Effect of FB301 on Vaginal Bacterial Profile in Women With Asymptomatic Vaginal Dysbiosis Undergoing a Mock Frozen Embryo Transfer Cycle

NCT07453069 | Not Yet Recruiting Phase 2 DMC FDA Drug

• 1 other identifier: FRB-005
• Study Type: interventional
• Target: 30
• Locations: 1 country
• Sites: 1

Brief Summary

The goal of this clinical trial is to evaluate FB301 during a mock frozen embryo transfer (FET) cycle in pre-menopausal women aged 18 to 40 years with a prior failed FET and a defined vaginal bacterial imbalance (dysbiosis). The main question it aims to answer is:

• Does treatment with FB301 during a mock FET cycle change the proportion of participants who meet the predefined vaginal bacterial threshold compared with placebo? Researchers will compare:
• FB301 given after an initial vaginal cleansing with chlorhexidine (an antiseptic solution),
• FB301 given after an initial vaginal cleansing with saline (saltwater), and
• A placebo capsule given after an initial vaginal cleansing with saline to determine whether these approaches affect vaginal bacterial composition and pregnancy outcomes. Participants will take study treatment for 15 days during a "mock" FET cycle. In a mock cycle, participants receive the hormones needed to prepare the uterus for embryo transfer, but no embryo is transferred. After completing the mock cycle, participants will proceed with their planned frozen embryo transfer and will be followed during pregnancy until birth. Participants will:
• Undergo a vaginal cleansing before receiving the first dose of FB301 or placebo
• Provide vaginal swab samples at up to 5 study visits
• Attend the study centre for up to 8 visits and participate in up to 4 follow-up phone calls
• Complete a mock FET cycle before proceeding with their planned frozen embryo transfer cycle Participants who become pregnant will be followed until birth.

Conditions

Vaginal Dysbiosis

Outcome Measures

Primary Outcomes (1)

• Proportion of participants with ≥90% combined relative abundance of Lactobacillus crispatus, L. jensenii, L. mulieris, L. gasseri, and L. paragasseri as measured by metagenomic sequencing.

  Metagenomic sequencing is performed on cervical vaginal swab samples. Relative abundance is expressed as a percentage of bacterial sequencing reads that are assigned to a specific bacterial species.

  Baseline to Day 16 (Mock FET cycle)

Secondary Outcomes (5)

• Percentage change from baseline in relative abundance of Lactobacillus crispatus, L. jensenii, L. mulieris, L. gasseri, and L. paragasseri as measured by metagenomic sequencing.

  Baseline to Day 16 (Mock FET cycle)

• Biochemical pregnancy rate following frozen embryo transfer (FET), defined as a positive serum beta-human chorionic gonadotropin (hCG) test.

  12-14 days after frozen embryo transfer (FET)

• Clinical pregnancy rate following frozen embryo transfer (FET), defined as the presence of a fetal heartbeat confirmed by transvaginal ultrasound.

  5-6 weeks after frozen embryo transfer (FET)

• Frequency and intensity of all treatment-emergent adverse events (TEAEs), adverse events (AEs), serious adverse events (SAEs), and adverse events of special interest) AESI

  Baseline to End of Study (up to neonatal follow-up assessment (Visit 11), approximately 10 months after FET)

• The incidence of early pregnancy loss, defined as a positive beta-hCG test (biochemical pregnancy) at 12-14 days after FET but no transvaginal ultrasound-confirmed fetal heartbeat at 5-6 weeks after FET (Visit 7)

  5-6 weeks after FET

Study Arms (3)

FB301 / Chlorhexidine

EXPERIMENTAL

Drug: FB-301; Other: Chlorhexidine (0.5%) Vaginal Cleanse

FB301 / Sham

EXPERIMENTAL

Drug: FB-301; Other: Sham vaginal cleanse (saline)

Placebo / Sham

PLACEBO COMPARATOR

Drug: Placebo; Other: Sham vaginal cleanse (saline)

Interventions

FB-301 DRUG

FB301 capsule

FB301 / Chlorhexidine; FB301 / Sham

Placebo DRUG

FB301 Placebo capsule

Placebo / Sham

Chlorhexidine (0.5%) Vaginal Cleanse OTHER

Vaginal cleanse with 0.5% Chlorhexidine solution prior to first IP administration

FB301 / Chlorhexidine

Sham vaginal cleanse (saline) OTHER

Vaginal cleanse with saline solution prior to first IP administration.

