Nestorone(TM) progestin - The ideal progestin for use in controlled release delivery systems

The progestin, 16-methylene-17 alpha-acetoxy-19-norpregn-4-ene-3,20-dione (formerly ST 1435: currently designated Nestorone(TM) progestin), was developed as a potential oral contraceptive. Studies in rodents and primates demonstrated that this agent had very little progestational activity when administered orally at 5-10 mg. By contrast, 5-10 mu g were highly active when administered intramuscularly or subcutaneously to the same animals. In a number of bioassays, Nestorone(TM) progestin was 10-100 times more potent than progesterone administered by the same route. The high potency of this progestin suggested that it might be used for development for parenteral rather than oral dosage forms. Because E. Merck was primarily interested in orally active progestins, the Population Council and its clinical investigators were encouraged to develop sustained release drug delivery systems for this steroid. The present report outlines the status of this development program.