Mutant RAS peptide-Major Histocompatibility Complex (RAS-pMHC)

Mutant RAS neoantigen peptides presented on MHC (Major Histocompatibility Complex) are cell-surface complexes consisting of a mutated RAS protein fragment (e.g., KRAS G12D, G12V, or G12C) bound to an HLA molecule (NIH, 2022). These complexes serve as highly specific "flags" that distinguish malignant cells from healthy ones, as the somatic mutations in the RAS gene are unique to the tumor (Cancer.gov, 2016). Because RAS is an intracellular protein, it was historically considered "undruggable" by traditional antibodies; however, the presentation of its mutant peptides on MHC allows the immune system to recognize it via T-cell receptors (TCRs) (Nature Communications, 2022). Current therapeutic approaches targeting these complexes include TCR-engineered T-cell (TCR-T) therapies, bispecific T-cell engagers (BiTEs), and neoantigen vaccines (Frontiers in Oncology, 2024). A significant challenge in targeting these neoepitopes is their low abundance on the cell surface and the high degree of HLA restriction, meaning a drug must be matched to both the specific RAS mutation and the patient's HLA type (AACR, 2022). Recent innovations, such as the HapImmune platform, utilize covalent inhibitors to enhance the presentation and stability of these neoantigens, potentially broadening their therapeutic utility (PNAS, 2024).

Other names

RAS neoepitopeRAS-HLA complexMutant RAS-MHC-I complexpMHCpHLARAS-pMHC complex

Therapeutic agents targeting this complex utilize high-affinity receptors (TCRs or TCR-mimetic antibodies) to specifically recognize the mutant RAS peptide presented by MHC molecules. This recognition triggers T-cell mediated cytotoxicity, either through the infusion of TCR-engineered T cells (TCR-T) or the use of bispecific molecules that bridge the target complex with CD3-positive T cells (Nature Communications, 2022; PNAS, 2024). Vaccines further enhance this process by priming the immune system to recognize these specific neoepitopes (Frontiers in Oncology, 2024).