OnCo
trialsTrialPositive

HERIZON-GEA-01

A two-armed HER2 antibody beat Herceptin head-to-head as first-line treatment for HER2-positive stomach cancer, the first such win since 2010.

PFS 12.4 months in both zanidatamab arms vs 8.1 months with trastuzumab (HR ~0.63 and 0.65); OS significantly improved in both arms (NEJM 2026). Supplemental BLA planned in the first half of 2026. Sets up zanidatamab as the HER2 agent of choice and raises the question of how T-DXd fits after it.

Setting
First-line HER2-positive advanced gastro-oesophageal adenocarcinoma: zanidatamab + chemotherapy ± tislelizumab vs trastuzumab + chemotherapy
Phase
Phase 3
Sponsor
Jazz / BeOne
Registry
Headline result
PFS 12.4 vs 8.1 months (HR 0.63-0.65); OS significantly improved.
Reported
2026
Enrolled
914
Replication
First phase 3; consistent with phase 2 (ORR 76% first line).

Outcomes

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In plain words
What these results mean for people, not percentages
914 people took part
Progression-free survivalprimarysurrogate endpoint
  • Median 12.4 vs 12.4 months with Zanidatamab + chemotherapy + tislelizumab compared with Zanidatamab + chemotherapy; about 0 months longer for half the group.
  • A median is a midpoint: half the people did better than this and half did worse, so it is not a prediction for any one person.
  • Other groups: Trastuzumab + chemotherapy 8.1 months.
  • This is a surrogate endpoint: it measures the cancer being controlled or absent on scans and tests, which often, but not always, translates into living longer.
  • These results apply to the people the trial enrolled: First-line HER2-positive advanced gastro-oesophageal adenocarcinoma: zanidatamab + chemotherapy ± tislelizumab vs trastuzumab + chemotherapy. People in a different situation may not see the same effect.
  • The trial selected people by a biomarker (HER2); the result should not be assumed for people whose cancer does not have it.

Numbers are from the trial as recorded here; see the source links in the table below. This is orientation, not medical advice: ask your team how closely the trial population matches you.

914 participants enrolled.

Progression-free survivalprimary
Zanidatamab + chemotherapy + tislelizumab
12.4 mo
Zanidatamab + chemotherapy
12.4 mo
Trastuzumab + chemotherapy
8.1 mo
Source
EndpointArmnValueHR (95% CI)pSource
Progression-free survivalprimaryZanidatamab + chemotherapy + tislelizumab12.4 monthslink
Zanidatamab + chemotherapy12.4 months
Trastuzumab + chemotherapy8.1 months
Replication
First phase 3; consistent with phase 2 (ORR 76% first line).

Connected

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