Engineering single-vector logic-gated CAR T cells with transgene sizes beyond current limitations

Engineering chimeric antigen receptor (CAR) T cells with logic-gated synthetic Notch (synNotch) receptor circuits can enhance specificity and mitigate on-target/off-tumor toxicity. However, the conventional synNotch system uses two lentiviral vectors encoding the synNotch receptor and inducible CAR, requiring dual transduction and cell sorting, which limits clinical translation. Integrating the synNotch-CAR circuit into a single lentiviral vector could overcome this limitation, yet manufacturing CAR T cells with large transgenes remains challenging, as increasing transgene size drastically reduces lentiviral titers and T cell transduction efficiency. Current production workflows compensate for low transduction efficiency by sorting transduced cells, further impeding clinical translation. Consequently, these constraints have limited the broader development of synNotch-CAR T cell therapies.

We engineered a single-vector synNotch (svsNotch) system that integrates all components of the conventional dual-vector circuit into one lentiviral vector to facilitate clinical translation. To overcome the low lentiviral titers and T cell transduction efficiency caused by the large svsNotch transgene, we established an optimized CAR T cell production workflow for effector T cells with large lentiviral transgenes.

Our optimized workflow increased T cell transduction rates by up to 14.8-fold and enabled the production of effector T cells with lentiviral transgenes exceeding the effective packaging capacity limit of 9.2 kb. As a proof of concept, we engineered human epidermal growth factor receptor 2 (HER2)-mesothelin (MSLN) svsNotch (9.2 kb), in which a synNotch receptor targeting HER2 regulates the expression of a second-generation 4-1BBζ CAR against MSLN to enable selective targeting of double-positive HER2⁺MSLN⁺ ovarian tumors. In vitro, HER2-MSLN svsNotch T cells demonstrated superior specificity to conventional dual-vector synNotch-CAR T cells, with selective cytotoxicity against HER2⁺MSLN⁺ but not HER2^koMSLN⁺ tumor cells. To enable in vivo monitoring, we engineered HER2-MSLN-click beetle green (CBG) svsNotch (10.1 kb) incorporating CBG luciferase. In mouse models using constitutive CAR T cells as controls, HER2-MSLN-CBG svsNotch T cells exhibited minimal cytotoxicity in the absence of HER2 and superior efficacy against HER2^lowMSLN^high and HER2^highMSLN^high tumors.

These data establish a framework for engineering logic-gated single-vector immunotherapies and provide an optimized workflow for generating CAR T cells with transgenes that exceed current size limitations.