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Study of elacestrant and ribociclib compared to standard treatment for patients with high-risk ER+/HER2- 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 study focuses on individuals with early breast cancer that is ER+/HER2-. This means the cancer cells have receptors for estrogen (ER+) but do not have an excess of a specific protein called human epidermal growth factor receptor 2 (HER2-). The research aims to compare the effectiveness of a new treatment approach against the current standard of care to see which better prevents the cancer from returning or causing death.

Participants may receive elacestrant, which is a type of medication used to block the effects of hormones that help cancer grow. Some individuals might also be given ribociclib, a medication known as a CDK4/6 inhibitor that helps stop cancer cells from dividing. The treatments are administered as oral use tablets. Depending on the group assigned, some participants may receive these medications alone or in combination with other standard hormone therapies, and some may receive a placebo.

The study follows participants over a period of time to monitor how they respond to the different medication combinations. The process involves tracking long-term outcomes, such as overall survival, which is the length of time from the initial diagnosis until death, and disease-free survival, which measures the time during and after treatment that a person lives without any signs or symptoms of the cancer. The researchers will also look at how the treatments affect the quality of life and any side effects that may occur during the study period.

The research process

The trial runs in 4 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Participation in the study

    Once participation begins, a treatment plan is assigned to compare different types of adjuvant therapy, which is treatment given after the main treatment to reduce the risk of the cancer returning.

  2. Step 2

    Medication administration

    Treatment involves taking oral tablets. depending on the assigned group, the medication may include elacestrant, which is provided as orserdu in doses of 258 mg or 345 mg, or it may include ribociclib, which is provided as kisqali in doses of 400 mg.

  3. Step 3

    Monitoring and follow-up

    The course of the trial includes monitoring survival outcomes and quality of life. quality of life refers to how the treatment affects daily physical and mental well-being.

  4. Step 4

    Long-term assessment

    Assessments of quality of life are conducted 6-monthly during the first 3 years of treatment and yearly after that period has concluded.

Who can join the trial?

17 criteria

  • The patient must be 18 years of age or older at the time of diagnosis.
  • The patient must have a confirmed diagnosis of early breast cancer, which is cancer that has not spread to distant parts of the body.
  • The cancer must be hormone receptor-positive, meaning the cancer cells have receptors for estrogen (ER) or progesterone (PR) that are at a level of 10% or higher.
  • The cancer must be HER2-negative, which means the cancer does not have high levels of the HER2 protein that helps cancer cells grow.
  • The patient must have completed any necessary chemotherapy (drugs used to kill cancer cells) or radiotherapy (using high-energy rays to kill cancer cells) if they were required.
  • The patient must have finished a period of endocrine induction treatment, which is a type of hormone therapy used to see how the cancer responds before starting the main treatment.
  • The patient must have a tumor block, which is a small piece of preserved tissue from the original diagnosis and the surgery, so that doctors can review it in a central lab.
  • The patient must have a good performance status, meaning they are physically able to carry out daily activities and are generally in good health.
  • Blood tests must show healthy levels of neutrophils (white blood cells that fight infection), platelets (cells that help blood clot), hemoglobin (a protein in red blood cells that carries oxygen), and bilirubin (a yellow substance produced by the liver).
  • The patient's kidney function and liver function must be within safe limits, as measured by blood tests like creatinine and transaminase (AST and ALT) levels.
  • Cholesterol and triglyceride levels must be within specific safe ranges.
  • The patient must have a normal electrocardiogram, which is a test that records the electrical activity of the heart, showing a normal heart rate and no dangerous electrical patterns like a long QT interval.
  • The patient must be able to swallow tablets.
  • The patient must agree to use contraception (methods to prevent pregnancy) as outlined in the study rules.
  • The patient must be able to understand the study, sign an informed consent form, and follow all the rules and follow-up appointments.
  • There must be no evidence of distant metastasis, which means the cancer has not spread to other organs like the lungs, liver, or bones.
  • The patient must have a high genomic risk assessment, which is a specialized test that looks at the genes within the tumor to predict how likely the cancer is to return.

Who cannot join the trial?

