SPRAY-DRIED ENTERIC SOLID DISPERSION AS A NOVEL ORAL DELIVERY SYSTEM FOR A PENTAPEPTIDE ANALOG OF THYMOPENTIN

IRI-426 (Ac-Arg-Pro-Asp-Val-Phe-NH2) is a biologically active and enzyme-resistant analog of thymopentin (Arg-Lys-Asp-Val-Tyr), a pentapeptide corresponding to an active site of the thymic hormone thymopoietin. Enteric formulation of this enzyme resistant pentapeptide could be valuable for oral administration by providing protection from acid proteolysis in the gastric juice and release and absorption in the duodenum. Using a drug-to-polymer ratio of 1 to 10, an enteric solid dispersion of IRI-426 was prepared with an acid-insoluble, pH-sensitive polymer Eudragit S-100, by the spray-drying technique. The USP rotating paddle method (apparatus II) was used to evaluate drug release as a function of pH. In vitro release profiles revealed that the spray-dried enteric solid dispersion powder exhibited rapid release at pH 7 and retarded release at pH 1.2.