Investing.com -- Jazz Pharmaceuticals PLC (NASDAQ:JAZZ) stock fell 4.5% on Tuesday after the company announced positive Phase 3 trial results for its cancer drug Ziihera that showed mixed benefits when combined with immunotherapy.
The HERIZON-GEA-01 trial evaluated Ziihera (zanidatamab-hrii) in combination with chemotherapy, with or without the PD-1 inhibitor Tevimbra (tislelizumab), as a first-line treatment for HER2-positive gastroesophageal adenocarcinoma. While both treatment arms showed statistically significant improvement in progression-free survival compared to the control arm, the addition of tislelizumab provided only modest additional benefit over Ziihera plus chemotherapy alone.
Both investigational arms achieved a median progression-free survival of 12.4 months, representing more than four months improvement versus the control arm of trastuzumab plus chemotherapy. The Ziihera plus tislelizumab and chemotherapy arm demonstrated a statistically significant overall survival benefit with a median of 26.4 months compared to 19.2 months in the control arm.
However, the Ziihera plus chemotherapy arm without tislelizumab showed a median overall survival of 24.4 months, which did not reach statistical significance at the first interim analysis. An additional planned analysis is expected in mid-2026.
"We think the sell-off is related to the triplet arm barely outperforming the doublet arm. However, we believe it is the wrong take to view this as a disappointment. We think this is actually a positive as it indicates that zanidatamab is doing most of the heavy lifting to improve outcomes, regardless of PD-L1 status, and should be used instead of Herceptin whether a patient is treated with PD-1 or not," commented Baird analyst Brian Skorney.
The safety profile was consistent with known effects of HER2-directed therapy and immunotherapy, with no new safety signals identified. The most common Grade ≥3 treatment-related adverse event was diarrhea.
Jazz plans to present the data at the 2026 ASCO Gastrointestinal Cancers Symposium on January 8, 2026, and will host an investor webcast the following day.
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