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 Washout (if applicable) or Screening.
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 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 (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.
