Last week the Food and Drug Administration approved an important new drug for use in the U.S. You may be wondering, "just what is this RU486?"


RU486 is an anti-progesterone drug, in the same way that tamoxifen is an anti-estrogen substance. Both work by attaching to the cells' receptors for the specific hormone and thus interfering with that hormone's action. Many people know someone who has used tamoxifen after surgery for breast cancer of the type that is stimulated by estrogen.


Progesterone is a female sex hormone that is produced by the empty ovarian follicle after ovulation in the second half of the normal menstrual cycle. As its name implies, it is "pro"-gestational, that is it stimulates the growth of the uterine lining for the attachment of the ovum. If the ovum is not fertilized or not attached, it is shed along with the extra uterine lining, producing a normal menstrual period. However, if implantation of the fertilized ovum does occur, the progesterone production increases and is later taken over by the placenta.


RU486 was developed by a French physician-biochemist, Etienne-Emile Baulieu, who had been studying steroid hormones and their receptors, particularly the progesterone receptor, seeking new approaches to fertility control. The goal was to find a compound similar enough to progesterone to bind to its receptor, but different enough that it would have anti-progesterone activity. Drug development is a team effort, and early in the process the chemists at the drug company Roussel were involved. Many years and many tests later the compound RU486 was ready for testing in animals, and finally in the l980's in humans. It proved to be remarkably effective and safe


The drug was first licensed in France in 1989, and since then it has provided early and safe abortions in many women. However, there are other potential uses as well. Some breast cancers that have become resistant to anti-estrogen treatment may respond with the addition of an anti-progesterone agent. Interestingly, meningioma a type of brain tumor, has progesterone receptors and may shrink with the use of this drug. Anti-progesterone compounds may also have a future as contraceptive agents with fewer side effects than the estrogen containing birth-control pills.


Although this non-surgical method of pregnancy termination is indeed safe and effective, it still requires medical supervision. However, resort to surgery is rarely required, so it is a boon to the less-developed countries where the alternative might be dangerous and unskilled back street abortion.


Whatever the final role of RU486, the recent FDA approval opens the door to productive study and research on its actions and usage.


Mary Frantz, MD

October 2, 2000