The goal of this clinical trial is to determine the benefit of relugolix 40 milligrams (mg) once a day compared with placebo in heavy menstrual bleeding associated with uterine fibroids. The main question[s] it aims to answer are:

• the benefit of relugolix 40 mg once daily in women with heavy menstrual bleeding associated with uterine fibroids
• the safety of relugolix 40 mg once daily in women with heavy menstrual bleeding associated with uterine fibroids

This study is a phase 3 multicenter, randomized, double-blind, placebo-controlled, parallel-designed efficacy and safety study to evaluate 12 weeks of oral daily relugolix 40 mg co-administered with megestrol acetate 1 mg and medroxyprogesterone acetate 2 mg (the treatment group) or 12 weeks of daily oral relugolix 40 mg placebo (the placebo group) followed by 12 weeks of daily oral relugolix 40 mg co-administered with megestrol acetate 1 mg and medroxyprogesterone acetate 2 mg.

Approximately 120 women with heavy menstrual bleeding associated with uterine fibroids will be enrolled and randomized 2:1 to the treatment group (N=80) or placebo group (N=40).

Stratification variables will include mean screening menstrual blood loss volume (< 225 mL versus ≥ 225 mL) by the alkaline hematin method.

The study consists of a screening period (up to ~13 weeks), a double-blind treatment period (12 weeks), an open-label treatment period (12 weeks) and a follow-up period (4w).

Safety will be assessed throughout the study by monitoring adverse events, vital signs, physical examinations, clinical laboratory tests, 12-lead electrocardiograms, and assessments of bone mineral density.

Inclusion Criteria:

• Premenopausal female aged 18 or older
• Diagnosis of uterine fibroids confirmed by transvaginal/rectal ultrasound during the screening period
• Heavy menstrual bleeding caused by uterine fibroids
• Breast ultrasound results during the screening period meet the BI-RADS classification of 1 to 3
• Able to understand and comply with the study procedures and methods, voluntarily participate in this trial, and sign the informed consent form in writing

Exclusion Criteria:

• History of bilateral oophorectomy, or planned to undergo hysterectomy, bilateral oophorectomy, or other surgical procedures during the study period.
• Previous treatment with gonadotropin-releasing hormone (GnRH) agonists or GnRH antagonists for uterine fibroids has failed.
• History of or current osteoporosis or other metabolic bone disease.
• History of malignant tumor within 5 years prior to screening, except for cured skin cancer, basal cell carcinoma, and other localized malignant tumors.
• History of drug abuse, alcohol abuse, or drug dependence within 2 years prior to screening.
• Presence of an in situ copper intrauterine device (IUD) or a progestin-containing IUD implant/subdermal contraceptive implant during the screening period; subjects who can remove the IUD/subdermal contraceptive implant at least 1 month before enrollment may be allowed to participate.
• Baseline bone mineral density Z-score of < -2.0 at the lumbar spine, total hip, or femoral neck during the screening period.
• Any other factors that the investigator deems unsuitable for participation in this trial.