Jazz Reports Survival Benefit for Ziihera in GEA

Dublin, Ireland, August 31, 2026

Ziihera Combination Improves Overall Survival

The HERIZON-GEA-01 Phase 3 trial evaluated Ziihera in combination with chemotherapy against trastuzumab plus chemotherapy in patients with previously untreated, HER2-positive advanced GEA. According to Jazz Pharmaceuticals, the study achieved its prespecified overall survival endpoint, demonstrating a statistically significant improvement for patients receiving the Ziihera-based regimen. Overall survival is a key endpoint in advanced cancer trials because it measures the length of time patients remain alive following treatment initiation. The positive result indicates that the Ziihera combination may provide a clinically meaningful benefit compared with the established trastuzumab-based treatment approach in the first-line setting. The trial forms part of the clinical development program for zanidatamab, a HER2-targeted bispecific antibody designed to bind two distinct sites on the HER2 receptor. By engaging HER2 through dual binding, zanidatamab is intended to produce multiple antitumor effects, including receptor clustering, internalization and immune-mediated mechanisms. The investigational strategy is designed to provide a differentiated approach to HER2-targeted therapy. The positive overall survival result builds on the established role of HER2-directed treatment in patients with HER2-positive advanced gastric and gastroesophageal cancers. However, detailed numerical overall survival data and additional efficacy outcomes from the trial are expected to provide further context for assessing the magnitude and clinical relevance of the treatment benefit.

HER2-Positive Advanced GEA Remains Challenging

Gastric and gastroesophageal adenocarcinoma are aggressive gastrointestinal malignancies, and patients with advanced disease often face limited treatment options and poor long-term outcomes. HER2 is an important biomarker in a subset of these cancers and has become a clinically relevant therapeutic target. Trastuzumab-based treatment has been an established component of first-line therapy for HER2-positive advanced GEA, creating a benchmark against which newer HER2-targeted approaches can be evaluated. Ziihera is designed to target HER2, a receptor involved in signaling pathways that can promote tumor-cell growth and survival. Zanidatamab’s bispecific design enables it to simultaneously engage two separate epitopes of HER2. This mechanism distinguishes the therapy from conventional monoclonal antibodies that bind a single region of the receptor. The HERIZON-GEA-01 findings are therefore significant not only because of the reported overall survival improvement, but also because they support continued investigation of next-generation HER2-targeted therapies in gastrointestinal oncology. A successful first-line strategy could potentially influence treatment sequencing and expand options for patients whose tumors demonstrate HER2 positivity.

Results Support Continued Regulatory Progress

The statistically significant overall survival finding represents a major milestone for Jazz Pharmaceuticals and the Ziihera development program. The company is expected to provide additional details from the Phase 3 study, including the magnitude of the survival benefit, other efficacy endpoints and safety findings, to support broader scientific and regulatory evaluation. Ziihera, also known as zanidatamab-hrii, is already an important component of Jazz Pharmaceuticals’ oncology portfolio, and the new Phase 3 data could potentially support expansion of its use in HER2-positive advanced GEA. Regulatory decisions will ultimately depend on comprehensive review of the clinical data and applicable requirements. The HERIZON-GEA-01 results highlight the continuing evolution of HER2-targeted cancer therapy, particularly through antibody designs intended to engage the target through multiple mechanisms. If the findings are confirmed through the complete dataset and accepted by regulatory authorities, Ziihera plus chemotherapy could represent an important advancement in the first-line management of patients with HER2-positive advanced gastric or gastroesophageal adenocarcinoma.

Source: Jazz Pharmaceuticals press relese