Jazz Pharmaceuticals presented top-line data from its global Phase III HERIZON-GEA-01 trial of zanidatamab in first-line HER2-positive gastroesophageal adenocarcinoma (GEA) at the American Society of Clinical Oncology Gastrointestinal Cancer Symposium. The randomized, open-label study enrolled 620 patients across 18 countries, comparing zanidatamab plus standard chemotherapy with or without the anti-PD-1 antibody tislelizumab. The primary endpoint of progression-free survival showed a 35% risk reduction (HR 0.65; p<0.001), with median PFS of 12.4 months versus 8.3 months for chemotherapy alone. Key secondary endpoints included overall survival, which demonstrated a statistically significant improvement (HR 0.72; p=0.004) and an estimated 18-month survival rate of 62% compared with 48% in the control arm. The objective response rate was 72% in the combination arm versus 48% with chemotherapy alone, and the safety profile was consistent with known toxicities of the components, with no new safety signals observed.