A Study of CNCT19 Treatment in Children and Adolescent r/r ALL Patients(Pediatric)

Key Inclusion Criteria: 1. Signed written informed consent prior to any study procedures (patient and/or parent or legal guardian) 2. Age 3 to 18. Weight ≥10kg 3. Relapsed or refractory acute lymphoblastic leukemia (ALL). 4. Documentation of CD19 tumor expression demonstrated in bone marrow or peripheral blood within 3 months before screening. 5. Bone marrow with ≥ 5% lymphoblasts by morphologic assessment at screening. 6. Karnofsky (age ≥ 16 years) performance status ≥ 70 or Lansky (age \< 16 years) performance status ≥ 50 at screening 7. Organ function requirements: All patients must have adequate renal and liver functions Key Exclusion Criteria: 1. Active Central Nervous System (CNS) involvement by malignancy. 2. Isolated extra-medullary disease relapse. 3. Patients with Burkitt's lymphoma/leukemia, mixed phenotypic acute leukemia and Chronic Myelogenous Leukemia in Blast Crisis 4. History of concomitant genetic syndrome 5. Patients with acute graft-versus-host disease (GVHD) or moderate-to-severe chronic GVHD within 4 weeks before screening. 6. Active systemic autoimmune disease 7. Known infection with human immunodeficiency virus (HIV) or chronic infection with hepatitis B virus (HbsAg positive) or hepatitis C virus (anti-HCV positive). 8. Patients with active infections at screening. 9. Patients who received specified chemotherapy before CNCT19 infusion 10. Radiotherapy before CNCT19 infusion: Non-CNS site of radiation completed \< 4 weeks prior to CNCT19 Infusion; CNS directed radiation completed \< 8 weeks prior to CNCT19 infusion. 11. Donor lymphocyte infusion (DLI) must be stopped \> 6 week prior to CNCT19 infusion. 12. Has had treatment with any prior CAR-T therapy. 13. Life expectancy \< 3 months.