Inhibition of LILRB2 by a Novel Blocking Antibody Designed to Reprogram Immunosuppressive Macrophages to Drive T Cell Activation in Tumors

Tumor-associated macrophages (TAMs) play an important role in maintaining the immunosuppressive state of the tumor microenvironment (TME). High levels of CD163+ TAMs specifically are associated with poor prognosis in many solid tumor types. Targeting TAMs may represent a key approach in development of the next generation of cancer immune therapeutics. Members of the leukocyte immunoglobulin-like receptor B (LILRB) family, including LILRB2 (ILT4), are known to transmit inhibitory signals in macrophages and other myeloid cells. Leveraging bulk and single cell RNAseq datasets, as well as extensive immunophenotyping of human tumors, we found that LILRB2 is highly expressed on CD163+ CD11b+ cells in the TME and that LILRB2 expression correlates with CD163 expression across many tumor types. To target LILRB2, we have developed JTX-8064, a highly potent and selective antagonistic monoclonal antibody. JTX-8064 blocks LILRB2 binding to its cognate ligands, including classical and non-classical MHC molecules. In vitro, JTX-8064 drives the polarization of human macrophages and dendritic cells toward an immunostimulatory phenotype. As a result, human macrophages treated with a LILRB2 blocker are reprogrammed to increase the activation of autologous T cells in co-culture systems. Furthermore, JTX-8064 significantly potentiates the activity of anti-PD-1 in allogeneic mixed lymphocyte reaction. In a human tumor explant culture, pharmacodynamic activity of JTX-8064 was observed in monotherapy and in combination with anti-PD-1. Collectively, our work provides strong translational and pre-clinical rationale to target LILRB2 in cancer.

First-in-Human Phase I/II ICONIC Trial of the ICOS Agonist Vopratelimab Alone and with Nivolumab: ICOS-High CD4 T-Cell Populations and Predictors of Response

PURPOSE

The first-in-human phase I/II ICONIC trial evaluated an investigational inducible costimulator (ICOS) agonist, vopratelimab, alone and in combination with nivolumab in patients with advanced solid tumors.

PATIENTS AND METHODS

In phase I, patients were treated with escalating doses of intravenous vopratelimab alone or with nivolumab. Primary objectives were safety, tolerability, MTD, and recommended phase II dose (RP2D). Phase II enriched for ICOS-positive (ICOS+) tumors; patients were treated with vopratelimab at the monotherapy RP2D alone or with nivolumab. Pharmacokinetics, pharmacodynamics, and predictive biomarkers of response to vopratelimab were assessed.

RESULTS

ICONIC enrolled 201 patients. Vopratelimab alone and with nivolumab was well tolerated; phase I established 0.3 mg/kg every 3 weeks as the vopratelimab RP2D. Vopratelimab resulted in modest objective response rates of 1.4% and with nivolumab of 2.3%. The prospective selection for ICOS+ tumors did not enrich for responses. A vopratelimab-specific peripheral blood pharmacodynamic biomarker, ICOS-high (ICOS-hi) CD4 T cells, was identified in a subset of patients who demonstrated greater clinical benefit versus those with no emergence of these cells [overall survival (OS), P = 0.0025]. A potential genomic predictive biomarker of ICOS-hi CD4 T-cell emergence was identified that demonstrated improvement in clinical outcomes, including OS (P = 0.0062).

CONCLUSIONS

Vopratelimab demonstrated a favorable safety profile alone and in combination with nivolumab. Efficacy was observed only in a subset of patients with a vopratelimab-specific pharmacodynamic biomarker. A potential predictive biomarker of response was identified, which is being prospectively evaluated in a randomized phase II non-small cell lung cancer trial. See related commentary by Lee and Fong, p. 3633.

