Thymopentin is a synthetic pentapeptide which is the active site of the naturally occurring hormone thymopoietin with immunomodulating properties. Thymopentin can specifically promote the differentiation and maturation of thymic T cells and natural killer cells (NK) and enhance the function of T helper cells. thymic can achieve a two-way adjustment to the immune system by increasing the levels of intracellular cyclic adenosine monophosphate, elevating the activity of T cells, and regulating the proportions of T cell subsets. As an immunomodulating agent, Thymopentin is clinically used in the treatments of autoimmune diseases, such as e.g. atopic dermatitis, chronic lymphocytic leukemia, Sezary's syndrome, rheumatoid arthritis, as well as decreased immune competency in elder surgical patients. Due to poor membrane permeability, extensive metabolism in the GI, and extremely short half-life of 30 s, repeated injections or i.v infusions of Thymopentin are necessary which greatly restrict its clinical applications.