Assessment of Senl_B19 CAR-T Cells in Relapsed/Refractory CD19+ B-ALL

This study tests a new CAR-T cell therapy (a type of treatment where your own immune cells are engineered to fight cancer) for children and young adults with relapsed or treatment-resistant B-cell acute lymphoblastic leukemia (ALL), a type of blood cancer. **You may be eligible if...** - You are 3 to 25 years old - You have been diagnosed with B-cell ALL that has come back or stopped responding to treatment - Your cancer cells test positive for the CD19 marker - You are in reasonably good health aside from the cancer **You may NOT be eligible if...** - You have active, uncontrolled infections (including HIV, active hepatitis) - You have had prior CAR-T therapy targeting CD19 - You have significant organ dysfunction - You have untreated or active cancer in the brain or spinal fluid Talk to your doctor to see if this trial is right for you.