Safety and Efficiency of Anti-CD19/CD22 Tandem Fully Human Chimeric Antigen Receptor (CAR)-Transduced T-cell Therapy for Pediatric and Young Adult Patients With Relapsed/Refractory B-cell Acute Lymphoblastic Leukemia: a Single Centre, Non-randomised, Open Label Phase I-II Clinical Trial of Automatically Produced Cell Therapy Product MB-CAR-T19-22 Using CliniMACS Prodigy

The treatment plan will be based on stratification by the initial leukemia burden. Patients with "low disease burden" will receive a lymphodepletion chemotherapy of fludarabine (total dose 120mg/m2) and cyclophosphamide (total dose 750mg/m2) over 5 days. Patients will "high disease burden" will receive a lymphodepletion chemotherapy of fludarabine (total dose 120 mg/m2), cyclophosphamide (total dose 750 mg/m2), cytarabine (total dose 900 mg/m2), etoposide (total dose 450 mg/m2), dexamethasone (total dose 30 mg/m2) over 5 days. Based on interim analysis the following dosing approach will be implemented starting April 2021: Cohort 1: CD19+ disease, low and high burden: 1st dose - 150k/kg, 2nd dose - 850k/kg Cohort 2: CD19- disease, low and high burden: 1st dose - 500k/kg, 2nd dose - 500k/kg Cohort 3: HSCT+CAR-T: 100k/kg