Jazz Pharmaceuticals PLC’s stock gained 2.3% on Tuesday after the U.S. Food and Drug Administration approved Ziihera for the first-line treatment of adult patients with unresectable locally advanced or metastatic HER2-positive gastroesophageal junction or gastric adenocarcinoma.
The FDA cleared Ziihera in two regimens: combined with Tevimbra and chemotherapy containing fluoropyrimidine and platinum for HER2+ IHC 3+ and IHC 2+/ISH+ patients, and with chemotherapy alone for HER2+ IHC 3+ patients. The approval applies to all HER2+ gastric or gastroesophageal junction cancer patients regardless of PD-L1 status.
Ziihera is the first HER2-targeted bispecific antibody paired with a PD-1 inhibitor and chemotherapy approved for this indication. Approximately 20% of gastric and gastroesophageal junction adenocarcinoma patients in the U.S. are HER2-positive, with more than 31,000 new stomach cancer cases diagnosed annually.
The approval was supported by Phase 3 trial HERIZON-GEA-01 results. Both Ziihera-containing regimens reduced the risk of disease progression or death by 35%, extending median progression-free survival to 12.4 months versus 8.1 months in the comparator arm receiving trastuzumab plus chemotherapy. In the overall HER2+ population, the combination of Ziihera with tislelizumab and chemotherapy cut the risk of death by 28%, achieving a median overall survival of 26.4 months compared with 19.2 months for trastuzumab plus chemotherapy. Jazz Pharmaceuticals noted this as the highest median overall survival recorded in a Phase 3 study for advanced HER2+ gastric or gastroesophageal junction cancer.
Diarrhea was the most common adverse reaction, managed with antidiarrheals and dose adjustments, with few discontinuations attributed to Ziihera.
