Mifepristone: Reflections on its Early Clinical Development for Medical Abortion.

Mifepristone (RU-486), the first clinically effective progesterone antagonist, was initially identified as having antiglucocorticoid activity. Although early interest focused on its role as a glucocorticoid receptor antagonist, recognition of its antiprogesterone effects led to studies of its role in pregnancy termination. This article reviews the steps leading to its use as an abortifacient, from its initial identification for this indication and draws on the author's direct involvement in the field with reflections on his contribution to the early clinical development of mifepristone. These studies established the efficacy of mifepristone in pregnancy termination. Unfortunately, its wider therapeutic applications have received limited attention.