Category Archives: tumor stroma

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


The Tumor Microenvironment (TME) series to date is assembled here containing parts 1-3

I’m happy to point you to the most recent content, posted on Slideshare:

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.

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The Big Tent: Halozyme is Targeting the Tumor Microenvironment, part 3 of an occasional series.

Many drug development programs claim to be truly unique and novel. It’s a mixed message really – complete novelty implies (or ensures) a high level of risk. It’s a bit difficult to attract early investment to such programs and maintain investor interest going forward. When we work with companies raising money, or are raising money ourselves, we are constantly trying to minimize risks, plural, as risks represent diverse aspects of a program or company: technology risk, biology risk, clinical risk, commercial risk, to highlight just a few. Companies that can move novel programs forward while derisking them in multiple areas certainly warrant our attention – for the scientific thesis and the investment thesis. We recently wrote about Innate Pharma, a company with first-in-class programs targeting NK cell immune checkpoint pathways (link 1). This is a good example of a company that has shed biology and clinical risks as the partnership with Bristol-Myers Squibb (BMS) continues to grow. The entire second tier of antibody-drug conjugate linker/payload companies (Redwood, Igenica, Mersana, Catalent and many others) will remain technology risk-heavy until each individual company either secures partnerships that eventually move ADCs into the clinic, or get their themselves. We could go on and on.

A few weeks ago I asked for companies and programs targeting the tumor microenvironment. Among the responses I got these:

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william gerber HA

Halozyme (Nasdaq: HALO) has a lead program that is very novel and I think scientifically is very interesting and has understood biological risk. We’ll talk about other risk elements in a bit, but science first. PEGPH20 is a pegylated version of the company’s approved recombinant human hyaluronidase (rHuPH20; brand name Hylenex). Hylenex is licensed to several partners, and provides a steady income stream from royalties. Hyaluronidase catalyzes the random hydrolysis of 1,4-linkages between 2-acetamido-2-deoxy-b-D-glucose and D-glucose residues in hyaluronan (HA), a constituent of the ECM. Hyaluronidase increases tissue permeability and as used locally (sc) to improve drug distribution. In the systemic tumor setting we have the interesting hypothesis that some tumor types use HA to create a cell impermeable “wall” around tumor cells or the tumor mass. The best-characterized tumor in this sense is pancreatic cancer, which is encased in an ECM that resists penetration by therapeutics and cells.

HALO is running a Phase 1/2 clinical program in PEGPH20 in patients with previously untreated metastatic pancreatic cancer. A completed Phase 1 clinical trial assessed the safety and tolerability of PEGPH20 treatment in patients with solid tumor malignancies refractory to prior therapies. A Phase 2 trial, built off a Phase 1b run-in, is underway in metastatic pancreatic cancer. The cohorts are standard of care (gemcitabine) with PEGPH20 or with placebo. An on-target toxicity (muscle spasm/pain) was addressed in a trial in which patients were pre-dosed with dexamethasone. At ASCO 2013, HALO presented data from the Phase 1b clinical study of PEGPH20 in combination with gemcitabine for the treatment of patients (n=28, 24 evaluable) with previously untreated stage IV metastatic pancreatic ductal adenocarcinoma (link 2). Patients received doses of PEGPH20 (1.0, 1.6 and 3.0 µg/kg) twice weekly for four weeks, then weekly thereafter, in combination with gemcitabine, IV. The RECIST 1.1 ORR (overall response rate = complete response (CR) + partial response (PR)) was 42% percent at the two higher doses. Subsequent exploratory analyses suggested better progression free survival (PFS) and overall survival (OS) in patients with high levels of tumor HA compared to patients with low levels of tumor HA. This has led the company to embark on the development of a companion diagnostic to enable pre-selection of patients.

