Merck announces OS results from final analysis of Phase 3 KEYNOTE-811 trial

Merck announced overall survival results from the final analysis of the Phase 3 KEYNOTE-811 trial evaluating KEYTRUDA, Merck’s anti-PD-1 therapy, in combination with trastuzumab, fluoropyrimidine- and platinum-containing chemotherapy, for the first-line treatment of adults with locally advanced unresectable or metastatic human epidermal growth factor receptor 2-positive gastric or gastroesophageal junction adenocarcinoma. The data are being presented during a proffered paper session at the European Society for Medical Oncology Congress 2024 and also simultaneously published in the New England Journal of Medicine. After a median follow-up of 50.2 months, the KEYTRUDA regimen demonstrated a statistically significant and clinically meaningful improvement in OS in the intention-to-treat HER2-positive advanced gastric or GEJ study population, reducing the risk of death by 20% compared to trastuzumab and chemotherapy alone. For patients who received the KEYTRUDA regimen, median OS was 20.0 months versus 16.8 months for patients receiving trastuzumab plus chemotherapy alone. The KEYTRUDA regimen also demonstrated a clinically meaningful improvement in OS in patients whose tumors expressed PD-L1, reducing the risk of disease progression or death by 21% compared to trastuzumab and chemotherapy alone in these patients. Median OS was 20.1 months for patients with tumors expressing PD-L1 receiving the KEYTRUDA regimen versus 15.7 months for patients receiving trastuzumab and chemotherapy alone. In the study, 85% of patients’ tumors expressed PD-L1. In the U.S., KEYTRUDA, in combination with trastuzumab, fluoropyrimidine- and platinum-containing chemotherapy, is indicated for the first-line treatment of adults with locally advanced unresectable or metastatic HER2-positive gastric or GEJ adenocarcinoma whose tumors express PD-L1 as determined by an FDA-approved test. This indication is approved under accelerated approval based on tumor response rate and durability of response. Continued approval of this indication may be contingent upon verification and description of clinical benefit in the confirmatory trials. Since the FDA’s accelerated approval, the trial has met its dual primary endpoints of progression-free survival and OS. These results have been shared with regulatory authorities worldwide.