Zymeworks, in partnership with Jazz Pharmaceuticals and BeOne, reported positive topline results from the Phase 3 HERIZON‑GEA‑01 study: zanidatamab (Ziihera) plus chemotherapy improved progression‑free survival (PFS) versus trastuzumab plus chemotherapy, with the triplet that added tislelizumab also showing statistically significant overall survival (OS) gains. The sponsors plan regulatory filings and supplemental submissions based on the dataset. The trial included arms with zanidatamab alone and zanidatamab plus PD‑1 inhibition; both demonstrated clinically meaningful benefits. Jazz signaled it will press forward with regulatory discussions and commercialization planning. The results position a bispecific HER2 agent as a potential new first‑line standard in HER2‑positive gastroesophageal adenocarcinoma.