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Sunday, 04/24/2016 9:11:02 PM

Sunday, April 24, 2016 9:11:02 PM

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Please find below the transcript of Dr. Prin's presentation entitled "The Future of Vaccine Treatment in Brain Cancer by Robert Prins, MD" from his March 28, 2016 video with the Seattle Science Foundation.

I start it in the 8th minute... simply because that's where he first mentions Northwest and gets into the P3 Trial. I had posted a portion of this a few weeks ago, but it was buried in a post where I responded to a fellow poster and perhaps some didn't get a chance to read this. That portion took us up to the point where Dr. Prins speaks of the upcoming partnership of DCVax with one or both of the Big Pharma companies... Bristol Meyers Squibb (BMY) and/or Merck.

You may want to view the video again, as you read the transcription.

Please forgive any typos.

Here is the first section that I'd posted (for those that already read or grabbed it for the files):

Based on these early studies, we partnered with a company, Northwest Biotherapeutics, to kinda move this out beyond our single institution studies, where dendritic cells, which are not easily made, and you need a GMP suite, so while we have that at UCLA, not every institution has a good manufacturing suite where you can just manufacture monocytes that are GMP grade. So in collaboration with Northwest Biotherapeutics, we initiated multi-center clinical trials, one of which is ongoing right now in a randomized fashion.

This is the design of the study that’s going on right now and they’re still accruing patients so it’s not, we’re not going to talk about that.

With that background, I thought I would kinda provide some sort of additional thoughts and relevant issues about personalized immunotherapy and what this means. And I think there are essentially three issues that are pertinent, especially to you as clinicians. One, which subtypes of GBM should be treated by immunotherapy? So we’ll go through a couple of anecdotes. (Two) Why is vaccination in the setting of advanced disease, or patients that are progressively growing… why is it less effective? And (three), which target antigens should we be actually vaccinating against?

So here’s a Tale of Two Tumors. This was shared by Linda Liau, this are actually a couple of patients in our first phase one clinical trial. So both have tumors in the same basic location, and I assume the oncologists can help me out here if I need it. These are patients that got surgery by Linda. They got standard chemo and radiation. And they were vaccinated on our phase one clinical trial with an autologous tumor lysate pulsed dendritic cell vaccine. But you can see that the survival is obviously quite a bit different. And we started wondering why one patient survives, and one patient doesn’t survive as long?

So it became clear that, and you’ve heard a lot of this, that a GBM is not a GBM, even though it’s called a World Health Organization grade IV tumor, there’s a lot of heterogeneity. And awhile back, Stan Nelson and Paul Michel at UCLA began looking at gene expression profiling of all these tumors. And as you’ve heard, there are several different subtypes of glioblastoma, and some of the early studies that they published, and even though they say Type 1A, 1B, 2A, 2B… these are really the Proneural, the Mesenchymal, and the Proliferative groups. These were compared with survival and you can see that there’s some subtypes that definitely have different overall survival. This group right here (points to right side) is the Proneural group, which is the enriched with the IDH mutations. This was confirmed by Heidi Phillips with the UCSF group, and they named it more this Proneural, Mesenchymal, and Proliferative subtypes and those seem to have caught on. And they essentially are enriched for gene groupings that are associated with neuro development… Classical, Proliferative markers and invasion inflammation and (indecipherable ??) of the matrix, these are essentially what these groups are.

And we sorta began to wonder whether vaccines might be having more effective long term survival in different subtypes. So we did micro-ray gene expression profiling on the first 23 patients in our phase one trial, and looked to see which subtypes and how well they did on survival. So one thing that was clear is that when we looked at the patients that had proneural and classical subtype, that their survival was no different than what had been seen with standard chemo and radiation in a large group of patients that was shown here. However, if you looked at our patients that had a mesenchymal subtype, actually, their survival turned out to be highly significantly elevated than what you would normally see, or expect to see. And so we thought that was interesting. Why mesenchymal? Mesenchymal often has the worst prognosis. Why would these patients have longer survival, especially on our dendritic cell trial?

