IPM Take
This is a precision-oncology approval with a companion-diagnostic backbone. The label depends on HER2 status, and FDA also approved Roche/Ventana companion diagnostic devices. That means pathology capacity, test quality, turnaround time and reimbursement are not secondary details. They are the front door to treatment.
Executive Summary
The FDA approved zanidatamab-hrii, marketed as Ziihera, for two first-line treatment approaches in adults with HER2-positive unresectable locally advanced or metastatic gastric, gastroesophageal junction or esophageal adenocarcinoma. One indication combines zanidatamab with fluoropyrimidine- and platinum-containing chemotherapy plus tislelizumab; the other combines zanidatamab with chemotherapy in HER2 IHC 3+ disease. FDA also approved two companion diagnostic devices to identify eligible patients. In HERIZON-GEA-01, the zanidatamab, tislelizumab and chemotherapy arm improved median overall survival to 26.4 months versus 19.2 months with trastuzumab and chemotherapy, and median progression-free survival to 12.4 months versus 8.1 months.
Why it matters
- Patients / advocates: Eligible patients need HER2 testing early enough to shape first-line care, not after treatment has already started.
- Diagnostics / pathology: Companion diagnostics are now part of the treatment architecture. Test quality is access.
- Clinicians: The approval changes first-line choices in HER2-positive gastroesophageal adenocarcinoma.
- Payers / HTA bodies: The value case must include drug cost, testing cost, chemotherapy backbone, immunotherapy component and real-world eligibility.
The first decision in this story does not happen in the infusion chair. It happens in the lab.
FDA’s approval of zanidatamab-based regimens for HER2-positive gastric, gastroesophageal junction and esophageal adenocarcinoma is a serious treatment advance. The strongest survival signal came from the zanidatamab, tislelizumab and chemotherapy arm in HERIZON-GEA-01: 26.4 months median overall survival versus 19.2 months with trastuzumab plus chemotherapy.
That number will get the attention. But the operational story is HER2.
FDA’s label depends on HER2 positivity, and the agency also approved companion diagnostic devices for identifying eligible patients. This is where many cancer systems either succeed quietly or fail invisibly. If HER2 testing is delayed, underfunded, poorly standardised or not connected to first-line treatment decisions, the approval becomes theoretical for the patient in front of the clinician.
Gastroesophageal cancer is already a difficult pathway. Patients can be symptomatic, nutritionally fragile and clinically deteriorating. Waiting for diagnostic clarification is not a harmless pause. It can become a lost treatment window.
There is also a fairness issue. High-volume centres may already have reliable IHC and ISH workflows, rapid reporting and multidisciplinary review. Smaller centres may not. A companion-diagnostic approval does not solve that gap. It exposes it.
The approval should be welcomed. But the implementation test is brutally clear: can systems identify HER2-positive patients early, accurately and consistently enough for this regimen to matter?
