Tofacitinib is a Janus kinase (JAK) inhibitor primarily used in the treatment of autoimmune conditions, particularly moderate to severe rheumatoid arthritis in adults who have had an inadequate response or intolerance to methotrexate. It works by inhibiting JAK enzymes, which are involved in the immune response and inflammation, thereby reducing joint pain, swelling, and stiffness.

It is also approved for active psoriatic arthritis in adults, helping to manage symptoms and improve physical function in patients with joint pain and swelling associated with psoriasis.

Another key application is in the treatment of moderately to severely active ulcerative colitis in adults who have had an inadequate response to or are intolerant of conventional therapies, aiding in inducing and maintaining remission.

Tofacitinib is additionally approved for active ankylosing spondylitis in adults. It is under investigation for other conditions like alopecia areata.

Overall, tofacitinib provides an important therapeutic option for various autoimmune diseases, offering symptom relief and improved quality of life.