Conditioning Regimen Containing Low Dose ATG for The Treatment of Acquired SAA Receiving sUCBT

Inclusion Criteria:

• Patients diagnosed with severe aplastic anemia who do not respond to initial diagnosisor immunosuppressive therapy;
• Patients meet diagnostic criteria for severe aplastic anemia (Camitta criteria);
• Age from 1 to 50 years old, male or female;
• Patients without HLA-matched sibling or unrelated donors avaliable;
• Patients who have undergone unrelated cord blood transplantation need to have HLAhigh-resolution matching、TNC (before cord blood freezing)≥3.0×107/kg、CD34+(before cordblood freezing)≥1.5×107/kg、tubule recovery rate≥80%;
• patients and their family members or guardians agreed to the study and signed informedconsent;
• No severe organ failure;
• ECOG score≤2 and HCT-CI≤2;
• serum ferritin (SF)<1000ug/L;
• women of reproductive agemust have a negative pregnancy test and agree to useeffective contraception during treatment and for one year thereafter.

Exclusion Criteria:

• patients with inherited bone marrow failure syndromes;
• Positive for HLA-A, B, Cw, DRB1, DQB1, DPB1 site-specific HLA antibodies for donorcord blood with solid-phase fluorescence assay;
• patients who have previously received allogeneic hematopoietic stem celltransplantation or solid organ transplantation;
• Uncontrolled bacterial, viral, or fungal infections;
• HIV infection or active viral hepatitis B or C infection;
• Pregnant or breastfeeding women;
• patients with a history of primary malignancy within 3 years prior to transplanttreatment;
• patients receiving ATG treatment within 2 weeks before transplantation;
• patients with drug dependent or uncontrolled mental illness or cognitive impairment;
• Participants in other similar clinical studies within 3 months;
• Patients allergic to ATG;
• patients considered unsuitable for inclusion by the researchers.