Graduate student Univ. of Notre Dame, United States
Disclosure(s):
Bassant Y. Eldaly, PhD: No financial relationships to disclose
Introduction/Rationale: For over 30 years, KRAS, a key oncogene, was deemed “undruggable” due to its intracellular nature and lack of a suitable binding site, posing a challenge for monoclonal antibody and small molecule targeting. Immunotherapy offers a promising approach by leveraging T cell receptor (TCR) recognition of mutant KRAS peptides presented by human leukocyte antigen (HLA) class I on cancer cell surfaces. Driver mutations like KRAS-G12D generate public neoantigens shared among patients, making them ideal targets for T cell therapy.
Methods: We investigated the structural and biophysical basis for the specificity of five patient-derived TCRs that recognize the KRAS-G12D neoantigen presented by HLA-A11. To define their binding mechanisms, we solved the crystal structures of three representative TCRs in complex with KRAS-G12D/HLA-A11 and measured their binding affinities using surface plasmon resonance (SPR).
Results: All five TCRs recognize KRAS-G12D with high specificity. Structural analysis revealed a large conserved conformational shift in the peptide upon TCR binding, with residues A5 and D6 reorienting from an exposed to a downward-facing position, adopting a polyproline type II conformation, indicating a shared recognition mechanism.
Conclusion: Building on these insights, we synthesized N-amino-modified KRAS peptides designed to stabilize this conformation and test whether pre-paying the entropic penalty enhances TCR binding. These findings lay the groundwork for engineering a KRAS superagonist peptide and advancing T cell-based immunotherapies targeting KRAS.
