What is the therapeutic effect of myfembree

Once-daily combined therapy with myfembree (an oral gonadotropin-releasing hormone receptor antagonist), estradiol, and norethindrone acetate may be effective in women with uterine fibroids and heavy bleeding while avoiding hypoestrogenic effects.

The study was conducted in two replicated international, double-blind, 24-week, Phase 3 trials (NCT03049735 and NCT03103087) involving women with fibroid-related heavy menstrual bleeding. Participants were randomly assigned in a 1:1:1 ratio to receive once-daily placebo, myfembree combination therapy (40 mg myfembree, 1 mg estradiol, and 0.5 mg norethindrone acetate) or delayed myfembree combination therapy (40 mg myfembree monotherapy followed by myfembree combination therapy for 12 weeks each).

Key secondary endpoints for each trial were amenorrhea, menstrual blood loss, anemia due to bleeding and pelvic discomfort, pain, distress, fibroid volume and uterine volume. Safety and bone density were assessed. The primary efficacy endpoint was the percentage of participants with a response (menstrual blood loss <80 ml and a ≥50% reduction from baseline) in the combination treatment group compared with the placebo group.

Results: A total of 388 women in trial L1 and 382 women in trial L2 underwent randomization. A total of 73% of participants in the myfembree combination treatment group in trial L1 and 71% of participants in trial L2 responded (the primary endpoint), compared with 19% and 15%, respectively, in the placebo group (<0.001 for both comparisons). The myfembree combination treatment group showed significant improvements compared with placebo in six of seven key secondary endpoints, including menstrual blood loss (including amenorrhea), pain, pain from bleeding and pelvic discomfort, anemia and uterine volume, but not fibroid volume.

Incidence rates were similar between myfembree combination treatment and placebo. Bone mineral density was similar in the myfembree combination treatment and placebo groups, but bone mineral density was reduced in the myfembree monotherapy group.

Conclusions: Once-daily myfembree combination therapy significantly reduced menstrual bleeding and preserved bone density in women with uterine fibroids compared with placebo.

Myfembree is the first once-daily drug to treat uterine fibroid-related menorrhagia (HMB) in premenopausal women. Treatment lasts for up to 24 months. It was developed by Pfizer and requires only one oral tablet per day to treat. The therapeutic effect of myfembree is remarkable. It is recommended that patients take medication under the guidance of a doctor and receive symptomatic treatment.

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References

Al-Hendy A, Lukes AS, Poindexter AN 3rd, Venturella R, Villarroel C, Critchley HOD, Li Y, McKain L, Arjona Ferreira JC, Langenberg AGM, Wagman RB, Stewart EA. Treatment of Uterine Fibroid Symptoms with Relugolix Combination Therapy. N Engl J Med. 2021 Feb 18;384(7):630-642. doi: 10.1056/NEJMoa2008283. PMID: 33596357; PMCID: PMC8262231.