Blinatumomab Combined With Low-dose DLI as Maintenance Therapy After Transplantation for B-ALL

Inclusion Criteria: * 1\) Voluntary participation: The participant or legal guardian fully understands this clinical study, provides informed consent (ICF), and is willing/able to comply with all trial procedures. 2\) Age: \<70 years old at screening, any gender. 3) Diagnosis: High-risk acute B-lymphoblastic leukemia (B-ALL) with MRD-negative status post-transplant. High-risk factors include: * \>CR1 status * Pre-transplant MRD+ status * Ph-like subtype * KMT2A rearrangement * Other high-risk cytogenetic/genetic factors per ELN 2023 criteria. 4) Allergy: No history of severe allergies. 5) Liver function: ALT and AST ≤ 2.5 × ULN; Total bilirubin ≤ 2 × ULN. 6) Renal function: Serum creatinine ≤ ULN. 7) Other conditions: Absence of uncontrolled infections or severe psychiatric disorders. 8\) Performance status: ECOG score 0-3, with life expectancy ≥ 4 months. 9) MRD status: Bone marrow flow cytometry confirmed MRD-negative before enrollment. 10\) Engraftment: Evidence of myeloid and platelet engraftment. 11) GVHD: No active graft-versus-host disease (GVHD). Exclusion Criteria: * 1\) Drug hypersensitivity/contraindications: Patients with known allergies or contraindications to the investigational drug(s). 2\) Pregnancy/lactation: Pregnant or breastfeeding female patients. 3) Active infection/GVHD: Patients with active infection or active graft-versus-host disease (GVHD). 4\) Substance abuse: Patients with chronic heavy smoking or alcohol use that may interfere with clinical evaluation. 5\) Impaired consent/compliance: Patients unable to provide informed consent or comply with procedures due to psychiatric/neurological disorders. 6\) Recent major surgery: Patients who underwent major organ surgery within the past 6 weeks. 7\) Organ dysfunction: * Liver: ALT or AST \> 2.5 × ULN; Total bilirubin \> 2 × ULN * Kidney: Serum creatinine \> ULN 8) Investigator judgment: Patients deemed ineligible by investigators (e.g., poor compliance, substance abuse).