Study summary

A two-site HER2 antibody beat trastuzumab as first treatment for HER2-positive cancer

HERIZON-GEA-01 trial · 914 people, phase 3 · FDA approved August 25, 2026

26.4 momedian survival with zanidatamab, tislelizumab and chemo, vs 19.2

What was tested

Zanidatamab, an antibody that binds two sites on HER2, with chemotherapy with or without tislelizumab, against trastuzumab plus chemotherapy, for advanced HER2-positive stomach, junction or esophageal adenocarcinoma.

What they found

With tislelizumab, median survival was 26.4 vs 19.2 months and time before growth 12.4 vs 8.1 months.
Without tislelizumab, in strongly HER2-positive (IHC 3+) tumors, time before growth was 14.2 vs 7.6 months.

What it means

Replaces trastuzumab as the HER2 backbone for first treatment of HER2-positive disease.

ASCO Post ↗ ← Back to the outlook

Last reviewed 2026-11-14 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.