Category Archives: Companies – stock symbols

Enumeral update – guest post by Cokey Nguyen, VP, R&D

Paul’s introduction:  Enumeral has been sending ’round some interesting updates to several of their programs and I asked for some more detail. Below is a quick primer sent along by Cokey Nguyen. More detail is available in Enumeral’s recent 8K filings, including one that dropped this morning. Also the company will present this and other work at the AACR Tumor Microenvironment Meeting in January (http://www.aacr.org/Meetings/Pages/MeetingDetail.aspx?EventItemID=73#.VlyGS7_QO2k - see below).

New data from Enumeral, by Cokey Nguyen

PD-1 biology in human lung cancer is an active area of research, as these cancers have shown PD-1 blockade responsiveness in clinical trials.  Enumeral has a drug discovery effort aimed at generating novel anti-PD-1 antibodies to develop into potential therapeutic candidates.  Using a proprietary antibody discovery platform, two classes of PD-1 antagonist antibodies were discovered:  the canonical anti-PD-1 antibody which blocks PD-L1/PD-1 interactions and a second class of antibody which is non-competitive with PD-L1 binding to PD-1.  These antibodies were validated first in a pre-clinical model of NSCLC using NSG mice with a humanized immune system and a patient derived NSCLC xenograft (huNSG/PDX) (Figure 1).  Here either class of antibody demonstrated activity on par with pembrolizumab, confirming that PD-1 blockade can slow tumor growth.

Figure 1

Figure 1

In order to confirm these pre-clinical findings, Enumeral began proof of concept studies with NSCLC samples.  The first question was if resident TILs, as found in tumors, could be reinvigorated (Paukken and Wherry, 2015) or if PD-1 blockade is mainly a phenomenon that affects lymph node-specific T cells that have yet to traffic to the tumor.  In these studies, Enumeral found PD-1 blockade can, in fact, increase effector T cell function, as readout by IFNg, IL-12, TNFa and IL-6.  In addition, in a NSCLC sample that showed PD-1hi/TIM-3lo expression, PD-1 blockade strongly upregulated TIM-3 expression (~5% to ~30%, see Figure 2).

Figure 2

Screen Shot 2015-12-01 at 6.07.24 AM

In these NSCLC-based studies, it was also found that an anti-PD-1 antibody (C8) which does not bind to PD-1 in the same manner as nivolumab or pembrolizumab (PD-L1 binding site) displays differentiated biology:  increased IFNg production and significantly higher levels of IL-12 in these bulk (dissociated) tumor cultures (Figure 3).  As IL-12 is thought to be a myeloid derived cytokine, this mechanism of action is not yet well understood, but has been now observed in multiple NSCLC samples as well as in MLR assays.

Figure 3

Screen Shot 2015-12-01 at 6.08.35 AM

In these NSCLC studies, while a subset of patient samples demonstrates PD-1 blockade responsiveness, the co-expression of TIM-3 on NSCLC TILs suggests this is a validated path forward to increase the response rate in lung cancer.  As with the PD-1 program, armed with a substantial portfolio of diverse anti-TIM-3 binders, Enumeral is actively testing single and dual checkpoint blockade on primary human lung cancer samples.

Look for the companies 2 posters at AACR/TME in January

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The Tumor Ecosystem: some thoughts stirred up at the NY International Immunotherapy meeting

Ecosystems in tumor immunity

The buzzword ‘ecosystem’ has popped like a spring dandelion, and it is now used everywhere in biotech. I’m as guilty as anyone of rapid adoption: the term does capture essential elements of modern biomedical science. Complex and interlaced, with key control nodes at work at all levels – scientific, financial, clinical, commercial – and also dynamic, constantly driving adaptation, and, we hope, innovation. Scientifically the ecosystem connections are easily spotted. CRISPR technology appears in cellular therapies including TCRs and CAR-Ts as we simultaneously learn that the mechanisms of immune checkpoint suppression deployed by tumor cells can derail genetically engineered CAR T cells as readily as normal T cells. Further, those genetically engineered CAR T cells and TCRs owe their existence in large measure to our newly developed ability to sequence tumors at the individual level, with great sensitivity, to identify novel targets. The whole enterprise in turn requires ever faster, cheaper, smaller and more reliable equipment (RNA spin columns and PCR cyclers and cloning kits and desktop sequencers and on and on) and software to handle the data. Enterprises like these in turn drive discovery and innovation.

Within the tumor is another ecosystem – the tumor microenvironment or TME. While TME is a fine term it does blur the notion that this microenvironment is in nearly all cases part of a larger environment and not a walled-off terrarium (perhaps primary pancreatic cancer is an exception, within its fibrous fortress). The tumor ecosystem is a more encompassing term, allowing for the ebb and flow of vastly different elements: waves of immune cells attempting attack, dead zones of necrotic tissue being remodeled, tendrils of newly forming blood vessels, a fog of lactate, a drizzle of adenosine, energy, builders, destroyers, progenitors, phagocytes, parasites, predators. When viewed this way we might wonder how any single drug could treat a tumor, since it is not a singular thing that we attack with a drug, but an ever-changing world we are seeking to destroy.

So it’s hard to do.

Our understanding of the tumor as a complex entity was first informed by pathology, then microscopy, then histology and immunohistochemistry, myriad other techniques and of course genetics, the latter leading to the identification of tumor oncogenes, tumor epigenetics, tumor mutations (referred to above) etc, etc. This ecosystem – that of the cell and it’s mutational hardware and software (genome and exome, or genotype and phenotype) we can hardly claim to understand at all, not matter how many arrows we might draw on a figure for a paper or a review. A few recent examples: we think that tumor cells adapt to immune infiltration in part by engaging CTLA4 expressed on T cells, and when that fails they secrete IDO1, or express PD-L1 on their cell surface, or the tumor cells direct tumor associated cells to do the work for them – maybe monocytes, or macrophages, perhaps fibroblasts, perhaps the endothelium, i.e. the ecosystem. As we know from studying patterns of response to PD-1 and PD-L1 therapeutics, it is hardly so simple, as patients who don’t express the therapeutic target will respond to therapy and patients who express the therapeutic target sometimes, in fact often, will not respond. Which just says we don’t know what we don’t know, but we’ll learn, the hard way, in clinical trials.

The abundance of therapeutic targets and our lack of knowledge is best displayed, with some irony, when we try to show what we do know, as in this figure from our recent paper on immune therapeutic targets:

 Screen Shot 2015-10-07 at 4.29.43 PM

from http://www.nature.com/nrd/journal/v14/n8/full/nrd4591.html 

The picture is static, and fails to represent or visualize complexity (spatial, temporal, random, quantum), and we therefore cannot formulate meaningful hypotheses from the representation. Without meaningful hypotheses we just have observations. With observations we can only flail away hopefully, and be happy when we are right 15 or 20% of the time, as is the case with most PD-1 and PD-L1-directed immune therapeutics in most tumor indications, at least as monotherapies. Why focus so on the PD-1 pathway? Because at least for now, it is the singular benchmark immune therapeutic, stunning really in inducing anti-tumor immunity in subsets of cancer patients.

The success of the “PD-1″ franchise has created another ecosystem, clinical and commercial. The key approved drugs, and the 3 or 4 moving quickly toward approval, are held by some of the world’s largest drug companies (BMS, Merck, Astra Zeneca, Sanofi, Pfizer, Roche). Playing in that sandbox has proven very lucrative for some small companies, and very difficult for many others. There is competition for resources, for patients, for assets and ideas. This has created new niches in the commercial ecosystem, as companies try to differentiate from each other and carve out their own turf – Eli Lilly for example has focused on TME targets, distinguishing itself from other oncology pharmaceutical companies in choice of targets, followed closely of course by smaller contenders – Jounce, with a T cell program directed at ICOS but perhaps more buzz around their macrophage targeting programs, and Surface, whose targets are kept subterranean for now. Tesaro and others are betting on anti-PD-1 antibodies paired rationally with antibodies to second targets in bispecific format. Enumeral is focused on building rationale for specific combinations of immune therapeutics in specific indications, perhaps even for the right subset of patients within that indication. And so on.

It’s complicated.

Lets imagine you are right now pondering an interesting idea, have a small stake, and want to engage this landscape of shifting ecosystems. What might you do?

