- Second induction therapy: Beginning immediately after first induction therapy, patients receive cyclophosphamide (CTX) IV over 30 minutes on days 1, 15, and 29; cytarabine (ARA-C) IV over 30 minutes on days 1-4, 8-11, 15-18, and 22-25; and oral mercaptopurine (MP) once daily on days 1-28. Patients with CNS leukemia at presentation also undergo concurrent craniospinal irradiation. Patients without CNS leukemia at presentation receive MTX IT on days 1, 8, 15, and 22. Patients with Ph chromosome-positive status receive oral imatinib mesylate once daily for at least 28 days (days 1-28).