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EP4 Antagonist ONO-4578 Plus Nivolumab and Chemotherapy in HER2-Negative Unresectable Advanced or Recurrent Gastric or Gastroesophageal Junction Cancer

I. Nakayama, Min-Hee Ryu, Sung-Hee Lim, Jong Gwang Kim, Takeshi Omori, S. Oh, Jin Young Kim, S. Rha et al.

Journal of Clinical Oncology, 2026

226 participants · 1 citation

Abstract

PURPOSE

EP4, a key receptor in the PGE2 axis, mediates tumor immunosuppression; the EP4 antagonist ONO-4578 plus nivolumab showed manageable safety, immune activation, and preliminary antitumor activity in previously treated gastric/gastroesophageal junction cancer (G/GEJC). This study explored whether ONO-4578 enhances the efficacy of nivolumab plus chemotherapy in unresectable advanced or recurrent G/GEJC.

PATIENTS AND METHODS

This multicenter, double-blind, randomized phase 2 study enrolled chemotherapy-naïve patients with HER2-negative unresectable advanced or recurrent G/GEJC. Patients were randomized (2:1) to receive oral ONO-4578 or matching placebo, each in combination with nivolumab and oxaliplatin-based chemotherapy. The primary endpoint was investigator-assessed progression-free survival (PFS). Secondary endpoints included overall survival (OS), objective response rate (ORR), and safety.

RESULTS

At the data cutoff, 226 patients were randomized to the ONO-4578 group (n = 150) and the placebo group (n = 76). Adding ONO-4578 significantly improved PFS (hazard ratio of 0.67; 90% confidence interval, 0.48-0.92; p-value, 0.040 [prespecified two-sided α = 0.10]), with favorable OS at a prespecified analysis with limited follow-up (hazard ratio of 0.60; 95% confidence interval, 0.37-0.96) and ORR (62.0% vs 48.7%). Exploratory subgroup analyses suggested that ONO-4578 regimen provided greater benefit in PD-L1 CPS ≥1, whereas no clear benefit in CPS <1/indeterminate…

How strong is the evidence?

Evidence Hub reads this as a randomized trial, done in people. Its evidence level is 2 of 5 (High · randomized trial). Randomized trials of a reasonable size are the strongest single-study design. Reported size: 226 participants or records.

How the five levels of evidence work. The level is assigned automatically from the abstract and can be wrong, so check the paper.

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