Lets start with a novel target. You’ve read some papers, woven together some interesting ideas, formulated some useful hypotheses. The protein has been around, maybe there are patents, but not in the immune oncology space, so you think you might have some freedom to operate. Good, best of both worlds. You dig around, find you can buy your target as purified protein, or find a cell line that expresses the target. Now what? Maybe you would hire an Adimab or Morphosys or X-Body to perform an antibody screen. Different companies, varied technologies, but all directed at antibody discovery. My favorite of this group was X-Body, who had an extraordinary platform to screen human antibody sequences and produce antibodies with really stunning activity and diversity. Juno bought them in early 2015, seeking the antibody platform and a TCR screening platform built with the same technology. I hadn’t seen anything quite so powerful until recently, with the introduction of a novel screening technology from Vaccinex. This platform is about as diverse as the X-Body platform (i.e. ~108 Vh sequences and up to 106 Vl sequences; that’s a lot of possible Vh-Vl pairs). What sets them apart is that the entire selection process happens as full length IgG in mammalian cells rather than surrogates like bacteria or yeast.  The net result is a reduction in risk associated with manufacturing.  They’ve used it to power their own clinical programs and have selection deals with some big names including Five Prime Therapeutics. Remarkably (I think) you can access their platform to screen targets for your own, i.e. external, use. Their website explains the platform further (http://www.vaccinex.com/activmab/) but here is one nice sample of their work on FZD4 (a nice target by the way):

 Screen Shot 2015-10-07 at 4.18.17 PM

So now via Vaccinex or someone else you’ve acquired a panel of antibodies that you are ready to test for immune modulatory activity in models that are relevant to immune oncology. You can build out a lab (expensive, time-consuming), find a collaborator with a lab, or find a skilled CRO. The immune checkpoint space was until recently devoid of really focused CRO activity, that is, having diverse modelling capability and careful benchmarking. However, Aquila BioMedical in Scotland, UK placed a solid bet on developing these capabilities around a year ago, and that effort is yielding a terrific suite of assays in both mouse and human cell systems, with multiple readouts, solid benchmarking (e.g. to nivolumab) and careful controls. I like this very much, rich in functional data in a way that a binding assay simply can’t reproduce. Aquila BioMedical seeks to become a driving force in this area, and I like their chances very much: see http://www.aquila-bm.com/research-development/immuno-oncology/ for more information on assays like this IFNgamma secretion assay:

 Screen Shot 2015-10-07 at 4.40.04 PM

Those are clean and robust data.

Now you come to the point of translation to actual use, that is, targeting an indication. How does one proceed? We can probe the TCGA and other databanks for clues, stare at the IHC data online (not recommended), try to cobble together enough samples to do our own analyses (highly recommended but difficult). The goal is to make some educated guesses about two distinct features of the tumor ecosystem: First, is your target expressed on a relevant cell within the ecosystem (tumor, TME, vasculature, draining lymph nodes, etc) in a specific indication or indications, and second, is that ecosystem likely to respond in a clinically meaningful way to manipulation of your target with your antibody?

That second question is a troubling one. What we are really asking is that we deconstruct the ecosystem and look for clues as to how the therapeutic might impact that ecosystem. What are we looking for during deconstruction? Several things, and they are assessed using diverse techniques, adding to the challenge. First, a highly mutated tumor is more likely to respond to immune therapy, and there are several aspects to these phenomena. One is to understand the underlying genomic changes underpinning the oncogenetics of the tumor: what is driving its ability to outcompete the natural surroundings – in our ecosystem analogy perhaps the tumor can be considered starting out life as an invasive species. Genomic sequencing can accurately identify the mutations that support the tumor, but also a potentially vast array of “passenger” mutations that accumulate when tumors turn off the usual mutation repair machinery. Various algorithms exists that can predict which mutated proteins may be immunogenic, that is, capable of stimulating an anti-tumor immune response. Another method designed to determine if an immune response has in fact be stimulated (and has stalled) is to sequence the mRNA expressed in the tumor: exome sequencing. This will reveal, among other things, what the TCR usage is within the tumor, and that in turn will inform you if there is a very narrow anti-tumor response and a broad one, based on the breadth of TCR clonality. That sounds complex, but really isn’t – suffice to say that a broader TCR response in suggestive of immune potential, leashed T cells awaiting clear orders to attack.

More complex is the nature of those orders, and counter-orders. Various methods are being developed to measure the “quality” of the immune response that confronts the tumor. Are key costimulatory molecules present on T cells that would allow stimulation? Are the T cells instead coated with immunosuppressive receptors? Are the tumor cells masked with inhibitory proteins, are they secreting immunosuppressive factors, have they hidden themselves from immune view by downregulating the proteins that T cells “see” (i.e. the MHC complex). What are the cells within the TME doing? Are they monocytes, macrophages, fibroblasts? Where are the T cells? Within the tumor, or shunted off to the side, at the margin between the tumor and normal tissue? Are NK cells present? And on and on it goes. It seems impossible to answer all these diverse questions.

You might try IHC, as mentioned, or targeted PCR for select genes, and Flow Cytometry to look at the distribution of proteins on various cells, or try deep sequencing. All of this is achievable with equipment, labs and people, or by assembling various collaborators, but all in all, quite a challenge. Very recently an interesting company called MedGenome came to my attention, offering a diverse range of services, starting with neo-epitope prioritization and immune response analyses. These offerings, plus some routine IHC, should give most researchers a comprehensive look into tumor ecosystems, informing indication selection, mechanism of action studies and patient profiling. They explain the technology at http://medgenome.com/oncomd/. This is a schematic they sent me showing their neoepitope prioritization scheme that enriches for peptides that trigger anti-tumor immunity, e.g. in a vaccine setting or perhaps in a cellular therapeutic format.

 Screen Shot 2015-10-07 at 4.22.16 PM

It’s a good start on democratizing a suite of assays typically available only to specialty academic labs and well-funded biotechs and pharma companies.

So now you’ve gotten your antibodies (Vaccinex), performed critical in vitro (and soon, in vivo) assays (Aquila Biomedical), and analyzed the tumor immune ecosystem for indication mapping (Medgenome).

You’ll have spent some money but moved quickly and confidently forward with your preclinical development program. Your seed stake is diminished though, and it’s time to raise real money. Now what? … now you face the financial/clinical/commercial ecosystem.

stay tuned.

The Tumor Microenvironment “Big Tent” series continues (part 4)

 

The Tumor Microenvironment (TME) series to date is assembled here http://www.sugarconebiotech.com/?s=big+tent containing parts 1-3

I’m happy to point you to the most recent content, posted on Slideshare: http://www.slideshare.net/PaulDRennert/im-vacs-2015-rennert-v2

In this deck I review the challenges of the TME particularly with reference to Pancreatic and Ovarian cancers. A few targets are shown below.

Feedback most welcome.

Screen Shot 2015-08-27 at 7.20.21 AM

 

Brodalumab for Psoriasis – what a mess

Let’s agree that the headline “Suicide Stunner” – penned by John Carroll for FierceBiotech – can never auger anything but very bad news, and never more so then when it is used to describe clinical trial results. Released on the Friday before the long US holiday weekend, bookended to the announcement of positive news on it’s PSCK9 program, Amgen stated that it was walking away from an expensive co-development program with AstraZeneca, basically washing it’s hands of the anti-IL-17 receptor (IL-17R) antibody brodalumab because of suicidal tendencies and actual suicides that occurred in the Phase 3 psoriasis trials. Brodalumab is under development for the treatment of plaque psoriasis, psoriatic arthritis and axial spondyloarthritis. Amgen stated that they believed that the approval label for brodalumab would contain warning language regarding suicide risk, and this would limit the success of the drug. By using such language while pulling the plug Amgen has essentially put AstraZeneca in the position of having to prove to the FDA that there is no suicide risk.

Holy crap.

Note here that we are not talking about a psychiatric drug, where the risk of suicide might be the consequence of trying to re-align an aberrant central nervous system. Instead we are talking about a drug that targets autoimmune disorders by blocking the action of T cells. This is not a biology linked to psychiatric health, at least not as we understand it today (more on this later).

Backing up: in April 2012, AstraZeneca and Amgen announced a collaboration to jointly develop and commercialize five clinical-stage monoclonal antibodies from Amgen’s inflammation portfolio: AMG 139, AMG 157, AMG 181, AMG 557 and brodalumab (aka AMG 827). The drivers for the collaboration were Amgen’s biologics expertise, the strong respiratory, inflammation and asthma development expertise of MedImmune (AstraZeneca’s biologics division), AstraZeneca’s global commercial reach in respiratory and gastrointestinal diseases, and the shared resources of two experienced R&D organizations

Under the terms of the agreement, AstraZeneca paid Amgen a $50MM upfront payment and the companies shared development costs. The breakout was as follows: AstraZeneca was responsible for approximately 65 percent of costs for the 2012-2014 period, and the companies now split costs equally. Amgen was to book sales globally and retain a low single-digit royalty for brodalumab. Amgen retained a mid single-digit royalty for the rest of the portfolio with remaining profits to be shared equally between the partners.

It gets even more complicated. Amgen was to lead the development and commercialization of brodalumab (and AMG 557, see below). Amgen was to assume promotion responsibility for brodalumab in dermatology indications in North America, and in rheumatology in North America and Europe. AstraZeneca was to assume promotion responsibility in respiratory and dermatology indications ex-North America. AstraZeneca remains responsible for leading the development and commercialization of AMG 139, AMG 157 and AMG 181. We’ll touch on these other antibodies at the very end.