Other clinical studies include a Phase 2 multicenter, randomized clinical trial first-line therapy trial of PEGPH20 in patients with stage IV metastatic pancreatic cancer. Patients were randomized to gemcitabine plus nab-paclitaxel with or without PEGPH20. The primary endpoint is PFS. SWOG has sponsored a Phase 1b/2 randomized clinical trial of PEGPH20 in combination with modified FOLFIRINOX chemotherapy compared to mFOLFIRINOX treatment alone in patients with metastatic pancreatic adenocarcinoma. MSKCC is sponsoring a trial +/- cetuximab. A full trial list is shown here:

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In October (2014) the FDA granted Orphan Drug designation for PEGPH20 for the treatment of pancreatic cancer. OK, so what do we see here? The therapeutic hypothesis is compelling, that disassembling the tumor-shielding ECM will be helpful (see link 3). Would this work as monotherapy? Perhaps, but that is not being tested, since keeping standard of care (SOC) on-board is important for these patients. But if we consider the impact of a disrupted architecture, I think we would argue that monotherapy, or at least interesting combination therapies, could be considered. The mechanisms of action are complex and include physical disruption of the tumor microarchitecture, disruption of aberrant circulation and interstitial pressure in the tumor, disruption of zones of hypoxia, and other effects. Look at this figure from the preclinical study (pancreatic cancer, mouse model):

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Panel A shows the dosing regimen (with gemicitabine), B shows the impact on pressure within the tumor and C v D shows representative tumors from the control and treated animals. Another recent paper discusses the vascular effects in detail (link 4). With the obvious leakage and loss of tissue integrity it makes sense to argue for combination with chemotherapy or antibody therapy, as in the cetuximab combo trial show above, from the MSKCC. One might also postulate that the collapse in pressure and increased access to the interstitial space might allow better penetrance by lymphocytes, allowing consideration of immune checkpoint combinations. But lets look closer:

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I left the figure legend in place so I don’t have to repeat the details, which show a reduction in smooth muscle actin (A v B) and collagen (D v E). Basically this figure suggests that the structural elements of the tumor microenvironment have collapsed. Given the impact on ECM components, I would predict that  you would see adverse impact on myeloid cell populations, inducing the TAM and MDSC populations discussed earlier (another link). I’d have loved to see a panel with PEGPH20 alone as I’ll bet you would see some impact with the monotherapy.

So if we go back to our three-legged stool model…

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… now we are dead-on the microenvironment piece, and perhaps an obvious complement to the other 2 legs.

All well and good but the proof is in the clinic, and so is the risk. We talked about diverse risks earlier – here we have clinical risk (efficacy/toxicity) and commercial risk (is it good enough). HALO is presenting at the ASCO GI meeting with abstracts to come out from under embargo on January 12, 2015. The abstracts will include an update on the clinical trial NCT01453153, phase 1/2 +/- gemcitabine in metastatic pancreatic cancer. Presentation of median OS data is rumored (but n.b. I’ve not confirmed with the company). I’m excited by the prospects here, and hope we see some nice results…

… because the science makes sense.

stay tuned.

The Big Tent: Tumor Microenvironment Targets Heat Up – part 2 of an occasional series

I recently asked folks for their favorite hot targets in the tumor microenvironment space. Among a flurry of responses I got these two related answers:

mcbio CSF-1R

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These responses from @mcbio316 and @Festivus159 were very timely, given what happened 4 days later (and a big shout-out to mcbio, whose post had preceded this):

Bristol-Myers Squibb and Five Prime Therapeutics Announce Exclusive Clinical Collaboration to Evaluate the Combination of Investigational Immunotherapies Opdivo (nivolumab) and FPA008 in Six Tumor Types

Five Prime Therapeutics, Inc. November 24, 2014 8:59 AM GlobeNewswire

  • NEW YORK and SOUTH SAN FRANCISCO, Calif., Nov. 24, 2014 (GLOBE NEWSWIRE) – Bristol-Myers Squibb Company (BMY) and Five Prime Therapeutics, Inc. (FPRX) today announced that they have entered into an exclusive clinical collaboration agreement to evaluate the safety, tolerability and preliminary efficacy of combining Opdivo (nivolumab), Bristol-Myers Squibb’s investigational PD-1 (programmed death-1) immune checkpoint inhibitor, with FPA008, Five Prime’s monoclonal antibody that inhibits colony stimulating factor-1 receptor (CSF1R). The Phase 1a/1b study will evaluate the combination of Opdivo and FPA008 as a potential treatment option for patients with non-small cell lung cancer (NSCLC), melanoma, head and neck cancer, pancreatic cancer, colorectal cancer and malignant glioma. Bristol-Myers Squibb has proposed the name Opdivo, which, if approved by health authorities, will serve as the trademark for nivolumab.

