TLDR
- Zymeworks stock climbed 57% following positive Phase 3 trial results for Ziihera in HER2-positive gastroesophageal adenocarcinoma treatment
- Ziihera combined with chemotherapy demonstrated statistically improved progression-free survival versus standard trastuzumab and chemotherapy regimen
- Triple combination of Ziihera, Tevimbra, and chemotherapy showed improved overall survival and progression-free survival in trial
- Jazz Pharmaceuticals will submit for regulatory approval in first half of 2026 seeking first-line treatment designation
- Jazz stock rose 21% in premarket trading while Asia-Pacific partner BeOne Medicines gained 3.9%
Zymeworks posted a 57% gain Monday after releasing Phase 3 trial data for Ziihera. The HERIZON-GEA-01 study evaluated the drug in HER2-positive gastroesophageal adenocarcinoma patients.
The trial assessed Ziihera plus chemotherapy as a first-line treatment. Data showed clinically meaningful and statistically improved progression-free survival compared to the standard trastuzumab plus chemotherapy combination.
Results also indicated a clinically meaningful effect on overall survival at the first interim analysis. The data showed a strong trend toward statistical significance for this measure.
A second treatment arm combined Ziihera with Tevimbra and chemotherapy. This triple combination produced clinically meaningful and statistically improved results for both overall survival and progression-free survival compared to the control arm.
Safety data remained consistent with the known profile of each individual agent. No new safety concerns emerged during the trial.
Partnership Details
Jazz Pharmaceuticals acquired development and commercialization rights to Ziihera from Zymeworks in 2022. Jazz stock jumped 21% in premarket trading following the data release.
BeOne Medicines holds rights to commercialize Ziihera across the Asia-Pacific region. BeOne shares gained 3.9% on the announcement.
Zymeworks maintains eligibility for additional regulatory and commercial milestone payments. The company will also collect tiered royalties on Ziihera net sales from its partners.
Regulatory Strategy
Jazz Pharmaceuticals intends to file a supplemental Biologics License Application in the first half of 2026. The filing will seek approval for Ziihera as a first-line treatment in HER2-positive locally advanced or metastatic gastroesophageal adenocarcinoma.
Ziihera already has approval in the United States, Europe, and China for second-line biliary tract cancer. Jazz and BeOne Medicines currently market the drug in their respective territories.
Jazz will present the full trial dataset at a major medical meeting in the first quarter of 2026. The company also plans to pursue publication in a peer-reviewed medical journal.
Rob Iannone, Jazz’s chief medical officer, described the results as potentially practice changing. He emphasized the limited treatment options currently available for patients with locally advanced or metastatic gastroesophageal adenocarcinoma.
Next Steps
Jazz will seek inclusion of the trial results in the National Comprehensive Cancer Network Guidelines for oncology treatment. This would establish Ziihera as a recommended option in treatment protocols.
The Phase 3 study represents a key milestone for Ziihera’s development in gastroesophageal adenocarcinoma. The drug targets HER2-positive tumors through a specific mechanism of action.
First-line treatments represent the initial therapy options offered to patients upon diagnosis. These treatments typically form the foundation of care protocols.
Jazz plans to share comprehensive trial data at the scheduled first quarter 2026 medical meeting.
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