Dafna Kaufman

Monovalent antibody design and mechanism of action of onartuzumab, a MET antagonist with anti-tumor activity as a therapeutic agent

Significance Therapeutic antibodies have revolutionized the treatment of human disease. Despite these advances, antibody bivalency limits their utility against some targets. Here, we describe the development of a one-armed (monovalent) antibody, onartuzumab, targeting the receptor tyrosine kinase MET. While initial screening of bivalent antibodies produced agonists of MET, engineering them into monovalent antibodies produced antagonists instead. We explain the structural basis of the mechanism of action with the crystal structure of onartuzumab antigen-binding fragment in complex with MET and HGF-β. These discoveries have led to an additional antibody-based therapeutic option and shed light on the underpinnings of HGF/MET signaling. Binding of hepatocyte growth factor (HGF) to the receptor tyrosine kinase MET is implicated in the malignant process of multiple cancers, making disruption of this interaction a promising therapeutic strategy. However, targeting MET with bivalent antibodies can mimic HGF agonism via receptor dimerization. To address this limitation, we have developed onartuzumab, an Escherichia coli-derived, humanized, and affinity-matured monovalent monoclonal antibody against MET, generated using the knob-into-hole technology that enables the antibody to engage the receptor in a one-to-one fashion. Onartuzumab potently inhibits HGF binding and receptor phosphorylation and signaling and has antibody-like pharmacokinetics and antitumor activity. Biochemical data and a crystal structure of a ternary complex of onartuzumab antigen-binding fragment bound to a MET extracellular domain fragment, consisting of the MET Sema domain fused to the adjacent Plexins, Semaphorins, Integrins domain (MET Sema-PSI), and the HGF β-chain demonstrate that onartuzumab acts specifically by blocking HGF α-chain (but not β-chain) binding to MET. These data suggest a likely binding site of the HGF α-chain on MET, which when dimerized leads to MET signaling. Onartuzumab, therefore, represents the founding member of a class of therapeutic monovalent antibodies that overcomes limitations of antibody bivalency for targets impacted by antibody crosslinking.

Hepatocyte growth factor (HGF) autocrine activation predicts sensitivity to MET inhibition in glioblastoma

Because oncogene MET and EGF receptor (EGFR) inhibitors are in clinical development against several types of cancer, including glioblastoma, it is important to identify predictive markers that indicate patient subgroups suitable for such therapies. We investigated in vivo glioblastoma models characterized by hepatocyte growth factor (HGF) autocrine or paracrine activation, or by MET or EGFR amplification, for their susceptibility to MET inhibitors. HGF autocrine expression correlated with high phospho-MET levels in HGF autocrine cell lines, and these lines showed high sensitivity to MET inhibition in vivo. An HGF paracrine environment may enhance glioblastoma growth in vivo but did not indicate sensitivity to MET inhibition. EGFRvIII amplification predicted sensitivity to EGFR inhibition, but in the same tumor, increased copies of MET from gains of chromosome 7 did not result in increased MET activity and did not predict sensitivity to MET inhibitors. Thus, HGF autocrine glioblastoma bears an activated MET signaling pathway that may predict sensitivity to MET inhibitors. Moreover, serum HGF levels may serve as a biomarker for the presence of autocrine tumors and their responsiveness to MET therapeutics.

MET Kinase Inhibitor SGX523 Synergizes with Epidermal Growth Factor Receptor Inhibitor Erlotinib in a Hepatocyte Growth Factor–Dependent Fashion to Suppress Carcinoma Growth

