RecruitingPhase 1Drug trialCD19-CD22-Bispecific Chimeric Antigen Receptor (CAR) T Cell Therapy for Pediatric Patients With Acute Lymphoblastic LeukemiaThis study is a phase I study designed to evaluate the safety of CD19-CD22-CAR T cells. Primary Objective: To determine the safety profile and propose the recommended phase 2 dose (RP2D) of autologous CD19-CD22-CAR T cells in patients ≤ 21 years of age with recurrent/refractory CD19- and/or CD22-positive leukemia. Secondary Objective: To evaluate the anti-leukemic activity of CD19-CD22-CAR T cells.