Back to brodalumab. On balance, Amgen was on the hook for the development and commercialization costs, direct, indirect and ongoing, for dermatology indications in the US and also rheumatology, which in this case refers to psoriatic arthritis and axial spondyloarthritis. On the other hand, AstraZeneca was on the hook for commercialization in respiratory indications worldwide, and dermatology ex-US. This is interesting because brodalumab failed in its’ respiratory indication, moderate to severe asthma, and failed late, in a Phase 2b patient subset trial. So, on balance, much of the overall development cost seems to have shifted back onto Amgen over time (this is not to say that the companies would not have changed terms mid-term, they may have).

Two weeks ago I chaired a session on “Biologics for Autoimmune Disease” at the PEGS conference on Boston. In my opening remarks I used psoriasis as an example of an indication in which we were making clear and important progress, including with IL-17-directed therapeutics. Indeed, psoriasis is now a “crowded” indication commercially, with antibodies and receptor fusion proteins targeting the TNFs, IL-6, IL-12, IL-17, and IL-23 pathways all showing at least some activity. Notably, IL-17 and IL-23 targeting drugs appear to offer the greatest benefit in clearing psoriatic plaques. These pathways intersect in myriad ways, not all of which are well understood. This cartoon shows the effector cytokines and the receptors are expressed by diverse cell types, including dendritic cells, macrophages, T cells, and keratinocytes in the dermis.

IL-17 and friends

In simplistic terms, IL-6 triggers IL-12 and IL-23, and IL-23 triggers IL-17. As mentioned, the IL-17 and IL-23 targeting agents have great efficacy in psoriasis. Amgen and AstraZeneca were preparing an NDA (new drug application) for FDA submission based on results from three large Phase 3 studies. Here are the listed Phase 3 programs for brodalumab:

broda 1

I suppose those Phase 3 studies in psoriatic arthritis will now be tabled or transferred to AstraZeneca. For the sake of completeness here are the earlier studies:

broda 2

Certainly the clinical program was a robust one. So, what went wrong? Amgen R&D head Sean Harper summed up Amgen’s thinking about the suicide issue in the press release: “During our preparation process for regulatory submissions, we came to believe that labeling requirements likely would limit the appropriate patient population for brodalumab.”

The news aggregator and commentary website UpdatesPlus had this to add, questioning whether this result was “bad luck, bad target or victim of brodalumab’s efficacy: Despite high efficacy in Phase 3 studies, whispers of suicidality associated with brodalumab started to emerge at AAD.  At the time Amgen suggested this was related to disease however the company refused to comment on total rates and whether events were seen across arms … The question is whether Amgen is being hyper-cautious or whether the risk of suicidality is especially concerning.  Questions also emerge around the cause of risk – is this a spurious cluster of events unrelated to brodalumab; is suicidality perhaps related to relapse from the excellent efficacy associated with brodalumab after withdrawal (remember most patients exhibited at least PASI 90 on treatment but durability was very poor upon withdrawal); or perhaps suicidality is related to blocking the IL-17RA (note that suicidality has not to our knowledge been reported for the IL-17A ligand mAb Cosentyx) … One final point is whether regulators will now reevaluate suicide risk of IL-17 related molecules as a class – much greater clarity of brodalumab data is required to make a judgement.” That’s quite a nice summary from UpdatesPlus.

FierceBiotech’s report added “AstraZeneca would face some stiff competition if it decides to move forward solo on the drug. Novartis is already well in front with its IL-17 program for secukinumab, approved in January as Cosentyx. Eli Lilly has also been racking up positive late-stage studies for its IL-17-blocking ixekizumab, trailed by Merck’s MK-3222 and Johnson & Johnson’s IL-23 inhibitor guselkumab.”

Still, brodalumab demonstrated remarkable efficacy in psoriasis – Amgen and AstraZeneca went so for as to include a PASI100 score in one of their trials, meaning 100% clearance of psoriatic plaques, and the drug would have shown well against the best of breed, which today is likely Novartis’ anti-IL-17 antibody secukinumab. It is crowded space however, with antagonists targeting multiple nodes in the IL-17/IL-23 axis, alongside the biologics mentioned earlier.

Here is the current landscape from CiteLine (including brodalumab):

CiteLine

All in all, a tough crowd, and one that Amgen likely felt it could not face with a compromised label.

Let’s go back to the question posed above: bad luck, bad target or victim of superior efficacy? “Bad luck” suggests a statistical fluke in the data, potentially caused by the generally higher rates of suicidal tendencies observed in the moderate to severe psoriasis patient population. “Victim of superior efficacy” is in a sense a related issue, since the suggestion is that the loss of responsiveness to the drug, or a relapse, triggers a suicidal response as plaques return. Neither of these statements is really formulated as a hypothesis, and it doesn’t matter, as we don’t have the actual trial data yet with which to perform hypothesis testing.

“Bad target” is the most worrisome suggestion, and this can be formulated as a hypothesis, formally, the null hypothesis is that targeting the IL-17 receptor does not cause suicidal tendencies. Unfortunately, we still can’t test the hypothesis, and it seems likely that having the actual data won’t really help, that is, the study is probably not powered to reject that particular null hypothesis. So, what do we know? A few things, as it turns out.

First is that a link between the immune system and the nervous system is well established, although much of the focus has been on the role of neuronal enervation on immune responses. But clinically at least, the picture is muddier than that. High dose IL-2 can cause neurotoxicity, even hallucinations, according to Dr. Kathleen Mahoney, an oncologist at Beth Israel Deaconess and the Dana Farber. But what is really interesting is what else happens: “Some IL-2 treated patients can have odd dreams, really crazy dreams, and they last for weeks after treatment, long past the time when IL-2 would still be present in the body”, Dr. Mahoney said. Interferon alpha therapy is associated with pathological (severe) fatigue and also depressive symptoms that develop after 4–8 weeks of treatment. Of note, preventive treatment with anti-depressants, in particular serotonin reuptake inhibition attenuates IFN-alpha-associated symptoms of depression, anxiety, and neurotoxicity. Some researchers have suggested (controversially) that anti-TNF antibodies can control depression. Such anecdotal clinical observations suggest that we really do not yet understand the immune system connection to CNS activity.

On the other hand, antagonism of cytokine activity, and particularly of the cytokines IL-6, IL-17 and IL-23, has not been associated with neurological symptoms. For example the anti-IL-6 receptor antibody tocilizumab has shown a positive impact in rheumatoid arthritis patients quality of life scoring, which includes fatigue, anxiety, depression and a number of other factors. More to the point, the anti-IL-17 antibody secukinumab, that targets the IL-17 ligand (rather than the receptor), has not shown a link to suicide.

Clearly more data are needed, and it would not be surprising if the FDA began a drug class review if the data in the brodalumab trials warrant. They could cast quite a wide net given the complexity of this pathway, which overlaps with IL-6, IL-12 and IL-23. This casts a pall over the dermatology and particularly the rheumatology landscape, which is really waiting for novel therapeutics to move them successfully into new and important indications such as lupus and Type-1 Diabetes. The IL-17/IL-23 axis was to be that next great hope, and with luck we will still see these drugs moving out of their core indications of psoriasis and inflammatory bowel disease into new indications.

One last thing.

Those other antibodies – where are they now? A quick scorecard:

snapshot

It is readily seen that none of these are beyond early Phase 2, so it’s fair to say that the rest of the Amgen/AstraZeneca partnership has a long way to go. I, for one, wish the ongoing collaboration the very best of luck, particularly in the lupus indications, where we can really use some good news.

stay tuned.

Celgene and friends…

The ever-nimble company Celgene (NASDAQ: CELG) was back in the news last week, signing a sweetheart deal with AstraZeneca (NYSE: AZN) that brings access to a Phase III immune checkpoint therapeutic.

The deal between Celgene and Astra Zeneca is remarkable for balancing the relative strengths and weaknesses of each company. For AZN the deal enhances the competitive reach of the anti-PD-L1 mAb MEDI4736, now backed by a rich war chest and the potential for combination therapy with Celgene’s myeloma and hematologic malignancy portfolio. Notably, these diseases have remained relatively indifferent to monotherapy with immune checkpoint therapeutics, with a few exceptions. Refractory multiple myeloma, an indication that Celgene dominates, is particularly resistant to monotherapy with immune checkpoint therapeutics and the bet is that efficacy will be seen when MEDI4736 is paired with Celgene’s approved drugs lenalidomide and pomalidomide, among others. The deal may also ultimately bring access to first line solid tumor patients in the form of a MEDI4736 combination with Celgene’s Abraxane, a synergy that has been overlooked I think.

For Celgene this is an overdue move into the immunotherapy space and reflects their willingness to spend their way into contention and expand market dominance from multiple myeloma into other hematological malignancies, a counter of sorts to Abbvie’s buyout of Pharmacyclics and it’s B cell cancer blockbuster Imbruvica. Celgene has already made forays into the immuno-oncology space with it’s in-licensing of Inhibrx’ anti-CD47 antibody and the deal with VentiRx and Array Biopharma to develop VTX-2337, a TLR8 agonist but these are much earlier stage assets. It is reasonable to predict that Celgene will also move quickly to acquire additional assets in the immune checkpoint space.

