JY509 Universal NK Cell Injection for the Treatment of Relapsed/Refractory Pediatric B-ALL

Inclusion Criteria: * Clinically diagnosed as relapsed or refractory B-cell acute lymphoblastic leukemia (B-ALL), and meeting any of the following criteria:①The patient fails to achieve bone marrow complete remission (MRD \> 1%) after at least 2 courses of standard induction chemotherapy; or those with pre-treatment specific molecular markers/immunophenotypes do not achieve molecular/immunological complete remission (remain non-negative post-treatment);②Relapse during chemotherapy, early relapse within 12 months after treatment discontinuation, or late relapse ≥ 12 months after complete remission, with failure to achieve complete remission (MRD \> 1%) following 1 course of standard induction chemotherapy;③Relapsed after hematopoietic stem cell transplantation (HSCT);④Isolated bone marrow relapse, isolated extramedullary relapse (testicular leukemia, central nervous system leukemia), or combined relapse; * Tumor cells confirmed positive for CD19 by flow cytometry (FCM) or immunohistochemistry (IHC); * Expected survival ≥ 3 months from the date of signing the informed consent form (ICF); * Aged 3-18 years (inclusive), no gender restriction; * ECOG ≤ 2; * HGB ≥ 70 g/L, PLT ≥ 50×10⁹/L (recombinant human erythropoietin or blood transfusion permitted); * Liver and kidney functions, as well as cardiopulmonary functions, shall meet the following requirements:①LVEF≥50%;②Oxygen saturation ≥ 90%;③Total bilirubin ≤3×ULN;④ALT/AST\<3×ULN;⑤Serum creatinine≤2×ULN.If organ dysfunction links …