DSMB recommended halting the study owing to futility after the first interim analysis in August 2024.

During the past decades, the wider application of easily available haploidentical donor hematopoietic cell transplant (haplo-HCT) has been made possible through the T cell-replete (TCR) regimens including T cell regulation with anti-thymocyte globulin (ATG)/granulocyte colony-stimulating factor (GCSF) and post-transplant cyclophosphamide (PTCy). To achieve decreased non-relapse mortality (NRM) and improved long-term outcomes in haploidentical transplant, the joint use of ATG and PTCy might effectively reduce graft versus host disease (GVHD) and mortality associated with severe forms of GVHD. Recently, investigators established a regimen using low-dose PTCy in conjunction with standard-dose ATG in order to lower the risk of GVHD without compromising engraftment and disease relapse.

Inclusion Criteria:

1. Patients with acute leukemia and/or myelodysplastic syndrome undergoing their first allogeneic hematopoietic stem cell transplantation;
2. Male or female , aged 12-55 years;
3. Haploidentical donor transplantation;
4. ECOG score ≤3; The basic organ function tests met the following standards;

1) Cardiac ejection index >55% 2) Creatinine ≤1.5 times the highest normal value (ULN)

Exclusion Criteria:

1. Severe brain, heart, kidney or liver dysfunction;
2. Refractory malignant state;
3. Patients with other malignant tumors requiring treatment;
4. Clinically uncontrolled severe active infection;
5. The expected survival time was less than 3 months.
6. A history of severe anaphylaxis.
7. Pregnant or lactating women;
8. Any condition considered by the investigators to be unsuitable for enrollment.