Used primarily in the treatment of acute leukemias, particularly acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). It functions as an antimetabolite that interferes with purine synthesis, thereby inhibiting DNA and RNA production in rapidly dividing cancer cells. It is often used as a maintenance therapy following induction chemotherapy. Also investigated for use in autoimmune disorders such as inflammatory bowel disease (IBD), especially in patients intolerant to azathioprine. Its application requires careful monitoring due to potential hepatotoxicity and myelosuppression.