Merck: KEYTRUDA monotherapy lowers progression or death risk 43% in dMMR advanced or recurrent endometrial cancer

Key efficacy results

In KEYNOTE‑C93, pembrolizumab monotherapy reduced the risk of disease progression or death by 43% versus platinum doublet chemotherapy (HR=0.57; 95% CI 0.42–0.79; p=0.0002). After a median follow‑up of 36.7 months median PFS was 38.2 months (95% CI 17.9–NR) with pembrolizumab versus 8.4 months (95% CI 6.8–10.4) with chemotherapy; 36‑month PFS rates were 52.8% versus 30.0%. Overall survival showed a favorable trend (HR=0.77; 95% CI 0.52–1.15; p=0.1000) with median OS not reached in either arm and 36‑month OS rates of 70.7% versus 62.0%.

Response and durability

Confirmed objective response rate was 64.1% with pembrolizumab versus 62.1% with chemotherapy; complete response rates were 33.8% and 26.2%, respectively. Median duration of response was not reached for pembrolizumab versus 10.2 months for chemotherapy; 24‑ and 36‑month DOR rates were 77.0% and 70.7% for pembrolizumab versus 41.3% and 40.0% for chemotherapy.

Safety

The safety profile matched previously reported data with no new signals identified. Grade ≥3 treatment‑related adverse events occurred in 18.1% of patients receiving pembrolizumab versus 50.7% receiving chemotherapy. The most common Grade ≥3 event reported was anemia (2.0% vs 18.1%). Grade ≥3 immune‑mediated adverse events and infusion reactions occurred in 7.4% versus 3.5%.

Trial design and next steps

KEYNOTE‑C93 randomized 299 patients with dMMR advanced or recurrent endometrial cancer who were chemo‑naive or recurred after adjuvant therapy to pembrolizumab 400 mg IV every six weeks (up to 18 cycles) or carboplatin plus paclitaxel. Results were presented at ESMO 2026 and published in The Lancet. The trial continues with ongoing OS follow‑up and results will be shared with regulatory authorities.