Blinatumomab as Maintenance Therapy in Patients With High-risk B-lineage Acute Lymphoblastic Leukemia Post Allogeneic Hematopoietic Cell Transplantation

1．Age ≥ 14 years, male or female; 2．CD19 + acute B lymphoblastic leukemia treated with allogeneic hematopoietic stem cell transplantation [Patients, the types of transplantation include fully matched sibling transplantation, haploidentical related donor transplantation and unrelated donor transplantation; 3．CD19 + acute B-lymphoblastic leukemia at risk of relapse before transplantation [including but not limited to: refractory leukemia: failure to achieve complete remission (CR)/CR with partial hematological recovery (CRh)/CR with incomplete hematological recovery (CRi) or CR/CRh/CRi after the end of induction therapy (generally refers to 4-week regimen or Hyper-CVAD regimen), but still positive for measurable residual disease (MRD); relapsed leukemia: patients who have achieved CR have blasts in peripheral blood or bone marrow (proportion > 5%), or extramedullary disease; onset of white blood cells > 30 × 109/L; patients with poor prognosis cytogenetic abnormalities; patients with positive residual leukemia before transplantation, etc.] 4．The disease is in complete remission, and residual leukemia is negative, absolute neutrophil count ≥ 1.0 × 109/L, platelet count ≥ 50 × 109/L, lasting for more than a week; 5．Freedom from ≥ Grade 3 acute GVHD or uncontrolled moderate to severe chronic GVHD within 30 days prior to enrollment; Awareness and willingness to sign written informed consent.