For example, although the early response rates in B-ALL patients are considerable, relapse occurs in many patients, which is usually attributed to the loss of CAR-T cell function and persistence.399 Moreover, tumors undergo genetic changes that cause the loss of the target antigen, resulting in treatment resistance.403 In cases where CD19-targeted CAR-T cells are used, some relapsed patients have CD19-negative leukemic cells, leading to treatment failure.399,404,405 This highlights the need for multitarget CAR designs to prevent tumor escape. Here, CD19 is linked to precursor B-cell acute lymphoblastic leukemia.