T cells expressing chimeric antigen receptors (CARs) specific for the B-cell marker CD19 have shown impressive results in the treatment of B-cell malignancies. However, multiple clinical trials have also demonstrated the vulnerability of single-input CD19 CAR-T cell therapy to antigen escape, in which patients relapse with the emergence of CD19 tumor cells. Here, we report on the rational design and systematic optimization of bispecific CAR-T cells that trigger robust cytotoxicity against target cells expressing either CD19 or CD20. We demonstrate that optimized bi-specific CARs can rapidly eliminate large, engrafted tumors in vivo. We further demonstrate the bi-specific CAR-T cells ability to prevent tumor escape while single-input CD19 CAR-T cells succumb to the selective expansion of CD19 mutant cells, which are shown to arise spontaneously in engrafted mice. The CD19-OR-CD20 CAR is fully compatible with existing T-cell manufacturing procedures and implementable by current clinical protocols. These results present an effective solution to the challenge of antigen escape in CD19 CAR T-cell therapy, and they highlight the utility of structure-based rational design in the development of receptors with higher-level complexity.

Citation Format: Eugenia Zah, Meng-Yin Lin, Michael C. Jensen, Anne Silva-Benedict, Yvonne Y. Chen. Combating antigen escape with CD19/CD20 bispecific CAR-T cell therapy. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2016 Oct 20-23; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2017;5(3 Suppl):Abstract nr IA12.