Safety Study of 5-Azacitidine and Standard Donor Lymphocyte Infusion (DLI) to Treat Acute Myeloid Leukemia (AML) or Myelodysplastic Syndrome (MDS) Relapsing After Allogeneic Stem Cell Transplantation

Inclusion Criteria: \- Primary and secondary MDS, AML after MDS, and de novo AML relapsing after allogeneic stem cell transplantation * Eligibility for Donor Lymphocyte Infusions * Performance status according to the WHO scale: 0, 1 or 2. * Adequate renal and liver function: bilirubin \< 1.5 times the upper limit of normal and a GFR \> 50 ml/min * Absence of severe cardiovascular disease, i.e., arrhythmias requiring chronic treatment, congestive heart failure (NYHA Class III or IV) or symptomatic ischemic heart disease, where New-York Heart Association (NYHA) * HIV negative and HBs-Ag negative. * Absence of active uncontrolled infection (Septicaemia). * No prior history or current evidence of central nervous system and psychiatric disorders requiring hospitalization. * Age at least 18 years. * Negative pregnancy test for women with reproductive potential. * Signed written informed consent must be given according to national/local regulations. Exclusion Criteria: \- Have malignant hepatic tumors. * Severe liver dysfunction CHILD B and C. * Renal insufficiency with a GFR \< 50 ml/min * Radiation therapy, chemotherapy, or cytotoxic therapy, given to treat conditions other than MDS, AML or applied for conditioning prior allogeneic stemcell transplantation. * Psychiatric illness that would prevent granting of informed consent. * Treatment with androgenic hormones during the previous 14 days prior Day 1. * Active viral infection with known human immunodeficiency virus (HIV) or viral Hepatitis B or C. * Hypersensitivity to Mannitol or 5-Azacitidine. * Treatment with other investigational drugs following relapse after allogeneic stemcell transplantation or ongoing adverse events from previous treatment with investigational drugs regardless of time period.