Merck provides updates on KEYNOTE-641, KEYNOTE-789 trials

Merck provided updates on two Phase 3 trials, KEYNOTE-641 and KEYNOTE-789. Merck is discontinuing the Phase 3 KEYNOTE-641 trial evaluating KEYTRUDA, Merck’s anti-PD-1 therapy, in combination with enzalutamide and androgen deprivation therapy for the treatment of patients with metastatic castration-resistant prostate cancer based on the recommendation of an independent Data Monitoring Committee. At an interim analysis, KEYTRUDA in combination with enzalutamide and ADT did not demonstrate an improvement in radiographic progression-free survival or overall survival, the trial’s dual primary endpoints, compared to placebo plus enzalutamide and ADT, and crossed a pre-specified futility boundary for OS. Merck is informing study investigators of the decision and advises patients in the study to speak to their physician regarding treatment. Merck also announced that the Phase 3 KEYNOTE-789 trial evaluating KEYTRUDA in combination with pemetrexed plus platinum-based chemotherapy did not meet its dual primary endpoint of OS for the treatment of patients with metastatic nonsquamous non-small cell lung cancer, with epidermal growth factor receptor-genomic tumor mutations, who have previously progressed on a tyrosine kinase inhibitor, including osimertinib. At the final analysis of the study, there was an improvement in OS for patients who received KEYTRUDA plus pemetrexed with platinum-based chemotherapy compared to pemetrexed with platinum-based chemotherapy; however, these results did not meet statistical significance per the pre-specified statistical plan. At an earlier interim analysis, the trial’s other dual primary endpoint, progression-free survival was tested and showed an improvement in the KEYTRUDA arm compared to chemotherapy alone, but these results did not reach statistical significance. In KEYNOTE-641 and KEYNOTE-789, the safety profile of KEYTRUDA was consistent with that observed in previously reported studies and no new safety signals were identified. In KEYNOTE-641, the combination was associated with a higher incidence of Grade 3-5 adverse events and serious adverse events compared to the control arm. Results will be shared at future scientific congresses.