Eligibility Criteria:
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