DS-3939a + DS-1103a

DS-3939a + DS-1103a is an investigational combination of two oncology agents developed by Daiichi Sankyo. DS-3939a is a tumor-associated mucin-1 (TA-MUC1)-directed antibody-drug conjugate (ADC) consisting of a humanized anti-TA-MUC1 IgG1 monoclonal antibody conjugated to the DNA topoisomerase I inhibitor payload DXd via a cleavable tetrapeptide-based linker. DS-1103a is a recombinant humanized IgG4 monoclonal antibody targeting signal regulatory protein alpha (SIRPα), designed to block the SIRPα-CD47 'don't eat me' signaling axis and promote macrophage-mediated phagocytosis of cancer cells. This combination is being evaluated in a Phase 1b/2 clinical trial (NCT07739966) for patients with advanced solid tumors, including pretreated non-small cell lung cancer (NSCLC), to leverage the synergistic effects of targeted cytotoxicity and immune checkpoint blockade.