Patient-derived high functional avidity TCR empowers diverse T cell subsets for tumour immunotherapy

Cancer-testis antigens (CTAs) are attractive targets for tumour immunotherapy due to their restricted expression in human malignancies and broad population-level prevalence. However, naturally occurring CTA-reactive T cells are often exhausted or functionally compromised, limiting their direct therapeutic utility. Here, using a non-viral orthotopic TCR replacement system, we systematically evaluated two patient-derived HLA-A*02:01-restricted TCRs specific for the synovial sarcoma X breakpoint 2 (SSX2) epitope SSX2_41-49 (KASEKIFYV). Although both TCRs conferred SSX2 specificity, one displayed markedly higher functional avidity and superior antigen responsiveness. Primary CD8⁺ T cells redirected with this high-avidity TCR showed CD8-independent recognition, enhanced tetramer binding, and stronger functional responses against SSX2-expressing tumour cells. Notably, the same TCR also redirected CD4⁺ T cells toward the MHC-I-restricted SSX2 epitope, inducing polyfunctional cytokine release and direct tumour cytotoxicity. Moreover, it remained highly functional when introduced into unconventional T cell subsets, including NKT and γδ T cells, thereby expanding the range of potential cellular platforms for TCR-based therapeutics. Together, these findings identify a naturally derived, high functional avidity SSX2-reactive TCR with broad activity across conventional and unconventional T cell subsets, supporting its further development for future TCR-T cell-based immunotherapies.