Used primarily in the treatment of acute lymphoblastic leukemia (ALL) and other forms of leukemia, especially in children. It functions as an immunosuppressive and antineoplastic agent by interfering with DNA and RNA synthesis, thereby inhibiting rapidly dividing cancer cells. Commonly used as a maintenance therapy to prevent relapse after remission is achieved. Also prescribed for autoimmune conditions such as inflammatory bowel disease (IBD), including Crohn’s disease and ulcerative colitis, when conventional therapies fail. Administered orally, it requires careful monitoring due to potential hepatotoxicity and myelosuppression. Its effectiveness can be influenced by individual metabolic variations, particularly related to thiopurine methyltransferase (TPMT) enzyme activity, which guides dosing to minimize adverse effects.