SHR2554/AZA + Overlapped Modified BUCY for High-risk/Relapsed Leukemia/MDS

Inclusion Criteria:

1. Age 15-60 years, of either sex.

2. Diagnosis of AML or ALL according to the WHO 2022 criteria, with an indication for allogeneic hematopoietic stem cell transplantation:

   AML with high-risk genetics at diagnosis (risk stratification per ELN 2022) or relapsed/refractory AML (meeting any of the following: refractory-failure to achieve complete remission (CR) after two cycles of induction chemotherapy; relapse-reappearance of blasts in peripheral blood or bone marrow (≥5%) after first CR, or extramedullary relapse (EMR)).

   High-risk B-ALL at diagnosis (risk stratification per ELN 2022) or pre-transplant MRD-positive B-ALL.

   Confirmed T-ALL. History of central nervous system leukemia (CNSL) or pathologically confirmed extramedullary disease (EMD) during AML or ALL.

   Myelodysplastic neoplasms (MDS): IPSS score intermediate-2 or high; IPSS-R score high or very high; IPSS-M score high or very high.

3. Availability of an appropriate HLA-matched donor.4: ECOG performance status 0-2.5: Adequate major organ function, defined as: Left ventricular ejection fraction ≥50%. Pulmonary function: DLCO ≥50% of predicted value. Liver function: ALT/AST ≤3×ULN, total bilirubin ≤2×ULN. Renal function: estimated creatinine clearance (CrCl) ≥60 mL/min.6: Ability to understand the study and voluntary signed informed consent.

Exclusion Criteria:

1: Acute promyelocytic leukemia (APL);2: Active central nervous system leukemia;3: Prior allogeneic hematopoietic stem cell transplantation;4: Prior treatment with any EZH2 inhibitor;5: Uncontrolled active infection as assessed by the investigator;6: Myocardial infarction or unstable angina within the previous 6 months;7: Known hypersensitivity to SHR2554, azacitidine, or any excipient of the mBuCy regimen;8: Pregnant or breastfeeding women;9: Any other medical condition that, in the investigator's judgment, would preclude study enrollment.