Recently, a few new HER2-directed antibody conjugates (ADCs), namely trastuzumab deruxtecan (T-DXd), trastuzumab duocarmazine (SYD985), disitamab vedotin (RC48-ADC), and MRG002 have promising activity in breast cancer with low HER2 expression in early phase clinical trials6–11. The gene discussed is ERBB2; the disease is breast cancer.