subcategories
of SCID, and we can definitely say that the outcome for the positive forms of
SCID, such as JAK-3 deficiency or gamma-c SCID, is a lot better than, for
example, ADA-SCID.
And
currently as I said the survival rate across Europe and in our center for
mismatched transplanting ADA SCID remains at about 30 center at one year. So it is very poor.
So
this slide Marina showed earlier, and this indicates the improval in outcome
for transplants in SCID and B-positive SCID for mismatched grafting.
And
we counsel our patients now about an 80 percent one-year survival rate. Now, this does not take into account the
patients who don't make it through the transplant center. We know that several of those or many of
those occurring over time.
The
other thing that we have to remember is that to achieve efficient or improve
the B cell engraftment and T-cell engraftment that we certainly believe in
Europe that you need to use some form of preferative chemotherapy.
And
when you are considering risks and benefits, you have to build in the effects
of the chemotherapy into the equation, and there are certainly long term
effects related to chemotherapy employed in infancy, and the chemotherapy
usually or has been until very recently been using alkylating agents, such a
busulfan.
And
there are clear effects documented on growth, fertility, possible developments
of secondary malignancies later in life, and also neuropsychological effects,
which may in-part at least be related to the use of chemotherapy.
And,
of course, in many of these cases there is incomplete immunity
reconstitution. And I would just show
this, because I think this is a graphic example of how brutal using
chemotherapy is in children, and so these are dental x-rays of a normal seven
year old, and a seven year old treated in infancy for SCID by condition
transplants.
And
the normal seven year old is showing secondary teeth, and this child has no
secondary teeth. Now, for a seven year
old child, this is a big deal both very psychologically and physically, and we
see dental abnormalities in most of our conditioned transplants.
So
really these are the drivers to try and develop less toxic both in the short
term, and in the long term treatments, and more effective treatments in terms
of immuno-reconstitution.
Now,
Marina set the case for this type of study and our gene therapy study for
X-SCID is very, very similar to the study conducted in Paris. So what I will do is highlight some
differences.
The
entry criteria are the same and so there is no matched sibling donor. The vector we use is also an MFG based
vector, and it doesn't have the BT mutation, and whether that is relevant or
not I doubt.
There
is a single gamma change, cDNA, and so this is virtually identical to the
vector used in the Paris study. One
significant difference perhaps is that all vectors are produced in PG13 cells,
and so it has a different envelope. It
has the gibbon ape leukemia virus envelope.
The
transduction cycle is the same, and we started them on Monday morning and we
finished on Friday evening when the cells are reinfused back into the patients.
The
CD34 positive cells are purified by the CliniMACS system, so it is magnetic
bead selection system. The cells are
preactivated for 40 hours in the presence of high dose cytokines, stem cell factor,
FLT-3 ligands, thrombopoietin, and a slightly lower dose of IL-3 than used in
the Paris study.
And
another difference is that we actually use serum-free conditions to culture our
cells, as opposed to using some fetal calf serum. So there are three cycles of transduction over three days on
Retronectin-coated surfaces. So this is
in a closed system, and the back to the bag type system, which many of you
would be familiar with.
And
as I said, these cells are reinfused without any preconditioning for the
patients. So the only procedure that
the patient goes through is a bone marrow harvest, where we take probably
around a hundred mls of bone marrow under general anesthetic for about an hour.
And
so these are the details of the patients who we treated to date, and as I said,
a follow-up is -- the maximum follow-up is 18 months for Patient 1, and they
all present with classical features of SCID.
The
age at therapy is 10 months, and 10 months, and 4 months, which is our youngest
patients, and this patient was diagnosed early because of a previously affected
family member.
And
then the final two patients are slightly atypical, and this is a 20 year old
patient with a failed graft, and this is a patient who has an unconditioned
haploidentical transplant in infancy, and who has had waning immunological
function, and consequently has developed end-organ damage in the form of
bronchiectasis, liver disease, and gut disease.
And
the fifth patient is a rather unusual patient, also from Denmark, who has
classical SCID and expresses no gamma-chain, and presented with PCP at the age
of 10 to 12 months, but survived at home with prophylactic antibiotics and
immunoglobin cover until the age three years, and at the time of treatment he
in fact was completely well and free from infections, and that is unusual.
So
this is total cells infused times 10 to the 6th, and 180 million, 180 million,
78 million, 150 million, and 115 million.
This is our transduction procedure, and you look at CD34 along here, and
gamma-chain here, and we start off with virtually pure CD34 populations, and
through the week we lose CD34 positivity on our cells, which is a side effect
if you like of the culture conditions that we are using.
And
so at the end of the culture we would say that approximately 60 percent of our
cells are transduced for gamma-chain, and that 30 percent of the population
retains CD34 positivity.
This
is the data on the first three patients, and I will show you a bit more on
Patient 1 because this is the longest follow-up. The first thing that we noticed, and the same as in the Paris
study, is that we see many NK cells emerging very consistently between or after
four weeks of infusion of cells.
And
these rise and then tend to fall a little bit, and then stabilize at or just
below the normal range for an age match control. At 10 to 12 weeks, we begin to see new lymphocytes appearing, and
these gradually rise over time, and then stabilize, and at 18 months in Patient
1, we see normal numbers of lymphocytes, normal CD34 and CD8 ratios and
slightly low numbers of NK cells.
Patient
3 is a Saudi patient, and again the follow-up is shorter on him, and he is in
Saudi at the moment, and from the information that we have his immune
reconstitution continues to be very good.
Patient
2 had an arrest of immune reconstitution of about 12 weeks. Now, this coincided with the time when he
developed severe gastrointestinal bleeding, and we believe that this is a
consequence of immune reconstitution.
It is not a side effect of gene therapy, per se.
He
then underwent radical surgery to remove part of his bowel, and developed
nutritional problems afterwards, and so we believe that these factors in
combination caused this delay or this plateau of immune reconstitution.
Now,
around about here we managed to correct his nutritional problems, and we
corrected the stoma that was produced at the time of surgery here, and so his
gut was linked back up again.
And
his immune reconstitution appears to be running back on track. So I think that is interesting, because it
may be saying that at this point in time that we are reconstituting his T-cells
from cells that have been engrafted in the bone marrow, rather than cells that
are in the initial graft going into the patients, but that is speculation at
this point.
And
this is an interesting point. This is
Patient 3, and at the time of T-cell emergence, he also developed this rash on
his hands and feet, and in fact all over his body, and which really is
indistinguishable from a mild cutaneous graft versus host disease. Now, this responded very well to topical
steroids, and has not reoccurred subsequently.
Now,
this is Patient 1, and this just shows you in a different way the emergence of
naive T-cells, and so if we look at CD27 and CD45RO, and the 27 positive RO
population are naive cells, and so you begin to see them at 10 weeks, and these
gradually increase in number over time here.
And
we know that if we take these cells out and we stimulate them with mitogens, or
antibodies to CD03, that they will proliferate entirely normally.
We
can also use the V-D-J recombination process to measure the diversity of the
immune reconstitution as you see earlier, and so both by immunofluorescence
studies we can show that the TCRVbeta families are represented entirely
normally, and with a normal distribution.
And
we can also measure by a spectral-type analysis by that diversity of CD03
links, and so again this is in Patient 1, and look at the total peripheral
blood mononuclear cells between weeks 12 and 16, and you can see that this is
week 12 and this is week 16, and you can see at the beginning that there is an
oligoclonal pattern, and this is very typical, whether it be in the gene
therapy setting or in the transplant setting.
The
reconstitution is always oligoclonal to start with, and in fact some of these
clones you can see from quite a distance after or for quite a time after
engraftment, and they do persist.
But
because there is a clone there doesn't mean that it is a pathological
thing. So by week 16, you can see some
normalization of these distributions, and then by week 24, when he has enough
cells, you can separate the CD34s and CD8s, and see again a highly complex
Gaussian distribution in those representative families. And again at week 52, the same.
So
this is the follow-up on these patients, and the first patient was followed up
at 18 months, 13 months, and 9 months, 6 months, and 2 months. The first three patients are alive and well,
and at home, and this patient is off all therapy and off antibiotics and
immunoglobulin.
The
third patient is about to discontinue the immunoglobulin therapy and has normal
levels of IgA and M. And Patient 3 at
the moment remains on immunoglobulin therapy and prophylactic antibodies, but
again is well and thriving.
Patient
4, which is the 20 year old patient, we can see no evidence for change in his
immunological function or diversity by an immunoscope or spectral-type
analysis, although we do see a positive signal for transgene CD34 positive
cells.
And
again Patient 5 is a three year old patient that was treated just before
Christmas, and the follow-up is 2 months, and he has NK cells, and he also has
small numbers, just detectable now of naive T cells, and he remains alive and
well at home.
The
copy number in our cells is very similar to that seen in Marina's study. We have seen approximately one transgene
copy number per T-cell, and we also see markings of B cells between 1 and 5
percent, and in myeloid cells between .1 and 1 percent.
This
is a LAM-PCR analysis, which we are all familiar with, and this was very kindly
done for us by Christof von Kalle, and Manfred Schmidt, and again you see a
very familiar pattern in these two patients of polyclonal smears in the CD3
populations in these two patients.
We
were also interested in perhaps more bands, more polyclonality in the B cell
lineage, and monocyte and granulocyte image than seen in the Paris study, and
that may be a reflection of the different envelope that we have used for this
study.
And
we believe that also may be important for the robustness of the immune
reconstitution, because if you can keep applying gamma-c transduced cells that
contribute to the thymopoiesis, then the longevity of reconstitution may be
more robust.
Okay. So the monitoring that we are undergoing or
undertaking at the moment is conventional, in terms of spectral-type
analysis. Obviously lymphocyte counts
and mitogen responses.
Christof
was very kind to do the integration profiles for us. We have performed RT-PCR for LMO-2, and have found in sorted
T-cell populations, and have found low levels of LMO-2 transcription in some of
the patients, but then we have also seen low levels of LMO-2 transcription in
some of our normal controls.
So
I am not sure that is a useful test to do, except that if you can clearly see
hyperexpression of LMO-2, and then it may be useful. We are performing microarray analysis on all sorts of populations
at the moment to look at global gene expression of cells, but I don't have any
data on that.
And
finally we have also looked for the presence of VL-30 sequences in our
patients, and I can say that in one of the patients by PCR we can see the very
low level in CD-3 cells. But it has
been under textbook in 4 out of the 5 patients.
So
as you know, our current trial status, which is this is a restriction imposed
by our GTAC and our Medicines Control Agency, is that the X-SCID study at least
is reviewed on a case by case basis.
Okay. I will stop there and take
any questions that are necessary. Thank
you.
(Applause.)
CHAIRMAN
SALOMON: Thank you very much,
Adrian. If I can have Claudio join you,
then what I would like to do is turn these two speakers to the questions.
To
start, I wanted to make sure that I was really clear on how exactly similar,
Adrian, your studies in the X-SCID children were to Marina's studies at the
Hospital Necker.
So
I guess the key question, and you didn't give us kilograms of the children, but
I was trying to figure out that even if they were 10 kilos or more, they were
getting more like 10 to -- somewhere around 10 million per kilo.
DR.
THRASHER: Yes.
CHAIRMAN
SALOMON: So, the number one question
was can you give us some range of CD34 cells per kilo. The preconditioning, there was no
preconditioning in your studies. And I
apologize to Marina, because I don't remember whether there was any
preconditioning in yours?
DR.
CAVAZZANA-CALVO: No.
CHAIRMAN
SALOMON: So that was similar.
DR.
CAVAZZANA-CALVO: Yes, it was identical.
CHAIRMAN
SALOMON: Identical. Anyway, if you can help me with any other --
DR.
THRASHER: So the differences are our
vector is serotyped with the gibbon ape leukemia virus envelope, okay? One difference. And the second difference, which may or may not be important, is
that we don't use fetal calf serum in our culture process, and that may alter
the distributions. So we don't know.
I
mean, we have no data on that. And the
expansion of total cells we see is probably a little bit less than what Marina
sees. We see about a 4 to 5-fold
expansion in total cell number, but we also see a big loss in CD34 positivity.
So
our expansion in CD34 positive cells is probably only two-fold or three-fold
maybe, or something like that. I can't
actually give you the exact numbers as I don't happen to have them.
CHAIRMAN
SALOMON: Yes. If you will just forgive the Chair's prerogative for a
moment. I just wanted to track that
down, and so the one thing is that when you -- you got a 60 percent transduction
if I remember right, but about 10 percent of the cells were CD34 at the end of
the --
DR.
THRASHER: No, 30 percent.
CHAIRMAN
SALOMON: Thirty percent. Okay.
Marina, can you --
DR.
CAVAZZANA-CALVO: Similar. With the total cells transduced.
CHAIRMAN
SALOMON: Just so it is on the
transcribed record, if you could come to the mike.
DR.
CAVAZZANA-CALVO: In terms of the total
number of transduced cells, I think Adrian is highest than me, because he
mentioned 60 percent of the total cells transduced, and we never reached this
level. It is around 40 percent for us.
And
in terms of CD34, that positive cell for the gamma-chain is the same, around 30
percent from 25, up to 40 percent. This
is the range limit we had.
CHAIRMAN
SALOMON: So you gave 40 million -- 40
to 44 million in the two patients, and CD34 cells per kilo.
DR.
CAVAZZANA-CALVO: No. For P4/P5, the question is related to the
two severe adverse events, they received, at maximum, 20 million per kilogram
of CD34 positive cells, gamma-c positive.
CHAIRMAN
SALOMON: Okay. Right.
About 50 percent of the total, they got. Okay. Now, that was CD34
--
DR.
CAVAZZANA-CALVO: Positive.
CHAIRMAN
SALOMON: -- positive. So that would be 30 percent of what you
infused, right?
DR.
THRASHER: Right. Well, before finding those, we would have to
sit down and do it accurately.
DR.
MULLIGAN: Can I make a suggestion? This is going to haunt us unless we -- are
we always going to do per kilogram, total cells CD-34? I think the simplest thing is the total
number of cells that you put in a patient.
DR.
THRASHER: Yes, I agree.
DR.
MULLIGAN: Okay. So what is the difference between that? Which is going to be comparable.
DR.
THRASHER: Yes.
CHAIRMAN
SALOMON: That's fine, and thank you for
that. So how many --
DR.
THRASHER: Well, that is the total
number of cells that we are putting into the patient is between 80 and 200
million.
DR.
MULLIGAN: And how many per kilo?
DR.
THRASHER: No, no, that is total
cells.
DR.
CAVAZZANA-CALVO: Yes, if you can permit
a comment. In terms of a bone marrow
transplantation, the cells given to the cell must be expressed per kilogram and
not in total number, and there is no sense, because all comparison with the
hematopoietic stem transplantation is based on the kilogram basis.
DR.
THRASHER: Yes, I would agree with that,
but I think that in terms of measuring or trying to determine the number of
integration events you are putting into the cell, I should change that slide to
put in the total number of cells, okay?
The
other thing that I think you may want to consider, I know you were talking
about cord blood earlier, is that the CD34 positive cells you are putting into
the patient here are different than the CD34 positive cells you get out from
fresh cord blood.
So
that way you can directly compare your numbers if it comes to that.
CHAIRMAN
SALOMON: Right. Now, just one last question. So this is to Claudio. So when you did the ADA-SCID children, how
many -- can you give us a sense of how many transduced hematopoietic stem cells
you were putting in?
DR.
BORDIGNON: It is about one log less,
and the reason -- and also there is a significant range, from 0.9 to 20 or 15,
and so even inside the study there is some difference. The reason for that is -- and in that regard
ADA is different and would probably not be so informative.
So
depending upon the level of toxicity that the patient gets there, you get or
you don't get any expansion of the CD34.
You start with the cell dose, and you finish with the same cell dose.
You
don't get any expansion, and sometimes even the harvest of the CD34 is
worse. One of the patients, the patient
from 0.9 dose, was actually going through some myelotoxicity due to a previous
viral infection.
So
I think ADA is a very different story in this regard, and it would be difficult
to compare, except for what is concerning the total dose of transduced cells,
because that would give you an indication of the transduction events in vivo,
and therefore, a comparison on whether or not that carrier is associated.
But
this study is definitely at the low range compared to the X-linked studies.
CHAIRMAN
SALOMON: Okay. John.
DR.
COFFIN: Okay. For the sake of the back of the envelope calculations, which is
by far the best we could possibly hope to achieve here, could we agree that the
total number of transduced cells was somewhere -- and in the case of the
X-linked SCID, was somewhere up to around 10 to the 8th per patient in total
dose of integration events in these cells, and probably that level, and down to
about 10-fold less, in that range.
Would
that be sort of a fair range that we are thinking of? And that the two patients with the adverse outcomes were the two
that were at the high end of that range.
And I am not talking about per kilogram.
(Discussion
off the record.)
DR.
COFFIN: Well, they were still at the 10
to the 8th range.
DR.
CAVAZZANA-CALVO: Yes.
CHAIRMAN
SALOMON: Just as -- just a minute,
John.
DR.
BORDIGNON: I think --
CHAIRMAN
SALOMON: One of the things that you
have to do here is keep the comments on the mic, which is hard. I screwed up earlier on that, and so if you
have a comment, I will do my best to recognize everybody, but you have to be on
the mic, or otherwise the transcript will have holes in it and it won't work.
I'm sorry.
DR.
BORDIGNON: I think the three of us can
sit down and give you a table and exact the numbers, per kilos, per total, and
everything else, probably in 10 minutes.
DR.
COFFIN: I think that would be great.
CHAIRMAN
SALOMON: Then what I would like to do
is to continue the discussions, and move towards when the first wave of the
discussion is over, take a 10 minute break, and then let them do that, because
I think that is really important to me, and I am getting some nods. Is that a good idea?
Because
I am trying to square all these numbers and am having trouble with it, and so
let's continue with the discussion that doesn't involve the numbers.
If
there is any question that someone has about the numbers, they will hold it
until we move up to a 10 minute break, okay?
Mahendra and then Rich.
DR.
RAO: Well, this is sort of a general
question to anybody who can answer it, but it seemed to me that when everybody
talked about having no adverse events, the time period was too short given what
was reported.
So
that if you had reported at that time on that study, you would have also said
that there were no adverse events. Is
that a fair statement?
DR.
BORDIGNON: Definitely not for the
ADA. I may have confused you
there. The initial study, the first
bone marrow studies, were done in 1992.
So this is true. However, if you
look --
DR.
RAO: For the stem cells?
DR.
BORDIGNON: Well, that was bone marrow
stem cells transduction. It is true if
you compare similar studies, and so if you compare the last study for CD34
purified, with the same cytokine combination.
So the study that is comparative, and the ADA that is comparable to the
gamma chain, then we are in that range.
With
one relevant difference, I believe, that having looked at the analysis of
clonal expansion, I think that at least the first two patients would have been
already informative.
CHAIRMAN
SALOMON: Let's do this. Richard, Barbara, Crystal, and Tom.
DR.
MULLIGAN: Well, just on Mahendra's
point, I want to echo that I think that this is key. I think when we go off and do our calculations that we should
also do a calculation just on simply how many, what number of patients does
Claudio have that are on the 3 year period.
Let's
just say that is some magic period, and how many patients are in your
collection of patients that have actually gone past 3 years and have had some
demonstrable gene transfer.
CHAIRMAN
SALOMON: We will put you on the numbers
subcommittee.
DR.
MULLIGAN: I am not finished, and so the
second thing is comparison of Adrian's protocol with Marina's. During the in vitro pre-stimulation cocktail
period, what was the total of A of growth of your cells in culture, versus --
and were they comparable factors? It
looks like they were comparable factors, except you had calf serum I think, she
didn't have calf serum.
Because
I think that an issue -- if one hypothesis is that there is some abnormal
target cell that is diseased specifically, then those in vitro culture
conditions could be very important.
For
instance, you may have differentiated out the cells that otherwise could be
dangerous cells if they were preserved in the culture. So it would be very important to see if they
are comparable.
DR.
THRASHER: Yes, I would agree with
that. We don't use fetal calf serum,
fetal calf serum is not popular in the U.K. for various reasons. But I think that is probably the only
significant difference in the culture conditions; that we are serum free.
And
I agree with you. I think that made a
big difference in the types of cells proliferating, or maybe different regions
of the chromosomes that are susceptible to integration, but we have no data on
that.
And
we do plan to compare very closely the two transduction protocols to see if
there are significant differences.
CHAIRMAN
SALOMON: Barbara.
MS.
BALLARD: Yes. My question is very -- actually kind of an extension of his, but
you talked about a different vector envelope.
DR.
BORDIGNON: I'm sorry, it may not even
matter, but I didn't answer Rich's question.
Did you ask how many patients were over the years --
CHAIRMAN
SALOMON: Yes, but we will get to that
in the 10 minute break. Sorry.
DR.
BORDIGNON: Okay.
MS.
