Efficacy and safety of elagolix with add-back therapy in women with uterine fibroids and coexisting adenomyosis.

Objective: To determine if coexisting adenomyosis limits the efficacy of elagolix, an oral gonadotropin-releasing hormone antagonist, with hormonal add-back therapy in reducing heavy menstrual bleeding in women with uterine fibroids.

Design: Pooled analysis of two identical, double-blind, randomized, placebo-controlled, 6-month phase 3 trials (Elaris Uterine Fibroids [UF]-1 and UF-2).

Setting: A total of 153 gynecological clinical care settings in the United States and Canada.

Patients: Premenopausal women (18-51 years) with >80 mL of menstrual blood loss (MBL)/cycle and uterine fibroids with and without coexisting adenomyosis diagnosed by ultrasound and/or magnetic resonance imaging at baseline.

Interventions: Participants were randomized 1:1:2 to placebo, elagolix 300 mg twice daily alone, or elagolix 300 mg twice daily with estradiol 1 mg/norethindrone acetate 0.5 mg once daily.

Main Outcome Measures: The primary endpoint was the proportion of women who had <80 mL of MBL during the final month and ≥50% reduction in MBL from baseline to the final month. Adverse events were monitored.

Results: Of 786 women treated across the two trials, 16% (126 women) had coexisting adenomyosis. Among this subset, a significantly greater proportion of women who received elagolix with add-back therapy (77.1% [95% confidence interval, 66.2, 88.0]) met both primary endpoint criteria compared with women who received placebo (12.2% [95% confidence interval, 1.0, 23.4]). Adverse events most frequently reported in the elagolix with add-back adenomyosis subset were hot flushes (18.3%), nausea (11.7%), and night sweats (8.3%).

Conclusions: Elagolix with add-back therapy significantly reduced heavy menstrual bleeding in women with uterine fibroids and coexisting adenomyosis, suggesting that elagolix efficacy was not adversely affected by the presence of adenomyosis (Elaris UF-1 and UF-2 Clinical-Trials.gov numbers, NCT02654054 and NCT02691494).