The U.S. Food and Drug Administration has accepted and granted Priority Review for zanidatamab (Ziihera) combined with chemotherapy, with or without tislelizumab, as a first-line treatment for HER2-positive advanced gastroesophageal cancer. A final decision is expected by August 25, 2026.
The application is based on results from the HERIZON-GEA-01 trial, where the zanidatamab combination showed clear improvements over standard therapy. Patients lived longer without disease progression (12.4 vs. 8.1 months) and had better overall survival (26.4 vs. 19.2 months). This is the first study in this setting to surpass one year of progression-free survival and two years of overall survival. Benefits were seen regardless of PD-L1 status.
Zanidatamab works by targeting two parts of the HER2 protein, improving anti-tumor activity compared to older drugs. Side effects were manageable, with infusion reactions, diarrhea, and some heart-related risks requiring monitoring. The drug is also under the Real-Time Oncology Review program to speed up availability if approved.