Category Archives: biologics

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.

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.

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.

Focus on Breast Cancer Therapy – Literature Sampling – Oncology – October 13, 2014

This is a tumor class we don’t write about that often but it bears remembering that there remains significant unmet need in an indication often touted as an example of victory over cancer. For those patients encountering resistance to therapy, metastases or breast cancers subtypes with few new options (e.g. triple negative breast cancer, TNBC) victory can seem far away.

There was a flurry of interesting papers over the last few weeks that I think give a peek behind the curtain at progress and frustrations in the ongoing evolution of breast cancer care. This post assumes some baseline knowledge of breast cancer therapy and application to specific oncogenic signatures.

As many readers will know, HER2-directed therapy has transformed care for patients carrying elevated levels of the growth factor receptor HER2 aka EGFR2. About 20% of breast cancer patients are HER2+ or become HER2+ as a mechanism of resistance to other therapies). This is an aggressive breast cancer subtype that has yielded to HER-2 targeting agents such as the small molecule inhibitor lapatinib that blocks EGFR and EGFR2 signaling, trastuzumab, an antibody that specifically kills EGFR2 positive cells, and T-DM1, an antibody-drug conjugate (ADC) consisting of trastuzumab bound to a cytotoxic “payload”. Lapatinib (Tykerbtm) is made by GlaxoSmithKline (GSK), trastuzumab by Roche/Genentech (Herceptintm) and T-DM1 (Kadcylatm) by Roche in collaboration with Immunogen. A second anti-EGFR2 antibody, pertuzumab (Perjetatm, Roche/Genentech) binds a different epitope than trastuzumab and is approved in combination with that antibody.

Although some patients experience long-term remission with HER2-directed therapeutics, relapse is a common problem. There are various mechanisms of relapse, and PI3K activation is a common one (first identified in 2009 by multiple groups). PI3K signals through AKT to mTOR to drive expression of numerous pro-growth and pro-survival genes, making this a known oncogenic pathway, indeed it is a known oncogenic pathway in breast cancer.

Recently Loibl et al. (http://jco.ascopubs.org/content/32/29/3212) reported that activating mutations in the PIK3CA gene that encodes for the PI3K alpha subunit were associated with poor response to initial HER2-directed therapy, that is, not in the relapse setting. This means we are seeing the impact of the activation of both the EGFR2 and PI3K pathways in these patients. Of the breast cancer patients examined, 21.4% harbored a PIK3CA mutation. Detection of a PIK3CA mutation was associated with a lower Complete Response (CR) rate in a cohort of nearly 300 EGFR–positive tumors. The CR rate was 11.3% with a PIK3CA mutation compared with 27.5% without the mutation. Worse yet, in patients with PIK3CA mutation, the CR rates were 16%, 24.3%, and 17.4% with lapatinib, trastuzumab, and the combination, respectively, compared to 18.2%, 33%, and 37.1%, respectively in patients not carrying the mutation. The difference in CR rates was significant (P = .017). Fortunately, multiple drugs targeting different parts of this pathway have been developed, and it is of course possible to combine these inhibitors with anti-HER2 therapies in patients with defined PIK3CA activating mutations. Indeed one such study of the mTOR inhibitor everolimus (Afinitortm, Novartis) in combination with trastuzumab showed an increase in progression-free survival, although there was considerable toxicity associated with the regimen (Andre et al.  2014). Many other trials with more selective inhibitors of the pathway are underway targeting PI3K rather than mTOR, and may give a better efficacy/toxicity profile. However most of these trials are in the relapse setting rather than the first-line setting, and results may not be as effective once relapse has occurred. One take home from the Loibl et al. is that HER2+ breast cancer patients should be screened for PIK3CA activating mutations so that combination therapy can be initiated earlier in the therapy cycle.

Saura et al. (link) reported early phase clinical results of a new pan-EGFR inhibitor for HER2+ breast cancer. Neratinib, developed by Pfizer and Puma Biotechnology, was tested in combination with chemotherapy. This study presents the results of the multinational, open-label, phase I/II trial in patients with HER2-positive metastatic breast cancer, and is most notable for defining the maximum tolerated dose (MTD) of 240 mg per day (with the chemotherapeutic capecitabine). The most common drug-related adverse event was diarrhea (in 88% of patients), severe enough to cause dose interruptions or dose reductions in some patients. In July of this year Puma announced interim results of a Phase III trail of neratinib versus placebo after adjuvant treatment with trastuzumab in women with early stage HER2-positive breast cancer. The ExteNET trial enrolled over 2,800 patients with early-stage HER2-positive breast cancer who had undergone surgery and adjuvant treatment with trastuzumab, and were then randomized to receive extended adjuvant treatment with either neratinib or placebo for a period of one year. The primary endpoint of the Phase III trial was disease free survival (DFS). Neratinib therapy resulted in a 33% improvement in DFS (versus placebo, p = 0.0046). There was also a 37% improvement in DFS including ductal carcinoma in situ versus placebo (this was the secondary endpoint).

Neratinib has had tolerability issues due to the grade 3 or higher diarrhea, and we will have to see if this is enough to limit its use outside the clinical trial setting. However, the drug’s efficacy is very promising, and the toxicity may be manageable. It is unclear where the companies will present the full results of this Phase III trial, although the upcoming San Antonio Breast Cancer Congress is one likely venue.

