an antimetabolite C5H4N4S that interferes especially with the metabolism of purine bases and the biosynthesis of nucleic acids and that is sometimes useful in the treatment of acute leukemia.
Standard risk (SR) patients (12%) received a 3-drug induction therapy, intrathecal methotrexate (IT-MTX), and continuation therapy with oral 6-mercaptopurine, weekly intramuscular MTX, and monthlypulses with vincristine and prednisone.