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Study of Elacestrant and Ribociclib for Patients with Endocrine-Responsive HER2-Negative Early Breast Cancer

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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 HER2-negative early breast cancer, which is a type of breast cancer that does not have high levels of a protein called HER2. The study will compare two different treatment approaches. One group will receive a combination of two medications: elacestrant and ribociclib. Elacestrant is an anti-estrogen medication, which means it works by blocking the effects of estrogen, a hormone that can promote the growth of breast cancer cells. Ribociclib is a cyclin-dependent kinase (CDK) inhibitor, which helps to stop cancer cells from dividing and growing. The other group will receive a combination of an aromatase inhibitor (AI), which is another type of medication that lowers estrogen levels, and ribociclib. In some cases, a GnRH agonist, a type of medication that affects hormone levels, will also be used in premenopausal and perimenopausal women and men.

The purpose of the study is to evaluate which treatment combination is more effective as a neoadjuvant therapy, meaning it is given before the main treatment, usually surgery, to shrink the tumor. Participants in the study will be randomly assigned to one of the two treatment groups. The study will last for a period of six months, during which participants will take the medications orally. The effectiveness of the treatments will be assessed at the time of surgery, using a measure called the modified PEPI score, which helps to evaluate the response of the cancer to the treatment.

This trial aims to provide valuable information on the best treatment approach for patients with endocrine-responsive HER2-negative early breast cancer. By comparing the two treatment combinations, researchers hope to determine which is more effective in reducing the size of the tumor and improving outcomes for patients. The study will also look at other factors, such as changes in tumor size and the proportion of tumors that respond to the treatment, to gain a comprehensive understanding of the benefits of each treatment option.

The research process

The trial runs in 6 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Beginning of the trial

    Upon joining the study, you will be randomly assigned to one of two groups. This means you will either receive a combination of elacestrant and ribociclib or a combination of an aromatase inhibitor (AI) and ribociclib. If you are premenopausal or perimenopausal, you will also receive a GnRH agonist.

    The purpose of this study is to evaluate the effectiveness of these treatments in early breast cancer that is responsive to hormone therapy and does not have an excess of the HER2 protein.

  2. Step 2

    Medication administration

    If you are in the elacestrant group, you will take elacestrant orally. The specific dosage and frequency will be provided by your healthcare team.

    If you are in the AI group, you will take one of the following medications orally: anastrozole, exemestane, or letrozole. The specific medication, dosage, and frequency will be determined by your healthcare team.

    All participants will take ribociclib orally. The dosage is 200 mg, and the frequency will be specified by your healthcare team.

  3. Step 3

    Treatment duration

    The treatment will continue for a period leading up to your surgery. The exact duration will be communicated by your healthcare team based on your individual treatment plan.

  4. Step 4

    Monitoring and assessments

    Throughout the trial, regular monitoring and assessments will be conducted. This includes blood tests and imaging to evaluate the response of your cancer to the treatment.

    A biopsy will be performed at a specific point in the trial to assess the characteristics of your tumor.

  5. Step 5

    Surgery

    At the end of the treatment period, you will undergo surgery. The effectiveness of the treatment will be evaluated by examining the tumor tissue removed during surgery.

  6. Step 6

    Post-surgery follow-up

    After surgery, follow-up visits will be scheduled to monitor your recovery and any further treatment needs. Your healthcare team will provide detailed instructions for these visits.

Who can join the trial?

15 criteria

  • Must provide a signed informed consent before any study-specific tests or procedures that are not part of standard care.
  • Must be a woman or man aged 18 years or older. Women can be postmenopausal, premenopausal, or perimenopausal.
  • Must have a confirmed diagnosis of invasive breast cancer that is HER2-negative and ER-positive. HER2-negative means the cancer does not have high levels of a protein called HER2. ER-positive means the cancer grows in response to the hormone estrogen.
  • Must have a performance status of 0-1 on the ECOG scale, which means you are fully active or have some symptoms but can carry out light work.
  • Women who can become pregnant must have a negative pregnancy test within 28 days before starting the study. Both men and women must use effective birth control during the study and for a period after the last dose of study treatment.
  • Must have a certain level of neutrophils (a type of white blood cell) without needing support from medications that stimulate white blood cell production.
  • Must have a certain level of platelets (cells that help with blood clotting) without needing a transfusion.
  • Must have a certain level of hemoglobin (a protein in red blood cells that carries oxygen). You may receive a transfusion only once to meet this requirement.
  • If not on blood thinners, must have certain levels of blood clotting tests. If on blood thinners, must have a stable treatment plan.
  • Must have certain levels of potassium, sodium, calcium, albumin, phosphate, and magnesium in the blood. Taking vitamin supplements is allowed.
  • Must have certain levels of liver enzymes (AST, ALT, ALP) that are less than three times the upper limit of normal.
  • Must have a certain level of bilirubin in the blood, with exceptions for those with Gilbert's syndrome.
  • Must have a certain level of creatinine in the blood or a certain level of kidney function, which is calculated using a formula based on age, weight, and creatinine level.
  • Must have a normal ECG (a test that measures the heart's electrical activity) with specific parameters, including a heart rate of at least 50 beats per minute.
  • Must be willing and able to provide tumor tissue and blood samples for research purposes.

