FDA Approves Myfembree to Treat Endometriosis

The approval had been delayed as the regulatory agency reviewed data on Myfembree's impact on bone mineral density.

The FDA has approved Myfembree (relugolix, estradiol, and norethindrone acetate) as a one-pill, once-a-day therapy for the management of moderate-to-severe pain associated with endometriosis. Developed by Myovant Sciences and Pfizer, Myfembree is also approved for the management of heavy menstrual bleeding associated with uterine fibroids in premenopausal women.

“This newly approved option for patients with pain from endometriosis offers the convenience of one pill taken once daily with a mean change in bone mineral density of <1% that did not appear to worsen at 12 months of treatment; however, monitoring is recommended,” Linda Giudice, M.D., Ph.D., distinguished professor at the University of California, San Francisco (UCSF), and chair, SPIRIT Program Steering Committee, said in a press release.

In May 2022, the FDA had extended the review of the supplemental new drug application (sNDA) for the endometriosis indication. Regulators want additional time to review information they had requested from the companies regarding bone mineral density.

Related: FDA Extends Review of sNDA for Myfembree

The approval for the endometriosis indication is supported by one-year efficacy and safety data, including 24-week data from the phase 3 SPIRIT 1 and SPIRIT 2 trials, which were published in The Lancet, and the first 28 weeks of an open-label extension study for eligible women who completed either SPIRIT 1 or SPIRIT 2.

The trials each met their co-primary endpoints with 75% of women in the Myfembree group in both studies achieving a clinically meaningful reduction in dysmenorrhea compared with 27% and 30% of women in the placebo groups at week 24. Adverse reactions occurring in at least 3% of women treated with MYFEMBREE and greater than placebo were: headache, vasomotor symptoms, mood disorders, abnormal uterine bleeding, nausea, toothache, back pain, decreased sexual desire and arousal, arthralgia, fatigue, and dizziness.

The open-label extension study showed mean bone mineral density loss of less than 1% from baseline through one year of treatment; some patients (19.7%) had losses >3%. Annual bone density measurement is recommended while treating women for endometriosis.