FDA approves Ziihera-based first-line regimens for HER2-positive advanced gastroesophageal cancers

The approvals introduce zanidatamab-based first-line options for adults with HER2-positive unresectable locally advanced or metastatic gastric, gastroesophageal junction or oesophageal adenocarcinoma, with treatment determined by HER2 status.

The US Food and Drug Administration (FDA) has approved Ziihera (zanidatamab-hrii) with fluoropyrimidine- and platinum-containing chemotherapy plus Tevimbra (tislelizumab-jsgr) as first-line treatment for adults with HER2-positive (IHC 3+ or IHC 2+/ISH+) unresectable locally advanced or metastatic gastric, gastroesophageal junction or oesophageal adenocarcinoma, while Ziihera plus chemotherapy was approved for the HER2 IHC 3+ population.

The decisions establish zanidatamab-based treatment in the first-line setting, supported by HERIZON-GEA-01 data showing significant progression-free and overall survival improvements for the Ziihera, Tevimbra and chemotherapy regimen versus trastuzumab plus chemotherapy.

Field	Content
Alert Type	Drug Approval
Drug Name	Ziihera (zanidatamab-hrii); Tevimbra (tislelizumab-jsgr)
Indication	Ziihera plus Tevimbra and fluoropyrimidine- and platinum-containing chemotherapy: first-line treatment of adults with HER2-positive (IHC 3+ or IHC 2+/ISH+) unresectable locally advanced or metastatic gastric, gastroesophageal junction or oesophageal adenocarcinoma, as detected by an FDA-approved test. Ziihera plus fluoropyrimidine- and platinum-containing chemotherapy: first-line treatment of adults with HER2-positive (IHC 3+) disease in the same settings. (fda.gov)
Therapy Area(s)	Oncology; Gastrointestinal cancers
Geography	United States (FDA)
What Happened	On 25 August 2026, the FDA approved two Ziihera-based first-line regimens for HER2-positive advanced gastroesophageal adenocarcinoma. Ziihera plus Tevimbra and fluoropyrimidine/platinum chemotherapy was approved for HER2 IHC 3+ or IHC 2+/ISH+ tumours, while Ziihera plus fluoropyrimidine/platinum chemotherapy was approved for HER2 IHC 3+ tumours. The FDA simultaneously approved Roche Diagnostics' PATHWAY anti-HER-2/neu (4B5) Rabbit Monoclonal Primary Antibody and VENTANA HER2 Dual ISH DNA Probe Cocktail as companion diagnostics for identifying eligible patients consistent with the Ziihera label. (fda.gov)
Why It Matters	The approval moves zanidatamab into first-line treatment for HER2-positive advanced gastric, gastroesophageal junction and oesophageal adenocarcinoma and provides a treatment option combining HER2-directed therapy with PD-1 inhibition and chemotherapy for eligible patients. HER2 testing is central to treatment selection because eligibility for the two approved regimens differs according to IHC and ISH status. (fda.gov)
Supporting Context	Approval was supported by the global HERIZON-GEA-01 trial. In patients with HER2 IHC 3+ or IHC 2+/ISH+ tumours, Ziihera plus Tevimbra and chemotherapy produced median overall survival of 26.4 months versus 19.2 months with trastuzumab plus chemotherapy (HR 0.72), while median progression-free survival was 12.4 versus 8.1 months (HR 0.63). Ziihera plus chemotherapy also significantly improved PFS versus the trastuzumab regimen, with exploratory analysis indicating that this effect was primarily attributable to patients with IHC 3+ tumours. (fda.gov)
Key Takeaway	The FDA approvals establish Ziihera-based first-line treatment for HER2-positive advanced gastroesophageal adenocarcinoma, with the addition of Tevimbra extending the regimen to eligible IHC 2+/ISH+ as well as IHC 3+ disease. (fda.gov)
What to Watch	The review was conducted through Project Orbis in collaboration with Health Canada and the UK's MHRA, where reviews remain ongoing, making subsequent regulatory decisions in Canada and the UK the principal near-term developments to watch. (fda.gov)
Primary Source	FDA approval announcement
Relevant Date	25 August 2026

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