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# Promising Ziihera Data in Gastric Cancer Trial
- URL: https://www.fdaweb.com/promising-ziihera-data-in-gastric-cancer-trial/
- Published: 2025-11-17T12:00:00.000Z
- Updated: 2026-09-14T15:26:43.000Z
- Author: David McFarland
- Tags: Biologics, #legacy-id-D5160234

Zymeworks says its HER2-targeted bispecific antibody Ziihera (zanidatamab-hrii) significantly improved outcomes for patients with HER2-positive gastroesophageal adenocarcinoma (GEA) in a large Phase 3 study. Topline results from the HERIZON-GEA-01 trial showed that Ziihera combined with chemotherapy, with or without the PD-1 inhibitor Tevimbra (tislelizumab), delivered substantial improvements in both progression-free survival (PFS) and overall survival (OS) compared with the current standard regimen of trastuzumab plus chemotherapy, according to the company. The study was conducted by Zymeworks’ partners Jazz Pharmaceuticals and BeOne Medicines.

Zymeworks says that both Ziihera-based treatment arms met the trial’s primary endpoint, demonstrating statistically significant and clinically meaningful gains in PFS over trastuzumab and chemotherapy. The combination of Ziihera, Tevimbra, and chemotherapy also improved overall survival, meeting statistical significance, it says, adding that the Ziihera-plus-chemotherapy arm showed a strong positive trend in OS that has not yet crossed the statistical boundary; another interim analysis is planned for mid-2026.

Importantly, the survival benefit for the Ziihera/Tevimbra regimen was observed across PD-L1 positive and PD-L1 negative subgroups, according to the company. The combinations also improved secondary endpoints, including objective response rate and duration of response. Safety findings were consistent with the known profiles of the drugs, with no new risks identified.

Calling the data “a true turning point,” Zymeworks CEO Kenneth Galbraith says the results support Ziihera’s potential to replace trastuzumab as the preferred HER2-targeted therapy in first-line GEA — a fast-moving and often fatal cancer affecting the stomach, gastroesophageal junction, and esophagus.

Jazz Pharmaceuticals intends to submit a supplemental BLA in the first half of 2026\. Ziihera is already approved for previously treated HER2-positive biliary tract cancer.