RAHWAY, New Jersey, United States — October 26, 2026
Merck, known as MSD outside the United States and Canada, announced positive results from the Phase III KEYNOTE-C93 trial evaluating KEYTRUDA® (pembrolizumab) as monotherapy in patients with mismatch repair deficient (dMMR) advanced or recurrent endometrial cancer. The study demonstrated a statistically significant and clinically meaningful improvement in progression-free survival (PFS), reducing the risk of disease progression or death by 43% compared with platinum doublet chemotherapy. Median PFS reached 38.2 months with KEYTRUDA, compared with 8.4 months with chemotherapy, representing more than a fourfold difference. The trial enrolled patients who had not previously received systemic chemotherapy or whose disease had recurred following prior adjuvant therapy. The results were presented during a Presidential Symposium at the European Society for Medical Oncology (ESMO) Congress 2026, selected for an official press briefing and published simultaneously in The Lancet. The findings support further evaluation of pembrolizumab alone as a potential chemotherapy-free treatment option for appropriately selected patients with dMMR advanced or recurrent endometrial cancer.
KEYNOTE-C93 Demonstrates Significant Progression-Free Survival Benefit
KEYNOTE-C93 met its primary progression-free survival endpoint, with a hazard ratio of 0.57 (95% confidence interval: 0.42–0.79; p=0.0002) for KEYTRUDA compared with platinum doublet chemotherapy. After a median follow-up of 36.7 months, the median PFS was 38.2 months for pembrolizumab, compared with 8.4 months for chemotherapy. At 36 months, an estimated 52.8% of patients receiving KEYTRUDA remained progression-free, compared with 30.0% in the chemotherapy group. The study also showed a favorable trend in overall survival, another primary endpoint, although the reported analysis did not establish a statistically significant overall survival benefit. The overall survival hazard ratio was 0.77, with a 95% confidence interval of 0.52–1.15, and follow-up is continuing. The confirmed objective response rate was 64.1% with KEYTRUDA and 62.1% with chemotherapy; these response-rate results were not tested for statistical significance at this analysis. Among responders, the median duration of response had not been reached with pembrolizumab, compared with 10.2 months with chemotherapy. These findings highlight the durability of responses observed in the KEYTRUDA treatment group.
Safety Findings Support Further Evaluation of Pembrolizumab Monotherapy
The safety profile of KEYTRUDA in KEYNOTE-C93 was consistent with previously reported studies, and no new safety signals were identified in either treatment group. Grade 3 or higher treatment-related adverse events occurred in 18.1% of patients receiving pembrolizumab, compared with 50.7% of those receiving platinum doublet chemotherapy. Severe anemia was the most common Grade 3 or higher treatment-related adverse event, reported in 2.0% of patients treated with KEYTRUDA and 18.1% of patients receiving chemotherapy. Grade 3 or higher immune-mediated adverse events and infusion reactions occurred in 7.4% of the pembrolizumab group and 3.5% of the chemotherapy group. As an anti-programmed death receptor-1 (PD-1) therapy, pembrolizumab works by blocking the interaction between PD-1 and its ligands, PD-L1 and PD-L2, helping the immune system recognize and attack cancer cells. However, immune-based treatments can also cause immune-mediated reactions affecting healthy tissues, so appropriate monitoring and clinical management remain important. Merck reported that the trial’s findings provide additional evidence for pembrolizumab monotherapy in this biomarker-defined population, while the ongoing study will continue to assess overall survival and other clinical outcomes.
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Results Expand Merck’s Endometrial Cancer Research Strategy
The KEYNOTE-C93 findings add to Merck’s broader clinical development program investigating KEYTRUDA as monotherapy and in combination regimens for endometrial cancer. In the United States, KEYTRUDA already has approved endometrial cancer indications, including use with carboplatin and paclitaxel for primary advanced or recurrent disease, and use with LENVIMA® (lenvatinib) for certain patients with advanced disease that has progressed following prior systemic therapy. Pembrolizumab monotherapy is also approved for eligible patients with advanced MSI-H or dMMR endometrial carcinoma following disease progression after prior systemic therapy when curative surgery or radiation is not an option. The KEYNOTE-C93 results concern a distinct treatment setting and will be shared with regulatory authorities worldwide; any new indication will depend on regulatory review. Merck is also developing additional approaches for endometrial cancer, including the investigational TROP2-directed antibody-drug conjugate sacituzumab tirumotecan in collaboration with Kelun-Biotech. Other studies are evaluating treatment strategies across different disease stages and biomarker groups. With endometrial cancer incidence and mortality presenting ongoing challenges, the company continues to investigate therapies intended to improve outcomes and broaden treatment options for patients. The clinical significance of the KEYNOTE-C93 results will be further clarified through continued follow-up and regulatory assessment.
Source:Merck, Press release
