Synovial sarcoma, X breakpoint 2 peptide–Major Histocompatibility Complex (SSX2-pMHC)

The Synovial sarcoma, X breakpoint 2 (SSX2) peptide–Major Histocompatibility Complex (pMHC) is a specialized immunotherapy target found on the surface of various malignant cells. SSX2 is a member of the cancer-testis antigen (CTA) family, which is typically expressed only in the immune-privileged germ cells of the testis but becomes aberrantly expressed in cancers such as synovial sarcoma, melanoma, and prostate cancer (UniProt Q16385). Intracellular SSX2 proteins are processed by the proteasome into short peptides, such as the immunodominant SSX2 41-49 epitope (KASEKIFYV), which are then presented on the cell surface by HLA-A*02:01 molecules (PubMed: 10944131). This pMHC complex acts as a specific marker that can be recognized by engineered T-cell receptors (TCRs), allowing the immune system to target and eliminate tumor cells while sparing most healthy tissues. Clinical candidates like ADP-A2SSX utilize high-affinity TCRs to bind this complex and initiate a potent cytotoxic T-lymphocyte response (ClinicalTrials.gov: NCT04917523). Because the target involves an intracellular protein presented via MHC, it expands the range of druggable cancer antigens beyond traditional cell-surface proteins.

Other names

SSX2-HLA-A*02:01 complexSSX2 peptide-MHCSynovial sarcoma X breakpoint 2 antigenSSX2 41-49 peptide-HLA complexCancer-testis antigen SSX2

T-cell receptor (TCR) mediated recognition and cytotoxic T-lymphocyte activation