And if you actually look back, a lot of these patients were enriched for these sorta pseudo-progressor cases, which they look, you know, after therapy, you see what looks like to be progression but goes away on the T-1, T-2 flair. But if you think about the mesenchymal subtype, they actually are known to be associated with inflammation. So we began to wonder whether maybe these are more immunogenic types of cancer… or this subtype is more immunogenic. And it was clear that mesenchymal subtypes have more endogenous T-cells, even before therapy starts. And then after therapy, they have a significant higher T-cell content after therapy.

So what we think is that different subtypes of tumors have/are different immunogenicity, and have different endogenous immune responses. And by doing vaccine in these mesenchymal type patients, you’re actually just re-activating a response that had already been there. And it’s more effective that way. So one anecdote of what we’ve been working on.

Secondly, why is vaccination in the setting of advanced disease, or progressive disease, less effective? This has been sorta the achilles heel of any vaccination, in pre-clinical models and even in patients. If patients are actively progressing on treatment, they are almost uniformly do not respond. So why is that? Could we develop models to sort of test what’s going on? We notice certainly early on that in patients in our clinical trial that not only if they had progressive tumors at the time that we were beginning vaccination, or if they had expression of some genes that are known to be immune inhibitors, such as TGF beta, or IL-10, that these patients didn’t mount responses. They didn’t induce T-cell infiltration after the vaccination. So we began to just think about mechanisms by which this might happen, and see whether we could look more in pre-clinical models. So we set up and went back, back to our pre-clinical model. And this is just a mouse model. Alright? These are murine glioma cells injected into the brains of mice and looking to see whether different treatments work. What I’m not showing you is that if you vaccinate mice, and then challenge with tumors, you basically can cure mice. However, if you wait for a tumor to become well-established, meaning it’s progressively growing, and you give the same treatment, it doesn’t work. Alright? The survival of a dendritic cell vaccine tumor lysate pulsed, or even a PD-1 blocking antibody, which is in the news these days, it doesn’t work. So this doesn’t happen because you’re not inducing immune response. We can see a robust inflammatory T-cell response. We can get T-cells there and they’re even activated T-cells at the site. So why is it that we’re not getting extended survival in a mouse model?

What we did notice is that vaccination in the setting induces a significantly large proportion of early myeloid cells and macrophages. So this is a flow cytometry plots of different populations that are within tumors. And what we notice that they express is PDL-1. High levels of PDL-1. PDL-1 is an immunomodulatory agent that binds to PD-1 on T-cells and turns off their functional activity. So is wasn't the tumor cells that expressed PDL-1. It was actually macrophages. And myeloid cells. And others. So since they expressed such high levels of PDL-1, we reasoned that blocking the effects of PD-1 or PDL-1 on macrophages might actually be a strategy. So when you do the same situation… you wait for a well established tumor, you give a dendritic cell vaccine, and you couple that with an antibody, a blocking antibody to PD-1, the survival is recovery. We see the same survival here that we see in the prophylactic setting.

So, we actually think this is relevant in humans. We went back and looked at our patient population, that were treated on a dendritic cell trial, and looked at, this is hard to see here, but we’re doing multiplex staining for CD-8 T-cells that express PD-1. And it was clear that PD-1 was up-regulated after vaccination. And, if you did an ex-vivo assay to look at whether you took out of a tumor you grew T-cells out of that, and looked to see whether they would kill the autologous tumor if you blocked PD-1 right before you’re put on the tumor, the killing was significantly higher. So we think this is a strategy that’s based on mechanism.

