SCR-A002, a novel FGFR2b-targeting antibody-drug-conjugate for solid tumors.

e15019 Background: FGFR2b (fibroblast growth factor receptor 2 IIIb), a transmembrane tyrosine kinase, is overexpressed in various cancers, including gastric, esophageal, breast, hepatocellular, pancreatic, ovary, uterine, cervical, endometrial, lung, colorectal cancers. Bemarituzumab (FPA144), an afucosylated humanized IgG1 monoclonal antibody targeting FGFR2b with enhanced ADCC activity, showed promising clinical efficacy in phase 2 study of FGFR2b-selected gastric or gastroesophageal junction adenocarcinoma. We have developed a potential first-in-class FGFR2b-targeting ADC (SCR-A002) at IND-enabling status, displaying significantly superior anti-tumor potency compared to Bemarituzumab. Methods: SCR-A002 is comprised of a humanized anti-FGFR2b IgG1 monoclonal antibody conjugated with proprietary TOPO1 inhibitor payload (DAR 8) via a cleavable linker. Anti-FGFR2b antibody was generated by immunization of FGFR2b protein in mice followed by hybridoma technique. Binding activity and cytotoxicity were assessed in FGFR2b+ tumor cell line. And anti-tumor efficacy was evaluated in several CDX and PDX models. Results: SCR-A002 could specifically bind to FGFR2b on cancer cells and be internalized, and the TOPO1 inhibitor could be cleaved intracellularly to kill the cancer cells potently in vitro. After single-dose administration of SCR-A002, tumor regression was achieved in different FGFR2b expression level CDX and PDX models, even with big-size tumor or Bemarituzumab resistance. Conclusions: SCR-A002 showed potent anti-tumor efficacy in preclinical data, which suggest that SCR-A002 is expected to provide a new treatment option as single agent or combo with SoC for patients with FGFR2b-overexpressing solid tumor.