Inclusion Criteria:

- Patients must be ≥1 and ≤ 21 years of age when originally diagnosed with acute
lymphoblastic leukemia (ALL).

- Patients must have a diagnosis of second or greater relapse 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 ≥ 50 for patients > 10 years of age and Lansky ≥ 50 for patients ≤ 10 years
of age.

- 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 study enrollment.

- Hematopoietic Stem Cell Transplant (HSCT): Patients who have experienced their
relapse after a HSCT are eligible, provided they have no evidence of active
Graft-versus-Host Disease (GVHD) and are at least 120 days post-transplant at the
time of enrollment.

- Prior anthracycline exposure: Patients must have ≤ 400 mg/m2 lifetime exposure of
anthracycline chemotherapy.

- Biologic (anti-neoplastic) therapy: It must be at least 7 days since the completion
of therapy with a biologic agent at the time of study enrollment. For agents that
have known adverse events occurring 7 days after administration, this period must be
extended beyond the time during which adverse events are known to occur.

- Patients must have a calculated creatinine clearance or radioisotope GRF ≥
70mL/min/1.73m2 OR a normal serum creatinine based on the institutional normal values
according to age.

- Patient's ALT must be < 5 x institutional upper limit of norm (ULN), unless the
elevation is suspected to be disease-related.

- Patient's total bilirubin must be ≤ 1.5 x ULN.

- Patient's serum albumin must be ≥ 2 g/dL.

- Patient must have prothrombin time (PT), partial thromboplastin time (PTT) and
international normalized ratio (INR) ≤ 1.5 times the ULN.

- Patient must have a shortening fraction ≥ 27% by echocardiogram or an ejection
fraction ≥ 45% by gated nucleotide study.

- Female patients of childbearing potential must have a negative urine or serum
pregnancy test confirmed prior to enrollment.

- Female patients with infants must agree not to breastfeed their infants while on this
study.

- Male and female patients of child-bearing potential must agree to use an effective
method of contraception approved by the investigator during the study.

Exclusion Criteria:

- Patients with Down syndrome are excluded.

- Patients with B-cell ALL (L3 morphology or evidence of myc translocation by molecular
or cytogenetic technique) are not eligible

- Patients with documented active and uncontrolled infection at the time of study entry
are not eligible.

- Patient will be excluded if they are currently receiving other investigational drugs.

- Patients will be excluded if they are taking strong CYP3A4 inducers or inhibitors.

- Patients will be excluded if there is a plan to administer non-protocol chemotherapy,
radiation therapy, or immunotherapy during the study period.

- Patients will be excluded if they have significant concurrent disease, illness,
psychiatric disorder or social issue that would compromise patient safety or
compliance, interfere with consent, study participation, follow up, or interpretation
of study results.