Blinatumomab as a Bridge to Allo-HSCT in HR BCP-ALL

Inclusion Criteria: 1. The patients meet the diagnostic criteria for high risk precursor B-ALL (according to the 2016 WHO classification) and are under hematologic remission. 2. ECOG score is 0-2. 3. Expecting life span is more than 6 months. 4. Patients are free from severe organ dysfunction. Exclusion Criteria: 1. Patients are combined with severe organ dysfunction: Organ failure: Cardiac failure: ejection fraction(EF) \<30%, NYHA standard, cardiac function not Full Grade II or above; Liver and kidney insufficiency: serum total bile Erythroid ≥2mg/dl, AST or ALT≥ upper limit of normal 2.5-fold, serum creatinine (SCr) \>2.5mg/ dL or blood Creatinine clearance rate \< 30ml/min. 2. Patients are combined with infection or other complications that can not tolerate chemotherapy. 3. Patients are suffering from central nervous system/solitary extramedullary leukemia. 4. Patients are considered as tumer progression. 5. Patients has undergone allogeneic hematopoietic stem cell transplantation or underwent autologous stem cell transplantation within 6 weeks or other immunotherapy within 4 weeks. 6. Pregnant and lactating women will not be included.