08:47 AM EST, 11/17/2025 (MT Newswires) -- Jazz Pharmaceuticals ( JAZZ ) said Monday that its late-stage trial evaluating Ziihera in combination with chemotherapy, with or without the PD-1 inhibitor tislelizumab, showed highly statistically significant and clinically meaningful improvements in progression-free survival in patients with HER2-positive locally advanced or metastatic gastroesophageal adenocarcinoma.

The company said Ziihera plus tislelizumab and chemotherapy also showed statistically significant and clinically meaningful improvements in overall survival.

Jazz said it plans to submit a supplemental Biologics License Application for this indication in the US in H1.

Jazz said Ziihera plus chemotherapy alone showed a clinically meaningful effect with a strong trend toward statistical significance for overall survival at the time of the first analysis.

Jazz said the trial is ongoing, with an additional interim analysis of overall survival for the Ziihera plus chemotherapy arm expected in mid-2026.

The safety profiles of Ziihera in combination with chemotherapy, with or without tislelizumab, was generally consistent with the known safety profiles, with no new safety signals observed, the company said.

Shares of Jazz were up 21% in recent Monday premarket activity.