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Effect of linzagolix and bilastine on breast density in premenopausal women at high risk of breast cancer: a phase II trial

Verified siteRegistered drugNo placebo
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What is this trial about?

A plain-language summary of the goals, design and what participants do

Women who have not yet gone through menopause and who have an increased chance of developing breast cancer may have a higher amount of dense tissue in their breasts, which can make it harder to see changes on a routine X‑ray called a mammogram. The study is testing whether taking the oral tablet linzagolix or the dissolvable tablet bilastine each day for about a year can lower this dense tissue compared with a group that receives a placebo.

The purpose of the study is to compare how much the breast density changes after 12 months between the three groups. Participants will have a mammogram at the start, begin taking the assigned medication, and return for regular check‑ins to report any side effects. After one year they will have a second mammogram, a scan that measures bone strength (called a DXA scan), and will complete short questionnaires about overall health and mood. The study also records any side effects that occur during the year.

The research process

The trial runs in 8 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Enrollment and consent

    After being selected for the study, you will read information about the trial and sign a consent form that confirms your agreement to take part.

    The study staff will check that you meet the eligibility criteria for women who have not yet gone through menopause and who have an increased risk of breast cancer.

  2. Step 2

    Baseline assessments

    You will undergo a mammogram, which is an x‑ray image of the breast used to measure breast density.

    A bone mineral density test (dual‑energy x‑ray absorptiometry) will be performed to evaluate the strength of your bones.

    Blood samples will be taken to check routine laboratory values, including blood counts and chemistry.

    You will complete several questionnaires that ask about your quality of life, anxiety (gadget‑7), and depression (phq‑9).

  3. Step 3

    Randomization to a study group

    Based on a computer‑generated list, you will be placed in one of three groups: the linzagolix group, the bilastine group, or the control group that does not receive an active study medication.

  4. Step 4

    Start of medication (if assigned)

    If you are assigned to the linzagolix group, you will take one 100 mg film‑coated tablet by mouth each day.

    If you are assigned to the bilastine group, you will take one 20 mg orodispersible tablet by mouth each day.

    The control group does not receive a study drug but follows the same visit schedule.

  5. Step 5

    Daily medication routine

    The tablet should be swallowed (or allowed to dissolve in the mouth for bilastine) with water at roughly the same time each day.

    You will continue taking the assigned tablet for the full 12‑month treatment period unless you or the study doctor decides to stop earlier because of safety reasons.

  6. Step 6

    Regular safety monitoring

    Throughout the 12‑month period you will attend scheduled visits where blood will be drawn to monitor safety laboratory parameters such as blood counts, kidney and liver function, and markers of bone metabolism.

    At each visit you will be asked about any side effects or adverse events you may have experienced.

    You will also be asked to complete the medication adherence report scale (MARS‑5) to record how consistently you have taken the study medication.

  7. Step 7

    12‑month follow‑up assessments

    At the end of 12 months you will have a repeat mammogram to measure any change in breast density.

    A second bone mineral density scan will be performed to assess any changes in bone health.

    Blood tests will be repeated to evaluate safety laboratory parameters.

    The same quality‑of‑life, anxiety, and depression questionnaires will be completed again to compare with baseline results.

  8. Step 8

    Study completion

    After the final assessments, the study will be concluded for you.

    The information collected will be used to compare the change in breast density between the linzagolix, bilastine, and control groups.

Who can join the trial?

6 criteria

  • Women who are between 35 and 50 years old.
  • Women who are premenopausal, meaning they still have regular monthly periods (regular menstrual cycles) or have hormone test results (estradiol and FSH) that show normal ovary activity.
  • Women whose calculated 5‑year breast cancer risk is 1.67 % or higher, using a computer program called the Breast Cancer Risk Assessment Tool (Gail model).
  • Women who have a high amount of dense tissue on their first (baseline) breast X‑ray, called a mammogram, classified as BI‑RADS category C or D (these categories mean the breast looks very dense).
  • Women who can understand the study information and can sign a written informed consent form.
  • Women who are willing and able to attend all required study visits and follow the study procedures for the entire follow‑up period.

