A Highly Efficacious Antibody Mixture Against MET-Amplified Tumors
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Author Manuscript Published OnlineFirst on July 5, 2017; DOI: 10.1158/1078-0432.CCR-17-0782 Author manuscripts have been peer reviewed and accepted for publication but have not yet been edited. Sym015: A highly efficacious antibody mixture against MET-amplified tumors Thomas Tuxen Poulsen#, Michael Monrad Grandal, Niels Jørgen Østergaard Skartved, Rikke Hald, Lene Alifrangis, Klaus Koefoed, Trine Lindsted, Camilla Fröhlich, Sofie Ellebæk Pollmann, Karsten Wessel Eriksen, Anna Dahlman, Helle Jane Jacobsen, Thomas Bouquin, Mikkel Wandahl Pedersen, Ivan David Horak, Johan Lantto, and Michael Kragh Symphogen A/S, Pederstrupvej 93, DK-2750 Ballerup, Denmark #To whom correspondence should be addressed: Thomas Tuxen Poulsen Symphogen A/S Pederstrupvej 93 DK-2750 Ballerup Denmark E-mail: [email protected] Tel: +45 45265050 Fax: +45 45265060 Running Title Sym015 inhibits MET-amplified tumors Keywords MET, EGFR resistance, antibodies, mixture, emibetuzumab, LY2875358 Notes All listed authors are current or former employees of Symphogen A/S. Abstract Length: 250 words Manuscript Length: 4987 words No. of Tables: 0 No. of Figures: 5 1 Downloaded from clincancerres.aacrjournals.org on October 1, 2021. © 2017 American Association for Cancer Research. Author Manuscript Published OnlineFirst on July 5, 2017; DOI: 10.1158/1078-0432.CCR-17-0782 Author manuscripts have been peer reviewed and accepted for publication but have not yet been edited. Translational Relevance In certain malignancies, such as gastric cancer and lung cancer, increased activation of the receptor tyrosine kinase (RTK) MET is associated with poor clinical outcome and resistance to targeted therapies. A number of MET-targeting monoclonal antibodies are in clinical development, but so far none have been approved. In recent years, preclinical and early clinical studies have demonstrated enhanced efficacy and anti-tumor activity of antibody mixtures directed against different RTK targets, leading to development of Sym015, a MET-targeting antibody mixture comprising two antibodies directed against non-overlapping epitopes. In the present study, we demonstrate that Sym015 inhibits MET-dependent cancer cell and tumor growth in multiple MET- dependent in vitro and in vivo models, including models exhibiting resistance to EGFR-targeting agents. The promising preclinical efficacy and safety data justify the ongoing clinical studies of Sym015 in patients with MET-amplified tumors. 2 Downloaded from clincancerres.aacrjournals.org on October 1, 2021. © 2017 American Association for Cancer Research. Author Manuscript Published OnlineFirst on July 5, 2017; DOI: 10.1158/1078-0432.CCR-17-0782 Author manuscripts have been peer reviewed and accepted for publication but have not yet been edited. Abstract Purpose: Activation of the receptor tyrosine kinase MET is associated with poor clinical outcome in certain cancers. To target MET more effectively, we developed an antagonistic antibody mixture, Sym015, consisting of two humanized monoclonal antibodies directed against non-overlapping epitopes of MET. Experimental Design/Results: We screened a large panel of well-annotated human cancer cell lines and identified a subset with highly elevated MET expression. In particular, cell lines of lung cancer and gastric cancer origin demonstrated high MET expression and activation, and Sym015 triggered degradation of MET and significantly inhibited growth of these cell lines. Next, we tested Sym015 in patient- and cell line-derived xenograft models with high MET expression and/or MET exon 14 skipping alterations, and in models harboring MET amplification as a mechanism of resistance to EGFR-targeting agents. Sym015 effectively inhibited tumor growth in all these models and was superior to an analogue of emibetuzumab, a monoclonal IgG4 antibody against MET currently in clinical development. Sym015 also induced antibody-dependent cellular cytotoxicity (ADCC) in vitro, suggesting that secondary effector functions contribute to the efficacy of Sym015. Retrospectively, all responsive, high MET-expressing models were scored as highly MET-amplified by in situ hybridization, pointing to MET amplification as a predictive biomarker for efficacy. Preclinical toxicology studies in monkeys showed that Sym015 was well tolerated, with a pharmacokinetic profile supporting administration of Sym015 every second or third week in humans. Conclusion: The preclinical efficacy and safety data provide a clear rationale for the ongoing clinical studies of Sym015 in patients with MET-amplified tumors. 