By Colin Kellaher

Merck & Co. on Thursday said a pivotal Phase 3 study of its blockbuster cancer drug Keytruda met a second primary endpoint of event-free survival in patients with high-risk early-stage triple-negative breast cancer.

The Kenilworth, N.J., drugmaker said Keytruda in combination with chemotherapy before surgery and continuing as a single agent after surgery showed statistically significant improvement in event-free survival versus pre-operative chemotherapy.

Merck, which previously reported that the study had met its other dual primary endpoint of pathological complete response, said Keytruda is the first anti-PD-1 therapy to show a statistically significant improvement in event-free survival as a neoadjuvant and adjuvant therapy for patients with triple-negative breast cancer, an aggressive cancer that characteristically has a high recurrence rate within the first five years after diagnosis.

The U.S. Food and Drug Administration in March turned away Merck's application for expanded approval of Keytruda for patients with high-risk early-stage triple-negative breast cancer based on the pCR data and early interim event-free survival findings. The agency was following advice from an advisory committee that recommended a regulatory decision on the indication should be deferred until further data were available from the study.

Write to Colin Kellaher at colin.kellaher@wsj.com

(END) Dow Jones Newswires

05-13-21 0727ET