Jazz Pharmaceuticals plc (JAZZ) delivered some genuinely impressive news Tuesday about its cancer drug Ziihera, showing it can help patients with advanced stomach cancer live substantially longer than current standard treatments. And we're not talking about incremental improvements here—we're talking about pushing median survival past the two-year mark, which is actually a big deal in this type of cancer.
The results come from the Phase 3 HERIZON-GEA-01 trial, which tested Ziihera (zanidatamab-hrii) in patients with HER2-positive gastroesophageal adenocarcinoma, or GEA for short. That's the umbrella term for cancers affecting the stomach, gastroesophageal junction, and esophagus—cancers that have historically been tough to treat when they've spread.
Jazz developed Ziihera with partners Zymeworks Inc. (ZYME) and BeOne Medicines Inc. (ONC), who initially announced topline results back in November 2025. The detailed data was presented at the 2026 ASCO Gastrointestinal Cancers Symposium this week.
Two Combinations, Both Winners
The trial tested two different approaches as first-line treatment. One combined Ziihera with chemotherapy (the doublet), while the other added BeOne's Tevimbra (tislelizumab) to create a triplet therapy. Both performed remarkably well.
On progression-free survival—meaning how long patients lived without their cancer getting worse—both combinations delivered statistically significant improvements. The doublet reduced the risk of disease progression or death by 35%, while the triplet hit 37%. That translated to median PFS of more than one year, which was over four months better than the control arm using standard trastuzumab plus chemotherapy.
But the overall survival numbers are where things get really interesting. The triplet therapy achieved a median overall survival of 26.4 months—that's more than two years. Jazz emphasized that this represents the longest median OS ever reported in a Phase 3 trial for GEA. Compared to the control arm, that's a seven-month improvement and a 28% reduction in death risk.
The doublet therapy wasn't far behind, hitting 24.4 months median survival. It showed a 20% reduction in death risk, though it narrowly missed the threshold for statistical significance with a p-value of 0.0564. (For context, the magic number is usually 0.05 or below.) Still, the trend strongly favored Ziihera, and Jazz is planning another interim analysis for mid-2026 that could firm up those numbers.
Why This Matters
"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 from Princess Margaret Cancer Centre. She's not exaggerating—in advanced stomach cancers, every additional month of survival is meaningful, and getting past the two-year mark in a large trial is genuinely noteworthy.
For patients with this type of cancer, these results suggest Ziihera could become a new standard of care if regulators approve it. For Jazz Pharmaceuticals, it's a potential blockbuster in the making.
JAZZ Price Action: Jazz Pharmaceuticals shares were up 2.07% at $170.44 at the time of publication on Wednesday.