Chimeric Antigen Receptor T Cell Therapy for Acute Lymphoblastic Leukemia

Chimeric receptor antigen (CAR) T cells are an innovative cellular immunotherapeutic approach that involves genetic modification of T cells to express CAR targeting tumor antigen. Prior to the development of CAR-T, the only potential cure for patients with relapsed or refractory (RR) acute lymphoblastic leukemia (ALL) was allogeneic hematopoietic stem cell transplantation (HSCT). Several CAR-T cell products have been studied in prospective clinical trials which ultimately have resulted in the approval of one anti-CD19 CAR-T cell product in pediatric RR ALL: tisagenlecleucel (CD3ζ and 41BB). While some patients achieve durable responses with CAR-T, lack of response and relapse remains clinical challenges. Reasons for sub-optimal response include lack of CAR-T cell persistence and target antigen down-regulation. Future CARs are under development to improve long-term persistence and to be able to overcome resistance mechanisms associated with the disease and the hostile tumor microenvironment. With evolving understanding about CARs and new constructs under investigation, there is optimism that future products will improve the safety and efficacy from the current standard of care.