Arginase 1-derived peptide 169–206 presented on MHC (ARG1 (169-206)/MHC)

Arginase 1-derived peptide 169–206 presented on MHC is a therapeutic target used in the development of cancer immunotherapies, specifically peptide vaccines (NCI Drug Dictionary). Arginase 1 (ARG1) is an enzyme frequently overexpressed by tumor cells and immunosuppressive myeloid cells, such as myeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages (TAMs) (Frontiers in Immunology, 2022). These cells deplete L-arginine in the tumor microenvironment, which inhibits T-cell proliferation and function (PubMed, 2019). The 38-amino acid peptide, often referred to as ArgLong2, contains multiple epitopes that are presented on both MHC class I and II molecules, allowing for the stimulation of a robust pro-inflammatory response from both CD4+ and CD8+ T cells (IO Biotech). Drugs like IO112 are designed to activate these ARG1-specific T cells, which then target and eliminate the immunosuppressive cells within the tumor (Journal for ImmunoTherapy of Cancer, 2025). By removing these cells, the vaccine helps restore L-arginine levels and reprograms the tumor microenvironment to support anti-tumor activity. This approach is currently being investigated in clinical trials for various solid tumors and hematological malignancies, demonstrating a favorable safety profile with mostly low-grade adverse events (ClinicalTrials.gov).

Other names

ArgLong2Arginase 1 peptide 169-206ARG1 169-206Arginase 1 epitope

Activation of Arginase 1-specific CD4+ and CD8+ T cells to target and eliminate Arginase 1-expressing immunosuppressive cells (MDSCs, TAMs) and cancer cells, thereby restoring L-arginine levels and enhancing anti-tumor immunity.