Abstract 3176: CD19/CD22 bispecific CAR-T cells are effective in CD19 loss B-cell tumor models

Abstract Background: Chimeric antigen receptor T (CAR-T) cell therapy targeting CD19 can significantly improve the long-term survival rate of patients with relapsed or refractory leukemia. However, CD19 absence or loss leads to resistance of the B-lymphoblastic leukemia cells to CD19 CAR-T cells and the patients will relapse. To solve the problem, we developed bispecific CAR-T cells that target CD19 and CD22 and evaluated their antitumor effects. Methods: The CD19/CD22 bispecific CAR-T cells were generated through the transduction of lentiviruses that simultaneously carry the genes for both CD19 CAR and CD22 CAR, including an anti-CD19 scFv, an anti-CD22 scFv, a CD8 hinge region, a CD8 transmembrane region, a 41BB intracellular region and a CD3ζ intracellular region. In vitro tumor killing assay on NALM6 and Ramos cells and in vivo efficacy studies on Ramos cell line-derived xenografts (CDX) were performed. Results: In in vitro studies, the CD19/CD22 CAR-T cells killed wild-type (WT) NALM6 and WT Ramos cells effectively like CD19 CAR-T; the CD19/CD22 CAR-T cells but not CD19 CAR-T cells killed NALM6 cells with loss of CD19 protein but expression of CD22 protein (CD19-CD22+) and CD19-CD22+ Ramos cells effectively. In in vivo studies, the CD19/CD22 CAR-T cells significantly prolonged the survival of mice bearing CD19-CD22+ Romas cells than CD19 CAR-T. Conclusion: The CD19/CD22 bispecific CAR-T cells effectively kill B-cell tumors with CD19 loss both in vitro and in vivo, which will have a superior therapeutic effect on patients with relapse due to loss of CD19 protein. Citation Format: Jiao Jiao. CD19/CD22 bispecific CAR-T cells are effective in CD19 loss B-cell tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 3176.