The what, when and how of CAR T cell therapy for ALL.

Chimeric Antigen Receptor (CAR) T cells that have been engineered to target CD19 have shown great promise in patients with relapsed and refractory B cell acute lymphocytic leukemia with remission rates of 70-90%. Some remissions have successfully bridged patients to a curable allogeneic stem cell transplant, some responses have been durable without further treatment, and some patients have achieved durable remissions for relapsed ALL after allogeneic stem cell transplant. Cytokine release syndrome, correlating with the in vivo activation and expansion of T cells, and neurologic toxicity are the most significant side effects and approaches to better understand and manage these events are the subject of ongoing clinical trials. The decision to intervene with CARTs requires an individualized approach taking into consideration patient, disease and therapy related factors.