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RecruitingNCT07453069Updated Oct 15, 2026

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

A Phase 2 interventional study of FB-301 and Placebo in Vaginal Dysbiosis, sponsored by Freya Biosciences ApS. Recruiting at 4 sites in United States. Open to female participants aged 18 Years to 45 Years. Per ClinicalTrials.gov, last updated 2026-10-15.

Sponsored by Freya Biosciences ApS · Phase 2, Interventional, and Treatment

From the registry’s dates

  • Started Jul 2026; still recruiting 3 months later.
Updated Oct 15, 2026Site recruiting status changedEligibility revisedGo to Updates ↓
Phase
Phase 2
Study type
Interventional
Enrollment
30
Allocation
Randomized
Ages
18 Years to 45 Years
Sex
Female
01

Where this study stands

Counted across the records on this site · 2026-11-12

Among 44 studies in Dysbiosis with a site in United States — 14 open to participants now, 20 under way, none of them phase 3. Dysbiosis · United States.

Planned enrollment
26th of 35
30 · median 48
Started
2026
with 4 others
Phase 2
3 of 44
3 open now
Primary completion
2026-10
later than 7 of 19 live
Registered
40th of 44
by date

Among the 44 studies in Dysbiosis with a site in United States, this one is the 26th largest by planned enrollment of the 35 interventional ones that give a count, is one of 5 that started in 2026, is one of 3 in phase 2, reaches primary completion later than 7 of the 19 other live ones, and was the 40th registered.

Dysbiosis

187 studies on the registry are indexed under Dysbiosis; 64 are open to participants now.

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Open to participants now

14 of the 44 studies in Dysbiosis with a site in United States are open now. Recruiting first, the newest first:

8 more — sign in →

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A study can be open while its sites in United States have not opened yet or have stopped. Only those recruiting at a site in United States →

Who these studies take

Of the 41 Dysbiosis studies recruiting now, 14 (34%) set no upper age limit and 24 (59%) stop at 75 or younger; 10 take children under 18; 18 take healthy volunteers.

This study: 18 Years to 45 Years · female · no healthy volunteers.

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Watch this landscapeDownload CSVNarrow it in search →With an account: a weekly mail of what changed among 44 studies in Dysbiosis with a site in United States, or all of them as a file.
02

Study 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 45 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 may 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
  • Subsequently complete a mock FET cycle before proceeding with their planned frozen embryo transfer cycle

Participants who become pregnant will be followed-up until birth.

Read the 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 may proceed with their planned frozen embryo transfer during a 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.

03

Conditions studied

  • Vaginal Dysbiosis

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04

Who can participate

The criteria were revised on the registry on Oct 15, 2026. See what changed

Ages eligible
18 Years to 45 Years
Sexes eligible
Female
Accepts healthy volunteers
No

Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.

Inclusion criteria

  1. Able to understand the study and sign a consent form.
  2. Is a woman aged 18 to 45 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. Willing to take part in mock frozen embryo transfer (FET) cycle and is considered medically suitable to subsequently have a frozen embryo transfer (FET) using one good-quality embryo (grade 3BB or higher).
  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 show FSH less than 12 IU/L (within the last 6 months)
  10. Recent fertility blood tests show AMH greater than 1 ng/mL (at the time of oocyte retrieval).
  11. (BMI) is between 18 and 42 kg/m².

  12. 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.
  13. Willing to answer questions about sexual and reproductive activity during the study.
  14. Willing to provide vaginal swab samples at the clinic.
  15. Willing to receive the first study treatment in the clinic and use the study treatment at home as instructed.
  16. Screening blood tests are negative for , , , and syphilis.
  17. Willing to attend all study visits and follow-up assessments and provide information about pregnancy and newborn health outcomes.

Exclusion criteria

Exclusion Criteria:

  1. History of five or more failed frozen embryo transfers (FET) in the past 5 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 , 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. Cannot 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.
Terms in these criteria, in plain language(5)

Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.

BMI (body mass index)

Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.

What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.

Hepatitis B tests

Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.

Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.

Hepatitis C tests

Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.

After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.

HIV

The human immunodeficiency virus, which weakens the immune system.

Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.

Corticosteroids (steroids)

Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.

Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.

05

Study design

Phase
Phase 2
Primary purpose
Treatment
Allocation
Randomized
Intervention model
Parallel assignment
Masking
Triple (Participant, Investigator, Outcomes assessor)
Enrollment
30 participants (estimated)

Study arms

  • Experimental
    FB301 / Chlorhexidine

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

  • Experimental
    FB301 / Sham

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

  • Placebo comparator
    Placebo / Sham

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

Interventions

  • DrugFB-301

    FB301 capsule

  • DrugPlacebo

    FB301 Placebo capsule

  • OtherChlorhexidine (0.5%) Vaginal Cleanse

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

  • OtherSham vaginal cleanse (saline)

    Vaginal cleanse with saline solution prior to first IP administration.

