Arginase-1 Peptide Vaccine in Patients With Metastatic Solid Tumors

Arginase-1 (ARG1) is an enzyme that converts the amino acid arginine into urea and ornithine. ARG1 is mainly expressed in hepatocytes but different myeloid cells are also capable of ARG1-expression. An ARG1-induced arginine depletion suppresses T cell function through the impairment of the T cell receptor (TCR)-complex. A research group from the Center for Cancer Immune Therapy (CCIT) have identified spontaneous T cell reactivity against ARG1 peptides in peripheral blood mononuclear cells of cancer patients and healthy donors. The theoretic background for an ARG1 peptide vaccine is to activate ARG1-specific T cells to infiltrate the tumor microenvironment and eliminate ARG1-expressing immunosuppressive cells. The aim is to treat 10 patients with progressive solid tumors following treatment with standard of care agents. Patients will receive ARG1 vaccinations administered subcutaneously every third week for 45 weeks. The primary endpoint is to evaluate safety and toxicity. Immune responses will be assessed using blood- and tumor tissue samples and clinical responses are evaluated using RECIST 1.1.