Melanoma-associated peptide–MHC complex (pMHC)

Melanoma-associated peptide–MHC (pMHC) complexes are specialized molecular structures on the surface of melanoma cells that present fragments of intracellular proteins to the immune system. These complexes are formed when tumor-specific peptides, such as those derived from gp100, MAGE-A4, or NY-ESO-1, are loaded onto Major Histocompatibility Complex (MHC) molecules, most commonly the HLA-A*02:01 allele (7, 12). Their primary biological function is to serve as ligands for T-cell receptors (TCRs), enabling the detection and destruction of malignant cells by cytotoxic T lymphocytes (6, 11). In the context of melanoma, these complexes are vital therapeutic targets because they allow the immune system to "see" intracellular oncogenic or lineage-specific proteins that are otherwise inaccessible to standard antibody-based therapies (9, 13). Therapeutic agents targeting these complexes include bispecific T-cell engagers, such as the ImmTAC tebentafusp, and adoptive cell therapies like TCR-engineered T cells (TCR-T) (7, 8, 10). These drugs are engineered to recognize the specific peptide-HLA combination with high affinity, effectively bypassing the natural limitations of the endogenous immune repertoire (16, 19). However, the clinical application of these therapies is limited by HLA restriction, requiring patients to possess specific HLA alleles for the drug to function (4, 18). Safety profiles for these treatments often include cytokine release syndrome and on-target, off-tumor toxicities, such as skin rashes or vitiligo, which occur when the targeted antigen is also present on healthy melanocytes (7, 9, 16).

Other names

Melanoma antigen-MHC complexTumor-associated antigen-MHC complexHLA-peptide complexpHLAgp100-HLA-A*02:01 complexMAGE-A4-HLA-A*02 complexNY-ESO-1-HLA-A*02 complex

T-cell receptor (TCR) mediated recognition and redirection of T-cell cytotoxicity against tumor cells presenting specific intracellular antigens.