Cutaneous squamous cell carcinoma (CSCC) is one of the most common types of cancer in humans, and its prevalence is rising. 

High mutational loads, known lymphocyte infiltration, and programmed death (PD)-ligand 1 (PD-L1) expression suggest that immune checkpoint inhibitors, such as PD-1 inhibitors, may be useful in treating CSCC, as seen in other solid tumor types. Recently, the results of a combined phase I/II clinical trial revealed the robust responsiveness of CSCCs to the PD-1 inhibitor cemiplimab, with an overall response rate of 50% and a durable response lasting more than 6 months in 57% of responders.

Cemiplimab is a breakthrough therapy, the first systemic medicine licensed for advanced CSCCs, as compared to other systemic therapies with limited data on effectiveness and safety. Other immune checkpoint inhibitors have shown potential in case reports and series and are now being tested in clinical trials for CSCCs.