Who cannot join the trial?

16 criteria

  • Personal history of breast cancer or other cancers that depend on hormones.
  • Taking medicines that should not be used together with the study drugs (linzagolix or bilastine) or that have strong interactions and cannot be stopped or changed before the study.
  • Previous diagnosis of osteoporosis or a bone density score (called a T‑score) of –2.5 or lower on a bone scan.
  • Unexplained genital bleeding at the time of joining the study.
  • Significant liver problems, such as liver enzymes (AST or ALT) more than twice the normal range, total bilirubin more than 1.5 times normal, or any other liver issue the doctor thinks is important.
  • Significant kidney problems, such as an estimated kidney filtration rate (estimated glomerular filtration rate or eGFR) below 60 mL/min/1.73 m², or any other kidney issue the doctor thinks is important.
  • Personal history of long QT syndrome (a heart rhythm condition), serious irregular heartbeats (arrhythmias), or a prolonged QT interval on the initial heart test (ECG).
  • Being enrolled in another clinical trial that uses medicines.
  • Family history of congenital long QT syndrome or an unexplained sudden heart death in a close relative.
  • Clinically significant slow heart rate (bradycardia).
  • Low blood levels of potassium, magnesium, or calcium that have not been corrected before joining (hypokalaemia, hypomagnesaemia, hypocalcaemia).
  • Taking medicines known to lengthen the QT interval when they cannot be stopped or replaced.
  • Pregnancy, breastfeeding, planning to become pregnant, or planning to donate eggs during the study period.
  • Medical or psychiatric conditions that the doctor believes could affect safety, ability to follow the study, or interpretation of the results.
  • Use of any systemic hormonal treatment (including hormonal birth control, hormone replacement therapy, or hormones for gynecological conditions) within the past 12 months.
  • Known contraindications to the study drugs, such as allergies to the active ingredients or any of their inactive components (excipients).
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Investigated drugs

  • linzagolix

    is an oral medication taken as a tablet. In this study it is being tested to see if it can lower the amount of dense tissue in the breast of premenopausal women who have a higher risk of developing breast cancer. The drug works by affecting hormones that influence breast tissue, and researchers hope it may help reduce breast density over a year of treatment.

  • bilastine

    is an oral tablet that is usually used for allergy symptoms, but in this trial it is being examined for a different purpose. Researchers are testing whether bilastine can also lead to a reduction in breast density in premenopausal women at high risk for breast cancer. The medication is taken by mouth and its potential effect on breast tissue will be compared with the other study groups over a 12‑month period.

What is already known about the treatment

Yselty 100 mg film-coated tablets - This oral tablet is taken by mouth and contains 100 mg of linzagolix. Linzagolix is a GnRH antagonist that is already approved for conditions such as uterine fibroids and is being studied for breast density reduction in women at high risk of breast cancer. It works by blocking the GnRH receptor, which lowers the amount of estrogen the body makes. The drug belongs to the class of gonadotropin‑releasing hormone antagonists. Bilastina Teva 20 mg comprimidos bucodispersables EFG - This medication is an oral orodispersible tablet that delivers 20 mg of bilastine when it dissolves in the mouth. Bilastine is a second‑generation antihistamine that is widely available for allergies such as hay fever and hives, and it is being tested for its effect on breast density. It reduces allergy symptoms by blocking H1 histamine receptors on cells. The drug is classified as a non‑sedating H1‑antihistamine.

Investigated diseases

Increased risk of breast cancer - This condition means a person has a higher chance than average of developing breast cancer. Over time, normal breast cells may acquire changes that lead to abnormal growth. If these changes continue, they can progress to a tumor that can become malignant. The risk can increase with age, genetics, hormonal factors, and lifestyle influences.
Trial detailsLast updated 4 Oct 2026
Age18+ yearsPhasePhase IITrial ID2026-525672-26-01Protocol codePremBreastPrev-01Estimated enrolment150 patientsSponsorConsorci Mar Parc De Salut De Barcelona

sourced from the EU Clinical Trials Register and site verification

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