Efficacy and Safety Study of Elagolix in Women With Endometriosis

A Phase 2, Randomized, Double-Blind, Placebo-Controlled Study to Assess the Efficacy and Safety of NBI-56418 Sodium in Subjects With Endometriosis

The purpose of this study is to evaluate elagolix (NBI-56418) compared to placebo for its effects on endometriosis related pelvic pain and its safety.

Participants were randomized (1:1) to 150 mg elagolix once daily or placebo once daily for the first 8 weeks of the study. Following 8 weeks of dosing, participants continued in the study for an additional 16 weeks in an open-label phase where all participants still enrolled in the study received 150 mg elagolix once daily.

There was no pre-specified primary efficacy end point for this study as there is no single key efficacy outcome measure in this exploratory Phase 2 study. However, the efficacy measures of primary interest included the daily assessment of dysmenorrhea, non-menstrual pelvic pain and dyspareunia on a 4-point scale (0 = none, 1 = mild, 2 = moderate, 3 = severe) using an e-Diary.

Inclusion Criteria:

• Be female, aged 18 to 49 years, inclusive.
• Have moderate to severe pelvic pain due to endometriosis.
• Have a history of regular menstrual cycles.
• Have been surgically (laparoscopy or laparotomy) diagnosed with endometriosis within 8 years of the start of screening.
• Have a Body Mass Index (BMI) of 18 to 36 kg/m², inclusive.
• Agree to use two forms of non-hormonal contraception during the study.

Exclusion Criteria:

• Are currently receiving gonadotropin-releasing hormone (GnRH) agonist, a GnRH antagonist other than NBI-56418, or danazol or have received any of these agents within 6 months of the start of screening.
• Are currently receiving subcutaneous medroxyprogesterone acetate (DMPA-SC) or intramuscular medroxyprogesterone acetate (DMPA-IM) or have received any of these agents within 3 months of the start of screening.
• Are currently using hormonal contraception or other forms of hormonal therapy or received such treatment within the last month.
• Have had surgery for endometriosis within the last month.
• Have had a hysterectomy or bilateral oophorectomy.
• Are using systemic steroids on a chronic or regular basis within 3 months.
• Have uterine fibroids ≥ 3 cm in diameter.
• Have pelvic pain that is not caused by endometriosis.
• Have unstable medical condition or chronic disease.
• Have been pregnant within the last six months.
• Currently breast feeding.