A Clinical Study to Evaluate the Safety and Efficacy of Elagolix in Subjects With Moderate to Severe Endometriosis-Associated Pain

This is a Phase 3, multicenter, double-blind, placebo-controlled, randomized study to assess
the safety and efficacy of two doses of elagolix (Dose 1 and Dose 2) versus placebo in
premenopausal 18 to 49 year old women with moderate to severe endometriosis-associated pain.
Approximately 875 subjects will be enrolled into the study at approximately 160 sites. The
study consists of 4 periods: 1) Washout Period (if applicable); 2) a Screening Period of up
to 100 days prior to first dose; 3) a 6 month Treatment Period; and 4) a Post treatment
Follow-up Period of up to 12 months (if applicable). An electronic diary will be dispensed
and training provided to record endometriosis-associated pain, uterine bleeding, and
analgesic medication use for endometriosis-associated pain on a daily basis. Pregnancy
testing will be performed monthly throughout the study. Subjects will be required to use
non-hormonal dual contraception during the study, and will be counseled on appropriate and
effective forms of birth control to promote pregnancy prevention.

Inclusion Criteria: 1. Premenopausal female, between 18 and 49 years of age, inclusive, at
the time of signing consent.

2. Clinical diagnosis of endometriosis (laparoscopy or laparotomy) performed within 10
years of entry into the Washout Period.

3. Agrees to use required birth control methods during the entire length of participation
in the study.

4. Subject has a Composite Pelvic Signs and Symptoms Score total score of ≥ 6 at Screening
with a score of at least 2 for dysmenorrhea AND at least 2 for non-menstrual pelvic pain.
5. Subjects must have at least two menstrual cycles 24 to 38 days within the Screening
Period, prior to Day 1 Exclusion Criteria: 1. Subject is pregnant or breast feeding or is
planning a pregnancy within the next 24 months or is less than 6 months postpartum,
post-abortion, or post-pregnancy at the time of entry into the Screening Period.

2. Subject has a history of previous non-response to GnRH agonists, GnRH antagonists,
Depot Medroxyprogesterone Acetate, or aromatase inhibitors as assessed by subject report
of no improvement in dysmenorrhea or non-menstrual pelvic pain (subject report of partial
response to or side effects from these agents is not exclusionary).

3. Subject has chronic pelvic pain that is not caused by endometriosis that requires
chronic analgesic or other chronic therapy, or that would interfere with the assessment of
endometriosis related pain.

4. Clinically significant gynecologic condition identified on Screening transvaginal
ultrasound or endometrial biopsy.

5. Subject has a history of osteoporosis or other metabolic bone disease. 6. Subject has a
current history of undiagnosed abnormal genital bleeding.