The treatment arsenal for small cell lung cancer could soon include antibody-drug conjugates, with early data from three phase I studies indicating robust response rates to CD56-targeting DXC006, DLL-3-targeting BL-M14D1, and B7-H3-targeting SYS6043. The latter also appears active in other tumor types, including ovarian and breast cancers. As well, phase II findings on a fourth ADC candidate, HER2-targeting trastuzumab brengitecan, suggest its strong efficacy in platinum-resistant ovarian cancer.