In recently published phase II clinical trial studies, combinations of the anti-PD-1 inhibitors pembrolizumab or nivolumab with cetuximab showed an overall response rate range of 23%–45% by 6 months, depending on the number of prior treatments in patients with recurrent or metastatic HNSCC (59–61). Here, PDCD1 is linked to head and neck squamous cell carcinoma.