Trastuzumab deruxtecan (DS-8201a), a HER2-targeting antibody–drug conjugate with topoisomerase I inhibitor payload, shows antitumor activity in uterine and ovarian carcinosarcoma with HER2/neu expression

•DS-8201a exhibited marked cytotoxicity in vitro among HER2/neu expressing cell lines.•0 HER2/neu cells are receptive to bystander killing effect from DS-8201a when mixed with 3+ HER2/neu-expressing cells.•DS-8201a inhibits HER2/neu expressing carcinosarcoma tumor growth in patient-derived xenografts.•DS-8201a is an effective antibody drug conjugate against HER2/neu-expressing uterine and ovarian carcinosarcomas.