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Background <p>Chimeric antigen receptor (CAR)-T cell therapies have achieved remarkable success in hematologic malignancies, yet their clinical utility remains limited by safety concerns, limited persistence, and T-cell exhaustion driven by continuous receptor signaling. While switchable CAR designs provide external control, many reported systems are irreversible, strictly binary, or compromise CAR-T potency.</p> Methods <p>We engineered an optimized chemically switchable CAR platform (CSN CAR) that pharmacologically regulates antigen engagement by controlling the surface expression of the full-length CAR. An NS3 protease module was embedded within the CAR construct to enable drug-dependent stabilization of intact CAR on T cells. Using engineered CAR-T cells, we quantified drug-controlled activation, cytotoxicity, and cytokine release against CD19⁺ tumor cells by flow cytometry and ELISA in vitro. We further screened clinically approved NS3/4A inhibitors in CAR-HEK and CAR-T cells to identify optimal small-molecule controllers. A chronic stimulation model was established to assess CAR-T persistence and exhaustion-associated phenotypes in vitro.</p> Results <p>CSN CAR-T cells enabled precise, dose-dependent regulation of CAR surface density, cytokine production, and cytotoxicity. In the OFF state, switchable CAR-T cells showed minimal basal activity, consistent with reduced antigen-driven activation and cytokine release in the absence of drug in the experimental conditions. Upon drug addition, intact surface CAR was detectable within 1&#xa0;h, reaching ~ 80% of peak observed CAR expression by 4&#xa0;h. Reversible suppression of CAR expression enabled attenuation of cytotoxicity toward normal CD19⁺ B cells in vitro after target-cell reduction, supporting a potential strategy to mitigate prolonged on-target/off-tumor activity. Under chronic stimulation, switchable CAR-T cells exhibited reduced exhaustion-associated markers, more stable CAR expression, and preferential differentiation toward a central memory phenotype.</p> Conclusion <p>Together, these findings establish CSN CAR as a reversible and tunable switchable CAR-T platform enabled by clinically approved NS3/4A inhibitors, supporting controllable modulation of CAR activity with potential applications for improving the precision and safety of CAR-T cell therapy.</p>

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Precise control of switchable chimeric antigen receptor T cells allows enhanced safety and less T cell exhaustion

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年6月17日

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  • Zihan Anna Zhang,
  • Logan Herring,
  • Thuzar Hla Shwe,
  • Yue Hu,
  • Xiaotong Song,
  • Wenyue Cao,
  • Wenshe Ray Liu

摘要

Background

Chimeric antigen receptor (CAR)-T cell therapies have achieved remarkable success in hematologic malignancies, yet their clinical utility remains limited by safety concerns, limited persistence, and T-cell exhaustion driven by continuous receptor signaling. While switchable CAR designs provide external control, many reported systems are irreversible, strictly binary, or compromise CAR-T potency.

Methods

We engineered an optimized chemically switchable CAR platform (CSN CAR) that pharmacologically regulates antigen engagement by controlling the surface expression of the full-length CAR. An NS3 protease module was embedded within the CAR construct to enable drug-dependent stabilization of intact CAR on T cells. Using engineered CAR-T cells, we quantified drug-controlled activation, cytotoxicity, and cytokine release against CD19⁺ tumor cells by flow cytometry and ELISA in vitro. We further screened clinically approved NS3/4A inhibitors in CAR-HEK and CAR-T cells to identify optimal small-molecule controllers. A chronic stimulation model was established to assess CAR-T persistence and exhaustion-associated phenotypes in vitro.

Results

CSN CAR-T cells enabled precise, dose-dependent regulation of CAR surface density, cytokine production, and cytotoxicity. In the OFF state, switchable CAR-T cells showed minimal basal activity, consistent with reduced antigen-driven activation and cytokine release in the absence of drug in the experimental conditions. Upon drug addition, intact surface CAR was detectable within 1 h, reaching ~ 80% of peak observed CAR expression by 4 h. Reversible suppression of CAR expression enabled attenuation of cytotoxicity toward normal CD19⁺ B cells in vitro after target-cell reduction, supporting a potential strategy to mitigate prolonged on-target/off-tumor activity. Under chronic stimulation, switchable CAR-T cells exhibited reduced exhaustion-associated markers, more stable CAR expression, and preferential differentiation toward a central memory phenotype.

Conclusion

Together, these findings establish CSN CAR as a reversible and tunable switchable CAR-T platform enabled by clinically approved NS3/4A inhibitors, supporting controllable modulation of CAR activity with potential applications for improving the precision and safety of CAR-T cell therapy.