Trastuzumab deruxtecan (T-DXd) showed significantly improved efficacy over trastuzumab emtansine (T-DM1) in the DESTINY-Breast03 trial (median follow-up, 28 months). Updated efficacy and safety analyses (median follow-up, 41 months) are presented. Patients with HER2-positive metastatic breast cancer previously treated with taxane and trastuzumab were randomized to T-DXd (5.4 mg/kg) or T-DM1 (3.6 mg/kg). The primary endpoint (PFS by BICR) was previously reported. Key secondary endpoint was overall survival (OS). With longer follow-up, T-DXd showed superior efficacy (median PFS: 29.0 vs 7.2 months; median OS: 52.6 vs 42.7 months) with a manageable safety profile. Treatment-emergent adverse events were consistent with previous analyses.

Javier Cortés, Sara A. Hurvitz, Seock-Ah Im, Hiroji Iwata, Giuseppe Curigliano, Sung-Bae Kim, Joanne W. Y. Chiu, Jose L. Pedrini, Wei Li, Kan Yonemori, Giampaolo Bianchini, Sherene Loi, Giuliano S. Borges, Xian Wang, Thomas Bachelot, Shunsuke Nakatani, Shahid Ashfaque, Zhengkang Liang, Anton Egorov, Erika Hamilton