One-armed 5D5 (OA5D5) is a potent humanized HGF-blocking anti-c-Met monovalent antibody that inhibits HGF-dependent activity in vitro and demonstrates anti-tumor efficacy in vivo

LB-372 The receptor tyrosine kinase c-Met and its ligand, hepatocyte growth factor/scatter factor (HGF/SF) are correlated with poor prognosis in numerous human cancers. We demonstrate here a novel monovalent antibody-based approach to block HGF/c-Met signaling. One-armed 5D5 (OA5D5) is an E. coli produced, humanized, monovalent, antagonistic anti-c-Met antibody, derived from the agonistic monoclonal antibody (mAb) 5D5. While the 5D5 mAb blocks HGF from binding to c-Met, it dimerizes and activates c-Met, stimulating receptor phosphorylation, downstream pathway activity and cellular responses, such as migration, morphogenesis and mitogenesis. 5D5 Fab fragments also block HGF from binding to c-Met, however do so without agonizing c-Met and instead act as antagonists. As it is difficult to achieve and maintain therapeutic levels of Fab fragments in vivo, a monovalent Fab/Fc form of 5D5 (OA5D5) was engineered. The novel design of OA5D5 utilizes knobs-into-holes mutations in the buried CH3-CH3 interface that enable proper assembly into a functional monovalent antibody when expressed in E. coli. OA5D5 binds to c-Met with high affinity and remains on the cell surface with c-Met, preventing HGF binding and subsequent c-Met phosphorylation as well as downstream signaling activity and cellular responses. In mice, OA5D5 is stable much longer than the 5D5 Fab, with a half-life of approximately 3-6 days. OA5D5 has significant anti-tumor efficacy in human glioblastoma (U87 MG) and pancreatic ductal carcinoma (KP4) subcutaneous and orthotopic xenograft models where HGF is produced as an autocrine growth factor. Anti-tumor efficacy is observed with single OA5D5 doses of 7.5 mg/kg and above. Together, these results show that OA5D5 is a potent, anti-c-Met monovalent antibody with promise as a therapeutic antibody in human cancer.