Zymeworks’ Ziihera® Achieves Landmark Results in HER2+ Gastroesophageal Adenocarcinoma
VANCOUVER, British Columbia, Jan. 06, 2026 (GLOBE NEWSWIRE) - Zymeworks Inc. (NASDAQ: ZYME), a leading biotechnology company, has announced remarkable results from the Phase 3 HERIZON-GEA-01 trial. This study evaluated Ziihera® (zanidatamab-hrii) in combination with chemotherapy, marking a significant step forward in the treatment of HER2-positive (HER2+) locally advanced or metastatic gastroesophageal adenocarcinoma (GEA). The positive findings suggest that Ziihera may replace trastuzumab as the standard of care.
Key Findings from HERIZON-GEA-01 Trial
The data revealed both investigational arms—Ziihera plus tislelizumab (Tevimbra®) and chemotherapy, and Ziihera plus chemotherapy—exhibited substantial benefits:
- Median Overall Survival (OS): Ziihera plus tislelizumab showed a median OS of more than 26.4 months, achieving the longest reported OS in a Phase 3 GEA trial, which represents more than a seven-month improvement over trastuzumab.
- Median Progression-Free Survival (PFS): The trial demonstrated a median PFS of over 12.4 months, reflecting a 35% reduction in the risk of disease progression compared to the control arm.
- Safety Profile: The combined therapy’s safety profile was consistent with existing HER2-directed therapies, with manageable adverse events.
Upcoming Presentation at ASCO GI Symposium
The HERIZON-GEA-01 findings will be presented as a late-breaking oral presentation at the 2026 ASCO Gastrointestinal Cancers Symposium on January 8, 2026, from 8:57 to 9:07 AM PST (abstract number: LBA285). This event will further highlight the potential of Ziihera as a leading HER2-targeted therapy in the GEA landscape.
Strategic Partnerships and Financial Implications
Zymeworks is eligible for up to $440 million in milestone payments from partners Jazz Pharmaceuticals and BeOne Medicines, contingent on regulatory approvals in various markets, including the United States, Europe, Japan, and China. The expected breakdown includes:
- United States: $250 million
- Europe: $100 million
- Japan: $75 million
- China: $15 million
Additionally, Zymeworks anticipates increased royalty revenues from Ziihera sales as global market approvals continue.
Executive Insights
“These results underscore the promise of Ziihera to meaningfully advance care for patients with HER2-positive disease,” said Kenneth Galbraith, Chair and CEO of Zymeworks. “The HERIZON-GEA-01 data further establishes Ziihera as the new HER2-targeted agent-of-choice, with the potential to redefine first-line treatment.”
The HERIZON-GEA-01 Trial Overview
The HERIZON-GEA-01 trial is a global, randomized, open-label Phase 3 study that aims to assess the efficacy and safety of Ziihera combined with chemotherapy, with or without tislelizumab, against trastuzumab plus chemotherapy for adults with advanced HER2+ GEA. The trial included 914 patients from approximately 300 trial sites across more than 30 countries.
Conclusion
The advancements presented in the HERIZON-GEA-01 trial reinforce Zymeworks’ commitment to pioneering innovative therapies. With its promising results, Ziihera (NASDAQ: ZYME) stands positioned to significantly change the treatment landscape for HER2-positive GEA patients.