Additionally, there is another group of systemically effective therapeutic agents and immune checkpoint inhibitors (ICIs) for therapeutics that specifically attack molecular structures that result from mutations in the tumors; this includes programed cell death protein 1 (PD-1) inhibitors, which have redefined the treatment paradigm of various types of advanced cancers, including patients with recurrent/metastatic HNSCC [29] in the last few years. The gene discussed is PDCD1; the disease is head and neck squamous cell carcinoma.