GnRH antagonist combination therapy
Two daily oral medicines, Myfembree and Oriahnn, are FDA-approved to treat heavy menstrual bleeding caused by uterine fibroids in premenopausal people. They work well but carry important safety limits.
How they work
Each combines a GnRH antagonist with low doses of hormones. The antagonist, relugolix in Myfembree and elagolix in Oriahnn, blocks signals from the pituitary gland to the ovaries. That lowers estrogen and progesterone and sharply reduces bleeding. The added estradiol, an estrogen identical to the body’s own, and norethindrone acetate, a progestin, are called add-back therapy. They reduce side effects of low estrogen such as bone loss and hot flashes, and the progestin protects the uterine lining.
How well they work
In the two main Myfembree trials, about 7 in 10 participants met the goal of much lighter bleeding at six months, compared with fewer than 2 in 10 on placebo. Bleeding usually returns after stopping.
What they do not do
These medicines treat bleeding. They do not meaningfully shrink fibroids and do not cure them. For fibroids, the FDA-approved use is heavy menstrual bleeding. Myfembree has a separate approval for endometriosis pain.
Important safety information
- Both carry a boxed warning for blood clots and vascular events such as stroke and heart attack. They are not for people at high risk of these, including people over 35 who smoke.
- Use is limited to 24 months because of bone density loss.
- They are not for people with osteoporosis, known or suspected breast or other hormone-sensitive cancer, significant liver disease, or abnormal bleeding that has not been evaluated.
- They can make pregnancy harder to recognize. Use non-hormonal contraception as directed while taking them.
- Mood changes, including depression, have been reported.
This is not the complete safety information. Read the prescribing information and discuss your history with your physician.
Sources
- MYFEMBREE (relugolix, estradiol, and norethindrone acetate) tablets. U.S. Prescribing Information. Current version.
- ORIAHNN (elagolix, estradiol, and norethindrone acetate capsules; elagolix capsules). U.S. Prescribing Information. Current version.
- Al-Hendy A, Lukes AS, Poindexter AN, et al. Treatment of uterine fibroid symptoms with relugolix combination therapy. N Engl J Med. 2021;384(7):630–642.
- American College of Obstetricians and Gynecologists. Practice Bulletin No. 228: Management of symptomatic uterine leiomyomas. Obstet Gynecol. 2021;137(6):e100–e115.