Jazz Pharmaceuticals' Drug Extends Survival Past Two Years in Advanced Stomach Cancer Trial

Jazz Pharmaceuticals plc (NASDAQ:JAZZ) on Tuesday shared efficacy and safety results from the Phase 3 HERIZON-GEA-01 trial of Ziihera (zanidatamab-hrii) for HER2-positive (HER2+) locally advanced or metastatic gastroesophageal adenocarcinoma (GEA). GEA includes cancers of the stomach, gastroesophageal junction, and esophagus. In November 2025, Jazz Pharmaceuticals and its partners Zymeworks Inc. (NASDAQ:ZYME) and BeOne Medicines Inc. (NASDAQ:ONC) announced topline results from the Phase 3 HERIZON-GEA-01 trial. The trial evaluated Ziihera in combination with chemotherapy, with or without BeOne’s Tevimbra (tislelizumab), as first-line treatment. The data will be presented at the 2026 ASCO Gastrointestinal Cancers Symposium (ASCO-GI). The study found: Both investigational arms, Ziihera plus tislelizumab and chemotherapy, and Ziihera plus chemotherapy, led to a statistically significant and clinically meaningful prolongation of progression-free survival (PFS). The doublet therapy (Ziihera+chemo) showed a PFS improvement of 35% and the triplet therapy (Ziihera+tislelizumab+chemo) showed approximately a 37% reduction in the risk of disease progression or death. This resulted in a median PFS of more than one year, representing a greater than four-month improvement compared to the control arm. The triplet therapy demonstrated a meaningful overall survival (OS) benefit with a median OS of more than two years (26.4 months). The company on Tuesday added that it is the longest reported in a Phase 3 trial in GEA, representing a greater than seven-month improvement in median OS and a 28% reduction in the risk of death versus trastuzumab plus chemotherapy. At this first interim analysis, the doublet therapy showed a median OS of more than two years (24.4 months), with a strong trend toward statistical significance, favoring Ziihera plus chemotherapy versus trastuzumab plus chemotherapy. Though not statistically significant, the doublet therapy showed a preliminary 20% death risk reduction, with a p-value of 0.0564. An additional planned OS interim analysis for Ziihera plus chemotherapy is currently expected in mid-2026. “Reaching more than two years of median overall survival in a global Phase 3 trial for HER2+ metastatic GEA is truly unprecedented,” said Elena Elimova, Princess Margaret Cancer Centre. JAZZ Price Action: Jazz Pharmaceuticals shares were up 2.07% at $170.44 at the time of publication on Wednesday, according to Benzinga Pro data. Photo by Aunt Spray via Shutterstock