Azacytidine and Lymphocytes in Relapse of AML or MDS After Allogeneic Stem Cell Transplantation.

Inclusion Criteria:

1. Patients:

   * Age ≥ 18 years
   * Be able to understand and sign informed consent
   * Fertile patients must use a reliable contraception method
2. Disease status at transplantation:

   * AML in first or subsequent complete remission (\< 5% marrow blasts)
   * MDS with less than 10% marrow blasts at the time of transplantation
3. Transplantation:

   * Allogeneic transplantation using a sibling or unrelated donor with matching in 10/10 alleles (HLA-A, B, C, DRB1, DQB1) or maximum of one allele or one antigen or 1 antigen + 1 allele or 1 antigen + 1 DQB1 antigen or 2 alleles mismatches.
   * Myeloablative or reduced-intensity conditioning
   * Second transplantation is allowed
   * Donor is willing to donate lymphocytes
4. Clinical situation:

   * Cytological relapse after allo-SCT defined as the recurrence of more than 5% blasts on bone marrow aspiration (AML) or evidence of MDS
   * Immunophenotypic relapse defined as the recurrence of an abnormal phenotype on flow cytometry in bone marrow aspirate (only in case of a specific phenotype).
   * Cytogenetic or molecular relapse defined as the persistence or recurrence of a cytogenetic abnormality or molecular marker in bone marrow aspiration or peripheral blood. WT1 expression is not considered as reliable marker for relapse in this protocol but FLT3-ITD, NPM1, CEBPA, or translocation-specific markers (such as MLL-PTD, AML-ETO, CBFB-MYH11) are.
5. Immunosuppressive therapy should have been stopped before inclusion.

Exclusion Criteria:

* More than 30% marrow blasts at the time of inclusion
* Extramedullary relapse including CNS involvement
* ECOG Performance status \> 2
* Active acute grade II-IV GvHD at the time of inclusion
* Active chronic GvHD requiring systemic therapy at the time of inclusion
* Uncontrolled infection
* HIV positive
* Acute or chronic heart failure (NYHA class III or IV) or symptomatic ischemic heart disease or ejection fraction \< 35% or uncontrolled arrhythmia
* Severe liver failure (total bilirubin \> 3 mg/dL, SGPT \> 4 X upper normal limit)
* Severe pulmonary failure (corrected DLCo \< 35%)
* Terminal renal failure requiring dialysis
* Severe neurological or psychiatric disorders
* Concurrent investigational drug.
* Other treatment for relapse, except for hydroxyurea but it should be stopped before inclusion in the study.
* Female who is pregnant or breastfeeding