To evaluate the safety and efficacy of Blinatumomab maintenance after allogeneic hematopoietic stem cell transplantation for high-risk acute B-lymphoblastic leukemia.

Blinatumomab is a novel immunological antibody based on BiTE. CD19 is a surface antigen expressed throughout the development of B lymphocytes, making it an ideal target for immunotherapy. Blinatumomab was approved by the FDA for the treatment of adults with relapsed/refractory cancers. Open-label, single-arm, multicenter phase II clinical study (BLAST study) , enrolling 116 adult patients with precursor B-ALL in complete hematologic remission after at least 3 doses of intense chemotherapy but persistently positive for Measurable Residual Disease (MRD) (MRD ≥10-3 ), which is the first ALL international multicenter clinical trial. In August 2022, China's National Medicines and Pharmaceutical Administration (NMPA) Approved Blinatumomab for the treatment of relapsed/refractory precursor B-cell ALL in adults.

Blinatumomab is mostly used for preemptive therapy after post-transplant MRD conversion, and fewer prospective studies have been conducted in the area of maintenance therapy. A prospective single-arm clinical study (NCT02807883) with Blinatumomab as maintenance therapy (up to 4 cycles) after allogeneic transplantation, concluded by MD Anderson in August 2021, had the primary endpoints of safety (acute graft-versus-host disease [aGVHD] and non-relapse mortality [NRM]) and the secondary endpoints of efficacy (PFS, OS, etc.), a total of 23 patients were enrolled in patients who received at least 1 cycle of Blinatumomab, the interval between transplantation and the first cycle of Blinatumomab use was 78 days (44-105), 57% of the patients completed 4 cycles of treatment, the median follow-up was 14.3 months, the 1-year NRM was 0%, the incidence of grade 3-4 aGVHD was 5%, the 1-year OS was 85%, and the 1-year PFS was 71%. There was a trend toward benefit in PFS and OS curves between the two groups. Although this study is an exploratory study, data from applied studies in the post-transplantation maintenance phase suggest that this immunotherapy may be termed as a new, better and safer option.

Therefore, the investigators conducted a multicenter, randomized, controlled study based on retrospective research to further explore and validate the safety and efficacy of Blinatumomab as a maintenance therapy after high-risk B-ALL allogeneic transplantation.

Inclusion Criteria:

1. Age 16-65 years
2. Diagnosis with acute B-lymphoblastic leukemia (B-ALL) expressed CD19
3. High-risk group B-ALL
4. Have suitable hematopoietic stem cell donors
5. No dysfunction of vital organs

Exclusion Criteria:

1. CR/MRD negative before blinatumomab maintenance
2. Active hepatitis B
3. HIV-infected
4. Active infections; acute and chronic GVHD requiring systemic immunosuppressive therapy;
5. severe impairment of vital organ function
6. Those judged by the investigator to be unsuitable for participation in this trial.