|William A. Hinton State Laboratorie|
In light of the potential of antibodies as therapeutics and prevention for HIV infection, the MA Department of Public Health and Search For A Cure invited an expert panel to identify barriers to monoclonal antibody development and the best course of action to see them make a difference in the cause of ending the epidemic.
Three antibodies were presented formally: Ibalizumab, an anti-CD4 monoclonal antibody; PRO140, an anti-CCR5 monoclonal antibody; and Cytolin, an anti-CD11a monoclonal antibody. The details of each are discussed in the transcript below.
Many potential advantages and drawbacks compared with modern antiretroviral therapies were identified, including once a week or potentially once a month dosing as opposed to the daily dosing requirement of existing drug regimens, lessened side effects, and potentially reduced emergence of resistance.
Dr. Daniel Kuritzkes, a representative of the ACTG, indicated support for the development of a monoclonal antibody, but warned against pursuing the wrong one. He pointed out that the wrong antibody could lead to practical clinical failure, not because of an inability to treat HIV infection but because of an inability to gain viable sales in the marketplace against competing, cheaper ARV regimens. He reminded the group that some antiretrovirals are nearing the end of their patent life and generic forms may reduce their cost, making the probably more expensive antibodies less desirable. Dr. Edmund Tramont favored clinically testing an antibody therapy to achieve FDA approval as soon as possible; positing that the achievement of one antibody would create a tipping point in their development and lead to the next generation of monoclonals for HIV treatment.
The group reached consensus that antibodies represent a very intriguing field of study and do have potential to make a real impact, particularly in the arena of prevention. If in fact antibodies are developed to be used once a month and possibly in combination as a cocktail of antibodies to reduce (the likelihood of resistance), then they could be a valuable tool for transmission prevention. However, determining clinical efficacy may present a serious challenge given the plethora of antiviral cocktails; a clinical trial would have to be constructed which simultaneously showed the efficacy of the antibody while allowing patients enrolled to be taking ARVs. As Dr. DeMaria pointed out, “it is not 1994 anymore,” meaning there are less people whose virus is not already being controlled by ART, making it difficult to find a population of patients to treat with antibodies in a clinical trial. The group affirmed that having a cohort for whom antibody treatment would be valuable is necessary to show efficacy.
The best method to approach further development in the field may be to first show an antibody works in combination with antiretrovirals allowing for reduction of elements ARV therapy due to efficacy of the antibodies. An alternative might be to demonstrate that an ARV cocktail+Antibody can reduce viral load below that achieved by patients whose RNA levels are >50 RNA copies. This could lead to expanded trials with treatment interruption to determine if the antibodies can suppress viremia in that context. There is also an opportunity to determine if treating the patients not achieving suppression with antibody can lead to suppression in patients having difficulty adhering to existing regimens. Any of these efforts would lead to testing monoclonals independently of other ARV’s. The most viable choice for this type of demonstration may be PRO140, which has already shown promising Phase II results controlling virus. Dr. Olson representing PRO140, indicated Progenics Pharmaceuticals has shifted their focus from virology to oncology and that they are interested in selling or licensing out their product, PRO140, to the right group to see it developed further. Search For A Cure supports achieving a Phase III trial through some mechanism and will continue to pursue assisting in making that happen.
In summary, experts agree that monoclonal antibodies represent a valuable opportunity for both pre and post exposure prevention and potentially in disease progression, including the context of maintaining prolonged treatment interruption, for salvage therapy, and as a component to existing ARVs to further reduce viral load and protect against ARV resistance development.
A successful antibody or antibody cocktail delivered infrequently, once a week or once a month, would be of enormous benefit to two particular groups. Persons living in resource limited settings, for whom daily dosing has been demonstrated as a clear impediment to the success of ARV programs, and secondly in the case of those who have difficulty in maintaining an effective dosing schedule. Dr. Valentine was especially concerned to find a successful way to treat drug addicts who have HIV infection.
With a long half-life, excellent tolerability, and the possibility to evade resistance Search For A Cure will continue to pursue the development of this field of therapy and report the progress to the community.
Search For A Cure
DS: First thank you all for being here I want to introduce the person who can explain to you why we are all here and can explain the outcomes we want to get from this meeting, the reason I am beginning this way is because someone asked me earlier what is the point of the meeting and I decided the best thing to do was to pass the buck to Dr. Alfred DeMaria who is going to give a formal introduction.
AD: I am Al DeMaria, medical director for infectious disease here at the Department of Public Health and the State Epidemiologist, Welcome to the William A. Hinton State Laboratory!
I think this meeting is very appropriate for this site because the state laboratory has been, in some way, here since 1894 when Theobald Smith decided to make diphtheria antitoxin. It didn’t make sense to have a horse out here in Jamaica Plain and a laboratory downtown at the State House, so he moved the laboratory to the horse instead of the horse to the laboratory. This facility was actually the Bussey Institute, which was officially the Harvard Agricultural School.
So as things evolved and state health departments realized that commercial smallpox products had certain deficiencies (like giving people bacterial infections and tetanus, etc.) they decided to get into the business of vaccine manufacturing themselves. In 1904 after the Boston smallpox epidemic of ‘02 ’03, it seemed logical to build the biologic laboratories here with the diphtheria antitoxin facility. Then during WWII, Edward Cohn the inventor of plasma fractionation needed a place to manufacture plasma products and the facility was built here at the Massachusetts Biologic Laboratories.
|Dr. Alfred DeMaria, State Epidemiologist|
So it was created for diphtheria antitoxin, then smallpox vaccine, and then plasma fractionation, and one of the side products of plasma fractionation to make albumin was immunoglobulin. After the war the Biologic Laboratories became an immunoglobulin production facility and for many years the Department of Public
Health had all of the immunoglobulin it wanted or needed for outbreak control for hepatitis A and measles. During the 50’s and 60’s they began to get into immunoglobulin specialty products and those specialty products included anti-RH Immunglobulin, varicella zoster immune globulin, CMV immunoglobulin, and RSV immunoglobulin. About five years ago they went out of the immunoglobulin fractionation business and built a monoclonal antibody production facility over in Mattapan, where the now UMass Biologic Laboratories is located. So, it seems like an appropriate place to have a meeting about monoclonal antibodies and the promise of monoclonal antibodies for HIV infection, and our collaboration with Search For A Cure goes way back. Perhaps we should go around and introduce ourselves.
(Introductions around the table)
DS: And back to the beginning. It makes sense to ask why we are together and it is intended to be an informal session, nevertheless however informal anything is, I think it is often wise to begin by some brief remarks, and as a consequence, we have set aside three brief presentations of the only three monoclonal antibodies which at the moment we have been able to notice via internet and through discussions with other community activist. There are being talked about in the context of HIV therapies of one type or another and particularly as a potential prophylactic and I want to share with you Search For A Cure’s reasons for interest.
1987, (many of the people in this room I want to thank because many of you were around back then and now still are), was a time when my life was spent going to funerals on the weekends. It was 9 years before the discovery that cocktails of antivirals would slow down HIV progression and a time that most of the younger folks just don’t remember but we do. One of the things that we remember, Dr. DeMaria would remember was we had a team called the Smart Team, that Dr. Mayer sitting here was on it as well as others when we started Search For A Cure in 1987, and one of the first things we talked about was using a “Bomb”. Fred Mendel was part of that discussion, Peter Medoff; they have both passed away as a result of HIV. That was the idea of using the drugs available at the time all at the same time trying to block the virus. It turns out that we weren’t that far off from accurately predicting what would happen next. In 1996, we had been in secret meetings with Gilead screaming bloody blue murder that their product Adefovir was never going to pass FDA testing, but their PMPA, which we now call Tenofovir, looked really promising as a prophylactic agent. We were convinced, as was Martin Delany and some others, that they should move forward and it took them four extra years because of their insistence of holding onto Adefevir to get going on Tenofovir and another eight years before it was used in an international trial to show that it had potential as a post exposure prophylactic medication.
|David Scondras, Search For A Cure|
This poster is from 2007, five years ago and it spells out a meeting held right here asking for and saying very publicly that we can use these drugs as pre and post exposure prophylaxis and as ways of putting an end to the epidemic. We said it was time to put an end to this epidemic, we had the tools and low and behold five years later it is in fact national policy that yes in fact we do have ways to put an end to the epidemic. We called it highly active prevention and we still have a lot of interest in it.
We went on to ask the state legislature to pass a piece of legislation that would make it possible for Massachusetts to have, in an organized fashion, a way to construct public policy, reconstruct legislation and look carefully at the potential for how to put an end to transmission using the existing tools. I’d like to read you a letter that we got on September 20th from Rep. Carl Sciortino, “I’m delighted to share with you some good news, we just approved the HIV commission bill out of the Committee on Public Health. This bill is passing rapidly, the Speaker of the House has already said it will pass, and we look forward to seeing it pass the Senate, and the Governor signing it.”
Having said, that it should come as no surprise that when we discovered that there was an entire potential line of medications that has gone as yet unexplored, that we of course as non-scientists don’t know much about, but never the less look promising. We wanted to pull together the best people that we knew and you are they to have a beginning open discussion about the potential use of monoclonal antibodies both in certain therapeutic settings but also in connection with a way of developing another tool for HIV Prevention, preventing transmission.
Let me share with you the communities’ view of a monoclonal antibody, number one it’s once a week, once every two weeks, or once a month. Trust me that is a huge difference in terms of compliance, in terms of failures, in terms of being able to afford, it in terms of making it internationally a realistic possibility, etc...Number two, it looks like it is difficult to get viral resistance to it, it would be something new certainly, and in that sense from the point of view of a person who needs salvage it would be very important. It could potentially be used as an add on to protect existing cocktails which don’t seem to always lead to enduring suppression, perhaps precisely because people don’t take them all on time, who knows. But having said all that, we also noticed that there was no institute of science for antibodies and that there were a considerable number of obstacles, both because of the stage of development of existing antivirals but also because of the fact that there isn’t a loud voice speaking out saying hey lets move on with this.
David Scondras, Search For A Cure
We were skeptical frankly, as a community, as to how rapidly a vaccine would be available and the existing panoply of antiretroviral possibilities all appear to us to have the shortcomings I mentioned earlier, such as difficulty with compliance more than anything. As a consequence anything that could be done to expedite focus, identify obstacles, suggest solutions to the development of monoclonal antibodies as therapeutics and as a potential way to be used as prophylaxis would be an extraordinarily important thing and we think the next obvious step in the sequence of steps that began with not knowing what to do, in fact I think testing nutmeg was one of the things that was tried out in the early 80’s leading to where we are now.
I wanted to thank you very much for coming. Dan Kuritzkes has offered to share a few of his experiences with David Ho’s product for us; you will see it here on the agenda as the first one. Second, William Olson is on the phone and is actually the Senior Vice President of Progenics Inc. and the person responsible for the antibody called PRO140, and Richard Trauger is here. Dr. Trauger is developing an antibody called Cytolin which was I think originally developed at the Dana Farber for other reasons all-together. Having said that, we listed five questions that we wanted to get some answers to today, if there are answers to them. To make it clear to all of us, that yes we do have very specific questions and would appreciate very specific answers to them. Having said that I would like to begin by introducing Dr. Dan Kuritzkes who is going to speak a little bit about his experiences with Ibalizumab. Number 1.
