Functional avidity enhancement of a T-cell receptor targeting the KRAS^G12D cancer neoantigen

Engineered T cell receptors (TCRs) targeting neoantigens represent a transformative approach in cancer immunotherapy, yet their clinical potential is limited by low natural TCR avidity and the risk of off-target toxicity from over-engineered TCRs with excessive high-affinity. Here, we developed a TCR engineering platform to enhance the functional avidity of a TCR targeting the KRAS G12D mutation (KRAS^G12D) while avoiding reactivity to the wild-type (WT) peptide. We separately constructed CDR3α- and CDR3β-focused TCR libraries derived from an HLA-A*11:01-restricted KRAS^G12D-specific TCR and screened them using alternating positive and negative selection: KRAS^G12D-pulsed antigen-presenting cells (APCs) drove functional avidity, while KRAS^WT-pulsed APCs eliminated cross-reactive clones. From these libraries, we identified CDR3α variants with modest avidity gains and reduced off-target reactivity, and CDR3β variants with significant avidity enhancement and potent tumor cytotoxicity, albeit with variable cross-reactivity profiles. This strategy enables precision engineering of neoantigen-specific TCRs, balancing therapeutic efficacy and safety for adoptive transfer TCR-T therapy.