Myovant Sciences and Pfizer have received the US Food and Drug Administration (FDA) approval for Myfembree to manage the pain associated with endometriosis.

Myfembree is a combination of relugolix, estradiol, and norethindrone acetate, indicated as a once-daily therapy for managing endometriosis-related pain in pre-menopausal women.

Relugolix reduces oestrogen and other hormones produced by ovaries, estradiol reduces the risk of bone loss, and norethindrone acetate is a progestin, a synthetic progestogen.

The drug is already approved in the US for managing heavy menstrual bleeding related to uterine fibroids in premenopausal women.

Myovant Sciences chief medical officer Juan Camilo Arjona Ferreira said: “The new Myfembree indication helps advance our mission to redefine care for women by helping address a disease with high unmet need, giving women and physicians a new meaningful treatment option to manage moderate to severe pain associated with endometriosis.”

Pfizer internal medicine and hospital chief development officer and global product development SVP James Rusnak said: “This approval is an important milestone reflecting Pfizer and Myovant’s commitment to women’s health in areas of significant unmet need.

“We look forward to making MYFEMBREE available to women with endometriosis and broadening their options in managing this complex disorder.”

The US FDA approval is based on one-year efficacy and safety data, including 24-week data from the Phase 3 SPIRIT 1 and SPIRIT 2 studies, along with 28-week data from an open-label extension study.

In the clinical trials, Myfembree reduced menstrual pain and non-menstrual pelvic pain with a loss of mean bone mineral density of less than 1% from baseline through one year.

Both studies met their co-primary endpoints with 75% of women achieving a clinically meaningful reduction in dysmenorrhea, compared to 27% and 30% with the placebo.

Treatment with Myfembree showed a clinically meaningful non-menstrual pelvic pain relief in 59% and 66% of women, compared with 40% and 43% with the placebo, said Pfizer.

Headache, vasomotor, mood disorders, abnormal uterine bleeding, nausea, toothache, back pain, decreased sexual desire, arthralgia, fatigue, and dizziness include adverse reactions.

SPIRIT Program steering committee chair Linda Giudice said: “The data from the SPIRIT studies showed the clinical benefit that relugolix combination therapy can have on moderate to severe pain associated with endometriosis and how it can impact patients.

“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.”