PDCD1 and head and neck cancer: A phase I/II study combining lirilumab and nivolumab, a programmed cell death protein 1 (PD-1) checkpoint inhibitor, in patients with head and neck cancer, as well as phase II trials utilizing lirilumab as monotherapy or in combination with PD-1 and CTLA4 inhibitors, have not shown a significant improvement in outcomes with the use of KIR blockade [28,29,30,31].