After the first 4 courses, you will receive 1 course of nelarabine and pegaspargase. Nelarabine will be given by vein over 2 hours once a day for 5 days. Pegaspargase will be given by vein over 2 hours on day 5. After about 21-35 days, you will continue with Course 5 (Hyper-CVAD). After Course 5, you will receive a second course of nelarabine and pegaspargase at the same dose and schedule as before. Once this course is complete, you will continue with Course 6 (methotrexate and cytarabine).