WST03 Capsule Combined With Metronidazole for Bacterial Vaginosis

This is a multicenter, randomized, double-blind, placebo-controlled Phase 2 trial enrolling approximately 150 pre-menopausal women with bacterial vaginosis (BV). Participants will be randomized 1:1:1 to three groups. All participants will receive oral metronidazole 0.4 g twice daily for 7 days. In addition, participants will take vaginal capsules (high-dose WST03, low-dose WST03, or matched placebo) once daily for 14 days. The primary endpoint is cumulative BV recurrence rate at Week 12. This trial evaluates the efficacy and safety of WST03 plus metronidazole for lowering BV recurrence and explores its impact on vaginal microecology.

Inclusion Criteria: 1. Pre-menopausal female aged 18-55 years inclusive. 2. Regular menstrual cycle of 21-35 days. 3. Clinically diagnosed bacterial vaginosis: at least 3 of 4 Amsel criteria positive with mandatory clue-cell positive; screening Nugent score ≥7. 4. No prior treatment for current episode of BV. 5. Sexually active history; willing for vaginal drug administration; agree to avoid prohibited vaginal products and comply with sexual activity restrictions per protocol. 6. No pregnancy plan during study and within 3 months after last study dose, agree to use effective barrier contraception. 7. Voluntarily sign informed consent form and be able to comply with all study procedures. Exclusion Criteria: 1. Current pelvic inflammatory disease, cervicitis or acute genitourinary infection. 2. Other genital tract infections including vulvovaginal candidiasis, trichomoniasis, aerobic vaginitis, gonorrhea, genital herpes, condyloma acuminata. 3. Unexplained vaginal bleeding; uterine leiomyoma, endometrial hyperplasia or adenomyosis interfering with study assessment. 4. Systemic/vaginal antibacterial or microecological agents within 2 weeks prior to randomization or planned use; vaginal douching / local vaginal therapy within 1 week. 5. Other vaginal infection diagnosed within 2 weeks before randomization except current index BV episode. 6. Long-acting injectable contraceptives / sustained-release contraceptives without required wash-out. 7. Planned systemic steroid therapy within 2 weeks prior to randomization. 8. Use of disulfiram; systemic alcohol- or propylene-glycol-containing products within 3 days before randomization or planned use, with known interaction with metronidazole. 9. Major gynecologic surgery within 6 months; superficial gynecologic procedures within 60 days; pregnancy termination less than 60 days. 10. History of complicated / recurrent vulvovaginal candidiasis within 1 year before ICF. 11. Malignancy within past 5 years (except basal-/squamous-cell skin carcinoma, papillary thyroid carcinoma, cervical carcinoma in-situ). 12. Obvious vaginal mucosal injury on gynecological examination. 13. Intrauterine device in-situ at screening. 14. Abnormal cervical cytology or positive HPV-16 / HPV-18. 15. Abnormal lab parameters: Neutrophil\