BALLARD: Somewhat an extension of his,
in that you mentioned a different vector envelope was used in your study from
the Paris study, and I was curious if there is any way to know how much
difference that made in how the insertions occurred?
DR.
THRASHER: Well, Christof may want to
comment on this, but just looking superficially at the LAM-PCR data, the number
of integrations in CD3 are probably similar, but I have not looked at the
comparative data. I mean, I think
Christof should maybe comment on that.
DR.
Von KALLE: The thing that we think is a
little different
CHAIRMAN
SALOMON: I'm sorry, but this is
Christof von Kalle.
DR.
VON KALLE: I'm sorry. The thing that may be a little different
between the Paris and the London trial is that the amount of insertion sites we
tend to find per given number of myeloid cells is higher in the trial from
London.
I
don't think that we can say anything firm about the number of insertion
T-cells.
CHAIRMAN
SALOMON: Let me just try to
clarify. You kind of trailed off. It is higher in the French trial, or higher
in the British trial?
DR.
VON KALLE: In the British trial. The number of integrations as defined per
nanogram DNA of myeloid cells seems to be higher in the British trial.
CHAIRMAN
SALOMON: Is it still an average of one
copy per cell?
DR.
VON KALLE: Oh, yes. Oh, yes.
Well, actually in myeloid cells it is a lot lower on average than one
copy per cell.
DR.
MULLIGAN: Can I just address her
question technically? The GALV versus
the ampho, shouldn't infect the types of integrations that occur, I think you
might have been asking would it go into different locations, and there is no
sense that would occur.
But
in fact the kinds of cells that could be infected could be different. And so there was a weird target cell
population and it might be more infectable by ampho than by GALV, or less
infectable?
CHAIRMAN
SALOMON: And remember that by the
premise that we have on the table here, which we will get to later, if
integration is not completely random, or if integration is affected by which
genes' chromatins are open at a given time, then the possibility that different
packaging envelopes would target different populations of cells could also
affect the spectrum of the genes that might see the integration event.
And
so it is not totally -- it is an interesting question, but I don't have any
answers for you. Crystal, and then Tom.
DR.
MACKALL: The first question is for Dr.
Bordignon. It would seem that the
combination of LMO-2 integration or around there, and gamma-c is a bad
combo. I mean, a very simplistic
interpretation. And you have listed for
us thousands of integration events that have been accomplished in mouse and
human models without adverse events.
But
do you know if any of those were in or around LMO-2?
DR.
BORDIGNON: Yes. That is a very good point. We have not found any so far, and we are
trying to do -- to have a quicker way to answer specifically only that
question, rather than analyzing zillions, how many go to the LMO-2, and I don't
have an answer at this stage.
My
impression is that from what we have analyzed so far, is that it is not a hot
spot. It is not something that happens
because it is more susceptible in the same transaction conditions, because
essentially the transaction conditions are the same.
So
from here down it is all speculation, of course. You can imagine that it occurs at exactly the same frequency, but
it does not pop up, also that the inverse PCR system is also related to the efficiency.
You
know, if you get the right amplfication size and the right primers and so on,
they will come out more frequently. I
am convinced that you will be able to give a definitive answer to this in a
matter of probably a few months, but at this stage it is just my impression.
DR.
MACKALL: And I think it is critical
with what we are going to be charged with now to try to decide, which is
whether the insertion of another gene around LMO-2 is going to be just as
dangerous, and until we know whether there is any data to that effect, it is
going to be very hard to know how critical the gamm-c component is here.
The
second point, just in terms of distinguishing the British from the French
studies, I still an struck by the post-gene therapy data that looks
different.
In
other words, the two patients that got leukemia had this dramatic immune
reconstitution that was at an increased rate, and so that within a month and in
an increased amount.
I
mean, they were up to 10,000 T-cells, and I didn't see any of your patients
doing that. Is that true?
DR.
THRASHER: Yes, that's true. I mean, those patients are exceptional, and
in Marina's study as well, and they stand out as the patients who reconstitute
the quickest.
DR.
MACKALL: It would be certainly nice if
we had an earlier marker for those patients that were going to develop, rather
than having to wait 3 years for them, and if you go back and look, in one year
they certainly looked different.
DR.
THRASHER: Yes, in hindsight, I think
that is true, but as Marina pointed out, those parameters remain within the
normal range for age-match controls.
DR.
MACKALL: We are only setting the
normals now and they are standing out now.
DR.
THRASHER: Yes.
DR.
MURRAY: This is for Adrian. I noticed that you had quite a broad range
in age of treatment of your patients, and the youngest was 4 months to 2 years.
And
I want to focus on in particular the two youngest patients, at four and 10
months, I believe it was.
DR.
THRASHER: Two at 10 months, and one at
4 months.
DR.
MURRAY: Okay. There is also the two patients in the French trial were the two
youngest patients also who have the immune response. I noted or remembered you saying that Patient 3, who is 4 months
old at treatment.
But
what I don't remember was which patient did have -- I thought one patient in
one of your graphs did have an earlier immune reconstitution than the others.
DR.
THRASHER: Actually, the scales are
different in total number of lymphocytes, the actual initial reconstitution
rates are virtually identical in all of them.
DR.
MURRAY: They are, and so you didn't
have one with a more significant response before the 3 month period?
DR.
THRASHER: No.
DR.
MURRAY: Okay. And which patient was it that had -- I can't remember the patient
number of the one who needed the bowel surgery.
DR.
THRASHER: Two.
DR.
MURRAY: That was two, and so how long
was that patient in treatment?
DR.
THRASHER: Ten months.
DR.
MURRAY: Thank you.
CHAIRMAN
SALOMON: Phil.
DR.
NOGUCHI: It is to follow up on some of
those questions, and Patient Number 4, Adrian, was that the patient that
appeared to be a very mild GVHD?
DR.
THRASHER: That was Patient 3.
DR.
NOGUCHI: I'm sorry, Patient 3, and that
was the youngest patient; is that correct?
DR.
THRASHER: Yes.
DR.
NOGUCHI: And do you think that might be
any indication that perhaps the cells that are being transduced might be
somewhat different than if they are transduced at an older age.
DR.
THRASHER: It is impossible to say. I mean, the numbers are so small. GVHD type phenomenon in autologous
transplants is well recognized. What
the stimulating antigens are we don't know.
It could be maternal cells, and it could be infection on board at the
time of the graft. We don't know. We believe that it may be a cytokine-driven,
CD4-mediated event.
DR.
NOGUCHI: Just a couple of other trivial
questions. Do you have any information
yet on this Patient 3, in terms of integrants?
I think you presented, I think, Patients 2 and 5.
DR.
THRASHER: They actually all look pretty
similar in terms of the distribution of integration.
DR.
NOGUCHI: Okay. And was Patient 3 or which patient -- how
old was the patient that had this very preliminary evidence of a VL-30
sequence?
DR.
THRASHER: How old was he -- well, 10
months at the time of treatment.
DR.
NOGUCHI: No, you mentioned one of the
five had evidence of PCR positive ?-
DR.
THRASHER: Yes, VL-30 sequences. We can
detect that in Patient 2 a year after treatment, and at a very low level, you
know, between 1 and a thousand, and 1 and a hundred T-Cells, compared to one
transgene of T-cells.
DR.
NOGUCHI: Thank you.
CHAIRMAN
SALOMON: Kathy.
DR.
HIGH: I know that Marina is looking at
this question, but just to the group, are there any data that suggest that CD34
positive cells from infants less than 3 months of age are somehow different
from those of older ones?
CHAIRMAN
SALOMON: Marina, you might want -- I
think she is running away.
DR.
CAVAZZANA-CALVO: I think nobody knows,
because for a practical reason none of these can harvest the bone marrow sensor
from children without any diseases. So
the studies were conducted on cord blood, but we don't know when there is a
switch of proliferation capacity between cord blood and newborn.
The
cord blood proliferates up to 10-fold when you make the same protocol in the
transaction rate and is much higher in bone marrow, and the 3 months patient
who had very similar to cord blood, and 11 months, and the 8 month patient, are
much more similar to bone marrow.
But
the figures are so low that you can't make a statistical test.
CHAIRMAN
SALOMON: And sort of following on that
theme, Claudio, you answered me at one point that the expansion potential, or
the expansion seen in the early activation of your stem cells was one or two
using Marina's view.
And
your statement to me was, oh, because ADA-SCIDs are very different. So can we go back to that? A), are you saying that you used the exact
same protocol; and, B), are they really different even if you match for age?
In
other words, is a 4 month old ADA-SCID really acting differently than a 4 month
old gamma-SCID in terms of their proliferation in these ex vivo things?
DR.
BORDIGNON: What I was trying to say
that they are less homogeneous in that regard, and therefore it is much more
difficult to extract the same type of information.
And
they tend to be from a metabolic point of view much more prone to
toxicity. Now, the study will probably
be different if you would do the same study in PEG-ADA patients when they are
detoxified.
But
the plans and protocol is designed for patients who do not have access to
PEG-ADA, and that was what was requested initially, and that is what we are
doing.
So
under those conditions, you have patients that have significant metabolic
toxicity, and therefore they proliferate relatively little, they harvest
poorly, you have a low number of cells and low growth.
On
the other hand, you have patients that respond absolutely normally, and they
grow 5 to 10 times during that transduction phase as the patient described by
Marina. Maybe a comment from Don Kohn
on this.
CHAIRMAN
SALOMON: All right. Don.
DR.
KOHN: Don Kohn, Children's Hospital,
Los Angeles. We are doing a trial for
ADA gene therapy with Fabio Candotti, Cynthia Dunbar, and myself, and we have
harvested marrow from four of those patients on PEG-ADA; a 4 year old, a 5 year
old, a 15 year old, and a 20 year old.
It
mirrors all the coments that have been made.
We get much less cells as they get older, and they tend to transduce
less, and so even by four years old, you are over the hill to some extent. And I think it is a big factor that these
very young patients just have a lot of cells that transduce very
efficiently.
And
the disease setting may also be different in ADA, and we have also done
children with HIV, and get again lower numbers, like 1 to 2 million per kilo,
and not 20 or 30, or 40 per kilo.
CHAIRMAN
SALOMON: So I think an interesting thing
here is -- and an interesting theme here that we could return to later is that
assuming that age is this obviously very powerful biological determinant, there
seems also to be the influence of the diseases, and I thought that Claudio's
comments are well taken about the toxicity that occurs from the primary gene
defect in the ADA kids.
So
that may be another factor, that if you take that away, you may level the
playing field there to be more of the age.
The activation protocols and the level of activation are felt at this
point to be necessary to get good transduction efficiency.
But
in the context of all of the things that we have begun to talk about, one
wonders when we get back to safety whether we should carefully consider how
much activation is necessary in a given protocol to achieve a reasonable amount
of vector integration.
And
certainly one could then go from there to argue for less is better if you can
get a sufficient amount of transduction.
So, Claudio, lining that up is, what were your transduction efficiencies
despite the fact that your proliferative activities were significantly less?
DR.
BORDIGNON: Between 10 and 40.
CHAIRMAN
SALOMON: Joanne.
DR.
KURTZBERG: I think it is also important
to notice that the ADA kids are different because if they are detoxified early,
they can have their own host cells proliferate without transfection. So their immune regulation may really be
different of the cells that are transfected.
And
so I think they should be evaluated as a completely different patient subset.
CHAIRMAN
SALOMON: I didn't mean to imply that
these diseases should be collapsed in any way.
I was just trying to talk about the biology of the stem cells. John.
DR.
ALLAN: This is probably a naive
question, but in your Patient Number 2, Adrian, that had gastrointestinal
problems, it made me start to think that is it possible that you could actually
either constituitively express genes that are not directed towards uncontrolled
growth, but could actually home to specific tissues.
And
so you get -- you may get some sort of diseases arising because of the nature
of the cells that have been transduced.
So did you do a histopathology on the intestines?
DR.
THRASHER: Well, actually, the
gastrointestinal problems also pre-dated the gene therapy. So you had some GI hemorrhages from
macroscopically inflamed lesions prior to the gene therapy.
The
histology was pretty unexciting to be honest, and we never found histological
microbiologic reasons for those lesions.
But the same lesions bled after gene therapy.
DR.
ALLAN: I just sort of wondered if you
may get other types of diseases besides cancers that you might want to think
about. I don't know if that is even a
real possibility, but I would like to throw that around at some point.
CHAIRMAN
SALOMON: Ken.
DR.
CORNETTA: I am interested to hear what
these numbers will be around CD34, but I just sort of give in prospective that
we are talking probably an order of magnitude more CD34 in these very young
children than we would normally think about per kilogram in adult
transplantation.
But
when you then factor in that often adults may be two orders of magnitude bigger
than these children, if we are looking at actual integration sites, if the
Committee is to try to find a number that sort of sets the bar, I think that is
going to be very hard to do.
And
I think we are ignoring a lot of the other factors that may be here. So I just sort of would have the Committee
think about as we do this that this may be a bar that we really are never going
to be able to try to set.
CHAIRMAN
SALOMON: Mahendra, and then Dave.
DR.
RAO: One thing that I wanted to do was
just try and get a general comment either from the Committee or one of the
speakers about this full integration site issue. I mean, you made the point that perhaps it is gamma-c, along with
LMO-2, which might be the important thing.
Maybe
it is not gamma-c at all, because when you look at the over-expressing mice,
you don't see that kind of procreative response at all, and so it is not the
gamma-c.
And
when you looked at the integration sites in the inverse PCR experiments, I
thought that the number that you saw within genes, you know within the intronic
sound boundaries was significant, as a number from the total number that you
analyzed, a third, and was that not surprising, or is that not a cause for
thinking that you can interrupt genes or do something?
DR.
BORDIGNON: Well, I think that will have
to be a bit better defined than what you mean around genes. We have been choosing some sort of distance,
but whether or not this is meaningful in the sense that the distances are
appropriate, and really results in amplification of the gene that is upstream
or downstream.
It
is an additional part of the work that will need to be done.
DR.
RAO: If you look at your table to ask
if they were in the intron or exon.
DR.
BORDIGNON: No, no, sure. Despite the consideration that it is not
really the siting itself there that would matter, but whether or not it is
affecting the expression of the gene, and where the gene is and so on.
There
is apparently, but I think it is too early to say from this data, but there are
data on the HIV integration that a famous science paper by Bushman and
co-workers that suggests that there is a skewing towards a transcription active
sites for integration, by a factor of two, which is not much.
And
which for this type of concern for this type of study will probably not matter
at all. I think that I will have to
wait for a bigger number.
CHAIRMAN
SALOMON: David, and then John.
DR.
HARLAN: When the numbers committee
meets, I would ask that they put together for us not only total cell number and
CD34 positive cell numbers, because the point that I wish to make is that CD34
is not a clear binary definition as Adrian, I think, you showed.
You
start off with CD34 bright, and then they get dimmer, and dimmer, and dimmer,
and it gets to be an increasingly fuzzy number.
CHAIRMAN
SALOMON: John.
DR.
COFFIN: I wanted to address two things
that came up before, which I probably forget the second part by the time that I
get to it. The first thing is that
there was discussion about setting a bar for numbers and so on. I don't think we will be able to do that.
But
I think it should be in our purview to try to do some back of the envelope
calculations to see, sort of, "what if things." And I think at some time in the future
somebody is going to have to sit down and try to do the best job they can with
that in a format design exclusively for that purpose, which this is not
appropriate, and so we might be thinking about that as we go forward.
The
second point regards both the distribution of integration sites and their
relationship with integration sites to turn on a gene expression. Our analyses have found that integration
sites are very, very widely distributed in cells as far as regions are
concerned, with very, very strong, and very local preferences.
The
Rick Bushman paper that was referred to uses a somewhat different method, but
it came to the conclusion that there was a skewing towards regions that had
been identified in genes and in HIV integration in human cells.
But
the scaling was a factor of two, and about a third of the genome by their
definition was genes, and those contained about 60 percent of the integration
event.
So
that number is small relative to the other levels of uncertainty that we are
discussing, and that is actually sort of a small error, or a small correction,
if that is the number that holds up.
And
finally the experience with MLV systems in particular, and ALV systems, where
lots and lots of integration sites activating genes have been looked at, has
revealed that the rules for whether an integration site can activate a gene are
probably extremely complex, and case-by-case, because in some cases their
integration is more than a hundred KB away from a gene that are known to
activate it.
But
that doesn't mean that the target for that gene is a hundred KB. It may well be that anything closer to a
hundred KB won't work. We just don't
know. It all depends on how the
chromosomes fall and everything else.
So
we really can't know that. We can only
make real guesses as to what in any given case might be the sensitive target
region. I usually use the figure of
somewhere between 1 and 10 KB for the sake of the back of the envelope
calculations.
But
it is certainly at least 1 KB I would say on average per gene would be the sort
of region that you could imagine the targeting to occur in.
DR.
BORDIGNON: Can I ask a question?
CHAIRMAN
SALOMON: Right now? Hang on a bit. What I would like to do is -- Carolyn, you had a question, and
then maybe Don, and then I would like to go to the break, where we can get some
of these numbers, and then come back if that is okay. And, Claudio, you will be the last question.
DR.
WILSON: This is on a completely
different topic, but Dr. Bordignon, you summarized very quickly for us a vast
amount of preclinical data regarding the use of the LNGFR marker gene, and made
a case for the safety of that gene.
And
I wanted to just clarify for my own purposes in contrast to the data from
Christopher Bounds' group. All of those
studies were using transduced lymphocytes, as opposed to hematopoietic stem
cells? Is that the difference?
DR.
BORDIGNON: No, no, I presented -- I
went very fast I realize, and I probably also made some confusion myself. But there are two sets of data. The first half was all related to
hematopoietic stem cells. The second
half was a lymphocyte study. So the
numbers are fairly equal in the two studies.
DR.
WILSON: Thank you.
DR.
CORNETTA: Again, maybe something else
that people can consider as people are working through the numbers. I think this insertional mutagenesis, we
sort of fixate on, that these vectors will just go in and knock out genes.
But
I think something that is very telling here is that in all of these patients
there has only been two occurrences, and it is both in the same locus.
So
I think again focusing rather from how many CD34 cells are at risk or whatever,
and also taking into big consideration that presumably some interaction,
whether it is the LPR enhancer or something else that is really playing a major
role here, I think that needs to be considered in these.
And
the second point is I think that not only do we need to think about how many
CD-34 cells have been transduced, but there have been many other T-cell studies
that we have not talked about, and these are mature T-cells that have been transduced
and had many more integrations, if you tried to put in how many have occurred
over these trials that have not seen this event.
So
again I think that this is a pretty complex issue and just to make sure that we
are thinking about all of those.
CHAIRMAN
SALOMON: The last question.
DR.
BORDIGNON: Yes. There was a very interesting piece of
information in what Christof von Kalle and Marina said about the existence of
another couple of -- I probably understood another couple of LMO-02 related integration
observed in the analysis.
Do
you know anything about whether or not this is affecting the expression of the
LMO-2 in those circumstances? Because
probably if there was an increased expression or not an increased expression,
and will analysis in the other one. I
hope that I didn't ask the wrong question.
DR.
VON KALLE: No, I think you didn't ask
the wrong question at all. One of the
clones that we looked at that have occurred in the patients earlier, and we
have tried to track it, and that was the one that was about 40 KB away, and
apparently it has not led to any lympho-proliferation.
The
other one that we are looking at that is closer, we also don't have any
evidence yet that is proliferating, but we have not done as much tracking on
this clone.
CHAIRMAN
SALOMON: But I think -- well, maybe I
am interpreting, but what I thought what Claudio was asking you was that in the
T-cells themselves that have that insertion, is there any evidence that they
are expressing an excessive amount of LMO-2 message, for example?
DR.
BORDIGNON: We cannot answer that
question because if we do not find it as a clone that we can separate, that is
not a question that we can technically answer at this point.
CHAIRMAN
SALOMON: Okay. We can talk about that later. You could get at it perhaps. I said that was the last one, but Linda had
her hand up. So, I'm sorry, you will be
the last question.
DR.
WOLFF: Carolyn brought up about the
pre-clinical studies, and I just wanted to clarify something. I thought I heard you say that the longest
time period was 6 to 8 months, would that be correct for the pre-clinical
studies in mice? What was the longest
period of time that these mice were analyzed or monitored?
DR.
BORDIGNON: In essence, the majority of
the animals, and there are a few animals that went to almost through the entire
life span, and were analyzed over 28 weeks.
Sorry. Yes, 28 weeks.
And
this also includes secondary and tertiary transplants, however, and so it is
probably more than the life span of the animal.
DR.
WOLFF: Okay. Thank you.
CHAIRMAN
SALOMON: Then I would like to take a 10
minute break. If I can have Rich, Ken,
and Marina. I am deputizing you as the
subcommittee here, and if anyone else really wants to be a part of this, they
are welcome to come up and join us.
