Merck’s Phase 3 KEYNOTE-C93 Trial Meets Primary Endpoint Of Progression-Free Survival, Reducing Risk Of Progression Or Death By 43% With KEYTRUDA Monotherapy vs. Platinum Doublet Chemotherapy In dMMR Advanced Or Recurrent Endometrial Cancer

KEYNOTE-C93 showed median progression-free survival (PFS) was more than four times longer for these patients treated with KEYTRUDA as monotherapy (38.2 months) compared to platinum doublet chemotherapy (8.4 months)

KEYNOTE-C93 is the first Phase 3 trial of a PD-1 inhibitor to show a statistically significant and clinically meaningful improvement in PFS as monotherapy compared to chemotherapy in these patients

Late-breaking results were selected for an official press briefing and will be presented during a Presidential Symposium session at the European Society for Medical Oncology (ESMO) Congress 2026 and published simultaneously in The Lancet

Merck (NYSE:MRK), known as MSD outside of the United States and Canada, today announced the first presentation of results from the Phase 3 KEYNOTE‑C93 trial, evaluating KEYTRUDA® (pembrolizumab), Merck’s anti-PD-1 therapy, as monotherapy for the treatment of patients with mismatch repair deficient (dMMR) advanced or recurrent endometrial cancer who had not previously received systemic chemotherapy or who experienced recurrence after receiving prior adjuvant therapy. Results showed KEYTRUDA as monotherapy demonstrated a statistically significant and clinically meaningful improvement in the primary endpoint of progression-free survival (PFS) for these patients, reducing the risk of disease progression or death by 43% (HR=0.57; [95% CI, 0.42-0.79]; p=0.0002) compared to platinum doublet chemotherapy. These late-breaking results will be presented today during a Presidential Symposium at the European Society for Medical Oncology (ESMO) Congress 2026 [Presentation #LBA12], were selected for an official ESMO press briefing and were published simultaneously in The Lancet.

After a median follow-up of 36.7 months (range, 28.4-50.0), median PFS was 38.2 months (95% CI, 17.9-NR) for KEYTRUDA versus 8.4 months (95% CI, 6.8-10.4) for chemotherapy, with 36-month PFS rates of 52.8% (95% CI, 44.2-60.7) versus 30.0% (95% CI, 22.4-37.9), respectively. In addition to an improvement in PFS, a favorable trend in overall survival (OS), the trial’s other primary endpoint, was observed for KEYTRUDA monotherapy versus platinum doublet chemotherapy (HR=0.77 [95% CI, 0.52-1.15]; p=0.1000). Median OS was not reached (NR) (95% CI, NR-NR) for KEYTRUDA versus NR (95% CI, 38.9-NR) for chemotherapy, with 36-month OS rates of 70.7% (95% CI, 62.4-77.5) versus 62.0% (95% CI, 53.1-69.8), respectively. The trial is continuing, and follow-up of OS is ongoing. Results will be shared with regulatory authorities worldwide.