Inclusion Criteria:  Age 4 months - 18 years old Diagnosis: acute lymphoblastic leukemia, acute myeloid leukemia, juvenile myelomonocytic leukemia, myelodysplastic syndrome, chronic myeloid leukemia Signed by legal representatives informed consent High risk disease ( for ALL - initial hyperleukocytosis> 50x109 / L, T-cell ALL, hypodiploid karyotype, complex karyotype, MLL gene rearrangement, SIL-TAL deletion, primary resistent of the disease, early/very earle relapse, infant ALL; for AML patients - rearrangement of the MLL gene (except for t (1; 11) and t (9; 11) with M5 morphology), inv (3), t (3; 3), complex karyotype anomalies, t (8; 21 ) with trisomy 4, t (16; 21), monosomy 7, monosomy 5, M7 without t (1; 22), FLT3+, M6, t (7; 12), AML with multilineage dysplasia, p53 gene mutations, NUP98 translocations, primary resistent of the disease, early/very earle relapse infant AML, secondary AML; all juvenile myelomonocytic leukemia and myelodysplastic syndrome; allo-HSCT at 3 or more remission; persistence MRD before alloHSCT; allo-HSCT out of remission; persistence MRD after alloHSCT; cytogenetic relapse after alloHSCT ) Donor chimerism=>95% No poor graft function (haemoglobin concentration < 100 g/L; neutrophils < 1.0 × 10E + 9/L; and platelets < 30 × 10E + 9/L on day ≥ 30 post transplant with complete donor chimerism and no graft-versus-host disease or relapse ) ECOG 0-2 status Karnofsky/Lansky status >30%  Exclusion Criteria:  Uncontrolled bacterial or fungal infection at the time of enrollment Severe organ failure: creatinine more than 2 norms; ALT, AST more than 5 norms; bilirubin more than 1.5 norms Ejection fraction less than 50% Requirement for vasopressor support at the time of enrollment Somatic or psychiatric disorder making the patient unable to sign an informed consent Acute GVHD grade 3-4 in patient medical history Severe chronic GVHD in patient medical history