Presented at ACoP14. Patritumab deruxtecan (HER3-DXd) is a human epidermal growth factor receptor (HER3)-targeting antibody-drug conjugate with a topoisomerase I inhibitor payload (DXd). The drug-to-antibody ratio is approximately 8. HER3-DXd is currently being investigated as an anticancer agent in several phase 1-3 clinical studies in breast cancer (BC) and nonsmall cell lung cancer ( NSCLC) patients.