Bavencio (avelumab) is a monoclonal antibody used to treat Merkel cell carcinoma, a type of skin cancer, in adults and children aged 12 and older when it has spread (metastatic). It also treats bladder or urinary tract cancer that has spread or cannot be removed with surgery, after platinum treatments have failed. Additionally, Bavencio is used alone or with axitinib to treat advanced kidney cancer. It works by modifying the immune system to target and attack cancer cells.