Melanoma-associated antigen 12 peptide–HLA-A*02:01 complex (MAGE-A12–HLA-A*02:01) (MAGE-A12–HLA-A*02:01)

The Melanoma-associated antigen 12 (MAGE-A12) peptide–HLA-A*02:01 complex is a specific molecular target consisting of a peptide fragment derived from the MAGE-A12 protein presented by the Human Leukocyte Antigen (HLA) allele A*02:01 (Morgan et al., 2013). MAGE-A12 is a member of the cancer-testis antigen (CTA) family, which is typically expressed in immune-privileged germ cells but becomes aberrantly expressed in various malignancies, including melanoma and non-small cell lung cancer (UniProt P43366). Because germ cells do not express MHC molecules, the presentation of MAGE-A12 peptides on HLA-A*02:01 was initially considered highly tumor-specific, making it an attractive target for adoptive T-cell therapies using engineered T-cell receptors (TCRs). However, clinical trials (e.g., NCT01273662) revealed that MAGE-A12 is also expressed at low levels in the human brain, specifically in the thalamus and other regions, leading to severe, sometimes fatal, neurotoxicity in patients treated with high-affinity TCRs (Morgan et al., 2013). This on-target, off-tumor toxicity resulted in necrotizing encephalopathy, highlighting the risks of targeting CTAs that may have previously unrecognized expression in vital tissues. Consequently, while the complex remains a potent target for cancer immunotherapy, its use requires extreme caution, stringent patient monitoring, and potentially the development of TCRs with optimized affinity to distinguish between tumor and healthy neural tissue.

Other names

MAGE-A12/HLA-A2MAGEA12-HLA-A*0201 complexMelanoma antigen family A 12 peptide-MHC complexMAGE-A12 peptide–HLA-A*02:01 complex on normal and tumor cells

T-cell receptor (TCR) mediated recognition and cytotoxic lysis of cells presenting the MAGE-A12 peptide in the context of HLA-A*02:01.