Presentation 1: Ibalizumab
Presented by Dr. Daniel Kuritzkes
|Dr. Daniel Kuritzkes,
Harvard Medical School
DK: Thanks David, it’s nice to be here. It is likely that my only qualification for being here tonight is that the name of the drug is e-bail-e-zoo-mab (laughter). Let me also say before I begin that I was involved, starting when I was still in Colorado and for a couple of years when I came back here to Boston with the Phase I studies of Ibalizumab, but have not been involved with them since, and although I once consulted for Tannox, I haven’t had any involvement with Timed so I have neither a conflict of interest here nor much relevant recent experience. So I will give a talk mostly about what is known and has been published or presented at conference.
My talk is going to be in two parts, the first part will be about Ibalizumab itself, what are the data and what we learned in the original clinical trials, and then the second part will be what are the challenges in studying monoclonal antibodies in the therapeutic setting, and my comments, to put it in perspective, will be on the use of monoclonals in therapeutics not so much about their use in prevention which I think raises a whole separate set of questions though somewhat related.
So Ibalizumab is a humanized murine monoclonal that was once known as 5A8 it’s an IgG subtype 4 antibody that recognizes the second domain of CD4 and as a result it is able to bind CD4 without inhibiting the ability of CD4 to mediate proliferative responses of CD4+ T Cells. In vitro studies looking at antigen specific proliferation as well as molecular mediated proliferation, found that there is no inhibition of recall responses and so forth. Although it is often called an attachment inhibitor, it is not an attachment inhibitor. It blocks virus entry at a post CD4 binding phase, and although I will show you some structural data, it is still not understood precisely how this antibody blocks because it allows the virus to attached to CD4 and then blocks the next step of interaction with the chemokine receptor but without being itself a chemokine antagonist.
So these are data published last year by a group collaborating with David Ho showing the binding of Ibalizumab to CD4.
You see here the first and second domains and the part that interacts with GP120 and the part that interacts with antigen presenting cells is really located on this side so there is no interference sterically by the antibody.
So the first study that was done which I helped the Tannox people design was a simple single dose escalation study where one infusion of antibody was administered to patients.
These were all people not on other antiretroviral therapy who were viremic and had CD4 counts that were above 200 or 300, and what you can see is there was actually a fairly prompt and reasonably dramatic reduction in plasma viremia and that the 10mg/kg dose nearly a 1.5 log reduction over the course of 14 days and at the higher, 25mg/kg dose about a 1 log reduction, so between a 1-1.5 log maximum reduction and then the lower doses didn’t really do very much but the antibody was well tolerated.
If you looked at what happened to the CD4 response, within the first 24 hours there was a 100 to 200 cell increase in CD4’s and then that response waned over time.
They then went on to do a multidose study, with three different doses, with or without a loading dose.
You see once again achieved a 1.5 log reduction that was really quite prompt, but then gradually that activity was lost and if you look at the CD4 counts there is again a very rapid increase in CD4 counts and then there is some see-sawing that occurs in the CD4 count.
So based on these data a Phase II study was conducted in patients who were failing antiretroviral therapy, and this was done in the era before the availability of contemporary salvage drugs, so before Darunavir there was Enfuvirtide available, but that was excluded from this trial and subsequently it was shown that there was synergy between T20 and this antibody but people didn’t have access to other suppressive therapies.
|Dr. Daniel Kuritzkes, Harvard Medical School|
There were two doses explored, 15mg/kg given every other week or 10mg/kg given per week, that then converted to every two weeks and for one of these arms for I have forgotten the loading dose, and they were compared to placebo.
So there was a significant reduction in plasma HIV RNA, about a log in both arms, and between 1/3 and 45% had at least a 1 log reduction, but very few achieved full virologic suppression and the CD4 increases were relatively modest and not statistically significant.
Curiously in the arm that had somewhat better virological response there was actually no meaningful CD4 response.
The other thing that was learned, both from the multidose study and from this Phase II study, was that despite the assumption that an antibody targeting a cellular receptor would not select for viral resistance, viral resistance appeared promptly and uniformly in patients who remained viremic, so that almost all of the patients who received the antibody over time developed resistance to Ibalizumab.
These are data just published this year, some six or seven years after the trial, which says something about priorities at Monogram or about what happens when nobody is driving the bus because of the change in the drug from Tannox to Genentech to Timed. You saw the same kind of curious plateauing of the inhibition curves as has been seen with the CCR5 antagonists and has been thought to be a signal of non-competitive inhibition. These are changes that clearly map to changes in envelope, when other properties of these viruses are actually quite interesting.
Instead of reporting shift in IC50 they talk about the change in maximum percent inhibition and you can see that of all of these patients samples all but one show in MPI an increase in IC50 to another anti-envelope monoclonal RPAT4, but curiously performance showed enhanced susceptibility to soluble CD4. They also showed enhanced replication capacity using a model where the envelope, these are un-cloned, so sulfalty amplified envelope from the patient plasma virus is used to make virus pseudo types and they are looking at the sulfurase expression; these are baseline samples and these are week nine samples from that Phase I-b study.
Subsequent work, in fact in the same paper but done later in time by the Monogram group, showed that consistently observed at the genetic level in virus was the loss of two N-linked bi-phosylation sites in V5.
This figure (which is too small to see) shows how the V5 ligand sites lie here in the Ibalizumab region, but remember that the virus is interacting with CD4 and binding, but they are actually not seeing the antibody just CD4 and the envelope so how this precisely applies to resistance is still being explored. They also showed that differences in rigidity of CD4 didn’t seem to have much impact on susceptibility to GP120 that was just engineered CD4 molecules. So where this antibody sits currently is that when Tannox was bought by Genentech. Genentech had previously having decided that they wanted nothing to do with HIV or HIV vaccine research and quickly shed their interest in this antibody by spinning it off or selling it to this company Tymed, which is the group that David Ho has been involved in as a scientific advisor. So Tymed proceeded to do some additional studies and was trying to finish another Phase II study. At the end of the Phase II study I showed you the FDA said that there was not really enough data to make a dose selection they would have to go back and redo a Phase II, and they had been struggling to do a Phase II, but there are really not the kinds of patients that used to be available for doing the kind of salvage study that led to the data from 2005. They have also done some reformulation in trying to develop a subcutaneous injectable form and that is in limbo at the moment, to the best of my knowledge.
So what are the potential advantages to using monoclonal antibodies in a therapeutic setting: they have long half-lives or can be engineered to have long half-lives, they are, as a class, known chemical entities, we have extensive experience with immunoglobulins, and they are generally well tolerated – antibodies – although there is always the potential for some serum sickness like reactions and there were a couple of patients in the Ibalizumab study that had reactions that appear to be hypersensitivity reactions. Then, of course there is always the concern of off target activity by binding to other cross-recognized antigens. There is the theoretical probability of a higher barrier to resistance. But I have to say every drug that has been used to target a cellular target, or been directed against a cellular target has managed to generate viral resistance. Whether it is the antagonism of CCR5, following a CCR5 antagonist, whether it is Ibalizumab. So I think that we have to be skeptical about claims that antibodies directed against cellular proteins will not select resistance. Then there is potential synergy with other monoclonal antibodies and to the extent that these antibodies have been mostly inhibitors of some stage of entry with other entry inhibitors including small molecules like Maraviroc.
But there are also potential disadvantages, which I think have to be balanced against their advantages and again here I am thinking mostly in a therapeutic setting granting that the equation may differ when talking about the preventive setting especially in the context of post exposure prophylaxis. These all require either infusion or injection, and although there was great excitement about the science behind Enfuvirtide and the fact that you could give a 39-mer peptide and it actually had demonstrable and significant antiviral activity as we all know when it actually got out into the clinic it proved to be an enormous challenge for patients to administer on a regular basis for a variety of reasons not all of which would necessarily carry over to some of the other drugs in question here. As things stand currently, other drugs in the regimen would still need to be administered daily. So if you are giving two drugs daily and one drug every week or every other week, how that is a major advantage. It is something that needs to be explored but obviously if several of these agents were developed and could be given in combination one could have an infrequently dosed regimen that was a combination of several monoclonal antibodies. There is the potential for off target effects and this becomes a particular issue with trying to develop a safety database. If these are highly specific and work only in humans and not in non-human primates, then you may not have the ability to observe these toxicities because we are not looking at chemical toxicity, we are really looking at biological toxicity, and here you need to have shared receptors or target specificity across primate species to be able to explore this. It may not be at all feasible to look at this in small animal models. So the more specific the antibody, the less opportunity you have to do a full preclinical toxicity analysis, and although antibodies may be dosed less frequently than drugs, it is expensive to make these and so the cost of goods is at a different order of magnitude than the cost of manufacture of at least some of the antiretrovirals and while most of the pricing of antiretrovirals has to do with recouping investment, you can get to a much lower irreducible price with small molecules than you can with proteins that have to be made with biologics, as the regulatory aspects of biologic manufacture are much more complicated.
|Dr. Daniel Kuritzkes, Harvard Medical School|
The last slide I said has some of the many challenges in development and I am sure all of you can add quite a lot to this list, but the first question would be what is a suitable patient population for doing phases I, II, and III. At the time that Ibalizumab was first introduced, the FDA was very reluctant to see a novel class of drug that might have an effect on viral envelope at a time when Efuvirtide was the only envelope targeted drug administered to treatment naïve patients who had little to benefit from the antibody because Ibalizumab was being developed for salvage at the time and had potentially at risk not only for toxicity but also for the development of resistance that might compromise this drug a little bit further down the road. That thinking may have shifted somewhat given the huge number of drugs currently available but clearly studies need to be done in a viremic population to demonstrate activity and it is harder and harder to find treatment experience patients not on therapy, so really treatment naïve patients are about the only population available for those kinds of studies. The PEP setting depends on the exposure and where you are doing that. You can certainly do PEP studies for safety and Ken has done quite a few of these with different agents. But for efficacy, fortunately at least here and in the US, the risk of acquisition of HIV following exposure are so low that you really couldn’t hope to find a signal short of amassing many thousand patients. These agents also have unusual pharmacokinetic properties or some of them do Ibalizumab has very non-classical PK because it binds CD4, and so it gets cleared by binding to CD4 and to CD4+ cells so its effects may linger, but the antibody actually disappears quite quickly, so it appears to have rapid clearing and that makes estimating dosing frequency, and whether you need a loading dose or not, very hard and because the drug is expensive to manufacture trying to do the right kinds of PK studies to hit on the right dose to take them to Phase II and then Phase III becomes a major challenge. Then constructing the right regimen, you know which drugs do you combine and are you placing potentially valuable drugs at risk with a novel agent whose activity is uncertain becomes an issue, and of course, cost plays into all of this. I did want to finish one point before I finish about Ibalizumab, which I think has gone unappreciated because the studies haven’t been large enough or long enough to sort this out. Remember that in that first single dose study long before there was evidence of antiviral activity within the first 24 hours, there was an increase in CD4 count. That cannot be because of viral suppression, right, that has to mean that even though this antibody doesn’t interfere in vitro with antigen recognition and recall antigen proliferation, that there is something happening with the trafficking of these cells, and whether there is a clinical correlate of that, whether there is some increase susceptibility infection or some impairment of CD4 function we really don’t know. There was evidence of that in Phase II trial, which was carried out to 48 weeks so that looked OK, that was 80 patients, and we know from Infliximab, Etanercept and the others that very often the infectious complications of these antibodies don’t become apparent until the post marketing phase when you have many more patients who are receiving them. I think we just have to be aware of these risks and go into the studies with open minds and with an appropriate safety data collection. So let me stop there and turn it back over to David.
DS: Thank you Dan.