A quick look at Puma’s stock (NASDAQ: PBYI) over the last year shows the impact this data set had in July:

 Screen Shot 2014-10-14 at 7.19.36 AM

The stock jumped on large volume in July and has held steady even through the recent downturn. I think we can expect little movement until the full Phase 3 results are presented. While we are likely to see more detailed DFS data from the Phase 3 study, significant upside would be possible if an impact on overall survival (OS) was demonstrated – but that is a very high hurdle in this patient population.

Notably, ongoing clinical trials of neratinib include TNBC and lung cancer (NSCLC) (both in combination with chemotherapy) and renal cancer (RCC) in combination with cetuximab (anti-EGFR antibody, Erbituxtm, from BristolMyersSquibb). Preliminary NSCLC data were presented at the ESMO conference last month. If the new indications are impacted positively by this therapy, we can expect further value in PBYI shares.

Lets turn to a late phase disappointment in metastatic breast cancer. An antibody to a different growth factor receptor, VEGFR2, failed to shown clinical benefit in the first-line setting when added to docetaxel chemotherapy. Mackey et al (link2) reported that ramucirumab (Cyramzatm, Eli Lilly), a human antibody that binds VEGFR2 receptor-2 and blocks ligand-stimulated activation, had no impact in a Phase 3 trial of 1,144 patients with HER2–negative breast cancer who had not received cytotoxic chemotherapy in the advanced setting. The primary end point was progression-free survival (PFS) and the secondary endpoint was OS. HER2-negative breast cancer is less aggressive than HER2-positive breast cancer and can be controlled with debulking and chemotherapy if it has not advanced to extensive lymph node involvement (TNBC is a further, and very aggressive, subset). Eli Lilly is also testing icrucumab, an anti-VEGFR1 in a similar setting.

Several studies have focused on the predictive value of tumor-infiltrating lymphocyte (TIL) status in breast cancer settings. Nabholtz et al (TIL-1 link) studies the therapeutic utility of panitumumab combined with anthracycline-taxane-based chemotherapy in patients with operable, stage II-III, TNBC. The CR rate for combination therapy was ~55% compared to ~47% with chemotherpy alone. Poor response to therapy was associated with high EGFR expression and low cytokeratin 8/18 expression. A positive response to therapy was correlated with a high density of CD8+ TILs, suggesting that interrupting growth factor receptor signaling allowed a productive immune response to the tumor to take place.

Loi et al. (TIL-2 link) reported that TIL status was a useful marker for both TNBC and HER2+ patients treated with trastuzumab. In TNBC, TIL numbers correlated with metastatic recurrance of disease. In HER2+ breast cancer, TIL numbers were associated with better response to trastuzumab therapy.

These two latter studies suggest that immunotherapy will play a significant role in the treatment of diverse breast cancers. Early attempts here include the CD3 x HER2 bispecific antibodies, ipilimumab treatment, nivolumab treatment and many others. That’s a story for another time.

stay tuned.

Yelling Yellen and The Least Licensable Unit (LLU)

In grad school we laughed about the LPU (Least Publishable Unit), those 2 or 3 crappy papers that should have been one better paper.

Today lets introduce the Least Licensable Unit, the LLU. Amidst all the angst and anger directed at the Fed chair yesterday it occurred to me that excessive valuation has a trickle-down effect. When anything is worth too much, almost nothing is still worth a little. That almost-nothing is an LLU. When we look at the current state of asset acquisition in the immuno-oncology (IO) space we see this clearly. Very early stage assets are being land-grabbed by very large companies, and a certain sly sense of glee has crept up the brainstems of savvy biotech entrepreneurs who are rightly looking at looking at IO assets as the rarest of gemstones. Even the mere hint of sparkle in an otherwise dirt sample has prospectors racing to the wilds of Waltham and the coffee shops of Cambridge looking for LLUs.

Why is this? A few years ago (a very few) you would need to drag a program right up to the threshold of IND enablement in order to attract any attention at all. Your IP would have to be rock solid and be good for 30 years (with extensions, I know I know). Preclinical pharmacology? check. Repeat dose toxicology? check. Non-human primates? of course. A validated biomarker program? well underway!

What changed? Pretty simply, IO creates a paradigm shift in the way oncology (and many other diseases) are treated. Think rheumatoid arthritis, psoriasis and Crohn’s disease before anti-TNFs. Multiple sclerosis before beta-interferons. HCV before Vertex, Gilead and Abbvie. We are looking at a similar level of evolution in clinical practice across the whole of oncology – meaning massive disruption. With the stakes this high you have to get out, or go big. And so we see that big bets and lots of them are the order of the day. But now, a few years in, the hunt for quality is harder, and programs are taken early. The hunt for assets is so intense that the academic licensing groups at our top tier universities and medical centers are overwhelmed with inquiries. The beautiful thing here is that such leaps of faith (lets face it) are now less risky in part because technologies are rapidly differentiating. Are you in danger of stumbling into patents that block your CAR T designs? Bolt on a gene editing company and tinker so you can move into new ip. No room for your new PD-1 antibody? Blaze trail to a newly defined epitope and defend your little patch. With so many companies applying technology to assets, novel composition is easier to define. You might be able to fix an LLU, make it better, make it into a drug.

