Anti-CRLF2-R/TSLPR Chimeric Antigen Receptor T Cells (TSLPR-CART) in Participants With Recurrent or Refractory CRLF2-R/TSLPR-Overexpressing B-Cell Acute Lymphoblastic Leukemia (B-ALL)

Background: B-cell acute lymphoblastic leukemia (B-ALL) is a type of blood cancer. Some people with B-ALL have a gene mutation that makes the disease hard to treat. The mutation causes cancer cells to make too much of a protein called thymic stromal lymphopoietin receptor (TSLPR). Chimeric antigen receptor (CAR) T cell therapy is a treatment that takes immune cells (T cells) from a person s body and modifies them to attack specific proteins. Researchers want to test whether TSLPR-CART cells can be given safely to adults with forms of B-cell leukemia, and to learn whether the treatment may help fight these cancers. Objective: To test TSLPR-CART in people with B-ALL. Eligibility: People aged 18 years and older with B-ALL that did not respond or returned after treatment. They must have TSLPR on their B-ALL. Design: Participants will be screened. They will have imaging scans and tests of their heart function. Samples will be taken from their bone marrow. They will have a lumbar puncture: A needle will be inserted into their back to collect a sample of the fluid around the spinal cord. Participants will undergo leukapheresis: Blood will be taken from their body through a tube. The blood will pass through a machine that separates out the T cells. The remaining blood will be returned to the body through a different tube. The T cells will be used to create TSLPR-CART. Participants will take chemotherapy over 5 days to prepare their body for the therapy; then they will receive the modified cells through a tube inserted into a vein. Staying in the hospital during part of the treatment is expected and participants will be monitored locally to evaluate for side effects. Approximately 1 month after receiving TSLPR-CART, participants will undergo evaluations to see how the TSLPR-CART impacted their leukemia. Participants will have follow-up visits for 2 years after TSLPR-CART either at NIH or at home....