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

Starting soon · Phase 2 · Has a placebo group

Conditions studied: Vaginal Dysbiosis

In brief

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.

Key facts

Study ID

NCT07453069

Run by

Freya Biosciences ApS

People needed

30

Starts

2026-04-15

Expected to finish

2027-09-30

Last updated by the study team

2026-03-05

Who can join

Age: 18 and older, up to 40. Sex: female. Healthy volunteers: not accepted.

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

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.

Where it is running

• Boston IVF — Waltham, Massachusetts, United States

Full record on ClinicalTrials.gov

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