Abstract 353: A novel molecule with profound tumor killing activity

LY3343544: A novel MET antibody drug conjugate that shows profound pre-clinical in vivo anti-tumor activities, irrespective of MET pathway dependence MET is over-expressed in many types of human tumors. Due to the heterogeneity of human tumors, MET antibodies or small molecule inhibitors have benefited only small subsets of patients with tumors driven by signaling through the c-Met pathway. The patient selection strategies to identify those tumors with MET activation dependence are helpful in predicting sensitivity to many of these inhibitors. It was reported previously that Lilly’s MET antibody, emibetuzumab, showed clinical activity in selective NSCLC patients with high MET IHC staining (90% to 100% 3+ positive) when it was combined with erlotinib in Phase II clinical Trials. In searching for a better treatment for patients carrying the MET overexpression tumors regardless other co-existing mutations, we developed LY3343544, a novel antibody drug conjugate (ADC) molecule that consists of emibetuzumab conjugated with the potent microtubule inhibitor MMAE using a unique lysine conjugation approach. Upon binding to MET, LY3343544 is internalized via receptor-mediated endocytosis. LY3343544 maintains the similar binding and internalization activities to the cell surface MET as compared to emibetuzumab in the competitive cell binding assay and the internalization assay. We reported here that LY3343544 showed profound anti-tumor activity in a preclinical mouse models, and overcome intrinsic resistance mechanisms including KRAS, BRAF, PI3K and TP53 mutations. LY3343544 kills tumor cells expressing a wide range of MET levels on the cell surface and is capable of killing a variety of MET-overexpressing tumor cells including pancreatic, cholanglocarcinoma, colorectal, NSCLC, gastric, head and neck tumor cells in vitro. In contrast, LY3343544 does not kill human normal endothelial cells and normal epithelial cells, no activity on human peripheral blood mononuclear cells with or without activation as well as in cell-based assays. Moreover, LY3343544 is more stable in rodent PK studies than typical inter chain Cys VC-MMAE conjugates and showed tumor regressions in colorectal, NSCLC, gastric and pancreatic mouse xenograft models. Furthermore, LY3343544 shows profound tumor regression in >50% of PDAC PDX models (n=40): 20% complete response (CR); 22.5% partial response (PR); and 17.5% stable disease (SD); overall disease control rate (DCR) is 60%. In addition, LY3343544 shows tumor growth inhibition in cholangiocarcinoma PDX model that is resistant to emibetuzumab. In summary, LY3343544 is highly potent in killing a variety of tumor cells in cell-based killing assays. It demonstrated good stability in vivo and profound anti-tumor efficacy in multiple mouse xenograft models and patient-derived xenograft models thus is a promising agent to treat many types of cancers. Citation Format: Ling Liu, Aaron D. Wrobleski, Yin Yin, Wei Zeng, Xianming Chen, David J. Stokell, Sheng-bin Peng, Amita Datta-Mannan, Gregory P. Donoho, Philip W. Iversen, Philip Hipskind, Yiqing Feng. A novel molecule with profound tumor killing activity [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 353.