The randomized, open-label phase 3 trial DESTINY-Breast02 compares DS-8201a with physicians’ choice (trastuzumab plus capecitabine or lapatinib plus capecitabine) in patients with HER2-positive advanced breast cancer (ABC) pretreated with prior standard of care HER2 targeting therapies including T-DM1 (clinicaltrials.gov identifier: NCT03523585). The gene discussed is ERBB2; the disease is breast carcinoma.