- Induction phase (part 2): Patients receive cyclophosphamide IV over 1 hour on days 36 and 64; cytarabine IV on days 38-41, 45-48, 52-55, and 59-62; oral mercaptopurine on days 36-63; and methotrexate IT on days 45 and 59. Two weeks later, patients proceed to protocol M.