Ustekinumab (INN, experimental name CNTO 1275, proprietary commercial name Stelara, Centocor) is a human monoclonal antibody. It is directed against Interleukin 12 and interleukin 23, naturally occurring proteins that regulate the immune system and immune-mediated inflammatory disorders. Since 2009, Ustekinumab is approved in Canada, Europe and the United States to treat moderate to severe plaque psoriasis. On September 24, 2013, the FDA approved the use of ustekinumab for the treatment of psoriatic arthritis.