Vilaprisan (BAY1002670) is a therapy being developed by Bayer HealthCare Pharmaceuticals to treat endometriosis and uterine fibroids.

Endometriosis affects up to 10 percent of women of reproductive age worldwide. It is characterized by abnormal tissue growth covering the inside of the uterus. This leads to the formation of endometriotic lesions. Symptoms include inflammation and recurring pelvic pain, which can be chronic or occur during menstruation. Endometriosis causes infertility in about half of patients. Its cause is unknown but it is likely the result of several factors. No cure exists for this condition, but it can be managed with pain relief and the surgical removal of lesions.

How vilaprisan works

Hormonal imbalance observed in women with endometriosis is a potential target for treating endometriosis. Vilaprisan is a highly selective steroidal progesterone receptor modulator (SPRM). It is a partial agonist of progesterone receptor, which means that the drug activates progesterone receptors to a certain degree upon binding. This triggers a cascade of biochemical reactions that result in the suppression of prostaglandin production. This, in turn, relieves symptoms such as pain and bleeding. Modulating progesterone by taking vilaprisan might help in treating endometriosis over the long term.

Vilaprisan in clinical trials

The results of a randomized, placebo-controlled Phase 1 study of healthy post-menopausal women showed that vilaprisan is well tolerated. A phase 1 trial (NCT02262663)  in healthy young women of reproductive age produced similar results.

The drug was also investigated in a non-randomized, non-blinded and non-placebo-controlled Phase 1 clinical trial (NCT02975440) aimed at studying the interaction between vilaprisan and Rifadin (rifampicin), another drug potentially useful to treat endometriosis. Researchers completed this study on a group of 12 healthy post-menopausal women in June 2017.

Vilaprisan is being studied for safety and efficacy in several trials of patients with uterine fibroids. For example, a Phase 2 trial (NCT02465814) compared the drug to placebo in 120 women with uterine fibroids, and a Phase 3 trial (NCT03194646) called ASTEROID 6 is now recruiting participants. The promising results reported from these studies are likely to spark similar studies on women with endometriosis.


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