Phase 2 study of PD-1 inhibitor JTX-4014 alone and in combination with vopratelimab, an ICOS agonist, in biomarker-selected subjects with metastatic NSCLC after one prior platinum-containing regimen (SELECT)

TPS9137

Background: Immune checkpoint inhibitors have led to durable remissions for some patients with advanced malignancies, including NSCLC; however, only a minority of patients benefit. The field of oncology is addressing this via the development of novel therapies, combinations and identification of biomarkers to select patients most likely to derive clinical benefit. ICOS, a novel therapeutic target, is a costimulatory molecule upregulated on activated T cells. Vopratelimab is an investigational IgG1 ICOS agonist monoclonal antibody that results in activation and proliferation of primed CD4 T effector cells. The preliminary efficacy of vopratelimab +/- nivolumab was assessed in the phase 1/2 ICONIC study in which durable responses were observed in a subset of patients who demonstrated on treatment emergence of peripheral ICOS hi CD4 T effector cells. Patients with peripheral ICOS hi CD4 T cells achieved significantly greater clinical benefit than patients whose CD4 T cells remained ICOS lo. An RNA based tumor inflammation signature (TIS) comprised of 18 genes associated with immune cell infiltration was previously identified as a predictive biomarker of response to anti-PD-1 therapy (Ayers et al, 2017); it was also associated with ICOS hi CD4 T cell emergence in ICONIC (ASCO-SITC 2020). The pre-treatment tumor TIS score, coupled with a specific threshold established by Jounce, referred to as TISvopra, was predictive of ICOS hi CD4 T cell emergence. TISvopra positive patients had improved RECIST response, PFS, and OS compared to those with a TISvopra negative score. Therefore, we hypothesize that patient selection by TISvopra will identify those who will display emergence of ICOS hi CD4 T cell populations and importantly, improved clinical outcomes when treated with vopratelimab in combination with JTX-4014 (a novel PD-1 inhibitor in development by Jounce) vs JTX-4014 alone. Methods: This Phase 2 open-label multicenter study is investigating JTX-4014 alone and in combination with vopratelimab in TISvopra selected patients with metastatic NSCLC after one prior platinum-containing regimen (NCT04549025). Patients must be PD-1/L1 inhibitor naïve and negative for activating EGFR mutations. TISvopra eligibility is determined using RNA isolated from a tumor sample. Eligible patients will be randomized to receive either JTX-4014 as monotherapy or in combination with one of two dose levels of vopratelimab. The primary endpoint is mean percent change from baseline tumor size of all measurable existing and new lesions averaged over 9 and 18 weeks. Secondary endpoints include ORR and PFS according to RECIST v1.1, OS, safety, and association of baseline TIS score with clinical outcomes. The study has a target enrollment goal of approximately 75 patients; the first patient was dosed October 2020. Clinical trial information: NCT04549025.

Abstract 5536: ICOS hi CD4 T cells emerging on vopratelimab treatment have Th1 central memory characteristics and may contribute to durability of clinical responses

Background: Inducible T cell Co-stimulator (ICOS) is a costimulatory molecule expressed primarily on T lymphocytes that is upregulated upon cell activation. Vopratelimab (vopra) is a novel ICOS agonist antibody whose primary mechanism of action is the stimulation of primed CD4 T effector cells. Clinical responses in the Phase 1/2 ICONIC trial (NCT02904226) were associated with the emergence of ICOS hi CD4 T cells. In a separate study of PD-1/L1 monotherapy, this phenotype was not observed, demonstrating ICOS hi CD4 T cell emergence in ICONIC was due to vopra. Ex vivo stimulation of antigen-primed ICOS hi CD4 T cells by soluble vopra demonstrated induction of a polyfunctional cytokine response. Previous studies have shown that sustained ICOS upregulation was associated with clinical benefit in subjects treated with anti-CTLA-4 inhibitors, with preclinical data confirming a role for ICOS signaling in optimal anti-tumor activity. Vopra is currently being tested as a sequenced combination with ipilimumab (ipi) in the Phase 2 EMERGE trial (NCT03989362).

Methods: Assessment of phenotype and function of ICOS hi CD4 T cells was conducted using serial collections of peripheral blood mononuclear cells (PBMCs) from a subset of evaluable subjects in the ICONIC trial. A mouse syngeneic tumor model was developed to assess the kinetics of ICOS hi emergence as well as determine functionality and combination efficacy. Biological activity was assessed through ex vivo functional assays, with phenotypic assessments by flow cytometry-based profiling and genomic analysis.