FV: Dan question, the resistant virus that lost a couple of sites in the B5 ligand sites, how rapidly does it regain susceptibility in the absence of Ibalizumab?
DK: You know that is a great question and I don’t know that that has been studied. You would think that they should be reacquired fairly quickly or that the preexisting wild-type virus would take over once the antibody was no longer being administered that has certainly been the experience with both T20 and CCR5 resistance, that we get the wild-type coming back quite promptly.
RR: Do you get CD4 independence if you continue the selection in suboptimal concentrations of inhibitor?
DK: They did not get CD4 independence. That was actually the first thing that the Monogram people looked at in the past and they did not find, people have not seen CD4 independence emerge as a result of continuing selection.
KM: Yeah, is there anything known about the penetration mucosal tissues and what kind of levels might be achieved?
|Dr. James Pan,
University of Toronto
DK: That’s a great question I don’t know, it may be known and (Keith Rayland?) is maybe the best person to ask, he has done quite a lot of work with this in the primate model.
RT: Yes I notice the 25mg/kg dose didn’t appear to be the maximum dose cohort infected - is there a reason for that was it saturated when you enter the systems?
DK: Yeah it may have been saturating I think it was.
RT: Ok, thank you.
JP: Just want to make a comment. You mentioned there that it might be difficult to do the pre-clinical toxicity experiment. Normally we deal with this these days you actually make an in-parallel antibody against the tox species and in some cases we would actually incorporate the cross reactivity into the antibody, so that would deal with that issue.
DK: That is a proper approach, yeah.
??: I also want to say I wonder if you can also see CD4 effector enhancement and even increase your scoped immune reconstitution.
DK: Interesting, yeah we did see some significant line of the CD4 counts in the Phase I-b study.
DS: Thank you Dan.
Presentation 2: PRO140
Presented via Teleconference with Dr. William Olson
AD: Hello is this Dr. Olson
AD: Hi it’s Al DeMaria with the Massachusetts State Laboratory we are all assembled here finishing our dinner and ready to hear from you.
|Dr. William Olson, Progenics Pharmaceuticals Inc.
WO: Ok, it sounds so great. I thank everyone and of course thanks to David Scondras for the invitation to speak to you all. I thank everyone for your interest in our anti-CCR5 antibody PRO140. I suppose some of you may know a bit about our product, others not, and I know its late but I thought before we begin I would take just a moment to provide a background for the context of the current status of this company. Our company, Progenics, was founded over 20 years ago based on initial discoveries in HIV cell entry and HIV has been a major focus of our company for those 20 years. Over that time period, our interests also expanded to include oncology and supportive care, and last year for the first time in the history of our company got a new CEO. One of the first initiatives of the new CEO was to conduct a strategic review of our business. We completed that review and it has two main recommendations. One was that we should focus on a single therapeutic area instead of three therapeutic areas, and the other one that that therapeutic area should be oncology. So that decision has affected PRO140. That program is currently on hold and we have just begun to reach out to companies that may have interest in that program. So I thought that might be important to say at the outset and it is important to say also that these were not easy decisions for our company by any means. They may have had as much to do with future opportunities in given therapeutic than with the particular compounds we have today.
DS: Doctor Olson, would there be any implication with what you said that the folks who made that decision had any medical or other analogous type problems with the compound itself?
WO: No it was not based on any medical problems, it was more a business decision with a lot of emphasis being placed on the need to focus in a single therapeutic area.
|Dr. Ruth Ruprecht (left),
Dana Farber Cancer Institute
Dr. Daniel Kuritzkes (right),
Harvard Medical School
There was a lot of analysis between companies of our size and similar companies, and most of those companies, the most successful ones, have a single focus in terms of therapeutic area. There has been no medical issue with this drug whatsoever. It is a highly active compound and there is an excellent safety profile and I continue to believe that this agent could provide an important treatment option for many patients and so I am very happy to have some time to discuss this product with you today.
You know we have before us today some slides that are from our last public presentation. It was a presentation prepared for a very different audience than today. I thought in the interest of time we could skip over some of these early background slides, maybe skip two slides by it is called PRO140.
DS: We have got it.
WO: And please feel free to interrupt me with any questions; are there any questions at this time?
WO: OK, just so we are all on the same page,
PRO140 is a humanized monoclonal antibody to CCR5, which is a chemokine receptor that normally plays the role in trafficking healthy immune cells in the body but of course it has been co-opted by HIV to serve as an entry co-receptor. The co-receptor used by the most abundant strains of HIV, but other strains of HIV can use an alternative co-receptor known as CXCR4, these strains usually arise late in infection, if at all, in the patient. In my reported studies, PRO140 blocks HIV at concentrations that have little to no effect on the natural activity of CCR5; it is somewhat unique in that regard. In clinic, both intravenous and subcutaneous dosage forms have shown they quite potently prolong antiviral activity, again without any apparent safety issue, thus far. The FDA did designate this product a fast-track candidate based on its properties and its potential to address ongoing unmet needs in HIV infection.
The next few slides summarize pre-clinical data for the antibody, these are all captured in slide eleven, so you can skip ahead that slide is entitled PRO140 Represents a Distinct Class of CCR5 Inhibitors, it has a table comparing Maraviroc and PRO140. Have it?
Group: Have it.
WO: OK, I think that PRO140 represents a different approach to HIV therapy and one that is really quite well differentiated from existing HIV drugs, including of course the only small molecule CCR5 antagonist, Maraviroc, and I think this stems from a solid scientific foundation. There are some fundamental differences in how PRO140 and small molecules like Maraviroc bind CCR5 and the effects on CCR5 post binding. The differences translate into important differences in the virologic and immunologic properties. For example, we mentioned PRO140 inhibits HIV in concentrations of little to no effect on the natural activity of CCR5 if in vitro, whereas in similar in vitro studies Maraviroc is a very potent CCR5 antagonist and in vitro inhibits HIV and CCR5 at a similar concentration virologically. PRO140 and Maraviroc are quite different in many respects. They have different modes of HIV inhibition they show complementary patterns of resistance for CCR5 viruses, and have got potent antiviral synergy when used in combination in vitro. Of course a monoclonal antibody PRO140 has pharmaceutical properties that are very different from Maraviroc and all of the other antiviral drugs.
PRO140 is suspected to be free of drug-drug interaction. The FDA said we don’t need to test this, and you know that can be advantageous to patients with complex medication requirements. Maraviroc of course is an example, we dose up or down depending on whether you combined with hepatic inducers or inhibitors. Maraviroc of course has a black box warning for past toxicity based on small number mutations that put that warning there. It is said to have known cardiovascular effect. However, I believe PRO140 has potential for improved tolerability again we see no pattern of toxicity in either preclinical or clinical studies conducted so far. We do think it is unusual for an HIV drug to reach this stage of development without any evidence of toxicity and that may be a property that is unique to antibodies. Perhaps most importantly PRO140 offers a different dosing paradigm. It can be given infrequently. Once a week, or potentially on alternate weeks, via a simple subcutaneous auto injection that can be taken at home or while traveling. So again all in all we think it really represents a different approach to HIV therapy.
This next slide,
we have completed three studies of PRO140 in HIV infected individuals, two have been with an intravenous dosing form and the third with a subcutaneous form and these studies have all been reported in published manuscripts each of these studies tested PRO140 used as short term monotherapy in subjects with early stage HIV infection, you know who are not candidates for antiretroviral therapy. The treatment groups and their sizes are summarized here, the studies examined the IV formulation given as a single dose and three doses of the subcutaneous formulation. Next slide please.
This slide depicts the antiviral effects seen in terms of the mean maximum or major reduction in HIV RNA in each of the three studies on the right of the slides are results of the IV studies data for the test tube studies is on the left and in each study PRO140 exhibited a potent dose dependent antiviral activity that was highly statistically significant. Regardless of whether we were using an IV or subcutaneous formulation we saw viral load reductions of 1.5 to 2 logs and you know the effects seen with IV PRO140 remain the largest effect with just one dose of any HIV drug. Next slide please.
The next slide depicts the mean HIV reductions over time of each of the three studies. In two IV studies on the right and the SC studies on the left. The single IV dosed apex viral load nadired in 10 to 12 days after administration of the drug. In the subcutaneous administration we saw prolonged and sustained viral load reductions that we saw to repeat when we do dosing, and really we have seen that the SC study provided the first clinical proof of concept for a long acting self administered HIV medicine. Then the next slide please.
This just depicts that the antiviral activity was pretty consistent across patients, here we plotted a percentage of responders in each of the different studies that had different dose levels and by responders that is defined by patients who have at least a 1 log reduction in viral load. As you can see we saw nice dose dependent increases in response rate in each of the three studies, the response rate was 90% or 100% at the top dose levels. The next slide.
The next slide compares some antiviral effects seen with a single dose of PRO140 with those seen with 20-30 doses of small molecule CCR5 antagonists, and we believe that PRO140 stacks up well with the data for small molecule antagonists and scientifically we think the results indicate that PRO140 is able to penetrate and access active ongoing sites of HIV replication on par with small molecule drugs. Next slide please.
This slide summarizes what we know about the genetic barriers of PRO140 to resistance emergence in preclinical and clinical data. It suggests that PRO140 does present a high genetic barrier to viral resistance its really not easy for the virus to elaborate resistant mutation. Our clinical studies did see outgrowth of viruses that used the alternative co-receptor CXCR4 in a small percentage of patients, and this is really in line with what was expected based on prior studies and probably as a reflection more of the sensitivity of the assay that was used to select patients for these studies based. All of these studies used the first generation profile assays but there is no evidence of resistance development from CCR5 using viruses in which there is no preexisting resistance to PRO140 observed in any of the subjects treated and no development of resistance was observed post treatment that reflected either a change in concentration required for inhibition or the maximum percent inhibition, the plateau inhibition, those are really unchanged before and after therapy. You know I think that to us it was somewhat remarkable because here is a situation where we used this agent as monotherapy. We gave a single dose that resulted in prolonged viral suppression for three to four weeks on average up to six weeks in some patients followed by slow washout with the study drug, many would say that those are ideal conditions to develop drug resistant virus and we simply didn’t see it.
The next slide just summarizes the safety finding we have seen, thus far. PRO140 has been generally well tolerated regardless of the route of administration. We have seen no clear pattern of toxicities known to be drug related. In terms of the subcutaneous formulation, administration type reactions have been characterized similar to injecting saline, it is very different from the burning one gets when treated with Enfuviritide. Again we have not seen a pattern of toxicity either in humans or in animals. An interesting side is that we have tested monkeys in our preclinical study and did not see side effects and we continued until the FDA told us to stop that we had reached such doses that it was pointless to go higher. Again I think that is not typical for most HIV drugs.
The next slide just summarizes the PK data real quickly, I know it is late, there are two IV studies on the right and the subcutaneous studies on the left and in all of these studies we have seen a quite predictable PK, the drug has a three to four day steric half-life regardless of its route of administration and we think that those PK parameters are indicative of dosing that is weekly or even every other week. The next slide please.
Based on those clinical findings we selected the subcutaneous dosage form for further development. We liked its potent efficacy, its favorable tolerability and the potential for really convenient self-administration by patients. We have since developed a simplified auto injector formulation that enables the product to be administered really easily. We also like the fact that this device standardizes the injection and hides the needle prior to injection and that is important for people who have an aversion to needles. So we think that this approach maximizes convenience and patient friendliness, and that is what we have to do for a very simple injection once a week or every other week. We have tested this auto injector formulation for safety and PK in healthy volunteers and we were encouraged by their performance.
