Jazz Pharmaceuticals (NASDAQ: JAZZ) announced on September 1, 2026, updated overall survival (OS) results from the phase III HERIZON-GEA-01 study, showing that its HER2-targeted bispecific antibody Ziihera (zanidatamab), combined with chemotherapy, significantly improved OS compared to the current standard of care in first-line HER2-positive gastroesophageal adenocarcinoma (GEA). The company’s stock rose 2.5% in response.
The updated second interim analysis demonstrated a statistically significant and clinically meaningful improvement in OS for the two-drug regimen of Ziihera plus chemotherapy versus trastuzumab plus chemotherapy, the current standard of care. Importantly, the OS hazard ratio improved from the first interim analysis reported in November 2025, indicating a stronger survival benefit with longer follow-up. The three-drug regimen of Ziihera plus Tevimbra (tislelizumab) and chemotherapy also showed an improved hazard ratio, further supporting a durable OS benefit.
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Expanding Ziihera’s Role in Gastric Cancer
These results follow the FDA’s recent label expansion of Ziihera as a first-line treatment for adults with HER2-positive unresectable locally advanced or metastatic GEA, in combination with chemotherapy, with or without Tevimbra. This approval significantly broadens Ziihera’s addressable market beyond its initial indication in previously treated HER2-positive biliary tract cancer (BTC).
GEA, which includes stomach, gastroesophageal junction, and esophageal cancers, is the fifth most common cancer globally. Approximately 20% of GEA patients have HER2-positive disease, a subgroup with particularly poor outcomes in advanced stages, where the five-year survival rate remains below 10%. The latest findings could help establish Ziihera-based regimens as a new standard of care, positioning the drug as a preferred HER2-targeted backbone therapy.
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Strategic Implications and Next Steps
Jazz plans to present the updated results at a medical meeting in the fourth quarter of 2026 and will submit the data to regulatory authorities worldwide. With approval across HER2-positive disease regardless of PD-L1 status, Ziihera could address a broader patient population than regimens requiring PD-L1 expression, a potential competitive advantage.
Ziihera was added to Jazz’s portfolio through a 2022 licensing agreement with Zymeworks (NYSE: ZYME), which grants Jazz exclusive rights in all territories except Asia-Pacific, where BeOne Medicines (formerly BeiGene) holds rights. Zymeworks is eligible for tiered royalties on sales. Jazz is also evaluating Ziihera in late-stage studies for first-line BTC and metastatic breast cancer.
Jazz’s stock has rallied 47.5% year-to-date, compared to the industry’s 9.7% increase. The company currently holds a Zacks Rank #3 (Hold). For investors, the sustained survival benefit and expanded label make Ziihera a key growth driver, though competition in the HER2-positive GEA space remains intense. The full data presentation in Q4 will be critical to confirm the durability of these results and their potential to reshape treatment paradigms.
This article is for informational purposes only and does not constitute financial advice. The biotech sector is volatile, and clinical trial outcomes can be uncertain. Investors should conduct their own research before making investment decisions.