Results: Phenotypic profiling of ICOS hi CD4 T cells demonstrated a T central memory phenotype with Th1 characteristics, and ICOS hi CD4 T cells increased as a % of the CD4 compartment longitudinally. Potent effector molecules, including perforin and granzyme, were significantly upregulated in isolated ICOS hi CD4 T cells relative to ICOS lo CD4 T cells from subjects. In a syngeneic tumor-bearing mouse system, ICOS hi CD4 T cells were induced in lymphoid organs following ipi treatment, with emergence detectable at day 3 and peaking at day 7 post-treatment, where up to 40% of CD4 T cells were ICOS hi. Relative to monotherapy, enhanced anti-tumor efficacy was observed in mice treated with combination ICOS agonist and ipilimumab.

Conclusion: Emergence of a peripheral ICOS hi CD4 T cell population correlates with response to vopra treatment and occurs independent of anti-PD-1 activity. Transcriptional profiling of ICOS hi CD4 T cells further defined the phenotype as Tcm cells that express cytotoxic effector molecules, which may contribute to observed clinical benefit. Treatment with ipi in combination with an ICOS agonist resulted in enhanced efficacy in mice, and follow-up studies exploring sequential dosing are ongoing.

Citation Format: Amadna Hanson, Abha Daneshwar, Heather Cohen, Yasmin Hashambhoy-Ramsay, Kristin O'Malley, Krithi Bala, Lara McGrath, Kristen Leone, Courtney Hart, Rachel McComb, Johan Baeck, Ellen Hooper, Elizabeth Trehu, Haley Laken, Monica Gostissa, Christopher Harvey. ICOS hi CD4 T cells emerging on vopratelimab treatment have Th1 central memory characteristics and may contribute to durability of clinical responses [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5536.

Association of an RNA signature (RS) with emergence of ICOS hi CD4 T cells and efficacy outcomes for the ICOS agonist vopratelimab (vopra) and nivolumab (nivo) in patients (pts) on the ICONIC trial

14

Background: ICOS is a costimulatory molecule upregulated on activated T cells. Vopra is an investigational ICOS agonist antibody that results in activation and proliferation of primed CD4 T effector cells. Vopra was assessed in heavily pretreated patients with advanced solid tumors as monotherapy (mono) or in combination with nivolumab (nivo) in the Phase 1/2 ICONIC trial (NCT02904226). Emergence of a distinct ICOS high (hi) population of peripheral CD4 T effector cells, not seen with PD-1 inhibitors alone, was associated with improved ORR, PFS and OS with vopra mono and combo therapy (AACR 2019). Baseline tumor and blood biomarkers were assessed for ability to predict ICOS hi CD4 T cell emergence and clinical outcomes. Methods: Fresh pre-treatment tumor biopsies were assessed by RS, a gene signature describing immune cell infiltration, and other biomarkers, including PD-L1 TPS by IHC. Pts were classified as RS1 and RS2 based on medium and high cutoffs. Associations between potential predictive biomarkers, ICOS hi CD4 T cell emergence and clinical outcomes were evaluated. Results: Baseline RS is significantly higher in patients with emergence of ICOS hi CD4 T cells. High RS was associated with increased emergence of ICOS hi CD4 T cells, accompanied by improved RECIST response, PFS, and OS. In contrast, no association was noted with PD-L1 IHC. Clinical trial information: NCT02904226. Conclusions: In this retrospective subset analysis, the RS score, but not PD-L1, in baseline tumor biopsies was predictive of emergence of an ICOS hi CD4 T cell population and improved RECIST response, PFS, and OS in patients treated with vopra alone and in combination with nivo. Clinical evaluation of vopra and investigational PD-1 inhibitor JTX-4014 in cancer patients with RS selection is planned. [Table: see text]

Abstract 5007: Preclinical evaluation of JTX-8064, an anti-LILRB2 antagonist antibody, for reprogramming tumor-associated macrophages

Introduction: Jounce has generated cell type-specific gene signatures as a means of probing The Cancer Genome Atlas and other large datasets to identify targets that may be important immune checkpoints. Using a tumor-associated macrophage (TAM) gene signature, we have found a strong correlation and coherence between TAMs and LILRB2 (leukocyte immunoglobulin like receptor B2; ILT4) across multiple tumors types. LILRB2 is a myeloid cell surface receptor containing four extracellular immunoglobulin domains, a transmembrane domain, and three cytoplasmic immunoreceptor tyrosine-based inhibitory motifs (ITIMs). Ligation of LILRB2 on myeloid cells, via its endogenous ligands (classical MHC I molecules [e.g. HLA-A, HLA-B] and non-classical MHC I molecules [e.g. HLA-G]), provides a negative signal that inhibits stimulation of an immune response. HLA-G is recognized as an important immunosuppressive molecule playing a role in maternal-fetal tolerance and being overexpressed in cancer - often associated with advanced disease stage and poor prognosis. As tumor-associated macrophages are known to suppress the anti-cancer immune response, these findings provide rationale for targeting LILRB2.