I’d expect to see both AZN and Celgene aggressively pursue additional deals. AZN did exactly that with Juno Therapeutics (combining CAR T and anti-PD-L1 therapies) and Innate Pharma in separate deals two weeks ago. It is interesting to speculate that there is additional synergy between the Innate Pharma programs and the Celgene programs that could be explored later on.

More importantly I think, and looking ahead, both AZN and Celgene are building multiplatform immuno-oncology companies, with cellular therapeutics (CAR-T and TCR), antibody therapies, targeted therapeutics, and immune checkpoint therapeutics – a broad reach across the evolving oncology clinical landscape, similar to the position Novartis has built for itself. Both AZN and Celgene floated that their deal could grow into a larger collaboration, if so, this means that similar deals in this space will have to become bigger and broader just to keep up. Merck and Pfizer’s recently announced collaboration is a good example of a deal not quite juicy enough to be transformative in the way the AZN/Celgene hookup may be for both of these companies. Novartis recently stated that they are looking for acquisitions in the 2-5 billion dollar range – this gives us a sense of scale required. We are entering a phase of “go big or go home” and the winners will dominate oncology clinical care.

Some Adjacencies in Immuno-oncology

Some thoughts to fill the space between AACR and ASCO (and the attendant frenzied biopharma/biotech IO deals).

Classical immune responses are composed of both innate and adaptive arms that coordinate to drive productive immunity, immunological expansion, persistence and resolution, and in some cases, immunological memory. The differences depend on the “quality” of the immune response, in the sense that the immunity is influenced by different cell types, cytokines, growth factors and other mediators, all of which utilize diverse intracellular signaling cascades to (usually) coordinate and control the immune response. Examples of dysregulated immune responses include autoimmunity, chronic inflammation, and ineffective immunity. The latter underlies the failure of the immune system to identify and destroy tumor cells.

Let’s look at an immune response as seen by an immunologist, in this case to a viral infection:

 immune viral

Of note are the wide variety of cell types involved, a requirement for MHC class I and II responses, the presence of antibodies, the potential role of the complement cascade, direct lysis by NK cells, and the potentially complex roles played by macrophages and other myeloid cells.

In the immune checkpoint field we have seen the impact of very specific signals on the ability of the T cell immune response to remain productive. Thus, the protein CTLA4 serves to blunt de novo responses to (in this case) tumor antigens, while the protein PD-1 serves to halt ongoing immune responses by restricting B cell expansion in the secondary lymphoid organs (spleen, lymph nodes and Peyer’s Patches) and by restricting T cell activity at the site of the immune response, thus, in the tumor itself. Approved and late stage drugs in the immune checkpoint space are those that target the CTLA4 and PD-1 pathways, as has been reviewed ad nauseum. Since CTLA4 and PD-1 block T cell-mediated immune responses at different stages it is not surprising that they have additive or synergistic activity when both are targeted. Immune checkpoint combinations have been extensively reviewed as well.

We’ll not review those subjects again today.

If we step back from those approved drugs and look at other pathways, it is helpful to look for hints that we can reset a productive immune response by reengaging the innate and adaptive immune systems, perhaps by targeting the diverse cell types and/or pathways alluded to above.

One source of productive intelligence comes from the immune checkpoint field itself, and its’ never-ending quest to uncover new pathways that control immune responses. Indeed, entire companies are built on the promise of yet to be appreciated signals that modify immunity: Compugen may be the best known of these. It is fair to say however that we remain unclear how best to use the portfolio of checkpoint modulators we already have in hand, so perhaps we can look for hints there to start.

New targets to sift through include the activating TNF receptor (TNFR) family proteins, notably 4-1BB, OX40, and GITR; also CD40, CD27, TNFRSF25, HVEM and others. As discussed in earlier posts this is a tricky field, and antibodies to these receptors have to be made just so, otherwise they will have the capacity to signal aberrantly either because the bind to the wrong epitope, or they mediate inappropriate Fc-receptor engagement (more on FcRs later). At Biogen we showed many years ago that “fiddling” with the properties of anti-TNFR antibodies can profoundly alter their activity, and using simplistic screens of “agonist” activity often led to drug development disaster. Other groups (Immunex, Amgen, Zymogenetics, etc) made very similar findings. Careful work is now being done in the labs of companies who have taken the time to learn such lessons, including Amgen and Roche/Genentech, but also BioNovion in Amsterdam (the step-child of Organon, the company the originally created pembrolizumab), Enumeral in Cambridge US, Pelican Therapeutics, and perhaps Celldex and GITR Inc (I’ve not studied their signaling data). Of note, GITR Inc has been quietly advancing it’s agonist anti-GITR antibody in Phase 1, having recently completed their 8th dose cohort without any signs of toxicity. Of course this won’t mean much unless they see efficacy, but that will come in the expansion cohort and in Phase 2 trials. GITR is a popular target, with a new program out of Wayne Marasco’s lab at the Dana Farber Cancer Institute licensed to Coronado and Tg Therapeutics. There are many more programs remaining in stealth for now.

More worrisome are some of the legacy antibodies that made it into the clinic at pharma companies, as the mechanisms of action of some of these agonist antibodies are perhaps less well understood. But lets for the sake of argument assume that a correctly made anti-TNFR agonist antibody panel is at hand, where would we start, and why? One obvious issue we confront is that the functions of many of these receptors overlap, while the kinetics of their expression may differ. So I’d start by creating a product profile, and work backward from there.

An ideal TNFR target would complement the immune checkpoint inhibitors, an anti-CTLA4 antibody or a PD-1 pathway antagonist, and also broaden the immune response, because, as stated above, the immune system has multiple arms and systems, and we want the most productive response to the tumor that we can generate. While cogent arguments can be made for all of the targets mentioned, at the moment 4-1BB stands as a clear frontrunner for our attention.

4-1BB is an activating receptor for not only T cells but also NK cells, and in this regard the target provides us with an opportunity to recruit NK cells to the immune response. Of note, it has been demonstrated by Ron Levy and Holbrook Khort at Stanford that engagement of activating Fc receptors on NK cells upregulates 4-1BB expression on those cells. This gives us a hint of how to productively combine antibody therapy with anti-4-1BB agonism. Stanford is already conducting such trials. Furthermore we can look to the adjacent field of CAR T therapeutics and find that CAR T constructs containing 4-1BB signaling motifs (that will engage the relevant signaling pathway) confer upon those CAR T cells persistence, longevity and T cell memory – that jewel in the crown of anti-tumor immunity that can promise a cure. 4-1BB-containing CAR T constructs developed at the University of Pennsylvania by Carl June and colleagues are the backbone of the Novartis CAR T platform. It is a stretch to claim that the artificial CAR T construct will predict similar activity for an appropriately engineered anti-4-1BB agonist antibody, but it is suggestive enough to give us some hope that we may see the innate immune system (via NK cells) and an adaptive memory immune response (via activated T cells) both engaged in controlling a tumor. Pfizer and Bristol Myers Squibb have the most advanced anti-4-1BB agonist antibody programs; we’ll see if these are indeed best-in-class therapeutics as other programs advance.

Agonism of OX40, GITR, CD27, TNFRSF25 and HVEM will also activate T cells, and some careful work has been done by Taylor Schreiber at Pelican to rank order the impact of these receptors of CD8+ T cell memory (the kind we want to attack tumors). In these studies TNFRSF25 clearly is critical to support CD8 T cell recall responses, and may provide yet another means of inducing immune memory in the tumor setting. Similar claims have been made for OX40 and CD27. Jedd Wolchok and colleagues recently reviewed the field for Clinical Cancer Research if you wish to read further.

Looking again beyond T cells another very intriguing candidate TNFR is CD40. This activating receptor is expressed on B cells, dendritic cells, macrophages and other cell types involved in immune responses – it’s ligand (CD40L) is normally expressed on activated T cells. Roche/Genentech and Pfizer have clinical stage agonist anti-CD40 programs in their immuno-oncology portfolios. Agonist anti-CD40 antibodies would be expected to activated macrophages and dendritic cells, thus increasing the expression of MHC molecules, costimulatory proteins (e.g. B7-1 and B7-2) and adhesion proteins like VCAM-1 and ICAM-1 that facilitate cell:cell interactions and promote robust immune responses.

I mentioned above that interaction of antibodies with Fc receptors modulates immune cell activity. In the case of anti-CD40 antibodies, Pfizer and Roche have made IgG2 isotype antibodies, meaning they will have only weak interaction with FcRs and will not activate the complement cascade. Thus all of the activity of the antibody should be mediated by it’s binding to CD40. Two other agonist anti-CD40 antibodies in development are weaker agonists, although it is unclear why this is so; much remains to be learned regarding the ideal epitope(s) to target and the best possible FcR engagement on human cells. Robert Vonderheide and Martin Glennie tackled this subject in a nice review in Clinical Cancer Research in 2013 and Ross Stewart from Medimmune did likewise for the Journal of ImmunoTherapy of Cancer, so I won’t go on about it here except to say that it has been hypothesized that crosslinking via FcgRIIb mediates agonist activity (in the mouse). Vonderheide has also shown that anti-CD40 antibodies can synergize with chemotherapy, likely due to the stimulation of macrophages and dendritic cells in the presence of tumor antigens. Synergy with anti-CTLA4 has been demonstrated in preclinical models.

