Endometriosis is a condition in which the endometrium, or tissues lining the uterus, grow outside the uterus, usually in the abdomen. The implanted tissue swells and sheds during the menstrual cycle, just as the lining of the uterus does. However, because these tissues are not in the uterus, they cannot be expelled as normal during a woman’s monthly cycle, leading to pain and inflammation, as well as the possibility of infertility.

There is currently no cure for endometriosis. However, there are several treatments aimed at reducing pain and inflammation. Surgery, to remove endometrial tissue, is also an option in some cases.

Several experimental therapies are also under development.

These experimental therapies aim to reduce pain and inflammation caused by endometriosis. They are designed to induce an artificial menopause, so as to halt menstruation by reducing the amount of estrogen secreted by the body.

Gonadotropin-releasing hormone (GnRH) agonists and antagonists act on a receptor in the pituitary gland, a region in the brain that is sometimes called the “master gland.” By interacting with this receptor, these treatments may prevent the secretion of estrogen, thereby reducing or suppressing the menstrual cycle.

Orilissa (elagolix), an oral medication developed by Neurocrine Biosciences and AbbVie, is a GnRH receptor antagonist that was approved by the U.S. Food and Drug Administration in July 2018 to treat moderate to severe pain in endometriosis. Orilissa reduces the amount of estrogen secreted by the body, which reduces inflammation and pain associated with the shedding of endometrial tissue.

Two GnRH receptor-targeting treatments in being tested in patients are detailed below.


Linzagolix (formerly OBE2109) is an experimental treatment created by Kissei Pharmaceutical, now owned by ObsEva. A Phase 2 clinical trial (NCT02778399) is currently testing the efficacy and safety of oral Linzagolix in treating pain in about 330 patients with endometriosis. This placebo-controlled study, called EDELWEISS, is due to finish in July 2019.

ObsEva is also sponsoring two Phase 3 clinical trials (NCT03070899 and NCT03070951) in patients with heavy menstrual bleeding due to uterine fibroids; the primary goal of both trials — which are recruiting hundreds of patients — is reduced fibroid-associated bleeding in those treated with Linzagolix, alone and in combination with add-back therapy. More information on these trials is available by clicking on their NCT numbers.


Relugolix is an experimental treatment being developed and tested by Myovant Sciences to reduce the pain associated with endometriosis. An oral once-daily treatment, it is also intended to treat pain due to uterine fibroids as well as hormone-sensitive prostate cancer (HSPC).

Myovant is currently recruiting patients in the U.S., the EU, Canada, and Australia for Phase 3 clinical trials (NCT03204318 and NCT03204331). Patients will receive either Relugolix or placebo to evaluate efficacy in treating endometriosis-associated pain. Both trials are due to end in 2020, and more information is available by clicking on their NCT numbers.


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