The hepatocyte growth factor (HGF)-MET pathway supports several hallmark cancer traits, and it is frequently activated in a broad spectrum of human cancers (http://www.vai.org/met/). With the development of many cancer drugs targeting this pathway, there is a need for relevant in vivo model systems for preclinical evaluation of drug efficacy. Here, we show that production of the human HGF ligand in transgenic severe combined immunodeficient mice (hHGF(tg)-SCID mice) enhances the growth of many MET-expressing human carcinoma xenografts, including those derived from lung, breast, kidney, colon, stomach, and pancreas. In this model, the MET-specific small-molecule kinase inhibitor SGX523 partially inhibits the HGF-dependent growth of lung, breast, and pancreatic tumors. However, much greater growth suppression is achieved by combinatorial inhibition with the epidermal growth factor receptor (EGFR) kinase inhibitor erlotinib. Together, these results validate the hHGF(tg)-SCID mouse model for in vivo determination of MET sensitivity to drug inhibition. Our findings also indicate that simultaneously targeting the MET and EGFR pathways can provide synergistic inhibitory effects for the treatment of cancers in which both pathways are activated.

Strengthening Context-Dependent Anticancer Effects on Non–Small Cell Lung Carcinoma by Inhibition of Both MET and EGFR

The MET and EGFR receptor tyrosine kinases (RTK) are often coexpressed and may cross-talk in driving the development and progression of non–small cell lung carcinoma (NSCLC). In addition, MET amplification is an alternative resistance mechanism for escaping EGFR-targeted therapy. To assess the benefits of combined targeting of MET and EGFR for treating NSCLCs, we investigated the activities of these two RTK pathways in NSCLC cell lines and evaluated their responses to SGX523 and erlotinib, the small-molecule kinase inhibitors of MET and EGFR, respectively. We showed that MET interacts with and cross-activates EGFR in MET-amplified or -overexpressed cells. The inhibition of both MET and EGFR results in maximal suppression of downstream signaling and of cell proliferation when their ligands are present. Furthermore, we showed that SGX523 plus erlotinib strengthens anticancer activity in vivo in a cellular context–dependent manner. The combination led to the regression of H1993 tumors by enhancing the suppression of proliferation and inducing apoptosis, whereas H1373 tumor growth was significantly reduced by the combination via suppression of proliferation without inducing apoptosis. SGX523 alone was sufficient to achieve near-complete regression of EBC-1 tumors; its combination with erlotinib strongly inhibited the viability of a population of insensitive cells emerging from an SGX523-treated EBC-1 tumor recurrence. Our data suggest that inhibition of both MET and EGFR can enhance anticancer effects against NSCLCs in a context-dependent manner and thus provide a strong rationale for combining MET and EGFR inhibitors in treating NSCLCs. Mol Cancer Ther; 12(8); 1429–41. ©2013 AACR.

Mimp/Mtch2, an Obesity Susceptibility Gene, Induces Alteration of Fatty Acid Metabolism in Transgenic Mice.

Objective Metabolic dysfunctions, such as fatty liver, obesity and insulin resistance, are among the most common contemporary diseases worldwide, and their prevalence is continuously rising. Mimp/Mtch2 is a mitochondrial carrier protein homologue, which localizes to the mitochondria and induces mitochondrial depolarization. Mimp/Mtch2 single-nucleotide polymorphism is associated with obesity in humans and its loss in mice muscle protects from obesity. Our aim was to study the effects of Mimp/Mtch2 overexpression in vivo. Methods Transgenic mice overexpressing Mimp/Mtch2-GFP were characterized and monitored for lipid accumulation, weight and blood glucose levels. Transgenic mice liver and kidneys were used for gene expression analysis. Results Mimp/Mtch2-GFP transgenic mice express high levels of fatty acid synthase and of β-oxidation genes and develop fatty livers and kidneys. Moreover, high-fat diet–fed Mimp/Mtch2 mice exhibit high blood glucose levels. Our results also show that Mimp/Mtch2 is involved in lipid accumulation and uptake in cells and perhaps in human obesity. Conclusions Mimp/Mtch2 alters lipid metabolism and may play a role in the onset of obesity and development of insulin resistance.

