Jazz Pharmaceuticals Receives FDA Priority Review for Ziihera® in Gastric Cancer Treatment

Jazz Pharmaceuticals plc (Nasdaq: JAZZ) has announced a significant development regarding Ziihera® (zanidatamab-hrii), a bispecific antibody that targets HER2-positive cancers. On April 27, 2026, the U.S. Food and Drug Administration (FDA) accepted the supplemental Biologics License Application (sBLA) for priority review. This milestone is critical for adults diagnosed with unresectable locally advanced or metastatic gastric, gastroesophageal junction (GEJ), or gastroesophageal adenocarcinoma (GEA) that are HER2-positive (HER2+). The FDA has set a target action date for this review under the Prescription Drug User Fee Act (PDUFA) on August 25, 2026.

The acceptance by the FDA is underpinned by robust data garnered from the HERIZON-GEA-01 trial. This pivotal study evaluated zanidatamab's efficacy and safety in combination with standard chemotherapy, with or without the addition of Tevimbra® (tislelizumab), a PD-1 inhibitor. This trial is noteworthy as it marks the first immuno-oncology combination demonstrating efficacy across both PD-L1–positive and PD-L1–negative tumor settings within this clinical framework.

Rob Iannone, the executive vice president and chief medical officer at Jazz Pharmaceuticals, emphasized the potential of zanidatamab as a leading therapy for HER2+ GEA. He highlighted the fact that the results from the trials indicated enhanced clinical benefits when tislelizumab was introduced into the treatment regimen.

The implications of this research are profound considering GEA is the fifth most prevalent cancer globally. Alarmingly, approximately 20% of these cases are HER2+, a factor associated with increased morbidity and mortality. At present, the prognosis for GEA patients is dismal, with a five-year survival rate of less than 30% for gastric cancer, and around 19% for GEA.

The HERIZON-GEA-01 trial involved a significant pool of patients—914 individuals across roughly 300 clinical sites in over 30 countries—solidifying the robustness of its findings. Participants were categorized into three trial arms: receiving zanidatamab combined with chemotherapy plus tislelizumab; zanidatamab paired solely with chemotherapy; and the traditional trastuzumab alongside chemotherapy. The trial’s dual primary endpoints included progression-free survival (PFS) and overall survival (OS).

FDA granted Breakthrough Therapy designation to zanidatamab in combination with chemotherapy, underscoring its potential to substantially improve treatment outcomes over existing options. This designation aims to accelerate the development and review process for therapies that demonstrate significant improvement based on preliminary clinical evidence, ensuring timely access to promising treatments for patients with serious conditions.

About the biopharmaceutical Ziihera: it acts on two extracellular HER2 domains, leading to a reduction in HER2 expression on tumor cells. By utilizing multiple cellular mechanisms, it induces cytotoxic effects that inhibit tumor growth. In the U.S., Ziihera is already indicated for patients with HER2-positive biliary tract cancer (BTC) who have received prior treatment. This application was accelerated based on initial clinical outcomes, highlighting the importance of ongoing trials to confirm efficacy.

As Jazz Pharmaceuticals advances its mission to innovate and transform patients’ lives with rare diseases, zanidatamab exemplifies their commitment to developing effective therapies where there are few to no options available. The company aims to expedite the process of bringing this promising treatment to market following active collaboration with the FDA.

In summary, Jazz Pharmaceuticals stands at the forefront of potentially reshaping the treatment landscape for HER2+ gastric cancer thanks to the FDA's acceptance of its supplemental application for Ziihera, a development that could provide new hope to patients in dire need of effective therapies.