Who cannot join the trial?

8 criteria

  • Patients with a different type of breast cancer than endocrine-responsive HER2-negative early breast cancer cannot participate.
  • Patients who are not within the specified age range for the study cannot participate.
  • Patients who are not willing or able to follow the study procedures cannot participate.
  • Patients who have other serious health conditions that might interfere with the study cannot participate.
  • Patients who are pregnant or breastfeeding cannot participate.
  • Patients who have participated in another clinical trial recently may not be eligible.
  • Patients who are allergic to any of the study medications cannot participate.
  • Patients who are taking medications that might interfere with the study drugs cannot participate.
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Investigated drugs

  • Elacestrant

    is a medication used in this clinical trial to treat a specific type of breast cancer that responds to hormones. It works by blocking the effects of estrogen, a hormone that can promote the growth of cancer cells. By doing this, elacestrant helps to slow down or stop the growth of the cancer.

  • Ribociclib

    is another medication used in the trial. It is designed to help stop cancer cells from growing and dividing. Ribociclib works by targeting specific proteins in the cancer cells that are responsible for their growth. This helps to control the spread of the cancer.

  • Aromatase Inhibitors (AI)

    are a group of medications used in the trial for treating breast cancer in postmenopausal women. These medications work by reducing the amount of estrogen in the body, which can help slow or stop the growth of hormone-sensitive tumors.

  • GnRH Agonist

    is used in the trial for premenopausal and perimenopausal women, as well as men. This therapy works by lowering the levels of certain hormones in the body, which can help reduce the growth of hormone-sensitive cancer cells.

What is already known about the treatment

  • Elacestrant

    Elacestrant is administered orally and is currently being studied in clinical trials for its effectiveness in treating endocrine-responsive HER2-negative early breast cancer. It is being evaluated for its potential to improve outcomes when combined with ribociclib, compared to standard treatments. Elacestrant works by blocking estrogen receptors, which can slow or stop the growth of certain breast cancer cells that rely on estrogen. It is classified as a selective estrogen receptor degrader (SERD), a type of hormone therapy used in cancer treatment.

  • Ribociclib

    Ribociclib is taken orally and is used in combination with other medications to treat certain types of breast cancer, specifically endocrine-responsive HER2-negative early breast cancer. It is part of ongoing research to determine its effectiveness when paired with elacestrant or other hormone therapies. Ribociclib works by inhibiting proteins called cyclin-dependent kinases (CDK4/6), which are involved in cell division, thereby slowing the growth of cancer cells. It is classified as a CDK4/6 inhibitor, a type of targeted cancer therapy.

Investigated diseases

Endocrine-responsive HER2-negative early breast cancer – This type of breast cancer is characterized by the presence of hormone receptors, meaning the cancer cells grow in response to hormones like estrogen or progesterone. It is classified as HER2-negative, indicating that the cancer cells do not have an excess of the HER2 protein on their surfaces. The progression of this cancer involves the growth and spread of malignant cells within the breast tissue, which can eventually invade surrounding tissues. The disease typically begins as a localized tumor in the breast and may progress to involve nearby lymph nodes. Over time, if not managed, it can spread to other parts of the body. The growth rate and pattern can vary, influenced by hormonal factors and the biological characteristics of the tumor.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IITrial ID2023-505758-17-00Protocol codeABCSG 63Estimated enrolment120 patientsSponsorVerein Zur Praevention Und Therapie Boesartiger Erkrankungen Austrian Breast And Colorectal Cancer Study Group

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