So BMS will immediately move FPA008, but all measures an early stage and largely unproven therapeutic, into combination therapy trials with nivolumab for the treatment of solid tumors. Not to be outdone, Roche has already positioned it’s CSF1R targeted therapeutic, as noted by @jq1234t:

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There are a number of interesting questions to answer here: What does CSF1R do, why is it so interesting, how does it impact the tumor microenvironment, how are these trials being done and (a favorite of mine), who else has assets in development?

CSF1R is the receptor for macrophage-colony-stimulating factor (aka M-CSF or CSF-1). The receptor is a control node for macrophage differentiation. CSF1R also serves as a receptor for the monocyte survival factor IL-34. Although the ultimate outcome depends on many factors, signaling through CSF1R is necessary for myeloid lineage precursor cell differentiation into macrophages, and it is this feature that interests us in the tumor microenvironment setting. We cannot gloss over the fact that this is a pleiotropic and complex biological system but it is safe to say that by the time we are confronted by an immunosuppressed tumor (as in the case of combo therapy with anti-PD-1/PD-L1 therapeutics), our pathway focus is on tumor associated macrophages (TAM), their impact on the tumor microenvironment and their susceptibility to CSF1R-targeted therapy.

Roche poached this figure that I’m now borrowing (with fair reference to Chen and Mellman, 2013).

Roche version Cancer Immunity Cycle

In the original figure (see Immunity 39: – an open access article), Chen and Mellman placed the PD-1 pathway inhibitors with a variety of microenvironmental modulators (IDO1, Arginase, TGFb) that together prevent, in distinct ways, cancer cell death. The Roche version of the figure, reproduced above, has been modified to include CSF1R among other targets in the “killing cancer cells” category.

Broad strokes, what does this mean? TAM, the tumor associated macrophages mentioned above, are dependent on CSF1R signaling. TAM are myeloid lineage-derived cells that are co-opted by the resident tumor as part of it’s microenvironmental support system. TAM are potently angiogenic, remodel the stroma (extracellular matrix and related components) and are immunosuppressive. Among the plethora of critical factors produced by TAM we find the hypoxia response proteins and growth factors that drive angiogenesis, tissue remodeling and immunosuppression, i.e. HIF2a, MMP-9, EGF, VEGF and TGFbeta, cytokines that can maintain this response in a chronic state (IL-10, IL-4) and chemokines that attract myeloid cells and regulatory T cells (CCL22, CCXL8). The TAM population can be directly regulated by tumor cell secretion of CSF-1, thus the importance of the CSF1R target. Multiple labs have produced preclinical data showing that anti-CSF1R antibody therapy can rapidly and effectively deplete tumors of the TAM population, and that this depletion has an impact on tumor growth and survival.

Clinical development to date is scattered. The FPRX program began with a Phase 1 trial in healthy volunteers and rheumatoid arthritis patients (NCT01962337) reflecting the role of diverse macrophage populations in inflammation and autoimmunity. Indeed the FPRX website states “we are currently conducting nonclinical research in areas such as idiopathic pulmonary fibrosis, lupus nephritis and other inflammatory disorders to identify a second target indication by the end of 2014″ although this may be trumped by the BMS deal. That trial reported safety and pharmacodynamic endpoints at AACR earlier this year. FPA008 was well-tolerated at all dose levels tested and the drug impacted inflammatory macrophage numbers and, interestingly, bone turnover (this latter effect due to the control of osteoclast differentiation by CSF1R, an important feature in bone metastasis settings perhaps).

