Jazz Pharmaceuticals has released new data indicating that its HER2 antibody Ziihera significantly improves survival outcomes for patients with locally advanced or metastatic gastroesophageal adenocarcinoma. The results come from the Phase III HERIZON-GEA-01 trial, which evaluated two combinations of Ziihera: one with chemotherapy and another adding BeOne’s Tevimbra. The control group received Herceptin with chemotherapy, and over 900 patients participated in the study.
The company reported a 35% reduction in the risk of disease progression or death when patients were treated with Ziihera and chemotherapy. Adding Tevimbra further improved this outcome, raising the reduction to 37%. Both regimens extended median progression-free survival by more than four months compared to the Herceptin-based control group.
Analysts at Truist Securities described these results as “practice-changing,” emphasizing that they showed “the strongest OS signals ever reported” in randomized studies of first-line HER2-positive gastroesophageal adenocarcinoma. They added, “The triplet’s >7-mo [median OS] improvement is practice-changing in any GI setting.”
Truist analysts also noted Ziihera’s median duration of response: 14.3 months for the doublet regimen and 20.7 months for the triplet regimen. Safety data indicated that adverse events were consistent with what is already known about Ziihera, with no new concerns identified. Grade 3 or higher treatment-related adverse events occurred in 59.6% of patients on the doublet regimen and 71.8% on the triplet.
“Beating a high-performing trastuzumab [Herceptin] control,” said Truist analysts, “strongly supports HER2 backbone replacement, not niche use.”
Chief Medical Officer Rob Iannone stated that Jazz plans to “move rapidly toward FDA submission.” The company will also present these findings at the upcoming 2026 ASCO Gastrointestinal Cancers Symposium.
Ziihera is administered intravenously and functions as a bispecific antibody binding to two sites on the HER2 protein, disrupting signaling pathways involved in cancer cell growth and tumor development. In November 2024, Ziihera received accelerated approval from the FDA for unresectable or metastatic HER2-positive biliary tract cancer. Jazz continues to develop Ziihera for other cancers such as breast cancer and colorectal carcinoma.
In addition to progress with Ziihera, Jazz had notable developments in 2025 following its acquisition of Chimerix in March. This included gaining dordaviprone (now marketed as Modeyso) for glioma treatment; new findings were presented in May and FDA approval was secured in August.
