Myovant and Pfizer’s relugolix combination tablet, MyFembree, has finally received approval from the US Food and Drug Administration (FDA) for the management of moderate to severe endometriosis. The fixed-dose combination product contains estradiol, norethindrone acetate and relugolix, and is currently used to control heavy menstrual bleeding associated with uterine fibroids.

Myovant and Pfizer have been awaiting the approval of MyFembree’s use in endometriosis patients, but the review process was delayed in April this year due to undisclosed concerns pertaining to the pharma giants’ drug application. However, they are now moving forward with the launch of MyFembree for use in endometriosis and anticipate a drug rollout this month. GlobalData expects MyFembree to be successful in the endometriosis space given its strong clinical trial readouts, once-daily administration, and high potential for market penetration after a disappointing and slow uptake of AbbVie’s Orilissa (elagolix) upon its 2018 market launch.

MyFembree is a once-daily therapy that can be used for up to 24 months to manage moderate to severe endometriosis, a condition in which endometrial-like tissue is found outside of the uterus, resulting in menstrual irregularities, chronic pelvic pain, infertility, pain during sexual intercourse, and pain during the menstrual period. Due to the heterogeneity of the clinical manifestations among different cases, women may wait an average of seven to eight years before receiving a proper diagnosis. An official diagnosis can only be made via a surgical procedure called a laparoscopy.

Most current therapeutic options interfere with a patient’s ability to conceive and may produce negative side effects such as hot flashes and bone mineral density (BMD) loss. Gonadotropin-releasing hormone (GnRH) antagonists are a relatively new class of medication that promises higher rates of efficacy and less BMD loss compared with GnRH agonists. MyFembree would be the second GnRH antagonist to enter the US market after Orilissa, which was launched in 2018.

MyFembree has shown promising efficacy and safety results from the Phase III SPIRIT 1 and SPIRIT 2 trials. In the SPIRIT 1 trial, among women receiving MyFembree, there were pain reductions for 74.5% of women with dysmenorrhoea and 58.5% of women with non-menstrual pelvic pain, compared with 26.9% and 39.6%, respectively, in the placebo group. In SPIRIT 2, 75.2% of women in the MyFembree group experienced clinically meaningful reductions in dysmenorrhoea, compared with 30.4% of women in the placebo group.

Kissei Pharmaceuticals’ Yselty (linzagolix) is another GnRH antagonist undergoing clinical development for the treatment of endometriosis. Yselty would be a third-to-market entrant behind MyFembree and Orilissa, giving the therapeutic a competitive disadvantage.

Based on GlobalData’s Endometriosis Global Drug Forecast and Market Analysis to 2030 report, MyFembree is anticipated to generate nearly $584m in sales in the US alone by 2030. When interviewed for the market analysis report, GlobalData key opinion leaders (KOLs) were optimistic about the potential for MyFembree to penetrate the endometriosis market, with one noting:

“The big pro is that it is once a day, it has a long half-life, and it lasts forever. But that requires that you give full suppression, [so] it’s hard to titrate it…Not everyone needs full suppression. So I think for those who want a one-size-fits-all, keep it simple [drug], they’ll like it because you don’t have to think about adjusting the dose and it’s very simple.”

Having MyFembree as a therapeutic option would provide endometriosis patients with options for managing their pelvic pain, as the current market landscape is dominated by genericised therapeutics that are ineffective in combatting endometriosis.