Abstract 5507: Generating optimal-affinity T cell receptors targeting the shared neoantigen KRAS G12V using the humanized TCR transgenic mouse platform HuTCR
Authors: Leliavski Alexei , Knackstedt Lorenz , Oduro Jennifer , Selck Claudia , Dhamodaran Arunraj , Blankenstein Thomas , Kieback Elisa , Poncette Lucia 
Published: June 2022

Background T cell receptor (TCR)-engineered T cell therapy (TCR-T) is a promising therapeutic modality to address key limitations of targeting solid tumors. Neoantigens are excellent therapeutic targets for TCR-T cell therapy, because they are highly specific and often homogeneously expressed in the tumor. While most neoantigens are patient-specific, there are rare exceptions of widely shared neoantigens, such as the driver oncogene KRAS containing mutations at position 12. The KRAS mutations G12C, G12D, and G12V are among the most common mutations in solid tumors, including indications with high unmet medical need, such as pancreatic, colorectal, and non-small cell lung cancer. Previous TCR-T approaches targeting KRAS G12V have been primarily focused on HLA-A*02:01, which appeared to be unable to present a mutant KRAS epitope. Here, we aim to generate TCRs of optimal affinity and high specificity to a KRAS G12V epitope in an HLA-agnostic manner using our HuTCR mouse platform.

Experimental procedures HuTCR mice represent a fully humanized TCR-MHC system and bear a diverse TCR repertoire, being transgenic for the entire human TCR alpha and beta gene loci and multiple human HLA class I molecules, while lacking murine TCRs and murine MHC class I molecules. The multi-HLA HuTCR mice were immunized with KRAS G12V peptides or the neoantigen-encoding adenovirus, leading to robust immune responses.

Results Single-cell sequencing of responding T cells revealed HLA-A*11:01-restricted immune responses, indicating that the epitope presented on HLA-A*11:01 was more immunogenic than epitopes presented on other HLA alleles. HLA-A*11:01 is expressed in approximately 11% of the United States and the European Union population and in around 30% of Asian populations. We were able to generate 30 KRAS G12V-specific TCRs, which we characterized for efficacy and safety. We selected a lead candidate, which demonstrated potent anti-tumor efficacy and no detectable off-target toxicity, to be pursued further into the clinic.

Conclusion Using the HuTCR mouse platform, we identified TCRs of optimal affinity and high specificity for the shared oncogenic KRAS G12V mutation. Importantly, the HuTCR platform was a powerful tool enabling us to determine the HLA allele responsible for generating the strongest immune response, and consequently, to define the patient population that may benefit most from targeting KRAS G12V.

Citation Format: Alexei Leliavski, Lorenz Knackstedt, Jennifer Oduro, Claudia Selck, Arunraj Dhamodaran, Thomas Blankenstein, Elisa Kieback, Lucia Poncette. Generating optimal-affinity T cell receptors targeting the shared neoantigen KRAS G12V using the humanized TCR transgenic mouse platform HuTCR [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5507.