Ok, this next slide talks about where we see PRO140 and how it might fit in in HIV therapy. We see that PRO140 has the potential to be a real meaningful product. First as a long acting at home administered HIV drug with a real favorable safety and efficacy profile. It could be used of course, in patients with multidrug resistant virus that may not have options. It could provide a compliment to existing therapies to patients who have difficulty adhering to daily regimens. We think it would be a great choice for patients with poorly tolerated therapies. Here I am thinking about short-term toxicities perhaps in patients with compromised organ function. I think PRO140 is an easy choice in patients who have complex constant medication requirements and there are multiple roles PRO140 can play in the existing treatment paradigm and since it is a different type molecule it is putting courage on creative thinking about HIV therapy, I’m sure a lot of that has occurred in the room today. It could be used for infrequent pre-exposure prophylaxis once a week or once a every other week, and again it may be used in patients who have been suppressed for a very long time and would like to take a break from daily life-long adherence to therapy. Maybe PRO140 could provide an effective mode of infrequent maintained therapy. Obviously we’d need to prove effectiveness for that.
The last slide summarizes the key points; maybe I won’t reiterate these things because you have that slide in front of you. Maybe I will stop there, thank you very much for your interest and attention and I’d be happy to answer any questions thank you.
DS: Are there any questions for Dr. Olson?
KK: I am just curious about storage requirements for the auto-inject device?
|Dr. Richard Trauger, CytoDyn Inc. (left)
Dr. Allen Green, Consultant (center)
Dr. Edmund Tramont, DCR/NIAID/NIH (right)
WO: Well we had refrigerated storage and based on the stability data, at room temperature it should be something that could be transported outside refrigeration. So if you were to take a plane or trip somewhere for example you could take it outside four-degree storage for days even a week or more.
RT: You mentioned a 3 to 4 day serum half-life?
WO: That is right.
RT: But there is a fairly long activity is there any evidence that you down regulate CCR5 expression when you use PRO140?
WO: We have actually looked at that, we have looked at receptor occupancy. We are quite efficient at blocking the PRO140 binding site, it is going to have been occupying that site pretty well, but CCR5 is still on the cell surface. We can stain CCR5 with an antibody that doesn’t compete with PRO140 and CCR5 is still there
DS: Any other questions for Dr. Olson? So thank you very much Dr. Olson, and we will be in contact.
WO: That would be really great, thanks again David and thanks everybody.
Group: Thank you (clapping)
DS: The last of the three monoclonal antibodies that we are aware of that are in development in one context or another for HIV specifically is Cytolin and Dr. Richard Trauger is here from San Diego to speak briefly about that particular antibody.
|Dr. Richard Trauger,
Presentation 3: Cytolin
Presented by Dr. Richard Trauger
RT: So let me thank David and let me tell you that we have no real clinical data yet; this is a developmental program. It is a real pleasure to be here to understand what really is happening in this field because my goal is to learn as much as I can while moving forward with this program and see if we can at least capture some of the data that has been shown, it has been really intriguing.
So you notice up here we have the human for HIV infection and we also are looking at FIV. I’ll explain why, because we think we can exploit this as a model for some of the other antibodies that we want to study.
Cytolin is a monoclonal antibody that binds to LFA-1, specifically CD11a, and LFA-1 is made of CD11a and CD18. It was derived originally as a marker for CD8 cells.
This paper was published in Nature in 1987, “A Novel Epitope that can Distinguish Between Effector and Suppressor Cells”, and as you will see it binds to a specific site on CD11a that is distinct from most of the antibodies or all of the antibodies that I have seen that bind to CD11a. That allows us to address some concerns about it going into an immunosuppressed population.
So just as a background, LFA-1 is a molecule, it is an adhesion molecule, its marker is ICAM, and it brings cells together to allow things to happen.
In the case of CTL’s if you block LFA-1 you will prevent lysis but if you allow cells to come together anti-LFA-1 will do nothing, so it presumably blocks the adhesion of cells in sending one thing from one cell to another.
Why is it important in HIV infection? Well this is a paper that shows a number of specific antigens that are captured by the virus when the virus buds from the cell.
See here is CD11a, ICAM also, and this is I believe a non-random assortment of proteins. When I was working years ago in HIV, I had to characterize an immunogen that we were producing and it had a very unique spectrum of antigens that was very consistent. They may reflect the cell type that it comes from but I think there are a number of pieces in the literature that describe this LFA-1 on the surface of the virion.
We are collaborating with Eric Rosenberg, and Eric has been able to pull down virus with antibody-coated wells (top right graph above).
Here you can see is GAG, with or without the antibody, and you can see is a P24 measurement of different isolates that are being pulled down with the antibody, so we believe that this antibody can bind to virus, which is important because unlike the other two antibodies that have been described this antibody appears to directly hit the virus.
Now why is it important for HIV to have this? Well as I mentioned, this is from a paper that describes the virological synapse, presumably this antigen is on the surface of the cell to allow membranes to fuse and to deposit viral information into the target cell to facilitate infection, so in this case the payload is viral RNA instead of cytotoxic granules.
So it makes sense for a virus to acquire this and to use this, the question is can you exploit this as a way of targeting virus infection.
Sure enough people for a long time realized that LFA-1 was a viable target for the treatment of HIV infection; this is just a short list of a few papers.
Interestingly it appears to be a key determinant for infection in memory CD4 cells, and it has been combined with T20 to see if there is enhanced activity. This last paper here from 2009 showed that there was an additive effect and then was a somewhat optimistic statement about the potential to combine these therapies to create something that would prevent fusion and reduce infectivity.
So, as I said it has a unique binding site and recognizes selective PBMC’s, this is again work from Eric’s lab, and interestingly this antibody doesn’t seem to stain CD4’s very well at all, but does stain CD8’s.
The reds are HIV positive subjects the white are HIV negative subjects. There doesn’t appear to be any difference in the spectrum of activity for PBMC’s. These are the CD8’s of dendritic cells, which are really interesting cells in and of themselves in fact they control HIV infection.
No real binding on monocytes, virtually no binding on CD4 cells, and as I said, through epitope mapping we are still confirming, the binding site appears to be in this end of the molecule here, not this end of the molecule, and this [the end we don’t bind] is the part of the molecule that has to bind ICAM.
Antibodies that are targeted to this end (ICAM binding site end) can eventually become immunosuppressive. The most well known of these would be Raptiva, which was developed to treat Psoriasis, after a long use they discovered three cases of PML in 47,000 individuals with an antibody that bound to this end. Our antibody binds here, and this is some work Eric did with some CTL activity that showed there is really no inhibition of CTL activity with Cytolin present in these cultures. So it does not appear to be immunosuppressive; which is really something you’d want to be really strongly confirmed prior to going to trials.
It was used in studies in the 90’s, in compassionate use. It’s safe and well tolerated, there were favorable observations, and we have very little data if not no data on patients who were on it as monotherapy.
|Dr. Richard Trauger, CytoDyn Inc.|
These are two patients that appear to be on monotherapy, and there appeared to be some reduction in viral burden but we can’t confirm that. I wouldn’t say that this is proof positive that this antibody works but it was interesting enough for us to pursue this to see if we could bring it forward into a real-time setting with humanized antibody to really see if we could reproduce and extend some of the data.
So where are we now? We are trying to determine how it blocks infectivity with Eric, by looking at its ability to block virus, to block syncytia, or to pre-treat cells to see if they are then resistant to virus, and as I showed you it is interesting that the antibody doesn’t seem to bind CD4 cells.
We are now looking at infected CD4 cells to see if the epitope is revealed there. It does appear to bind the virus, and so presumably when the virus does bud from the cell it either exposes this epitope or offers something that is accessible, but it is really I think intriguing to be asking why there is this specificity binding to the virus and not to the cell, and LFA-1 has really been indicated a lot in syncytia formations so I am very interested to see in an infection setting if we can block the syncytia.
So there are a number of ways we are going to attack this. We have been doing this for quite a while, and if we had another month before this meeting, I might have data for you now but I don’t have the data now, so again I apologize and again its really a pleasure to present such speculative work but I think we are on the right track.
|Dr. Richard Trauger, CytoDyn Inc.|
So as a therapeutic monoclonal antibody that binds to a site distinct from the binding site of ICAM it does not seem to block normal function of LFA-1 on CTL’s, and I know that Dan made a big point about resistance and how that will evolve. Because Cytolin’s target is not made by the virus, it doesn’t involve any part of the virus, basically it’s ICAM and LFA-1, we think it most likely will not (I wouldn’t say cannot) be mutated around, because the virus does not control these genes.
It is possible to develop virions that potentially will be LFA-1 negative, but I think once those virions cycle through an LFA-1 positive cell they’d acquire LFA-1 again.
I’ll show you the second model, the feline model where we are actually studying some of these things. Again this an antibody that I think is targeting the virus and not the cell that sort of distinguishes it from some of the other approaches going for cellular antigens.
Now, I came from a lab that worked in mouse retroviruses and cat retroviruses, and in particular FIV, I was with John Elder in fact when I first came to California we thought that because of genotypic and phenotypic similarity we might look at FIV as a model. So we started looking for CD11a and antibodies that would bind to cat cells to directly develop an FIV therapy, but also to use this as a model to study antibodies that bind to LFA-1 in an animal model. Because Cytolin with its specificity doesn’t appear to bind any other species but humans, and we are talking to Ruth about looking at primates now, non-human primates, but it really had a very unique specificity so we still want to hear from that perspective. Now FIV and HIV are very similar but there are a couple of really unique differences and they actually really relate to the specie because unlike HIV FIV does not use CD4 to bind, and unlike HIV it does not use CCR5. So unfortunately you wouldn’t be able to run those antibodies through this type of model but FIV looks a lot like HIV and is transmitted by biting, and I don’t know how much you know about FIV, but it does cause dementia and wasting. About the same disease that you see in HIV you see in FIV. So we looked at a number of antibodies, we found an antibody that bound cat PBMC’s and also this 14C1 cell which is a target for FIV, if we put that in for 15 minutes and then infect cells and look over 14 days you can see a suppression of infectivity at this 10 or 15 microgram dose, which leads us to believe that we are probably targeting the virus, in this case we are blocking infectivity. Now, this antibody binds to that loop on CD11a that is the ICAM binding site so there is a potential for immunosuppression over the long run use. We are now contemplating studies in cats that will allow us to study that.
|Dr. Richard Trauger, CytoDyn Inc.|
I am looking at a couple of different ways of measuring immunosuppression over the course of many doses in seronegative cats or seropositive cats, but for all intents and purposes I think we know that we can do what we did with Cytolin, or what we would like to do with Cytolin, in this animal model and then carry that forward. So we filed a patent for this and obviously we are working with John Elder. We have got this pilot study planned and happening next quarter. We have identified a cattery, they have infected cats, we have a discussion with them now to get the dosing set and actually look to see if we can affect something.
So, just to wrap up this is a monoclonal antibody that may be a new class of anti-infectious agents directly targeting virus, or potentially infected cells, depending on the antibody, and we have antibodies under development that include those that bind to this unique epitope or that bind directly to the ICAM binding site. So where we are with this program now is we are wrapping up our collaboration with Eric who has been steadfast in working through all the potential reasons why this antibody may have activity. We have a humanized antibody completed; we’ve got the patent filed on the antibody so we are set for that. We have got discussions underway to get the manufacturing started and we have got people helping us like Allen Green to then start initiating discussion with the FDA to get the study going. So, that is where we stand right now. We are very very excited about moving this forward. I think as a virologist it is a really neat novel idea and I always like to go after some novel ideas but hearing the history and the data from others, I think we are really aware of where we need to be and what we need to be doing to make sure we really have a manageable therapeutic that we take forward. So I think I’ll close there and maybe we can get to the big discussion about everything. Thank you.
