CTLA4 and head and neck squamous cell carcinoma: To this matter, antibodies targeting the Programmed Death 1 (PD-1), such as pembrolizumab and nivolumab, others targeting Programmed Death Ligand 1 (PD-L1), atezolizumab, avelumab as well as the Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) inhibiting antibody ipilimumab have demonstrated their effectiveness in terms of both overall survival (OS) and progression free survival (PFS) in different types of solid tumors among which lung cancer [149], bladder cancer [150], renal cancer [151], head and neck squamous cell carcinoma [152] and melanoma [153] are to be mentioned.