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This article is the author’s final published version in Obstetrics and gynecology, Volume 135, Issue 6, June 2020, Pages 1313-1326.

The published version is available at Copyright © Simon et al.


Objective: To investigate the safety and efficacy of elagolix, an oral gonadotropin-releasing hormone antagonist, with hormonal add-back therapy for up to 12 months in women with heavy menstrual bleeding associated with uterine leiomyomas.

Methods: Elaris UF-EXTEND was a phase 3 extension study that evaluated an additional 6 months (up to 12 months total) of elagolix 300 mg twice daily with hormonal add-back therapy (estradiol 1 mg and norethindrone acetate 0.5 mg once daily) in women who completed an initial 6 months of the same treatment in one of two preceding phase 3 studies. The primary endpoint was the percentage of women with both less than 80 mL menstrual blood loss during final month and a 50% or greater reduction in menstrual blood loss from baseline to final month. Safety evaluations included adverse events and bone mineral density changes. The planned sample size of UF-EXTEND was based on estimated rollover and discontinuation rates in the two preceding studies.

Results: From September 2016 to March 2019, 433 women were enrolled in UF-EXTEND. Of these women, 218 received up to 12 months of elagolix with add-back therapy; the mean±SD age of this group was 42.4±5.4 years and 67.3% were black. The percentage of women who met the primary endpoint in this elagolix with add-back group was 87.9% (95% CI [83.4-92.3]). The most frequently reported adverse events with up to 12 months of elagolix plus add-back therapy were hot flush (6.9%), night sweats (3.2%), headache (5.5%), and nausea (4.1%). Mean percent decreases in bone mineral density from baseline to extension month 6 were significantly less with elagolix plus add-back therapy than with elagolix alone {between-group difference in lumbar spine: -3.3 (95% CI [-4.1 to -2.5])}.

Conclusion: Up to 12 months of elagolix with add-back therapy provided sustained reduction in menstrual blood loss in women with uterine leiomyomas, with the addition of add-back therapy attenuating the hypoestrogenic effects of elagolix alone. No new or unexpected safety concerns were associated with an additional 6 months of elagolix with addback therapy.

Clinical trial registration:, NCT02925494.

Funding source: AbbVie Inc funded this study.

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