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Phase 1b-2 Study of Elacestrant and Abemaciclib in Patients with Brain Metastases from ER-Positive, HER2-Negative 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 a type of breast cancer known as Estrogen Receptor Positive, HER-2 Negative Breast Cancer that has spread to the brain, referred to as brain metastasis. The study involves two medications: Elacestrant and Abemaciclib. Elacestrant is taken in the form of film-coated tablets, and Abemaciclib is also administered as film-coated tablets. The purpose of the study is to explore the effects of these medications when used together in patients with this specific type of breast cancer.

The study is divided into two phases. In the first phase, the focus is on determining the appropriate dose of Elacestrant when combined with Abemaciclib. In the second phase, the study aims to evaluate how effective this combination is in treating patients with brain metastases from this type of breast cancer. Participants will take the medications orally, and the study will monitor their response to the treatment over time.

Throughout the study, participants will be observed for any changes in their condition, including the size and number of brain metastases. The study will also track any side effects or adverse reactions to the medications. The goal is to gather information that could help improve treatment options for patients with this type of breast cancer in the future.

The research process

The trial runs in 2 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Phase 1b evaluation

    Participation begins with the phase 1b stage of the study.

    The goal of this stage is to find the recommended dose of elacestrant when used together with abemaciclib.

    The medications, elacestrant and abemaciclib, are taken by mouth.

  2. Step 2

    Phase 2 evaluation

    The second stage is the phase 2 evaluation.

    The purpose of this stage is to check how well the combination of elacestrant and abemaciclib works for people with breast cancer that has spread to the brain.

    The medications continue to be taken by mouth.

Who can join the trial?

20 criteria

  • You must sign a consent form, which is a document that explains all the details of the study before you begin any activities.
  • You must have had no more than one seizure (an uncontrolled electrical disturbance in the brain) in the 4 weeks before starting the study treatment.
  • You must have a life expectancy of at least 12 weeks.
  • You must have healthy bone marrow (the part of the body inside bones that makes blood cells) and organ function, based on specific blood tests for:
    • Neutrophils (a type of white blood cell that fights infection).
    • Platelets (cells that help blood clot).
    • Hemoglobin (a protein in red blood cells that carries oxygen).
    • Electrolytes (minerals like potassium, sodium, calcium, and magnesium that keep the body working correctly).
    • Kidney function (measured by creatinine clearance, which shows how well your kidneys filter waste).
    • Albumin (a protein in the blood).
    • Liver function (measured by levels of ALT and AST, which are enzymes that can indicate liver health, and bilirubin, a yellow substance produced by the liver).
    • You must be 18 years of age or older.
    • Women must be either postmenopausal (no longer having menstrual periods) or pre/perimenopausal (still having periods or approaching menopause) and must be taking a specific medication called an LHRH agonist to manage hormone levels if they are not postmenopausal.
    • Your cancer must be ER positive (the cancer cells have receptors for the hormone estrogen) and HER-2 negative (the cancer cells do not have high levels of a specific protein that promotes cancer growth).
    • For the second part of the study, you must have at least one active and measurable brain metastasis (cancer that has spread to the brain and can be seen on a scan like a CT or MRI scan).
    • In the first part of the study, you do not need brain metastases, but you must have at least one measurable cancer lesion somewhere else in your body.
    • If you are taking corticosteroids (medicines that reduce inflammation), your dose must be stable or decreasing and must not be higher than a specific amount (4 mg of dexamethasone) for at least 7 days.
    • You must have previously received at least one endocrine therapy (treatment that interferes with hormones) and have used up to two types of chemotherapy (drugs used to kill cancer cells) and up to two types of CDK 4/6 inhibitors (a type of targeted medicine), excluding abemaciclib.
    • Any side effects from your previous treatments must have mostly resolved, meaning they are no longer severe.
    • Your cancer must have shown radiological progression (the cancer has grown or spread as seen on a scan) or recurrence (the cancer has come back) after your last treatment.
    • You must have an ECOG performance status of 2 or less, which is a scale used by doctors to measure how well you can perform daily activities and how much your cancer affects your lifestyle.

Who cannot join the trial?

