ABSTRACT
Since the discovery of the first progesterone antagonist, RU 486 (mifepristone), by the scientists of Roussel-Uclaf (Philibert et al., 1982), considerable progress has been made in the development of PR ligands as well as in elucidating their molecular mechanisms of action. Novel compounds capable of either blocking (progesterone antagonists, antiprogestins) or modulating SPRMs the transcriptional activity of the PR are now available for clinical studies. The SPRMs exhibit mixed agonistic/ antagonistic activity at
PR and may exert tissue-specific effects (Elger et al., 2000). These developments suggest new and exciting clinical applications in gynecological therapy, contraception and HRT, and are useful, non-invasive pharmacological tools to study progesterone action in various tissues of the reproductive tract. The availability of specific and potent progesterone antagonists and SPRMs makes it possible to study progesterone action in the primate endometrium, and for the first time also during pregnancy in species exhibiting placental progesterone synthesis.
