Zymeworks (ZYME) Stock Soars as Cancer Drug Shows Promise in Phase 3 Trial

TLDR

• Zymeworks stock jumped 57% after positive Phase 3 trial results for cancer drug Ziihera in treating HER2-positive gastroesophageal adenocarcinoma
• Ziihera plus chemotherapy showed statistically improved progression-free survival compared to trastuzumab and chemotherapy in first-line treatment
• Combined with Tevimbra and chemotherapy, Ziihera demonstrated improved overall survival and progression-free survival versus control group
• Jazz Pharmaceuticals plans to submit supplemental Biologics License Application in first half of 2026 for first-line treatment approval
• Jazz stock rose 21% in premarket trading while partner BeOne Medicines gained 3.9%

Zymeworks stock surged 57% on Monday following the announcement of positive Phase 3 trial results. The company reported data from its HERIZON-GEA-01 trial evaluating Ziihera as a treatment for HER2-positive gastroesophageal adenocarcinoma.

Zymeworks Inc., ZYME

The trial tested Ziihera combined with chemotherapy as a first-line treatment. Results showed clinically meaningful and statistically improved progression-free survival compared to the standard trastuzumab and chemotherapy combination.

The drug also demonstrated a clinically meaningful effect on overall survival at the first interim analysis. This showed a strong trend toward statistical significance.

A second combination tested in the trial included Ziihera with Tevimbra and chemotherapy. This three-drug regimen showed clinically meaningful and statistically improved results for both overall survival and progression-free survival versus the control arm.

Jazz Pharmaceuticals acquired development and commercialization rights to Ziihera from Zymeworks in 2022. The company’s stock jumped 21% in premarket trading following the announcement.

Regulatory Timeline

Jazz Pharmaceuticals intends to submit a supplemental Biologics License Application in the first half of 2026. This submission would support Ziihera as a first-line treatment for patients with HER2-positive locally advanced or metastatic gastroesophageal adenocarcinoma.

The safety profile of Ziihera in the trial was generally consistent with known safety profiles of each agent. No new safety signals were observed during the study.

Ziihera currently has approval in the United States, Europe, and China. The drug is approved for use in second-line biliary tract cancer and is marketed by Jazz and BeOne Medicines.

BeOne Medicines holds commercialization rights for Ziihera in the Asia-Pacific region. Shares of BeOne Medicines rose 3.9% on the news.

Financial Arrangements

Zymeworks remains eligible for additional regulatory and commercial milestones from its partners. The company will also receive tiered royalties on net sales of Ziihera.

Jazz Pharmaceuticals plans to submit the trial data for presentation at a major medical meeting. This presentation is scheduled for the first quarter of 2026.

The company will also seek publication in a peer-reviewed journal. Jazz intends to submit the results for adoption in the National Comprehensive Cancer Network Guidelines for oncology treatment.

Rob Iannone, chief medical officer at Jazz, stated the results could be practice changing. He highlighted the potential impact for patients facing limited treatment options in locally advanced or metastatic gastroesophageal adenocarcinoma.

The Phase 3 trial evaluated Ziihera as a first-line treatment option. First-line treatments are the initial therapies given to patients when they are first diagnosed with a condition.

Jazz plans to present complete trial data at the first quarter 2026 medical meeting.

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