24 criteria

  • You need immediate treatment specifically for the central nervous system, which is the part of the body containing the brain and spinal cord.
  • You are currently experiencing organ failure (when an organ stops working correctly) or a visceral crisis (a sudden, life-threatening medical emergency involving internal organs).
  • You have leptomeningeal metastases, which means the cancer has spread to the protective layers covering the brain and spinal cord, or it is found in the cerebrospinal fluid (the clear liquid that surrounds the brain and spinal cord).
  • You have never received any systemic therapy (medical treatment that travels through the entire body, such as pills or IV medicine) for your advanced or metastatic breast cancer.
  • You have previously taken abemaciclib to treat metastatic breast cancer, unless it was used as adjuvant therapy (treatment given after the main treatment to prevent the cancer from coming back) more than 12 months ago.
  • You have previously used elacestrant or other similar experimental drugs, such as SERDs, SERMs, SERCANs, CERANs, or PROTACs (different types of hormone-based or experimental cancer treatments), for metastatic breast cancer.
  • You have another type of cancer that started within the last 3 years, except for certain well-treated skin, bladder, or cervical cancers, or a second breast cancer that is currently in complete remission (a state where there are no signs or symptoms of the disease).
  • You are currently participating in another clinical study for breast cancer.
  • You have taken certain medications too recently, including:
    • Fulvestrant (a hormone therapy) less than 42 days before starting the study.
    • Other endocrine therapies (medicines that affect hormones) less than 14 days before starting.
    • Chemotherapy or other cancer medicines less than 14 days before starting.
    • Experimental cancer drugs within 28 days or 5 half-lives (the time it takes for the amount of a drug in your body to reduce by half).
    • Bisphosphonates or RANKL inhibitors (medicines often used for bone health) within 1 month of starting.
    • You have taken certain foods, herbs, or medicines that affect cytochrome P450 3A4 (a specific enzyme in the liver that helps break down many drugs) within the last 14 days, or herbal supplements like ginseng, ginkgo biloba, or kava within the last 7 days.
    • You have had a pulmonary embolism (a blood clot in the lung), a cerebrovascular accident (a stroke), or a myocardial infarction (a heart attack) in the past 6 months.
    • You have had radiation therapy (the use of high-energy rays to kill cancer cells) within the last 7 days or have not fully recovered from its side effects.
    • You have an active, uncontrolled infection, or you have Hepatitis B or Hepatitis C with a detectable viral load (the amount of virus present in the blood).
    • You have HIV with a detectable viral load.
    • You have had major surgery within the last 4 weeks.
    • You are unable to swallow pills or have a condition like malabsorption syndrome (where the body cannot properly soak up nutrients or medicine from the gut) or other stomach issues that affect how medicine is absorbed.
    • Women of childbearing age who do not agree to use highly effective non-hormonal contraception (methods like an IUD or certain surgical procedures) and do not agree to avoid donating eggs during the study period.
    • Men who are able to father children and whose partners are of childbearing age, if they do not agree to use barrier contraception (such as condoms) or if they do not agree to avoid freezing or donating sperm during the study period.
    • You are currently pregnant or breastfeeding.
    • You have a known intolerance (a bad reaction or inability to handle) to the study drugs or any of the excipients (the inactive substances used to make up a pill, like fillers or coatings).
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Investigated drugs

  • Elacestrant

    is an oral medication taken as a tablet that is used to treat certain types of breast cancer. It works by blocking estrogen, a hormone that can help some cancer cells grow.

  • Abemaciclib

    is an oral medication used to treat breast cancer. It works by blocking specific proteins in the body that help cancer cells grow and divide.

What is already known about the treatment

  • Elacestrant

    This medication is taken orally in the form of film-coated tablets and is used to treat certain types of advanced breast cancer. It belongs to a group of drugs called selective estrogen receptor degraders, which work by attaching to and breaking down the estrogen receptors that help cancer cells grow. By reducing the number of these receptors, the drug helps to stop or slow down the spread of the disease at a molecular level.

  • Abemaciclib

    This medicine is administered orally and is currently used in medical practice to treat advanced stages of breast cancer. It is classified as a CDK4/6 inhibitor, a type of drug that works by blocking specific proteins in the cell cycle that allow cancer cells to divide and multiply. By stopping these proteins from functioning, the medication helps to prevent the rapid growth of tumor cells.

Investigated diseases

Metastatic estrogen receptor-positive, human epidermal growth factor receptor2-negative breast cancer - This is a type of cancer where cells in the breast grow uncontrollably and use estrogen to fuel their development. The cancer is characterized by having receptors for estrogen but lacking high levels of a specific protein called HER2. This condition is considered metastatic when the cancer cells spread from the original breast site to other parts of the body. As the disease progresses, these cancer cells can form new tumors in distant organs. Brain metastasis from estrogen receptor-positive, HER-2 negative breast cancer - This occurs when breast cancer cells that are driven by estrogen and lack the HER2 protein spread specifically to the brain. The cancer cells travel through the bloodstream or lymphatic system to reach brain tissue. Once there, they begin to grow and form new masses within the brain. The disease continues to advance as these secondary tumors increase in size or number.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase ITrial ID2024-512878-98-00Protocol codeELA-0121Estimated enrolment195 patientsSponsorStemline Therapeutics Inc.

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On this site, “treatment” means an investigational medicine being studied in a clinical trial. Its safety and efficacy for the use being studied have not yet been confirmed, some participants may receive a placebo or a comparator medicine, and taking part does not guarantee any health benefit. The decision to take part is made by the doctor at the research site. This site is for information only and does not replace medical advice.

This service is not affiliated with the European Commission, the EMA, or the official CTIS system. Most information comes from publicly available international clinical-trial registries, supplemented by data from academic sites, national regulators and commercial sponsors. On this site, “treatment” and “therapy” mean a medicine being tested in a clinical trial. Its safety and effectiveness in the use being studied are not yet confirmed, some participants may receive a placebo or a comparator, and taking part does not guarantee a health benefit. The doctor at the research site decides who can take part. This site provides information, not medical advice. Certain content and visual elements on this website have been generated or enhanced using artificial intelligence (AI).