The primary objective of this study is to demonstrate the superior efficacy versus placebo of BG2109 alone and in combination with add-back therapy for the reduction of heavy menstrual bleeding associated with uterine fibroids in premenopausal women.

The study is a prospective, randomized, parallel group, double-blind, placebo-controlled phase 3 study investigating the efficacy and safety of BG2109 alone and in combination with add-back therapy (Estradiol 1 mg / Norethindrone Acetate 0.5 mg) for the treatment of uterine fibroids in China.

Key Inclusion Criteria:

1. Subject is an 18 years and older premenopausal woman.
2. Subject's Body Mass Index ≥ 18 kg/m2.
3. Subject has a diagnosis of uterine fibroids documented by a pelvic ultrasound.
4. Subject's menstrual cycles is between 21 days and 35 days in the last 3 months.
5. Subject has clinical manifestations of heavy menstrual bleeding.
6. Subject's menstrual blood loss >80mL for at least 2 menstrual periods assessed at screening using the alkaline hematin method.

Key Exclusion Criteria:

1. The subject is pregnant or breast-feeding or is planning a pregnancy within the duration of the treatment period of the study.
2. The subject has a history of uterus surgery that would interfere with the study.
3. The subject's condition is so severe that she will require surgery within 6 months.
4. The subject have had or are currently suffering from any estrogen- dependent malignancy.
5. The subject has a significant risk of osteoporosis, or have a known history of osteoporosis or other metabolic bone disease.