Upadacitinib hemihydrate is used to treat moderate to severe rheumatoid arthritis (RA) in adults with an inadequate response or intolerance to methotrexate (MTX) or other disease-modifying antirheumatic drugs (DMARDs). It reduces joint pain, swelling, and stiffness, inhibits progression of structural damage, and improves physical function by selectively inhibiting Janus kinase 1 (JAK1), a key enzyme in inflammatory signaling pathways. It is also indicated for active psoriatic arthritis (PsA), active ankylosing spondylitis (AS), moderate to severe atopic dermatitis (AD) in adults and adolescents, moderately to severely active ulcerative colitis (UC), and Crohn's disease (CD) in adults and adolescents aged 12 years and older who have had an inadequate response or intolerance to conventional therapy or biologics. Administered orally as an extended-release tablet, it provides a targeted oral alternative to injectable biologic therapies.