All such asset stampedes eventually run into a wall of diminishing returns as the front runners take off and the leftovers get trampled by too many competitors. That is starting to happen now in IO. Yes, it is. So what do we do now? I have a few ideas:

1) Sifting through LLUs take hard-core due diligence, so let us know if we can help

2) It is going to be harder to partner “me too” assets – programs need to differentiate or better yet track novel biology

3) In IO the T cell space is not played out yet, but we should be looking at NK cells and myeloid lineages for extra traction, and watch for the development of novel immune checkpoint pathways and better agonist antibodies (or both)

4) The CAR T space seems overwrought – I think this has to settle out over a few years – but despite this I also expect to see a big wave of new companies emerge from stealth in the next 0 – 18 months

5) Bispecific antibodies and ADCs will quietly advance to capture a dominant position in IO

6) Finally if you are looking for or have a beautiful asset, seek help in partnering – you’ll save time and wind up in a better partnership (sure, call me, this is what we do best)

cheers all, and stay tuned

Targeting TNFRs with agonist antibodies for cancer therapy: 4-1BB, GITR, CD27

One of the puzzles in thinking about the available costimulatory receptors on T cells (and NK cells) is the unsettling number of them. Sticking just to the TNF receptor superfamily (TNFRSF) we have OX40 (discussed earlier), 4-1BB, GITR, CD27, and also the TNF receptors themselves (1 and 2), the lymphotoxin beta-receptor, HVEM, and TNFRSF25. There may be some I’ve forgotten. As noted in part 1 OX40, GITR, 4-1BB and CD27 are evolutionary cousins, as are their cognate ligands. Why did the immune system evolve such a complexity of T cell costimulators?

The answer is not entirely clear although the expression patterns and kinetics of expression suggest some rationale for understanding the number of different receptors. Also, as it’s understood that all the TNF receptors signal via NF-kB, Jun and p38, we might see these receptors either compete (for signaling proteins) or cooperate. All of the available genetic and pharmacologic data suggest they cooperate or even synergize, thereby powering the T cell response when needed. Since T cell responses (and immune responses generally) are so dangerous when dysregulated, the multiplicity of on and off switches presumably allows for redundancy of control.

As we said previously, OX40 comes on slow and easy, starting about 12 hours after TCR stimulation, and riding along for up to 96 hours. This is in vitro, cell culture data … so lets recognize that in vivo, in response to the chaotic presentation of antigen, the population of T cells is likely to be turning over, proliferating … so it’s unlikely we will see a finely tuned kinetic response in the real world, as regards the population of responding cells. Nonetheless we can focus on a single T cell, just the one. And we’ve guessed it will be expressing OX40 say from day 2 to day 5 after activation. Lets ignore the fact that activated effector T cells are likely dividing more rapidly than every 5 days, and just ask the simple question – of the other TNFSF receptors, what else is expressed and when, and on what T cell and other cell types?

Cue 4-1BB.

4-1BB is also expressed following T cell activation, and is expressed on other cell types also. 4-1BB expression come up much more quickly after T cell activation, within a few hours, and wanes after several days. This receptor is critical to supporting activated T cell proliferation, differentiation and survival. Expression on T cells may be coincident with OX40, but the consequences of engaging the receptor with an agonist antibody are different. 4-1BB preferentially supports the proliferation and survival of CD8+ T cells, although at least in some settings the activity of CD4+ T cells is also stimulated through 4-1BB. Much of the anti-tumor activity of 4-1BB agonist antibodies in preclinical studies can be traced to stimulation of NK cells although this depends of the tumor type and model used. Less well understood is the role on 4-1BB on other cells types. This receptor is also found on DCs, macrophages, granulocytes, and Tregs. Expression has also been described on vascular endothelium and on some tumor cells. The role of 4-1BB is confusing, with various studies showing expansion of the Treg subset and others suggesting that 4-1BB dampens Treg responses, perhaps via direct effects on DCs. The 4-1BB gene-knockout mouse shows aspects of autoimmune disorders (at least in the mouse strains tested), suggesting a role for 4-1BB in maintaining immune homeostasis following activation. 4-1BB knockout mice have trouble handling tumor challenge, and at least some spontaneously develop B cell lymphomas as they age. It is all a bit complicated.

Regardless, there are two antibodies that can provide some early clinical data. Bristol-Myers Squibb (BMY) started development of the BMS-663513 antibody quite early, before the immunotherapy wave had really gotten started. BMS-663513 is a specific anti-4-1BB agonist antibody, isotype IgG4. The antibody ran into toxicity issues in a phase 2 trial of metastatic melanoma in 2011, leading to a halt of three trials with that antibody. As the toxicity was correlated with dose, BMY has restarted the clinical campaign with BMS-663513, now called urelumab to establish a safe and efficacious dose. A monotherapy trial is being run in patients with advanced/metastatic solid tumors or with relapsed/refractory Non-Hodgkin Lymphoma (NHL). A second trial in NHL is being run in combination with rituximab treatment. A third trial in advanced/metastatic colorectal and head and neck cancers is being run in combination with cetuximab (anti-EGFR). Pfizer’s (PFE) PF-05082566 is an agonist anti-4-1BB antibody (IgG2 isotype). One trial is listed at clinicaltrials.gov, a 3×3 dose escalation phase 1 trial run as monotherapy in patients with advanced cancers, and as combination therapy with rituximab in NHL.