(Whereupon, at 12:04 p.m., the meeting was
recessed.)
A-F-T-E-R-N-O-O-N S-E-S-S-I-O-N
(12:18
p.m.)
CHAIRMAN
SALOMON: Welcome everybody back. What we are going to do is -- I am going to
be the fall guy on this one, but we just are not going to get to lunch. I can see that. So for the panel, they are going to bring some cookies, and some
drinks and stuff, and I will try and work on that.
But
I apologize, on the other hand, I just think that the time is constrained, and
the topic is so important that I think a couple of hungry scientists and other
advisors is probably a reasonable price to pay for what we need to get
accomplished.
But
you can blame me for it. I don't know
why I am getting blamed for it, but I suppose that is the true nature of
blame.
DR.
NOGUCHI: We will support this and say
that the FDA actually feels that lunch is not necessary today.
CHAIRMAN
SALOMON: I have worked so hard to get
out of the evil empire at the FDA that you just set it back a couple of
years. Anyway, what we are going to
start with is that we had a kind of a little impromptu subcommittee of numbers,
and grappled with the issue of what numbers could be put together that that had
value.
And
obviously the speakers didn't come here with every detail in their
databases. So, Rich, can you give us
just kind of a quick rundown on this.
DR.
MULLIGAN: Yes. The only numbers that we could really get
three different values for were the total and estimate, a real estimate, of the
total number of transduced cells that are put into the patients.
And
that appears to be for the Paris and Milan groups of about a
hundred-million. So that is the total
numbers, whether they are CD34 plus, or deficient, that are infected.
And
it appears that Paris and London were about a hundred, and the Milan had about
a tenth. Okay.
CHAIRMAN
SALOMON: And the two children that
developed leukemia?
DR.
MULLIGAN: Had about two times that.
CHAIRMAN
SALOMON: About 200 million?
DR.
MULLIGAN: Yes.
CHAIRMAN
SALOMON: Okay. So the difficult point --
DR.
MULLIGAN: Two times for one, 1.5 for
the second. Okay. So that there is a 10-fold difference, and
one other little discussion that we had was just that the manipulations of
these cells in vitro are such that by certainly mouse marrow transplantation
they can have a major effect on the reconstitution potential.
And
so easily a 10-fold effect. So we are
clearly I think where judgment I think would be by the individual investigator
about what kind of things their protocols will do to take hits on the
reconstitution potential.
DR.
JUNGHANS: Just a question on that.
CHAIRMAN
SALOMON: Could you give you name.
DR.
JUNGHANS: Richard Junghans, Harvard
Medical School. One question on
that. Was that compensated for the fact
that you infect on maybe day two, and you expand? In France, they had a 10-fold expansion; whereas, in the other
groups they may have only had a two-fold.
So
it is really on the number of integration events prior to expansion that you
want to count?
DR.
MULLIGAN: No. This is the literal -- and this is a rough number, but this is
the literal number of cells that were put back into the patient that were
determined to be transduced.
DR.
JUNGHANS: Right, but if there --
okay. So that is a separate question,
as the number of integration events which may be more equivalent or the --
DR.
MULLIGAN: Yes, I think what you are
getting at is whether or not you have fewer integration events, but that is
going to be too complicated.
DR.
JUNGHANS: I can provide a little bit of
information on this because I had -- no, it is not 10-fold. I had a discussion
earlier that the -- that apparently as they tracked the number of integrants
the infection was ongoing I believe in these protocols through the entire
expansion process.
And
it looked like the vast bulk of the integrations occurred in the last day. So at most I think the correction that you
are after is probably a factor of two, and that is sort of the guesstimate that
I put on that.
Is
that there may be half as many unique integrations as total integrations in the
population, because the expansion was ongoing, but there is only a fairly small
number of integration events that occurred early on, and most of them appeared
to have occurred late in the expansion.
DR.
COFFIN: So they are reinfecting on a
daily basis through the whole expansion period?
DR.
JUNGHANS: Through the last three days,
I believe, the protocol is. The first
two days are getting ready and then the last three days are infecting all the
time.
CHAIRMAN
SALOMON: Okay. Thank you to everyone on the
subcommittee. So I guess one of the
things that came out of that before we go on was that there are some -- let me
see how to put this.
So
yesterday we spent a lot of time with some really lovely data from the
International Bone Marrow Transplant Registry, and Cord Blood Registry, and the
New York Blood Bank Registry, talking about the numbers of bone marrow stem
cells and peripheral blood stem cells, and cord blood, umbilical cord blood
cells, that were required for engraftment and doing comparisons.
Today
we are talking about a very different kind of situation, and it is a very
interesting highlight, and a challenge I think to the field, which is what Rich
referred to.
And
that is that if you take CD34 stem cells that have been in many ways processed
identical to the types of stem cells that I just got through mentioning, but
then put them through these transduction protocols of activation with a
cocktail of hematopoietic activating factors, and manipulations, such as
growing them on fibronectin or rectonectin, which is a recombinant fibronectin
fragment, that the question then becomes -- and then there is this range of
proliferation, which is a whole question in and of itself.
And
there is a big question as to how much reconstitution potential for a human
patient is left in the context then of how one would calculate what was an
appropriate CD34 dose.
And
all I am saying here is that I think it was clear to the subcommittee in
talking about it that we really don't have the kinds of information yet to
absolutely understand that.
However,
I think that we also felt that based on the preclinical models that the idea of
about a 10-fold loss of reconstituting capability would be a reasonable
estimate.
So
that the idea of giving 20 million CD34 per kilo, which is something that I
brought up, or 40 million per kilo, as I brought up in Marina's talk, may not
be such an unreasonable guess in this situation.
But
it is a really interesting and important topic to get back to in further
investigations. I don't know if anyone
wants to make any comment on that, but that kind of came out of our
discussions. Rich.
DR.
MULLIGAN: And I think that there are
many different groups that think that they are have better or worse protocols
along these lines and there are controversies.
So I think it is going to be very, very difficult to come up with any
sort of number.
In
the mouse case, where there has been all this pre-clinical information, there
is very, very few, if any, reports where they directly assess the
reconstitution potential in the hit after the infection.
But
there is cytokine cocktails in vitro culture where they assess the hit, and in
the mouse system you can test this by a competitive repopulation test, which is
a really good quantitative test.
But
in human, there is a tremendous controversy whether there is any in vitro
assay, any SCID-NOD mouse system that accurately assesses that, and I am
certainly on one end of the controversy thinking that there definitely isnt --
that these SCID-NOD systems are not appropriate for trying to make such an
assessment.
CHAIRMAN
SALOMON: Ken, do you want to have any
additional comment? I know that you
referred to some data that you had.
DR.
CORNETTA: I guess I feel like we are
getting off-track again with CD34. I
mean, I am sure that you had -- I was not here yesterday for the discussion,
but I have been involved in bone marrow transplants for about 15 years, and the
regime that you used to prepare the patient and everybody else is such a big
number that I am not sure that is really relevant to what is going on here.
I
think it is not necessarily how many cells you are having. If you think back to what happens in mice
who get below the LTR in a virus, they get T-cell lymphoma.
When
monkeys got exposed to this virus, they got lymphoma, and now we have patients
who have been exposed to this LTR, and for some unique reason that we have not
figured out, they have gotten T-cell leukemia, too.
It
is associated with the same gene in two different patients, and I think that is
where we should be focusing our biology and discussions about those kinds of
issues, rather than how many CD34.
Because
the calculations that I made earlier looking at our adult patients who got a
very relatively similar transduction process over fibronectin probably had very
similar numbers of cells transduced.
They
didn't have this issue, but again they were not genetic disease patients. They were cancer patients, but they are out
now 5-plus years, and we have not seen this event. So I think we probably need to refocus what we think is the major
problems here.
CHAIRMAN
SALOMON: So I am comfortable with that
as a statement to end the discussion on numbers. Is there anyone who -- Claudio?
DR.
BORDIGNON: Yes. I would like very much to support this point
on the basis with two observations.
First, as you probably remember, we have one patient with a relatively
low dose who didn't engraft, meaning that there is no marking outside
T-cells.
But
T-cells are a hundred percent transduced.
So we have to keep in mind that these are very specific biological
situations in which the selective advantage for cells that can grow a bit
better to the next cell, it is enormous.
And
it is even probably stronger in the gamma-chain than in the ADA form because of
the mechanism of the selection. So I
would like to share with you a comment that actually came out during the
European gene therapy meeting a few months ago on calculating the total number
of the reconstitution, and the number of events, and so on and so forth.
And
one of the speculations that came from the floor was actually that if you give
a relatively low number of cells, but you have a very strong selective
advantage, you are going to fish out and give the maximum pressure to the cell
that has a growth advantage.
So
you are actually putting yourself in the situation in which potentially you are
favoring a transformation event. Of
course, this is just a speculation, but in a way I want to agree with Ken. I think that we have to look at the biology
of the system.
Otherwise,
we can argue one way or the other, and we really don't know.
CHAIRMAN
SALOMON: Just to put this in the
context, John, the point here isn't to argue about anything. The point is just to have as clear an idea
of the different kinds of facts.
And
one fact set here is numbers, okay? And
the issue is how many cells are infusing, and how many cells were transduced,
and how you activated them, and those are very relevant.
Now,
I agree that the discussion has to go on now and talk about the vector, and
talk about the gamma chain, and talk about the disease, and that is where we
are going to go.
But
just as you say, Claudio, the numbers are there, and you have got to put them
in a context and then set them aside clearly and move on. And I am okay with doing that, but I want to
make sure that it does not keep coming back in the discussion to haunt it the
way that it did for the first hour.
John.
DR.
COFFIN: Let me make one hopefully last
response to that. You can't select for
something that isn't there. So in my
mind as I think about this right now, the only way that this problem can be
overcome is to try to arrange things so that that integration is not in the
population of cells that you put in.
And
I suspect that I will come down with the idea that only if we can do that can
we -- if only we can do that can we -- only if we can come up with a strategies
that have a good chance of doing that can these things be considered safe
enough to go forward with. That is my
position right now and that may change at the end of the day.
CHAIRMAN
SALOMON: Well, we will see where we are
at the end of the day I guess that is the point. Okay. Thank you,
John. So I would like to go on to the
public hearing part of the morning, which should be brief. But we have three speakers.
The
first is Dr. Donald Kohn. Is Joe
Glorioso here as well? No? Okay.
Don is representing the American Society of Gene Therapy, and is going
to present some data that the ASGT came up with.
DR.
KOHN: Which hopefully will shed some
light, but maybe not. The American
Society of Gene Therapy is a scientific society that was founded in 1996, and
it has over 2,500 active members, 71 percent of which are in the U.S., and 38
other countries are represented.
And
the purpose is to engage exclusively in scientific and educational activities,
including promoting professional and public education in all areas of gene
therapy. Next slide.
And
so in response to the news of this second adverse event, we discussed what our
response should be and could we do anything to help. And before even the second LMO-2 integration site was formed or
was identified, we discussed forming a subcommittee to help inform the debate
on the causes, risks, and solutions to leukemogenesis.
In
other words, as it was discussed at the last BRMAC meeting, to help to find the
denominator. What is the -- what are
all the data that these cases are divided by, and so we developed a plan to
collect all the relevant literature and as much available unpublished data as
we could.
And
so we are in the process of accumulating data in three areas; in gene transfer
studies in mice, and especially focusing on immune deficient mice in gene
knockout models; and in large animal studies of retroviral-mediated gene
transfer of hematopoietic stem cells.
And
the clinical trials involving human subjects.
And our plan then, is that once this is accumulated to publicly post it
at the ASTG website, www.astg.org. Next
slide.
And
so a subcommittee was formed with three main groups, as well as some other
people just to give overall guidance. And Michel Sadelain and David Bodine have gathered a large volume
of data on all the relevant murine studies.
I
will just give you in my talk just a little introduction of some of the
findings. Cynthia Dunbar and Hans-Peter
Kiem have accumulated as much of the world's information on large animal
studies, a group of us are attempting to collect as much clinical data as
possible. Next slide.
And
so I just want to tell you a little bit about some of the murine data, and this
is has already been written up by Michel and Dave in a really scholarly
overview of all of the studies that we will post. Next slide.
And
so they focused in six areas looking at studies that have been done in murine
models of SCID, both natural pathogenesis, as well as gene correction. And looked at marketing studies in murine
and hematopoietic chimera, and in non-lymphoid murine disease models. Looked at questions of tumorigenesis and
transgenic in naturally occurring immune-deficient mice.
Tony
Blau wrote a subsection focusing on what is known in studies related to efforts
to expend stem cells or select them to get at the issue that Claudio was just
addressing.
They
have looked at murine models of insertional mutagenesis that lead to
hematologic malignancies and try to ask what can we learn from those to
understand these cases.
And
they have looked at the studies where leukemogenesis or lymphomogenesis have
occurred in transgenic mice where either oncogenes or fusion genes were
inserted as transgenes and what do they tell us about these cases. Next slide.
And
just a few of the highlights from the study.
This group, including Fabio Candotti, have identified at least 80 X-SCID
mice that have been transplanted with retroviral-medicated gene transfer, and
that have been published in at least another 53 or more from unpublished
series.
And
what stands out in all these animals is as you have heard to some extent from
the previous speakers, there were no serious adverse events, like
leukemogenesis. And in their discussion,
they talk about the benefits and limits of this model for predicting the human
disease.
Brian
Sorrentino reviewed the JAK-3 kinase deficient SCID mouse model, and in fact
reported that there is a high incidence of spontaneous T-cell leukemia even in
untreated or non-vector just transplanted animals, and the rate did not seem to
be increased with retrovirus vectors.
And
in a review of some of the insertional oncogenesis literature, there is
actually LMO-2 is a rare target for insertional leukemogenesis. I believe they spoke with Dr. Neal Copeland,
who has had several hundred integration sites that have been analyzed, and
LMO-2 was seen in only one of them.
And
so again it is a rare target, and I think that may be informative. Next slide.
The
large animal data, there is a large amount of this, and Cindy and Hans-Peter
have again accumulated this data into tabular form, as well as text that sort
of comments on it. Next slide.
And
so there have been gene transfer studies done in non-human primates, dogs,
cats, sheep, and pigs, both gene transfer, hematopoietic stem cells, or
lymphocytes, as well as direct vector injection.
And
these models I think have great relevance to the human experience, and their
comparable life expectancies unlike the short life span of mice; similar
hematopoietic demands, the reagents are cross-reactive, and the gene transfer
efficiencies are similar to those seen in clinical trials. Next slide.
And
so their method was to, first of all, go through PubMed to identify and review
all the published articles and then to directly query all investigators known
to operate large animal facilities, able to perform gene transfer and
transplantation regarding questions of long term follow-up in unpublished
toxicity that they may have observed.
And
then there was a detailed analysis of cohorts that have been followed the
longest times, so multiple animals followed more than one year, with blood
counts, gene transfer levels, LAM-PCR in some of them.
And
this is primarily sets of rhesus animals at the NIH, and baboons and dogs at
Seattle. Next slide. And again just a couple of the
highlights.
From
this they were able to ascertain at least 46 rhesus mecaques, with a mean
follow-up of 3 years after a gene transfer by retroviruses. The median number of CD34 cells was 82
million, and the animals have all had normal CBCs and are healthy, except for
transplant related complications.
And
the clone number in 20 animals has been a median of 30. That analysis is still ongoing. At the Hutch in Seattle, 21 baboons have
been followed for a mean of 2.3 years, and receiving a median of 60 million
infused cells, and again these animals have been healthy; as well as another 12
dogs have been followed for a median of 2 years, receiving 170 million CD34
cells, and again no adverse events have been seen. Next slide.
From
the clinical trials, this is a little more difficult to get the data, so far we
have obtained data on 38 clinical trials in which hematopoietic cells were
targeted, with at least 218 subjects that we have ascertained existing.
Thirty-one
of these were in the U.S. and six were non-U.S., and I believe that there are
more outside the United States that we don't have. Six of these were gene marking studies in the setting of
autologous bone marrow transplant for a variety of malignancies.
And
six of these were chemotherapy resistance genes, and again in the setting of
autologous transplants for malignancies.
Six of the trials were for HIV or AIDS, and 17 were in genetic diseases,
and eight I guess were for SCID, and then other genetic diseases. Next slide.
And
again just to sort of summarize what has been seen from all of these studies,
there have been no serious adverse events observed related to the vector other
than the two cases in the X-SCID study.
However,
there are a number of caveats. Most
yielded quite low level of marking for a short duration, and in many of the
oncology patients were done at an advanced disease stage.
And
the one number -- the one finding that sort of sticks out is what has been
discussed extensively, is that the absolute number of cells given to the X-SCID
patients are within the range given to many adult patients.
So
that if you look at a insertional oncogenesis model, it would not be consistent
with that, but the cells per kilo were higher, which really suggests that there
is something about the biology of these patients' marrow that may be a factor. And such as disease status, age, or bone
marrow. Next slide.
And
so for the clinical data, most of the relevant published data have been
assembled, and accrual of the unpublished data is somewhat slower due to one
element is that some groups have expressed, IRB concerns about releasing the
data.
So
we are asking for a minimum of just of the number of subjects that were
treated, or referral to published abstracts.
We need to collate the data with the non-U.S. data, and we have made
contact with the European Society of Gene Therapy, who are undergoing a similar
effort to obtain this data.
I
have spoken with Armand Keating at the International Bone Marrow Transplant
Registry, which I guess you heard about yesterday, and they have formed a
working group to begin prospective collection of data from clinical trials
involving gene transfer to hematopoietic stem cells.
And
so hopefully what we have done can be turned over to them to sort of form a
nucleus of this effort to collect these data in a prospective manner.
And this will be an ongoing effort by ASGT, with
a goal of completing it by our annual meeting in June of 2003, although we hope
to have the material posted on the website within the next few weeks of what we
have so far. Next slide.
And
so just one slide of recommendations, and that would be important to
standardize data capture as we try and get data from the different trials. Different data have been recorded in
different studies, and so not everyone has CD34 cells per kilo, and transduced
CD34 cells per kilo, et cetera.
And
the specific questions need to be asked for specific vectors, cell targets, and
routes. And I know that the RAC is
developing a database, and at the present time it does not have this kind of
information in it, and this may be useful to help them formulate their later
stages of the database.
And
that finally we would recommend a continued need by the NIH and other funding
agencies to support cores for clinical trial monitoring if it is now going to
be a mandate for the studies, and support will need to be done for these
studies, which are expensive, despite the ease that they seem to be done by Dr.
Von Kalle, and in fact they are a lot of work.
We
need to also support long term observation of experimental animals for late
events, especially large animals.
Keeping these animals alive after the study are very expensive, and so
often they are euthanized 6 months to a year after the gene transfer study is
complete.
And
with the events occurring later, we need to specifically support that. And we need to support basic science studies
to look on the risks of integrating vectors, and the role played by specific
transgene products, stem cells in different disease states, as well as
developing safer methods, such as non-integrating the persisting vectors, site
specific integration, insulators, suicide genes, et cetera. Thank you.
(Applause.)
CHAIRMAN
SALOMON: Thank you, Don. The next speaker in the public record will
be Dr. Rachel Salzman of the Stop Adrenoleukodystrophy Foundation. Rachel.
DR.
SALZMAN: Hi. Good afternoon. I would
like to thank everybody for giving me a couple of minutes here. I just wanted to make a couple of
comments. The first one is adverse
events.
Obviously
this is what started this whole thing is addressing these recent serious
adverse events, and I just wanted to comment that in the whole modern history
of experimental medicine, we have always encountered serious adverse events,
and over the years there have been methods developed of analyzing them.
And
the reason that I am bringing this up here is because there has been sort of
this chatter in the professional gene therapy community, and in the research
gene therapy community, about concern of maybe the potential for over-reaction
more globally to one particular category of adverse events.
That
has not come out of this committee at all, but I just wanted to make the
committee aware of that. I know that in
the history of cancer that there has always been adverse events, and that led
to the development of the NCI toxicity index, and so there is a paradigm or
methodology for handling that.
Another
example is they have been doing some clinical trials with erythropoietin, and
one form was found to be causing aplastic anemia, which is obviously quite
serious.
And
so that form of Epo was addressed.
However, it didn't really have a significant impact on other Epos or
other growth factors. So it didn't
really radiate out that widely.
And
when we talk about retroviral vector in the way that the questions were
designed by the FDA, retroviral vector is not a generic term. I mean, it depends on whether there is an
LTR, and when you say retroviral vector, there is many versions of it.
And they don't all behave identically at
all.
And
so I think that also should be remembered.
My second area of comment is on the importance for this committee to
devise guidelines or recommendations for groups that are interested in moving
forward.
Fortunately,
there is a lot of preclinical work ongoing with many different groups and
institutions around the world, and that is very positive.
But
the only way that all of that preclinical data can be useful to patients is if
it gets translated to a clinical trial.
