The FDA required the safety trial, which also investigated other potential risks, including blood clots in the lungs and death. AdIn the release, the FDA said:“Tofacitinib was first approved in 2012 to treat adults with rheumatoid arthritis (RA) who did not respond well to the medicine methotrexate. In 2017, we approved tofacitinib to treat patients with a second condition that causes joint pain and swelling, psoriatic arthritis (PsA), who did not respond well to methotrexate or other similar medicines. In 2018, we approved the medicine to treat ulcerative colitis, which is a chronic, inflammatory disease affecting the colon. Tofacitinib works by decreasing the activity of the immune system; an overactive immune system contributes to RA, PsA, and ulcerative colitis.