Methods and Results: We have generated a panel of monoclonal antibodies that bind specifically to LILRB2, but not other LILR family members, and can block binding of LILRB2 to MHC I molecules (i.e. HLA-A and HLA-G). In vitro differentiated monocyte-derived macrophages (MDMs) cultured for 24h in the presence of anti-LILRB2 antibodies and lipopolysaccharide (LPS) show polarization toward a more inflammatory phenotype - secreting higher levels of TNF-α and IL-6 with decreased amounts of IL-10 and CCL2 as compared to an isotype control antibody. NanoString mRNA analysis revealed that, in the absence of LPS or any additional stimuli, MDMs cultured with anti-LILRB2 antibodies showed gene changes consistent with inflammatory or M1-like polarization of macrophages. Anti-LILRB2 antibodies were also evaluated in human tumor histoculture and induced pharmacodynamic responses consistent with macrophage and T cell activation in a variety of tumor types. While mice do not express LILRB2 specifically, they do express a LILRB-like molecule known as Pirb. Mice that are deficient in Pirb display resistance to mouse colon 38 (MC-38) tumor growth suggesting this pathway functions as immune checkpoint in cancer.

Conclusions: Based on these preclinical data, JTX-8064, a high affinity LILRB2-specific humanized antagonist monoclonal antibody, is being developed as an immunotherapeutic to reprogram suppressive macrophages within the tumor microenvironment.

Citation Format: Heather Cohen, Yasmin Hashambhoy-Ramsay, Lauren R. Pepper, Jeffrey Y. Smith, Margaret Willer, Kevin Guay, Vikki Spaulding, Kristin O'Malley, Monica Gostissa, Abha Dhaneshwar, Edward C. Stack, Alessandro Mora, Donald R. Shaffer. Preclinical evaluation of JTX-8064, an anti-LILRB2 antagonist antibody, for reprogramming tumor-associated macrophages [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5007.

Abstract 700: Development of a second-generation TRAIL agonist and predictive biomarker profile for colorectal cancer

In colorectal cancer (CRC), RAS mutated cancers comprise 30-50%, for which there are limited treatment options. Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) has been found to selectively induce cell death in 50% of the CRC cell lines tested in vitro and this appears to be independent of RAS mutation status. Minimal clinical success was observed for first generation TRAIL receptor agonists primarily due to poor agonist activity and poor bioavailability. In addition, a biomarker to identify responsive patients was lacking. Here we present the therapeutic development of MM-201, a next generation TRAIL receptor agonist, and its companion biomarker strategy. MM-201 is composed of an IgG1 Fc fused to a single chain TRAIL trimer (Fc-scTRAIL) engineered for improved stability and activity. Using TRAIL surface display on yeast, we identified three mutations (R130G/N228S/I247V) from a random mutagenesis library that lead to enhanced surface expression and DR5 binding. Incorporation of these three mutations into each TRAIL protomer of MM-201 resulted in an improvement of greater than 10°C in TM and an extended serum half-life of 33 hours in mice compared to wild-type Fc-scTRAIL and comparable activity in a panel of colorectal cancer (CRC) cell lines. To uncover predictive biomarkers for MM-201, we used continuous logic gate analysis on a publicly available dataset of cell survival for 27 CRC cell lines treated with cross-linked TRAIL cytokine. Using this dataset and gene expression data from Cancer Cell Line Encyclopedia, we explored combinations of 33 differentially expressed genes in the apoptosis pathway and identified a two gene biomarker signature that positively correlated with TRAIL response in CRC cell lines. The combined signature of high DR4 and low cIAP-1 was identified with a correlation coefficient of 0.99 with MM-201 response across 15 CRC cell lines both in vitro and in vivo. Subsequently we evaluated MM-201 and our biomarker approach in vivo, in a group of five CRC patient-derived xenograft (PDX) models. Four of the five models were sensitive to MM-201, with an average tumor growth inhibition (TGI) of 91%. The relative expression of DR4 and cIAP-1 in each of the PDX models was measured by RT-qPCR and the biomarker scores were observed to be significantly higher for all responding models. Given the responses observed in preclinical models, we used TCGA data to assess biomarker prevalence in patient tumor tissues. This analysis predicted that 59% of samples would have a biomarker score greater than 0.5, which correlates to a 75% reduction in cell viability in vitro. In contrast, only 12% of normal tissues had a score in this range. Our biomarker signature identifies a potentially responsive patient population and when combined with our next generation TRAIL agonist, MM-201, has the potential for development in CRC, especially for RAS mutated cancers.