Now, clinical trials are very expensive, and for rare diseases clinical
trials even become more rare.
I
know personally of a case where a group of Canavan's patients wanted to have a
gene therapy trial, and I know at least one family had to remortgage their
house to pay for it.
And
I don't think that is the way that we want to go. That just is not where we want to be. So it is very important that we have industry participation and a
willingness for them to be part of these types of efforts, and that also
academia gets a perception of support from the regulatory community.
And
when these parties here blanket limiting recommendations or comments, again not
necessarily in this forum, but they come out of other forums, it has a very
chilling effect on them, and makes everybody want to put on their breaks.
And
it stops also some very brilliant and thoughtful investigators from thinking
about moving forward, and investing their time and their brain power into
trying to advance a clinical trial that they might believe in.
So
I would like to respectfully request that the BRMAC issue recommendations in
particular to Item Number 4, which I know is on the end of the list, and you
have time constraints, because we need to think about these disenfranchised
patients that may benefit from these more novel constructs, these more novel
approaches, because they have got fatal, rare diseases.
And
the risk benefit ratio is sort of easy to calculate for them, and they really
need all the help that they can get.
And I would like to hear the Agency be able to promote a climate that
industry and academia will then find encouraging, and they are going to want to
participate in clinical trials, and invest in them moving forward.
No
matter what, I think that clinical trials need to be conducted in a safe and
rational fashion, and we have to consider like we are discussing today what
disease we are talking about, the age of the patients, certain numbers that I
am not going to get into; vector constructs, the transgene product, and risk
versus benefit for each particular disease, and obviously a program or protocol
for patient monitoring.
Nevertheless
we really think that future gene therapy clinical trials should be conducted,
and that is a message that we would like to hear, and we would like to have
everybody else hear that also.
Because
the bottom reason and the bottom line is that there is a lot of sick and
affected patients out there that are counting on you to make these
opportunities available to them.
And
their outlook right now is very, very dismal and poor for many people. So they are counting on you. I think that is about it, and I would just
like to thank you very much for your time.
(Applause.)
CHAIRMAN
SALOMON: The third scheduled speaker is
Dr. Richard Junghans from the Beth Israel Deaconess, Harvard Med School. Dr. Junghans.
DR.
JUNGHANS: I will have three minutes of
slides and two minutes of comments.
This follows very well upon the prior speaker's comments, where we want
to be sure that other areas get represented in a way which balances their risk,
versus the potential benefits.
So
today most of the conversations obviously have been about genetic diseases, and
the use of stem cells. There is a large
group of investigators now who are going into the cancer area, and using mature
T-cells as targets for modification in directing the immune system against T-cells.
This
is one protocol which I just want to briefly give you an overview about, and
then some comments that I would just like to follow up with. We chose as an antigen for targeting the CEA
antigen, which is on colon and rectal cancers, as well as breast and lung
cancers, and you can see here a high expression in tumor versus low expression
in normal colonic epithelium.
And
so to target this our approach is that we take an antibody directed against the
CEA antigen, and graft it on to the zeta-chain of the T-cell receptor, and we
use the MFG retrovirus kindly provided by Dr. Mulligan, to package this
product, and then express it in patient T-cells.
So
the idea here is that we have a patient with a tumor, who takes their T-cells
out, or the normal TCR repertoire, and we do ex vivo gene therapy, and modify
as many as 10 to the 9th T-cells, and expanding them up to the 10 to the 11th
cells, and infusing them into the patient.
And
then hopefully the tumor is targeted and eliminated. In our first generation product we ran a Phase I study and this
represents a patient who had metastatic rectal cancer, with mets to liver,
lung, and a large pre-sacral mass was extremely painful, and his serum CEA was
rising from 800 to 1,300 over the time that we prepared his cells prior to
infusion. Normally it is below five.
And
at the time that we infused these T-cells, he was bedridden on narcotics, and
nausea and vomiting, and very bad protoplasm.
A week later after T-cells were infused, his CEA dropped by 50 percent,
and he was up and ambulatory, and pain free, and off of narcotics.
And
for a period of about a month he had an improved performance status. His life was better, but this highlights the
potential of this approach, but also a limitation of it. That it was time limited in efficacy,
whereas, a good immune response, which we use every day in fighting viral
infections, will persist and amplify in accord with the threat.
So
we had here this chimeric immunoglobulin TCR cell receptor delivering signal
one to the modified T-cell through antigen recognition on a tumor cell.
We
knew that this led to the activation of cell death in the absence of signaling
the CD28 molecule, and this is a stimulation and post-stimulation.
And
what we did is that we have since prepared a molecule which incorporates CD28
and the T-cell receptor into one molecule so an antigen is recognized. We get signal one and two, and we have shown
that this leads to actual T-cell proliferation in contact with tumor cells, as
opposed to activation and new cell death.
And
this is what we want to be in a complete immune response in vivo against a
tumor, and that is done by taking this molecule and inserting CD28 signaling
domains here.
In
an animal model, we are looking at tumor growth here with a CEA positive tumor
in mice for a certain number of days after tumor injection. We inject T-cells, which are either
untransduced are first generation without the signal two, and then a tandem,
which is signal one plus signal two.
The
untransduced T-cells have no effect on tumor growth, the first generation slows
the tumor, but the they all grow; whereas, we have no tumor growth whatsoever
in the second generation designer T-cell treated animals.
CHAIRMAN
SALOMON: You're getting pretty close to
the end of your three minutes of slides.
DR.
JUNGHANS: Yes, this is it. Okay.
So in an established model, we have CEA negative and CEA positive
tumors. And you can see after 10 days
in the untransduced T-cells they grow.
And
10 days with the -- you get a partial remission with tandem T-cells, whereas, a
CEA negative tumor continues -- is growing, and in other mice, they did not
have the CEA negative tumor, and at 70 days, you can have complete tumor
elimination.
So
that is the end of the slides, and we now have a Phase I study set up for doing
second generation designer T-cells in colon and rectal cancer with possible
extensions of applications.
This
will be the vector that will be produced by Ken Cornetta at the National Gene
Vector Lab. So three points I want to
make. One is that we are working with
mature T-cells.
We
have heard from prior speakers that there is a reason to believe that these
mature T-cells could be at less risk for leading to leukemia when these are
transformed.
We
don't know that for sure. We need more
data. But at least there is a reason to
believe that. Also, these T-cells do
not survive, except if you maintain IL-2 present in the patient, and if you
don't, the T-cells die off within a week.
So
that gives us a little bit of a safety margin.
The second point is extremely important. There are no instances in which a metastatic rectal or colon
cancer, or breast cancer patient, has been cured. They all die, 100 percent.
They
may die in 3 months, and they may die in a year, or even 2 years, but they will
all die. This is a group of people who
are highly motivated to participate in some kind of rationally designed study.
And
the final point, which is almost the important one, is that we don't want to be
-- echoing the prior speaker's comments.
It would be a misfortune if we were so to regulate this area as to
prevent these patients from having the right to decide, as you said to
disenfranchise them.
In
other words, these are adult patients, and they are fully competent. We can even tell them that there is a 20
percent chance that you will get leukemia in 3 years.
These
patients aren't going to live that long, and if they were, they would be
willing to take that chance. And that
is all that I have to say. Thank you.
(Applause.)
CHAIRMAN
SALOMON: The fourth speaker scheduled
for the public session is Mr. Paul Gelsinger.
Paul.
MR.
GELSINGER: Thank you, Dr. Salomon. I am here representing CIRCARE, Citizens
for Responsible Care in Research; and my son, Jesse Gelsinger. CIRCARE is about accountability in research.
In
that regard, I would like to compliment the FDA and all the scientists here
from all around the world working together to try to unravel this mystery that
has cropped up.
I
would like to second the patient advocate's stance on taking care of these
patients. This is about people. But I would also like to temper her remarks
in unqualified support for ambitious researchers is not necessarily a good
thing.
Be
careful. Ambitious men may paint a
great picture, but the reality may be something altogether different. And I am waiting with bated breath to see
how you guys focus in on the age-related aspects of this.
It
is something that just jumped out at me early in this meeting, and in that
regard, I would like to ask a question related to the animal studies that have
been done.
It
is my understanding that they don't treat very young animals. So how relevant is that data in relation to
what you see in these very young patients?
Thank you.
(Applause.)
CHAIRMAN
SALOMON: In keeping with the policy of
these open public hearings, is there anyone in the audience who would like to
step up? It is not just the scheduled. I think, as you already know, my strategy or
attitude as Chair is always to try and make the audience feel as welcome at the
mic as the participants within reason so we can get our job done.
And
so if there are those of you out there who still feel later that they have
something pertinent, then please step up to a mic and just remember to identify
yourself, and I will do my best to keep track of the surrounding mics that are
outside the table area.
I
would like to now -- if there is anyone on the panel who has a comment. I know that Abbey -- I am sorry for putting
you off just a little bit, but go ahead.
MS.
MEYERS: I just want to say that I have
not heard any discussion at all about the ethical aspects of this whole
thing. I know that we are focusing in
on the science, but when I hear people talking about gene therapy as if it is
their last chance for themselves or for their child, I am bothered by it,
because actually in the 11 years of gene therapy experiments the only ones that
have been proven effective are these studies on gene therapy.
And,
of course, in the cases of the X-linked SCID, we traded one terrible disease
for another terrible disease. Now, the
goal of human research, of course, is to come out with a product, whether it is
a surgery or a drug, or a device, or whatever, that hopefully will be safe and
effective and get on the market.
We
have some drugs, for example, that are not safe, like thalidomide, but it is on
the market because there was a way to control that terrible side effect. If we don't let pregnant women take it, it is
a good drug.
In
this case here, I can't think of any company in the world that would want to
commercialize gene therapy when they know that there is a likelihood that a
percentage of those people who take this gene therapy are going to come down
with leukemia.
They
would not face the liability insurance problem in that.
And
so when I look at this whole thing, we are going down a road, and we are
looking at future clinical research on this, and I am wondering whether it
should all go back to the laboratory, and instead of using people, we should go
back to the mice.
And
the most disturbing thing that I heard this morning was the first or second
speaker who said, you see, they tried it in baboons, and they tried it in
monkeys, but it is very expensive to keep them alive. So we only followed them to 6 months or a year.
Well,
what was the cost of saving the money and not following those animals for a
longer period to see whether they came down with leukemia.
So
I am really disturbed, because I don't know whether human beings should be put
in this position, especially when a parent makes a decision for a child who
does not have the capacity to say what he wants and what he needs and who can
later grow up, like the babies from the DES mothers, and sue everybody. I just want to put that out on the table.
CHAIRMAN
SALOMON: Well, I think we acknowledged
last time, in October when we met, that part of the responsibility of the
committee in considering this was to relate as scientists to something that for
some of us is a potentially extremely important insight into oncogenesis.
It
is an important step in deciding the direction of different kinds of gene
therapies, all pieces of which you have heard.
But at the same time we acknowledged in October how important it was to
keep the ethical issues, which as we now think about it, between the public
comments and your comments, represents a bit of a --- represents two sides of a
coin.
And
I am not going to try and resolve it, but certainly on one hand you have
patients who are grievously ill or dying or have almost basically zero hope of
being alive in two years.
And
you have patients who -- or you have a community or a public that has other
interests. As you point out, Abbey,
should this stop now and not go forward into the clinical trials, and go back
into the lab.
And
I think that these are very important for us to think about. One way we deal with it is in informed
consent. So I think that we need to
make sure that we spend a few minutes on that.
So
I guess all I can say is that I am going to try and manage the next two hours
well. That is not going to be easy I
know, but to try and get through the science.
And I think that a lot of us in the field feel that there is a lot at
stake here about directions, and there has got to be some sort of statement in
that regard.
But
we are going to leave some time to try and maybe end on some of the ethical
issues. Okay. So we are going to let it go a little bit loose for a few minutes
just because people have a right to say what they want to say to start, and
then I want to go into the questions as shortly as possible. Joanne.
DR.
KURTZBERG: I have two comments for the
last two speakers. One is that SCID is
a disease that affects babies, and if you don't treat them as babies, they
often don't live to have access to other therapies.
So
you don't have the luxury of waiting until they are older, and that in and of
itself can cause harm. So treating
younger children is an obligation because of the diagnosis, not because of the
safety of the situation.
And
the second is that I think if you think of developing drug therapies and
devices in terms of the marketing and the commercial companies, that you do a
great disservice to patients with orphan diseases, because they are not a big
market.
And
they will never have these therapies developed for them because, safe or not,
they are not money-making propositions, and a lot of what drives our industry
of drug therapies and other therapies does not serve those populations.
So
I don't think that marketing or liabilities, et cetera, should be the reason
that we make decisions about drugs. I
think that's why government oversight is important.
That
is why the NIH is important because it takes some of that out of the situation
and allows these orphan populations access to developments of new therapy.
CHAIRMAN
SALOMON: Linda, do you still have a
comment? Then Tom and then David.
DR.
WOLFF: I wanted to make a comment that
is related somewhat to the ethics and to the informed consent. I noticed at the end of our last meeting in
October it was concluded that the informed consent should be more potent and
direct.
And
I was just reading the other night again what it said, and in the very
beginning of it, it says "expected to cause no harm." And even though there were statements made
after that about how a patient had gotten leukemia, if I were a parent looking
at that and didn't have much knowledge, I would almost stop at the
"expected to cause no harm," which was at the beginning.
And
I just think that it should be a little bit more straightforward and realistic.
CHAIRMAN
SALOMON: I am not certain exactly what
wording you are referring to, but the message from the committee in October was
that it should be very straightforward and not mince words about the fact that
gene therapy caused leukemia.
And
so I don't know. I would have to defer
to my FDA colleagues on that one. Tom,
and then David.
DR.
MURRAY: Thanks. And I want to take particular note of the
comments made by Abbey Meyers and by Paul Gelsinger and by the person whose
name I did not get.
CHAIRMAN
SALOMON: Rachel Salzman.
DR.
MURRAY: Rachel Salzman. Thank you.
It is not easy striking the right balance here. People who are dying or whose children are
dying of disease are desperate for a cure in many cases.
Certainly
many of the people, adults and children, who participate in first line clinical
trials will receive no benefit, and may even be harmed by their participation,
and that needs to be made abundantly clear to anybody who will enroll in a
subject trial.
And
I think that we need to make sure by the end of today that we give clear
instructions to the FDA, which I think is welcoming of these instructions, and
to be as firm and as clear as we can on that.
On the other hand, if there aren't any human trials, no progress would
be made.
I
do think having been involved in, among other things, a reexamination of NIH's
role in oversight of gene transfer research, that there seems to me to be a
world of difference between the way that we are dealing with this, and the way
that we dealt with -- or what was done prior to Jesse Gelsinger's death.
I
think that the openness of the investigators, and the candor, and the extensive
pre-clinical work that was done -- of very high quality --seem to me to mark a
very substantial difference in the responsibility that is being shown by the
scientists involved in this, and I just wanted to go on the record to say that.
CHAIRMAN
SALOMON: Thank you. David.
DR.
HARLAN: I wanted to applaud the first
presenter this afternoon, representing the American Society of Gene Therapy,
Dr. Kohn. I thought the way that was
put together was exactly the kind of information that I would like to see.
But
then in the public comment, several points were made that I wanted to make sure
registered with that group and that analysis.
And that is that age of animals be considered -- and that was Mr.
Gelsinger's point -- when the gene therapy was administered, and that the
duration of follow-up be especially paid attention to.
But
then in the clinical studies part, I find almost counter to the argument any
study that says that we have done this in 300 people, if the follow-up is only
a month or two. It is completely
uninformative.
And
I would argue -- I heard the point mentioned, but I would really emphasize that
you not even consider in the denominator gene therapy trials, or the duration
of follow-up, or the duration of gene therapy labeling, as uninformative.
And
that the committee come up with criteria before they even consider in the
analysis whether that is relevant data.
CHAIRMAN
SALOMON: Don, did you want to -- where
is Don? He's hiding. Oh, there you are. I saw you go that way at the end of your talk.
DR.
KOHN: I had to check out. In terms of the age of the animals, in fact
most mice typically are transplanted at 6 weeks of age, which is young,
although for a mouse, that is probably an early teenager or something.
So
there are now groups that are transmitting newborn mice, which might be the
most relevant time to get those kind of data.
In terms of the follow-up, what we were tempted to do is get all the
data with as much information about time-to-follow-up, extent of marking so
that it can be assessed.
So
this was just sort of a summation of how many studies we have gotten data
on. It wasn't a comment on the quality
of the data. And I did make one comment
that in fact in many of them, or the majority of them, the marking was very low
and short term, not much beyond 3 to 6 months.
And
so they are part of a denominator, but maybe not the most relevant denominator.
DR.
HARLAN: Just a comment. When you presented the clinical data, I
didn't hear you say that the committee was looking to identify criteria that would decide whether or not a clinical
study was informative for the safety question.
DR.
KOHN: At this point, we are just trying
to get the data as much as possible, and then once it's assembled, at the
annual meeting there is going to be a presentation of it in a symposium,
followed by a workshop to discuss it to maybe come up with some methods of what
to do with it. But the first step is
just to try and get it.
CHAIRMAN
SALOMON: Dr. Cindy Dunbar.
DR.
DUNBAR: Yes. I just wanted to make a couple of comments about the large animal
models. They are unbelievably
expensive. Ms. Meyers already alluded
to the horror that we were not following animals long term, but the program,
just for the infrastructure, is over a million dollars a year. And that is not buying the animals, and
that's not talking about any of the reagents.
I
am sort of amazed that I actually did have 46 animals that we followed for a
median of 3 years, and the only reason we were keeping those animals was
because of some other scientific studies that were not even related to gene
therapy, in terms of stem cell cycling, and I am very glad we kept them.
But
my facility has recently been told that we have to cut half our space, and just
simply in the current budget, NIH budget in 2004, there is just no money for
non-hypothesis driven non-investigator -- I mean, this is not something that we
follow the animals for ten years and were going to publish papers about it if
nothing happens. The FDA was wonderful
about following a group of animals that French Anderson had transplanted and
given vector to ten years ago. I mean,
he had given replication competent viruses to these animals and said, you know,
they didn't get the disease, so that is good.
It is not toxic. But those
animals turned out not to be very useful because the immune system cleared the
virus right away.
More
relevant were animals that got help for virus by mistake, more or less, and did
get lymphomas. Those studies we finally
shut down because it was felt that we had not learned anything from them ten
years after they had started, and I took the animals and used them for
something else.
But
I seriously don't know if we are going to be able to continue to follow these
animals. We had our breeding programs
shut down, so the whole issue of looking at young animals is going to be much
more difficult.
It
is very hard to buy -- you can't buy any new animals. They have to stay with their mother, you know, and we no longer
have a breeding program and neither does Seattle.
And
so these are big issues, but there is going to have to be creative funding
mechanisms through NIH or the FDA that is not your typical
investigator-sponsored RO1 grants or intramural investigator-sponsored things
because it is not possible in the current climate to do that.
And
the magnitude of expenses is horrifying, and that's why it was easy for me to
gather all the data because I know the 4 or 5 people in the world who have
these programs, and we are all holding on by our fingertips.
CHAIRMAN
SALOMON: Well, my comment to Abbey
about that is that you are doing good.
I mean, one of the roles that we can play here for the field in general
-- we have people here from the NIH, and certainly we have the FDA staff here,
and we do have people listening in industry as well to what we are saying. So you made your point.
MS.
MEYERS: The NIH got a 15 percent raise
for 5 years in a row, way above anybody's inflation, and I cannot believe that
they have cut back on their animal money.
It is unbelievable when they have gotten such huge raises.
CHAIRMAN
SALOMON: Well, in the two hours that
are left, we are not going to solve the NIH's budget woes. That much I am sure of. Dr. Bordignon.
DR.
BORDIGNON: Yes, thank you. Actually, I would like to make sure that one
of the aspects, the technical aspects related to the duration and level of
marking in relation to the safety studies is not overlooked.
I
sensed a couple of times through the discussion either public or during the
breaks that the threshold for considering a given animal or patient valuable
has to have a upper peak level of marking, and that level of marking has to
stay for three years, four years, or whatever was the crucial and critical time
in the gamma-chain study.
I
personally disagree on this point. I
completely agree with the statement that was made on this issue, that if there
is no marking, there is no toxicity to study.
But
if there is marking in the first place, the marking disappears, and the patient
or the animals is alive for evaluation, that marking disappearing means that
that cell that was tested was transduced.
It is just doing whatever biologically it is supposed to do.
Therefore,
it is dying at the end of its expected life.
I think that those data could be of different value, that long-term
marking and long-term expression, and long-term function, but they can be
extremely valuable, and I would caution against discarding them.
CHAIRMAN
SALOMON: Ken.
DR.
CORNETTA: I guess going through a
number of things that were said, one of the things that was brought up was that
the climate seems to be different than it had been with -- or at least the
climate currently is that the investigators are really trying to cooperate and
find this.
