Shitara K, et al. - In all patients with HER2-positive gastric or gastro-esophageal junction cancer who were administered trastuzumab deruxtecan (DS-8201a) at the recommended doses for expansion, researchers reported the safety and initial activity results of their open-label, dose-escalation and dose-expansion phase 1 trial. Until withdrawal of consent, unacceptable toxicity, or progressive disease, patients received intravenously the recommended doses for expansion (5.4 mg/kg or 6.4 mg/kg trastuzumab deruxtecan) once every 3 weeks. A manageable safety profile was displayed by trastuzumab deruxtecan, which also demonstrated initial activity in heavily pretreated patients with HER2-positive gastric or gastro-esophageal junction cancer. Anemia and decreases in neutrophil, platelet, and white blood cell counts were the the most frequently seen grade 3 or worse treatment-related adverse effects.