One of the more interesting CD40 agonist antibodies recently developed comes from Alligator Biosciences of Lund, Sweden. This antibody, ADC-1013, is beautifully characterized in their published work and various posters, including selection for picomolar affinity and activity at the low pH characteristic of the tumor microenvironment (see work by Thomas Tötterman, Peter Ellmark and colleagues). In conversation the Alligator scientists have stated that the antibody signals canonically, i.e. through the expected NF-kB signaling cascade. That would be a physiologic signal and a good sign indeed that the antibody was selected appropriately. Not surprisingly, this company is in discussion with biopharma/biotech companies about partnering the program.

Given the impact of various antibody/FcR engagement on the activity of antibodies, it is worth a quick mention that Roghanian et al have just published a paper in Cancer Cell showing that antibodies designed to block the inhibitory FcR, FcgRIIB, enhance the activity of depleting antibodies such as rituximab. Thus we again highlight the importance of this sometimes overlooked feature of antibody activity. Here is their graphical abstract:

 graphical abstract

The idea is that engagement of the inhibitory FcR reduces the effectiveness of the (in this case) depleting antibody.

Ok, moving on.

Not all signaling has to be canonical to be effective, and in the case of CD40 we see this when we again turn to CAR T cells. Just to be clear, T cells do not normally express CD40, and so it is somewhat unusual to see a CAR T construct containing CD3 (that’s normal) but also CD40. We might guess that there is a novel patent strategy at work here by Bellicum, the company that is developing the CAR construct. The stated goal of having a CD40 intracellular domain is precisely to recruit NF-kB, as we just discussed for 4-1BB. Furthermore, the Bellicum CAR T construct contains a signaling domain from MYD88, and signaling molecule downstream of innate immune receptors such as the TLRs that signal via IRAK1 and IRAK4 to trigger downstream signaling via NF-kB and other pathways.

Here is Bellicum’s cartoon:

 cidecar

If we look through Bellicum’s presentations (see their website) we see that they claim increased T cell proliferation, cytokine secretion, persistence, and the development of long-term memory T cells. That’s a long detour around 4-1BB but appears very effective.

The impact of innate immune signaling via typical TLR-triggered cascades brings us to the world of pattern-recognition receptors, and an area of research explored extensively by use of TLR agonists in tumor therapy. Perhaps the most notable recent entrant in this field is the protein STING. This pathway of innate immune response led to adaptive T cell responses in a manner dependent on type I interferons, which are innate immune system cytokines. STING signals through IRF3 and TBK1, not MYD88, so it is a parallel innate response pathway. Much of the work has come out of a multi-lab effort at the University of Chicago and has stimulated great interest in a therapeutic that might be induce T cell priming and also engage innate immunity. STING agonists have been identified by the University of Chicago, Aduro Biotech, Tekmira and others; the Aduro program is already partnered with Novartis. They published very interesting data on a STING agonist formulated as a vaccine in Science Translational Medicine on April 15th (2 weeks ago). Let’s remember however that we spent several decades waiting for TLR agonists to become useful, so integration of these novel pathways may take a bit of time.

This emerging mass of data suggest that the best combinations will not necessarily be those that combine T cell immune checkpoints (anti-CTLA4 + anti-PD-1 + anti-XYZ) but rather those that combine modulators of distinct arms of the immune system. Recent moves by biopharma to secure various mediators of innate immunity (see Innate Pharma’s recent deals) and mediators of the immunosuppressive tumor microenvironment (see the IDO deals and the interest in Halozyme’s enzymatic approach) suggest that biopharma and biotech strategists are thinking along the same lines.

The twisted tale of neoantigens and anti-tumor immune responses

Two papers out this week add to a pile of data addressing the role of neoantigens in tumor therapy. While these papers address tumor neoantigen “load” in the context of immune checkpoint therapy the results have implications for TIL therapeutics, TCR therapeutics and onco-vaccine development.

A really dramatic paper from diverse groups at the University of Pennsylvania and their collaborators, just published in Nature (link-1), explores the complex interplay of radiation therapy and anti-CTLA4 antibody therapy (ipilimumab, from BMS) in patients with stage IV metastatic melanoma (relapsed or previously untreated). In this Phase 1/2 clinical trial (NCT01497808) patients with multiple melanoma metastases received various doses of radiation therapy delivered to a single metastasis, termed the “index lesion”. They then received 4 doses of ipilimumab (3 mg/kg, i.v., once every 3 weeks) and non-irradiated lesions were evaluated within 2 months of the last dose.

Although the sample size reported is small (n=22) some interesting lessons emerged from the study. The response rate was low, and the progression free survival (PFS: 3.8 months) and overall survival (OS: 10.7 months) data bear this out. It appears that just shy of 40% of patients were still alive at ~30 months (see Figure 1c in the paper). It is too early to tell if there will be a “long-tail” effect going forward. In the original ipilimumab study a very small percentage of patients lived for a very long time, “pulling” the PFS and OS curves to the right. Regardless, most patients in this study did not respond and the questions posed in this paper are directed to the mechanisms of resistance.

The mouse B16-F10 melanoma model was used to model resistance. Mice with tumors were locally irradiated then treated with an anti-mouse-CTLA4 antibody, to mimic the clinical trial. Only 17% of the treated mice responded. Two predictors of response/non-response were elucidated: 1) the ratio of effector T cells (Teff) to regulatory T cells (Treg) and 2) a gene signature in the tumor cells that is dominated by the expression of PD-L1 and IFNgamma regulated genes. In short, if the melanoma cells are expressing PD-L1 and the tumor infiltrating lymphocyte (TIL) population is dominated by Tregs (which are PD-1+), then the radiation + anti-CTLA4 therapy failed.

To further subset TIL into active Teff versus non-responsive “exhausted” Teff, the authors used an expression profile of PD-1+/Eomes+ to identify exhausted Teff and PD-1+/Eomes+/Ki67+/GzmB+ for active Teff. Importantly, exhausted Teff could be reanimated upon treatment with PD-1 pathway antagonists: anti-PD-1 antibody or anti-PD-L1 antibody. This reanimation led to an improved CD8+ Teff/Treg ratio and led to tumor control in the majority of the mice (up to 80%) when the treatment consisted of irradiation plus anti-CTLA4 plus anti-PD-L1. Of note, radiation plus anti-PD-L1 did not achieve this effect; the triple therapy was required (see Figure 2d).

The striking conclusion is that upregulation of PD-L1 on tumor cells can subvert the effect of anti-CTLA4 antibody therapy, and this therefore qualifies as a mechanism of resistance.

What about the role of irradiation? In both the patients and the mouse model irradiation was local, not systemic. Further, this local irradiation was required to achieve complete responses in the mouse model. What is going on here? Irradiation was linked to a modest increase in TIL infiltration of melanoma tumors in the mouse model, but sequencing of the T cell receptors (TCR) revealed that there was an increase in the diversity of TCRs, meaning that more antigens were being recognized and responded to by TIL after irradiation. In this context then, anti-CTLA4 reduced the Treg population, anti-PD-L1 allowed CD8+ TIL expansion, and irradiation set the antigenic landscape for response.

Returning to the patients armed with this information from the mouse study, the authors find that low PD-L1 expression on the melanoma cells correlates with productive response to irradiation plus ipilimumab therapy, while PD-L1 high expressing tumors were associated with persistent T cell exhaustion. In addition, monitoring the state of the CD8+ T cell population (PD-1+/Eomes+ versus PD-1+/Eomes+/Ki67+/GzmB+) suggested that these phenotypes might be useful as peripheral blood biomarkers. The patient numbers are very small for this analysis however, which awaits further validation.

The conclusion: irradiation combined with ipilimumab plus anti-PD-L1 antibody therapy should be a productive therapeutic combination in PD-L1+ stage IV melanoma. Similar strategies may be beneficial in other solid tumor types. This is interesting news for companies developing anti-PD-L1 antibodies, including BMS-936559 (also from BMS), MPDL3280A (Roche/Genentech), MEDI4736 (AZN) and MSB0010718C (Merck Serono).

A second paper (link) bring our focus back to PD-1, in the context of non-small cell lung cancer (NSCLC). Using the anti-PD-1 antibody pembrolizumab (from Merck) a group from the Memorial Sloan-Kettering Cancer Center sought to determine correlates of response of NSCLC patients to anti-PD-1 therapy. Their findings again hone in on neoantigen load, as the best predictors of response were the non-synonymous mutational burden of tumors, including neoantigen burden and mutations in DNA repair pathways. What all this means is that mutations that change the amino acid sequence (thus, are non-synonymous) can produce neoantigens that can be recognized by CD8+ T cells; mutations in the DNA repair pathways increase the rate that such mutations go uncorrected by a cell.

