An Efficacy and Safety Study of Elagolix (NBI-56418) in Women With Endometriosis

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

This study is designed to see how elagolix works compared to placebo in women with endometriosis and to see the effect, if any, on bone mineral density.

This is a Phase II, multicenter, randomized, double-blind, placebo-controlled parallel-group study to assess the efficacy and safety of elagolix at two dose levels administered once daily for up to 6 months. Participants will be randomized (1:1:1) to one of the following treatment groups for the first 12 weeks of dosing: 150 mg elagolix once daily (QD); 250 mg elagolix QD or placebo QD. Following 12 weeks of dosing, participants will continue in the study for an additional 12 weeks; participants randomized to elagolix will continue to receive their assigned dose and participants randomized to placebo will be re-randomized to receive one of the two doses of elagolix for 12 weeks in a double-blind fashion. Six weeks after the last dose of study drug at the end of Week 24, a follow-up visit will be performed (end of Week 30).

Inclusion Criteria:

• Be female, aged 18 to 49 years, inclusive
• Have moderate to severe pelvic pain due to endometriosis
• Have been surgically (laparoscopy) diagnosed with endometriosis within the last 8 years and have recurrent or persistent endometriosis symptoms
• Have regular menstrual cycle
• 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 or GnRH antagonist 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