Used primarily in the treatment of acute lymphocytic leukemia, it functions as an antimetabolite to inhibit the synthesis of purines, thereby slowing the growth of cancer cells. It is also applied in managing inflammatory bowel diseases like Crohn's disease and ulcerative colitis, where it helps to modulate the immune system and reduce inflammation. Additionally, it is employed in organ transplant patients to prevent rejection by suppressing the immune response. Its therapeutic use requires careful monitoring due to potential side effects, including bone marrow suppression and liver toxicity.