Anti-CD19 CAR-Engineered NK Cells in the Treatment of Relapsed/Refractory Acute Lymphoblastic Leukemia

Inclusion Criteria: * Age ≥12 years in the single-dose exploration phase, age ≥3 years in the dose exploration phase, both sexes; * Meet the diagnostic criteria for recurrent or refractory CD19 positive acute lymphoblastic leukemia. * The main organs have good organ function. * The estimated survival time is ≥12 weeks. * Blood pregnancy tests for women of childbearing age are negative. * The patient himself/herself , and/or his/her legal guardian, agree to participate in the trial and sign the informed consent form. Exclusion Criteria: * Central nervous system involvement； * Simple extramedullary leukemia or simple extramedullary recurrence； * Received hematopoietic stem cell transplantation within the last 3 months and had graft-versus-host disease (GVHD) in the last 2 weeks, requiring immunosuppressive agents； * Treated with high-dose corticosteroids in the last 1 week； * Allogeneic cell therapy, major surgery, and live or attenuated vaccine had been received within 4 weeks prior to CAR NK-CD19 infusion； * Had received other antitumor therapy or had an uncontrolled infection within 2 weeks prior to CAR NK-CD19 infusion； * Systemic steroids were used within 3 days before CAR NK-CD19 infusion； * Toxicity caused by previous treatment do not fully recover or do not stabilize to grade 1； * Concomitant autoimmune diseases, central nervous system diseases, other active malignancies, infectious diseases, severe cardiovascular diseases, etc； * Known allergies to study drugs or drugs that may be used in the study； * Other conditions determined by Investigator which are not suitable for participation in the study