Cemiplimab, sold under the brand name Libtayo, is a monoclonal antibody medication for the treatment of squamous cell skin cancer. Cemiplimab belongs to a class of drugs that binds to the programmed death receptor-1, blocking the PD-1/PD-L1 pathway.
The most common side effects include fatigue, rash, diarrhea, musculoskeletal pain, and nausea. From Wikipedia