At the June ASCO meeting there will be updates on both the BMY and PFE programs. BMY has a presentation focused on mechanism of action and biomarker analyses. Abstract #3017 outlines the goal of monitoring the immune status of 4 patients prior to and during the phase 1 study of urelumab (BMS-663513: clinical trial NCT01471210). The antibody was given every 3 weeks and the analysis presents results through 3 cycles. PBMCs were isolated from whole blood, and stimulated for 4 hours with PMA/ionomycin to activate lymphocytes. There was an increase in CD8 T cells up to 41% and NK cells up to 62%. CD4 T cells decreased by as much as 23% and regulatory CD4 T cells decreased by as much as 18% comparing the 3rd cycle to baseline. The results are consistent with a preferential impact on CD8+ T cells and NK cells. The level of the cytokines GM-CSF and IFNgamma were increased.

The PFE study (abstract #3007) describes very early data from clinical trial NCT01307267. Patients received PF-05082566 IV every 4 weeks (one cycle) with an 8 week period for assessment of dose-limiting toxicity (DLT) and radiographic analysis of tumor burden (RECIST 1.1). 27 patients were up to 0.3 mg/kg, the highest dose reported in the abstract. The majority of patients had either colorectal cancer (n=11) or Merkel cell carcinoma (n=6), the rest were a collection of solid tumor patients and 2 patients with B cell lymphoma.  25/27 patients completed the DLT assessment period (first cycle). No DLT was established but only 7 patients remain on therapy. All discontinuations from treatment were due to disease progression. A best overall response of stable disease was observed in 6 patients. No duration data is supplied.

These two early trials suggest that safe dose levels can be achieved, that a mechanism of action can be confirmed (urelumab: expansion of CD8+ T cells and NK cells), and that some clinical response can be observed (PF-05082566: stable disease). That’s a pretty good picture coming out of Phase 1. As preclinical data suggest that 4-1BB is most effective in various combination formats, it will be interesting to monitor advances in the rituximab and cetuximab co-therapy arms of these trials. Several potent combinations arising in the preclinical literature include 4-1BB with immune checkpoint inhibition (CTLA4 or the PD-1 pathway) and in combination with agonist OX40 antibody therapy.

Lets get back to the Treg cells, whose function is to suppress immune responses, primarily those of CD4+ T cells. These express 4-1BB constitutively, although it’s not clear how or if they are responding to treatment with agonist anti-4-1BB antibodies. Let’s turn to a different pathway known to have a profound effect on Tregs, the Glucocorticoid-Induced TNFR Related gene (GITR). GITR was first identified as a regulatory T-cell marker and was shown to play a critical role in breaking T cell tolerance by direct suppression of Treg activity. The preclinical evaluation of GITR produced some very striking data, including in combination settings in which anti-GITR antibodies essentially synergized with other immune checkpoint therapeutics to eliminate established tumors. Such combinations have included PD-1 blockade and CTLA4 blockade. GITR agonism is also synergistic with chemotherapy in preclinical models. Clinical development of GITR antibodies has been slow. A program initiated at TolerX and reborn at GITR, Inc., is recruiting for a phase 1 trial in advanced melanoma and other solid tumors. The antibody is TRX518 (NCT01239134). Merck is advancing a phase 1 study with the anti-GITR antibody MK-4166, although this trial (NCT02132754) is not yet recruiting patients. Review articles have mentioned an ongoing clinical program at MSKCC – this is one of the three sites enrolling patients in the TRX518 trial.

To the extent that the driving mechanism of action (MOA) of GITR stimulation is shown to be downregulation of Treg activity, this pathway should be a good candidate for combination therapy with 4-1BB, OX40 or CD27 agonists (see below) as well as with the CTLA4 and PD-1 pathway antagonists. If the MOA in human cancer patients is different or more complex than proposed, different combinations may be more or less attractive.

One last receptor – CD27.

The costimulatory molecule CD27 is constitutively expressed on most effector T cells, memory B cells, and an NK cell subset. So its expression may also overlap with those of the other receptors. CD27 appears to be important for sustained T cell effector function and also the development of T cell memory. CD27 is a marker of memory T cells, conversely, it is low or absent on Tregs. More broadly, CD27 supports germinal center formation that drives B cell maturation and the differentiation of plasma cells that produce high affinity antibodies, and is also important in driving the cytolytic activity of some NK cells.

Although there is a large preclinical literature on CD27 and its ligand CD70, there are few antibodies in clinical development. There are several historical explanations for this I think. CD70 is expressed at high levels on certain tumor types, particularly renal cell carcinoma (RCC). Much effort has gone into the development of cell-depleting antibodies targeting CD70. This expression pattern also called into question the relevance of CD27 in controlling tumor growth, as the ligand would be expected to stimulate immune responses. We now know that RCC and other solid tumors expresses high levels of PD-L1, and likely disables immune responses via this pathway. Not surprisingly then, one of the ongoing clinical efforts is a combination trial of nivolumab, the anti-PD-1 antibody from BMY with CDX-1127, an anti-CD27 antibody from Celldex (CLDX) in a collaboration announced by the 2 companies last week. In the meantime we have 2 abstracts from CLDX at ASCO in June to look forward to. In a 3×3 phase 1 dose escalation study of B cell lymphoma patients the drug was well tolerated with weekly IV dosing, and there were signs of clinical response, including a durable complete response in one patient with advanced refractory disease (abstract #3024; clinical trial NCT01460134). In the same trial, solid tumor patients were treated in a dose escalation phase and then an expansion phase (RCC and melanoma). The drug was well tolerated, there were preliminary signs of clinical response, and measureable activation of the immune system (Abstract #3027). With the potential to support memory T cell differentiation, CD27 may provide an important additional signal to drive long term tumor control. We’ll have to wait and see.