And
I think that is a credit to the folks in the field, and I have been
contributing my data to that also. I
think in regards to a follow-up of the ethical issues, while this formation of
leukemia is something that, you know, has been a sort of shock to the field, in
some ways it hasn't been.
And
I think that most investigators, including myself, have always included this
possibility on informed consents. And
the problem is that we have not known when it is going to occur. I think the thing to keep in mind is that,
with the committee and the other folks in the room, we have been doing trials
in this type of gene therapy for ten-plus years now.
There
is a tremendous amount of animal work, and I think there are some questions
about how long to keep animals, but probably every medical school in the
country now has some investigator doing retroviral gene transfer in some model
system, and this is not something that has been predicted with all of that
work.
I
think the real challenge for the committee today is why, with all of the work
that has been done and all the patients that have been treated, why in this
trial have we seen this, and how does that impact on the rest of the people
doing work.
CHAIRMAN
SALOMON: Cynthia.
DR.
RASK: Yes. I would just like to make a comment with regard to the informed
consent recommendations that we had sent out recently. We recommended that the investigators insert
a section entitled, "Risk of Cancer."
And
there is a statement that says that most integration is not expected -- or, is
expected to cause no harm. However, it
is followed by two paragraphs describing the potential risks and the events
that have occurred.
And
I would submit that, if patients stop at the point of that sentence and there
is no further discussion with the investigators and the treating physicians,
they are not really being informed fully as they should be.
CHAIRMAN
SALOMON: Well, I think that this whole
issue isn't one to run away from. I
mean, the strong recommendations of the committee in October were that there
should not be any equivocation in the informed consent.
I
think at the same time it was the intention of the FDA, in crafting that
particular language, not to create a situation in which it sounds like every
time you do gene therapy that you are going to get an integration event causing
cancer. And I think that was
responsible.
However,
certainly your comment, Linda, is reasonable, and we shouldn't run from that
immediately. I mean, if you feel that
it still is not unequivocal, when we come back at the end to talk about the
informed consent, you might want to readdress it.
DR.
WOLFF: Just a quick comment. In reading the two paragraphs, there was no
estimate of risk, which I realized was because we ended that session saying
that you could not estimate a risk, and that's why it was put in that way.
But
I was just trying to look at it as a parent, instead of a scientist, and how I
would interpret that.
CHAIRMAN
SALOMON: And I would just reiterate, the
intention is that we think that the people that are reading this that need to
get the message get the message. So if
you don't think that that was crafted properly, that is on the table then. Alice.
MS.
WOLFSON: Yes. I am here on this committee as a consumer representative, but I
am also the mother of a child who died from leukemia following a bone marrow
transplant, and one of the things that I hear missing from a lot of the
scientific discussions is the physical costs.
I
don't mean monetarily, but I mean the extraordinarily rigorous and physical
pain that not only, in my case, the child but an entire family and an entire
community endured for a bone marrow transplant which was really entered into
without sufficient informed consent, exactly what Linda is talking about.
As
a desperate parent, you are not going to notice the second paragraph, because
you are already thinking that you know you are doing something that is
desperate. And people talk to you about
statistics, Well, somebody makes it.
Statistics are meaningless.
Well,
they are really not meaningless, and I think putting that section second in
that way makes the argument that statistics are meaningless, and I don't think
that parents and children should be put in that position.
CHAIRMAN
SALOMON: Abbey.
MS.
MEYERS: I have had an 11-year argument
with Phil Noguchi on this problem, because Phil says in public -- and if you go
back to the minutes of RAC meetings ten years ago, eight years ago, five years
ago, you will see this argument in the minutes. Phil says that the FDA has no governance over informed consent
documents. He cannot force -- the FDA
cannot force a university to change them.
You can advise them, but you can't force them; is that correct, Phil, or
has it changed?
DR.
NOGUCHI: Legally, the jurisdiction over
the status and the form of the informed consent is the jurisdiction and
approval by the local IRB. That's
correct.
MS.
WOLFSON: I will just answer that a
little bit. It is not an answer, but I
can tell you that if the FDA has a very, very strong informed consent
requirement, then beware if you are an institution that doesn't enforce it,
because legally you open yourself to exactly the kind of lawsuits that you were
talking about from DES daughters, where in fact the reason they won those
lawsuits and are winning them is that the drug companies knew what they were
doing and did it anyway.
CHAIRMAN
SALOMON: Crystal.
MS.
MEYERS: But each university has its own
IRB and does it the way that they want to do it, and we don't have a federal
law that requires some kind of punishment if you don't do it that way. And the FDA is not legally empowered to do
it.
CHAIRMAN
SALOMON: Abbey, again, we are not going
to solve that either. That is the
American way right now, and it is more now than it was a few years ago.
Crystal.
DR.
MACKALL: Yes. I guess to echo this informed consent, we could talk about this
all day and more, but I am a pediatric oncologist who deals with lethal cancers
of childhood on a daily basis and go through the informed consent process
firsthand with my families. And our IRB
at the NCI is very strong and insists that every possible negative event that
this child can go through is there in black and white staring these families in
the face.
And
the fact of the matter is that under most circumstances the families don't have
a lot of options. That is part of
having one of these terrible diseases.
So in some ways I think we overestimate what the informed consent can do
for our families.
I
think the goal of this session here is to decide whether we think that first
sentence is true, that we expect that the likelihood of this is that there will
be no harm.
If
we don't think that is the case, then all the informed consent in the world
really does not matter. We have to
believe that sentence is true, or else we don't go forward.
CHAIRMAN
SALOMON: So my view here is that we are
kind of, in a natural way which is good, coming back to what we need to do now,
which is to discuss the questions. And
I promise, Abbey, that we will come back.
And
the only thing that I am not going to try and do is solve problems that are way
outside this advisory committee, not when we have such limited time. Rich, is this relevant to getting to the
questions?
DR.
MULLIGAN: No, but it wasn't as
irrelevant as the last ones.
(Laughter.)
CHAIRMAN
SALOMON: I assume that includes my
comments.
DR.
MULLIGAN: Definitely. This is about Dr. Fischer. You know, we were talking about how the
field has shifted, and I want to make sure that people have a sense of the
impact that his forthcoming has had on the field.
I
would say that if there is a single person over the last couple of years that
has influenced the course of the field, it is him. And I want to make sure that everyone is very aware of how upset
he has been very recently about the circumstances of the release of the
information about his patients.
Now,
I don't want to argue about it, because I know that there are a lot of issues
of getting the information out to people, but I would just make the point that,
had he not been as forthcoming and had he not led a very open transparent
analysis of what has happened, we would be so far behind.
And
I think that -- I mean, I can think of many other situations and other places
where this could have happened, where we would be so far in the dark that it is
not even funny.
So
it is just a pitch to everyone to be thinking about this issue of how unique
his contributions have been, and the issues that he will face in the future if
there is a third case or a fourth case.
I
just know because I have talked to him personally that he is very, very
concerned about how he makes public information. He is not under jurisdiction with the FDA. So I hope that people can just -- the
respective bodies can think about this issue because he is a very, very
valuable and important resource for us to have.
(Applause.)
CHAIRMAN
SALOMON: Agreed. Okay.
The first question is to -- Carolyn, do you want to project those?
"Please
discuss under what conditions clinical trials using retroviral vectors to
transduce CD34 positive hematopoietic stem cells for the treatment of
SCID" -- this is for the treatment of SCID, not X-SCID specifically, but
SCID -- "may resume.
"Currently
before sponsors of these trials may proceed with clinical trials, they need to
provide a revised informed consent document and plans for monitoring peripheral
blood cells for the clonality of vector integration. Is this sufficient or should additional conditions be placed on these trials?"
And
then there are a couple of things that they want us to consider. Let me throw it to the group.
And,
again, remember that we want to move forward from where we were in October and
not go over all the old ground. So we
all remember what happened in October.
Is it sufficient to open up the SCID trials that a revised informed
document -- well, we all agree with that, right? I mean, I don't think we need to waste any time on that.
Any
revision of the informed consent document that captures the integrity of what
we were trying to do in October -- and I have heard very clearly now -- is
okay; right?
So
how about clonality of vector integration?
How feasible is this? How
accurate is it? Should they do it? Is that enough? Rich.
DR.
MULLIGAN: Well, I think it would be
helpful if we just first addressed the kind of philosophical question about
what is different at this meeting than was at the previous, because otherwise
we are going to redo -- I thought we had actually an organized discussion
previously, we had good consensus, and everyone felt very happy about most
everything.
And
unless we kind of understand what is different and how that will influence the
decisions on these points, I am not sure that we are not going to be doing a
worse job this time just by the randomness of it.
And
I was going to say that what I think is different is that there obviously is a
second case. We now know that. Before we could have said that this would
never happen again and that it was a random thing, but it has happened another
time.
There
is much more information scientifically about the characteristics of the
disease. We obviously have addressed a
lot of points about cell dose. But I
think it is very key to also address this issue of safety. I know that John made some comment earlier,
that I don't know that I can support his, you know.
I
mean, I think that is very important for people to be thinking about, now there
are two cases of leukemia, is a point of view that there can't be a third case,
as opposed to the issues about how to judge risk and benefit.
And
I would just like some discussion by people on the issue of what is different.
CHAIRMAN
SALOMON: Bruce, and then John.
DR.
TORBETT: I tend to agree with
Rich. I mean, I think what we heard
today is that we have very little, other than perhaps culture conditions, to
base what is different.
We
do know that, unfortunately, another individual came down with that
debilitating disease. However, trying
to set a bar or readjust a bar I think is going to be very, very difficult.
And
I guess I would again like to echo the point that Rich made, that until we have
some idea or a discussion of what the differences potentially could be, I am
not sure that we are not -- I think we are moving, if anything, backwards.
CHAIRMAN
SALOMON: John.
DR.
COFFIN: In the last discussion we had a
fairly long discourse on denominators.
When you have one out of nine that the real denominator could be a thousand
or a million, and it could be a fluke; when you have two out of nine, the real
denominator is nine.
And
that is a hundred-fold, thousand-fold, change in one's thinking in a way. Because I think we can have some confidence
that if this protocol were to be repeated exactly this way in another similar
group of patients, we would be looking at exactly the same thing going forward.
And
so I have a lot of trouble seeing -- I'm wrestling with that. Before, I was quite enthusiastic about
continuing these studies because of the likelihood that it really was a flukish
experience.
But
now I think we really have to come to grips with what we need to do and what
steps need to be taken to try to prevent this from happening in the
future.
You
know, we are not going to send the space shuttles back up until we figure out
what went on with the Columbia, and I don't -- I think we would be derelict in
our duty if we didn't make a real effort to come to grips with some technical
way to deal with this, rather than just saying we should keep going along as we
are.
I
don't think we can afford to do that at this point, with these kinds of studies
at least. I mean, there are other kinds
of studies we can consider.
CHAIRMAN
SALOMON: Okay. There are hands going up. Usually, in all other BRMAC meetings -- it
sounds like Passover for those of you who get that joke -- but in all our other
meetings, we obsess about how we have got to get to the questions.
I
am actually okay with this little more freewheeling discussion, and since this
is my last meeting, you guys can fire me anyway.
(Laughter.)
CHAIRMAN
SALOMON: So we may not get to your
exact questions, but maybe we will. So
let's try something a little bit different, because I think that there are some
points here. There is so much that is
important here.
So
I have Ken, and Alison, and then Barbara, and then I think Bruce was waiting.
DR.
CORNETTA: I guess I was trying to get
to the question, at least for me, where we branch off and to start making some
decisions. Do I think that the
integrations that we have seen and the leukemia that has developed is this a
single hit that everyone who gets a gene transfer is at risk to?
Or
is there something unique about, for example, the transgene, in combination
with this, that really makes a very big difference on where we go? Because it also -- even the first question,
of what does this do for SCID, actually you might want to rephrase that.
If
this is -- if the transgene is playing a dominant role here, then actually even
non-X-linked SCID trials may not be at risk for this type of problem. So, for me, that is a real crucial point.
CHAIRMAN
SALOMON: Well, let's just try and --
just since there is a lot to go through, let's try and keep key points. So Ken's key points now are vector and
transgene. Okay. And Bruce seconds that. Alison.
MS.
LAWSON: I was going to say exactly the
same thing, but I would add a couple of more things into that. Because what John said was 2 out of 9, and I
think what we have to discuss is: Is
it 2 out of 9, or is it 2 out of 2?
Because we also talked about age, and we talked about dose, and so we
don't know if those other factors as well may be part of that.
CHAIRMAN
SALOMON: So as we evolve it now, the
question would be is there enough information, at least inferentially, allowing
us to say that there are specific groups within the group of X-SCIDs that might
be at higher risk.
And
age, dose -- well, no, that is on the table, and you can shake your head. But age and dose, and other issues. Barbara.
MS.
BALLARD: I was looking at much the same
question, and whether or not the first question looked at all of SCID, versus
X-linked, and breaking X-linked out from the other types.
DR.
LEONARD: A couple of the same related
ideas, but the one thing is that JAK-3 deficiency is clinically and
immunologically so indistinguishable from X-linked SCID that I think a JAK-3
deficiency must be considered in the same context as X-SCID.
IL-7
receptor deficiency, as far as I know, no one is doing gene therapy is related
to that, but it would also fall within the spectrum of SCID.
So that one question is to consider all SCID or
X-SCID. But if X-SCID is a breakout,
then I think that JAK-3 deficiency and IL-7 receptor deficiency should
necessarily go with it.
And
the age issue is very important. I
suspect that there are not that many here who would be enthusiastic tomorrow
transducing more children one or three months of age; whereas, if the question
is older children, there might be more room for discussion and greater thoughts
related to that.
CHAIRMAN
SALOMON: David, and then Jeff.
DR.
HARLAN: I am going to propose coming at
this from a completely opposite angle; and that is, I would be in favor of a
trial as long as there is nothing else to offer.
I
mean, if there is really nothing else to offer, then I don't see -- then the
risk/benefit ratio for me is easy, and this is where we did discuss this last
time, and I know at the DNA RAC, this is how it was approached.
If
there is no other therapy, then it is pretty hard to argue that the
risk/benefit ratio isn't -- even if it is infinitesimally greater benefit, then
it is greater than nothing.
CHAIRMAN
SALOMON: That's fine. Jeff.
DR.
FRENCH: It is inherently difficult to
extrapolate from mouse models to humans, but I wanted to go ahead and factor in
both dose that is the vector cell integration into pre-clinical studies,
because you don't seem to have any other options at this stage to proceed,
because you can't wait for any other preclinical studies to be done.
But
in the future, if you consider pre-clinical studies, I would want to give you
the benefit of what we have experienced over the past ten years in trying to
deal with safety assessments in both pharmaceuticals, as well as environmental
chemicals.
But
I was struck by Baum and von Kalle paper in terms of the potential rates of
integrants that could have an adverse event in a case, and it is very similar
to the spontaneous mutation rate in both the mouse and the human genome. It's not different, so something else is
obviously happening that drives that progress forward.
In
terms of what we have experienced, in terms of how do you define a model or a
battery of models that can help you actually address pre-clinical safety
issues, historically the carcinogenistic potential of a given chemical is dealt
with by looking at long-term studies in rats and mice, which is very time
consuming and very expensive, and probably not applicable to here, where you
have to address something very quickly.
I
have not seen anything today thus far that really shows that those studies in
mice that tried to address safety were done to the extent where you could come
to a conclusion about the actual safety.
But
there are a lot of models that are available, and we have seen the papers from
the Jenkins-Copeland lab using retroviral targeting that can identify potential
cancer genes, more oncogenes, and tumor suppressor genes. But they obviously do occur at some rate because
those were determined by pulling out tumor DNAs and identifying them.
So
there are obviously a lot of animal models that are available. So how do you do that? I would suggest that you actually need a
working group of people to define it.
And
we had a partnership between academia, industry, and government over the past
six years that sort of addressed that.
You have to build a consensus on how that is going to be done.
And
the more models that you bring into it -- and I am referring back now to the
list of models that we saw with the presentation from the Gene Therapy
Association -- you can inundate yourself.
We
spent six years and about $50 million to try just to find three models. I am not trying to equate the two, but the
point is that you have to be very circumspect and very direct by what you want
to get out of the outcome if you are going to use animal models to try to
determine a pre-clinical safety assessment.
CHAIRMAN
SALOMON: Okay. But again we have lost the thread of the questions. We said that was okay, but I am trying to
make sure that we do have a thread.
So
the thread so far is we have talked about the vector, and we have talked about
the transgene. We have talked about the
disease, and we have talked a little bit about whether there were -- you know,
how you would make the cuts. I mean,
SCID as a big group, versus type X SCIDs, versus types of SCIDs, okay? We have got to get to some place at the end
of this. Joanne.
DR.
KURTZBERG: You know, I think when people
are trying to figure out is if there is something different about these two
kids that led them to be more vulnerable to this problem, I don't think the
problem is two out of nine. I think the
number right now is three out of four.
Because
you have five kids, and the first one has the insertion, even though he or she
is not sick. I think the third one
didn't engraft, and then the other two have it. So time-wise you really only really have four children out the
same amount of time in which the event occurred.
And
then you have three or four more who could still be under observation, but have
not necessarily fulfilled the time for observation that this might happen
within. So I think you have to think of
it from that perspective when you start trying to figure out what the incidence
might really be.
I
think that first patient is going to be very important, because age is a factor
and if that patient does not end up with leukemia, that is a very positive
observation. But we don't have the time
yet to know that.
So
I think if this was an oncology study, you would say we have met a stopping
rule. We need to sit down and figure
out if we can make this safer and have a hypothesis about how to do that and
then reopen the study with whatever that change may need to be.
And
it may need to be that we have more time to observe the kids already treated
before you can make that hypothesis.
But
I think that that is the direction that people ought to take, rather than some
of the discussions that we have had so far.
DR.
MACKALL: Let me just comment,
Joanne. I agree with you that I can't
imagine that we can go from here today without saying that there has to be at
least some hold on this trial, because we don't have that many
person-years.
We
need the individual patients to accumulate enough time post-transfer to really
know what the incidence is, but in the meantime, you know, you are going to be
faced with some kids that don't have other options. So you as a transplanter -- I mean, what are you going to do with
that?
DR.
KURTZBERG: Well, that was the other
part of my comment. There are other
options for these kids. You could argue
about qualitative risks and benefits, but these kids could have haploidentical
transfers, and they could have ablative transplants. They could have cord blood transplants. There are donors available now to transplant these kids.
And
those are not necessarily less risky procedures, depending upon what the
incidence of this event really turns out to be. But there are options, and that should not get lost in the
discussion.
CHAIRMAN
SALOMON: Tom and Butch.
DR.
MURRAY: The last point gives me
pause. Of the ten children treated, if
we had seven positive responses and three non-responses, we would not be here
talking about it. In fact, what we have
is seven children at this point who I guess have responded positively at this
time, or at least no occurrence of leukemia, and one not responding, and two
with leukemia.
And
we need to be mindful of what the options are, both in terms of the percentage
of success, but also in terms of what it does to quality of life of the child
and the family. That point was made,
and it is an extremely important point.
These
are not data points on a chart. These
are children who have parents who are worried about the children and caring for
the children, and children and parents can suffer together.
And
some of the alternative treatment modalities can be fairly harsh I
understand. So we just need to weigh
that in the balance with whatever recommendations we make.
CHAIRMAN
SALOMON: I think we are actually
getting there. So, Jon, Richard, and
John Coffin.
DR.
ALLAN: I don't know that I have
anything different. I will maybe just
phrase it a little bit differently. I
mean, when you talk about all of these variables -- and they are all
variables. You can say transgenes, and
you can say dose, and you can say cells and you can say age, and you can say
vector, and you can say the target cells.
And
you can say all of these things, but at the end of the day these are all
variables, and they are not easy to separate, and so I think you are sort of
stuck in these SCID trials, in terms of trying to sort that out.
I
don't know that pre-clinical animal models are going to be able to give you
that information the way I think you want.
But what strikes me is the fact that even when you looked at one of the
studies -- I think it was Adrian's study, that compared umbilical cord blood --
well, I don't know if it was Adrian or whose study it was. But they said it was
equivalent, that the gene therapy was equivalent to the umbilical cord blood.
And
so that makes me sort of, like, pause and say, well, we keep hearing all this
other stuff that says the bone marrow transplants are 50 percent or 60 percent,
or whatever, but some of those are non-conditioned kids.
And
if you threw in umbilical cord blood, maybe you would get 80 or 90 percent, and
the quality might not be any worse than the gene therapy trials. So that suggests to me, then, that there are
alternatives at the present moment, which would mean that, with the fact that
you have got at least two leukemias, it is a no-brainer to me.
But
then you sort of have to break it down into what it is that you are -- if you
are going to keep a hold or put a hold on a trial, how much do you define it?
