Aim: To evaluate if additional cord blood transfusion could accelerate the hematopoietic reconstitution in severe aplastic anemia(SAA) patients receiving immunosuppressive therapy (IST).

Study design: open-labed, prospective, multicenter, randomized control study Number of subjects: 60 each group

Treatment:

IST group: ATG (Thymoglobuline®, Genzyme) 3.5mg/kg/d×5d plus oral cyclosporine A (CSA) Cord blood transfusion group: In addition to the same dose and course of ATG and CSA , one unit of cord blood having no more than 2 HLA-A, B or DRB1 mismatches is transfused 24h after last dose of ATG administration.

Eligible patients should be under 60 years old with confirmed SAA, without HLA matched siblings and previous ATG treatment history. Patients will be excluded if they present any fatal disease, including respiratory failure, heart failure, liver or kidney function failure et al or severely allergic to biologic products.

To evaluate if additional cord blood transfusion could accelerate the hematopoietic reconstitution in severe aplastic anemia(SAA) patients receiving IST therapy, 120 eligible patients will be randomized to two groups, the IST group and the cord blood transfusion group. Patients in the IST group receive standard IST which including ATG (Thymoglobuline®, Genzyme) 3.5mg/kg/d×5d plus oral cyclosporine A（CSA ) started from 5mg/kg/d and adjusted to maintain trough serum concentration of 200-300ng/ml. While patients in the cord blood transfusion group receive the same dose and course of ATG and CSA as the control group and one unit of cord blood having no more than 2 HLA-A, B and DRB1 mismatches is transfused 24h after last dose of ATG administration.

The neutrophil recovery day is defined as the first day of 3 consecutive days during which the absolute neutrophil count (ANC) is >0.5×109/L, without G-CSF adminstration. Platelet recovery day is defined to have occurred on the first of 7 consecutive days with a blood platelet count (BPC) of >20×109/L, without transfusion support. Response (CR, PR or NR) is evaluated on 3, 4, 6,9, 12, 18 and 24months after treatment.

The primary end point is the neutrophil recovery day and second end points are response rate (CR+PR), treatment related mortality, disease free survival and overall survival.

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Inclusion Criteria:

1．Diagnosis of AA confirmed by bone marrow aspirate and biopsy, myelodysplastic syndrome and paroxysmal nocturnal hemoglobinuria were excluded. To confirm severe AA, the patient must fulfill at least two of the criteria: i) ANC<0.5×109/L,ii)PLT<20×109/L and iii) Ret<20×109/L ,in addition, ANC<0.5×109/L must be included.

2. Under 60 years old, male or female.

3. No HLA matched siblings.

4. No previous ATG treatment history.

5. Performance status score no more than 2 (ECOG criteria).

6．Adequate organ function as defined by the following criteria:ALT, AST and total serum bilirubin <2×ULN (upper limit of normal) Serum creatinine and BUN <1.25×ULN.

7. Adequate cardiac function without acute myocardial infarction, arrhythmia or atrioventricular block, heart failure, active rheumatic heart disease and cardiac dilatation.

8．Signed and dated informed consent document indicating that the patient (or legally acceptable representative) has been informed of all pertinent aspects of the trial prior to enrollment.

9. Willingness and ability to comly with scheduled visits, treatment plans, laboratory tests, and other study procedures.

Exclusion Criteria:

1. Presence of any condition inappropriate for HSCT.
2. Presence of any fatal disease, including respiratory failure, heart failure, liver or kidney function failure et al.

3．Severely allergic to biologic products.

4．Pregnancy or breastfeeding.

5．Current treatment on another clinical trail.

6．Any other condition the investigator judged the patient inappropriate for entry into this study.