DK: Richard it is curious that, how do you explain the absence of binding on CD4 cells but the ability to bind CD11 on viruses, the CD11 is coming from the CD4 cells?
RT: That’s an excellent question. I don’t have an explanation for it. What I am going to look at is that LFA-1 has an inactive and active state and there are certain antibodies that target only the active state of LFA-1. It may be that when infected it forces them into an active state, it may be that when it is infecting CD4 cells you have virus – we haven’t looked at infected CD4 cells to see if it binds those cells. In the HIV infected subjects, it did not appear to bind. But I would rather start in acute infection of the cells and look. So I really don’t know, but it is a very interesting point that I want to sort out.
|Dr. Fred Valentine, Langone Medical Center (left)
Dr. Ruth Ruprecht, Dana Farber Cancer Institute (right)
FV: Have you had the opportunity to grow up some virus in vitro in LFA-1 negative cells?
RT: That is a great suggestion as well, and we did that in the feline model.
RT: Eric is currently now trying to do that in the HIV model and we did that in the feline model and we did not neutralize those virions.
FV: Hmm there must be proof huh?
RT: Well, what we are looking at is if those virions are in culture and go back through LFA-1 positive cells will they reacquire LFA-1, or is there always a population of virions out there that is LFA-1 negative. That is another part of this that we really don’t understand. What is the, well you see this in the cartoon that LFA-1 is present on the surface of the virion. Is it on every virion? Or certain types of virions? I think when you look at the endogenic profile of the virion it is really going to reflect the cell it came from.
FV: Yeah, but it is not random, that has been studied.
RT: I agree, John and I go around and around, John Elder and I go around and around at this about whether or not it is random, I don’t believe it is random at all because I think that you never see T-cell receptor, you never see certain other things in a virion ever, and I think it makes sense for a virus to want to acquire this. The question is, do all viruses do this? Or just the majority that you can culture out? Has some of that data not been generated in cells that were in culture that were all LFA-1 positive to begin with?
So we need to look at this more closely, with clinical isolates, and that is sort of what Eric is doing now. He is looking at a variety of isolates to be sure that every one appears to be a target for us and then try to get an idea of whether or not we are truly blocking that fusion event.
DK: Do you know if you try to precipitate virus, pull down virus with antibody what fraction of the virus is actually pulled?
RT: What percentage? No we don’t know, but Eric is looking at many different things, I have just now contracted Bioreliance, they have a P3 Lab, so we are setting up those types of assays there, and I expect that we might even need to develop an assay based on...I don’t know what the assays were for putting PRO140 out or for putting the anti-CD4 antibody out in terms of how you determine the clinical lot was accurate. Was it viral inhibition did they have an assay like that? Or was it simply binding?
DK: I don’t know.
RT: Well we are going to try and take that a step forward and really quantitate very well what the spectrum of activity is and where it goes.
Any other questions? So David it is your meeting again?
Led by David Scondras, Search For A Cure
Search For A Cure
DS: As you can see from looking at the three presentations it makes sense for folks who are interested in HIV on the community level to legitimately question scientists such as yourselves, and (Dr. Tramont, Dr. DeMaria, Kevin Cranston) and clinicians as to whether or not there appears to be a potential for a promising type of therapy here, and if so, what are the obstacles to finding that out and in what way can we be of service on the community level to help making that happen. I will summarize for you very briefly why that will be very hard just so you are aware of it.
First it will be very hard to test any of these given the abundance of existing antiretrovirals. Finding the appropriate population of people to test these in will be a challenge. I have heard from talking to people privately that there is reluctance on the part of large-scale pharmaceutical firms to engage in any kind of research around monoclonal antibodies. It is not a quick way to make a lot of money. I have heard that the use of passive immunization in antibodies is a very old thing and actually not an unimportant thing to look at. You have heard of some of the potential benefits of such a thing Dr. Huston; the chairman of the National Antibody Society is here, I am not aware of a focus in the United States that is looking at antibody development for the sake of developing a therapeutic for HIV, correct me if I am wrong. A source of funds for it, a source of support, the exception is some money given by NIH to look at a Phase III trial of PRO140, which is being rejected by the company in favor of looking for somebody else to carry it on.
It is discouraging frankly on the community level to see one antibody being developed and sort of set aside in favor of oncology by one company, the second one being developed but very slowly by a small biotech firm, and the third that went through changes as a consequence of companies buying and selling each other whose first papers were back in 2004, it is 2012 for god sake. So that seems to me to be a lot of time with potentially very promising stuff and not a lot of push behind getting it to a place where it could be used.
On the other side, just on a community level I see something that could be very important to folks in developing countries, people who could use a therapy that is not multiple times every day, and could potentially be less expensive. I’d like to know, are those hopes supported by what you know of antibodies? And number two, given what obstacles there are how quickly could we in some way get through them and get to see if this potential avenue, could be explored more thoroughly? I can’t tell you how pleased I am that you are all here, it is amazing.
We have James Pann from Toronto, who works with antibodies, we have people from New York like Fred Valentine, we have some of the most well known people in the whole field of antibodies sitting in this room, like Ruth and some of the most persuasive people I have ever met in my life sitting in this room so if we can identify what these problems are, and I guess beginning with the question is there reason for people like me to want to push to see this developed?
|Dr. Edmund Tramont,
And if there is what are the obstacles and in what way should we be pushing?
ET: Well if you have one success, the rest will take care of itself. There will be a lot of people jumping on that wagon. So the one that seems the furthest down the line is PRO140. Overcome that obstacle, and he made it very clear that they are not going to pursue it, is where I think emphasis needs to be. Somebody has to come and pick that up, some other company.
DS: So item one would be find someone to pick up PRO140.
ET: Yeah, and then take it to the next step, I’ll ask Dan and Ken, PRO140 would go into studies wouldn’t it?
DK: I’m taking the opposite point of view I think that there may be a great potential for the right antibody, but you’d want to pick very carefully which antibody you choose to pursue and I would say PRO140 is the wrong antibody. The reason I’d say it is the wrong antibody is that I, despite all of the comparisons that Bill made to Maraviroc I still don’t see a compelling description of unmet medical need that PRO140 fills, recognizing that Maraviroc, which black-box warning aside, and I can go into why I believe that, there is virtually no uptake of Maraviroc. So in a therapeutic setting where nobody is using a CCR5 antagonist, what is the rationale of developing a monoclonal version that is an injectable monoclonal version of a CCR5 antagonist?
|Dr. Daniel Kuritzkes,
Harvard Medical School
DS: Why is no one using Maraviroc?
DK: For several reasons there is no advantage over current therapy, you need a diagnostic test that is imperfect to exclude the presence of X4 virus, and it is not co-formulated for the other regimen.
DS: Has anyone talked about the use of that drug in connection with pre-exposure prophylaxis?
DK: Yeah absolutely so in fact there is a clinical trial that Ken is leading that the ACTG is collaborating with HB10 on
KM: Well NextPrEP, it will be enrolling 400 MSM and hopefully there will be resources to expand it to also enroll women its going to be starting probably late first quarter, beginning second quarter of this year, it will be enrolling individuals. You know it is strange when you are going to be studying something that has extensive safety studies going into Phase III work, so I don’t know if you call it a Phase I-II or you know Phase IV, because it is an FDA approved drug but it has to be studied for prevention, but that is oral Maraviroc, it is looking at Maraviroc by itself, Maraviroc+FTC, Maraviroc+Tenofovir, and the comparator is Tenofovir+FTC. It is modestly sized so it is 400 individuals the way it is written now and hopefully it will expand to at least 600 including women.
|Dr. Ken Mayer, Fenway Health Center|
DS: As PEP or PrEP?
DK: As PrEP
KM: PrEP, and it is going to be enrolling in 12 cities in the US, so Boston will be one of the cities.
DS: How long before you discover if it is efficacious?
KM: It is individuals who have some risk.
It is not powered to show efficacy, the main issue it is looking at is comparable tolerability because even in iPrex there was some modest level of GI upset for example and questions about adherence so whether because Maraviroc has a limited symptom profile, and then the issue of the blockage there is not as much data for the protective use so that a subset of individuals in the studies will undergo various biopsies and sampling of various mucosal tissues and fluids in the study. So it is a run up to eventually doing a larger study that might show efficacy.
|Dr. Ken Mayer,
Fenway Health Center
There is also a study that actually is enrolling women as we speak in Boston as well at three sites looking at Maraviroc in a ring formulation by itself and Maraviroc + an NNRTI a non-nucleoside reverse transcriptase agent called Duprivirine, and its ring formulation is being studied in women at low risk for HIV, this is an earlier phase study it is co-sponsored by NIH and the Microbicide Trials Network, and the International Partnership for Microbicides. Lori Panther, who splits her time between Beth Israel
Deaconess and Fenway Health Center, is protocol co-chair with Beatrice Hann in University of Pittsburgh and the third site is University of Alabama, and that is also enrolling as we speak. So Maraviroc is certainly moving forward in the chemoprophylaxis realm, and you know I think the monoclonals are very interesting as prophylactic agents, but I think we need a lot more data about them, I don’t know if Deborah you want to comment about a few things you are starting to investigate?
DA: Yes, speaking of prophylaxis we just got an IPCP grant to look at the efficacy of Plantibodies, which are humanized monoclonal antibodies made in tobacco plants to see if they can be applied mucosally to prevent HIV transmission.
DS: Made in what?
DA: They are called Plantibodies, and the advantage of plantibodies is that they can be made very cheaply and very pure and very quickly. There is a lot of interest now in the Department of Defense for making these antibodies for prophylactic protection against epidemic viruses. They are kind of getting resurgence and the technology is getting to a place where we can really consider them as medical grade antibodies. So we will be looking at cocktails of HIV monoclonal antibodies mucosally applied. We are looking at the interaction between the monoclonal antibodies and mucus strands. Because there are some evidence that the mucus strands at mucosal sites actually tether the antibodies and you get longer efficacy that way.
RT: Are these IgA?
|Deborah Anderson, PhD.
Harvard Medical School
DA: We can make them as IgA, but right now we just have IgG1 prototypes, but we want to look at different isotypes in some classes.
DS: At what stage of development are you in? And what are the resources for doing this?
DA: It is a multi-center program project grant. There are ten centers, and we are partnering with a company called Map Biopharmaceuticals, that make the antibodies. They engineer them and then they actually work with a big company in Kentucky that actually has the tobacco plants in big warehouses, and then they scale up make the batches for our research.
DS: Are the companies helping out financially?
DA: It is an NIH program project.
DS: An NIH Project. Ok.
DK: It is at its very early stages?
DA: It’s very early stages, but, in year five Ken is going to try it out in women (joke: laughter) and men hopefully.
ET: Alright, I’d like to get back to respond to Dan, I agree with the comment you made about Maraviroc, in fact Rich and I were talking about that this afternoon. But you don’t see a once a week that looks like it could be easily delivered with that apparatus he has as an advance?