And
someone else suggested that, well, maybe we shouldn't include these SCIDs. Just these SCIDs. I don't know where to stop there, but I can tell you that if
there are alternative therapies, it is just common sense.
CHAIRMAN
SALOMON: Well, that is a good piece,
and we will come back to that in a couple of minutes. I think we are almost there.
So, Rich, and then John Coffin.
DR.
MULLIGAN: Yes. I look at the breakdown between the
scientific advice and the clinical advice that we have in this case. And at the previous session, I was just very
impressed by Rebecca (sic) Buckley and all the clinical discussion of the
risk/benefit, and also a little bit about the differences in the options, and
Joanne just entered that.
I
mean, in the previous talks that we had, there clearly was not a consensus
among the people that there were other options. It was clearly not put that way.
And so I think there is going to be a difference among excellent
clinicians about what those options might be.
Now,
I think what is different at this point, and I think we mentioned this at the
previous meeting, too. I think I may
have mentioned it specifically that I wouldn't be surprised if this never happened
again in other patient populations even if it happened to every one of the
children that was treated for this disease.
So
I think the scientific judgment that is different is that I think that the
message that we would get across is, based on what we see here, this is not a
random thing, and indeed it might happen to every one of the patients.
And
then I think we break that and separate that from essentially what is the
clinical judgment. I think there will
be variations. And with regard to the
FDA, I think from a scientific point of view, is it irresponsible at this point
for us to recommend that, scientifically in a way, you go ahead.
And
I think from the vector issues that will all surface at some point, we are in
no position to get there quickly, okay, for a lot of reasons, some of which we
talked about before.
So
that is not going to happen, and we need to let that happen, we want to
encourage that to happen, and then once there are vectors that have these
properties, as we have seen in the past, people gravitate towards these, and
there will be a consensus, just like the discussion about packaging cells and
old fashioned ones, and people tend to go to new things.
So
here I think the message that is very clear is that this could likely happen,
all ten. I think Joanne pointed out
that there is people that have LMO-2 in this trial, and that is not a good
thing to see.
But
all of that being said, I am not sure that necessarily interferes with a
clinical decision about how to go ahead with these patients. That is very different. I think it is simple to say that we have no
information from the disease that we are seeing in these kids to really suggest
that it will happen in other diseases.
We
just don't have information, and I think we will come to that.
CHAIRMAN
SALOMON: So hold that. I mean, I think that one of the things that
I would like to try and do is like sort ripples in a pond. So let's deal with this and then see how far
the ripples go out, which is where you are starting to go now. John, do you have a comment?
DR.
COFFIN: I have a couple, actually. In terms of where we cut our decisions, I
have a lot of trouble just because of our complete lack of knowledge of any
other system other than X-linked SCID really.
Cutting on SCID versus non-SCID, or X-linked versus ADA deficiency, the
cut that I would be willing -- or that I think we should consider more is
perhaps between stem cells and non-stem cells.
And
I think there we might be able to come to some agreement.
CHAIRMAN SALOMON: That is a good way of looking at this ripple
approach, so now you have rippled it all the way out to hematopoietic stem
cells and that's fine.
DR.
COFFIN: So that is one point. The other point is that as far as this
particular outcome is concerned, I think we would all be extremely upset if we
allowed trials in other diseases or in these to go forward, and this event
happened again.
And
the only way I can see that trials could go forward and that this would not
happen, that we could reduce the probability to something that we might be able
to live with is if the trials were allowed to go forward only with doses of
unique integration events that were small enough that the probability of there
being an integration next to LMO-2 or other oncogenes was low enough that we
could comfortably live with it.
And
I will just lay that on the table right now.
That may not be a wonderful option, and it needs a lot of research to
sort of come to a consensus on what those levels would be, but it is perhaps
better than putting indefinite holds on these trials, waiting for very large
amounts of sort of very basic research to be done.
And
we are talking about extensive research projects whose designs are going to be
difficult, if they are going to be really tightly designed to answer the sorts
of questions that we have. And so I
will just lay that on the table for the moment.
CHAIRMAN
SALOMON: Ken and Steve Rose.
DR.
CORNETTA: I guess, as you said, we are
wrapping up, and I guess I am ready to put out what I am thinking. In terms of X-linked SCID and JAK and the
Il-7 receptor, I think it would be very hard for me to enter someone in who had
other options at this point. And,
again, those are sometimes left to the clinician.
But
I think what I am hearing is really a consensus here, and that is really what
we need to do. We have to realize that
there will always be extenuating circumstances, and that we need to let the FDA
know that there are going to be that.
But
I think what I am hearing from the committee, and at least where I am coming to
is for these -- you know, we have a disease that is somewhat unique, and there
are other good similar diseases.
But
at least my recommendation right now would be that, if there is an alternate
therapy, those should be explored now.
CHAIRMAN
SALOMON: Yes, that's perfect. If the circle of this conversation is
getting us to the right spot, then it is working. Barbara, and then Steve Rose, and then Warren.
MS.
BALLARD: One thing that I want to bring
up, though, is Dr. Kurtzberg brings up alternative therapies, but the thing
that you are dealing with at this point in time is a child who has already
failed one type of standard therapy, whether it is haploidentical, PEG-ADA,
whatever. They failed the therapy.
And
so you are dealing with a child, who is not a healthy child, with a cellular
defect. You are dealing with a child
who has possible infections that you can't clear, and a child who probably has
organ damage, maybe multiple organ damage, and your optional therapy is to give
him chemotherapy.
DR.
KURTZBERG: First of all, the current
trial enrolls these kids as frontline therapy.
And one of the proposals on the table was, until the safety is better
defined -- and I think it should just be limited to the X-linked and the IL-7s,
et cetera --to say that it is not frontline therapy. It is salvage therapy or second-line therapy.
But
what is going on right now is that it is the frontline therapy. And at the very least it is now equivalently
risky as other frontline therapies. And
I think that should be on the table for families that have to make a decision
about treatment.
MS.
BALLARD: I just did not want to lose
the idea of it being a salvage therapy, too, because the alternative options on
salvage therapies aren't a hundred percent and are not great options, either.
DR.
KURTZBERG: And I agree with you, and
that may be the solution, to say --
CHAIRMAN
SALOMON: And that is a good example of
how these are circles. I mean, you can
go to saying it maybe is not the primary therapy and we ought to consider
options.
But
that doesn't -- and I think Barbara is right -- preclude that under the right
circumstances, it can be salvage therapy, and that is a circle that we should
follow. Steve, and then Warren.
DR.
LEONARD: Just a brief comment related
to John, and Christof could speak to this.
At the RAC meeting, he estimated that the target window for the LMO-2
gene was one per ten to the fifth.
So
that really is a low enough frequency so that, although limiting the number of
integrations would be desirable, you may not really be able to get the number
of integrations down to a sufficient level, if that calculation, is true to
really avoid the LMO-2 integrations.
That
is to say that lowering the number of integrations might not be desirable.
DR.
COFFIN: My calculation was one in a
million on that, so maybe we should talk to the RAC --
CHAIRMAN
SALOMON: It's one times ten to the
fifth, and then there are people arguing for first hits and second hits and
third hits. And to be honest with you,
I would like to just cut that off. We
are never going to get there.
I
am actually totally with you as a scientist, so we should put our heads
together afterwards and talk about this.
But I don't think that, as a regulatory principle or as an advice
principle, it is going to work at this point, and we will just drive each other
nuts.
DR.
COFFIN: Before we take it off the
table, could we just consider advising that a committee of some kind be put
together to specifically investigate this issue?
CHAIRMAN
SALOMON: I don't know if I am -- well,
sure, you can put that on the table.
No, I shouldn't do the Chair thing and cut that off. Does anyone think that there should be a
committee to investigate this? I just
am not certain what you --
DR.
TORBETT: I guess it should be tabled
until we make some of these other decisions first, but I do agree with John
that there should be a concerted effort, and it looks like the American Society
of Gene Therapy has taken the lead in that.
But there needs to be something done.
CHAIRMAN
SALOMON: I think we all agree that this
is really where the science is, and that is good. I think if we don't advise also in the context of where the
science should go, then we have not done the full job today either. Bruce.
DR.
TORBETT: I guess I would weigh in with
X-linked SCID. I think what I have been
convinced of, at least for the data here, is that it is as equally risky or
more risky than current conventional therapies.
And
so given that, I guess I would weigh in for it being, at best, a salvage
therapy at this point. This is not the
general SCID, but at least the specific X-linked SCID.
CHAIRMAN
SALOMON: So let's see if we can get
some traction on the first part of the circle, the inner-most circle, if you
will, by the end of the day. We have
only got an hour to torture this metaphor, and so I guess we can probably get
away with it.
The
X-SCID. And let's go with Dr. Leonard's
comment that within X-SCID there may be a couple of critical types that I guess
are a little outside the actual X-SCID group, like the IL-7 and the JAK-3, that
would be in the same way, where there would be such a powerful potential
selection element that a transgene would contribute.
Do
we agree that those right now should not be primary therapies for these
children? Is that a consensus? Are we voting actually today or just
achieving some sort of consensus?
DR.
NOGUCHI: I think the importance of this
discussion would warrant a vote on how people think about this. It is not meant to be binding in any sense,
but where we at the FDA want to be very clear is that we get the advice, and we
know the strengths of the arguments about it.
So a vote would be helpful, at least a vote for the sense of where
people would be going.
CHAIRMAN
SALOMON: I am trying to focus us down
just for the moment now on a clear statement from the committee about X-SCID,
with a little bit of a ripple out into a couple of other very similar molecularly
mechanistic types of severe combined immunodeficiency. David.
DR.
HARLAN: I want to make one last stab at
not going down that path, if I can, by challenging Joanne for her opinion. You said that there are always alternative
therapies, and you know that, in clinical medicine, you never say
"always".
You
know, let's say that there is no umbilical cord blood donor and that the parent
is CMV positive. You know, it seems to
me that you don't want to limit it to a specific disease if there really is no
other therapy available.
CHAIRMAN
SALOMON: But, David, I think what we
are saying here -- and it is important what you are bringing out -- is that we
are not trying to preclude someone who has got no other options and is going to
die. We are just trying to get at a
primary therapy. A kid --
DR.
KURTZBERG: I mean, a protocol can be
written with an algorithm. It's done in
transplantation all the time. If you
don't have a six-of-six match sibling, and you don't have a this, and if you
don't have a that, then you are eligible.
DR.
HARLAN: Then why try to limit it
further? I mean, why split it? It seems to me that is the critical place
where these should move forward.
CHAIRMAN
SALOMON: Well, we need to give a clear
message to the FDA, if we can. We can
say that we can't give you a clear message, and that is a message, too. But I think if we can give them a clear
message, then there are people -- there are sponsors who are stepping up to do
these trials, and the FDA can't avoid the need to regulate them.
So
they are going to have to say, we are going to give you an idea or not. And we have to give them something
here. Marina.
DR.
CAVAZZANA-CALVO: I have just a comment
on the definition of a salvage therapy or firstline or second-line. I think that it is a decision that can be
made by the clinician on a case- by-case basis. Because we can think that we can avoid in the future -- and this
is a reflection that we have had in France -- that we can avoid using gene
therapy for a newborn child of the age of the two with side effects that we
have had, less than 3 months, for example, and in good health because the two
cases had no infection at the time of the gene therapy. So in this case probably even haploidentical
bone marrow transplantation is good enough to hope to cure the patient.
In
the cases that you have, all these newborns, more than 6 months and severely
affected with multiple virus infections, herpes viral infection, and bacterial
infections. That is, pneumocystis
carinii at the time of the diagnosis is a common feature, and herpes virus
infection.
In
this case, haploidentical is not really a choice. We lose the child before you have the option of gene
therapy.
CHAIRMAN
SALOMON: Well, I think that this is
really important. I mean, you are right
at this point on how you define salvage therapy. But can we just get through the idea that it isn't salvage, then
define salvage?
DR.
CORNETTA: Well, I actually made the
suggestion that "if there is no alternative therapy," and I think
that is the word that you want, not salvage versus primary, because there are
going to be cases where it would be primary therapy, but, because of other
clinical indications, it would be inappropriate to take that patient to
transplant.
And
there may be other times where there may be other salvage therapy. So that's why it should be "if there is
no alternative therapy."
DR.
CAVAZZANA-CALVO: This is the
definition. Because in the case of
varicella-zoster, I can assure you that with haploidentical you lose the
patient before any alternative treatment can be made.
CHAIRMAN
SALOMON: Did you want to comment?
DR.
HIGH: I just wanted to say that before
I came here today, based on what I read in the provided documents, I had made a
decision. But based on the discussions
that took place, at least it seems to me that there is a possibility that there
may be something about the CD34 cells of very young children, of infants, that
would make a difference.
So
that I am not sure that it isn't correct what Alison said, that maybe this is
two out of two. And if I had one wish
for one more piece of data, it would be to fast-forward 18 months.
So
my point is that I would be willing to agree to what we are talking about now,
with the caveat that I get to reverse my decision in 18 months if it turns out
that no other children develop this sort of complication.
CHAIRMAN
SALOMON: Well, I would think that is a
good point, and clearly the premise is that you can only do what you know
now. My personal view of this is right
now with what we know about using this particular vector with this particular
transgene, in this particular disease, with this particular induction protocol,
is that we know that at least two of seven or eight, depending on how you cut
these numbers, got leukemia.
And
I don't know whether that leukemia is going to kill these children. I really don't. So one thing that I would love to fast-forward to is three or
four years from now and find out that these kids' leukemia wasn't as serious as
a T-cell leukemia in a kid.
DR.
KURTZBERG: But one of them is already
going to a transplant, the dreaded therapy that everybody is trying to avoid.
CHAIRMAN
SALOMON: Right. Where I am going here is that I don't know
how many more of these children are going to get leukemia in the next 18
months, which echoes something that Rich said, and something that you said,
Kathy.
So
I must say that from my point of view, not trying to be the chairman but just a
part of the committee, I am not comfortable at this point going forward with
these cases anymore, with using gene therapy.
I
am okay with doing it if you can convince me that there is no alternative
therapy. I am okay with that
caveat. I am always going to be that. I have done enough medicine, and I have
cried enough at patient bedsides to be there with you.
But
other than that, I just am not comfortable with it in this particular, very
narrowly defined group of people, only because -- and here is what is driving
that decision for me.
I
can, based on the data that we heard in October and the data that we heard in
the last day, say something about the risk of haploidentical transplantation,
and HLA identical transplantation, et cetera.
At
this point, I don't know anymore what the risk of gene therapy is in these
kids. I really don't know today. And based on -- knowing that it is serious
and not knowing whether there are going to be two or three more kids, given the
data that you all know, then to me it is moving off the table unless there is
no alternative. So that is kind of
where I am at right now.
DR.
MULLIGAN: I think the way that Joanne
put it was perfect, that it is now clear that, weighing this relative to the
other risky approaches or last-ditch approaches, it is clear -- the information
that we have is that it now clearly is a question whether these other things
are more risky.
So that is a big difference.
I
guess I would ask Joanne about this issue of clinical judgment and whether
there is any alternative therapy in the eyes of the beholder.
DR.
KURTZBERG: I mean, there is a lot of
criticism in that decision, but if you really think about it, when we talk
about haploidentical transplant in SCID patients, we are not talking about
conditioning. We are talking about
taking the risk that (a) they don't engraft, or (b) that they partially
engraft.
And
there is a small risk of GVH, but the biggest risk is that it didn't work, and
not that the child is worse off than they would have been without that
procedure.
If
you talk about the risk of cord blood or match related donor or whatever
transplant with appropriate regimen, then you have the inherent risk of the
chemotherapy, which is somewhat age- and clinical status-dependent, but can
range between 5 percent to 30 percent, depending on where the child fits in
that category.
But
I think the people who believe that haploidentical transplant has a role would
say that everybody has a parent, and everybody has that option.
Certainly
that option carries no more risk than what we are talking about now, which is a
20 or 30 percent risk at least, of a leukemic transformation. And again I think the risk of an ablative
transplant is equivalent at this stage.
So
I think that everybody has a haplo donor.
Ninety-five percent of people will have a cord blood donor. We have an 80 percent event-free survival
with full T- and B cell reconstitution in our immune-deficient population who
get cord blood.
But
I am just saying that these things are equivalent, and there are options for
everybody. And gene therapy should be
an equivalent option in that cascade, but not a superior option in that
cascade.
CHAIRMAN
SALOMON: Okay. You were going along okay, which I would
define as following the discussion, until that last little zinger. If it is at all an even playing field, that
is real different from saying we don't know whether there is now going to be,
in 18 months, two, three of four more kids, which now you would have to say
there was a 60 percent incidence of leukemia, versus a 20 percent incidence of
GVH for the cord blood or something. I
don't know, but that is the problem that I am having.
DR.
MACKALL: I think that we do have to
keep in mind Joanne hails from Duke, and this is the center of the universe
when it comes to transplanting SCIDs.
So it may not be the same everywhere that you are, and I think that
Marina has alluded to that.
You
have situations where you do not see haploidentical transplant as any kind of a
real option at all for your patient, even though they have a parent who is a
haploidentical donor.
So
I respect Joanne, and I believe what she is saying, but it may not be the same
in every center with differing levels of expertise with that therapy.
DR.
KURTZBERG: But we have data to fall
back on. I mean, I am not a
haploidentical transplanter, but the data with the haploidentical transplant is
--
DR.
MACKALL: But it is single-institution
data, Joanne. It has not been
replicated everywhere.
DR.
CORNETTA: These are also done under
IND. So the FDA does have an input here
of what are going to be the eligibility criteria. So I think we have to give them some credit to be able to look at
these protocols.
So
it is not like we are sending it back to a local IRB, and it is only one
institution that is making these decisions.
The FDA is going to have input here, so hopefully they will take our
advice.
CHAIRMAN
SALOMON: Okay. So one thing that I sort of see us coming
around to is -- the difficult thing is deciding for a given place, a given part
of the world -- in this case we have to deal with the United States, but the
United States is pretty large and diverse -- what it means for an alternative
not to be available.
And
that I don't think the committee is going to get through defining for the FDA,
nor frankly do I think we would be very
good at it, since it is going to be very individual.
So
I think that, in general, could we agree that every sponsor has the right in
coming forward with the design of their trial and their inclusion and exclusion
criteria to make the case to the FDA that this is the definition of when a
patient is eligible for our study, based on the precept that there is no
alternative available.
And
that might be a concept that this committee can agree to, and I think we will
get lost in the details of, well, if they are not at Duke... That's more like an exclusion criteria.
DR.
PUCK: I just wanted to make a quick
clinical point.
CHAIRMAN
SALOMON: Can you identify yourself,
please?
DR.
PUCK: I am Jennifer Puck from NIH and
the Genome Institute. And there is
something of a watershed in the presentation of babies with SCID now that we
are able to do prenatal diagnosis, or if there are patients with a positive
family history, so that you know right at birth that a baby is infected before
infections have set in and the complications have set in.
That
is a very different baby from the one who was unsuspected, who presents with
months of failure to thrive and infections and is already in a very tenuous
situation.
And
so those eight-, nine- and ten-month patients are really a different group from
that very young group who had to be picked up because of their genetics, not
their infections.
And
I think that the low-risk transplant could be applied to those very young
babies who aren't so ill, fortunately, because those may be the babies who you
would least like to do gene therapy on because of leukemia risk.
CHAIRMAN
SALOMON: David.
DR.
HARLAN: So I just want to strongly
endorse this no-alternative-therapy concept at the jurisdiction of the local
level, as you just proposed, with the final arbiter being, as it always is, the
court of public opinion.
If
somebody does something and the patient does poorly, and there was an
alternative therapy, we will all agree on it.
Because the last point that I want to make is that this same rule can
apply to gene therapy, as far as I am concerned, across the board. It doesn't have to be SCID at this
point. I think the same rule could
apply to retroviral gene therapy, regardless of the indication.
CHAIRMAN
SALOMON: Well, I mean, the concept is
there. Let's ripple out there in a
minute. I am still trying to get us to
a point where we could vote on something that we will try and craft in a
moment. Now, Jon, does this have to do
with getting us to the vote?
DR.
ALLAN: It is just that when you are
talking about alternative therapy, I am getting concerned. Because if a researcher goes and says, well,
gee, I can't find whatever, or there is some reason to push, if the agenda of
that researcher is to do gene therapy, then they are not going to be as
diligent about alternatives, because they are thinking about gene therapy. And so I am worried about that.
DR.
KURTZBERG: But the FDA could help with
that if they put together an informative document that says here is the state
of the art for this disease. Gene
therapy is one of the options, and here are the risks and benefits of this, as
well as the other therapies that you are considering for yourself or your child. So it would be a generic document that would
not have been prepared by the local investigator.