So, we have 4 receptors with overlapping activities and we have multiple antibodies in various stages of development. There will be plenty to learn about these targets and their roles in the future of combination immunotherapy. One of the most promising paths forward is the analysis of immune checkpoint and costimulatory proteins on tumor infiltrating lymphocytes (TILs). It seems very likely that the makeup of the tumor cell defense against the immune system will diverge between tumor types, and perhaps between patients with the same tumor types, or even with the same patient tumor at different times, or in different metastatic locations. Profiling TILs, and perhaps sentinel lymph nodes, for the expression patterns of lymphocytes and antigen presenting cells is likely to help guide combination therapy.

We’ll come back to that. And we’ve not forgotten those NK cells either.

stay tuned.

A Conversation with Agenus Leadership

Recently I had the opportunity to talk with Robert Stein, CSO and CMO, and Garo Armen, Chairman and CEO of Agenus Inc. (NASDAQ: AGEN). Agenus, formerly Antigenics, broke into the public eye earlier this year with their acquisition of 4-Antibody AG (4-Ab), a privately held European biotech. This week they announced a two-target deal with Merck, using the 4-Ab platform for the generation of novel antibodies to two undisclosed Merck checkpoint targets. These targets are in addition to the six internal checkpoint modulator programs, a quite positive development. This alone makes the company worth a look.

On the other hand a large Phase 3 trial of GSK’s MAGE-A3 vaccine in lung cancer failed, and this vaccine uses AGEN’s saponin-based adjuvant. That was certainly seen as a negative, although there are still 20 clinical programs using AGEN’s saponin-based adjuvant at GSK, Pfizer, and J&J, including GSK’s malaria vaccine that is heading toward Regulatory filing this year. While the company has its fans and detractors among stock analysts, our focus is on the science; so let’s see where that leads us. My conversation with AGEN leadership was wide-ranging but focused on the future of the company, particularly goals and near-term milestones.

I’ll start with the 4-Ab deal, which was touted in February for its transformational potential (adding checkpoint modulators to a vaccine company), and also financials, featuring a modest upfront with most of the value back-ended. The deal brought multiple immune checkpoint programs into AGEN- 6 programs in total. That’s quite a haul. Less well appreciated I think was the 4-Ab antibody platform, branded Retrocyte Display. The technology is interesting. According to the 4-Antibody website, Retrocyte (Retroviral B lymphocyte Display) is a “high throughput cellular antibody expression platform … to allow expression and screening of full-length immunoglobulin antibody libraries in mammalian B-lineage cells … Libraries of full length immunoglobulin heavy and light chains are encoded by separate retroviral expression vectors within B-lineage cells to yield efficiently and stably expressed fully human monoclonal antibodies on the surface of the B-lineage cells in the form of B-cell receptors. Retrocyte Display can be used to directly screen combinations of antibody heavy and light chain libraries for antigen-specific binders.”

This is the platform Merck sought to generate antibodies for two of their targets. Importantly the deal financially supports the R&D work that will be ongoing at AGEN to carry out their end of the collaboration. This is in addition to a potential $100 million in milestone payments and royalties on product sales. Considering that Merck brought proprietary checkpoint targets to the collaboration, participating in the upside is somewhat atypical. This deal makes a statement regarding how much Merck valued accessing the platform and of course it also sets the stage for future platform deals.

Back to those assets, Dr Armen stated quite clearly that the company will internally develop the first tier of antibodies acquired in the 4-Ab acquisition, with a stated goal of moving development candidates targeting CTLA4 and PD-1 and selected additional immune checkpoint modulator programs to IND filings with a target date of approximately 2 years. One of the uses of least some of the immune checkpoint modulators might be to “turbo-charge” the company’s long-standing tumor vaccine programs. These have certainly struggled to gain traction, as have nearly all vaccine plays in oncology, for reasons we now understand well – active immune suppression mediated by the highly adaptable tumor for its survival. Prophage is a personalized cancer vaccine based on patient-specific antigens isolated from each patient’s tumor, bound to heat shock proteins to drive the activation of anti-cancer T-lymphocytes. The company has been exploring the use of Prophage in patients with Glioblastoma Multiforme (GBM), influenced in part by the decision of the NCI to fund the ongoing Phase 2 trial. Over the years the company had conducted Phase 3 trials in melanoma, renal cell carcinoma, and earlier phase trials in multiple other cancers. AGEN is no longer advancing Prophage programs in these tumor types however they are participating in an investigator-sponsored clinical study of Prophage plus the checkpoint inhibitor Yervoy (the anti-CTLA-4 antibody ipilimumab from Bristol-Myers Squibb) in patients with advanced melanoma. Additional work could be done with their internal checkpoint modulator pipeline in the future. It is certainly true to say (although harder to predict) that positive results from the GBM trial would transform the company. I suspect that a failure here would lead the company to drop the platform.

It’s important not to confuse the Prophage tumor vaccine effort with the QS-21 Stimulon adjuvant programs. This is the adjuvant that GSK has licensed for use in much of their vaccine work. GSK’s MAGE-A3 vaccine failure is one of the few settings in which QS-21 was used as a tumor vaccine adjuvant. The company expects approvals for use in a malaria vaccine this year, with 20 advanced trials underway at GSK and J&J. GSK’s renewed emphasis on its prophylactic vaccine business might help AGEN even more going forward.  AGEN receives a milestone payment when the first QS-21 containing vaccine is registered by GSK and also royalties on both prophylactic and therapeutic vaccines.