And, we’re actually designing a new clinical trial right now in which dendritic cell vaccination is going to be combined with a PD1 blocking antibody. And the reason we think it’s going to… we hope it will… work is because this is the inherent biology of these types of tumors. In the no treatment situation, these tumors are not inherently immunogenic except for some subtypes. There is no anti-tumor immune response and the tumor progresses. If you give dendritic cell vaccination alone (note: the slide shows DCVax which is NWBO’s trademarked name), you can induce a T-cell response but you get this macrophage infiltration that basically inhibits what you just started in the environment. If you give PD-1 blocking antibody by itself, alright, it doesn’t work because there is no endogenous immune response. So there aren’t any T-cells within the tumor that you can activate their function. However, if you give, if you induce a T-cell response, and you block a negative regulatory molecule with an antibody, you can then get significant rejection of the tumor (note: visual shows “tumor eliminated).

So based on this, we’ve already negotiated with a couple of companies, with BMS and Merck, to partner with a dendritic cell vaccine. Hopefully a clinical trial will be starting up soon.

Sounds as if this trial will at least focus on recurrent GBM, as it seems that it is when the tumor is already progressive, that it will benefit from the CI blocking the PD-1 or PDL-1 will help the T-cells, which are already there from DCVax, work.

Here is the next portion of the transcription... taking you through to the 26th minute...

And so lastly, I think what’s also important is which antigens we should be vaccinating against. What we’re doing right now is we’re taking primary tumor cells, we are freeze thawing and taking lysate. Alright? The vast majority of tumor lysate is gonna be self, alright? It’s not going to be specific.

There’s going to be a small minority of these proteins which have mutations, or have antigens that you can activate the immune system, but the vast majority are going to be … not relevant. How can we enrich for the right antigens? And we think, based on a lot of the new sequencing data, gene expressing data, that mutations and antigens, and what’s immunogenic… seem to be different in every every patient. So vaccinating against EGFR, or vaccinating against Survivin, or FA2… alright… you can do that and induce immune responses but they’re not inherently immunogenic in every patient. Alright? It’s kind of an “all comers” but every patient’s different. And what one patient responds to endogenously is not the same as the other. And I think that’s clear right now.

And I think this comes on the heels of, you know, prominent studies that have come out lately where targeting one agent, one antigen, leads both to loss, and it hasn’t really resulted in objective clinical responses in randomized studies.

So what are the best antigens, or which antigens does the host immune system recognize? Well the majority of tumor-specific T cells don’t recognize well-characterized tumor associated antigens (TAAs). They figured this out mostly in melanoma a while back, because this is one of the most immunogenic cancers, and they began looking to see whether the well-characterized melanoma antigens… all the T cells were specific for them. They were essentially finding out that the vast majority of all these tumor-specific T cells that could come of a tumor didn’t recognize the ones they thought they should be recognizing… the pigment synthesis proteins, part one and two gp100, tyrosinase. So… what they’re finding is that actually T cells recognize mutation-specific epitopes. So somatic mutations in a tumor cause an amino acid change which actually gets presented on MHC with a different amino acid sequence. And that creates a new target. That target is different for every patient though. And it’s specific to their somatic mutation burden.

And I think this was figured out about five years ago… this is one of the early studies (“Exploiting the Mutanome for Tumor Vaccination”) in a melanoma model they did sequencing.

So how does this work? How would you identify which patients, which patients and their tumor would have antigens that the immune system would recognize. The strategy is sort of outlined here. You can identify tumor specific somatic mutations by gene expression. So what we’ve already talked about… RNA sec (sequencing), pol exam sequencing. You basically figure out the mutations, you screen them through sequencing data, then you actually filter in silico (computer simulation), and then using algorithms, you can figure out whether amino acid changes create epitopes on that patient-specific HLA. And you decide which ones should have enhanced binding.

And actually, what’s interesting, and I won’t bother you with a lot of details… but if you look at what T cells recognize… what classes of oncogenes or mutations… there are really very few of the immune response T cells that recognize actual driver cell mutations. They recognize mutations, but they’re basically passenger mutations. It has nothing to do with whether that’s making… this oncogene is making that cancer drive. The immune system recognizes just changes. And it’s basically a random process that recognizes, that creates a new protein which creates enhanced binding on MHC.