The authors sequenced the exomes (expressed exons – these encode proteins) from tumors versus normal tissue, as a measure of non-synonymous mutational burden that could produce neoantigens. Patients were subsetted based on response: those with durable clinical benefit (DCB) and those with no durable benefit (NDB). High mutational burden was correlated with clinical efficacy: DCB patients averaged 302 such mutations, while NDB patients averaged 148; ORR, PFS and OS also tracked with mutational burden. In a validation cohorts the number of non-synonymous mutations was 244 (DCB) versus 125 (NDB).

Examination of the pattern of exome mutations across both cohorts was studied in an attempt to discern a pattern of response to pembrolizumab treatment. The mutational landscape was first refined using an algorithm that predicts neoepitopes that can be expressed in the context of each patients specific class I HLA repertoire – these are the molecules that bring antigens to cell surfaces and present them to T cells for recognition (I’m simplifying this process but that is the gist of it). The algorithm identified more potential neoepitopes in the DCB patient tumors than in the NDB cohort, more impressively, a dominant T cell epitope was identified in an individual patient using a high-throughput HLA multimer screen. At the start of therapy this T cell clone represented 0.005% of peripheral blood T cells, after therapy the population had risen 8-fold, to 0.04% of peripheral blood T cells. Note that most of this clone of T cell would be found in the tumor, not in circulation, so that 8-fold increase is impressive. The T cells were defined as activated CD8+ Teff cells by expression markers: CD45RA-/CCR7-/LAG3-. As in the first paper we discussed, it is useful that these markers of systemic response to immunotherapy treatment are being developed.

There is an interesting biology at work here. It is often noted that high mutational burden is associated with better outcome, for example to chemotherapy in ovarian cancer, and irrespective of therapy across different tumor types (link-2). This suggests that tumor neoepitopes are stimulating an ongoing immune response that is stifled by active immunosuppression, yet is still beneficial. Once unleashed by immune checkpoint blockade, the immune system can rapidly expand it’s efforts.

We recently reviewed the importance of neoantigens in anti-tumor therapy (link-3) although the focus then was on cellular therapeutics rather than on immune checkpoint modifiers such as anti-CTLA4 and anti-PD-1 or PD-L1 antibodies. We can mow add that our ability to track neoantigens and the immune response to neoantigens is opening new avenues for investigating immuno-oncology therapeutics and their efficacy.

Snow Day Reading: The New Multiple Myeloma Therapeutics

There was a comment floating around Twitter that “Biotech was boring this week” and that’s true, it has been a slow news week. Sanofi took the ax to about 100 Genzyme site staffers, Bayer and J&J announced R&D reorganizations, another CAR T cell deal got done (China) and IPOs and follow-on financings were announced: business as usual.

In the background though, slow but steady therapeutic advances are being made that will impact long-term company values. The development of antibody-based therapeutics in multiple myeloma (MM) is one nice example. Among the hematologic malignancies MM is a major disease. The incidence in the US is ~30K yearly and the prevalence is ~85K. A quick glance at that math reveals a disease with pretty short-term survival, less than 5 years according a report produced by the Leukemia & Lymphoma Society in 2014.

The age of onset for MM is 70 years old in the US, and this is important because it limits some treatment options for many patients who are physically frail. Such patients may not be candidates for high-dose chemotherapy and stem cell transplantation (SCT) and even patients who are given this first line regimen will eventually relapse. Those patients are served by second line therapeutics, described below.

The huge advance is this field has been the development of non-chemotherapeutic drugs. The IMiDs such as lenalidomide and pomalidomide (Revlimidtm and Pomalysttm, both from Celgene), are used with the proteasome inhibitors such as bortezomib (Velcadetm from Takeda) or carfilzomib (Kyprolistm, from Onyx) along with steroids (dexamethasone, prednisone) in various combinations. “Triplets” are the preferred therapeutic, as exemplified by the combination of lenalidomide, bortezomib and dexamethasone.

At the ASH conference in December a large retrospective outcomes study of newly diagnosed MM patients was presented (link 1). Here is some of the data from that study:

Cohort                                                                         % Probability of 3 yr Survival

All ages (N = 1444) 63
       < 65 70
       65 to < 75 65
       ≥ 75 47
SCT
      Yes 77
      No 54
Triplet therapy
     Yes 69
     No 55
IMWG risk
     High 59
     Standard 66
     Low 76
del(17p)
     Present 53
     Absent 63

So a few things here to note: age of onset is a negative factor for survival, in part due to the inability to get the majority of elderly patients to autologous stem cell transplantation (ASCT). In addition to age of diagnosis, the International Myeloma Working Group

(IMWG) risk score is a composite of factors that determine outcome, and finally the presence of a chromosome deletion (called del(17p)) is known to be associated with significantly shortened survival.

In this study they demonstrated further that the use of triplet therapy vs. non-triplet therapy was associated with significantly prolonged OS regardless of IMWG risk but no improvement was noted for triplet vs. non-triplet therapy in patients with del(17p). Two things are clear from this study – one, we have patient subsets that remains underserved (the elderly and those patients carrying del(17p), and two, triplet therapy is keeping 70% of patients alive for at least three years.

What about patients that fail triplet therapy and who relapse and or are refractory to further treatment (rrMM)? They fare very poorly indeed, as shown here:

                               newly diagnosed                                           treatment failures 

MM survival curves

There are a variety of novel therapeutics moving forward in rrMM, including novel proteosome inhibitors, HDAC inhibitors, nuclear export protein inhibitors and any others. One class of therapeutic gaining significant attention are the antibodies directed to the MM cells. These include the antibodies to CD38 and other MM-selective cell surface proteins.

The lead therapeutic among the anti-CD38 antibodies is daratumumab from Genmab in collaboration with Janssen. The deal included a US$55 million upfront payment, an $80 million equity stake in Genmab, and milestone payments adding up to $1.1 billion or more.Daratumumab is a huMAX CD38 mAb which kills CD38+ tumor cells via CDC and ADCC activity and antibody-dependent cellular phagocytosis (ADCP) by macrophages. Additional activity may be due to apoptosis upon secondary cross-linking and modulation of CD38 enzymatic function (see ASH 2014 abstract # 3474). Daratumumab received the FDA’s breakthrough therapy designation in May 2013 for treatment of rrMM (for patients failing 2 lines of therapy).

When combined with lenalidomide and dexamethasone (len/dex), daratumumab produced an overall response rate (ORR) of 75% in the phase I dose ranging clinical trial. The trial was designed to accommodate an expansion cohort dosed at the MTD (maximum tolerated dose) of 16mg/kg. In the expansion cohort the ORR was ~ 92%.

In a phase Ib study daratumumab was combined with various regimens:

Screen Shot 2015-02-14 at 11.51.52 AM

These efficacy numbers are startlingly good. What will be really impressive is the associated duraton of response (DOR) and overall survival (OS) data once the trial is mature. In early February preliminary results from another Phase II study were announced. The study, called MMY2002, is listed as NCT01985126 on clinical trials.gov    (link 2). This two-part study enrolled 124 rrMS patients who had received at least three prior lines of therapy, including both a proteasome inhibitor and an IMiD, or were double refractory to therapy with a proteasome inhibitor plus an IMiD. The primary objectives of the study were to define the optimal dose and dosing schedule, to determine the efficacy of two treatment regimens of daratumumab as measured by ORR, and to further characterize the safety of daratumumab as a single agent. Two doses of daratumumab were compared in part 1, at 8 mg/kg and 16 mg/kg. The expansion cohort (part 2) received the higher dose based on interim safety analysis of the initial dose comparison.

The ORR was 29.2% in the 16 mg/kg dosing group with a DOR of 7.4 months. We can expect additional data to be presented at a medical conference this year, perhaps ASCO or ESMO, and ASH or EHA. These data will support the breakthrough therapy designation for daratumumab in rrMM and may lead to a 2015 approval in this patient population, i.e. based on the phase II results.

Additional daratumumab trials include 5 phase III trials in MM, including a series of studies in newly diagnosed MM, therefore, as front-line therapy, and a phase II trial ((LYM2001) in hematological malignancies. The study will evaluate daratumumab monotherapy in three different types of NHL, diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL) and mantle cell lymphoma (MCL).  The study is expected to start enrolling patients in 2015.

Sanofi Oncology is developing SAR650984 (SAR), is a human IgG1 antibody that targets CD38. TCD11863 (NCT01749969) is a phase Ib trial evaluating the combination of SAR with len/dex in rrMM: patients averaged six prior therapies. These prior therapies included the second line therapeutics lenalidomide (94%), pomalidomide (29%), bortezomib (94%), and carfilzomib (48%). Eighty four percent of patients were relapsed and refractory to a least one second line therapeutic. In the dose ranging phase, the highest SAR dose of 10mg/kg was well tolerated.

After a median 9 month follow up, the ORR was 58%, with a clinical benefit rate of 65%, including a 6% stringent complete response rate. In patients receiving the 10 mg/kg dose, the ORR was 63%. The median progression free survival (PFS) was 6.2 months for all evaluated patients but was not yet reached in patients who received fewer than three prior therapeutic regimens before entering the study.

