A bi-specific CAR T-cell targeting CD19 and/or CD22 (CD19-22.BB.z-CAR) was developed to prevent disease recurrence in these patients after CD19 CAR T-cell therapy, and a Phase I clinical trial (NCT03233854) in patients with R/R B-ALL and DLBCL was conducted. The gene discussed is CD19; the disease is acute lymphoblastic leukemia.