Upadacitinib is a selective JAK1 inhibitor used to treat moderate to severe rheumatoid arthritis in adults with inadequate response to methotrexate or other disease-modifying antirheumatic drugs. It is also approved for active psoriatic arthritis, ankylosing spondylitis, moderate to severe atopic dermatitis, ulcerative colitis, and Crohn's disease in adults who have not responded well to conventional therapies or biologics such as TNF inhibitors.

It works by inhibiting JAK1, a key enzyme in inflammatory signaling pathways, thereby reducing inflammation. Administered orally as tablets, it helps alleviate joint pain, swelling, and stiffness, improves skin symptoms in atopic dermatitis, and can slow disease progression and joint damage. This medication offers a convenient alternative to injectables and is often prescribed when other treatments are ineffective.