Checkpoint Inhibitors in Head and Neck Cancer: Rationale, Clinical Activity, and Potential Biomarkers.

OPINION STATEMENT: The discovery and antibody targeting of immune regulatory molecules such as programmed cell death protein 1 (PD-1) and cytotoxic T lymphocyte antigen 4 (CTLA-4) pathways have led to clinically meaningful anti-cancer results. Rapid advances are being made in a variety of tumor types resulting in regulatory approvals in melanoma, non small cell lung cancer, and renal cell cancer. Numerous ongoing studies are expected to establish the worth of PD-1 pathway inhibitors in other tumor types as well as in combinations with approved agents. Head and neck squamous cell carcinoma (HNSCC) represents a complex group of malignancies characterized by profound immunosuppression and is an excellent candidate for investigation in this exciting field. However, given the fact that a subset of patients will likely benefit, it is critical to focus on biomarker development for appropriate patient selection and facilitation of trial design. As immunotherapy is settling in cancer treatment, immune checkpoint inhibitors are emerging as one of the most promising agents.