Zymeworks soars on positive Phase III results for Ziihera

17 November 2025

Canada-based clinical-stage biotech Zymeworks (Nasdaq: ZYME) today announced positive top-line results from the Phase III HERIZON-GEA-01 trial evaluating Ziihera (zanidatamab-hrii) in combination with chemotherapy, with or without the PD-1 inhibitor Tevimbra (tislelizumab) as a first-line treatment for HER2-positive (HER2+) locally advanced or metastatic gastroesophageal adenocarcinoma, including cancers of the stomach, gastroesophageal junction, and esophagus.

The results were announced today by Zymeworks’ development and commercialization partners, Jazz Pharmaceuticals (Nasdaq: JAZZ) and BeOne Medicines (Nasdaq: ONC). Zymework’s shares leapt 31.8% to $18.52 in pre-market activity

Key findings from HERIZON-GEA-01

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