This article reports a case of relapsed B-cell acute lymphoblastic leukemia (B-ALL) in a patient who underwent multiple lines of immunotherapy, including CD19- and CD22-targeted CAR-T cells, inotuzumab ozogamicin (an anti-CD22 antibody-drug conjugate), and belimumab (a CD19/CD3 bispecific T-cell engager), followed by allogeneic HSCT from an unrelated donor. This evidence concerns the gene CD22 and B-cell acute lymphoblastic leukemia.