CHAIRMAN
SALOMON: So if you think about the
dynamics that have evolved here, it really is encapsulating the major
issues. The public comments and the
comments that followed point out that there are people dying who are grievously
ill, and who could potentially benefit from gene therapy, right? We all get it.
On
the other hand, one of our roles is to protect human subjects from therapies
that are insufficiently safe. And then
we have gone into all of these mitigating factors. How do you responsively respect the potential future and in this
case the tremendous benefit that these children got from their gene therapy,
and at the same time responsibly fulfill our role to protect subjects and
protect safety?
Now,
in this particular case, I am saying that we need about two more years before I
can say how safe this therapy is. And
until then, regardless of its incredible benefit which I acknowledge to everyone,
I am not comfortable supporting it any longer, unless there is no alternative.
So
could we vote on that? Okay. All of those in favor --
DR.
ALLAN: Can I just -- I'm sorry. That "alternative" still bothers
me, because the thing is that there are alternatives as far as I can tell with
these SCID patients. It may not be the
best alternative, but it sounds like there are alternatives.
CHAIRMAN
SALOMON: Well, I think we are giving a
pretty clear message, Jon, that any sponsor who wants to do these studies
better have a darn good line of reasoning for "no alternative" at
this point, and that that could change 18 to 36 months from now when hopefully
there are no more children with leukemia, and these two kids have had complete
remissions, and everything is good again.
That is all that I am saying.
DR.
KURTZBERG: I mean, you could follow the
pediatric oncology model right now and just say that kids will be eligible for
this if they failed or were ineligible for the other therapies that are available.
And
that way it could still be a salvage there therapy, and you could still learn
about it. The informed consent would
have to be incredibly clear, but it would be like Phase I studies in kids who
are dying of leukemia, where we say to the parents that we are testing a new
drug, we don't expect it to help your child, but we hope that it will help
other children. We're learning about
the safety of this drug.
CHAIRMAN
SALOMON: Can we get a vote on this
then? Is there anybody confused about
what we are voting on?
DR.
NOGUCHI: Please articulate exactly what
you are voting on.
CHAIRMAN
SALOMON: I knew you were going to say
that. Well, we don't -- I don't want to
go into motions and seconding and all of that.
We have never done that in the BRMAC.
But
the concept here is that for the moment, given the evidence, that gene therapy
trials in X-SCID children using the retroviral vector with the gamma-chain
transgene and X-SCIDs with the JAK-3 deficiency, and the IL-7 -- just SCID.
Okay. I want the ripple to go next to the ADA,
because there is a lot at stake here, and I am not sure the ADA is the same
game. That in that situation, until new
data is available in 18 to 36 months, that these are not going to be allowed in
children unless there is no alternative therapy available for those children
under these hematopoietic stem cells.
Is anyone opposed to that?
(No
response.)
CHAIRMAN
SALOMON: Does anyone want to abstain?
(No
response.)
CHAIRMAN
SALOMON: So then it is a unanimous vote
of the voting members, and then I don't have to count. Okay.
So the next issue, following this analogy, is -- I'm sorry, Phil?
DR.
NOGUCHI: I would like to thank the
committee for being very clear about this.
Just a comment about going beyond the X-SCID and the SCID with JAK-3 and
SCID IL-7.
I
do think that one needs to consider when we are talking about other models,
such as pediatric oncology, I would just say part of that is not similar
because here we have evidence from a different country of benefit. We have evidence from a different country of
adverse events.
Typically
in a pediatric oncology, you do not start with a presumption of
effectiveness. It is try this since you
have no other alternatives, but it probably won't work.
I
don't think that is really the same concept that we have for the X-SCID, but
when we get beyond X-SCID to the other small populations, then I think that
model is actually closer to what we are talking about.
But
for X-SCID it is a different kind of calculus that everybody has struggled with
and gone through.
DR.
KURTZBERG: I don't know about
that. Because it works, but it causes
an equally serious illness. That is not
a home run.
DR.
NOGUCHI: No, it is not a home run, but
in pediatric oncology if you are testing an experimental drug, you don't even
have that first assurance that in fact in some cases, in some clinical study
there is necessarily effectiveness. I
am just saying that it's a different perspective.
DR.
KURTZBERG: But you are not trying it in
frontline patients when you are at that level. You are trying it in patients
who failed the effective therapy.
DR.
NOGUCHI: And that is what we have
talked about for X-SCID, yes.
CHAIRMAN
SALOMON: So what I would like to do now
is see how far can the ripple go next.
I mean, the next group of trials is obviously there, as described by Dr.
Bordignon, but I know that there are at least two or three in the United
States, right, for ADA-SCIDs, and what do we think about that?
I
would start by saying that I think that is a very different group, and I am not
convinced by anything that I have heard that we should continue a hold on
ADA-SCID trials. But that is my
statement. Abbey.
MS.
MEYERS: ADA-SCID has an FDA-approved
drug on the market. It is an enzyme
replacement therapy. It seems to me
that all of the figures that I have seen say 80 to 90 percent of the children
do well.
And
it should only be, I think, the people or children who don't do well on that
FDA-approved drug who should be considered for this.
CHAIRMAN
SALOMON: So that is an important
statement. There is a drug available
for these children, and should that be considered in the trial designs. John.
DR.
COFFIN: To take the other extreme on
this, the only fundamental differences I see, if I got them right from what we
have been presented, is the dose that was given and the follow-up time.
Otherwise,
I have no good faith basis for thinking that there is any fundamental
biological difference in what is being done in ADA-SCID versus this that will
impact this kind of outcome in that disease.
We
have just basically an anecdote, that we have two patients here and none there,
but in my opinion that is only an anecdote at this point of the level of
evidence that we have.
CHAIRMAN
SALOMON: I think we should discuss that
because I think it is really different.
But let other people deal with it.
DR.
COFFIN: It is a matter of one's feeling
about the underlying biology, but I think it is only a feeling because we do
not know what the important biological parameters that underlie these events
are.
And
until we do, all we can offer I think is gut feelings regarding differences in
the diseases. I mean, I can understand
what the rationales are, but they are just rationales right now. There are no data that support them.
CHAIRMAN
SALOMON: I would like more discussion
on this, but again this is really important.
What we are dealing with now is how far our anxieties and uncertainties
now can drive regulation or inhibition of progress in trials to treat sick
people based on -- in other words, it is just as irrational for you to say,
well, I am concerned because of these X-SCID kids that it is going to happen to
these kids.
DR.
COFFIN: I would argue about levels of
irrationality, but if it is irrational, that is the level of rationality that
the FDA aspires to.
CHAIRMAN
SALOMON: Right. So let's see where that goes. Crystal.
DR.
MACKALL: Well, I mean, we didn't talk a
lot about it today, because I think that there were other more pressing issues,
but we had an extensive discussion at the last BRMAC meeting about the second
hit and then the potential critical role of the second hit being a gamma-c
signal, a growth signal.
And
certainly when you are looking at IL-15 transgenic animals or IL-7 transgenic
animals -- animals that have a constitutive on through the common gamma-chain
-- there is plenty of precedent that that is oncogenic in and of itself;
whereas, the ADA is simply a metabolic pathway. So at the scientific level, they seem like, really, apples and
oranges to me.
So
I think that there is a lot of rationale for believing, if you believe in a
second hit, that these are two different things.
CHAIRMAN
SALOMON: Rich, and then Mahendra, and
then Jon.
DR.
MULLIGAN: Yes. I agree with John Coffin on this point, but
I come to a different conclusion. That
is, I think it is a gut feeling. This
person just had a gut feeling, and maybe that is my gut feeling, too, that it
is different. But there are not sufficient
facts.
CHAIRMAN
SALOMON: Right.
DR.
MULLIGAN: And the fact that we have is
that there is not yet an ADA kid who has this, and when the first one gets
this, if someone gets this, then I am sure that we will be right back here
recounting the conversation.
But
I fall in differently, although I think that the reasoning is sound. I don't think that you can prevent these
things. I think that this is the way
that the course of clinical research has to actually move ahead.
CHAIRMAN
SALOMON: Mahendra.
DR.
RAO: I was just going to echo what you,
Dan, and Richard have said. Basically,
I don't think we have data on the ADA in sufficient numbers to be able to try
and make a judgment call either way.
And so we shouldn't until we have data.
DR.
KURTZBERG: I agree with that, but I
also want to say that ADA is a different disease, because these kids have the
potential for endogenous immune recovery with PEG-ADA or with gene therapy,
because it is a different kind of defect.
They
don't have a preemptive defect at the level of an immune cell, and that may be
enough of a safeguard to prevent this kind of event from transforming.
So
I think it is very different, and it should be approached very differently.
DR.
ALLAN: Okay. I don't know that we have any data that says that a transgene is
responsible for the leukemia or even a second hit. We don't have any information; it's a guess. It is.
It is a guess. It is probably a
pretty good damn guess, but it is still a guess.
And
for me, like Abbey was saying, you have got some treatment already, so it is
not a last-resort therapy. So if it was
your kid and your kid was on this pegylated-ADA and the kid was doing fairly
well, but you wanted to try something different because you didn't want this
kid to be on this thing, and you gave him the gene therapy, and the kid got
leukemia, that would be awful.
So
I am a little concerned when you say, well, wait until we get a leukemic
kid. If it was my kid, I don't want him
to come in here with leukemia.
CHAIRMAN
SALOMON: So you read the informed
consent, and you don't agree to your kid having the trial. But I think we have got to be careful here. The retroviral -- I mean, if you want to go
there, Jon, and you are welcome to do that here, then you get to the point
where you stop all retroviral gene therapy.
Because this is just going to reverberate out to any sort of integrating
gene therapy.
DR.
ALLAN: No. This is a hematopoietic stem cell in a SCID.
CHAIRMAN
SALOMON: Okay. Then you draw the line at hematopoietic stem
cells. Okay. Warren, and then David.
DR.
LEONARD: I was just going to say that I
am really not convinced that the transgene is having an effect, and I know that
we have no way of knowing definitively one way or the other.
But
the fact is that the gamma-chain, to the extent that we know, is constitutively
expressed, and there is no evidence of JAK-3 activation. I think that the IL-15 and IL-7, et cetera,
transgenes are different because then you are constituitively providing growth
factors that are normally not constitutively present.
And
without the constitutive presence of the growth factors, there is not
necessarily a reason to think that the receptors are going to respond when the
gamma-chain is presumably there anyway in the wild-type situation.
So
I am just throwing that out for food for thought, that I am not convinced that
the gamma-chain gene transduction is contributing. I don't want to rule out that it is not, because I can't know.
So
I think ADA deficiency is in fact quite different. Nevertheless, you know, there is a possibility of integration of
the ADA transgene, for example, in the LMO-2 locus or elsewhere. So I think that there is a finite
whatever-the-risk-is associated with that type of therapy as well.
CHAIRMAN
SALOMON: David, and then Barbara.
DR.
HARLAN: I am going to be a broken
record here, but I am going to fall in with Jonathan Allan, Abbey, and what
Warren just said. Because what we are
saying is whether or not we should let informed consent be the arbiter or
regulatory guidelines be the arbiter. And I think the latter should be on this
alternative therapy rule.
Because
if we see a -- number one, informed consent.
Patients, no matter what -- and our ethicists I think will back this
up. If it is allowed, there is an
implicit statement that doctors wouldn't even let me do this if they really
thought that it was dangerous, or they didn't have some pretty good idea. No matter how you word it, there is that
implicit communication.
So
if a kid does get leukemia, someone will say, What were you guys thinking? You knew that this was a risk, and you
allowed this to proceed when there was an alternative therapy.
It
seems to me that we have to do it only for those where there is no alternative
therapy.
CHAIRMAN
SALOMON: I have no problem with that,
and that is well said. Just as a point
of context though, that is what we said in October. One of the major messages we made in October was that the
risk/benefit analysis has to be in favor of the therapy.
So
what that means to me, Abbey, is that if you have a drug, in this case
pegylated ADA, that is part of your risk/benefit analysis. And, again, if a sponsor can make adequate
case that the risk/benefit analysis is such, then I think that works.
And
so I don't think that we need to reinvent risk/benefit analysis at this
point. I think that we affirmed that in
October, and that is one of the things that I think we did well. Claudio, do you have a comment?
DR.
BORDIGNON: Yes. I must apologize, because probably during my
rush in my presentation, I was not very clear about the data on the PEG-ADA.
I
think that everybody can assess this, but about 80 percent of the patients were
on PEG-ADA and alive, which means that the other ones were not.
Of those patients, the ones that failed PEG-ADA
and had to go to bone marrow transplantation, overall 73 percent are alive,
which means that the others are not.
Of
all the patients who went into gene therapy -- there are over 20, but I am not sure
about the numbers right now -- they are all alive. I cannot say that they are all well.
All
the patients that are in gene therapy without PEG-ADA are alive and well. I think that the numbers speak for
themselves. Of course they are not big
numbers, and of course the follow-up is not at the same level as the
gamma-chain. It is a different disease
and a different condition, and a different age.
But
how do I deal with parents asking me about the choice between the two
treatments, and having to say that a treatment with 30 percent risk of dying is
better than a treatment so far that has zero percent dying.
CHAIRMAN
SALOMON: So the question would be: Can we focus this discussion enough to now
vote on whether we would take a position as a committee on the trials on ADA?
And,
again, this is not an academic question here.
There are three trials. My
thinking here, my intuition is that there is two ADA trials and one other trial
that is not an ADA; is that right?
Because they were both put on hold the last time in October.
DR.
NOGUCHI: There is just one ADA
trial. But there is an ongoing study
that is not accruing patients.
CHAIRMAN
SALOMON: But my point is that it is not
academic, right? I mean, there are
people waiting to find out whether they can go forward with an ADA trial in the
U.S.?
DR.
NOGUCHI: That's correct.
CHAIRMAN
SALOMON: So I think that the community
has got to grapple with this one.
Whether we can successfully or not, we will figure out in a second.
But
I would like to propose that, for the moment, provided an appropriate
risk/benefit analysis -- a principle that was articulated in October -- and an
appropriate informed consent principle that was articulated in October, I don't
believe that there is enough data on the table right now that justifies this
committee stopping retroviral gene therapy for the other forms of SCIDs that we
have not already targeted.
And
I don't want to see that happen, and that is my personal opinion. Alison.
MS.
WOLFSON: I need to say something about
the appropriate risk/benefit analysis.
We just heard a risk/benefit analysis, and I asked David, because I am a
non-scientist, do the kids, the 20 percent who die, do they die from the
medication, or do they die because the medication has not worked and then the
disease kills them. And he said, the
latter.
Well,
that is a whole different way of looking at what a risk/benefit analysis
is. Here you have a drug and there is a
20 percent chance that you are going to die, and a hundred percent chance that
you won't if you do this. But that is
not really true.
CHAIRMAN
SALOMON: John.
DR.
COFFIN: I, too, hate to sound like a
broken record, but the only thing that gives me some optimism that we won't see
the same kind of adverse events in the ADA case is that the dose of cells is
smaller, and that really is the only thing that I think we could hang some
biological difference on.
And
I think somehow we should get that idea out there, that less can be more in
these cases.
CHAIRMAN
SALOMON: Butch.
DR.
TSIATIS: I have gotten very confused
with the numbers that are being thrown around.
I heard before that there is an FDA-approved therapy that has a 90
percent success rate.
And
then I hear that there is only a 70 percent success rate. Then I hear there is a hundred percent, with
very limited follow-up. So I am getting
very confused what is what.
Again,
I feel very uncomfortable given that we have a problem that children that are
eligible for an FDA-approved therapy that is beneficial, that they be eligible
for a trial that we know right now is a problem, at least for the time being.
CHAIRMAN
SALOMON: As long as, Butch, what you
are saying now -- it is fine to say it that way --but what you are saying then
is that any retroviral gene therapy or lentiviral gene therapy, for that
matter, in hematopoietic stem cell, you don't feel comfortable with right now.
DR.
TSIATIS: As long as there is no
alterative therapy.
DR.
ALLAN: So let me get this straight for
me. If the child can take pegylated
ADA, why not put him on pegylated ADA?
If he fails, then you are basically in that mode where there is no
alternative. And then you could have
gene therapy. So that is how I would
look at it.
CHAIRMAN
SALOMON: I think the important thing
here is -- well, sure, I agree. But the
point here is that I don't think that it is our job to design the trial. Our job is just to deal with the principle
that, under the right circumstances, it can go forward.
DR.
ALLAN: But it is the same principle
that we just did with the X-SCID kids.
So I am just saying that we are using the same principle, which is if
you have got an alternative therapy that works well, then the firstline should
not be gene therapy.
CHAIRMAN
SALOMON: And my point to David was,
Exactly. That's the risk/benefit
analysis, right? I mean, obviously
there are individuals that are not getting full benefit from replacement
therapy with pegylated ADA.
It
is extremely expensive, and it is in short supply. There have been different times that it has not been
available. It isn't perfect. It requires a constant, umbilical cord
attachment to medical care.
So
there is a lot of reasons that these sort of intermittent infusion replacement
therapies are not ideal. So it is okay
to see that they have got their good and bad points.
DR.
ALLAN: I just do not want to be
responsible if the kid is given gene therapy and isn't being offered -- or the
way it is being offered makes him jump for gene therapy, instead of PEG-ADA, and
he gets leukemia. I am going to feel
responsible for the fact that that kid got leukemia.
CHAIRMAN
SALOMON: Joanne and then Ken.
DR.
KURTZBERG: One thing in defense of gene
therapy for ADA that has not been said is that children on PEG have a selective
disadvantage to benefit from gene therapy because you take away the selective
advantage for the gene-altered cells to work.
So
it is actually a more complicated situation than we have been able to talk
about today. Because, although PEG does
have such efficacy, it has only had short-term observation, and it undermines
other types of therapy that might be based on selective advantage. So it is just something to put on the table.
CHAIRMAN
SALOMON: The field agrees that if you
are going to do this, you are going to have to remove the pegylated ADA to
allow selective advantage to work. Ken.
DR.
CORNETTA: Well, maybe just to remind
the committee, because I know you said three o'clock, but we have talked about
X-SCID for a long time, and there have not been any U.S. trials, I think, that
have entered any patients. This is a
still low number, and if you look at Carolyn's slide, the ones that we have not
talked about are really the largest number of studies, and we should make sure
that we discuss that.
But
I think to follow up, what probably what we are struggling again with is
something that we consider firstline therapy, or in the case where there is no
alternate therapy.
And
I still am not sure that there is a consensus here, but it seems to be that is
what we are trying to move towards.
DR.
MACKALL: We have not mentioned bone
marrow transplant for this either. We
have only talked about the PEG.
DR.
CORNETTA: Again, that is an alternate
therapy.
DR.
MACKALL: Exactly. Would we have to have worked through bone
marrow transplant? That is the
question.
CHAIRMAN
SALOMON: Okay. So I am sitting here, and what is going
through my head is that, for people who want to talk, there is 20 minutes left,
and if we don't push this to the next logical ripple, which is hematopoietic
stem cells or not, then we have not done our job today.
So
if you will forgive me, I am just going to temporarily push past this for a
second and not force a vote on this ADA thing yet, but hopefully we can come
back to it. I may be in la-la land now.
But
how far do you guys want to ripple this out?
Retroviral gene therapy for a hematopoietic stem cells is on the table,
and that is the next concentric circle that I see.
DR.
WILSON: And as Dr. Cornetta pointed
out, we currently have approximately 27 trials that are on hold using
hematopoietic stem cells, so that is an important issue that the committee
needs to discuss.
CHAIRMAN
SALOMON: So everybody keep their
comments real short here so that we can get everybody's comments, but just that
we get them.
MS.
MEYER: I just want to ask a question of
the FDA, which is that I think at the last meeting we asked that you have all
of the gene therapy scientists report to you on any clinical trials underway
and test the blood to see if there had been any of this insertion problem. What did you find?
More
than half of gene therapy is on cancer.
So if a patient died of cancer, nobody is even going to think about
this. Did you find any of this other
insertion problem in those?
DR.
RASK: Well, we have only gotten limited
data since that meeting in October. And
we were only asking them to monitor that periodically, but we have not obtained
any information of concern.
CHAIRMAN
SALOMON: Abbey, we are not going to get
this data. I mean, let's go on. With all due respect, you are not going to
get an answer to your question. It is
not anyone's fault. It is just that it
is really complicated to do those kinds of studies, and no one is doing them
yet. David.
DR.
HARLAN: So if we start from the point
of using this no-alternative-therapy standard, there must be hundreds of people
in this room who have arguments on why not to use that. I would like to hear what do we lose by
using that as the standard.
It
will continue because there are going to be patients for whom there is no
alternative therapy. I don't see what
we lose by adopting that safety standard.
CHAIRMAN
SALOMON: Be brief.
DR.
JUNGHANS: I think with oncology, you
have got a real problem because we always have another chemotherapy that we can
give. So there is alternative
therapies. There may not be alternative
curative therapies, but when you are giving PEG-ADA, you are not giving a
curative therapy either.
