Jazz Pharmaceuticals has released Phase III trial data for its drug Ziihera in combination with chemotherapy, showing a statistically significant improvement in overall survival for patients with HER2-positive gastroesophageal adenocarcinoma. The company announced the results from the second interim analysis of the HERIZON-GEA-01 trial, which involved nearly 225 sites across more than 30 countries. This global study randomised 914 adults receiving first-line treatment for the specific type of cancer.
Ziihera showed survival benefits in the key trial.
The combination of Ziihera with chemotherapy demonstrated a hazard ratio for overall survival that improved compared to the first interim analysis. This improvement was observed when the treatment was compared against trastuzumab plus chemotherapy, which is currently the standard of care. The safety profile of Ziihera administered with chemotherapy appeared consistent with previously reported data for each agent and the outcomes seen in the earlier stages of the HERIZON-GEA-01 study. No new safety concerns were identified as follow-up continued.
Patients with unresectable locally advanced, recurrent or metastatic HER2-positive gastroesophageal adenocarcinoma were assigned to receive zanidatamab with chemotherapy and tislelizumab, zanidatamab with chemotherapy, or trastuzumab plus chemotherapy. The trial’s main endpoints were progression-free survival assessed by blinded independent central review and overall survival.
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The United States Food and Drug Administration approved Ziihera along with tislelizumab and chemotherapy for first-line treatment in adults with HER2-positive unresectable locally advanced or metastatic gastroesophageal adenocarcinoma on 25 August 2026. The agency also approved Ziihera in combination with chemotherapy for HER2-positive disease in the same setting.
Jazz Pharmaceuticals executive vice-president of research and development and chief medical officer Rob Iannone stated that these results reinforce the company’s confidence that Ziihera is the new HER2-targeted backbone therapy in first-line HER2+ advanced GEA. He noted that the treatment replaces trastuzumab and extends survival beyond the current standard of care.
The company has submitted data from the HERIZON-GEA-01 trial for presentation at a major medical meeting in the fourth quarter of 2026. Jazz plans to submit these results to health authorities worldwide to support the drug’s positioning in the market.