KENILWORTH, N.J.–(BUSINESS WIRE)–Merck (NYSE:MRK), known as MSD outside the United States and Canada, announced today that the pivotal Phase 3 KEYNOTE-048 trial investigating KEYTRUDA® (pembrolizumab), Merck’s anti-PD-1 therapy, for first-line treatment of recurrent or metastatic head and neck squamous cell carcinoma (HNSCC), met a primary endpoint of overall survival (OS) as monotherapy in patients whose tumors expressed PD-L1 (Combined Positive Score (CPS) ≥20). Based on an interim analysis conducted by the independent Data Monitoring Committee (DMC), treatment with KEYTRUDA monotherapy in these patients resulted in significantly longer OS compared to cetuximab in combination with platinum chemotherapy (cisplatin or carboplatin) plus 5-Fluorouracil (5-FU), the current standard of care for HNSCC in the first-line treatment setting. At the time of the interim analysis, the dual-primary endpoint of progression-free-survival (PFS) for patients whose tumors expressed PD-L1 (CPS≥20) had not been reached. The safety profile of KEYTRUDA in this trial was consistent with that observed in previously reported studies involving patients with HNSCC. These results will be presented at an upcoming medical meeting and submitted to regulatory authorities worldwide.