Patients newly diagnosed with an aggressive cancer of the stomach, esophagus or the junction between them now have two additional treatment options at the very start of care. Federal regulators approved two combinations featuring Ziihera, the brand name for zanidatamab, for adults with unresectable, locally advanced, or metastatic HER2-positive gastroesophageal adenocarcinoma.
The FDA also approved two companion diagnostic devices to identify eligible patients: the PATHWAY anti-HER2/neu antibody test and the VENTANA HER2 Dual ISH DNA Probe Cocktail, according to oncology coverage of the decision. That pairing matters more than it sounds, because eligibility here depends entirely on a tumor test result rather than on symptoms or stage alone.
For a patient sitting in an oncology office next week, the practical change is what the first treatment conversation can now include. Roughly 20 percent of gastroesophageal adenocarcinomas are HER2 positive, and the outlook for metastatic disease has remained poor, with global five-year survival under 10 percent.
Which Patients the Approval Actually Covers
The two regimens are not interchangeable, and the distinction turns on how strongly a tumor tests positive for HER2.
The first combination pairs Ziihera with Tevimbra, the brand name for tislelizumab, along with fluoropyrimidine and platinum-based chemotherapy. It is approved for patients whose tumors test HER2-positive by immunohistochemistry 3+ or by 2+ with a positive in situ hybridization result. The second combination pairs Ziihera with chemotherapy alone and is approved only for tumors at 3+.
Notably, the immunotherapy-containing regimen was approved regardless of PD-L1 status, a protein level that often determines whether immunotherapy is offered in other cancers. Rob Iannone, chief medical officer at Jazz Pharmaceuticals, which markets the drug, described the regimen as approved "for all HER2+ advanced GEA patients, regardless of PD-L1 status."
That framing comes from the company. Geoffrey Ku of Memorial Sloan Kettering Cancer Center, a co-author on the supporting trial, said "similar outcomes were seen in patients whose tumors were PD-L1 positive or negative," suggesting the regimen could benefit a broad range of patients. Ku's financial interests related to Jazz are disclosed in the company's announcement, which is worth weighing alongside the statement.
The Trial Numbers Behind the Decision
The approval rests on the phase 3 HERIZON-GEA-01 trial, which randomly assigned 914 patients and was published in the New England Journal of Medicine after first being presented at a gastrointestinal cancers meeting earlier this year. Regulators reviewed the application through a real-time oncology review pathway that lets the agency examine data as it arrives rather than waiting for a complete submission, according to CancerNetwork.
Both Ziihera combinations significantly improved progression-free survival compared with trastuzumab plus chemotherapy, the previous standard. Median progression-free survival reached 12.4 months versus 8.1 months, a 35 percent reduction in the risk of disease progression or death.
For the immunotherapy-containing regimen, median overall survival reached 26.4 months compared with 19.2 months, corresponding to a 28 percent reduction in the risk of death. Crossing two years of median survival in metastatic disease is a meaningful shift in a setting where that number has been stubbornly low.
The safety picture requires equal attention. Grade 3 or higher adverse events occurred in 83.3 percent of patients on the immunotherapy regimen, 73.8 percent on Ziihera plus chemotherapy, and 74.5 percent on the comparison arm, as summarized in trial reporting. Diarrhea was the most common grade 3 or higher event, and the US prescribing information carries boxed warnings for diarrhea and embryo-fetal toxicity.
Trial investigators used preventive loperamide during the first cycle and managed diarrhea with antidiarrheal medicines and dose adjustments, which the company reports resulted in few discontinuations. The label also flags decreases in heart pumping function and infusion-related reactions. That is a real clinical burden that patients should expect to discuss before starting.
Testing Determines Access Before Treatment Does
Because eligibility depends on a specific tumor test result, the approval process creates a practical bottleneck that patients and families should understand early on. A tumor sample must be tested for HER2 using an FDA-authorized test, and the result determines which of the two regimens, if either, is available.
Patients diagnosed at community oncology practices should ask directly whether HER2 testing has been done, which test was used, and what the result was. In cancers where biomarker testing determines access to a newer regimen, testing rates have historically lagged at smaller centers compared with academic hospitals.
Cost and coverage remain open questions. Jazz has not published pricing for the new combinations, and insurance policies typically take weeks to months to reflect a new indication. Patients facing a coverage denial can ask their oncology team about prior authorization, appeals, and manufacturer patient assistance programs.
The regimens involve infusions of at least three agents, which means treatment days are long and travel to an infusion center is frequent. For families in rural areas, that logistical load is part of the real cost of a new standard of care.
Open Questions the Trial Has Not Answered
The HERIZON-GEA-01 trial is still ongoing, with additional analyses planned. Longer-term survival data are not yet available, and the durability of the benefit past the reported medians is unknown.
The trial compared the new regimens against trastuzumab plus chemotherapy. It did not compare them head-to-head against every other regimen a physician might consider, so the ranking among newer options is not settled by this study alone.
Ziihera previously received accelerated approval in November 2024 for adults with previously treated HER2-positive biliary tract cancer, as noted in oncology coverage, and it remains approved in the European Union and other countries. Regulators elsewhere have not all acted on the gastroesophageal indication.
Gastroesophageal adenocarcinoma is the fifth most common cancer worldwide, and more than 31,000 new stomach cancer cases are diagnosed annually in the United States, according to American Cancer Society figures cited by Jazz. Symptoms of these cancers are often vague early on, which is part of why so many are diagnosed at an advanced stage.
Patients should not interpret this approval as a reason to change an existing treatment plan on their own. Anyone currently receiving therapy for HER2-positive gastroesophageal cancer should raise the new options at their next appointment rather than adjusting anything independently. Updated prescribing information and eventual guideline revisions from major oncology bodies are the next developments worth watching.
Key Questions Answered
What exactly was approved? Two Ziihera-containing regimens for first-line treatment of adults with unresectable locally advanced or metastatic HER2-positive gastroesophageal adenocarcinoma, plus two companion diagnostic devices to identify eligible patients.
Who qualifies for each regimen? Ziihera with tislelizumab and chemotherapy is approved for tumors testing HER2 positive at IHC 3+ or IHC 2+ with positive in situ hybridization. Ziihera with chemotherapy alone is approved for IHC 3+ tumors.
How much did survival improve? In the supporting trial, median overall survival with the immunotherapy-containing regimen reached 26.4 months versus 19.2 months, and median progression-free survival reached 12.4 months versus 8.1 months.
What are the main side effects? Diarrhea was the most common grade 3 or higher adverse event. The prescribing information carries boxed warnings for diarrhea and embryo-fetal toxicity. Grade 3 or higher events occurred in the majority of patients across all arms.
Does PD-L1 status matter? The immunotherapy-containing regimen was approved regardless of PD-L1 status. Trial investigators reported similar outcomes in PD-L1 positive and negative patients.
What should a patient ask their oncologist? Whether HER2 testing has been performed, which FDA-authorized test was used, what the specific result was, and whether either regimen fits their situation.
Is pricing or insurance coverage known? No pricing has been published for the new combinations, and coverage policies typically take time to reflect a new indication. Patients can ask about prior authorization, appeals, and patient assistance programs.
