Emerging and Ongoing Medication Research for Endometriosis

In addition to the current pain medications and hormonal therapies on the market, there are several other medications under investigation for the potential treatment of endometriosis-related symptoms. Several of these include the following. Although some of these options have promising preliminary research, they are not yet approved by the U.S. Food and Drug Administration for use in America.


Relugolix is another Gn-RH agonist that functions in a similar manner to Elagolix, however, Relugolix may potentially decrease the initial flare of hormones at the beginning of treatment. Normally, when treatment with a Gn-RH agonist starts, there is an increase in the hormones, including estrogen, that these medications are trying to suppress. This happens because Gn-RH agonists attempt to desensitize 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.

The makers of Relugolix, Myovant Sciences, are trying to demonstrate that this medication is different than others by preventing this flare stage.2 As of mid-2018, the main Relugolix clinical trial, SPIRIT 2, was a Phase 3 trial, which is the last phase of trial a new medication can be in. The SPIRIT 2 trial is enrolling 600 participants and is expected to be completed by June 2020, when it may potentially be approved for the market by the U.S. FDA.3


OBE2109 is an investigational medication manufactured by ObsEva and Kissei Pharmaceutical Company. Like Elagolix and Relugolix, it is another Gn-RH agonist. Like Relugolix, OBE2109 may potentially reduce the hormonal surge at the beginning of treatment. In addition to this, the manufacturers of OBE2109 also claim that it may help prevent bone mineral density loss, which is a serious side effect of the currently available Gn-RH agonists. This property is also a contributing factor to why Gn-RH agonists can only be prescribed for only short-term use. In the U.S., clinical trials on OBE2109 are currently underway at the Phase 2 stage (the second to last stage in the clinical trial pipeline). These will help determine the validity of the manufacturers statements and assess the safety and efficacy of OBE2109. As of mid-2018, the study’s anticipated completion date was July 2019, when it may potentially be approved by the U.S. FDA.4,5

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. Although aromatase inhibitors are already approved by the U.S. FDA for the treatment of other conditions, clinical trials need to be completed to expand any medication’s indicated uses.6-8

This is not an exhaustive list of all investigational medications for endometriosis. Consult your healthcare provider about any new medications that you may be eligible for, as well as any clinical trials you might qualify for (if you are interested in clinical trials).

Written by: Casey Hribar | Last reviewed: June 2018
View References
  1. Relugolix: How it Works. Myovant Sciences. http://myovant.com/relugolix/. Accessed May 1, 2018.
  2. 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.
  3. Product Information: OBE2109. ObsEva. http://www.obseva.com/pipeline/obe2109#obe2109-endometriosis. Accessed May 1, 2018.
  4. A Study to Assess the Efficacy and Safety of OBE2109 in Subjects with Endometriosis (EDELWEISS). National Institutes of Health: U.S. National Library of Medicine. ClinicalTrials.gov. https://clinicaltrials.gov/ct2/show/NCT02778399?recrs=ad&cond=endometriosis&phase=1&rank=1. Updated January 24, 2018. Accessed May 1, 2018.
  5. What are the Treatments for Endometriosis? National Institutes of Health: Eunice Kennedy Shriver National Institute of Child Health and Human Development. https://www.nichd.nih.gov/health/topics/endometri/conditioninfo/treatment. Published January 31, 2017. Accessed May 1, 2018.
  6. 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.
  7. Bulun S, Wood R. Aromatase in Endometriosis. Endometriosis.org. http://endometriosis.org/resources/articles/aromatase/. Accessed May 1, 2018.