DK: So it has to be cost competitive, right? Because Atripla is going to be generic in three more years, and nobody is going to have the money to pay for branded drug when there is a generic competitor on the market, and scaling up to a much more expensive injectable I just don’t see where the economics are behind that?
|Dr. Daniel Kuritzkes
Harvard Medical School
And I think it is not only my opinion because I think it is pretty well known that Bill and Progenics shopped their antibody around to every single pharmaceutical company in the United States and Europe, and nobody would bite, because nobody saw a commercial future for their product, and even though I think there is a role for scientific discovery at some point you have to get practical about it, and if all the people who are used to making money on these things don’t think there is any value in any future. They are probably right, and I just don’t see how this would fit, PRO140 combined with other antibodies to make a infrequently dosed regimen could be useful, but it would have to be less than once-a-week I think. I think you have to go to monthly. Because the big advantage of injectable therapies is if you could formulate regimens to be administered monthly, DOT becomes a reality. It is feasible.
ET: I agree with that.
DK: Weekly is still too frequent to be feasible for DOT, because of the cost of having to get people to go out and give it. But monthly, is doable.
RT: So I have a question because it is interesting to me to watch both of those antibodies move from an IV dosing to a SC dosing. I didn’t know whether it was because they weren’t getting coverage as IV dosing or whether they felt the patients weren’t really compliant like we all hope they would be to show up once a month. So what is the push to SC?
DK: Well, I think that although infusion sounds great, when you think about the realities of doing that it quickly becomes not so great. So if you have to give an infusion every other week. That is good for 12 weeks, 24 weeks; you start to run out of veins. Then you start to look at a chronic indwelling, and then you start to look at Staph bacteremias and other complications and then it becomes not so great and we are back to the gancyclovir days where patients were being given drugs IV, so I think moving to SC is a smart move, because for longer term administration I think you really do want to be able to give it – if it has to be dosed weekly or every other week, maybe monthly you could do infusion, but again there is much more flexibility about the setting of administration if it could be given SC compared to having to give the infusion. It is probably less expensive on the apparatus side because otherwise you are looking at infusion charges from either a doctor’s office or a clinic. I would love an infusible; we could make money in the ID clinic if there was an infusible that required and infusion center. But I think it is more cost effective if it was self-administered.
|Dr. Richard Trauger, CytoDyn Inc.
Dr. Allen Green, Consultant
Dr. James Huston, The Antibody Society
RT: So that leads me to the next question and that is, there is plenty of chemistry around where you can increase the half-life of the serum protein.
Group: That’s right.
RT: So if it is great looking and you want to give it once a month is there anything going on that is trying to affect structures like this to increase half-life because it would seem like the whole industry would benefit in general from that work.
DK: Right, right, yeah I mean you can optimize the persistence of the antibody.
RT: Albumin is the obvious thing to me, but there is a bunch of things you can try.
RT: Maybe, in terms of an R&D focus, increasing serum half-life might be a goal that you want to achieve to make it a more commercially viable thing so that when you get to the end someone will actually want to use it.
FV: Right, you can employ a depot antibody release mechanism, which has been done for small molecules I don’t know about antibodies.
ET: But, you know if you want to talk practical, and you want to talk excitement, until you show something that works, to put that effort into it making a better mouse trap is a hard thing to do.
RT: That is what I was going to say.
DK: The thing is we know that PRO140 works, that is the other problem with it. We know it works. They have got great Phase II data right, so there is no mystery there and that is partly why the ACTG said you don’t have to do the study we already know it works. So now the issue is, is it worth doing Phase III? Phase III for what? And Phase III in what combination? And what combination would actually be a superior regimen? If all the best you could hope for was non-inferiority? We just didn’t see that that was worth the effort.
KM: It might be helpful if you have a sense of the standing, say what do you think is the current estimate of people who are actually adherent to regimens, needing a third line regimen at this point? That is really a context study, but speaking on it say
DK: Yeah, but well you can imagine this as a first line and know most people couldn’t see patients giving themselves an injectable as a first line regimen when there are single pill fixed regimens now. So for salvage therapy, you know, we struggle to find eligible patients for salvage therapy studies.
|David Scondras, Search For A Cure|
DS: You know there is a contradiction that I think I am sorry, I should have started off with this conversation a little differently at that point in time. If you look at the mathematical dynamics of about 40 to 50 thousand new cases every year and you break out the subsets involved, if you look at the actual power of the variety of different non-cross reactive cocktails that are left out there, you are left with a strong suspicion that is supported by data that isn’t good-enough, or at least good enough to say this, that the vast majority of people on cocktails in fact don’t get adequate suppression. That is 29% in response to the numbers that I look at, which leads me immediately to ask a question, and that is that I think the Fenway has 17% - probably as a result of noncompliance. If indeed, there are subsets of people that are fairly large, whose noncompliance is connected to daily dosing then it seems to me that for that group of people it is an urgent situation to find something else that might work, which is why I always argue that having the NIH or somebody look at a cocktail of monoclonals taken once-a-month, makes some sense. At least for that group.
DS: In Baltimore, I know Redfield is looking at drug addicts and it is just astonishingly horrible, the results are just disastrous, that is to say people get prescribed things that just doesn’t get taken, they just keep missing doses.
|Dr. Daniel Kuritzkes, Harvard Medical School|
DK: All right, so I would agree with two points that you made. One is that the next great advance in antiretroviral therapy is to go to infrequently dosed regimens, but that is once a month, once a week is not going to do cut it. Once a month. Second, is that it has to be in combination. So Progenics was not willing to do studies in combination because that is not a path to approval, they wanted their drug studied for their approval, and we were very interested in studying it in combination with Ibalizumab to see whether you could have a regimen that would be workable and we couldn’t come to agreement.
DS: One could argue that there is a sufficiently compelling ethical public need for this to be argued with the NIH that if companies for whatever reasons won’t do it on their own, maybe it is time to for the Feds to take the property and start doing it. Someone needs to find a way.
DK: Well they weren’t about to relinquish their intellectual property, and we didn’t see the reason to do their work for them...
DS: Well there are good arguments to, all you would need is one state to decide that it is legally important to do it and you would see the transmission immediately
DK: Well what would the study show you? That you could give Tenofovir and this antibody; I mean Truvada and this antibody?
DS: No I am saying, what if you had more than one monoclonal antibody. We have more than one monoclonal antibody why can’t they be used collectively?
DK: And so, in 2017 the state of Massachusetts which may be the only state providing medical care is going to spend $100,000 a year to give to monoclonals?
|[NOTE: Search For A Cure feels this above statement is inaccurate. Our assessment is that it cost about $10 for a dose of antibody to be manufactured and the anciillary costs should price the monoclonal at less than 10% per year of what is presently being paid for any antiretroviral cocktail in drug costs alone]|
DS: Think of it as a situation where there will never be enough people in this situation to warrant it
DK: I agree, so is the state going to spend $100,000 a year per patient on monoclonal antibodies when they could be spending $12,000 a year on pills? For $100,000 per patient it would actually be cost effective to hire a healthcare assistant at $40,000 a year to do DOT and bring your pills twice a day, right?
DS: Well no actually a successful monoclonal if you look at it from a prophylactic basis, and on a world-wide basis and talk to Bill Gates about it, it might actually be cheaper to find it and use it because it will work to put an end to the epidemic.
|David Scondras, Search For A Cure|
DK: So let’s talk about worldwide. So you can’t get clean needles or these devices in any third world country. You can’t have a cold chamber in third world countries, and nobody is giving hepatitis B immunoglobulin to prevent hepatitis, which is epidemic in resource limited settings because they can’t afford the HB; and that is proven therapy. So I think it is a good concept that these antibodies might be useful globally but in reality these are just not scalable because of the cost. I mean, look at the debate that is occurring now in oncology, right we have highly effective antibodies they are becoming more and more and more expensive in vivo, right. Part of that is the cost of goods, part of that is opportunity costs, I mean people can make money at doing this so they are, but there has been a...
DS: Ah, out of curiosity Dan how much of the costs are being driven entirely by the difficulty of constructing and replicating and manufacturing and how much of those costs are related to IP rights?
DK: You’ll have to ask these guys I couldn’t really give you that kind of breakdown, I just know that the cost of goods is not a trivial issue when the cost of manufacture, aside from raw materials is...
DS: The only reason I ask is I know that the cost of Tenofovir is $1.07 per month in India in the Taj Mahesh Hotel retail pharmacy.
DK: No that is my point you can make small molecules very inexpensively, there is a much higher floor for how inexpensively you can make biologics, and you have to be able to demonstrate because a big part of the biologic is process, you have to validate the process.
|Nader Pourhassan, CytoDyn Inc. (left)
Dr. James Pan, University of Toronto (right)
JP: But, I have to say that for monoclonal antibody production, the yield has been increased many many fold and in China for example the biologics, Imogen for example here is equivalent to maybe $10 dollar of US. So it can be done, but depends how you do it. So I think that obviously the monoclonal antibodies make tons of money for companies, the cost of goods is not that high, and does not justify that high pricing. But that is the reality. They want to make money so; also they have control over it that is the big problem. Nobody else can replicate it easily. There is no bio-similar that can easily be manufactured. That is the problem.
FV: Though it doesn’t address David’s question, there is a mode of technology down the pike producing antibodies, which was published this past week I think from David Baltimore’s lab, which if you take the gene for the antibody and put it on an adenovector and the host makes the antibody. So bridging some of the arguments here there is a long term production of antibody, the recipient of the injection does all the work of making the antibody, and all you do is get a vector and put it in them so according not to an antigen but to the primary host.
DS: Similar to vaccine.
RT: Well you know it is a very provocative idea but again you are then back to the whole gene regulation, gene therapy. Look at Vical and how long they have been at this business trying to get anything expressed for a long time.
DK: I think that is a provocative approach and if we probably need a two-stage development process, where you first demonstrated that the antibody was effective at least through Phase II and safe for long term administration.
FV: Right and you don’t get anti-idiotype antibiodies
DK: Right and if you did that you could then go back and reengineer that as a semi AV delivered vector, because you wouldn’t want to give somebody something they are going to make for the rest of their lives, if it turns out a year into it they start having autoimmune implications
DA: I noticed Wayne Marasco was supposed to be here tonight and he is not here, but we just published a paper where we did a similar approach with mucosal transfection. We used ARV vectors and delivered what he calls his minibody genes to vaginal mucosal stem cells and got persistent production of HIV antibodies in this in vitro model. It might also be an approach for prophylaxis.
RT: Are these minibodies camel derived single chains or human single chains?
DA: It’s in plus one plus
RT: I know it, OK.
DK: I Do think there is a significant potential role fore these antibodies as preventive agents and maybe particularly in PEP. Then the challenge is what is the right setting where we can demonstrate that to gain approval, and would their efficacy in demonstrating them in PrEP potentially be a bridge to being able to use them in PEP.
RT: But like you said to be able to get reliable data from PrEP is
DK: Well PrEP is easier than for PEP. I mean we are still looking at large scale studies but I think when you look at the failure of femPrEP and Voice, certain arms in Voice, and the modest success in the initial CAPRISSA study it has to be that adherence is playing a significant role here in limiting efficacy in what aught to be highly effective and if you could get to something that is intriguingly administered and where there is reasonable biological evidence that CCR5 blockade would stop most transmission, that makes a lot of sense, you still have to overcome some of the economic issues of the needles and all of that stuff but a once every other week injection for prevention, where that is the only thing a person needs may be much more plausible as a therapeutic.