FB301 / Sham; Placebo / Sham

Eligibility Criteria

• Age: 18 Years - 40 Years
• Sex: female
• Healthy Volunteers: No
• Age Groups: Adult (18-64)

You may qualify if:

• Able to understand the study and sign a consent form.
• Is a woman aged 18 to 40 years.
• Still has regular menstrual periods (pre-menopausal).
• Has had at least one previous frozen embryo transfer (FET) that did not result in pregnancy within the past 3 years, and this was not due to either male infertility or blocked /damaged fallopian tubes.
• Planning to have a frozen embryo transfer (FET) using one good-quality embryo (grade 3BB or higher) and are considered medically suitable to proceed.
• Willing to have only one embryo transferred during the study cycle.
• A vaginal swab taken at the first study visit shows a specific vaginal microbiome imbalance required for this study (vaginal molecular dysbiosis).
• An ultrasound scan shows no problems with uterus or pelvis that would prevent pregnancy or greatly reduce the chance of pregnancy.
• Recent fertility blood tests (within the last 6 months) show:
• FSH less than 12 IU/L
• AMH greater than 1 ng/mL
• Body mass index (BMI) is between 18 and 38 kg/m².
• From the first study treatment until the mock FET cycle, agrees to:
• Avoid vaginal intercourse or use condoms (without spermicide or lubricant),
• Avoid swimming or hot tubs,

You may not qualify if:

• History of three or more failed frozen embryo transfers (FET) in the past 3 years.
• Have a condition that weakens the immune system (such as uncontrolled diabetes, active cancer, or an organ transplant).
• Currently taking medications that suppress the immune system (such as systemic steroids, biologics, chemotherapy, or transplant medications).
• Is already pregnant before completing the mock FET cycle.
• Test positive for a sexually transmitted infection (such as chlamydia, gonorrhea, Mycoplasma genitalium, or Trichomonas vaginalis).
• Current vaginal yeast infection that requires treatment.
• YCannot safely take the hormone medications required for a frozen embryo transfer (such as estradiol or progesterone).
• Use of intravaginal progesterone gels or solutions.
• Needs regular antibiotics or are likely to require antibiotics during the study.
• Has taken oral, injectable, or vaginal antibiotics within 30 days before screening.
• History of gynecological cancer or other significant gynecological condition that would make participation unsafe.
• Has a medical condition that would make participation unsafe or difficult.
• Has an unstable medical or psychiatric condition that could make it difficult to follow study requirements.
• Has any other condition that could interfere with participation.

Sponsors & Collaborators

• Freya Biosciences ApS: lead
• Premier Research: collaborator

Study Sites (1)

Boston IVF

Waltham, Massachusetts, 02451, United States

Location

MeSH Terms

Interventions

Chlorhexidine; Sodium Chloride

Intervention Hierarchy (Ancestors)

Biguanides; Guanidines; Amidines; Organic Chemicals; Chlorides; Hydrochloric Acid; Chlorine Compounds; Inorganic Chemicals; Sodium Compounds

Study Design

• Study Type: interventional
• Phase: phase 2
• Allocation: RANDOMIZED
• Masking: TRIPLE
• Who Masked: PARTICIPANT, INVESTIGATOR, OUTCOMES ASSESSOR
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: INDUSTRY
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: February 26, 2026
• First Posted: March 5, 2026
• Study Start: April 15, 2026
• Primary Completion (Estimated): October 31, 2026
• Study Completion (Estimated): September 30, 2027
• Last Updated: March 5, 2026

Record last verified: 2026-03

Data Sharing

• IPD Sharing: Will not share

Locations

US (1)