Cladribine Dose Escalation in Conditioning Regimen Prior to Allo-HSCT for Refractory Acute Leukemia and Myelodysplastic Syndromes

Inclusion Criteria: * Age 18-70 * ECOG 0 or 1 * Acute leukemia (AML or ALL) without criteria for CR or high risk MDS without criteria for CR * Availability of a donor among following oHLA identical sibling oHaploidentical donor o10/10 or 9/10 allele-level HLA matched unrelated donor * Signed informed consent * Patient affiliated to the national "Social Security" regimen or beneficiary of this regimen Exclusion Criteria: * Contraindication for Allo-HSCT * Cord blood Allo-HSCT * Current active disease or positive serology for HIV, and/or HCV with detectable viremia and/ or HBV with positive Hbs Antigen. * Renal failure with creatinine clearance \< 30 ml/ min * Decompensated haemolytic anaemia * Hypersensitivity to an active substance or to any of the excipients * Acute urinary infection * Pre-existing haemorrhagic cystitis * Woman of childbearing potential not using an effective contraception . * Pregnant or lactating women * Any serious concurrent uncontrolled medical disorder * Any psychological, familial, sociological or geographical condition potentially hampering compliance with the study protocol and follow-up schedule.