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

March 3, 2026 updated by: Freya Biosciences ApS

A Randomized, Double-blind, Three Arm, Multi-center Phase 2 Study to Investigate the Molecular Efficacy and Safety of FB301/Chlorhexidine Compared With FB301/Sham and Placebo/Sham in a Mock FET Cycle in Female Participants 18-40 Years of Age With Asymptomatic Vaginal Molecular Dysbiosis Planning to Undergo a Frozen Embryo Transfer (FET) Cycle

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.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Not yet recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

Vaginal dysbiosis characterized by reduced relative abundance of Lactobacillus species has been associated with reproductive outcomes in women undergoing frozen embryo transfer (FET). This study evaluates the safety, tolerability, and molecular effects of FB301 in women undergoing FET who have no known underlying clinical gynecological conditions but are identified as having molecular dysbiosis by metagenomic sequencing of a vaginal swab collected at screening.

Participants will be randomized to one of three arms: (1) FB301 following a single initial vaginal cleansing with chlorhexidine (an antiseptic solution), (2) FB301 following a single sham cleansing with saline, or (3) placebo following sham cleansing. Cleansing occurs once prior to initiation of study treatment. Participants will then receive 15 days of study treatment during a mock frozen embryo transfer (FET) cycle in which participants receive hormonal preparation of the endometrium but no embryo is transferred. Following completion of the mock cycle, participants will proceed with their planned frozen embryo transfer during the subsequent menstrual cycle, in accordance with standard clinical practice. Participants who become pregnant will be followed until birth.

The primary objective is to evaluate whether treatment increases the proportion of participants achieving a predefined Lactobacillus-dominant vaginal bacterial profile following therapy. Secondary objectives include evaluation of biochemical pregnancy (confirmed by serum beta-hCG testing) and clinical pregnancy (confirmed by transvaginal ultrasound) following the subsequent planned FET cycle.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
30

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Phase 2

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • United States
    • Massachusetts
      • Waltham, Massachusetts, United States, 02451
        • Boston IVF

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  1. Able to understand the study and sign a consent form.
  2. Is a woman aged 18 to 40 years.
  3. Still has regular menstrual periods (pre-menopausal).
  4. 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.
  5. Planning to have a frozen embryo transfer (FET) using one good-quality embryo (grade 3BB or higher) and are considered medically suitable to proceed.
  6. Willing to have only one embryo transferred during the study cycle.
  7. A vaginal swab taken at the first study visit shows a specific vaginal microbiome imbalance required for this study (vaginal molecular dysbiosis).
  8. An ultrasound scan shows no problems with uterus or pelvis that would prevent pregnancy or greatly reduce the chance of pregnancy.

  9. Recent fertility blood tests (within the last 6 months) show:

    • FSH less than 12 IU/L
    • AMH greater than 1 ng/mL
  10. Body mass index (BMI) is between 18 and 38 kg/m².

  11. 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,
    • Avoid using tampons, menstrual cups, sex toys, vaginal cleansers, lubricants, or other vaginal products unless approved by the study team.
  12. Willing to answer questions about sexual and reproductive activity during the study.
  13. Willing to provide vaginal swab samples at the clinic.
  14. Willing to receive the first study treatment in the clinic and use the study treatment at home as instructed.
  15. Screening blood tests are negative for hepatitis B, hepatitis C, HIV, and syphilis.
  16. Willing to attend all study visits and follow-up assessments and provide information about pregnancy and newborn health outcomes.

Exclusion Criteria:

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

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Triple

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: FB301 / Chlorhexidine
Drug: FB-301
FB301 capsule
Other: Chlorhexidine (0.5%) Vaginal Cleanse
Vaginal cleanse with 0.5% Chlorhexidine solution prior to first IP administration
Experimental: FB301 / Sham
Drug: FB-301
FB301 capsule
Other: Sham vaginal cleanse (saline)
Vaginal cleanse with saline solution prior to first IP administration.
Placebo Comparator: Placebo / Sham
Other: Sham vaginal cleanse (saline)
Vaginal cleanse with saline solution prior to first IP administration.
Drug: Placebo
FB301 Placebo capsule

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
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.
Time Frame: Baseline to Day 16 (Mock FET cycle)
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 Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Percentage change from baseline in relative abundance of Lactobacillus crispatus, L. jensenii, L. mulieris, L. gasseri, and L. paragasseri as measured by metagenomic sequencing.
Time Frame: Baseline to Day 16 (Mock FET cycle)
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)
Biochemical pregnancy rate following frozen embryo transfer (FET), defined as a positive serum beta-human chorionic gonadotropin (hCG) test.
Time Frame: 12-14 days after frozen embryo transfer (FET)
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.
Time Frame: 5-6 weeks after frozen embryo transfer (FET)
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
Time Frame: Baseline to End of Study (up to neonatal follow-up assessment (Visit 11), approximately 10 months after FET)
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)
Time Frame: 5-6 weeks after FET
5-6 weeks after FET

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Freya Biosciences ApS

Collaborators

Collaborators

An organization other than the sponsor that provides support for a clinical study. This support may include activities related to funding, design, implementation, data analysis, or reporting.
Premier Research

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
April 15, 2026

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
October 31, 2026

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
September 30, 2027

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
February 26, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
March 3, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
March 5, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
March 5, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
March 3, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
March 1, 2026

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • FRB-005

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

There are no current plans to share individual participant data.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

Clinical Trials on Vaginal Dysbiosis

Clinical Trials on FB-301

Search Similar Trials

Sponsors and Collaborators

Medical Conditions

Drug Interventions

Conditions

Rare Diseases

Drug Interventions

Dietary Supplements

Sponsor/Collaborators

Locations

Cookie Settings

We use cookies to ensure that we give you the best experience on our website. For more details carefully read our Privacy and Cookies Policy. ...>>>You can change your preferences or withdraw your consent at any time by deleting the cookies from your website or computer as described in the policy. Please accept it and choose your preferences by ticking the corresponding boxes in the "Manage Settings" section below. Please carefully read our Terms of Service before you proceed with using any part of this website.
«Manage Settings