So I think you have to be careful how you phrase
that.
DR.
HARLAN: But I would say that
jurisdiction should be at the IRB level.
An IRB would recognize that an alternative anti-cancer agent is really
not an effective alternative therapy, and that we should leave that at the
local jurisdiction.
DR.
JUNGHANS: You have to be careful how
you phrase that because IRBs can be very nervous when they hear someone say,
"no alternative," and they hear "gene therapy" on the other
side. Believe me.
CHAIRMAN
SALOMON: Okay. Hematopoietic stem cells. John.
DR.
COFFIN: Again, I will express the
conservative position, which is that I don't see right now any evidence that
the same kind of event will not happen or should not be considered as a
significant risk with any hematopoietic stem cell therapies, so long as
adequate numbers of transduced cells are infused.
That
is not to say that in any given case it should not go forward, but in the
risk/benefit balance, I think this should be the risk. Clearly if somebody is going to be -- if we
are talking about terminal cancer patients, it is an insignificant risk.
But
this is what I think should be on a risk side of a risk equation like that.
CHAIRMAN
SALOMON: Okay. Rich.
DR.
MULLIGAN: I always go after John and
say that I agree, but I still draw the opposite conclusion. So I think that is true that these other
things are hunches. I say that ADA is
no different than any other stem cell, and certainly there is some reason to
think that insertions will cause difficulties.
Nevertheless,
I still harp on the lack of any data suggesting in patients that bad things
will happen in other diseases. There is
no direct evidence. And I just happen
to think that is the way that one ought to look at this.
CHAIRMAN
SALOMON: I would reiterate that. I mean, what we are faced with, factually,
is two tragic complications in an otherwise successful gene therapy trial in a
disease called X-SCID.
And
that really to me is no different than a leukemia trial that someone got then
lymphoma 12 years later or something.
And we have got to be really careful that we suddenly abandon all
existing principles of informed consent, and risk/benefit analysis because
theoretically -- which we have known all along, John -- a retroviral vector
with an integration -- I mean, I know that I don't need to tell you of all
people. Ken.
DR.
CORNETTA: I think the risk is
significant. I don't know how frequent
it is, and that's what we are, again, still struggling with. I do think that for Phase I that these
studies are generally done in populations where there is either no alternative
therapy or no therapy at all.
I
think the one thing that we can, again, try to advise the FDA, which they
probably thought of already, is that as they look at the process of going from
Phase I to Phase II to Phase III agents, there is more characterization and
validation of that process.
But,
in addition, to make sure that they are telling the investigators that they now
need to be thinking about their vector construct, what is the enhancer there,
and all the things that we have talked about today so that the FDA is also
communicating that to investigators, that as they are moving beyond Phase I
they need to be considering this in the development of their product.
CHAIRMAN
SALOMON: Present and future. Cindy.
DR.
DUNBAR: Well, I do think that we do
have some data from the large animals.
I mean, those animals' median cell dose was 65 million. That is not that far. There are 46 animals with, if you add up the
follow-up years, 250 follow-up years, and I calculated it to be like 5,000
insertions that we know about so far. I
mean, they have not all been sequenced obviously.
I
believe that there is something unique about the selective expansion of the
cells, potentially the transgene may be
less likely. I think it's the age. I mean, I don't think we know yet.
But
when you say "no alternative therapy," there is no way that you can
even think of developing HIV -- many genetic diseases, like CJD, thalassemia,
sickle cell, et cetera, where there are certainly alternative therapies, but
they are just not necessarily very good ones.
And
I don't think that the risk in the other group -- I think we have data that
would suggest that we are not going to suddenly see 20 leukemias with a
neovector or a globin vector. We don't
know.
But
we do have a lot of experience, and I think we need to figure out what it is
about the bone marrow or the transgene in that particular clinical situation
that may have led to second hits.
CHAIRMAN
SALOMON: David. And, again, let's keep it very brief because
I want to get to a vote in a minute.
DR.
HARLAN: So I don't think that anybody
said, "no alternative therapy."
The words that people have used are "failure" or "no
effective alternative therapy."
And the second point is imagine a situation where a treatment was
available for Disease A, and two of eleven of those patients got a serious
complication.
And
then we are asking about using that same therapy for Disease B, and saying
because there is no proof that it causes that complication, we should let it
proceed. That is not where the safety
equation falls for me.
It
seems to me we should say its absence of proof does not mean proof of
absence.
CHAIRMAN
SALOMON: Kathy and then Bruce.
DR.
HIGH: Okay. I just want to point out that they are not the equivalent
therapy. When the transgene is
different, the therapy is different.
And to me, I think it is being too liberal, not too conservative, but
too liberal to take adverse event data from one trial and extrapolate it to
everything that uses the same vector and the same target cell.
Because
if the transgene is different, then the therapy is different.
CHAIRMAN
SALOMON: Well, the transgene is
different, but the disease is different, the ages are different, the
co-existing comorbidities are different.
So that is the issue.
DR.
RAO: That is like taking one
chemotherapy drug and saying it is like another chemotherapy drug and we can
generalize across all of them. I mean,
we don't do it, so we shouldn't do it because it is a gene therapy.
CHAIRMAN
SALOMON: Okay. Bruce.
Again, be brief.
DR.
TORBETT: I tend to agree with the
analogy to cancer. I think we are
trying to lump everything together and draw large conclusions based on very
little data at all, and I guess I would err on the side -- and perhaps in six
months I hopefully won't be back here-- err on the side of being more cautious,
and trying to keep the bar at a reasonable level to proceed in this area, and
not kill it off completely.
So
I guess I would agree with what Kathy was saying, that I think that without any
data -- and there has been history with Cindy Dunbar's work and others, that it
has been fairly safe so far. And I use
"fairly."
CHAIRMAN
SALOMON: Ken and then Barbara.
DR.
CORNETTA: Well, I guess to put it in an
analogy that we are getting used to, I think with the X-linked SCID that we are
sort of at Code Red or whatever, Yellow, and I think --
CHAIRMAN
SALOMON: That is worse than my ripple
metaphor.
DR.
CORNETTA: But in a sense I think that
there are so many different diseases that we are talking about -- it's oncology
patients, it's HIV patients -- that it is going to be very hard for us to get a
consensus on what the risk is for each of those.
But
in a sense I think what direction we can give the FDA is that we are not
considering the risk that we see with the X-linked SCID to be the same risk
currently with these other trials.
There
is certainly room for concern. We are
not down to Code White or whatever, but we are probably somewhere in the
middle. But I think the recommendation
that we can give currently is that there is enough difference to say that these
are not equivalent risks.
CHAIRMAN
SALOMON: Barbara.
MS.
BALLARD: Another thing that I was going
to say is that I think we are kind of working semantics of language here in the
difference between whether there is a failure of standard treatment versus no
optional treatment, or alternative therapies.
Do
we want to specifically say that there has to be no alternative therapy? And I don't think that is what anybody is
trying to do. So I think the language
that we are using is a little bit of a misnomer.
We
need to present it to the FDA in a way where if there has been a failure of
standard therapy, then a risk/benefit analysis needs to be done on a
case-by-case basis.
CHAIRMAN
SALOMON: I would even go a little
further and say that as far as I am concerned, when you get out to just all
retroviral gene therapies and hematopoietic stem cells, as long as the informed
consent is unequivocally clear about what has happened, I would not touch those
trials at all.
And
I would not try and craft language today to change them. I am very comfortable with those
trials. I don't think anything that we
have heard today changes those trials.
I
know that everybody does not agree with that, but I am just saying that I don't
think we have to get hung up right now on that language. I thought that was important for the X-SCID
statements and your points are well taken on that. But I don't think that is important now.
DR.
NOGUCHI: To try to cut to the chase
here, I will say that the FDA already has a policy for the 27 trials outside
the SCID, and X-SCID, and ADA- SCID, and that would be on a case-by-case basis. We will have and have entertained on a
case-by-case basis taking people off, given all the caveats that we have from
the October 10 meeting.
What
we are simply asking here in the sense of that larger scale is: What is the sense of the committee regarding
risk? And we have already made a
determination that we are prepared to move forward in specific cases where
there are no alternative therapies or where the therapies are inadequate.
CHAIRMAN
SALOMON: I would like to, just for
times sake here, we have got two important questions that we need to vote
on. I think we have articulated all the
sides, and we don't all have to agree.
AUDIENCE
MEMBER: Can I say one thing about the
patient side?
CHAIRMAN
SALOMON: If it is really quick.
AUDIENCE
MEMBER: I just think that you are in a unique position here, where everyone has
been saying that informed consent is for desperate parents, and therefore it is
like less legitimate.
Well,
now you have a perfect opportunity where informed consent is not a desperate
situation. It can be used as a
situation to really empower the patients or the parents to make a more informed
balanced decision.
So
you have an opportunity here to make informed consent part of it, and I think
that is powerful.
CHAIRMAN
SALOMON: I think we all agree, and I
think this informed consent issue is really good. I just think that -- everybody is always ready to beat us up with
this informed consent when it suits them, and then they are always ready, like
you, to tell us, oh, you know, informed consent is such a great tool.
We
are not trying to get rid of informed consent.
But I think you have got to realize that this has been used against us
and used with us, and it is not as clear to me. We really think we can do better informed consent, and we are
really trying our best to do it. I
guess that is what I am trying to say.
So
can we have a vote now on should we advise the FDA that there should be a hold
on retroviral gene therapy trials continued that use retroviral vectors for
hematopoietic stem cells.
DR.
ALLAN: Dan, that is not what he is
saying.
CHAIRMAN
SALOMON: That is the vote that I want
to hear though. What is different?
DR.
ALLAN: This is on a case-by-case basis
when there are not other therapies, either no alternative therapies or what was
the other?
DR.
CORNETTA: Inadequate. I mean, it is the responsibility of the
sponsor to really justify to us why this should proceed.
DR.
ALLAN: So it is not a question of
putting a hold on all therapies because that is not what is going on, right?
CHAIRMAN
SALOMON: Right now they are all on
hold, Jon. So I am asking the committee
whether they can vote to take the trials off hold. That's all I am trying to get at. I am not trying to stipulate what the basis of the off-hold is,
just that we would advise the FDA that they can now review the 27 trials on a
case-by-case basis to take them off the hold
Or
do we want to go with the opposite feeling that I think John has articulated
very clearly, that this is a risk of this class of vectors, and it is not
acceptable, and they should all stay on hold.
DR.
COFFIN: That wasn't exactly it.
CHAIRMAN
SALOMON: I was just taking your
articulated ideas as the other thesis.
So can we vote? How many would
agree to advise the FDA to go back and take a reevaluation of all 27 cases on a
case-by-case basis because we feel that they don't have to be on hold any
longer just based on the fact that that they are using retroviral vectors and
hematopoietic stem cells? How many
would agree to that?
DR.
HARLAN: I will agree to that, but that
is where I thought you said you were right now.,
CHAIRMAN
SALOMON: No, it's not. Everything is on hold right now.
DR.
HARLAN: The FDA doesn't even have the
prerogative to release them?
CHAIRMAN
SALOMON: Well, the FDA can, but we are
trying to advise the FDA. They want to
know our advice on this.
DR.
NOGUCHI: We are, on a case-by-case
basis, entertaining proposals from sponsors where they can demonstrate to us
satisfactorily that there is no adequate therapy or inadequate therapy for
life- threatening diseases.
And
we have implemented for those conditions the advice of October 10, and that has
been updated with the evidence of the new adverse event. In that sense, I think this vote would be
saying in general, given -- rather than wait for people to come to us, we
should actively work with sponsors on this.
It
is sort of, where is the burden placed to take people now off clinical hold in
this subset.
CHAIRMAN
SALOMON: How many vote aye? I am trying to articulate what Phil
said. Basically, can we advise the FDA
that it is time for them to remove the blanket hold on all retroviral gene
therapy trials in hematopoietic stem cells and review them case by case, and
where appropriate risk/benefit is there, and where appropriate consent form
documents are given, and where there is an appropriate balance in this concept
of risk/benefit of alternative therapies that have been considered, that they can
take them off hold and let them go forward.
DR.
TSIATIS: Just a point of
clarification. How is this different
from our motion with the SCID?
CHAIRMAN
SALOMON: It's not. We are just following the ripples, Butch,
because there are now 27 trials waiting to hear what we have to say.
DR.
MACKALL: With the SCID, we said that
this shouldn't happen.
DR.
ALLAN: To me, it is just wording
because it sounds to me like you are saying that we are going to take
everything off hold, and it sounds like we are giving the green light to go
forward with all these trials, and that is not what you are saying.
CHAIRMAN
SALOMON: No. I am definitely not saying that.
I am trying to capture what the committee was saying, which is that we
have concerns about consent forms, and we have concerns about risk/ benefit,
and we have concerns about a careful consideration of alternative therapies.
So
I am trying to say that given that you don't want to review all 27 trials
before they can go forward, we ought to advise, if you can get yourself to that
point, the FDA that they should do it.
DR.
COFFIN: Dan, I would support this if
the FDA at the same time when they went back over these asked the sponsors to
give an incisive analysis as to whether or not these events -- what the
probability, based on what they can tell now, of these kinds of events
occurring in their trial is.
CHAIRMAN
SALOMON: Can we vote first, and I will
come back to you. But can we just vote
on what I said first? So how many
people vote aye?
(Vote
taken.)
CHAIRMAN
SALOMON: It is not unanimous. How many people vote nay?
MS.
DAPOLITO: Dr. Salomon, can we take a
poll by individual?
CHAIRMAN
SALOMON: Well, I thought the nays would
be easy.
MS.
DAPOLITO: But we are required to have
on record your vote.
CHAIRMAN
SALOMON: Okay.
(Vote
off microphone.)
DR.
HARLAN: If I understand it, aye.
DR.
HIGH: Aye.
DR.
FRENCH: Aye.
DR.
CORNETTA: Aye.
DR.
WOLFF: Aye.
DR.
TORBETT: Aye.
MS.
MEYERS: Aye.
CHAIRMAN
SALOMON: And Barbara. Thank you, guys. Now, if I can just back you up.
How about ADA-SCIDs? One way we
could deal with this is to say we just dealt with it. I am happy with that. I
like it. Now, the last thing here would
be that John suggested is there something else that the committee would
feel.
Now,
I have to say to you that with the world looking at us like, Did you do the
right thing in October and did you do the right thing in February, I personally
would like to see at a website somewhere at some point in the near future where
I could tell people go to the website and all 27 trials have a couple of
paragraphs about how they dealt with these issues.
I
feel like all of us feel a lot of responsibility, and I feel like we have done
a really hard job here for you to give you support, and that gives us as a
whole field an integrated answer to a tough issue.
You
know, sick and dying patients and safety issues and trials gone array and the
whole thing. But I sure as heck would
like to be able to point people who start hassling me six months from now to
just go to such-and-such a website and see what we really did.
DR.
NOGUCHI: I think we would take that
under advisement and strive to do that.
As you know, though, each case is individual and we may not be able to
necessarily make public each response.
We
may be able to in a better sense be able to give you both the general feeling,
as well as some of the outliers. I just
think that on a case by case basis we would be not in a good position at FDA to
completely specify all the responses.
But
the point is absolutely well taken, and part of the discussion and part of the
minutes for this particular meeting will be reflecting these concerns.
CHAIRMAN
SALOMON: I guess to be really specific,
what I am saying and the committee can agree and support it or not, but I guess
the message that I am giving you after this experience of doing this thing in
October and being back here in February to do it, and then listening to Bruce
say, gee, I wonder what I am going to say six months from now, and I think we
heard that from Kathy and from others as well, is -- I mean, we need or you
need to do this.
I
mean, you guys really need to go through all of these cases, and it had better
be clean if we are back here again in September.
DR.
MULLIGAN: I want to emphasize that all
the things that we didn't get to, like the cell dose, and actually implementing
that. I think it is very, very
important that our concerns are really emphasized, in terms of we think that --
I certainly think that things like suicide vectors, insulator vectors, all
those things are incredibly important.
And
it is not that we don't think that they are important. And it would be fantastic if, although we
have not implemented any of these issues, people got the message that we do
think -- many of us think the cell dose is key.
That
the number of integration sites is key, and it would be wonderful if new
clinical trials were --
CHAIRMAN
SALOMON: I didn't shut you off. Ken.
I would just say that Ken sort of captured that, you know, sort of
present and future. But, Ken,
your comment.
DR.
CORNETTA: Another comment, and maybe
I'm sorry that I am sitting so close to the FDA folks here. One of the things in line with this is the
clonality that has been asked for by investigators. And to be able to analyze what that data is, there is going to
have to be some consistency in what that analysis is going to be.
And
I would ask the committee to maybe -- if they agree with me -- to sort of make
the recommendation that at least some type of paper or guidance comes out on
what that analysis -- you know, what are the expectations and sensitivity, or
is there some common or agreed-upon assays that would be done.
But
really some specific guidance for investigators because I think that's going to
be key to collecting that data and having compliance.
CHAIRMAN
SALOMON: And I would just point out
that we made a decision two hours ago to go a
little different direction, and to the FDA's credit, those very specific
kinds of questions were spelled out in their questions.
So
we didn't get to those, but I think that everyone can agree that those are the
next big steps, and there may be another BRMAC meeting that needs to happen in
6 to 12 months to do that. Bruce.
DR.
TORBETT: I think, with the whole world
watching on this decisions, I think that some type of website or some type of
information and profile similar to what Rich and Ken said is needed, and I
think that it needs to be updated, because if this is a recurring theme, I
think the public needs to know what is going on, and I think it is imperative
for the committee to decide something along these lines.
CHAIRMAN
SALOMON: Abbey and then Linda.
DR.
WOLFF: I just want to say that if there
are animal studies going on right now, preclinical studies, that those animals
should be kept longer if possible.
CHAIRMAN
SALOMON: Write your Congressman,
Kathy.
MS.
MEYERS: On the informed consent
argument thing, I want to agree with what somebody said before that there
should be some piece of paper written by the FDA that is required to be
attached to the informed consent document so that every patient, no matter
where they are in the country, who is considering gene therapy, would have,
like, a patient package insert.
CHAIRMAN
SALOMON: Abbey, in fact, if you go back
to the website around October, we specifically said there should be standard
language drafted by the FDA for the informed consent, and indeed they did that,
and that was what they were reading from for all retroviral gene therapy
trials. Tom.
DR.
MURRAY: Also on informed consent, which
is going to be made to bear an enormous amount of moral weight in these trials,
there is a growing and significant body of empirical information about when
informed consent -- how and when informed consent can be made meaningful and
not merely a pro forma exercise.
And
everything from the cognitive errors that people commonly make in judging
risks, including ways of presenting information, not just -- I guess I was
getting distressed by this notion that somehow we are going to have a magic
paragraph that is going to solve all of our problems. That is not the way it is going to work.
And,
in fact, I think I would recommend to the FDA that it recommend to any group
that wishes to do these trials that they should familiarity with this empirical
literature about informed consent, and that in fact it is in conformance with
best practices of informed consent.
CHAIRMAN
SALOMON: Well, I don't know about your
institution, but every year I have to recertify the fact that I am exhaustively
aware of everything that happened in the last 12 months, and that is the point
there. David, a last comment.
DR.
HARLAN: So if I understood what I just
voted for, it was to move the onus of responsibility from the IRBs to the FDA,
and then you -- well, sort of, but -- well, no?
CHAIRMAN
SALOMON: Remember these programs are on
IND, these programs are now on hold. We
are telling the FDA to go back, review them, and let them go. The IRBs can make their own decisions after
that.
DR.
HARLAN: Right. Yes, that is what I meant to say. And then you had asked could we have on a
website some short paragraph from each center and Dr. Noguchi's response was
maybe yes and maybe no. I would just
say for those instances, where there isn't explicit wording as to that
analysis, that some generic wording to that effect be placed on the
website. That is my only suggestion.
CHAIRMAN
SALOMON: Well, again, I think that the
best thing the FDA does now is publicly demonstrate that these 27 trials, and
any other trial after that, address the principles that we have articulated for
you in October and February.
I
mean, I think that is really important, because the public is going to come to
it and the public is going to demand it, particular if the you-know-what hits
the fan in another six months from now.
DR.
NOGUCHI: Obviously, we will work to
implement all the advice. We may be
getting back to the committee for help on some of the details, but we greatly
appreciate all the advice that is being given and continues to be given.
This
is a difficult area and I thank the committee in its entirety, and including
the public here, for helping us move through these very difficult issues.
CHAIRMAN
SALOMON: So with that, I am closing
this meeting, the last of my chairmanship of the BRMAC, and to tell you just --
(Applause.)
CHAIRMAN
SALOMON: And in keeping with my idea of
staying brief, it has been an extraordinary experience with extraordinary
people. Thank you.
(Whereupon,
the Advisory Committee meeting was concluded at 3:08 p.m.)