A Global Phase 3 Study to Evaluate the Safety and Efficacy of Elagolix in Subjects With Moderate to Severe Endometriosis-Associated Pain

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
nonhormonal 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 regular menstrual cycles with an interval of 24-38
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 gonadotropin-releasing hormone
(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.

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 uterine bleeding.