CD274 and head and neck squamous cell carcinoma: Other anti-PD-1 Phase II/III trials currently underway including NCT03813836 (pembrolizumab in recurrent/metastatic HNSCC with WHO performance status 2), NCT02521870 (pembrolizumab plus intratumoral SD-101 in anti-PD-1/PD-L1 treatment-naïve recurrent/metastatic HNSCC), NCT02741570 (nivolumab plus ipilimumab vs. the EXTREME regimen as first-line treatment in recurrent/metastatic HNSCC), NCT03040999 (pembrolizumab plus cisplatin plus RT vs. cisplatin plus RT alone in locally advanced HNC), and NCT02707588 (pembrolizumab plus RT vs. cetuximab plus RT in locally advanced HNC).