RU 486: The Progesterone Antagonist

The objective of this report is to review the current and potential therapeutic uses of the progesterone antagonist drug RU 486 (mifepristone). Publications cited in peer-reviewed journals were identified through a search of the Index Medicus from 1987 through 1992. A wide range of research reports was reviewed, including human, animal, and tissue culture experiments. Data from published reports were included in this report if they addressed the mechanism of action, clinical indications, and potential uses for RU 486. The review disclosed that as a progesterone antagonist, RU 486 is clinically effective for inducing first-trimester abortions, for ripening and dilating the cervix to facilitate intrauterine surgical procedures, and as a postcoital contragestational agent. As a glucocorticoid antagonist, RU 486 is useful for treating inoperable cases of nonpituitary Cushing's syndrome. RU 486 is under investigation for use as an antineoplastic agent; it has shown promise as a treatment of meningioma, breast cancer, prostate cancer, and hepatoma. RU 486 may also have a role in the treatment of endocrinologic conditions such as endometriosis and premenstrual syndrome. I conclude that RU 486 is effective and in current clinical use for a number of reproductive indications and for treatment of Cushing's syndrome. The drug also has potential as therapy for certain neoplasms and endocrinologic conditions.