If AGEN seems difficult to get one’s arms around, it may be because of this three-platform business model. On the other hand, these three platforms address three critical components of immune modulation, with immunotherapy programs a few years away from the clinic, a very long-standing vaccine effort, and an adjuvant program that is not well appreciated outside the company. Valuing this collection of technologies has been difficult, and certainly progress in any or all three will be important catalysts going forward.

Dr Armen and Dr Stein are well aware of the fuzzy picture that the outside world, and investors in particular I suppose, have had of the company. The refocus on immune checkpoint modulators was very well received allowing AGEN to raise $56M from  investors in February.  AGEN has articulated specific goals to drive the company forward:

  • Execute on the 4-Ab programs internally and through partnerships. This includes IND filings for two or more programs within 2 years, developing appropriate strategic partnerships, and further advancing other checkpoint inhibitors that were acquired with 4-Ab, but have not been disclosed.
  • Leverage the value of the 4-Ab platform, as has just been done in the Merck deal
  • Reboot the Prophage program via combination use with immune checkpoint modulators as results warrant. One cautionary note – this will require additional translational research efforts that are just now getting underway.
  • Design personalized therapeutic interventions utilizing the vaccine platform and an understanding of the basis for immune suppression in individual patients. AGEN leadership envisions that this will be done by a combination of internal efforts and through strategic partnerships with centers of excellence in translation medicine.
  • Acquire a later stage asset in the immune-oncology space that would complement the evolving immunotherapy portfolio. That could be a good use of capital.

It’s a full dance card. We’ll keep an eye on AGEN as they execute on these critical goals, especially in the immunotherapy space.

Disclosure: I own no stock in AGEN and have no opinion as to the value of the stock or its’ future performance.

Three high-altitude take aways from AACR14

The American Association for Cancer Research (AACR) 2014 meeting last week was high energy and high impact. We will dive into particular talks and specific pathways and indications in later posts, in the meantime I wanted to mention a few key themes.

1) Immunotherapy Versus The World.  That’s a deliberate overstatement of a subtle shift in emphasis from last year’s big meetings, where combinations of immunotherapy with just about anything else were the hot topic. This year there were several talks which emphasized the futility of chasing oncogenic pathways and all of their resistance mutations, one after the other, as opposed to letting the immune system do the work. However, it seems to me overly optimistic to believe that immune modulation can defeat a high percentage of patient  tumors on its own, as some speakers acknowledged. Combinations remain necessary although we will have to work past some notable failures in combo trials, such as the liver toxicity seen in the ipilimumab + vemurafenib combination phase 1, discussed briefly by Antonio Ribas               (see http://www.nejm.org/doi/full/10.1056/NEJMc1302338).

2) Immunotherapy Versus Itself.  In the ultimate battle of the titans, we see different immunotherapeutic modalities squaring off. This is a theme we’ve touched on before in this space, but the  competition is getting heated. In some indications, the leukemias, lymphomas, perhaps melanoma and some other solid tumors, there is an abundance of therapeutic choices, and the hard question of which therapy best suits which patient will ultimately need to be addressed outside of the context of clinical trial enrollment. Several talks really brought this message home. Roger Perlmutter of Merck (and before that, Amgen) envisions an important role for multiple immune therapies including bi-specific antibodies, chimeric antigen receptors (CARs), and immune checkpoint modulators like Merck’s anti-PD-1 antibody MK-3475.  For B cell lymphoma for example, there is blintumumab (Amgen), a potent bi-specific that redirects T cells to CD19+ tumor cells (and normal B cells), and there is CTL019, a CAR therapeutic which does much the same thing. The therapeutic profiles and toxicity differ, but the general idea is the same. One big difference is that while CTL019 drives T cell expansion and the development of long term anti-tumor memory, the bi-specific does not. Which is better? We don’t know yet. He did not mention that one might do well trying a course of BTK inhibition plus anti-CD20 antibody therapy, perhaps with restricted chemotherapy first e.g ibrutinib plus rituximab and chemo (R-BR or R-F). That choice comes down to efficacy, then toxicity, and eventually cost. Efficacy seems to be a home run with the CAR therapeutics, although these may run into trouble in the area of toxicity and cost calculation. Renier Brentjens discussed the CAR therapies being developed under the Juno Therapeutics umbrella. Acute lymphoid leukemia (ALL) can be treated with CAR 19-28z modified T cells to achieve a >80% complete response rate with >70% of patients showing no minimal residual disease, an outstanding result. However, 30% of treated patients end up in the ICU due to cytokine release syndrome and other toxicity, and recently patients in the ALL trials have died from unanticipated tox causes. Juno stopped 5 trials of their CAR technology last week due to toxicity. Apparently one patient died of cardiovascular complications and another of CNS complications (severe uncontrolled seizures) – it was hard to nail down as Dr Brentjens had gone off his prepared talk for these remarks which were off the cuff, so comment please if you have better info on this. Carl June discussed Dr Brentjens’ presentation, noting that the clinical results were really quite striking, and contrasting the CD28 motif-based CARs with the 4-1BB-based CARs (as designed by Dr June with U Penn and licensed to Novartis). He also stressed that in chronic lymphocytic leukemia (CLL) they have had patients who have failed up to 10 prior therapies, including rituximab and/or ibrutinib, and these patients have responded to CAR treatment. That’s very impressive data. The roadblocks to widespread use of CAR therapy however are large and include the toxicity, the “boutique” nature of the current protocols, the cost. Perhaps, Dr June suggested, CAR will end up as third line therapy, reserved for salvage therapy. I for one hope not.