And the cancers that are the most immunogenic are the ones that have the most mutations. It’s a numbers game. The more mutations you have, the greater the likelihood that a mutation will create a random new peptide that binds on MHC.

It’s clear that… this is basically just a list of a whole bunch of different types of cancer and their somatic mutation rate. They’ve gone through mostly the TCJ (?). Cancers that have the most mutations are the ones that you would expect. Melanoma… sunlight exposure. Lung cancer… smoking. And colorectal cancer… microsatellite unstable. If you look at the cancers that are responding to new diverse modes of immunotherapy… it’s these ones right there (points to chart). Almost universally.

So where is GBM? Somewhere in the middle. There are a variety of these cancers which have a high number of mutations. And I think they’ve figured out that about ten mutations per megabase will generate one hundred and fifty putative neoantigens.

So there’s a population of GBM that might be… and you could identify it… using this prediction.

Here's a link to a synopsis of an article published in Science back in May 2015 that seems relevant to these past few paragraphs of Dr. Prins' presentation. You have to have a subscription to view the entire abstract.

A dendritic cell vaccine increases the breadth and diversity of melanoma neoantigen-specific T cells
Giving antitumor T cells a boost

Mutations allow tumors to divide, escape death, and resist treatment. But mutations can also cause tumors to express mutant proteins, which could potentially be exploited to drive antitumor T cell responses. Carreno et al. report the results of a small phase I trial seeking to do just this (see the Perspective by Delamarre et al.). They vaccinated three patients with advanced melanoma with personalized dendritic cell–based vaccines designed to activate T cells specific for mutations in the patients' cancer. T cells specific for mutant peptides did indeed expand. A next step will be to determine whether this promising strategy improves patient outcomes.


T cell immunity directed against tumor-encoded amino acid substitutions occurs in some melanoma patients. This implicates missense mutations as a source of patient-specific neoantigens. However, a systematic evaluation of these putative neoantigens as targets of antitumor immunity is lacking. Moreover, it remains unknown whether vaccination can augment such responses. We found that a dendritic cell vaccine led to an increase in naturally occurring neoantigen-specific immunity and revealed previously undetected human leukocyte antigen (HLA) class I–restricted neoantigens in patients with advanced melanoma. The presentation of neoantigens by HLA-A*02:01 in human melanoma was confirmed by mass spectrometry. Vaccination promoted a diverse neoantigen-specific T cell receptor (TCR) repertoire in terms of both TCR-ß usage and clonal composition. Our results demonstrate that vaccination directed at tumor-encoded amino acid substitutions broadens the antigenic breadth and clonal diversity of antitumor immunity.

And finally, here is the rest of the transcription of Dr. Prins' presentation...

Why is it that neoantigens would be better immune targets? Well for one thing, it’s back to immunology. When a T cell develops in the thymus, self antigens induce tolerance. So if you have self antigens that are over-expressed on a melanoma, the affinity of that T-cell receptor for that antigen is low. And this is why viruses… you have really high affinity because they never saw that tolerance during development in the thymus. So new mutations that come up in cancer, cancer cells, are foreign. And they look like a virus. So the effectiveness of a T cell recognizing a neoantigen is much more avid. And the issue here is that with over-expressed antigens on tumor cells, you get a lot more off target toxicity. So if you do adoptive transfer, like in melanoma, which is doing the rounds right now… adoptive transfer of melanoma-specific T cells into patients with progressively growing metastatic melanoma, a lot of them recognize pigment-synthesis proteins, gp100 tyrosinase… and one of the off-target toxicity is autoimmune vitiligo. T cells are targeting tumor cells, but they’re also targeting normal cells that have pigment proteins. You get depigmentation, you get vitiligo. So the off-target toxicity is much higher with self antigens, not with neoantigens.

