High-resolution profiling of neoantigen-specific T cell receptor activation signatures links moderate stimulation patterns to resilience and sustained tumor control

Neoantigen-specific T cell receptors (neoTCRs) promise a safe, highly personalized therapeutic approach in anti-tumor immunotherapy. Substantial progress has been made regarding their identification whereas detailed functional assessment of single TCR characteristics impacting therapeutic efficacy is lacking. We previously identified and functionally characterized neoTCRs specific for neoepitopes derived from KIF2C and SYTL4 demonstrating differences in functional avidity in a patient with metastatic melanoma. In this work, we now combined single-cell TCR- and RNA-sequencing using stimulated peripheral blood derived CD8+ T cells of this patient and thereby identified two new neoTCRs recognizing the previously identified mutated epitope KIF2CP13L. Analyzing patient-derived neoTCR expressing T cells, we detected distinct activation patterns as a measure for substantial heterogeneity within oligoclonal T cell responses towards neoantigens upon specific ex vivo-restimulation. Moreover, neoTCR-transgenic T cells from healthy donors were employed for detailed in vitro and in vivo fine-characterization focusing on TCR-intrinsic functional patterns. Most importantly, in a xenogeneic mouse model experimentally simulating rechallenge of tumor infiltrating lymphocytes (TILs) after adoptive T cell transfer, we found that T cells expressing neoTCRs with a moderate activation profile provide a stable and more sustained anti-tumor response upon repeated in vivo tumor challenge as compared to neoTCRs with a stronger, burst-like reactivity. These insights have significant implications for engineering TCR-transgenic T cells for therapeutic purposes. One Sentence SummaryCombining TCR specificity linked single-cell transcriptomics with in vitro and in vivo characterization of transgenic T cells helps to decipher functional potential and persistence of neoantigen-specific T cell receptors (TCRs) for TCR-transgenic T cell-based adoptive cellular anti-tumor immunotherapy.