In contrast Roche has been testing it’s antibody in a rare disease (a form of giant cell tumor) that is caused by a  t(1;2) translocation resulting in fusion of COL6A3 and M-CSF genes encoding for CSF1. The tumor is characterized by CSF1R+ cells. Roche reported that RG7155 had the following activities (Reis et al. 2014. Cell 25: 846–859):

- Anti-CSF-1R antibody depletes tumor-associated macrophages in cancer patients

- CSF-1R inhibitor shows clinical activity in diffuse-type giant cell tumor patients

- CSF-1R signaling inhibition increases lymphocyte infiltration in cancer patients

That last highlight referring to an effect on immunosuppression and refers to a relative increase of CD8+ T cells versus CD4+ FoxP3+ T regulatory cells, thus feeding the enthusiasm for combination therapy with anti-PD-1/PD-L1 therapeutics. More data is available in their ASCO abstract (

Other clinical stage antibodies include IMC-CS4 from Eli Lilly, in Phase 1 for advanced solid tumors (NCT01346358), ARRY-282 from Array BioPharma and Celgene, which had completed a Phase 1 trial in advanced solid tumors (NCT01316822) before the program was terminated, AMG 820 from Amgen with a completed Phase 1 study in advanced malignancies (NCT01444404), and others. Preclinical programs are visible at many small companies, both private and public, and include small molecule inhibitors of the receptor, e.g the Ambit and Plexxikon programs.

While the enthusiasm seems warranted by the preclinical modeling data and the (to date) apparent tolerability of the antibody therapies, I did receive this one note of caution from @Boston_Biotech:

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Nuances, indeed. It is important to consider a few possible issues. First, blockade of CSF1R in mice led to the pronounced and sustained upregulation of CSF-1, and drug doses had to be kept high in order to “drug-through” this level of ligand to block the receptor. Rebound activity at trough or upon drug cessation could be a big problem, as has been described for other systems, including CCL2 blockade in breast cancer models (leading to abundant metastasis). Sticking with breast cancer, it has been reported that blocking CSF1R leads to upregulation of GM-CSF signaling, changing the composition perhaps (but not the stability) of the tumor microenvironment. Finally, as always, we cannot yet see what efficacy drugs will have as monotherapies (its too early) while we race ahead to combo therapies. While its all hands on deck to get these assets into patients, they won’t all work and certainly can’t be sure they will do no harm. However, that said, I think targeting components of the tumor microenvironment, including TAM, is our next best step forward, and I certainly will enjoy watching the data unfold.

next time … what wraps pancreatic cancer up so tight that you can’t treat it until it explodes in a deadly metastasis fireball?

cool stuff.

The Tumor Microenvironment – A Big Tent

 We have talked repeatedly about the promise of immuno-oncology, and with good reason. Very recent data show that the landscape of cancer care is changing rapidly and dramatically for the better. We continue to see contributions from diverse therapeutic modalities: immune checkpoint modulation, novel antibodies, bispecifics, CAR T therapy, TCR therapy and others. Massive amounts of resources have poured into this space, and interesting new companies continue to launch in the Boston area: Surface, Unum, Potenza, Enumeral to name just a few.

The last decade has seen intense focus on the immune checkpoint field, and clinical development in that space is encompassing combination therapy as the defining principal to advance treatment (Mahoney et al. NRDD, submitted). While much of the effort is driven toward combining antagonists of T cell immune checkpoints (CTLA4, PD-1, TIM-3, etc) with T cell activators (4-1BB. OX40, CD27, etc), this approach may be self limiting due to the toxicity associated with hyper-activation of T cells (cf. CAR Ts and BiTES) alongside the limitation of targeting just one arm of the immunosuppressive armature deployed by tumors.

