Dual-Targeted Umbilical Cord Blood CAR-T Cells Against CD19 and CD22 for the Treatment of Relapsed or Refractory Acute B-Cell Lymphoblastic Leukemia

Patients with relapsed/refractory B-cell acute lymphoblastic leukemia who meet eligibility criteria will receive fludarabine (30 mg/m²/d) and cyclophosphamide (300 mg/m²/d) for three consecutive days as lymphodepleting conditioning, followed by a single intravenous infusion of anti-CD19/CD22 dual-target cord blood-derived CAR-T cells. Dose assignment follows a "3+3" escalation design across three dose levels (4×10⁶, 8×10⁶, and 12×10⁶ CAR-T/kg, ±20%). Dose-limiting toxicity will be assessed during the first 14 days post-infusion to determine the maximum tolerated dose. After CAR-T infusion, patients will be monitored for safety and efficacy at protocol-specified time points through 3 months, with long-term follow-up continuing up to 15 years post-infusion. A total of 18 patients will be enrolled.