LBA1 Trastuzumab deruxtecan (T-DXd) vs trastuzumab emtansine (T-DM1) in patients (Pts) with HER2+ metastatic breast cancer (mBC): Results of the randomized phase III DESTINY-Breast03 study

T-DXd is a HER2-targeting antibody–drug conjugate approved for pts with advanced HER2+ mBC based on the results from DESTINY-Breast01 (NCT03248492). This is the first report of DESTINY-Breast03 (NCT03529110), a multicenter, open-label, randomized phase 3 study comparing the efficacy and safety of T-DXd vs T-DM1 in pts with HER2+ mBC previously treated with trastuzumab and taxane. This is the first reported randomized study of T-DXd in BC.