 - Patients with a prior seizure disorder requiring anti-convulsant therapy are not eligible to receive nelarabine; in addition, patients with pre-existing grade 2 or greater peripheral neurotoxicity, as determined prior to Induction treatment by the treating physician or a neurologist, are not eligible to receive nelarabine; these restrictions in eligibility are designed to prevent excessive nelarabine-induced central and peripheral neurotoxicity in at-risk patients; for the purposes of this study, this includes any patient that has received anticonvulsant therapy to preventtreat seizures in the prior two years 