KEYNOTE-991 trial evaluating Keytruda + enzalutamide and androgen deprivation therapy for metastatic hormone-sensitive prostate cancer to stop for futility

Merck is discontinuing the study based on the recommendation of an independent Data Monitoring Committee which reviewed data from a planned interim analysis. At the interim analysis, Keytruda in combination with enzalutamide and ADT did not demonstrate an improvement in overall survival (OS) or radiographic progression-free survival (rPFS), the trial’s dual primary endpoints, compared to placebo plus enzalutamide and ADT.

The safety profile of Keytruda in this trial was consistent with that observed in previously reported studies. No new safety signals were identified; however, the combination was associated with a higher incidence of Grade 3-5 adverse events and serious adverse events compared to the control arm. Merck is informing study investigators of the decision and advises patients in the study to speak to their physician regarding treatment. Data from this study will be presented at an upcoming medical meeting.

“There is a significant unmet need for patients with advanced prostate cancer, and the outcome of this study is an important reminder that this disease remains very difficult to treat,” said Dr. Scot Ebbinghaus, vice president, clinical research, Merck Research Laboratories. “We are grateful to the patients and investigators for their participation in this study, and we will continue to advance our clinical development program to evaluate Keytruda-based combinations and novel candidates for patients with prostate cancer.”