Citation Format: Sara Ghassemifar, Yasmin Hashambhoy-Ramsay, Haluk Yuzugullu, Tamara Utermark, Violette Paragas, Tim Maiwald, Lia Luus, Maja Razlog, Hannah Hudson, Diane Chai, Birgit Schoeberl, C. Patrick Reynolds, Peter Sorger, Andrew J. Sawyer, Daryl C. Drummond, Eric Tam. Development of a second-generation TRAIL agonist and predictive biomarker profile for colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 700.

Abstract 22: MM-161, a first-in-class pan-FGFR antibody

Aberrant signaling of the FGFR pathway has long been known to promote tumorigenesis and angiogenesis across multiple cancer indications. However, the development of an effective and well-tolerated FGFR targeted inhibitor has been hindered by the need to block the activation of multiple mitogenic receptors while avoiding significant toxicities associated with blocking endocrine FGF ligands.

Here we disclose for the first time a novel FGFR targeted antibody, MM-161, designed to block ligand-dependent signaling driven by all four FGF receptors, specifically the IIIc-isoforms. MM-161 is well tolerated in mice and cynomolgus monkeys with no significant weight loss observed in either species. Efficacy studies demonstrated that MM-161 monotherapy leads to significant tumor growth inhibition or tumor regression of xenografts of human lung, renal and endometrial cancer amongst others. Importantly, MM-161 has a dual mechanism of action by inhibiting both proliferation and angiogenesis. We will present data illustrating that inhibition of multiple FGFRs is desirable to achieve tumor regression. Furthermore, we will show combination studies with relevant standard of care therapies in models of lung and renal cancer.

Taken together, our preclinical data strongly supports the clinical evaluation of MM-161 in cancer patients.

Citation Format: Tamara Dake, Greg Finn, Melissa Geddie, Neeraj Kohli, Maja Razlog, Lihui Xu, Violette Paragas, Haluk Yuzugullu, Sara Ghassemifar, Yasmin Hashambhoy-Ramsay, Charlotte McDonagh, Marco Muda, Birgit Schoeberl. MM-161, a first-in-class pan-FGFR antibody [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 22. doi:10.1158/1538-7445.AM2017-22

Abstract 3842: Design and engineering of TRAIL fusion proteins for cancer therapy

Protein-based agonists of apoptotic death receptors have shown remarkable preclinical efficacy but limited clinical response. The short circulating half-life of recombinant human TRAIL and the necessity of Fc-mediated clustering for potentiating agonistic antibodies against DR4 and DR5 have been proposed to be major impediments to the clinical success of this class. To address these limitations we have created Fc-scTRAIL, a single fusion polypeptide consisting of an IgG1 Fc region followed by three successive TRAIL monomers connected by two fifteen-amino acid linkers. While Fc-scTRAIL showed potent activity in vitro, we observed a low TM (48 °C) and rapid inactivation in serum indicating protein instability. Subsequently, we applied a directed evolution approach using yeast surface display to identify mutations that would stabilize the TRAIL trimer. When individual mutations were transferred to the Fc-scTRAIL format, we observed a dramatic increase in the TM (66-70 °C) while the combination of three mutations improved serum stability by ten-fold. Stabilized Fc-scTRAIL shows greater pro-apoptotic activity across a panel of cancer cell lines when compared to mapatumumab (anti-DR4) and drozitumab (anti-DR5), or the combination of antibodies even in the presence of anti-Fc cross-linking. Moreover, anti-Fc did not improve Fc-scTRAIL activity suggesting that the hexavalent design of the molecule maximizes death receptor activation. Currently, in vivo evaluation of Fc-scTRAIL for pharmacokinetic properties and activity is underway. We believe this format, when combined with an appropriate patient selection strategy, will result in improved clinical outcomes.