Simultaneous Targeting of Two Distinct Epitopes on MET Effectively Inhibits MET- and HGF-Driven Tumor Growth by Multiple Mechanisms

Increased MET activity is linked with poor prognosis and outcome in several human cancers currently lacking targeted therapies. Here, we report on the characterization of Sym015, an antibody mixture composed of two humanized IgG1 antibodies against nonoverlapping epitopes of MET. Sym015 was selected by high-throughput screening searching for antibody mixtures with superior growth-inhibitory activity against MET-dependent cell lines. Synergistic inhibitory activity of the antibodies comprising Sym015 was observed in several cancer cell lines harboring amplified MET locus and was confirmed in vivo. Sym015 was found to exert its activity via multiple mechanisms. It disrupted interaction of MET with the HGF ligand and prompted activity-independent internalization and degradation of the receptor. In addition, Sym015 induced high levels of CDC and ADCC in vitro. The importance of these effector functions was confirmed in vivo using an Fc-effector function–attenuated version of Sym015. The enhanced effect of the two antibodies in Sym015 on both MET degradation and CDC and ADCC is predicted to render Sym015 superior to single antibodies targeting MET. Our results demonstrate strong potential for use of Sym015 as a therapeutic antibody mixture for treatment of MET-driven tumors. Sym015 is currently being tested in a phase I dose escalation clinical trial (NCT02648724). Mol Cancer Ther; 16(12); 2780–91. ©2017 AACR.

Abstract 2167: Strengthening anti-cancer effects on non-small cell lung carcinoma by dual blockage of MET and EGFR in a context-dependent manner.

Non-small cell lung carcinoma (NSCLC) accounts for more than 80% of lung cancer, the leading cause of death among all cancer casualties. The MET receptor tyrosine kinase (RTK) is often co-expressed with EGFR in the NSCLC cells, and is an important alternative resistant mechanism for escaping EGFR-targeted therapy. To assess the benefit of dual blockage of MET and EGFR for NSCLC therapy, we investigated the activities of these two RTK pathways in several NSCLC cell lines carrying distinct cellular contexts, and determined their responses to SGX523 and erlotinib, the small molecule kinase inhibitors of MET and EGFR, respectively. Here, we showed that MET can cross-activate EGFR in MET-amplified or overexpressing cells via hetero-receptor dimerization, and the MET-dependent phosphorylation of EGFR can be abolished by SGX523 but not by erlotinib. More importantly, combined inhibition of MET and EGFR in vitro results in a maximal suppression of downstream ERK and AKT activation and of cell proliferation when their ligands (HGF and EGF) are present. Furthermore, we demonstrated that SGX523 and erlotinib combination strengthens anti-cancer activity in vivo in a cellular context-dependent manner. The combination led to regression of MET-amplified H1993 tumors by enhancing suppression of proliferation and inducing apoptosis, whereas significantly reduced MET-non-amplified H1373 tumor growths by suppression of proliferation without inducing apoptosis. Although SGX523 alone was sufficient to achieve near complete regression of MET-addicted EBC-1 tumors, its combination with erlotinib strongly inhibited viability of a population of SGX523-insensitive cells emerging from SGX523-treated EBC-1 tumor relapse. Our data suggest that dual blockage of MET and EGFR can enhance anti-cancer effects on NSCLC in a context-dependent manner, and provide a strong rationale and mechanisms for combining MET and EGFR inhibitors for NSCLC therapy. Citation Format: Yu-Wen Zhang, Ben Staal, Curt Essenburg, Steven Lewis, Dafna Kaufman, George F. Vande Woude. Strengthening anti-cancer effects on non-small cell lung carcinoma by dual blockage of MET and EGFR in a context-dependent manner. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2167. doi:10.1158/1538-7445.AM2013-2167

Abstract LB-223: Dissecting the therapeutic determinants of MET inhibition in Glioblastoma: HGF-autocrine loop predicts sensitivity to MET inhibitor