22 criteria

  • You have a known hypersensitivity (an extreme allergic reaction) to any of the study drugs or their ingredients.
  • You are currently breastfeeding.
  • You are using hormonal contraception (birth control through pills, patches, injections, or implants) or hormonal replacement therapy (medicine used to replace hormones like estrogen or progesterone).
  • There are reasons why you might not be able to follow the study rules or take the medicine as directed, known as poor compliance.
  • You are unable to give informed consent (legal permission to participate in the study).
  • You have not yet recovered from acute toxicities (harmful side effects) from previous cancer treatments that are rated as Grade 1 or higher by medical standards.
  • You have a severe co-morbidity (another serious medical condition) that could interfere with hormone treatments or your safety during the study.
  • For those planned to take ribociclib, you have uncontrolled heart disease or a cardiac repolarization abnormality (an issue with how the heart's electrical activity resets between beats).
  • You have gastrointestinal (GI) issues (problems with the stomach or intestines) that could change how your body absorbs the medicine, such as ulcerative diseases, severe nausea, vomiting, diarrhea, malabsorption syndrome (difficulty absorbing nutrients), or having part of your small intestine removed.
  • You have an uncontrolled infection that requires intravenous (i.v.) medicine (medicine given directly into a vein) like antibiotics, antivirals, or antifungals.
  • You have an active primary immunodeficiency (a condition where your immune system does not work correctly) or a known HIV infection.
  • You have had a different type of cancer in the past that returned within 5 years, though some skin or cervical cancers that were fully cured are allowed.
  • You have an active hepatitis B or hepatitis C infection (viruses that affect the liver).
  • You have received live vaccines (vaccines containing a weakened form of a germ) within the last 30 days.
  • You are participating in the study due to a court order or a government authority.
  • You have a history of invasive cancer (cancer that has spread into nearby tissue) within the last 10 years, with some specific exceptions for certain skin or cervical cancers.
  • You have distant metastases (cancer that has spread to parts of the body far away from the original tumor) beyond nearby lymph nodes.
  • You are currently taking cytotoxic agents (medicines that kill cells, often used in chemotherapy) for reasons not related to cancer.
  • You are currently taking other experimental drugs (medicines being tested in research).
  • You have participated in another interventional clinical trial (a study where a treatment is given) within the last 30 days or within a specific timeframe related to the drug used.
  • You have received treatment with a SERD (a type of hormone-blocking medicine) more than 4 weeks ago.
  • You are currently pregnant.
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Investigated drugs

  • Elacestrant

    is a medication taken by mouth that is used to treat certain types of breast cancer by blocking the effects of estrogen, a hormone that can help cancer cells grow.

  • Ribociclib

    is a medication taken by mouth that belongs to a class of drugs known as CDK4/6 inhibitors, which work to stop cancer cells from dividing and growing.

What is already known about the treatment

  • Elacestrant

    This medication is taken orally in the form of film-coated tablets. It is an approved treatment used primarily for certain types of advanced breast cancer. As a selective estrogen receptor degrader, it works by binding to and breaking down the estrogen receptors that cancer cells use to grow. This drug belongs to a class of medications known as endocrine therapies.

  • Ribociclib

    This medication is administered orally as a film-coated tablet. It is a recognized treatment used to help manage certain types of cancer, including breast cancer. It works at the molecular level by blocking specific proteins called CDK4 and CDK6, which prevents cancer cells from dividing and multiplying. This drug is classified as a CDK4/6 inhibitor.

Investigated diseases

ER+/HER2- early breast cancer - This condition involves cancer cells in the breast that possess estrogen receptors and lack an excess of the HER2 protein. The presence of estrogen receptors means the cancer cells use this hormone to help grow and divide. Because it is classified as early stage, the cancer is typically found in the breast before it has spread significantly to other parts of the body. As the disease progresses, the abnormal cells may multiply and potentially spread to nearby lymph nodes or distant tissues. The specific hormone profile influences how the cells behave and advance over time.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-522484-15-00Protocol codeWSG-AM16Estimated enrolment1 520 patientsSponsorWSG Women's Cancer Study Group GmbH

sourced from the EU Clinical Trials Register and site verification

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