KEYNOTE-055: A phase II trial of single agent pembrolizumab in patients (pts) with recurrent or metastatic head and neck squamous cell carcinoma (HNSCC) who have failed platinum and cetuximab.

TPS3094 Background: Treatment options are limited for pts with recurrent and/or metastatic HNSCC whose disease has progressed after platinum and cetuximab therapy. Pembrolizumab (MK-3475) is a humanized IgG4 monoclonal antibody designed to block interaction between activated T-cell-specific programmed death receptor 1 (PD-1) and its ligands PD-L1 and PD-L2. Preclinical studies have shown that blocking PD-1/PD-L1 interaction promotes infiltration of activated tumor-specific effector T cells, leading to tumor cell death. In KEYNOTE-012, a phase 1b clinical study, pembrolizumab exhibited antitumor activity in patients with recurrent or metastatic, PD-L1–positive HNSCC. Treatment with intravenous pembrolizumab 10 mg/kg every 2 weeks resulted in an objective response rate (ORR) of 19.6% (confirmed and unconfirmed responses) by investigator review, and the magnitude of response was positively correlated with PD-L1 expression in the tumor tissue (P= 0.018). Methods: KEYNOTE-055 (NCT02255097) is a multicenter, op...