IL-13Rα2/TGF-ß bispecific CAR-T cells counter TGF-ß-mediated immune suppression and potentiate anti-tumor responses in glioblastoma.

BACKGROUND: Chimeric antigen receptor (CAR)-T cell therapies targeting glioblastoma (GBM)-associated antigens such as interleukin-13 receptor subunit alpha-2 (IL-13Rα2) have achieved limited clinical efficacy to date, in part due to an immunosuppressive tumor microenvironment (TME) characterized by inhibitory molecules such as transforming growth factor-beta (TGF-ß). The aim of this study was to engineer more potent GBM-targeting CAR-T cells by countering TGF-ß-mediated immune suppression in the TME. METHODS: We engineered a single-chain, bispecific CAR targeting IL-13Rα2 and TGF-ß, which programs tumor-specific T cells to convert TGF-ß from an immunosuppressant to an immunostimulant. Bispecific IL-13Rα2/TGF-ß CAR-T cells were evaluated for efficacy and safety against both patient-derived GBM xenografts and syngeneic models of murine glioma. RESULTS: Treatment with IL-13Rα2/TGF-ß CAR-T cells leads to greater T-cell infiltration and reduced suppressive myeloid cell presence in the tumor-bearing brain compared to treatment with conventional IL-13Rα2 CAR-T cells, resulting in improved survival in both patient-derived GBM xenografts and syngeneic models of murine glioma. CONCLUSION: Our findings demonstrate that by reprogramming tumor-specific T-cell responses to TGF-ß, bispecific IL-13Rα2/TGF-ß CAR-T cells resist and remodel the immunosuppressive TME to drive potent anti-tumor responses in GBM.

Navigating CAR-T cells through the solid-tumour microenvironment.

The adoptive transfer of T cells that are engineered to express chimeric antigen receptors (CARs) has shown remarkable success in treating B cell malignancies but only limited efficacy against other cancer types, especially solid tumours. Compared with haematological diseases, solid tumours present a unique set of challenges, including a lack of robustly expressed, tumour-exclusive antigen targets as well as highly immunosuppressive and metabolically challenging tumour microenvironments that limit treatment safety and efficacy. Here, we review protein- and cell-engineering strategies that seek to overcome these obstacles and produce next-generation T cells with enhanced tumour specificity and sustained effector function for the treatment of solid malignancies.

Getting better mileage with logically primed CARs.

Although remarkably successful against liquid tumors, chimeric antigen receptor (CAR)-T cell therapy has been stymied by solid tumors, limited by inadequate specificity and poor efficacy. Pairing synthetic Notch (synNotch) receptors with CARs, Choe et al. and Hyrenius-Wittsten et al. engineer T cells that more precisely and potently combat solid tumors.

CAR-T design: Elements and their synergistic function.

Chimeric antigen receptor (CAR) T cells use re-engineered cell surface receptors to specifically bind to and lyse oncogenic cells. Two clinically approved CAR-T-cell therapies have significant clinical efficacy in treating CD19-positive B cell cancers. With widespread interest to deploy this immunotherapy to other cancers, there has been great research activity to design new CAR structures to increase the range of targeted cancers and anti-tumor efficacy. However, several obstacles must be addressed before CAR-T-cell therapies can be more widely deployed. These include limiting the frequency of lethal cytokine storms, enhancing T-cell persistence and signaling, and improving target antigen specificity. We provide a comprehensive review of recent research on CAR design and systematically evaluate design aspects of the four major modules of CAR structure: the ligand-binding, spacer, transmembrane, and cytoplasmic domains, elucidating design strategies and principles to guide future immunotherapeutic discovery.

Engineering primary T cells with chimeric antigen receptors for rewired responses to soluble ligands.

The expression of synthetic receptors in primary T cells enables the programming of user-defined responses when designing T-cell therapies. Chimeric antigen receptors (CARs) are synthetic receptors that have demonstrated efficacy in cancer therapy by targeting immobilized antigens on the surface of malignant cells. Recently, we showed they can also rewire T-cell responses to soluble ligands. In contrast to other synthetic receptors, CARs are not only readily engineered by rational design, but also clinically translatable, with robust function in primary human T cells. This protocol discusses design principles for CARs responsive to soluble ligands and delineates steps for producing T cells expressing synthetic receptors. Functional assays for quantifying the ability of CAR T cells to sense and respond to soluble ligands are also presented. This protocol provides a framework for proficient immune-cell researchers to test novel T-cell therapies targeting soluble ligands in <2 weeks.

TGF-ß-responsive CAR-T cells promote anti-tumor immune function.

A chimeric antigen receptor (CAR) that responds to transforming growth factor beta (TGF-ß) enables the engineering of T cells that convert this immunosuppressive cytokine into a potent T-cell stimulant. However, clinical translation of TGF-ß CAR-T cells for cancer therapy requires the ability to productively combine TGF-ß responsiveness with tumor-targeting specificity. Furthermore, the potential concern that contaminating, TGF-ß?producing regulatory T (Treg) cells may preferentially expand during TGF-ß CAR-T cell manufacturing and suppress effector T (Teff) cells demands careful evaluation. Here, we demonstrate that TGF-ß CAR-T cells significantly improve the anti-tumor efficacy of neighboring cytotoxic T cells. Furthermore, the introduction of TGF-ß CARs into mixed T-cell populations does not result in the preferential expansion of Treg cells, nor do TGF-ß CAR-Treg cells cause CAR-mediated suppression of Teff cells. These results support the utility of incorporating TGF-ß CARs in the development of adoptive T-cell therapy for cancer.