XB773

XB773 is a preclinical-stage antibody-drug conjugate (ADC) being developed by Exelixis, Inc. for the treatment of neuroendocrine carcinomas, including small cell lung cancer (SCLC) and neuroendocrine prostate cancer (NEPC). The drug comprises a monoclonal antibody targeting delta-like ligand 3 (DLL3), a protein frequently overexpressed in neuroendocrine-derived tumors, conjugated to a topoisomerase inhibitor payload, specifically exatecan. The mechanism of action involves the selective binding of the ADC to DLL3-expressing tumor cells, followed by internalization and the subsequent release of the exatecan payload. Exatecan inhibits DNA topoisomerase I, inducing double-strand DNA breaks and cell death in the targeted cancer cells.