Merck said Keytruda used alone reduced the risk of disease progression or death by 43% compared with chemotherapy in a Phase 3 trial involving patients with mismatch repair deficient advanced or recurrent endometrial cancer.
The randomized, open-label KEYNOTE-C93 study enrolled 299 patients who had not received systemic chemotherapy or whose cancer returned after prior adjuvant therapy. Participants received pembrolizumab, marketed as Keytruda, or carboplatin plus paclitaxel.
After median follow-up of 36.7 months, median progression-free survival was 38.2 months with Keytruda versus 8.4 months with chemotherapy. The difference was statistically significant, with a hazard ratio of 0.57 and p-value of 0.0002.
At three years, 52.8% of Keytruda recipients remained alive without disease progression, compared with 30% receiving chemotherapy.
Overall survival, the trial’s other primary endpoint, showed a favorable trend but no statistically significant improvement. Three-year survival rates were 70.7% and 62%, respectively. Median overall survival had not been reached in either group, and follow-up continues.
Confirmed tumor response rates were 64.1% with Keytruda and 62.1% with chemotherapy. That comparison was not tested for statistical significance at this analysis.
Grade 3 or higher treatment-related adverse events occurred in 18.1% of Keytruda recipients versus 50.7% receiving chemotherapy. Grade 3 or higher immune-mediated adverse events and infusion reactions occurred in 7.4% and 3.5%, respectively. No new safety signals were identified in either treatment group during the trial.
The findings were presented at the European Society for Medical Oncology Congress 2026 and published in The Lancet. Merck said it would share the results with regulators worldwide.
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