06

What researchers measure

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.

    Time frame: Baseline to Day 16 (Mock FET cycle)

Secondary outcomes

  1. Percentage change from baseline in 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.

    Time frame: Baseline to Day 16 (Mock FET cycle)

  2. 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)

  3. 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)

  4. 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)

  5. 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

07

Study locations

3 of 4 sites recruiting
08

References and documents

Individual participant data

Plan to share: No — There are no current plans to share individual participant data.

No publications or documents are linked to this record.

09

Timeline

1 registry update since Sep 25, 2026
ElapsedEstimatedEstimated, not yet reached

Started Jul 2026 (actual). Primary completion is estimated for Oct 2026, 3 months after the start.

How these figures are worked out, and which studies are left out of them.

Registered
Feb 26, 2026
First posted
Mar 5, 2026
StartActual
Jul 22, 2026
Primary completionEst.
Oct 31, 2026
CompletionEst.
Sep 30, 2027
Last update
Oct 15, 2026
What these dates mean
Start.
When the first participant enrolled; while estimated, when the study expects to open to recruitment.
Primary completion.
When the last participant was examined or treated to collect data for the study's main question, its primary outcome. A study that stopped early gives the date its data collection stopped.
Completion.
When the last participant's last visit took place, for every outcome, secondary ones and side effects included: the end of the study. Often later than primary completion, sometimes the same day.
Actual and Est.
Actual means the registry says the date has happened. Est. (estimated) is a date the sponsor plans or expects. It can still move, and the sponsor is expected to change it to actual once it has passed.
Sites
REACH Fertility is now Recruiting
Oct 15, 2026
Eligibility
Maximum age 40 Years→45 Years; 5 inclusion criteria edited, 1 removed; 2 exclusion criteria edited
What changed in the criteria
Inclusion criteria
  • EditedIs a woman aged 18 to 4045 years.
  • EditedPlanningWilling to take part in mock frozen embryo transfer (FET) cycle and is considered medically suitable to subsequently have a frozen embryo transfer (FET) using one good-quality embryo (grade 3BB or higher) and are considered medically suitable to proceed.
  • EditedRecent fertility blood tests show FSH less than 12 IU/L (within the last 6 months) show:
  • RemovedFSH less than 12 IU/L
  • EditedRecent fertility blood tests show AMH greater than 1 ng/mL (at the time of oocyte retrieval).
  • EditedBody mass index (BMI) is between 18 and 3842 kg/m².
Exclusion criteria
  • EditedHistory of threefive or more failed frozen embryo transfers (FET) in the past 35 years.
  • EditedYCannotCannot safely take the hormone medications required for a frozen embryo transfer (such as estradiol or progesterone).
Oct 15, 2026
Show all 1 update
  1. Oct 15, 2026
    REACH Fertility is now Recruiting
    Eligibility Maximum age 40 Years→45 Years; 5 inclusion criteria edited, 1 removed; 2 exclusion criteria edited
    What changed in the criteria
    Inclusion criteria
    • EditedIs a woman aged 18 to 4045 years.
    • EditedPlanningWilling to take part in mock frozen embryo transfer (FET) cycle and is considered medically suitable to subsequently have a frozen embryo transfer (FET) using one good-quality embryo (grade 3BB or higher) and are considered medically suitable to proceed.
    • EditedRecent fertility blood tests show FSH less than 12 IU/L (within the last 6 months) show:
    • RemovedFSH less than 12 IU/L
    • EditedRecent fertility blood tests show AMH greater than 1 ng/mL (at the time of oocyte retrieval).
    • EditedBody mass index (BMI) is between 18 and 3842 kg/m².
    Exclusion criteria
    • EditedHistory of threefive or more failed frozen embryo transfers (FET) in the past 35 years.
    • EditedYCannotCannot safely take the hormone medications required for a frozen embryo transfer (such as estradiol or progesterone).
    + 3 other changes: identifiers, verification date and description

From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗

10

Registry details

Key details

Study ID
NCT07453069
Lead sponsor
Freya Biosciences ApS
Collaborators
Premier Research
Responsible party
Sponsor
First posted
Mar 5, 2026
Start date
Jul 22, 2026
Primary completion
Oct 31, 2026 (estimated)
Completion
Sep 30, 2027 (estimated)
Last update
Oct 15, 2026

Oversight

Data monitoring committee
Yes
FDA-regulated drug
Yes
FDA-regulated device
No
View the source record on ClinicalTrials.gov ↗

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