Controlled Study of Post-transplant Azacitidine for Prevention of Acute Myelogenous Leukemia and Myelodysplastic Syndrome Relapse (VZ-AML-PI-0129)

Inclusion Criteria:

1. Patients with a diagnosis of AML (World Health Organization classification: \>=20% blasts in the bone marrow and / or peripheral blood) or MDS (International Prognostic Scoring System intermediate-1 or higher) that at the time of allogeneic transplantation were in: - Induction Failure, relapsed disease or second or greater remission; patients in first complete remission that required more than 1 cycle of treatment to achieve the remission, or that have AML evolving from MDS, or that had the following abnormalities: FLT3 mutation, deletion of chromosome 5 or 7, MLL gene rearrangement, or more than or equal to 3 cytogenetics abnormalities. Patients with de novo or therapy-related MDS, CMML, or AML are also eligible, regardless of cytogenetics or molecular rearrangements.
2. Biphenotypic Leukemia that at the time of allogeneic transplantation was in induction failure, relapsed disease, first, second or greater remission.
3. Patients must be in complete remission post transplant.
4. Patient may be enrolled 40 to 100 days after transplant.
5. Age 18 to 75 years old.
6. Serum creatinine \< 1.8 mg/dL or creatinine clearance greater or equal than 40 cc/min as defined by the Cockcroft-Gault Equation\*. a. Males(mL/min):(140-age)\*IBW(kg) / 72\*(serum creatinine(mg/dl)) b. Females(mL/min):0.85\*(140-age)\*IBW(kg) / 72\*(serum creatinine(mg/dl)).
7. Serum direct bilirubin \< 1.5 mg/dL (unless Gilbert's syndrome).
8. SGPT \</= 200 IU/ml unless related to patient's malignancy.
9. Be able to understand and sign informed consent.

Exclusion Criteria:

1. Active uncontrolled infection.
2. Presence of uncontrolled graft-versus-host disease.
3. Patients that underwent allogeneic transplantation as a treatment of graft failure.
4. Pregnancy or breast-feeding (women of childbearing potential, any female who has experienced menarche and who has not undergone surgical sterilization or is not post-menopausal with a positive serum pregnancy test.
5. Known or suspected hypersensitivity to azacitidine or mannitol.
6. Patients with advanced malignant hepatic tumors.