# KEYNOTE-859

Source: https://onco.cc/trials/keynote-859/  
OnCo record `keynote-859` (Trial). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Confirmed that adding a PD-1 blocker to first-line chemotherapy helps in stomach cancer, with the biggest gain in tumours rich in PD-L1.

## Summary

KEYNOTE-859, trial NCT03675737 sponsored by Merck and reported in 2023, confirmed that adding the PD-1 antibody pembrolizumab to first-line chemotherapy helps in HER2-negative advanced gastric and gastro-oesophageal junction adenocarcinoma, with the biggest gain in tumours rich in PD-L1. It randomised 1,579 patients and met its primary overall survival endpoint in all randomised patients, with progressively larger effects at CPS 1 and CPS 10 or higher, leading to FDA approval in November 2023 for all PD-L1 levels while the EMA restricted it to CPS 1 or higher. OnCo links it to gastric cancer, PD-1 as a target, pembrolizumab, the CPS term and Sun Young Rha, and it replicates CheckMate 649. As with its predecessor, whether PD-L1-negative patients should receive immunotherapy is the open question the regional labels disagree on.

## Fields

- Kind: Trial
- Status: positive
- Last checked: 2026-09-07
- Registry id: NCT03675737
- Phase: 3
- Setting: First-line HER2-negative advanced gastric/GEJ adenocarcinoma: pembrolizumab + chemotherapy vs placebo + chemotherapy
- Sponsor: Merck
- Enrolled: 1579
- Result: OS HR 0.78 (all); CPS ≥10 OS 15.7 vs 11.8 months (HR 0.65).
- Outcomes: Overall survival, all randomised: Pembrolizumab + chemotherapy 12.9 months vs Placebo + chemotherapy 11.5 months, HR 0.78; Overall survival, CPS ≥10: Pembrolizumab + chemotherapy 15.7 months vs Placebo + chemotherapy 11.8 months, HR 0.65
- Replication: Replicates CheckMate 649.

## Sources

- ClinicalTrials.gov NCT03675737: https://clinicaltrials.gov/study/NCT03675737

## Connected records

- cancers: [Gastric & gastro-oesophageal junction cancer](https://onco.cc/cancers/gastric/), [Microsatellite-unstable (MSI-high) gastric cancer](https://onco.cc/cancers/gastric-msi-high/), [PD-L1-high gastric cancer](https://onco.cc/cancers/gastric-pdl1-high/)
- technologies: [Immune checkpoint inhibitors](https://onco.cc/technologies/checkpoint-inhibitor/)
- targets: [PD-1](https://onco.cc/targets/pd1/)
- drugs: [Pembrolizumab](https://onco.cc/drugs/pembrolizumab/)
- companies: [Merck & Co. (MSD)](https://onco.cc/companies/merck/)
- terms: [Combined positive score (CPS)](https://onco.cc/terms/cps/)
- people: [Sun Young Rha](https://onco.cc/people/rha-sun-young/)
- key papers: [KEYNOTE-859: pembrolizumab plus chemotherapy versus placebo plus chemotherapy for HER2-negative advanced gastric cancer](https://onco.cc/key-papers/paper-keynote-859-lancet-oncol-2023/)

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