Efficacy and Safety of Elagolix in Combination With Estradiol/Norethindrone Acetate for the Management of Heavy Menstrual Bleeding Associated With Uterine Fibroids in Premenopausal Women

* Subject is a premenopausal female at the time of Screening. * Subject has a diagnosis of uterine fibroids documented by a pelvic ultrasound (transabdominal ultrasound/transvaginal ultrasound). * Subject has heavy menstrual bleeding associated with uterine fibroids as evidenced by menstrual blood loss \> 80 mL during each of two screening menses as measured by the alkaline hematin method. * Subject has negative urine and/or serum pregnancy test in Screening and just prior to first dose. * Subject has an adequate endometrial biopsy performed during Screening, the results of which show no clinically significant endometrial pathology.

* Subject has screening pelvic ultrasound or saline infusion sonohysterography results that show a clinically significant gynecological disorder. * Subject has history of osteoporosis or other metabolic bone disease. * Subject has clinically significant abnormalities in clinical chemistry, hematology, or urinalysis. * Subject has a history of major depression or post-traumatic stress disorder (PTSD) within 2 years of screening, OR a history of other major psychiatric disorder at any time (e.g., schizophrenia, bipolar disorder). * Subject is using any systemic corticosteroids for over 14 days within 3 months prior to Screening or is likely to require treatment with systemic corticosteroids during the course of the study. Over the counter and prescription topical, inhaled, intranasal or injectable (for occasional use) corticosteroids are allowed.