Moreover, a phase 1 clinical trial in 15 patients with refractory and metastatic HNSCC indicated that combination therapy with PD-1 inhibitor cemiplimab plus cyclophosphamide, radiation therapy (RT), and granulocyte–macrophage colony-stimulating factor (GM-CSF) could demonstrate acceptable safety profile [143]. The gene discussed is PDCD1; the disease is head and neck squamous cell carcinoma.