KM: And the reason I asked you to comment about salvage is I think there is a role here, I don’t think anybody around the table would say that monoclonals are not interesting and could offer some advantages. I think that it is getting to the point of showing efficacy, so the people who might benefit the most therapeutically are not necessarily the people who have the equipoise to go into a randomized controlled trial to show efficacy in salvage. Somebody who is not adherent or using various drugs may not want to go into clinical trial, likewise the challenge of any PrEP efficacy trial now is that although the data are not unequivocal for Tenofovir based regimens, so there is definitely room for improvement and ethically one would have to offer a controlled condition that would have some active agent and therefore the kind of endpoint you are talking about to show even equivalence is upscale of 5000 participants, it is really getting towards 10,000 or so individuals.
DK: I think you are right but the fact that in a few trials there hasn’t been efficacy presumably because of adherence, it might actually work in your favor in this setting. It would be different than comparing 80% efficacy against a novel agent.
KM: True but you are certainly not going to get placebo.
DK: No you’re not getting placebo.
KM: But 40% vs. 80% some order around there.
DS: To summarize, from Dr. Tramont I hear show me something that works and the rest will follow. From Dan I am hearing when it becomes economically feasible it will start happening.
DK: Or pick an antibody that does something that is clearly different from what others are doing so that there is a stronger rationale.
DS: But there are disagreements about actual per dose costs of manufacturing depending on whom I speak with. So I think some research in that area is warranted.
|Dr. Alfred DeMaria, State Epidemiologist|
AD: The UMass Biologic Laboratories have licensed an anti-rabies monoclonal to an Indian company who are apparently making it for $10 a dose. So it is possible in the developing world. Now you wonder about the cGMP and what is going on there you know, but the fact is that they are doing it and for a rabies monoclonal obviously you are going to save a lot of lives because people don’t have access to HRIG.
DS: The reason it is a concern to me as a public sector, a public policy person is competitive inhibition is not just biological only, it affects economic activities and right now competitive inhibition refers to the fact that the large pharmaceuticals make a hell of a lot more money by repainting an existing pharmaceutical or doing a “me too” drug that has an atom switched, much more easily and successfully than pursuing something that has not one example of a wildly high selling profitable product on the market and I can really appreciate that because the model was built on rate of return to primary investors not on how many people you helped in what way that is something that is supposed to be the churches or the government, and in this case neither one of them seem to be pursuing it so I guess my question is where do you go now? What is the next business?
RR: Well there is another major effort ongoing and that is targeting the viral envelope and over the last two to three years now literally hundreds of new human anti-HIV monoclonal antibodies have been isolated, from work performed by the VRC and by Dennis Burton's group and others and several of those antibodies are absolutely dynamite. They are amazingly potent, much more potent than the first generation of broadly reactive monoclonal antibodies that were out there initially. Now, there are cocktails of maybe three new monoclonal antibodies that are pan-neutralizing. So something like this in my view would have great potential because it has amazing breadth of inhibition and by simultaneously having maybe three or such antibodies in a cocktail you greatly diminish the chance of selecting resistant escape viruses.
DS: What was the name?
RR: Dennis Burton, from Scripps in La Jolla.
RT: Ruth, I had the opportunity to talk to Dennis about six months ago and I asked him specifically about application of these antibodies to therapeutics and he said that he didn’t think that they would work very good in therapeutic settings, he said that he thought that they would work very good in prophylactic settings but they tend to not neutralize the viral swarm out there and it is, you know maybe it is because it was one monoclonal he was looking at and your point is combining them, but I actually sat and asked him specifically what about therapeutics and he said, I didn’t see that happening then. But I think a cocktail really, that is kind of where this is going, if you are going to have one and you can combine them and it is the same mode of administration.
FV: I was going to say there are many far more potent
|Dr. Ruth Ruprecht,
Dana Farber Cancer Institute
RR: One of the new and very potent neutralizing monoclonal antibodies that target the HIV envelope directly could be combined with a monoclonal antibody like the anti-CD11a mAb that targets a cell-derived component. Something like this would really be a very very potent inhibition. Now there is another clinical situation where antibodies can be tested for efficacy, and just about a month ago there was a paper in JAIDS, from Brooks Jackson at Johns Hopkins University. He performed a mother-to-child transmission study in Uganda. This Phase III efficacy study used so-called HIVIGLOB, a polyclonal anti-HIV IgG preparation made from local Ugandan blood donors, HIV positive individuals who had more than 500 CD4 cells. The idea was that these were still healthy individuals who therefore would be more likely to have neutralizing antibodies but neutralization was not a listed criterion. So - IgG preps were made, and Phase I and II clinical trials were performed over the years. For the Phase II clinical trial, mothers and their infants were either given single-dose nevirapine alone or single-dose nevirapine + HIVGLOB. The mothers were given one dose at 200mg/kg at about gestational week 36 to 38, and the infants were given a dose of 400mg/kg roughly within the first 18 hours of birth, one dose each.
The bottom line was there was no prevention of acquisition at all. If anything, there was a trend for increased acquisition in the nevirapine+HIVGLOB group compared to the group given only nevirapine. So - the somewhat lower dose of HIVIGLOB given to the mothers prior to delivery may have acted to enhance virus acquisition.
DK: Only had enhancing activity.
RR: Who knows, but I am just bringing this up because the standard of care in Uganda is now single-dose nevirapine. However, it is not perfect and it does not protect against milk-borne HIV transmission. So in this situation there is still a relatively short window of opportunity to look at efficacy of passive immunization with monoclonal antibodies, but soon triple therapy with drugs is going to be given to the mothers to also block the milk-borne HIV transmission. So the window is closing.
DS: Tell me again what the vertical transmission did.
RR: So basically there was no efficacy and if you looked at the raw data there were actually more HIV positive infants in the combined group, single dose Naviriprine+Hiviglob, and at birth that difference was statistically significant.
DS: Any explanation?
DS: A lot of theories
RR: A lot of theories, for some reason the control group in that study had unusually low transmission rates, much less than the second control group they had in the same study, so there are a lot of questions.
RR: But the one thing was clear, there was no prevention of acquisition by the addition of HIVIGLOB.
ET: Yeah that was the key. VRC antibodies are going into, are being tested therapeutically, I can tell you that. Or will be tested.
JP: Technically you can, if you want to target multiple antigens you can always combine by making bi-specific antibodies able to target more than what you, able to target three antigens if you like emphatically, so that can be done. Technically some companies already pushing on that front, already bi-specific antibodies that work very nicely.
RT: You can make penta-specific antibodies.
FV: Thinking about antibodies therapeutically you are struggling against a much larger amount of virus with a much greater chance for mutations
RR: We used combination regimens. We actually gave a combination of three monoclonal antibodies as post exposure prophylaxis against a single high dose challenge in the infant rhesus monkey model and we got complete prevention of virus acquisition when there was a time interval of 1 hour between the initial virus challenge and the onset of passive immunization with the monoclonal antibodies. With no acquisition.
But again this was with a triple combination of human anti-HIV neutralizing monoclonal antibodies
But again this was with a triple combination.
DS: I want to mention the fact that Dr. Huston, do you all know Dr. James Huston? I thought it was gracious of him to come he is the chairman of the National Antibody Society. If you could describe the society a little bit I would appreciate it, they just had their annual meeting in San Diego if I remember correctly.
|Dr. James Huston,
The Antibody Society
JH: Yes, well the presentation that William Olson made was from our meeting a year ago our meeting in San Diego, which was also, called the IPC meeting that the Antibody Society was organizing for the last 15 years and finally the society formed about 5 years ago. Dennis Burton was one of the founders in fact and so HIV is always somehow worked into the program in a significant way, so we can be found on the Internet at www.AntibodySociety.org. It is a website that is meant to be quite useful there is a news section that our current president Janice Reichert writes every month which describes all antibodies that have gone through the FDA or are midway through, keeps all that up to date. There is an initiative that Richard Begent, who is an emeritus professor and head of oncology at the University College, London which deals with systems medicine and bioinformatics of keeping data in a way that you can share it between labs and that it is in your output folder, it is a standard program that the NIH really could write. This could apply to any kind of therapy not just antibodies so, on the website are all of the references and access to the schemes that you could apply to your own programs.
In general the society’s membership is international and interestingly about half are from academics or research institutions and half are from industry. I think that I’ve worked in industry for about the last 17 years and I was always accused of being too academic, when I was an academic I don’t know what they accused me of. But I think that my PhD advisor did his post doc with Edwin Cohn and John Edsall at Harvard and so it is somewhat appropriate to close the circle and be here and to raise the question of why shouldn’t you be making modern antibodies here. You know antibody libraries as a source of human antibodies is really the vehicle that everybody can use, technology takes people who are well trained but it is not really that expensive, and since NIH pays for most of the libraries that people in academics are using you can have access to them and produce materials surprisingly cheaply. I can’t speak for specific companies, but it is not so far off the cost of a good small drug. Certainly not something if you are going to be administering SC doses of 100 or 200 micro liters it is not a barrier to treating anybody the device becomes the expensive part not the antibody, and you can get those made somewhere else cheap. So I think that living up to my reputation as a sort of turncoat I would suggest that maybe the opportunities for the state and for academics, some institutions like City of Hope and others around the country already have got their own GMP facilities. The processes for making human IgG’s has plummeted and improved very dramatically so that it is both easy to find the people who know how to do it in an area like Boston and also a principal when you can start to allow these sorts of studies we have been talking about have barriers about cost or justification. You know it is already routine in some companies. The technology is already there to make all of the clonal mixtures, so you can make several antibodies at once, and the FDA is perfectly satisfied with that as long as it is reproducible, which it is if you vial your stocks identically and always start in the same way.
|Dr. James Huston, The Antibody Society|
So I think that there are unusual opportunities in the private public sector to help jumpstart some of these things and also to the extent that there are financial benefits. You can reap benefits. You don’t have to make billions of dollars a year for it to be a big advantage. A few hundred million dollars a year might be good enough to be an advantage but being able to test them is really the decisive issue. NIH, formed the MARC facility in order to get past just this bottle-neck, but now I think it has got so many people standing in line that they have to give out grants just to get people to manufacture antibodies. But you can use the Mark facility as a great model, blue print and place to learn from but in terms of unmet need its huge and in terms of opportunities and clinical experiments to be done, that is the bottleneck. It is just providing the GMP material and if the companies don’t want to release their antibodies, and don’t quote me on this publicly, you should have your own human antibody library lab, and you select them against similar sorts of targets and you make a sort of generic version in which the state has rights to. It is just the thing that a venture capital firm would do if they wanted to start a competing company in an area. So I don’t see any reason to not save lives just because a few companies feel they have to hold on to something until their intellectual property has deteriorated to the point when it is worthless. You know a 20-year half-life on a patent is worthless once it has gotten past the 10-year mark if they haven’t gotten into clinical trials and they can’t recoup their expenses.
RT: Well, it is not a bottleneck here I think it is more - can we leverage this therapy into something that really has clinical utility. You know I have a great scientific idea, and I have a really interesting target but I can’t go forward and develop this without, you know looking back, if I can’t get this into people and it does something. I am not interested if it doesn’t do anything. So I need to understand how to take advantage of the history of what has been going on to move this forward and then how to build upon that, because there is always a lot of possibility for 2nd and 3rd generation molecules.
|Dr. Richard Trauger, CytoDyn Inc. (left)
Dr. Allen Green, Consultant (right)
I think there is a lot of opportunity to alter the chemistry of the molecule itself. Just to make it increase the half-life, get it better bioavailability you know it is an antibody molecule we can do that, and I am coming from a background in oncology as well and when I think back to why people really didn’t do that. I think it is because they had enough they got enough out of it, because they could get what they wanted. So maybe there is precedent here to look deeper at this molecule and, here is a start of what we have. When we talk about antibodies, or antibodies, as we know them today. Maybe antibodies as we use them tomorrow will be suited to this particular application and then we can talk about discovers and antigens and new patents and all that stuff. But, we have to make these things, we have, I have to determine, can I get this thing to be a clinical candidate that is realistic, that really gets somewhere, and does something for someone. That is the challenge right now.
