CD19 and precursor B-cell acute lymphoblastic leukemia: Remarkably, patients who experienced treatment failure or relapsed did not exhibit loss of the CD19 antigen.151 In Dai et al.’ study, after receiving another bispecific tandem CD19/CD22 CAR-T therapy, the patients demonstrated a favorable outcome, with a high MRD- complete response rate (100%) reached in B-ALL patients (n = 6); However, one patient relapsed at 5 months post-treatment with decreased CD22 density and negative CD19 expression.152 Additionally, the combination of different single-target CAR-T therapies is being investigated.