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Study on Abemaciclib, Letrozole, and Fulvestrant for Patients with Advanced HR-positive/HER2-negative Breast Cancer

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

This clinical trial is focused on studying treatments for a type of breast cancer known as HR-positive/HER2-negative breast cancer. This type of cancer is characterized by the presence of hormone receptors (HR) and the absence of a protein called HER2. The study is investigating the effectiveness of different treatment combinations for patients whose cancer is advanced and cannot be surgically removed. The treatments being studied include a medication called abemaciclib, which is a CDK4/6 inhibitor that helps stop cancer cells from growing. It is being tested in combination with other treatments such as letrozole or fulvestrant, which are types of hormone therapies that block the effects of estrogen, a hormone that can promote the growth of breast cancer cells. Additionally, the study is exploring the use of paclitaxel, a chemotherapy drug, which may be given for a short period at the beginning of the treatment.

The purpose of the study is to compare how well these treatment combinations work in controlling the cancer. Participants in the study will be randomly assigned to one of two groups. One group will receive abemaciclib combined with either letrozole or fulvestrant, while the other group will receive paclitaxel. The study will last for up to 12 months, during which time the participants will receive their assigned treatments and be monitored regularly. The researchers will assess the response of the cancer to the treatments at various points throughout the study.

This trial aims to provide valuable information on the best treatment approach for patients with this specific type of breast cancer. By comparing the different treatment combinations, the study hopes to identify which option offers the most benefit in terms of controlling the disease and improving patient outcomes. Participants will be closely monitored by healthcare professionals throughout the study to ensure their safety and to gather important data on the effectiveness of the treatments.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial treatment phase

    The study begins with the administration of abemaciclib combined with either letrozole or fulvestrant. Abemaciclib is taken orally twice daily. Letrozole is also taken orally once daily, while fulvestrant is given as an intramuscular injection every two weeks for the first three doses, then once a month.

    This phase aims to evaluate the initial response to the treatment combination over a period of 12 weeks.

  2. Step 2

    Optional chemotherapy phase

    Some patients may receive a short course of paclitaxel chemotherapy. Paclitaxel is administered as an infusion once a week for up to 12 weeks.

    This phase is designed to assess the potential benefits of adding chemotherapy to the treatment regimen.

  3. Step 3

    Ongoing treatment and monitoring

    Patients continue with the abemaciclib and endocrine therapy (either letrozole or fulvestrant) as long as the treatment is effective and tolerated.

    Regular monitoring includes blood tests, imaging studies, and assessments of health status to track the response to treatment and any side effects.

  4. Step 4

    Response evaluation

    The primary evaluation of treatment response occurs at 12 weeks, using imaging studies to measure changes in tumor size.

    The response is classified as complete response, partial response, stable disease, or progressive disease.

  5. Step 5

    Follow-up and study completion

    Patients are followed up regularly to monitor long-term outcomes, including overall survival and quality of life.

    The study is expected to conclude by June 2025, with final analyses of the collected data to determine the effectiveness of the treatment strategies.

Who can join the trial?

21 criteria

  • Sign an informed consent form before participating in any study-related activities.
  • Be willing and able to provide a sample of the tumor from a metastatic site or the primary breast tumor at the start of the study and when the disease progresses, if possible.
  • Be willing to provide blood samples at different times during the study for research purposes.
  • Be willing to provide stool samples and complete a food questionnaire at the start of the study, 4 weeks after starting treatment, and when the disease progresses.
  • If the disease returned after using a specific type of cancer treatment called a CDK4/6 inhibitor, it must have been at least 12 months since the treatment ended.
  • Have not received any previous treatment for advanced or metastatic breast cancer that cannot be removed by surgery.
  • If radiation therapy was used for metastatic disease, the patient must have recovered from its effects, and at least 14 days must have passed since the last dose before starting the study.
  • All side effects from previous cancer treatments must have improved to a mild level, except for certain conditions like hair loss or nerve damage, at least 14 days before starting the study.
  • Have adequate blood and organ function within 14 days before starting the study, as determined by specific medical tests.
  • Women who can have children must have a negative pregnancy test before starting treatment and agree to use birth control during the study.
  • Men with partners who can have children must agree to use birth control during the study.
  • Be at least 18 years old at the time of signing the consent form.
  • Be able to swallow pills.
  • Be reliable, willing to participate for the entire study duration, and follow study procedures.
  • Have a performance status of 0 or 1, which means being fully active or restricted in physically strenuous activity but able to carry out light work.
  • Have a life expectancy of at least 24 weeks.
  • Women can be pre-menopausal, peri-menopausal, or post-menopausal, as defined by specific criteria like age or medical history.
  • Have breast cancer that is advanced or has spread and cannot be removed with surgery.
  • Meet at least one of the following aggressive disease criteria: presence of disease in organs, evidence of disease progression within 36 months of completing hormone therapy, high-grade tumor, or specific blood test results.
  • Have breast cancer that is positive for estrogen or progesterone receptors and negative for HER2, based on recent testing.
  • Have measurable disease according to specific guidelines, with at least one site that can be biopsied. Patients with only bone lesions are not eligible unless there are identifiable soft tissue components that can be measured.