Also in the immunotherapy space were hot new targets (e.g. CD47, OX40, GITR), advances on the vaccine front, and a few surprises. We’ll update soon.

3) The Medicinal Chemists Have Been Busy.  Not to be drowned out by the Immunotherapy tidal wave, small molecule therapies targeting specific oncogenic pathways continue to be developed and show promise. Most readers will be aware of the high stakes showdown (so billed) between Novartis, Pfizer and Lilly in the field of specific CDK4/6 inhibitors – in addition to bringing forward some really nice phase 2 data (we’ll discuss these another time) this “showdown” also illustrates that current portfolio strategy drives a lot of overlapping effort by different companies. As expected, much of the action is moving downstream in the signaling pathways, so we saw some data on MEK1 inhibitors and ERK1/2 inhibition. There were some new BTK inhibitors, nice advances in the epigenetics space, and some novel PI3K inhibitors. All grist for the mill.

stay tuned.

Hematological Malignancies – who will win the battle for patients? Part 2: BiTEs & CARTs targeting CD19

 We talked last time about the potential of Macrogenic’s DART bi-specific technology and we focused primarily on the T cell engaging bi-specifics, such as DART006, a CD3 x CD123 therapeutic. Lets just quickly state the hypothesis:

Bi-specific modalities will allow the targeting of the patients T-cell driven immune       system to a precise (tumor-expressed) antigen.

Other outcomes are possible. For example, the drugs might not work at all, or they might not be as specific as designed, or they act in ways we have not anticipated. In the context of the Macrogenics platform, we actually don’t know yet, as DART006 is very early in clinical development. BiTEs (Bi-specific T cell Engagers), Micromet’s version of a bi-specific technology, have been around a while and are further advanced. Acute Lymphocytic Leukemia (ALL) patients are now being recruited into Phase 3 clinical trials for blinatumomab, the anti-CD3 x anti-CD19 BiTE, with study completion due in July 2017. Micromet was acquired for 1.2BB dollars in January 2012 by Amgen. At the time Amgen R&D head Roger Perlmutter pointed to the Phase 2 clinical trial results in ALL as driving Amgen’s interest in the technology. Indeed, blinatumomab has produced some remarkable data in ALL. Historically, chemotherapy treated ALL patients had a complete response rate (CR) of about 38% and a median overall survival (OS) of 5 months. Rituximab (anti-CD20) didn’t perform much better than chemo. In the blinatumomab Phase 2 trial of adult relapsed/refractory (r/r) ALL, patients received a continuous IV infusion of blinatumomab for 28 days followed by 14-days off drug. Patients who responded could re-up for 3 more cycles of treatment or proceed to allogeneic stem cell transplantation (HCST). There was a very high rate CR of ~70% and the apparent absence of minimal residual disease (MRD) in many patients. Blinatumomab also impacted overall survival (OS) in ALL, as reported at the American Society of Hematology conference (ASH) in 2012 (Abstract #670). The CR was still 69% with most patients being MRD negative. The OS for responders was 14.1 months while the OS for non-responders was 6.6 months (so median OS = 9.8 months). Thirteen of the 36 patients enrolled were able to receive allogeneic HSCT.

The most common adverse events (AEs) were fever, headaches, tremors, and fatigue. Some patients experienced severe AEs (SAEs) such as cytokine release syndrome (CRS) and central nervous system events, including seizures and encephalopathy. One patient stopped treatment due to fungal infection leading to death. So, there is tox to consider.

A smaller study directed to salvaging patients with MRD despite prior treatments showed even more dramatic results: 16/21 patients became MRD negative and the probability for relapse-free survival was 78% at a median follow-up of 405 days. This is a remarkable result. An SAE led to one drug discontinuation.

Last year at ASH (Abstract #1811) we saw early results from an open label phase 2 study in r/r Non-Hodgkin’s Lymphoma (NHL), specifically, Diffuse Large B cell Lymphoma (DLBCL). Blinatumomab was administered by continuous IV for 8 weeks. Patients received either stepwise blinatumomab dosing of 9, 28, and 112 μg/d during weeks 1, 2, and thereafter, or received 112 μg/d throughout. All patients received prophylactic dexamethasone. So you can see some dose modifications here designed to reduce SAEs. After a 4-weeks off drug, patients who had responded could receive a 4-week consolidation cycle. 11 patients had been enrolled, 7 patients were evaluable for response. These patients had failed >2 prior therapies, including some patients who had relapsed after HSCT. The overall response rate (ORR) was 57% (14% CR plus 43% partial response (PR); 30% had progressive disease (all from the stepwise dose regimen). Note this is a very small sample size so every patient has a large impact on the response numbers. Ten of 11 patients had at least one grade ≥3 AE with 2 patients having grade 4 AEs (one patient with neutropenia and leucopenia; one with respiratory insufficiency). There were no drug related fatalities. Ten of 11 patients had central nervous system (CNS) AEs, mostly tremor, speech disorder and disorientation: in 5 patients these CNS toxicities were grade 3. The overall benefit/risk assessment suggested stepwise dosing (9, 28, 112 μg/d) to be the recommended dose.

