CAR-T immunotherapies: Biotechnological strategies to improve safety, efficacy and clinical outcome through CAR engineering

T cells engineered to express a chimeric antigen receptor (CAR) have re-shaped the way hematological malignancies are treated. Despite the overwhelming early clinical success, CAR-T therapies are associated with severe side-effects, disease relapse and often exhibit limited efficacy. In this Review article we summarize the most recent biotechnological advances that have been developed to enhance the efficacy and specificity of CAR-T therapies, as well as to address the key challenges associated with them. We place particular emphasis on the most recent clinical data that indicate which CAR-T populations are the most relevant to clinical success, and indicate how the molecular structure of the CAR receptor can affect clinical outcome. Finally, we outline what we believe is the next generation of immunotherapies.