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Due to its invasive nature, glioblastoma (GBM) is the most aggressive brain cancer. Hepatocyte growth factor (HGF) binds to MET tyrosine kinase receptor and induces invasive tumor growth. As MET inhibitors are entering clinical trials against several types of cancer including GBM, it is compelling to identify therapeutic determinants which could indicate which patient subsets are suitable for this therapy. We investigated in vivo four types of GBM models for their sensitivity to MET (SGX523*) or EGFR (erlotinib*) inhibitors: 1) Tumors sustained by an HGF-autocrine loop; 2) tumors displaying paracrine HGF tumor growth; and 3) tumors with polysomy MET amplification. 4) In addition, GBM tumors with epidermal growth factor receptor (EGFR) amplification were included, as this occurs frequently in GBM patients and often in association with MET aberrancy. Of the four tumor types, we observed that HGF-autocrine loop expression correlates with p-MET levels in the HGF autocrine cell lines, which in turn are extremely sensitive to MET inhibition in vivo. Moreover, serum HGF levels in HGF-autocrine loop GBM xenografts correlate with MET inhibition. Paracrine HGF can enhance GBM growth in vivo , but they were not significantly sensitive to MET inhibition. In type 4, EGFR VIII amplification predicted sensitivity to erlotinib, but MET polysomy in the same tumor did not display MET activity and the cells did not show sensitivity to MET inhibition. We conclude that HGF-autocrine loop GBM tumors bear an activated MET signaling pathway that may be used to predict sensitivity to MET inhibitors in GBM patients. However, targeting MET alone may not be sufficient for treating GBM and the combination of MET with other RTK inhibitors, especially EGFR inhibitors should be considered. *SGX523, a selective small molecule MET inhibitor, was obtained from Eli Lilly and Company, Indianapolis IN. *Erlotinib inhibits EGFR and was a generous gift from OSI Pharmaceuticals, Long Island N.Y. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-223. doi:10.1158/1538-7445.AM2011-LB-223

Abstract LB-305: Why two are better than one: Suppression of carcinoma cell growth in vitro and in human HGF/SF transgenic SCID by inhibitors of MET (SGX523) and EGFR (erlotinib)

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC The signaling cascade originating from hepatocyte growth factor/scatter factor (HGF/SF)-MET ligand-receptor pair is frequently observed in a broad spectrum of human cancers. Inappropriate activation of this pathway has been shown to occur via: paracrine/autocrine activation; by amplification or mutation in the MET gene; or through ligand independent mechanisms (www.vai.org/met). Various MET drugs targeting this pathway are under development and in need of relevant in vivo tumor models to allow assessment of drug efficacy alone or in combination against human MET expressing tumors. Conventional mouse models post a significant limitation on fulfilling such demand as mouse HGF/SF has low affinity/activity on the human MET. Such limitations are abrogated in human HGF/SF transgenic SCIDs (designated hHGFtg-SCID), which, unlike its non-transgenic littermates, produce human HGF/SF to allow human MET signaling on cells of human cancer xenografts. Here, we show that the hHGFtg-SCID mouse significantly enhances tumor xenograft growth of many MET-expressing human carcinoma cell lines including lung, breast, kidney, colon, gastric and pancreatic cancers. Using the hHGFtg-SCID mouse model systems, we demonstrated that SGX523, a MET small molecule kinase inhibitor which suppressed MET phosphorylation and downstream signaling activation in vitro, partially inhibits the growth of xenografts derived from NCI-H596 lung cancer cells, HCC1954 breast cancer cells and HPAF II pancreatic cancer cells. Furthermore, we found that the partial tumor growth inhibition by SGX523 was significantly enhanced by co-administration of erlotinib, the EGFR small molecule kinase inhibitor. In vitro, erlotinib also enhanced SGX523 inhibitory activity in cell proliferation and G1/S cell cycle progression assays. Our data suggest that the hHGFtg-SCID mouse is a valuable system for evaluating MET drugs, and simultaneously targeting MET and EGFR pathways may provide a better treatment for cancers harboring inappropriate activation of both pathways. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-305.