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If you have endometriosis, then you probably know that medical treatments rarely result in a permanent cure. You can receive hormonal treatments to suppress ovulation, but they may be associated with adverse side effects.

The good news is that as researchers learn more about the underlying mechanism of endometriosis and realize that it is not just a disease related to hormones and the reproductive system, but one that is also likely related to the immune system, then potential new treatments can be identified.

Here are a few that are under investigation, though none of these has yet been approved for treatment of endometriosis by the U.S. Food and Drug Administration.

• Aromatase inhibitors. These medications—letrozole (Femara), anastrozole (Arimidex) and exemestane (Aromasin)—are used to treat breast cancer and prevent a recurrence. They work by interfering with the ability of the aromatase enzyme to transform androgen hormones into estrogen. So they may be an ideal treatment for an estrogen-related condition like endometriosis. A review of eight published studies involving 137 women with endometriosis found the medications helped reduce the chronic pain of endometriosis. In some studies, the aromatase inhibitor was combined with other traditional treatments for endometriosis, such as oral contraceptives, progestogens or gonadotrophin-releasing hormone (GnRH) agonists. The combination is an effort to decrease the incidence of hot flashes and bone loss, both of which may be side effects of aromatase inhibitors. In women who have been treated for breast cancer, aromatase inhibitors may also increase the risk of blood clot formation. As the authors noted, larger clinical studies are needed.

• Selective progesterone receptor modulators (SPRMs). These investigational medications work by preventing the action of progesterone in certain tissues, like uterine tissue, while allowing it in others, like bone. The compounds farthest along in development are asoprisnil and Proellex. Studies with asoprisnil find it helps reduce endometriosis-related pain as well as heavy bleeding. A six-month study of Proellex in 39 premenopausal women with endometriosis compared it to the GnRH agonist leuprolide (Lupron). This unpublished study found Proellex reduced the duration and intensity of pain faster and better than Lupron, with no evidence of the bone loss seen with Lupron.

• Anti-angiogenic medications. These medications, which include bevacizumab (Avastin), were initially developed for cancer treatment. They work by blocking blood vessel formation that would theoretically prevent tumor or endometriosis growth by limiting blood supply. Animal studies show these compounds, particularly endostatin, effectively reduced the number of newly developed blood vessels around the endometrial lesions, as well as interfering with their growth and development.

• GnRh antagonists. Like GnRh agonists, these medications work to suppress the activity of gonadotrophin-releasing hormone, which, down the line, triggers production of estrogen. So far, clinical trials are ongoing with cetrorelix (Cetrotide), which is administered as a daily or weekly injection.

These are just a few of the many options being examined but not yet approved for treatment of endometriosis in the United States. Others include terbutaline, a drug used to prevent premature birth but which may have benefits for reducing endometriosis-related pain; mifepristone, the so-called "abortion" drug, which prevents the action of progesterone in certain tissues; a vaginal form of danazol (Danocrine), a male hormone that suppresses ovulation and which is sometimes used in pill form to treat endometriosis; and even a vaccine designed to trigger the immune system to destroy endometrial lesions.

If you're interested in volunteering for a clinical trial on new medical options for endometriosis, go to www.clinicaltrials.gov and type "endometriosis" into the search box.

References

Patwardhan S, Nawathe A, Yates D, Harrison GR, Khan KS. Systematic review of the effects of aromatase inhibitors on pain associated with endometriosis. BJOG. 2008;115(7):818-822.

Repros reports that Proellex has demonstrated superior efficacy and safety in endometriosis when compared to standard of drug care [press release]. June 11, 2007. Available at: http://www.drugs.com. Accessed July 5, 2008.

Becker CM, Sampson DA, Rupnick MA, et al. Endostatin inhibits the growth of endometriotic lesions but does not affect fertility. Fertility and Sterility. 2005;84:1144-1155.

Produced with financial support from TAP Pharmaceutical Products Inc.

Create Date: 7/23/2008
Last Date Updated: 7/23/2008