Melanoma-associated antigen 3 peptide–MHC complex (MAGE-A3 pMHC)

The Melanoma-associated antigen 3 (MAGE-A3) peptide–MHC complex is a specialized immunological target consisting of a processed peptide fragment of the MAGE-A3 protein bound to a Major Histocompatibility Complex (MHC) molecule, typically HLA-A1 or HLA-A2, on the surface of tumor cells (UniProt P43357). MAGE-A3 is a member of the cancer-testis antigen (CTA) family, characterized by high expression in various cancers—including melanoma and non-small cell lung cancer—while remaining absent in normal adult tissues except for the immune-privileged testis. This restricted expression profile makes the pMHC complex an attractive target for T-cell-based immunotherapies, such as T-cell receptor (TCR) engineered T-cells and bispecific T-cell engagers, which are designed to recognize the specific peptide-HLA configuration. Historically, clinical development has been complicated by severe safety issues; for instance, early TCR-T therapies targeting MAGE-A3 resulted in fatal cardiotoxicity due to unexpected cross-reactivity with the muscle protein Titin (Linette et al., Blood 2013), and neurotoxicity due to cross-reactivity with MAGE-A12 in the brain (Morgan et al., JCO 2013). Despite these setbacks, refined targeting of the MAGE-A3 pMHC complex remains a major focus in precision oncology, with newer agents like IMC-C103C undergoing clinical evaluation (NCT02111811).

Other names

MAGE-A3/HLA complexMAGE-A3 peptide-HLA complexMelanoma antigen family A 3 peptide-MHCMAGE3 peptide-MHCMAGE-A3/HLA-A*01 complexMAGE-A3/HLA-A*02 complex

T-cell receptor (TCR) mediated recognition leading to T-cell activation and targeted lysis of tumor cells expressing the MAGE-A3 peptide in the context of specific HLA alleles.