HERIZON-GEA-01: Zanidatamab ± Tislelizumab vs Trastuzumab + Chemotherapy in HER2+ Gastric/GEJ Cancer

This discussion reviews the ongoing HERIZON-GEA-01 trial, a global Phase 3 study evaluating zanidatamab as part of first-line therapy for HER2-positive gastric and gastroesophageal junction (GEJ) adenocarcinoma. The trial includes two investigational arms, zanidatamab plus chemotherapy, and zanidatamab combined with tislelizumab and chemotherapy, compared with a control regimen of trastuzumab plus chemotherapy. Primary endpoints include overall survival and progression-free survival, allowing the study to assess both efficacy and durability. The discussion outlines the scientific rationale for zanidatamab’s bispecific HER2 targeting and references early clinical data showing antitumor activity and a manageable safety profile, with diarrhea reported among observed adverse events. As results remain pending, the panel emphasizes that HERIZON-GEA-01 is a key study that may help clarify how HER2-targeted therapy and immunotherapy could be integrated in future first-line treatment strategies for HER2-positive advanced gastric and GEJ cancers.