T Cell Receptor-mimic STAR Conveys Superior Sensitivity over CAR in Targeting Tumors with Low-density Neoantigens

Targeting tumor-specific neoantigens is promising for cancer immunotherapy, yet their ultra-low expression on tumor cells poses significant challenges for T cell therapies. Here, we found that chimeric antigen receptors (CARs) exhibited 10-100 times lower sensitivity compared to T cell receptors (TCRs) when targeting p53R175H common neoantigen. To enhance CAR functionality, we introduce T cell receptor fusion construct (TRuC) and synthetic TCR and antigen receptor (STAR). Our data demonstrate that STAR, which incorporates TCR-mimic antibody fragments and complete TCR signaling machinery, optimally reproduces antigen sensitivity of TCRs. STAR outperforms both CAR and TRuC in redirecting both CD8+ and CD4+ T cells to recognize HLA class I neoantigens. In vitro, human primary T cells engineered with STAR kill multiple cancer cell lines with low neoantigen density better than CAR-T and TRuC-T cells. In tumor mouse models, STAR-T cells outperform CAR-T and TRuC-T cells in controlling neoantigen-low breast cancer and leukemia. Taken together, our findings highlight severe defects in CAR sensitivity and introduce STAR as a more sensitive synthetic receptor, providing a new framework for T cell-based immunotherapy targeting tumors with low neoantigen density. Overall design: To characterize transcriptional and chromatin accessibility changes in T cells expressing different antigen receptors, we performed RNA-Seq and ATAC-Seq on CD8+ and CD4+ CAR, TCR-1, and STAR-T cells, respectively, following coculture with T2 cells at three different neoantigen densities (0, 10, 100nM and 1µM) for 24 hours.