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BACKGROUNDUterine fibroids are a common cause of heavy menstrual bleeding and pain. Treatment with the combination of relugolix (an oral gonadotropin-releasing hormonereceptor antagonist), estradiol, and norethindrone acetate, administered once daily, may have efficacy in women with uterine fibroids and heavy bleeding while avoiding hypoestrogenic effects. METHODSWe conducted two replicate international, double-blind, 24-week, phase 3 trials involving women with fibroid-associated heavy menstrual bleeding. Participants were randomly assigned in a 1:1:1 ratio to receive once-daily placebo, relugolix combination therapy (40 mg of relugolix, 1 mg of estradiol, and 0.5 mg of norethindrone acetate), or delayed relugolix combination therapy (40 mg of relugolix monotherapy, followed by relugolix combination therapy, each for 12 weeks). The primary efficacy end point in each trial was the percentage of participants with a response (volume of menstrual blood loss <80 ml and a ≥50% reduction in volume from baseline) in the relugolix combination therapy group, as compared with the placebo group. Key secondary end points were amenorrhea, volume of menstrual blood loss, distress from bleeding and pelvic discomfort, anemia, pain, fibroid volume, and uterine volume. Safety and bone mineral density were assessed. RESULTSA total of 388 women in trial L1 and 382 in trial L2 underwent randomization. A total of 73% of the participants in the relugolix combination therapy group in trial L1 and 71% of those in trial L2 had a response (primary end point), as compared with 19% and 15%, respectively, of those in the placebo groups (P<0.001 for both comparisons). Both relugolix combination therapy groups had significant improvements, as compared with the placebo groups, in six of seven key secondary end points, including measures of menstrual blood loss (including amenorrhea), pain, distress from bleeding and pelvic discomfort, anemia, and uterine volume, but not fibroid volume. The incidence of adverse events was similar with relugolix combination therapy and placebo. Bone mineral density was similar with relugolix combination therapy and placebo but decreased with relugolix monotherapy. CONCLUSIONSOnce-daily relugolix combination therapy resulted in a significant reduction in menstrual bleeding, as compared with placebo, and preserved bone mineral density in women with uterine fibroids. (Funded by Myovant Sciences; LIBERTY 1 [L1] and LIB-ERTY 2 [L2] ClinicalTrials.gov numbers, NCT03049735 and NCT03103087, respectively.