Multi-center Single Arm Phase II Study of Myeloablative Allogeneic Stem Cell Transplantation for Non-remission Acute Myeloblastic Leukemia (AML) Using Clofarabine and Busulfan x 4 (CloBu4) Regimen

Inclusion Criteria:

Disease Criteria

- AML not in remission at the time of transplant

- "Not in remission" is defined as "greater than 5.0% bone marrow blasts by
aspirate morphology," as determined by a bone marrow aspirate obtained within 2
weeks of study registration.

- For primary induction failure patients: Patients must have failed at least 2
induction regimens.

- For patients with relapsed disease: Patients who relapse more than 6 months
after preceding remission must fail at least one reinduction regimen to be
eligible. For patients in whom the preceding remission is equal to or shorter
than 6 months duration, no re-induction regimen is required to qualify for this
protocol.

- If the pre-transplant bone marrow aspirate and biopsy are hypoplastic (less than 10%
cellularity), and blast percentages cannot be determined, the patient is eligible if
the preceding bone marrow met the above criteria.

- Patients with peripheral circulating blasts or patients with extramedullary leukemia
are eligible if bone marrow aspirate and biopsy meets the above criteria. Age and
Organ Function Criteria

- Age: 2 to 65 years in age.

- Cardiac: LVEF ≥ 40% by MUGA (Multi Gated Acquisition) scan or echocardiogram.

- Pulmonary: FEV1 and FVC capacity) ≥ 40% predicted, DLCO (corrected for hemoglobin) ≥
40% of predicted.

- Children who are unable to cooperate for pulmonary function tests (PFTs), must have
no evidence of dyspnea at rest, no exercise intolerance, and not require supplemental
oxygen therapy.

- Renal: Age equal to or older than 12: The estimated creatinine clearance (CrCl) must
be equal or greater than 60 mL/min/1.73 m2 as calculated by the Cockcroft-Gault
Formula. Age younger than 12: Either estimated or measured CrCl should be greater
than 90 ml/min/1.73m2. For estimation, Schwartz formula will be used.

- Hepatic: Serum bilirubin ≤ 1.5 x upper limit of normal (ULN); (AST)/ ALT ≤ 2.5 x
ULN; Alkaline phosphatase ≤ 2.5 x ULN

- Performance status: Karnofsky ≥ 70%., or Lansky≥70% Consent: All patients must sign
informed consent

Exclusion Criteria:

- Active life-threatening cancer requiring treatment other than AML

- Non-compliant to medications.

- No appropriate caregivers identified.

- HIV1 (Human Immunodeficiency Virus-1) or HIV2 positive

- Active life-threatening cancer requiring treatment other than AML

- Uncontrolled medical or psychiatric disorders.

- Uncontrolled infections, defined as positive blood cultures within 72 hours of study
entry, or evidence of progressive infection

- Active central nervous system (CNS) leukemia

- Preceding allogeneic HSCT

- Receiving intensive chemotherapy within 21 days of registration.

- Patients with preceding primary myelofibrosis

- Peripheral blasts > 10,000/μL at the time of registration