Used primarily in the treatment of acute lymphoblastic leukemia (ALL) and other forms of leukemia, especially in children. It works by inhibiting the synthesis of purines, which are essential for DNA and RNA production, thereby preventing the growth of cancer cells. Also used in the management of inflammatory bowel diseases such as Crohn’s disease and ulcerative colitis, and autoimmune conditions like rheumatoid arthritis, where it acts as an immunosuppressant to reduce inflammation and maintain remission. Administered orally or intravenously, it is often part of long-term maintenance therapy due to its ability to sustain disease control. Requires careful monitoring due to potential side effects like bone marrow suppression and liver toxicity.