Further, we understand that affecting outright cures in more patients is a dramatic step change, and we are not there quite yet, outside of hematology perhaps. It is obvious (we think) that curing cancer will require taking down the infrastructure that supports tumor cell survival, proliferation, resistance and metastasis. For solid tumors and niche-homing leukemias/lymphomas this infrastructure is built on the foundation of tumor cell/stroma interaction, where we define the stroma as extracellular matrix and associated cells – tumor associated macrophages (TAM), myeloid-derived suppressor cells (MDSC), tumor associated fibroblasts, endothelium, other mesenchymal-lineage cells, etc. The composition may vary from indication to indication, with more or less complexity.

Let’s set the stage using three biology buckets:

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Immuno-oncology focuses intently on tumor cells and tumor-expressed antigens, and on lymphocytes and the mechanisms by which they are shut down by tumor-mediated immunosuppression. Indeed, the current clinical immunotherapy data set is comprised primarily of measured T cell responses, in particular CD8+ T cell responses, with emerging respect for the role of NK cells (see, for example, the lirilumab post). We have not yet developed the readouts needed to accurately assess the role of microenvironmental cells and their soluble mediators but that’s not to say these elements are not be targeted.

It’s certainly true that some of the traditional approaches to cancer treatment impact components of immunity. Cytotoxic therapy (chemotherapy, irradiation) has the demonstrable effect of increasing antigen presentation by inducing tumor cell death and membrane disruption. Chemotherapeutics like cyclophosphamide have been shown in some tumor types to induce the cell surface expression of HLA, a molecule that is often specifically downregulated by tumor cells as a mechanism of avoiding recognition by CD8+ T cells and NK cells. Taxane based chemotherapeutics can induce dendritic cell (DC) activity and induce the local production of pro-inflammatory cytokines. Gemicitabine, until recently the standard chemotherapeutic for pancreatic cancer, induces DC maturation, induces antigen expression on tumor cells, and, of particular interest, reduces the MSDC “burden” within tumors. We stress this last activity as the accumulated data to date suggest that in nearly all tumor settings immunosuppression trumps immune activation, meaning that DC activation, epitope production and cytokine expression is for naught if overriding suppressive signals are not reduced.

Another interesting example is BRAF inhibition. Jennifer Wargo’s lab at MGH has published extensively on this subject. Critical observations from that group and others were recently summarized, and here we quote from their recent review:

“Oncogenic BRAF contributes to immune escape through … establishing an immunosuppressive tumor microenvironment. The administration of a BRAF inhibitor promotes clinical responses along with an increased expression of melanoma-differentiation antigens by malignant cells, an increased tumor infiltration by CD8+ T cells, and a decreased production of immunosuppressive cytokines such as interleukin (IL) -6, IL-8 and IL-1α as well as of the angiogenic mediator vascular endothelial growth factor (VEGF). This phenotype is reverted at time of disease progression. Importantly, the expression of immunomodulatory molecules on T cells (e.g., PD1) and on tumor cells (e.g., PDL1) is also increased within 14 d of BRAF-targeted therapy initiation.” (Cooper et al. 2013. OncoImmunology 2:5, e24320).

This review also makes the very interesting claim that targeting further downstream from BRAF, e.g. with MEK inhibitors, is less beneficial to the immune response because of a direct negative effect on T cells. These data were accumulated in studies of melanoma, but may be more broadly applicable. We’ll come back to BRAF inhibition in but suffice to say there are combination trials of immune checkpoint inhibition with BRAF and MEK inhibitors underway.

Another interesting class of traditional inhibitors with described impact on anti-tumor immune responses are the growth factor targeting agents, notably VEGFR inhibitors. For example sunitinib, a VEGFR inhibitor and a standard therapy for patients with metastatic renal cell carcinoma (RCC) blocks growth factor signaling in tumor and vascular cells to disrupt tumor-induced angiogenesis. Sunitinib also reportedly reduces the accumulation of myeloid-derived suppressor cells (MDSC) and the number of T regulatory (suppressive) T cells within tumors. Diverse types of VEGF pathway inhibitors are now in clinical trials with immune checkpoint inhibitors like nivolumab (anti-PD-1, BMY).

