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Study on Lasofoxifene, Fulvestrant, and Abemaciclib for Advanced Breast Cancer in Women and Men with ESR1 Mutation

Verified siteInvestigationalNo placebo
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What is this trial about?

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

This clinical trial is focused on studying treatments for locally advanced or metastatic breast cancer, specifically in cases where the cancer is estrogen receptor positive (ER+) and human epidermal growth factor receptor 2 negative (HER2-) with an estrogen receptor 1 (ESR1) mutation. The study involves two treatment combinations: one group will receive a combination of Lasofoxifene and Abemaciclib, while the other group will receive a combination of Fulvestrant and Abemaciclib. These treatments are being tested to see how well they work and how safe they are for both pre- and postmenopausal women and men who have previously been treated with certain other medications.

The purpose of the study is to evaluate how long patients can live without their cancer getting worse when treated with these combinations. Participants will be randomly assigned to one of the two treatment groups. The study will involve taking medication in the form of tablets or injections over a period of time, with regular check-ups to monitor health and progress. The study aims to provide valuable information on the effectiveness of these treatment combinations for people with this specific type of breast cancer.

The research process

The trial runs in 7 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Joining the study

    Upon joining the study, eligibility is confirmed based on specific criteria such as age, health status, and previous treatments.

    A written informed consent is required before any procedures begin.

  2. Step 2

    Initial assessment

    An initial assessment is conducted to evaluate the current health status and medical history.

    This may include imaging tests and laboratory evaluations to confirm the presence of specific mutations in the cancer cells.

  3. Step 3

    Randomization

    Participants are randomly assigned to one of two treatment groups.

    One group receives a combination of lasofoxifene and abemaciclib, while the other group receives fulvestrant and abemaciclib.

  4. Step 4

    Treatment administration

    For the lasofoxifene and abemaciclib group, lasofoxifene is taken orally in tablet form, and abemaciclib is also taken orally in tablet form.

    For the fulvestrant and abemaciclib group, fulvestrant is administered as an intramuscular injection, and abemaciclib is taken orally in tablet form.

    The specific dosage and frequency are determined by the study protocol and monitored by the healthcare team.

  5. Step 5

    Regular monitoring

    Participants undergo regular monitoring to assess the effectiveness of the treatment and any side effects.

    This includes routine visits for physical examinations, blood tests, and imaging studies.

  6. Step 6

    Evaluation of progression

    The primary goal is to evaluate progression-free survival, which is the time from the start of treatment until the disease progresses or the participant passes away.

    Secondary evaluations include the objective response rate and overall survival.

  7. Step 7

    Completion of the study

    The study is estimated to conclude by October 2026.

    Upon completion, participants may receive follow-up care and further assessments as needed.

Who can join the trial?

12 criteria

  • Must be at least 18 years old or older, depending on the country's legal age of maturity.
  • Can be a premenopausal or postmenopausal woman or a man. Postmenopausal women are those who are 60 years or older with no vaginal bleeding for a year, or younger women with early menopause confirmed by specific hormone levels, or women who have had their ovaries removed.
  • Should have locally advanced or metastatic breast cancer that has shown signs of getting worse after certain treatments.
  • Must have had no signs of cancer getting worse for at least 6 months while on a specific combination of treatments for advanced breast cancer.
  • Must have specific changes (mutations) in a gene called ESR1, which can be found in blood or breast cancer tissue samples taken within 90 days before joining the study.
  • Should have breast cancer that is either measurable or not measurable according to specific guidelines.
  • May have had one chemotherapy treatment for metastatic cancer before joining the study, but must have recovered from any immediate side effects, except for hair loss and mild nerve damage. There should be a 14-day gap between the last chemotherapy dose and joining the study.
  • Must have a performance score of 0 or 1, which means they are fully active or have some symptoms but can still do light work.
  • Must have proper functioning of organs, shown by specific blood test results.
  • Must be able to swallow tablets.
  • Must be able to understand and sign a consent form voluntarily before any study procedures.
  • If there are cancer spread areas in the brain, they must be without symptoms, treated, not needing steroids for 4 weeks before starting the study, and stable for more than 3 months as shown by an MRI scan.

