EZN-3042 Administered With Re-induction Chemotherapy in Children With Relapsed Acute Lymphoblastic Leukemia (ALL)

Inclusion Criteria: * Patients must be ≥1 and ≤ 21 years of age when originally diagnosed with acute lymphoblastic leukemia (ALL). * Patients must have relapsed or refractory B-precursor acute lymphoblastic leukemia (ALL) with ≥25% blasts in the bone marrow (M3), with or without extramedullary disease. * Patients may have central nervous system 1, 2 or 3 disease. * Karnofsky Performance Level ≥ 50 for patients \> 10 years of age and Lansky ≥ 50 for patients ≤ 10 years of age. * Patients must have had 2 or more prior therapeutic attempts defined as: * Relapse after going into remission from re-induction for the first or subsequent relapse (ie: 2nd , 3rd, 4th…relapse), or * Refractory disease after first or greater relapse and a single re-induction attempt. \*Please note, Enrollment will be restricted to at most one refractory patient in each cohort of 3 patients per dose level. * Patients with ALL who are refractory to frontline induction therapy are not eligible. * Patients who relapse while receiving standard ALL maintenance chemotherapy will not be required to have a waiting period before entry onto this study. * Patients who relapse when they are not receiving standard ALL maintenance therapy must have fully recovered from grade 3 or 4 toxic effects of all prior chemotherapy, immunotherapy, or radiotherapy prior to entering this study. * Cytotoxic Therapy: It must be at least 14 days since the completion of cytotoxic therapy (excluding hydroxyurea) at the time of s…