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.