• Jennifer S Y Ma, Ji Young Kim, Stephanie A Kazane, Sei-Hyun Choi, Hwa Young Yun, Min Soo Kim, David T Rodgers, Holly M Pugh, Oded Singer, Sophie B Sun, Bryan R Fonslow, James N Kochenderfer, Timothy M Wright, Peter G Schultz, Travis S Young, Chan Hyuk Kim, and Yu Cao.
• Department of Biology, California Institute for Biomedical Research, La Jolla, CA 92037;
• Proc. Natl. Acad. Sci. U.S.A. 2016 Jan 26; 113 (4): E450-8.

AbstractThe adoptive transfer of autologous T cells engineered to express a chimeric antigen receptor (CAR) has emerged as a promising cancer therapy. Despite impressive clinical efficacy, the general application of current CAR-T--cell therapy is limited by serious treatment-related toxicities. One approach to improve the safety of CAR-T cells involves making their activation and proliferation dependent upon adaptor molecules that mediate formation of the immunological synapse between the target cancer cell and T-cell. Here, we describe the design and synthesis of structurally defined semisynthetic adaptors we refer to as "switch" molecules, in which anti-CD19 and anti-CD22 antibody fragments are site-specifically modified with FITC using genetically encoded noncanonical amino acids. This approach allows the precise control over the geometry and stoichiometry of complex formation between CD19- or CD22-expressing cancer cells and a "universal" anti-FITC-directed CAR-T cell. Optimization of this CAR-switch combination results in potent, dose-dependent in vivo antitumor activity in xenograft models. The advantage of being able to titrate CAR-T-cell in vivo activity was further evidenced by reduced in vivo toxicity and the elimination of persistent B-cell aplasia in immune-competent mice. The ability to control CAR-T cell and cancer cell interactions using intermediate switch molecules may expand the scope of engineered T-cell therapy to solid tumors, as well as indications beyond cancer therapy.

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