Is there evidence for this proof in patients? Certainly. There’s new exome analysis. Ton Schumaker is a guy in the Netherlands who first coupled tumor exome analysis with the identification of neoantigens that could be recognized by T cells and… this was done in melanoma… but he could isolate tumor cells, identify tumor specific mutations, predict these epitopes, grow out infiltrating tumor cells, and screen to see which of these mutations you are doing.

So with UCLA and the Brain Tumor Program, every tumor that gets operated on, we create a xenograft, a patient-derived xenograft, and we grow out their tumor specific T cells and culture. Screening with exome, RNA seq, and we grow out T cells. And we’re actually sequencing the T cell repertoire of every T cell expanded culture to start cloning T cells and their ?.

So, one of the other things is how can we do this in mouse models? Using our mouse glioma model, we actually did RNA seq, and whole exome sequencing on a GL261, which is just a murine glioma line. We found a whole set of mutations, we made predictions, we found which ones were expressed and which ones could be verified. And so in this line, we found eight mutations… and this is actually one of the mutations where you can see that the amino acid change right here actually creates an affinity of a nanomolar with a T cell receptor. That’s a strong binder, and it tells you which MHC class it actually aligns with.

And this is actually a group of antigens (slide shows neoantigens) that we found based on the mutations that create epitopes that have strong binding. And when you vaccinate with tumor lysate pulsed dendritic cells, you can actually find T cells that are specific to some of these antigens. And in particular, one that we pulled out is actually known to be a mutated antigen (shows GARC-1 peptide-pulsed DC Vaccination) in glioma in this line.

So, we began to do this in patient samples. Obviously, the next step is can you do this, and can you do this in a relatively quick fashion? Can patients with tumor lysate pulsed dendritic cells… can you start figuring out what’s their mutations? And if you’re vaccinating with tumor lysate on dendritic cells, are any of these T cells that you primed recognizing neoantigens? And… we’re in the middle of this. So… I will let you know in a year.

So I think that conclusions are that I think immunotherapy is an exciting new field. It may likely be relevant for glioblastoma in the near future… although there are a lot of ongoing clinical trials going right now.

Not all glioblastomas are likely to be sensitive. I think there are some subtypes that are more likely to respond to an immune-based therapy, and we’ve got to learn how to predict.

Some of these patients are likely to have incomplete tumor resections from the clinical side. (RK did made note of this many times) This is hard to treat because of the adaptive immune resistance that develops.

And combinatorial strategies are probably likely going to be important.

The identification of patient-specific neoantigens, I’m sure is going to be relevant, but the ability to do it in a straight forward fashion where you can do it and make a difference for a patients is really what the future is going to hold.

So with that, it’s a large group, but it’s a good group, and we all work together, and I think that’s part of the thing.
(Northwest Biotherapeutics - Marnix Bosch is on the list).

You need, to do work like this, you need basic science people. You need surgeons, you need oncologists, you need post docs and funding.

Thank you very much.

I think that Dr. Prins' conclusions offer us a glimpse as to what is might be involved in the P3 from behind the scenes, as well as and will be happening in the near future. It's obvious he believes immunotherapy will be relevant for GBM in the near future. And as many of us have somewhat figured out here, that while L may be relevant for some patients in the near future (perhaps mesenchymal, pseudo progressors), it may not be as relevant, or at all relevant for all GBM patients. And for those patients, these academics are hoping that a combination trial will make it relevant for them as well.

And finally, targeting the patient-specific neoantigens, and using a dendritic cell vaccine to deliver them will possibly ultimately prove to go further than simply extending life for these GBM patients, it may possibly make them immune to it's return. And who can manufacture a tumor lysate pulsed dendritic cell vaccine in significant quantities?

Why NWBO (along with their pal Cognate).

Hopefully we will be given... sooner rather than later... more than a glimpse of what's going on. In the meantime, you may want to consider buying at these amazingly low share prices while you still can.


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