Tumor antigen-specific peptide-Major Histocompatibility Complex (pMHC) (pMHC)

The tumor antigen-specific peptide-Major Histocompatibility Complex (pMHC) is a molecular assembly on the surface of cancer cells consisting of a processed peptide fragment derived from a tumor-associated antigen or neoantigen bound to an MHC molecule (Frontiers in Immunology, 2020). This complex serves as the primary signal for recognition by the T-cell receptor (TCR) of CD8+ cytotoxic T lymphocytes, facilitating the immune system's ability to identify and eliminate aberrant cells (Nature Reviews Drug Discovery, 2021). In the context of immunotherapy, pMHC complexes are highly specific targets for engineered T-cell therapies (TCR-T), bispecific T-cell engagers, and TCR-like antibodies (Journal of Hematology & Oncology, 2023). Unlike traditional antibody targets that are limited to surface proteins, pMHC targets allow for the therapeutic targeting of intracellular proteins, which constitute the majority of the proteome (Molecular Cancer, 2022). However, effective targeting requires precise HLA matching and sufficient antigen presentation, as tumors often downregulate MHC expression to evade immune detection (Cancer Discovery, 2019). Therapeutic success depends on the high affinity and specificity of the drug for the specific peptide-HLA combination to avoid cross-reactivity with similar self-peptides in healthy tissues (Nature Communications, 2021). Notable examples of drugs targeting these complexes include Tebentafusp for uveal melanoma and Afamitresgene autoleucel for synovial sarcoma (FDA, 2022; FDA, 2024).

Other names

Peptide-MHC complexpMHC complexTumor-associated antigen-MHC complexNeoantigen-MHC complexTAA-HLA complexPeptide-HLA complex

Therapeutic agents, such as TCR-engineered T cells (TCR-T) or bispecific T-cell engagers (e.g., ImmTACs), utilize a T-cell receptor or a TCR-like binding domain to specifically recognize the peptide-MHC complex. Upon binding, these agents facilitate the formation of an immunological synapse between the T cell and the tumor cell, leading to the release of cytotoxic granules (perforin and granzymes) and subsequent apoptosis of the target cancer cell (Nature Reviews Drug Discovery, 2021; Frontiers in Immunology, 2020).