CAR T-cells in acute lymphoblastic leukemia: Current results

The marketing authorization of tisagenlecleucel, a 2nd generation of CD19-directed CAR T-cells, containing the 4-1 BB co-stimulatory domain, in 2017 in USA and in 2018 in EU, has revolutionized the therapeutic strategy in advanced B-cell acute lymphoblastic leukemia (B-ALL) in children, adolescents and young adults (AYAs) with relapsed or refractory disease. This innovative treatment, based on a "living drug", has shown very impressive short-term responses. However, safety profile and complex logistics require high expertise centers and tight collaborations between addressing and treating centers. Current research is exploring the possibility to move to first line ALL with high-risk features and/or first high-risk relapse. More efficient CAR T-cells products, are still lacking to counteract the escape mechanisms already described. Moreover, to define the bridge-to-CAR time for each patient remains a challenge to obtain optimal disease burden allowing expansion and persistence of CAR T-cells. Also difficult is to identify patients who will benefit from further therapy after infusion, such as allogeneic HSCT or may be immuno-modulatory treatment. Finally, CAR T-cells directed against T-ALL are only in their beginning but require more complex engineering process to avoid T- cell immune-deficiency or fratricide.