Looking just at the 84% of who were relapsed and refractory to least one second line therapeutic, the ORR was 50%.

An interesting study presented at ASH in December suggested that Immunogenetic factors contributing to NK cell function influenced clinical activity in pts treated with SAR/LEN/Dex. Specifically, the presence of a high-affinity KIR3DL1, HLA-B Bw4-80Ile genotype was associated with high ORR and prolonged PFS. This suggests that the NK cell competency of the patient influences the ability of NK cells to become activated in the presence of tumor cells coated with SAR antibodies. This fascinating study (ASH 2014, Abstract # 2126) should stimulate investigation of mechanisms of NK cell activation that could be used in combination with SAR, assuming the presence of len/dex does not complicate the picture. There are additional clinical studies of SAR, listed here: link 3. These include a phase I/II study in hematologic malignancies.

In addition to daratumumab and SAR650984, Celgene and MorphoSys are collaborating on the development of the CD38 antibody MOR03087 (aka MOR202). This antibody is currently being investigated as monotherapy and in combination with len/dexamethasone or bor/dex in a phase I/II rrMM study (NCT01421186). The Morphosys licensing deal with Celgene included a $92M upfront, $60M equity investment and downstream milestones. Takeda is developing the anti-CD38 antibodies Ab79 and Ab19, currently in preclinical studies (link 4). Xencor has a CD3/CD38 bispecific program. The small private biotech Molecular Templates has an anti-CD38 antibody-drug conjugate program. There are likely other programs out there.

Elotizumab (ELO) from Bristol Myers Squibb targets a different MM antigen, SLAMF7 (aka CS-1). A presentation at ASH (abstract #2119) reported early results from a phase Ib study of ELO in combination with len/dex.ELO selectively kills SLAMF7-positive MM cells through both direct activation and engagement of NK cells. A multicenter, open-label, Phase Ib trial (NCT01393964) enrolled patients with newly diagnosed or rrMM and varying renal function. Renal function is a dose limiting feature of rrMM treatment and disease progression. ELO (10 mg/kg) plus len/dex was given in 28-day cycles until disease progression or unacceptable toxicity. 26 pts were treated, 8 with Normal Renal Function (NRF), 9 with Renal Insufficiency (RI), and 9 with End Stage Renal Disease (ESRD). 89% had received prior therapy (median 2 regimens). Prior bor, thalidomide, or len treatment occurred in 21 (81%), 11 (42%), and 9 (35%) patients, respectively. ORRs were 75% (NRF), 67% (SRI), and 56% (ESRD). Thirty-eight percent NRF, 56% of SRI, and 11% of ESRD patients had a very good partial response or better. Therefore ELO/len/dex was well tolerated and showed clinical responses in MM patients regardless of renal function.

These new therapeutics for MM will certainly complement the existing triple therapies, giving patients added hope and time. We certainly expect that one of the new combinations of antibodies and the second line “triple therapeutics” discussed above will have an even more dramatic impact on MM when given in the front-line setting.

In the meantime Janssen (J&J) and Genmab are poised to give Celgene some real competition in the MM space.

Reading List – day 2, #JPM15 edition – The Power of Immunotherapy

BMY today announced that an open-label, randomized Phase 3 study (CheckMate-017; NCT0164200) evaluating Opdivo vs docetaxel in previously treated patients with advanced, squamous NSCLC was stopped early because an assessment concluded that the study met its endpoint, demonstrating superior overall survival in patients receiving Opdivo.

CheckMate-017 is a Phase 3, open-label, randomized study. Patients who had failed prior platinum doublet-based chemotherapy received either nivolumab 3 mg/kg intravenously every two weeks or docetaxel 75 mg/m2 intravenously every three weeks (N = 272, randomized).

The primary endpoint is overall survival. Secondary endpoints include objective response rate and progression free survival. The initial time frame was 38 months from enrollment. The trial opened in 2012 and was scheduled for primary outcome measurement in January 2016, so this halt is a year early. An association between PD-L1 expression and efficacy measures (ORR, OS PFS) will be explored post hoc.

Arms Assigned Interventions
Experimental: Arm A: Nivolumab

Nivolumab 3 mg/kg solution intravenously every 2 weeks until documented disease progression, discontinuation due to toxicity, withdrawal of consent or the study ends

Biological: Nivolumab

Other Name: BMS-936558

Experimental: Arm B: Docetaxel

Docetaxel 75 mg/m2 solution intravenously every 3 weeks until documented disease progression, discontinuation due to toxicity, withdrawal of consent or the study ends

Drug: Docetaxel

Other Name: Taxotere®

Key Inclusion Criteria:

  • Adult subjects with Stage IIIB/IV disease or with recurrent or progressive squamous cell NSCLC who present with disease following multimodal therapy (radiation therapy, surgical resection or definitive chemoradiation therapy for locally advanced disease)
  • Disease recurrence or progression during/after one prior platinum doublet-based chemotherapy regimen for advanced or metastatic disease
  • Evaluable by imaging (CT/MRI) per RECIST 1.1 criteria
  • ECOG performance status ≤1
  • Formalin fixed, paraffin-embedded tumor tissue block or unstained slides of tumor sample (archival or recent) available for biomarker evaluation. Biopsy is excisional, incisional or core needle.

Key Exclusion Criteria:

  • Subjects with untreated central nervous system (CNS) metastases are excluded. Subjects are eligible if CNS metastases are treated and subjects are neurologically returned to baseline for at least 2 weeks prior to enrollment. In addition, subjects must be either off corticosteroids, or on a stable or decreasing dose of ≤10 mg daily prednisone (or equivalent)
  • Subjects with active, known or suspected autoimmune disease (except for type I diabetes mellitus, hypothyroidism only requiring hormone replacement, vitiligo, psoriasis, or alopecia not requiring systemic treatment, or conditions not expected to recur in the absence of an external trigger).
  • Subjects with a condition requiring systemic treatment with either corticosteroids or other immunosuppressive medications within 14 days of randomization
  • Prior therapy with anti- PD-1, anti-PD-L1, anti- PD-L2, anti-CD137, or anti-CTLA-4 antibody (including ipilimumab or any other antibody or drug specifically targeting T-cell co-stimulation or checkpoint pathways)
  • Prior treatment with Docetaxel
  • Subjects with interstitial lung disease that is symptomatic or may interfere with the detection or management of suspected drug-related pulmonary toxicity
  • Treatment with any investigational agent within 14 days of first administration of study treatment

So stopping this trial early is great news. What can we anticipate in addition to the report of ORR, OS, PFS etc that we will likely get at ASCO? The answer lies in the details regarding the Checkmate-017 trial.

A few pointers:

1) there is no inclusion biomarker, ie., there is no specified use of PD-1 staining of biopsy tissue that puts patients into the trial. This is in line with the confusion surrounding use of PD-1 as a biomaker.

2) there is a requirement that pretreatment biopsy specimens be available, as these will be used retrospectively to associate response with expression of biomarkers, including PD-L1 (the PD-1 ligand). No doubt many other biomarkers will be explored.

3) if you have autoimmune disease or interstitial lung disease (a broad term) you are out of luck. So patients with RA, MS, IBD, lupus, and a whole host of other autoimmune diseases need not apply. If you have Type 1 Diabetes though, your good to go (which among other things reminds us just how damn puzzling T1D autoimmunity is).

4) you also cannot be immunosuppressed (corticosteroids) or have had prior treatment with with anti- PD-1, anti-PD-L1, anti-PD-L2, anti-CD137, anti-CTLA-4 antibody (including ipilimumab), or docetaxel. This last one excludes patients who may have gotten docetaxel as second line therapy, which is a setting in which it is commonly used. This tells us that the risk of toxicity in patients is deemed too high.

5) the study halt, being based on efficacy, does not mention toxicity, so we’ll have to wait and see.

Now back to the reading list. In the context of biomarker investigation this story has some resonance:

Day 2 – Immunotherapy: back to those biomarkers of response

Genetic Evolution of T-cell Resistance in the Course of Melanoma Progression

Sucker et al 2014. Clin Cancer Res; 20(24); 6593–604

This interesting paper outlines a technique for tracking the evolution of immune resistance, an essential part of the so-called immune editing process, using in vitro analysis of patient-derived (PDX) samples.

Three consecutive melanoma lesions obtained within one year of developing stage IV disease were analyzed for their recognition by autologous T cells.

One skin and two lymph node metastases were initially analyzed for T-cell infiltration. Then, melanoma cell lines established from the respective lesions. T-cell–stimulatory capacity, expression of cell surface molecules involved in T-cell activation, and specific genetic alterations affecting the tumor–T-cell interactions were identified.

Sampled skin lesions were infiltrated by T cells. The T cell infiltrate was diminished in the lymph node metastatic samples which were found to be HLA class I–negative due to an inactivating mutation in one allele of the beta-2-microglobulin (B2M) gene and concomitant loss of the other allele by a deletion on chromosome 15q. This is an impressive response to avoid immune detection.

