HER2-targeted therapies such as treatments with trastuzumab, pertuzumab, lapatinib, and trastuzumab emtansine (T-DM1), neratinb, tucatinib, and trastuzumab–deruxtecan, have shown clinically significant efficacy against HER2-positive breast cancer. The gene discussed is ERBB2; the disease is breast carcinoma.