The study will be conducted as a single center Phase I/II study to evaluate the safety of administering Plerixafor administered as part of a myeloablative preparative regimen (Institutional Protocol:Fludarabine 50mg/m2/da x 4 days, Busulfan 3.2mg/kg/day x 4 days, TBI 400cGy in divided fractions) for stem cell transplant recipients with AML and to determine whether or not residual leukemic stem cells can be mobilized. Three patients will be enrolled into each of 4 sequential cohorts. Patients in the first cohort will receive 1 dose of Plerixafor (240mcg/kg sc) prior to administration of the first dose of Fludarabine and Busulfan. If tolerated it is planned to escalate the number of Plerixafor doses in the subsequent cohorts to 2. 3. and 4 to be administered before the respective 2nd, 3rd, and 4th dose of chemotherapy.

The study will be conducted as a single center Phase I/II study to evaluate the safety of administering PLERIXAFOR as part of a myeloablative preparative regimen (Institutional Protocol: FBT(400) - FLUDARABINE 50mg/m2/d x 4 days, BUSULFAN 3.2mg/kg/day x 4 days, TBI 400cGy in 2 fractions) for stem cell transplant recipients with Acute Myeloid Leukemia (AML) and to determine whether or not residual leukemic stem cells can be mobilized. Three patients will be enrolled into each of 4 sequential cohorts. Patients in the first cohort will receive 1 dose (240mcg/kg SC) of PLERIXAFOR ( MOZOBIL, formerly known as AMD3100) prior to administration of the first dose of FLUDARABINE and BUSULFAN It is planned to escalate the number of PLERIXAFOR doses in the subsequent cohorts to 2. 3. and 4 to be administered before the respective 2nd, 3rd, and 4th doses of chemotherapy. As primary endpoint the study will establish the toxicity of combined administration of PLERIXAFOR and the preparative regimen at each dose level. Secondary endpoints will include quantification of CXCR4 positive cells and candidates for leukemic disease propagating cells before and after administration of PLERIXAFOR. Mobilized cells will be examined for the ability to undergo apoptosis. Clinical parameters including SAE, OS and LFS are part of the evaluation.

The comparison of cell populations in peripheral blood before and after PLERIXAFOR may facilitate a better definition of minimal residual disease in patients deemed morphologically in a complete remission. The assessment after completion of the preparative regimen will provide a measurement of minimal residual disease prior to the transplant. The assessment of residual leukemic cells with respect to apoptosis will define their responsiveness to the administration of FLUDARABINE and BUSULFAN. The obtained information will facilitate development of a new platform to optimize preparation of patients for a transplant. Eg. Insufficient mobilization of leukemic cells may be addressed in future studies by combining mobilization strategies. Similarly, if cells are shown to be apoptosis resistant one may be able to include apoptosis inducing small molecules.

Inclusion Criteria:

• Patients with AML in remission.
• Availability of a suitably matched related or unrelated donor
• Age 18-60 years
• Eligibility for a myeloablative transplant using the Institutional protocols R-FBT(400)-CSMF as preparative regimen for related donors and U-FBT(400)-CP(30)CS for unrelated donors.
• Eligible subjects who are illiterate will be offered participation in the study

Exclusion criteria:

• Patients aged 61years or older
• Patients not eligible for the preparative regimens R-FBT(400)-CSMF or U-FBT(400)-CP(30)CS
• Pregnant or lactating females
• Creatinine of .>2x normal
• Bilirubin, AST, ALT > 2x normal
• MUGA of <50%

The study will be performed on patients undergoing myeloablative allogeneic stem cell transplants (PBSC or BM) from related or unrelated donors for the treatment of patients with AML in remission.