Who cannot join the trial?

5 criteria

  • Patients who have not previously received treatment with ribociclib or palbociclib. These are specific medications used in treating breast cancer.
  • Patients who do not have locally advanced or metastatic breast cancer. This means the cancer has not spread beyond the breast or nearby areas.
  • Patients whose breast cancer is not estrogen receptor positive (ER+). This means the cancer does not grow in response to the hormone estrogen.
  • Patients whose breast cancer is human epidermal growth factor 2 negative (HER2-). This means the cancer does not have high levels of the HER2 protein.
  • Patients without an estrogen receptor 1 (ESR1) mutation. This is a specific change in the gene that can affect how the cancer behaves.
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Investigated drugs

  • Lasofoxifene

    is a medication being studied for its potential to treat breast cancer. It works by blocking the effects of estrogen in the body, which can help slow down or stop the growth of certain types of breast cancer cells that need estrogen to grow.

  • Abemaciclib

    is a cancer treatment that targets specific proteins in cancer cells, helping to stop their growth and division. It is used in combination with other medications to treat certain types of breast cancer, particularly those that are hormone receptor-positive.

  • Fulvestrant

    is a medication used to treat breast cancer by blocking and breaking down estrogen receptors on cancer cells. This action helps to slow the growth of cancer cells that rely on estrogen. It is often used in combination with other treatments for more effective results.

What is already known about the treatment

  • Lasofoxifene

    Lasofoxifene is administered orally and is currently being studied in clinical trials for its effectiveness in treating locally advanced or metastatic breast cancer, particularly in patients with an ESR1 mutation. It is a selective estrogen receptor modulator (SERM) that works by binding to estrogen receptors, thereby blocking the effects of estrogen in breast tissue, which can slow the growth of certain types of breast cancer. Lasofoxifene is classified as a hormonal therapy and is being evaluated for its potential to improve progression-free survival in combination with other medications.

  • Abemaciclib

    Abemaciclib is taken orally and is an approved medication used in the treatment of certain types of breast cancer, including locally advanced or metastatic cases. It is a cyclin-dependent kinase (CDK) 4/6 inhibitor that works by interfering with the cancer cell cycle, thereby preventing cancer cells from dividing and growing. Abemaciclib is classified as a targeted therapy and is often used in combination with other treatments to enhance its effectiveness against hormone receptor-positive, HER2-negative breast cancer.

  • Fulvestrant

    Fulvestrant is administered via intramuscular injection and is an established treatment for hormone receptor-positive metastatic breast cancer. It acts as an estrogen receptor antagonist by binding to and degrading estrogen receptors, which helps to inhibit the growth of cancer cells that rely on estrogen. Fulvestrant is classified as a hormonal therapy and is used particularly in cases where other hormonal treatments have failed, often in combination with other medications to improve outcomes.

Investigated diseases

Locally Advanced or Metastatic Breast Cancer – This is a type of breast cancer that has spread beyond the breast to nearby tissues or other parts of the body. It is characterized by the presence of cancer cells in the lymph nodes or other organs, indicating that the disease has progressed beyond the initial site. The cancer can be either estrogen receptor-positive (ER+) or human epidermal growth factor receptor 2 negative (HER2-), which influences how the disease behaves and responds to treatment. In some cases, mutations in the estrogen receptor 1 (ESR1) gene may be present, affecting the cancer's growth and progression. The disease can occur in both pre- and postmenopausal women, as well as in men. The progression of this cancer is typically monitored through various clinical endpoints, such as progression-free survival and objective response rate.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2023-503708-10-00Protocol codeSMX 22-002Estimated enrolment500 patients

sourced from the EU Clinical Trials Register and site verification

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