Who cannot join the trial?

5 criteria

  • Patients who have a different type of breast cancer than HR-positive/HER2-negative cannot participate. This type of cancer is defined by specific proteins on the cancer cells.
  • Patients who have had surgery to remove their breast cancer are not eligible. The study is for those with cancer that cannot be removed by surgery.
  • Patients who do not meet the age requirements for the study cannot participate. The study is for specific age groups.
  • Patients who do not meet the gender requirements for the study cannot participate. The study includes both male and female patients.
  • Patients who are considered part of a vulnerable population may not be eligible. This includes groups who might need special protection in research.
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Investigated drugs

  • Abemaciclib

    is a medication used in this trial to treat breast cancer. It works by blocking certain proteins that help cancer cells grow, which may slow down or stop the progression of the disease. In this study, it is combined with other therapies to see if it can improve treatment outcomes for patients with advanced breast cancer.

  • Letrozole

    is an endocrine therapy used in this trial. It helps to lower estrogen levels in the body, which can slow the growth of certain types of breast cancer that need estrogen to grow. It is used in combination with other treatments to enhance their effectiveness.

  • Fulvestrant

    is another form of endocrine therapy included in the trial. It works by blocking and breaking down estrogen receptors on cancer cells, which can help slow or stop the growth of tumors that rely on estrogen. It is used alongside other medications to improve treatment results.

  • Paclitaxel

    is a chemotherapy drug used in this study. It works by stopping cancer cells from dividing and growing, which can help reduce the size of tumors. In this trial, it is used to see if a short course of chemotherapy can improve the effectiveness of other treatments in patients with aggressive breast cancer.

What is already known about the treatment

  • Abemaciclib

    This medication is administered orally and is currently being studied in clinical trials for its effectiveness in treating HR-positive/HER2-negative breast cancer. It is often used in combination with endocrine therapies like letrozole or fulvestrant. Abemaciclib works by inhibiting certain proteins called cyclin-dependent kinases, which are involved in cell division, thereby slowing down the growth of cancer cells. It is classified as a CDK4/6 inhibitor and is being evaluated for its potential to improve response rates in patients with advanced breast cancer.

  • Letrozole

    This medication is taken orally and is widely used in the treatment of HR-positive breast cancer, particularly in postmenopausal women. It functions by reducing estrogen levels in the body, which can slow or stop the growth of certain types of breast cancer cells that require estrogen to grow. Letrozole is classified as an aromatase inhibitor and is well-established in medical literature as an effective endocrine therapy for breast cancer.

  • Fulvestrant

    Administered via intramuscular injection, fulvestrant is used in the treatment of HR-positive breast cancer, especially in cases where the disease has progressed following other endocrine therapies. It works by binding to estrogen receptors and degrading them, thereby blocking the effects of estrogen on cancer cells. Fulvestrant is classified as an estrogen receptor antagonist and is recognized in medical literature for its role in managing advanced breast cancer.

  • Paclitaxel

    This medication is given through intravenous infusion and is used in the treatment of various cancers, including breast cancer. It works by stabilizing the structure of microtubules, which are essential for cell division, thus preventing cancer cells from dividing and growing. Paclitaxel is classified as a taxane and is well-documented in medical literature for its effectiveness in chemotherapy regimens for aggressive breast cancer.

Investigated diseases

HR-positive/HER2-negative breast cancer – This type of breast cancer is characterized by the presence of hormone receptors (HR-positive) and the absence of excess human epidermal growth factor receptor 2 (HER2-negative). It typically grows in response to hormones like estrogen or progesterone. The disease can be locally advanced, meaning it has spread beyond the breast to nearby tissues, or metastatic, indicating it has spread to other parts of the body. The progression of this cancer can vary, with some tumors growing slowly while others may be more aggressive. Treatment often focuses on blocking the hormones that fuel the cancer's growth.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IITrial ID2023-509591-42-00Protocol codeABIGAILEstimated enrolment162 patientsSponsorMedica Scientia Innovation Research S.L.

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