Safety and Efficacy of CAR T Cell Therapy in Patients with R/r B-ALL

This study is testing CAR-T cell therapy for children and teenagers with relapsed or refractory B-cell acute lymphoblastic leukemia (B-ALL) — a blood cancer that has come back or stopped responding to treatment. CAR-T therapy involves modifying the patient's own immune cells to recognize and destroy leukemia cells carrying the CD19 protein on their surface. **You may be eligible if...** - You are between 2 and 18 years old with CD19-positive B-ALL that has relapsed or not responded to treatment - Cancer cells are present in the bone marrow - You are healthy enough to tolerate the cell collection process (apheresis) - Your expected life expectancy is more than 12 weeks - Your physical function score is above 50% - At least 7 days have passed since your last chemotherapy or steroid treatment - A potential stem cell donor is available if needed afterward **You may NOT be eligible if...** - You have another active cancer - You have brain or central nervous system involvement by leukemia, or significant neurological symptoms - You have active graft-versus-host disease (from a prior transplant) - You received radiation within the past 14 days - You have previously received anti-CD19 or anti-CD20 therapies - You had a cell therapy or donor lymphocyte infusion within the past 30 days - You have a severe active infection or significant organ dysfunction Talk to your doctor to see if this trial is right for you.