ifinatamab deruxtecan + pembrolizumab + 5-fluorouracil + leucovorin

This is a **combination regimen** comprising four agents: ifinatamab deruxtecan, pembrolizumab, 5-fluorouracil, and leucovorin, under investigation for oncology indications, likely synergizing immune checkpoint inhibition, cytotoxic chemotherapy, and targeted antibody-drug conjugate (ADC) mechanisms. - **Ifinatamab deruxtecan** is an investigational B7-H3–directed antibody–drug conjugate (ADC) utilizing a humanized anti–B7-H3 IgG1 monoclonal antibody conjugated to a topoisomerase I inhibitor payload (DXd) via cleavable linkers. It induces selective tumor cell cytotoxicity by targeting tumors overexpressing B7-H3[1][4][7]. - **Pembrolizumab** is a fully human monoclonal antibody targeting PD-1 (programmed death receptor-1), blocking its interaction with PD-L1 and PD-L2, and thereby enhancing anti-tumor immune response. It is FDA approved for numerous malignancies[2][3][8]. - **5-fluorouracil** (5-FU) is a classic small molecule chemotherapeutic, an antimetabolite that inhibits thymidylate synthase, impeding DNA synthesis and inducing apoptosis in rapidly proliferating cancer cells. - **Leucovorin** (folinic acid) is a reduced folate that potentiates 5-FU activity by stabilizing the 5-FU–thymidylate synthase complex and mitigating certain toxicities. This regimen likely seeks to exploit the additive or synergistic anti-cancer activity of checkpoint inhibition, targeted ADC cytotoxicity, and enhanced chemotherapy efficacy, especially in solid tumors such as small cell lung cancer, where ifinatamab deruxtecan is in advanced-stage investigation.