Thymotrinan (also known as RGH-0205) is a protected synthetic tripeptide patented by Hungarian multinational pharmaceutical and biotechnology company Gedeon Richter Plc. (Richter, Gedeon, Vegyeszeti Gyar Rt) as an immunomodulating agent. Thymotrinan is the shortest thymopoietin fragment, that induces differentiation of CD90 cytotoxic T cell in the thymus. In preclinical models Thymotrinan is shown to exert similar immunomodulatory activities to thymopoietin affecting both humoral and cellular responses. In chronic 28-days i.v. toxicity studies in dogs no adverse reaction has been found. The low toxicity of Thymotrinan is probably attributable to their short half-life.