Phase II Study of 5-azacytidine Maintenance After Transplant for AML or MDS

Inclusion Criteria: * Age≥18 with MDS or high-risk AML, morphologically confirmed and based on World Health Organization criteria (see below for definition of high-risk AML)\*, who are transplant candidates with an available human leukocyte antigen (HLA) -matched sibling or unrelated donor with at least 8/8 match \*Definition of high-risk AML: * Age≥60 years * Age\<60 years with any of the following: * Secondary AML * Poor risk cytogenetics, which include abnormalities of chromosome 3, 5, or 7, trisomy 8, 11q23 abnormalities, t(6;9), 20q-, and complex karyotype * Fms-like tyrosine kinase 3 (FLT3) mutation * Disease status ≥ second complete remission (CR2) at time of HCT * Detectable disease at time of HCT * Eastern Cooperative Oncology Group (ECOG) performance status 0-2 * Adequate major organ function, as defined by AST and ALT \< 2 x upper limit of normal, total serum bilirubin \< 2 x upper limit of normal (unless due to hemolysis or Gilbert's syndrome, then no upper limit), creatinine \< 2 x upper limit of normal, unless there is known chronic kidney disease (creatinine must be at baseline for subjects with chronic kidney disease) * In agreement to use an effective barrier method of birth control to avoid pregnancy during the study and for a minimum of 30 days after study treatment, for all male and female patients who are fertile Exclusion Criteria: * Uncontrolled, life-threatening infection that is not responding to antimicrobial therapy * Serum creatinine \> 2 x upper limit of normal, unless there is known chronic kidney disease (creatinine must be at baseline for subjects with chronic kidney disease), aspartate aminotransferase (AST),alanine aminotransferase (ALT), or total bilirubin \> 2x upper limit of normal * History of psychiatric disorder which may compromise compliance with the protocol or which does not allow for appropriate informed consent * Patient may not be receiving any other antineoplastic agents * Pregnancy * Concurrent use of any other investigational agents on a clinical trial * Prior allogeneic stem cell transplant * Known hypersensitivity to 5-azacytidine \* Prior treatment with 5-azacytidine is allowed Post-transplant eligibility and exclusion criteria Patients will have to meet the following post-transplant eligibility criteria to initiate treatment: * In complete response (including complete remission with incomplete blood count recovery and marrow complete response) on bone marrow biopsy for response assessment after HCT (typically day +30) * Patient is within 30-100 days after HCT * Absolute neutrophil count (ANC) ≥ 1000/µL, platelet count ≥ 20,000/µL * ECOG performance status 0-2 * Adequate major organ function, as defined by AST and ALT \< 2 x upper limit of normal, total serum bilirubin \< 2 x upper limit of normal (unless due to hemolysis or Gilbert's syndrome, then no upper limit), creatinine \< 2 x upper limit of normal unless there is known chronic kidney disease (creatinine must be at baseline for subjects with chronic kidney disease) * In agreement to use an effective barrier method of birth control to avoid pregnancy during the study and for a minimum of 30 days after study treatment, for all male and female patients who are fertile Patients may not have any of the following post-transplant exclusion criteria: * Active grade II-IV acute GVHD, for example requiring treatment with steroids at a dose equivalent to prednisone 1mg/kg daily or higher * Uncontrolled, life-threatening infection that is not responding to antimicrobial therapy * Serum creatinine \> 2 x upper limit of normal unless there is known chronic kidney disease (creatinine must be at baseline for subjects with chronic kidney disease), aspartate aminotransferase (AST),alanine aminotransferase (ALT), or total bilirubin \> 2x upper limit of normal * History of psychiatric disorder which may compromise compliance with the protocol or which does not allow for appropriate informed consent * Pregnancy * Concurrent use of any other investigational agents on a clinical trial * Known hypersensitivity to 5-azacytidine \* Prior treatment with 5-azacytidine is allowed