Zymeworks and Jazz Pharmaceuticals announced positive topline results from the Phase 3 HERIZON-GEA-01 trial evaluating zanidatamab (Ziihera) in first-line HER2-positive gastroesophageal adenocarcinoma. The trial met its primary endpoint with statistically significant and clinically meaningful improvements in progression-free survival versus trastuzumab plus chemotherapy; a regimen that added Jazz’s PD-1 inhibitor also showed OS and PFS gains, the companies said in a joint release. Jazz intends to file a supplemental Biologics License Application in the first half of 2026 based on the data, which were disclosed by Zymeworks and its development partners. The companies highlighted zanidatamab’s potential to become a new HER2-targeted standard of care in this indication and noted ongoing survival analyses and regulatory planning.