A novel bivalent anti-c-MET/PD-1 bispecific antibody exhibits potent cytotoxicity against c-MET/PD-L1-positive colorectal cancer

Abstract Previously, we generated a novel bispecific antibody (BsAb) targeting c-MET and PD-1 (PDCD1), which can bridge T cells and c-MET positive tumor cells. This study investigated functional mechanisms and antitumor activities of our BsAb against c-MET/PD-L1 (CD274) positive colorectal cancer (CRC). The Cancer Genome Atlas database was used to evaluate c-MET expression in tumor tissues. The expression of plasma exosomal c-MET/PD-L1 in CRC patients was measured by enzyme-linked immunosorbent assays. Western blotting assay was performed to determine expression levels of c-MET and molecular mechanism. The scratch wound healing migration assay and transwell chamber invasion assay were conducted to determine cell migratory and invasive abilities, respectively. A humanized mouse model was used to evaluate antitumor activity of the BsAb in vivo. The BsAb inhibited c-MET/PD-L1+ CRC cell migration and invasion and mediated strong antitumor activity against HCT116 tumors in mice. The BsAb induced the degradation of c-MET protein in a dose and time-dependent manner. The BsAb suppressed the phosphorylation of c-MET downstream proteins GRB2-associated-binding protein 1 (Gab1) and focal adhesion kinase (FAK). The BsAb promoted macrophage phagocytosis. Furthermore, the level of plasma exosomal-c-MET/PD-L1 distinguished CRC patients from healthy controls. The BsAb exhibited potent anti-tumor activities by two distinguished mechanisms: inhibition of c-MET signal transduction and promotion of macrophage-mediated phagocytosis. Our BsAb may provide a novel therapeutic tool for patients with c-MET/PD-L1+ CRC, and the status of exosomal-c-MET/PD-L1 may be predictive responsiveness to treatment with our BsAb.