Abstract A008: Fine-Tuning Signal Strength in CD5 CAR-NK Cells for Targeted T Cell Cancer Therapy

T cell hematological malignancies are aggressive blood cancers that remain challenging despite various treatments. Current chimeric antigen receptor (CAR)-T and natural killer (NK) therapies show potential but struggle with nonselective elimination during tumor targeting. This study aims to develop a safe and effective therapy targeting T cell malignancies using CD5 CAR-NK cells. The strength of CAR signaling, determined by the single-chain variable fragment (scFv) and CAR expression level, enables selective antigen recognition while protecting normal T cells. We aimed at optimizing CAR-NK (OptiCAR-NK) to enhance anti-cancer effects against CD5+ tumors and mitigate on-target off-tumor toxicity in vitro and in vivo. By modulating scFv and CAR expression levels through single-cell isolation and mRNA transfection, we identified variations in the activity of CAR-NK cells against CD5+ cells. In vivo studies using xenograft and humanized mouse models confirmed the selective anti-tumor effects and safety of OptiCAR-NK cells. OptiCAR-NK with optimal scFv and CAR expression showed strong anti-tumor activity with minimal toxicity to normal cells. We identified that fine-tuning CAR is important to harnessing NK cells' innate discriminatory ability, activated by endogenous ligands on target cells. Optimized modulation of scFv and CAR expression is crucial for designing a CAR that achieves high anti-cancer efficacy and is safe in normal cells. Our results suggest a promising avenue for optimized CD5 CAR-NK cell therapy to manage T cell malignancies while minimizing off-tumor effects. Citation Format: Seona Jo, Yu Bin Lee, Tae-Don Kim. Fine-Tuning Signal Strength in CD5 CAR-NK Cells for Targeted T Cell Cancer Therapy [abstract]. In: Proceedings of the AACR Immuno-Oncology Conference (AACR IO): Discovery and Innovation in Cancer Immunology: Revolutionizing Treatment through Immunotherapy; 2026 Feb 18-21; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Immunol Res 2026;14(2 Suppl):Abstract nr A008.