This study aims to evaluate whether maintenance therapy with decitabine, venetoclax and blinatumomab could improve the 2-year progression free survival (PFS) of patients with philadelphia chromosome-negative B-cell acute lymphoblastic leukemia who had recently received an allogeneic stem cell transplant and in measurable residual disease-negative remission.

This is a phase Ⅱ, open-label, single-arm, multi-center study in patients with philadelphia chromosome-negative B-cell acute lymphoblastic leukemia who had recently received an allogeneic stem cell transplant and in minimal residual disease-negative remission. In this study, patients will be treated with 4 cycles of maintence therapies for up to one year (or until intolerable toxicity, death, withdrawal, or study termination). In cycle one and three, patients will receive decitabine monotherapy, and in cycle two and four, patients will receive a combination of venetoclax and blinatumomab. This study aims to evaluate whether maintenance therapy with decitabine, venetoclax and blinatumomab could improve the 2-year progression free survival (PFS) of those patients, and explore the efficiency and safety.

Inclusion Criteria:

• 1.Philadelphia chromosome-negative B-cell acute lymphoblastic leukemia who underwent an alloHSCT as follows:

  1. patients in CR1 with high-risk features,including adverse clinical features, cytogenetic or molecular alterations according to NCCN 2023.V3.
  2. patients lack of achievement of complete remission after standard induction chemotherapy.
  3. patients with detectable minimal residual disease pre-transplantation.
  4. patients in second and higher CR pre-transplantation. 2.Negative minimal residual disease prior to enrollment (FCM-MRD <0.01% and fusion gene negative).

  3.≥3 months post-transplantation. 4.hematopoietic reconstitution, i.e., ANC ≥0.5 x 109/L, and platelets >20 x 109/L.

  5.Eastern Cooperative Oncology Group (ECOG) score: 0-2. 6.Total serum bilirubin ≤ 3 x upper limit of normal (ULN), alanine aminotransferase (ALT) ≤ 5 x ULN, aspartate aminotransferase (AST) ≤ 5 x ULN.

  7.Creatinine clearance ≥ 30 mL/min. 8.Provide informed consent.

Exclusion Criteria:

• 1.Patients with another malignant disease. 2.Patients with uncontrolled active infection. 3.Patients with left ventricular ejection fraction < 0.5 by echocardiography or grade III/IV cardiovascular dysfunction according to the New York Heart Association Classification.

  4.Detectable minimal residual disease post-transplantation 5.Active GVHD requiring systemic steroid therapy. 6.Patients with uncontrolled active bleeding. 7.Pregnant and lactating women; patients of childbearing potential should be willing to practice methods of contraception throughout the study period.

  8.Patients with other commodities that the investigators considered not suitable for the enrollment.