Cyclic Peptide-Based CAR T Cells Exhibit Antigen-Dependent Cytotoxicity with Attenuated Cytokine Secretion

Current Chimeric Antigen Receptor (CAR) T-cell immunotherapies for solid tumors face challenges including limited persistence, the 'decoy effect' of shedding antigens, and severe side effects from excessive cytokine release. Traditional single-chain variable fragment (scFv)-based CARs, while effective, can induce intense T-cell activation, leading to systemic toxicity. There's a critical need for CAR designs that maintain potent anti-tumor efficacy while mitigating adverse events. Exploring novel antigen recognition modules, like cyclic peptides, offers a pathway to engineer CARs with improved safety profiles and enhanced stability.

Researchers developed a comprehensive workflow for constructing and evaluating disulfide-directed multicyclic peptide (DDMP)-based CAR T cells. The protocol spanned CAR construct design and generation, followed by rigorous in vitro and in vivo functional evaluation. They used DDMPs as the exemplar recognition module, leveraging their compact size and enhanced stability. The study involved generating Jurkat NFAT reporter cell lines and luciferase-expressing tumor target lines to standardize readouts. Functional assessments included NFAT activation, luminescence-based killing, flow cytometry-based cytolysis, and ELISA for cytokine analysis, normalizing all comparisons to CAR-positive cell numbers.

DDMP-based CAR T cells successfully mediated antigen-dependent cytotoxicity, demonstrating their ability to effectively target and eliminate tumor cells. A key finding was the observation of an attenuated cytokine secretion profile in these CAR T cells, suggesting a significant improvement in safety compared to conventional scFv-based designs. The inherent properties of DDMPs, including their markedly smaller molecular size (<5 kDa) and enhanced structural stability through disulfide-directed cyclization, were confirmed to be advantageous for CAR engineering. This structural robustness also supports broad tolerance to sequence diversification, facilitating systematic affinity and specificity optimization. The integrated pipeline allowed for rigorous, objective comparison of CAR T-cell efficacy and safety across various tumor models, ensuring that transduction efficiency did not confound results. Complementary readouts consistently cross-validated the observed efficacy and specificity.

DDMP-based CAR T cells demonstrated potent antigen-dependent cytotoxicity while exhibiting an attenuated cytokine secretion profile, supporting the development of potentially safer immunotherapies for solid tumors.