Citation Format: Eric M. Tam, Hannah Hudson, Tamara Dake, Sara Ghassemifar, Andreas Raue, Yasmin Hashambhoy-Ramsay, Stephen L. Sazinsky, Anahita Daruwalla, Neeraj Kohli, Lihui Xu, Charlotte F. Mc Donagh, Birgit Schoeberl, Diana H. Chai. Design and engineering of TRAIL fusion proteins for cancer therapy. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3842.

Abstract LB-C25: Inhibition of ERBB3 with MM-121, IGF1-R with MM-141 or Met with MM-131 increases the activity of EGFR inhibitor MM-151 in colorectal cancer models expressing multiple resistance ligands

Introduction: The Epidermal Growth Factor Receptor (EGFR) pathway is a key driver of late-stage colorectal cancer (CRC) and EGFR inhibitors, such as cetuximab and panitumumab, prolong survival in a large subset of patients. Not all patients respond to EGFR inhibitor therapy, however, and resistance develops in those who respond. Accumulating evidence suggests that alternative signaling pathways circumvent EGFR blockade. Several studies have shown that tumors with high heregulin, IGF-1 or HGF respond poorly to EGFR-targeted therapies. Further, Phase 2 studies suggest that combined inhibition of EGFR and HGF with panitumumab and rilotumumab significantly improves response rates compared to panitumumab alone. These data support the notion that more than one pathway may be simultaneously active in late-stage CRC and that EGFR-directed therapy may be improved through combination strategies.

Merrimack has built a portfolio of biologic agents targeting key oncogenic receptors that block ligand binding and pathway activation, providing a unique opportunity to develop combination therapies in a biomarker-driven fashion. MM-151 targets EGFR; MM-121 (seribantumab) targets ERBB3; MM-141 (istiratumab) targets both IGF-1R and ERBB3; and MM-131 targets Met and EpCAM. Here we investigate responsiveness to different resistance ligands and the ability of drug combinations to block ligand-mediated cell growth more effectively than monotherapy.

Experimental procedures: We evaluated the prevalence of resistance ligands in colorectal adenocarcinoma patient samples by RNA in situ hybridization. To assess the effect of ligands and drugs on cell growth we assembled a panel of 29 genetically diverse CRC cell lines. Using a carefully optimized in vitro 3D culture system, we measured cell viability in response to MM-151, MM-121, MM-141, MM-131 or a combination of the drugs using MM-151 as the backbone. The screen was performed in the presence or absence of exogenously added ligands: EGF, heregulin, IGF-1 or HGF. Using these data, we selected representative xenograft models for in vivo analysis of drug combination efficacy.

Results: We show that colorectal cancer tumors co-express resistance ligands and that ligand prevalence appears to increase following treatment. Results from our in vitro screen show that CRC cell lines fall into two groups: those that are unresponsive to ligand stimulation and those that are responsive. Interestingly, cell lines that are responsive to one ligand tend to respond to other ligands as well, suggesting that blocking more than one pathway may prove more effective than blocking only a single pathway. In pre-clinical models of cell lines and xenografts, where ligands are co-expressed, combinations of targeted antibodies, using MM-151 as the backbone, have greater activity than monotherapy.

Conclusions: These data suggest that subsets of patients with high expression of individual or multiple ligands could benefit from different combinations of targeted therapies. A Phase 1 study evaluating the safety, pharmacology and preliminary activity of the co-administration of MM-151 and MM-121 (seribantumab) in heregulin positive cancer patients is currently enrolling patients with advanced colorectal cancer, non-small cell lung cancer, and head and neck cancer.

Citation Format: Marisa J. Wainszelbaum, Jessica Fessler, Johanna Lahdenranta, Olga Burenkova, Nat Gerami-Moayed, Yasmin Hashambhoy-Ramsay, Victoria Rimkunas, Gavin MacBeath. Inhibition of ERBB3 with MM-121, IGF1-R with MM-141 or Met with MM-131 increases the activity of EGFR inhibitor MM-151 in colorectal cancer models expressing multiple resistance ligands. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr LB-C25.