3 Downloaded from clincancerres.aacrjournals.org on October 1, 2021. © 2017 American Association for Cancer Research. Author Manuscript Published OnlineFirst on July 5, 2017; DOI: 10.1158/1078-0432.CCR-17-0782 Author manuscripts have been peer reviewed and accepted for publication but have not yet been edited. Introduction The receptor tyrosine kinase (RTK) MET, also known as c-MET or hepatocyte growth factor (HGF) receptor (HGFR), is essential for embryonic and liver development, wound healing, and tissue regeneration. Lately, evidence has accumulated for the role of elevated MET activation as an oncogenic driver in a number of malignancies(1). In a context-dependent manner, high activation of MET induces increased cell proliferation, survival, motility, scattering, and angiogenesis, and drives epithelial-mesenchymal transition and cell invasion(2). There are multiple mechanisms for aberrant MET activation in tumorigenesis, including overexpression of its ligand HGF, as well as amplification, activating mutations, and other modifications of the MET gene. In particular, MET gene amplification is observed in a distinct subset of patients and is associated with poor prognosis in malignancies such as gastric and non- small cell lung cancer (NSCLC)(3,4). In addition, genetic alterations leading to MET exon 14 skipping have recently gained interest. MET exon 14 encodes the juxta-membrane receptor domain containing the binding site for the ubiquitin ligase CBL, responsible for triggering MET internalization and degradation. Exon 14 skipping thus induces stabilization of MET on the cell surface, leading to enhanced and constitutively active MET signaling(5,6). A shift to MET dependency as a mechanism of resistance to tyrosine kinase inhibitors (TKIs) targeting other RTKs is frequently observed, and up to 20% of epidermal growth factor receptor (EGFR) mutated NSCLCs develop resistance by MET gene amplification in response to treatment with EGFR- targeting TKIs(7,8). A number of MET-targeted TKIs and therapeutic antibodies have entered clinical development, but so far none have been approved as MET-targeting agents(9). TKIs generally have limited target specificity, which may lead to pleiotropic effects and unwanted toxicity. Furthermore, after long- term therapy with MET-targeting TKIs, subsets of quiescent tumor cells survive treatment, resulting in a rebound effect with aggressive tumor regrowth upon release of treatment pressure(10,11). MET-targeting antibodies in clinical development include the one-armed engineered antibody onartuzumab (MetMAb), which demonstrated activity in early-stage clinical trials(12–15), but failed to improve survival when used in combination with erlotinib to treat NSCLC in a phase 3 study(16). More recently, other antibodies targeting MET have entered the clinic. These include ABT-700, which has demonstrated activity in patients with MET-amplified tumors(17,18), and ARGX-111, which has been glyco-engineered to enhance secondary effector functions and which also demonstrated efficacy in a single patient with MET gene amplification(19,20). One of the most advanced MET-targeting antibody therapeutics in clinical development is emibetuzumab (LY2875358), a humanized IgG4 reported to block ligand binding and induce receptor internalization(21). Emibetuzumab has demonstrated preliminary evidence of antitumor activity in combination with erlotinib in patients with MET-positive tumors and is currently being evaluated in phase 2 studies(22). 4 Downloaded from clincancerres.aacrjournals.org on October 1, 2021. © 2017 American Association for Cancer Research. Author Manuscript Published OnlineFirst on July 5, 2017; DOI: 10.1158/1078-0432.CCR-17-0782 Author manuscripts have been peer reviewed and accepted for publication but have not yet been edited. As an alternative to monoclonal antibodies, mixtures comprising more than one antibody have demonstrated strong potential as RTK-targeting anti-cancer agents. A major therapeutic advantage of antibody mixtures is their ability to orchestrate receptor internalization and degradation in a manner superior to monoclonal antibodies, as previously demonstrated for different targets in the human epidermal growth factor receptor family(23,24). In light of the role of MET as a therapeutic target in cancer and the enhanced activity of antibody mixtures in targeting other RTKs, we developed the antibody mixture Sym015 comprising two antibodies directed against non-overlapping epitopes on the MET extracellular domain(25, Grandal et al., manuscript submitted). Here, we present data demonstrating efficacy of Sym015 in MET amplified cancer models. Sym015 demonstrated superior anti-proliferative and tumor growth-inhibitory effects in many cell lines and xenograft models, including models resistant to an analogue ofemibetuzumab. Furthermore, Sym015 was efficacious in models harboring MET exon 14 deletions and in models with acquired MET dependency in response to EGFR-targeting agents.