AD: It seems like the fundamental problem is it is not 1994 and people are getting very good treatment with available drugs and that even people who are not doing well could conceivably benefit, or, you are never going to be able to do the trials to address their problems and so, if there is a role for these products it seems like it should be prevention.
DK: I think that the CD11 antibody, one can see a path to Phase II. Because I think it is a novel approach. It is a very interesting question; does targeting an adventitiously incorporated cellular protein even if it is not so random into the virus provide a suitable target for a virally directed therapeutic? And so you could demonstrate, hopefully, anti-viral activity and then depending on the magnitude of that activity you have to figure out then what next, because I think where this would fit in therapeutically is a question. In my mind it has a substantial advantage over CCR5 targeted therapy just because there is not an existing oral alternative. Secondly, at least so far, in-vivo studies may show us differently, it isn’t obvious that there is not an alternative form of virus that would already be programmed to escape the blockade. One area where a number of these antibodies are of interest, especially ones that are working either against the virus or against other cellular targets is persistent viremia because we know that patients even on suppressive, or so called suppressed therapy, are still producing viruses from cells, which many believe are activated latent infected cells, others say it is ongoing low level replication. If you can extinguish that last bit of replication and remove that last bit of virus with another kind of approach, in a setting of suppressive therapy, first of all that becomes much easier to study because you have got an abundance of people on suppressive therapy, and now there are tools to monitor quantitatively residual viremia and there is a question of does doing that reduce the residual re-inactivation? The only problem with that from a drug development perspective is I think that is a fantastic clinical experiment to do, but, does that get you to an approval? You would have to then do a study that demonstrated clinical benefit. Which takes you back to a large scale trial, because you are looking at thousands of patients to demonstrate that reducing CD38 expression or reducing IL-6 levels, actually means something. But as initial steps I think these would be really very interesting experiments whether CD11 antibody or Dennis Burton’s antibody or the VRC antibodies
RT: And they provide very valuable secondary endpoints when you are starting out to see is there a path to follow, Ruth...
|Dr. Ruth Ruprecht, Dana Farber Cancer Institute|
RR: There is another point. You could combine your anti-CD11 antibody with another neutralizing anti-HIV antibody, which could result in synergistic inhibition of the virus in HIV-infected persons. Chronically infected cells would, however, still continue to release virus particles. These would be covered with the two different types of antibodies, which would prevent the virus particles from infecting new target cells. This scenario would result in the following: a) viral RNA copies will be detectable by RT-PCR and the number of viral RNA copies may not show much difference compared to pre-treatment levels, and b) the number of infectious cells (i.e., cells capable of releasing infectious virions) could drastically decrease or be undetectable. What should be done in this passive immunization is to add a second test, an infectious center assay. As mentioned, viral RNA loads may not change because the physical particles containing viral RNA molecules may still be present but rendered non-infectious by the blocking neutralizing antibodies.
We have actually done this double approach and published the results (Rasmussen et al., Neutralizing antibodies as a potential secondary protective mechanism during chronic SHIV infection in CD8+ T-cell depleted macaques. AIDS 2002; 16: 829-838). In this study, we looked at the role of neutralizing antibodies in a rhesus monkey model. We had vaccinated these animals, which resulted in the induction of good levels of neutralizing antibodies as well as cellular immunity. The animals had been partially protected from a virus challenge and suppressed viremia after the acute infection. The question then was: What would happen to viral RNA loads if we knocked out the CD8+ cells? What would happen to the number of infectious cells? To address this, we gave a toxic antibody to these animals to temporarily destroy their CD8+ cells. Once T-cell surveillance was abrogated, virus was promptly released from the reservoir of infected cells. Viral RNA loads rose to levels that were comparable to those in monkeys who were newly infected with the same virus. However, in the vaccinated animals, neutralizing antibodies were on board and present in the circulation. Once virions were released, these particles were immediately covered up by the neutralizing antibodies, which blocked further virus spread. As a result, the CD4+ cells did not get infected and did not get killed. Control animals that were newly infected with the virus had similar levels of viral RNA, their CD4+ cells quickly became virus-infected, and when such cells were analyzed ex vivo, they released infectious virus. This illustrates that viral RNA load measurements need to be combined with an infectious center assay. Just looking at viral RNA loads only gives you half the story. If the virus is actually covered up with neutralizing antibodies, RT-PCR would still be positive, whereas the infectious center assay would show huge differences because neutralizing antibody-covered virions have nowhere to go. Just to give you some numbers of the infectious center assay: In the infected control monkeys, without neutralizing antibodies, we detected over 1000 infectious cells per million peripheral blood mononuclear cells. In contrast, the vaccinated monkeys with neutralizing antibodies present but temporarily depleted CD8+ cells had 100- to 1000-fold fewer infectious cells – although the viral RNA loads were similar in the two groups.
FV: So you have the potential, by keeping CD8’s low to purge the system actually. So you then keep the CD8’s low, stimulate all the cells under cover of antibody and improve the system all together.
|Dr. Fred Valentine, Langone Medical Center (left)
Dr. Ruth Ruprecht, Dana Farber Cancer Institute (right)
RR: Yeah, yeah, but there is one other aspect, and this has to do with cure. The current drugs have very imperfect tissue penetration, and that is why we have these sanctuaries and even in the key tissues there is a problem, in terms of actually measuring the drug levels. Antibodies are known, especially of the IgG variety, IgG antibodies are known to have good tissue penetration, and they even go onto the mucosal surfaces. So you basically get three bangs for your buck, because you get the blood levels, you get the tissue levels, and you get the mucosal fluid levels, and that could multiply the clinical benefit.
RT: So you think measuring pro-viral DNA would be of use?
RR: No it would actually have to be something like the infectious center assay. We actually, I mean it was logs difference logs, thousands.
FV: Well it is logs period if you simply do quantitative cultures versus RNA,
RR: Yep that is what we did
FV: anybody who lived through the transition said that you were dealing with a million. Before, you were dealing with a few thousand; most of the virus it measures were empty.
RR: I remember the results. The viral loads were roughly the same between those two sets of animals. But the number of PBMC able to release virus in the control group was greater than 1000 per million cells. In contrast, in the animals where the neutralizing antibodies were around, it was only maybe 4 or 16 cells per thousand were able to make virus. Huge difference. But the viral loads didn’t show it.
RT: Great point because it is particularly relevant to us since we think we’d have more of an attachment to the virus than the cell.
RR: Yeah, yep. Infectious PBMC. The number of infectious PBMC by endpoint titration per million peripheral blood mononuclear cells...
RT: as in did that eliminate responses...?
FV: Well this is really meager and conceptual
DS: Amazing. You guys are terrific incidentally. One thing that was mentioned a little earlier just an aside, maybe you are aware of this or not, Dr. Pan you are from Toronto if I remember correctly, and my understanding is that the Canadian government already finances a human antibody library in Toronto at the University of Toronto is that true?
JP: That is right.
DS: Can you just briefly describe how many antibodies you are talking about? And can anybody use them?
JP: Well the idea was to set up a kind of pipeline approach to develop antibodies against the 100,000 different targets. Including receptors obviously of relevant therapeutics as well as a reagent, you know any transcript factors of the enzymes; there are a lot of funded grants for those projects actually. We also have a large number of collaboration with small companies, as well as other universities to develop antibody for their own purpose as well. So there is a lot of collaboration going on. The effort was initiated so we have built up some libraries, the common libraries and a fake display approach I guess to identify in human the antibody directly, the idea to move quickly past proof of concept for cause mostly and when you do have an antibody for other disease as well, but mostly oncology.
DS: I wanted to mention it only because Dr. Huston had mentioned something like that earlier for the United States, NIH apparently is overloaded
JH: Well, this is a protein production facility which can make clinical grade antibodies or other proteins for clinical trials, because they found they were spending billions of dollars a year and nothing was getting into the clinic even though it is ready because basically a company would always have to step up to the plate
AD: To provide production capacity
RT: Well that is to find what you want to make
|Dr. James Huston,
The Antibody Society
JH: I am sure everybody in the room including me had a grander program project grant that died a sad death because it never got past that juncture, because our companies wouldn’t provide the resources to make the antibodies. It doesn’t cost billions of dollars.
AD: The Biolab is actually going through a transition right now as they are going to be getting a new director. A new director probably will be changing some of their strategic direction. They are still sort of focused on their public health mission and an orphan drug approach to their product development but they are also looking at utilizing their capacity to contract for production of a product for clinical trials. They could never do it commercially but they certainly have enough capacity to go to clinical trials.
JH: Well as I said it turns out that, if you are administering something SC, if you have the antibody that is either immunocytokine or its armed with a drug or it has fantastic functional activity and you can administer it SC like the one we heard about, then the amount of antibody per patient per dose is very small and you can make it in a very small facility.
JH: Certainly it is also possible to make them in E. coli using fermenters.
AD: Or tobacco plants.
JH: Exactly. There are other companies who have very good technology also.
RT: As the Great Yogi Berra said, “In theory there is no difference between theory and practice, in practice there is”
JH: I don’t know if Yogi Bera took chemistry, but if he had I think he would have also said that there is no substitute for doing the experiment
RT: Yeah exactly.
JH: and I think that really goes to the clinical experiment. That’s really the decisive issue and I think if people like you and the NIH and other private resources can be marshaled to provide antibodies in one like this example for clinical trials so you can test six or eight or ten ideas, if one of them really works that is a huge success, and if you can say large numbers applies. The same technology applies to any number of different diseases, and as a field we are still just scratching the surface, and so I think that the public good is well served to not keep the genie in the bottle, but to really share it as fast as you can.
Search For A Cure
My friends in England, who were the first to have a single chain antibody in patients created their own GMP lab, that they had to spend a year writing IND forms and they had the cover of Nature Medicine, with the first trial with a single chain FV. But, that was just the first step in a long development program, but it was a decisive one because everybody was worried until you’d done it, and so you know we have lots of brave clinicians ready to do these things but you know everything you can do to make the materials available will really accelerate the process. There are lots of ways you can really make the political forces feel it is cost effective option because you get some benefits for that, real benefits, but you can fit in the future health plan and not in the past one.
DS: I am going to join the society.
JH: Good it is only $100 a year.
DS: Listen, first I want to share with you that at some point in the near future you will each be receiving a summary of the meeting, that’s why there are microphones here and a photographer. You are welcome to comment on it or change portions of it if you feel there was an inaccurate or misunderstanding made by people who were trying to accurately compile an understanding of the meeting.
DS: Each of you is just beyond admiration for using a Friday Night, to come out and give us some free time and advice I want to thank you we could never afford to pay anything for this it would just be beyond measure.
RT: Thanks to Search For A Cure.
DS: This is not kicking you out it is saying grab a pastry have some coffee talk to each other and thank you so much for coming. We will have another one at some point in the future when we figure out what the use of it would be.
|A SPECIAL THANK YOU TO ALL OF OUR PARTICIPANTS|