ERBB2 and adenocarcinoma: Trastuzumab deruxtecan (T-DXd; 6·4 mg/kg) is approved for metastatic human epidermal growth factor receptor 2 (HER2)–positive (HER2+) gastric or gastroesophageal junction (GEJ) adenocarcinoma after a trastuzumab-based regimen.