Blinatumomab Prevents Recurrence of R/R ALL After Allo-HSCT

Inclusion Criteria: 1. B-ALL patients with history of relapse, or MRD positive in the last bone marrow examination before allo-HSCT; 2. Age ≥16 years old and ≤ 65 years old when signing informed consent Form (ICF); 3. KPS \> 60 or ECOG 0-2; 4. The expected survival time is more than 3 months; 5. Complete remission (CR) after allo-HSCT with either myeloablative or non-myeloablative conditioning regimen determined by the investigator; 6. Reach the standard of hematopoietic reconstitution (neutrophil count ≥ 0.5×10\^9/L for 3 consecutive days without G-CSF application, platelet count ≥ 20×10\^9/L for 7 consecutive days without platelet transfusion, Hb ≥ 80 g /L without red blood cell transfusion); and neutrophil count ≥ 1.5×10\^9/L, platelet count ≥ 50×10\^9/L within 45 days after transplantation; 7. No central nervous system involvement or clinical symptoms after transplantation; 8. Those who have no serious functional damage to important organs of the body; 9. Fully understand and be informed of this study and sign the ICF; willing to follow and have the ability to complete all test procedures; 10. Females of childbearing age must afford a serum pregnancy test within 7 days before the first dose, and the result should be negative; female participants and their partners should agree to use effective contraception from signing the ICF until 6 months after the last dose. Exclusion Criteria: 1. Serious basic diseases of important organs: such as myocardial infarction, chronic cardiac insufficiency, decompensated hepatic insufficiency, renal function, gastrointestinal insufficiency, etc.; 2. Uncontrolled active infection (including bacterial, fungal, or viral infection), and drug treatment is ineffective; 3. Participating in other clinical studies, or planning to start treatment in this study and less than 4 weeks before the end of treatment in the previous clinical study; 4. Poor graft function (PGF) occurred after allo-HSCT; 5. Combined with other malignant tumors and require treatment; 6. Active GVHD; 7. Have a history of allergy to Chidamide; 8. Pregnant or lactating females; 9. Patients with known history of human immunodeficiency virus (HIV) virus infection and/or acquired immunodeficiency syndrome; 10. Patients with active chronic hepatitis B or active hepatitis C; 11. History of prolonged QT syndrome; 12. Patients considered by other researchers to be unsuitable for this study