Jazz and Zymeworks’ Ziihera Achieves Practice-Changing Results in Phase 3 Trial for First-Line HER2-Positive Gastroesophageal Adenocarcinoma
Ziihera (zanidatamab-hrii) in combination with chemotherapy, with or without tislelizumab (Tevimbra), met dual primary endpoints of progression-free survival (PFS) and overall survival (OS) in the Phase 3 HERIZON-GEA-01 trial, showing highly statistically significant and clinically meaningful improvements over trastuzumab plus chemotherapy.
The trial enrolled 914 patients with unresectable locally advanced, recurrent, or metastatic HER2-positive gastroesophageal adenocarcinoma (GEA) across ~300 sites in over 30 countries.
Results announced January 6, 2026, with late-breaking presentation at 2026 ASCO GI Symposium on January 8, 2026.
Jazz Pharmaceuticals plans to file a supplemental biologics license application (sBLA) for Ziihera as first-line treatment in HER2+ GEA in the first half of 2026.
Analysts highlight Ziihera as potentially practice-changing, able to replace Herceptin across PD-L1 statuses, with peak GEA revenue forecasts up to $2.9 billion.
Ziihera is a HER2 x HER2 bispecific antibody that binds two sites on HER2, inducing receptor internalization, CDC, ADCC, and ADCP for tumor cell death.