The study reveals a progressive loss in melanoma immunogenicity during metastasis. Screening tumors for this and other genetic alterations  that cause acquired immune resistance will be clinically relevant in terms of predicting patient responses and designing combinatorial approaches to immunotherapy.

Day 2 – Immunotherapy: back to those tox issues: it’s hard to control ipilimumab-induced tox

In the trial above we noted two things: no current corticosteroid use and no prior ipilimumab. Turns out these don’t play well together either

http://clincancerres.aacrjournals.org/content/early/2014/12/23/1078-0432.CCR-14-2353.abstract

Min et el. 2014. Systemic high dose corticosteroid treatment does not improve the outcome of ipilimumab-related hypophysitis: a retrospective cohort study

Purpose To examine the onset and outcome of ipilimumab-related hypophysitis and the response to treatment with systemic high dose corticosteroids. Patient and Methods Twenty-five patients who developed ipilimumab-related hypophysitis were analyzed for the incidence, time to onset, time to resolution, frequency of resolution, and the effect of systemic high-dose corticosteroids on clinical outcome. To calculate the incidence, the total number (187) of patients with metastatic melanoma treated with ipilimumab at Dana-Farber Cancer Institute (DFCI) was retrieved from the DFCI oncology database. Comparisons between corticosteroid treatment groups were performed using Fisher’s exact test. The distributions of overall survival were based on the method of Kaplan-Meier. Results The overall incidence of ipilimumab-related hypophysitis was 13%, with a higher rate in males (16.1%) than females (8.7%). The median time to onset of hypophysitis after initiation of ipilimumab treatment was 9 weeks (range: 5-36 weeks). Resolution of pituitary enlargement, secondary adrenal insufficiency, secondary hypothyroidism, male secondary hypogonadism, and hyponatremia occurred in 73%, 0%, 64%, 45%, and 92% of patients, respectively. Systemic high dose corticosteroid treatment did not improve the outcome of hypophysitis as measured by resolution frequency and time to resolution. One-year overall survival in the cohort of patients was 83%, and while slightly higher in patients who did not receive high dose corticosteroids, there was no statistically significant difference between treatment arms. Conclusion Systemic high dose corticosteroid therapy in patients with ipilimumab-related hypophysitis may not be indicated. Instead, supportive treatment of hypophysitis-related hormone deficiencies with the corresponding hormone replacement should be given.

The widget TIGIT

Genentech continues to work on TIGIT, so what the heck is this target? Lets have a look, but first, some context.

T cell constraint is a fundamental attribute of tumor-induced immunosuppression. CTLA4 and PD-1 are central regulators of this process, and antibody blockade of these pathways can restore anti-tumor responses. The state of T cell constraint (non-responsiveness) has been termed anergy in reference to CD4+ T cells and exhaustion in reference to CD8+ T cells. Exhausted CD8+ T cells have a recognizable T cell phenotype characterized by the expression of diverse inhibitory pathways and proteins, including PD-1, TIM-3, LAG-3 and TIGIT. Whether such a phenotype is absolutely selective for exhausted CD8s is a matter of debate, but is a good starting point for a discussion of the need for so many regulatory pathways.

Dual gene-deficient (knock-out) mice and the administration of blocking antibody combinations have shown that the inhibitory receptors can function synergistically to reject tumors in mouse models. The hypothesis that individual co-inhibitory receptors contribute distinct functions to collectively limit T cell responses has recently been tested in human cancer clinical trials, yielding the impressive result that co-blockade of CTLA4 and PD-1 has synergistic and beneficial anti-tumor activity. Such benefit comes with a toxicity cost, as pathological autoimmunity is revealed when the “brakes” come off the immune system.

Why does the T cell arm of immune system require so many different control pathways? This is a reasonable question, which can be answered somewhat glibly with the observation that uncontrolled immunity leads to autoimmune disease and/or chronic inflammation. Still, though, why are multiple breaks required? The working hypothesis is that one pathway (CTLA4) regulates T cell activation by CD28 that normally occurs in the spleen, lymph nodes, Peyer’s patches and other “secondary lymphoid organs” (the thymus, bone marrow and fetal liver are the major primary lymphoid organs). A second pathway (PD-1) is generally thought to regulate “peripheral” T cell activation at the sites of pathogen encounter – in this sense “peripheral” means outside of the lymphoid organs themselves, that is, in the tissues and circulation, or, in the case of cancer immunology, within the tumor. So, simplistically, there is one control pathway (CTLA4) in the house and another (PD-1) in the yard. The recent paper (link 1) describing the release of T cell recognition of tumor antigens upon CTLA4 blockade in melanoma suggests either cross-talk between the compartment (i.e. tumor beds have lymphatic or circulatory drainage to secondary lymphoid organs) or that the role of CTLA4 is more complex than we think.

What about the other control pathways? LAG-3 is a competitive regulator of CD4/MHCII antigen recognition activity and was shown to confer Treg function when transfected into naive CD4+ T cells. The expression of LAG-3 on CD8+ T cells (which are critical for anti-tumor activity) suggests a role in the interaction of CD4+ and CD8+ T cells. LAG-3 is also expressed on tumor cells and may mask tumors from immune recognition. LAG3/PD-1 doubly gene-deficient mice can reject poorly immunogenic tumors that wild-type mice cannot reject. However, the doubly deficient knockout mice also develop pathological and aggressive autoimmunity. These results show that these proteins have distinct roles in regulating immune responses.

TIM-3 has several immune regulatory activities, one of which is to suppress T cell recognition of phosphatidylserine, a molecule expressed on dead and dying cells but also on tumor cells. As with LAG-3 the combination of anti-PD-1 and anti-TIM-3 antibodies had enhanced anti-tumor efficacy in mouse tumor models when compared to either antibody alone.

And now we have TIGIT, an Ig superfamily protein and a member of the PVR/nectin family that includes CD226 (DNAM-1), CD96, CD112 (PVRL2), and CD155 (PVR), among others. The biology of this family of proteins is complex and a little intimidating. Genentech has been prosecuting this pathway for several years, and their new paper (link 2) has perhaps shed additional light on the biology and utility of this target.

One mechanism by which TIGIT modulated immune responses is via the interaction of TIGIT on T cells with CD155 expressed on immature or resting dendritic cells, which blocks maturation signals normally delivered by CD226, that is, TIGIT is a competitive inhibitor of the interaction of CD226 with CD155. The authors note that this system resembles the co-stimulatory/co-inhibitory receptor pair of CD28 and CTLA-4, where CTLA4 is a competitive inhibitor of the interaction of CD28 with B7-1/CD80 and B7-2/CD86. The expression pattern of the receptors is also similar: both TIGIT and CTLA-4 are induced upon cell activation, while the expression of CD226 and CD28 is constitutive.

As alluded to above, and noted explicitly by the Genentech team, the molecular and functional relationships between TIGIT and it’s various ligands/co-receptors are poorly characterized. Furthermore, TIGIT’s role in regulating CD8+ T cell responses and the mechanisms underlying such regulation are not known. Of note, antibodies to TIGIT or PD-L1 alone enhanced CD8+ T cell effector function in tumor-draining lymph nodes, but blockade of both receptors was required to allow activation of CD8+ T cells within the tumor microenvironment, as measured by IFNy production. The authors conclude that TIGIT is a critical and regulator of CD8+ T cell anti-tumor activity. The mechanism of action evoked to explain the role of TIGIT in the tumor setting was addressed using FRET and other analyses. The authors show that TIGIT interacts directly with CD226 to prevent homodimerization, a component of the interaction of CD226 with CD155.

There are a few things to consider here. The animal models were run with very high amounts of anti-TIGIT and anti-PD-L1 antibodies on board (10 mg/kg anti-PD-L1 and 25 mg/kg anti-TIGIT) given 3 times a week. That’s nearly a gram of antibody approximately every 2.5 days. While the anti-PD-L1 antibody used has a mutated Fc domain that cannot mediate direct cell killing by ADCC, the anti-TIGIT antibody used is a wild-type IgG2a isotype antibody and almost certainly mediates direct killing of TIGIT+ cells. While the in vitro FRET assays are suggestive of the proposed mechanism of action, what is actually occurring in vivo is less clear. TIGIT expression on NK cells is also worthy of further exploration.

So I have a doubt. Not that the pathway is important, but that we really have a good sense of how it functions, nor how antagonism of the pathway in patients will impact anti-tumor activity and baseline immune responses. Locally, Drs Vijay Kuchroo and Ana Anderson have done wonderful work on TIGIT biology, and no doubt one or more of the Cambridge immunotherapy companies is working on this target and exploring it’s utility in the tumor setting. Given the expression pattern of TIGIT in tumors – i.e. on PD-1+/TIM3+ “exhausted” T cells – it is certainly worth the effort to find out.

How to select patients who should respond to anti-TIGIT co-therapy (or anti-TIM-3 or anti-LAG-3) is a critical question, best left for another day.

stay tuned

AND HAPPY HOLIDAYS AND PEACE TO ALL