Jazz Pharmaceuticals Announces Key Data on Ziihera® at ASCO GI 2026

On December 2, 2025, Jazz Pharmaceuticals plc (Nasdaq: JAZZ) made a significant announcement regarding the upcoming presentation of crucial data for Ziihera® (zanidatamab-hrii) at the 2026 American Society of Clinical Oncology Gastrointestinal Cancers Symposium (ASCO GI). The symposium, scheduled from January 8-10, 2026, in San Francisco, will feature two abstracts that highlight the promising results of Ziihera in treating first-line HER2-positive locally advanced or metastatic gastroesophageal adenocarcinoma (GEA).

Jazz Pharmaceuticals revealed that the Phase 3 HERIZON-GEA-01 trial results have been accepted as a late-breaking presentation. This trial aims to evaluate the efficacy of Ziihera in combination with chemotherapy, with or without the PD-1 inhibitor Tevimbra® (tislelizumab), as a first-line treatment for patients with HER2+ locally advanced or metastatic GEA. Alongside this, a new post-hoc overall survival analysis from the HERIZON-BTC-01 Phase 2b trial concerning previously treated HER2+ biliary tract cancer (BTC) will also be showcased.

Dr. Rob Iannone, Executive Vice President and Chief Medical Officer of Jazz Pharmaceuticals, expressed enthusiasm about sharing the results. "We look forward to sharing the clinically meaningful results from the Phase 3 HERIZON-GEA-01 trial with the oncology community at ASCO GI," he stated. He emphasized the urgent need for advancements in treating advanced HER2+ GEA, a type of cancer known for its aggressive nature and poor prognosis.

The HERIZON-GEA-01 trial, conducted in collaboration with BeOne Medicines, has shown promising results. The combination of Ziihera with chemotherapy and tislelizumab demonstrated statistically significant improvements in progression-free survival (PFS) compared to the control group receiving trastuzumab plus chemotherapy. Additionally, the Ziihera plus tislelizumab and chemotherapy combination exhibited noteworthy overall survival (OS) benefits, while Ziihera with chemotherapy showed a positive trend toward OS significance.

Dr. Iannone noted the potential of Ziihera to be established as "the HER2-targeted agent-of-choice," suggesting that these combinations could set a new standard of care for patients with HER2+ first-line metastatic GEA, independent of PD-L1 status.

In conjunction with the ASCO GI presentations, Jazz Pharmaceuticals will host an investor webcast on January 9, 2026, at 6:30 a.m. PT/9:30 a.m. ET. The webcast will feature discussions from senior management and Dr. Geoffrey Ku, an Associate Attending Physician at Memorial Sloan Kettering Cancer Center. Investors and stakeholders are encouraged to register early for the event.

GEA remains a critical area of need in oncology, being the fifth most common cancer worldwide. Approximately 20% of GEA cases are HER2-positive, and the prognosis for these patients is bleak, with a five-year survival rate of less than 30%. On the other hand, BTC, which includes gallbladder cancer and cholangiocarcinoma, poses similarly severe challenges. HER2-positive BTC, identified in about 26% of patients, is particularly associated with poorer outcomes.

Ziihera (zanidatamab-hrii) is a bispecific HER2-directed antibody designed to combat tumors expressing HER2. Its mechanisms of action include inducing cytotoxicity and promoting tumor growth inhibition. Recently approved for use in previously treated HER2-positive BTC, Ziihera has received accolades for its potential in transforming the treatment landscape for these aggressive cancers.

As Jazz Pharmaceuticals prepares to unveil pivotal data on Ziihera at ASCO GI 2026, the oncology community eagerly awaits insights that could reshape treatment protocols for patients battling HER2-positive gastroesophageal adenocarcinoma and biliary tract cancer. The anticipated results not only highlight the company's commitment to innovation in cancer therapies but also promise hope for patients in dire need of effective treatment options.