A study recently published in the journal Science Translational Medicine revealed two novel therapeutic drugs for endometriosis that do not impair fertility in mice. The study was led by researchers at the University of Illinois at Urbana-Champaign and is entitled “Dual suppression of estrogenic and inflammatory activities for targeting of endometriosis.”

Endometriosis is a gynecological disorder in which the tissue that normally lines the inside of the uterus (called endometrium) grows outside the uterus, usually in the abdominal cavity, where it can form lesions and cysts, scarring organs like the ovaries, bladder and rectum. The tissue, although displaced, still continues to act normally as inside the uterus, so it thickens, breaks down and bleeds with each menstrual cycle. Endometriosis can be a painful disorder, causing inflammation and very heavy periods. It is estimated that 10% of the women in reproductive age suffer from this condition and it can cause infertility in up to 50% of them. The exact causes of this disorder are unknown.

The reduction of estrogen levels in the body is a long-term solution for the disorder as the endometrium tissue requires this hormone for growth and survival. However, estrogen reduction has limited effectiveness and can lead to severe side effects such as menopausal symptoms and infertility. Therefore, women with endometriosis and who want to have children face a problem as they need to treat endometriosis in order to conceive, but the hormonal therapy can make them infertile in turn.

Researchers have now discovered that the estrogen receptors present in the lesions differ from the ones in the normal endometrium. This finding allowed them to design two drug inhibitors specific for estrogen receptors in the lesions — chloroindazole (CLI) and oxabicycloheptene sulfonate (OBHS).

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Using mice models, the team found that both drugs have a strong anti-inflammatory activity, inducing regression of the established endometrial lesions and halting the growth of new lesions. Both CLI and OBHS were also found to decrease pain and none interfered with mice fertility or the health status of the pups. The drugs also restrained endometriosis development in human endometrial tissue taken from cysts of patients.

“We are hopeful that these compounds will prove to be useful for women with this common disease,” said the study’s senior author Dr. Benita Katzenellenbogen in a news release.

The research team concluded that these two new therapeutic drugs represent promising alternatives to surgery or therapies linked to serious side effects in the treatment of endometriosis without affecting fertility.

“It’s fascinating to see the drugs had very little effect on the [normal] endometrial tissue and the pups, but we have to wait to see whether this will hold up in humans,” said Dr. Christian Becker, a consultant gynecologist and endometriosis specialist at the University of Oxford, United Kingdom. “It’s good that this is getting some attention as it affects so many people, but it’s not historically been a cool thing to talk about.”