Well first of all let’s point out here that blinatumomab has orphan drug status for ALL and NHL. That’s just to remind ourselves that these are pretty rare diseases with high unmet need. For ALL in particular this seems a good risk/benefit scenario. Within the diseases that make up NHL, DLBCL is not the most treatable (nor the least), and we note also that there is no attempt in the open-label phase 2 to characterize DLBCL into its subclasses – these have different oncogenic drivers and different outcomes for patients. Blinatumomab has also been in Phase in in other NHL classes, including Mantle Cell Lymphoma and Follicular lymphoma. Response rates were generally below current standard of care. Similarly, we can go back to look at rituximab, ofatumumab, and even ibrutinib, idelalisib and ABT-199 in NHL and likely find better treatment paradigms for r/rDLBCL than this, although maybe not as a monotherapy (see those earlier posts here: http://www.sugarconebiotech.com/?p=16).

Given the modality (CD3 x CD19 bi-specific) maybe the most interesting comparison is with Novartis’ CAR-T CD19 technology CTL019. CTL019 is the product of genetic engineering technology developed by Carl June’s group at U Penn, and is currently advancing in close to 20 clinical trials. The most advanced is a Phase 2 trial in r/r ALL, with a primary outcome completion due in July of 2015. As a quick reminder, CARs combine a single chain variable fragment (scFv) of an antibody (e.g. anti-CD19) with intracellular signaling domains from CD3 and 4-1BB into a single genetically engineered chimeric protein. The CD19-specific version of this technology is termed CTL019. Patient’s T cells are lentivirally transduced with a CAR, expanded ex vivo then infused back into the patient. Infusion of these cells results in 100 to 100,000x in vivo T cell proliferation, anti-tumor activity, and prolonged persistence in patients carrying CD19+ B cell tumors. Results from a pilot study in pediatric and adult r/r ALL were presented at ASH in 2013 (Abstract #67). Most patients received lymphocyte-depleting chemotherapy just a few days prior to infusion. This helps de-bulk the malignancy. In this small trial, 82% achieved a CR, 18% did not respond. Of the patients achieving CR, 20% subsequently relapsed. The rest of the patients are being followed and there has been no update. Responding patients all developed CRS, and about 30% of patients were treated with the IL6-receptor antagonist tocilizumab plus corticosteroids to control CRS symptoms.

We have a little more data on CTL019 from NHL studies, specifically r/r CLL. In December 2013, Phase 2 data were presented at ASH (Abstract #873).  Patients with r/r CLL received lymphocyte depleting chemotherapy and then one of several doses of transduced T cells (this is a dose study in that regard, although, cutting to the chase, no dose response was seen, so lets skip over that). Median follow-up for analysis was 3 months at which time the ORR = 40% (20% CR plus 20% PR, with clearance of CLL from the blood and bone marrow and at least a 50% reduction in lymphadenopathy. The toxicity profile was similar to that described above, dominated by treatable CRS. In a small Phase 1 study (Abstract #168), adult patients with r/r NHL including patients with chemotherapy-refractory primary mediastinal B cell lymphoma and DLBCL were enrolled. They received chemo to reduce disease burden and then an infusion of CTL019. 12 of 13 evaluable patients responded (ORR = 93%), the CR = 54% and PR = 38%. These are outstanding responses.

So let’s take a step back. It is a bit hard to compare these regimens head-to-head as they are in different stages of clinical development, the trails are generally small, and in the case of NHL, we have limited data on different types of lymphomas. At the same time we have to consider the larger landscape of therapies available, and ask ourselves how patients will best be served. In the case of the T cell engaging bispecific antibody landscape, it is very clear that robust anti-tumor responses are generated with very low concentrations of antibody. It seems to me very likely that there will be malignancies or subsets of malignancies where this technology will be very useful, including ALL, as we just saw. It will be important to either improve the antibody construction or alter the dose regimen sufficiently to reduce the toxicities associated with the BiTE therapeutic and competing modalities, including the DARTs. Now, people will claim that the tox is not so bad, and that it is only efficacy that matters, and that’s fine, but in the face of competition from CTL019 and other therapeutics, maybe this becomes a differentiating issue. This might also be different for the pediatric population (a critically important population in ALL) versus the adult population. When we look at the CAR T cell transduction technologies we need longer follow-up on the phase 2 studies but certainly anecdotal evidence from smaller trials suggests that some patients will experience long-lasting remissions. If this observational information holds up in the larger clinical trials than the technology will cement itself a place in ALL therapy, and perhaps in other diseases as well. We don’t know yet whether the BiTE therapeutic blinatumomab or the CAR therapeutic CTL019 will have a top-tier profile in NHL. This may change as more data become available, as some of the small studies are very encouraging. One of the interesting twists to the CAR technology is the question of how to make it widely available. In host-institutions (The U Penn system, MD Anderson, NCI) this is a centralized procedure, and in medical institutions world-wide, core patient cell facilities are commonplace. However it is rumored that Novartis at least wants to maintain the core facility model, as they picked up the Dendreon facility in Morris Plains New Jersey (at a bargain price) specifically to support CAR technology, and plan to duplicate those capabilities in Basel and in Singapore. Perhaps yesterday’s pickup of Israel’s Gamida Cell also plays into this centralized cell handling model. None of these complexities will bother the bi-specific therapeutics as these are injectable – that said, I’m not sure anyone will choose walking around with an IV pump for two months if they can avoid it.

So while these therapies and those like them are very potent, we will have to see how patients and providers ultimately use them.

Now, we’ve unfairly used blinatumomab and CTL019 to illustrate what are both pretty large areas of therapeutic development. We’ll come back to talk about the other players in the bispecific antibody and CAR spaces very soon.

stay tuned.