A few days ago I pooled readers for their favorite “tumor microenvironment” targets. The response was interesting for it’s diversity of approaches and companies. Here are some very good ones:

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So we have targets, a company (AstraZeneca), a link to a Science TM paper – all in 144 characters. Also included was the a slide from an AZN presentation about the paper.

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The subject of the paper is a specific tumor type, rhabdomyosarcoma (RMS), the most common childhood soft tissue sarcoma (Highfill et al. 2014. Sci Transl Med 6: 237). In a mouse model, RMS tumors were notable for selective recruitment and/or expansion of CXCR2+ MDSC, which mediate local immunosuppression, while inhibiting or blocking inflammatory CD11b+ macrophages. CXCR2 is a chemokine receptor, and chemokines and their receptors are cell attraction gradients widely used in normal and diseased tissue to “pull” cells into the appropriate environment at the right time. CXCR2 gene-deficiency, or anti-CXCR2 monoclonal antibody therapy, enhanced an anti-PD1 antibody-induced anti-tumor immune response and anti-tumor efficacy, informing the design of the clinical trial mentioned in the slide above. AZD5069 has been profiled extensively in inflammatory diseases, and has quite a good tolerability profile. The GlaxoSmithKline (GSK) inhibitor reparixin blocks binding of the chemokine CXCL8 to both it’s receptors, CXCR1 and CXCR2. GSK has positioned this therapeutic as a method of targeting cancer stem cells, which are inherently mobile and rely of chemokine receptors to exit the primary tumor and find suitable host sites for metastasis. Reparixin has been tested in a variety of chronic inflammatory and tissue injury models like acute lung injury and COPD. More recently, a variety of tumor types are being targeted with this drug in clinical trials. The use of riparixin with chemotherapy is being pursued in breast cancer and pancreatic cancer.

Interest in these targets has also grown with the appreciation that chemokine inhibitors can be used in the context of chemotherapy to “flush” tumor niches like the bone marrow and lymph nodes by disrupting chemokine gradients. A good example of this type of gradient is SDF-1 and CXCR4, a target picked out by Dan Marks aka @Festivus159:

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We’ll come back to that other target (CSF-1R) later. CXCL12 is the official designation for SDF01, mentioned above as the ligand for CXCR4. The approach is validated by the use of plerixafor (AMD3100, Genzyme), a small molecule CXCR4 inhibitor, and ulocupumab (aka BMS-936564/MDX-1338, from BMS), a fully human anti-CXCR4 antibody. These therapeutics are used to treat hematological malignancies, especially in the context of bone marrow invasion by the tumor cells. Plerixafor is approved as Mozobiltm). The bone marrow is an exquisite example of a tumor-supportive niche as it is highly vascularized, rich in adhesion pathways that can be hijacked to induce pro-survival signaling, and readily remodeled to accommodate tumor-specific stromal interactions.

CXCR4 is an interesting target, and there are now multiple companies pursuing diverse therapeutics targeting this receptor. A quick search of the American Society of Hematology meeting abstracts for this year reveal a new antibody from Pfizer and a peptidic antagonist from Eli Lilly in clinical development, with other compounds coming along behind.

A lesser-appreciated role for CXCR4 is articulated in the preclinical and translational medicine literature, in which the critical role of CXCR4 in glioblastoma, ovarian cancer, renal cell carcinoma and other solid tumors in detailed. In this setting the role of CXCR4 as a critical regulator of immune suppression within the tumor microenvironment has been revealed. Specifically, CXCR4 inhibition has been shown to block recruitment of regulatory T cells, block recruitment and retention of MDSC and a newly appreciated stromal suppressor cell, the FAP+ tumor-associated fibroblast, thereby reducing immune suppression. Reviews from Doug Fearon and colleagues cover this biology in detail (e.g. Fearon 2014. Immunol Res2;187).

In part 2 we will look at ideas sent in by @JSWatercooler, @PaulyDeSantis, @WilliamGerber1, @zDonShimoda, @csr1223, @mcbio316, @AZBiomarkers and others.