Emerging and Ongoing Medication Research for Endometriosis

In addition to the current pain management and hormonal therapies on the market, there are several medications in clinical trials being investigated for the potential treatment of endometriosis-related symptoms.


Relugolix is a Gn-RH antagonist in development that functions in a similar manner to elagolix now known by the brand name Orlissa. It quickly reduces the two main circulating gonadotropins in women: luteinizing hormone (LH), and follicle-stimulating hormone (FSH). This results in the suppression of estrogen.

It is an oral once-daily drug designed to inhibit the Gn-RH receptors in the pituitary. Treatment with a Gn-RH antagonist generally results in a temporary increase in hormone level production including estrogen. A potential differentiating factor is the hope that relugolix could decrease the initial rise of hormone levels typically experienced at the beginning of treatment. Gn-RH antagonists work by desensitizing the Gn-RH receptors. Desensitization happens when a receptor gets activated so many times that it eventually stops responding altogether. So, at first, Gn-RH agonists create a surge of these Gn-RH receptor-related hormones as the medication is overloading the receptors, leading the receptors to eventually shut off and the hormone levels drop dramatically. When the initial surge happens though, the symptoms that the medication is trying to alleviate, such as pelvic pain, may increase.

Myovant Sciences is continuing Phase 3 of the SPIRIT 2 clinical trials of relugolix hoping to differentiate it from other available treatments by preventing the initial flare stage. Relugolix is also in clinical trials as a treatment for uterine fibroids and prostate cancer.1-4


Linzagolix, formerly known as OBE2109, is an experimental oral medication manufactured by ObsEva for the purpose of easing the symptoms and pain associated with endometriosis and uterine fibroids. The Kissei Pharmaceutical Company originally developed the drug.
Like Orlissa and relugolix, it is a Gn-RH antagonist. It works by blocking the action of GnRH on the pituitary gland binding to its receptors thereby preventing GnRH from activating hormone development. This causes a reduction in follicle stimulating hormone (FSH) and luteinizing hormone (LH), which results in lowers estrogen levels.

Linzagolix is also striving to reduce the initial hormonal surge experienced at the beginning of treatment. Researchers are investigating the effectiveness of linzagolix at both low and high doses. If results are favorable, dosing can be tailored to individual needs. This could impact the side effects experienced, and reduce the need for an add-back therapy typically seen in Gn-RH agonists. Add-back therapy is a supplementary dose of either estrogen or progesterone to reduce side effects, particularly bone loss and cholesterol levels.

There are currently two Phase 3, randomized, double-blind, and placebo-controlled studies investigating linzagolix before it is considered for FDA approval.5-6

Aromatase inhibitors

Aromatase inhibitors decrease levels of estrogen in the body, and are indicated for use by women with some forms of breast cancer who are also post-menopausal. Some providers have begun prescribing aromatase inhibitors off-label for endometriosis (meaning for a purpose other than what they are intended for use for). Data on their effectiveness in relieving endometriosis-related symptoms is not robust at this time; however, more studies are ongoing to determine if endometriosis should be added to the list of indications for aromatase inhibitors. Aromatase inhibitors are FDA approved for the treatment of certain conditions, but clinical trials are required to get approval for expand use beyond any existing indications.7-8

This is not an exhaustive list of all investigational medications for endometriosis. Consult your healthcare provider about the availability of any appropriate new medications as well as any available clinical trials in your area that might be appropriate should you be interested.

Written by: Casey Hribar | Last reviewed: February 2019
View References
  1. SPIRIT 2: Efficacy and Safety of Relugolix in Women with Endometriosis-Associated Pain. National Institutes of Health: U.S. National Library of Medicine. ClinicalTrials.gov. https://clinicaltrials.gov/ct2/show/NCT03204331?recrs=ad&cond=endometriosis&phase=2&rank=5. Updated April 3, 2018. Accessed May 1, 2018.
  2. Relugolix. Available at: https://endometriosisnews.com/relugolix/. Accessed 2.26.19
  3. SPIRIT 2: Efficacy and Safety Study of Relugolix in Women With Endometriosis-Associated Pain. Available at: https://www.centerwatch.com/clinical-trials/listings/121654/endometriosis-related-pain-spirit-2-efficacy-safety/. Accessed 2.27.19
  4. How It Works. Available at: http://myovant.com/relugolix. Accessed 2.27.19
  5. Linzagolix. Available at: http://www.obseva.com/pipeline/obe2109. Acccessed 2.26.19
  6. Linzagolix (OBE2109). Available at: https://endometriosisnews.com/obe2109/. Accessed 2.27.19
  7. Endometriosis: Should I Use Hormone Therapy? Michigan Medicine: University of Michigan. https://www.uofmhealth.org/health-library/tv7240. Published October 6, 2017. Accessed May 1, 2018.
  8. Bulun S, Wood R. Aromatase in Endometriosis. Endometriosis.org. http://endometriosis.org/resources/articles/aromatase/. Accessed May 1, 2018.