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Study of abemaciclib and its connection to severe diarrhea in patients with hormone receptor-positive breast cancer at high risk of return

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What is this trial about?

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

This study involves people with hormone receptor-positive and HER2-negative breast cancer that has a high chance of coming back after initial treatment. The cancer is classified as stage 2 or stage 3, which means it has spread to nearby lymph nodes or the tumor is larger in size. All participants will receive treatment with Verzenios, which contains the active substance abemaciclib, given as tablets taken by mouth. This medication will be used together with an aromatase inhibitor, which is a type of hormone therapy. The purpose of the study is to understand the relationship between the amount of abemaciclib and its breakdown products in the blood and the chance of developing serious diarrhea, which is watery or loose bowel movements that occur more frequently than normal and is the most common side effect of this medication.

During the study, participants will take abemaciclib tablets for up to six months as part of their standard treatment after surgery. Blood samples will be collected at different times to measure the levels of the medication and its breakdown products in the body. The study team will also monitor participants for side effects, particularly diarrhea and low white blood cell counts, which is called neutropenia and can make it harder for the body to fight infections. The information gathered will help doctors better understand how the medication works in the body and how its levels relate to the occurrence of these side effects.

The study will also look at whether the amount of medication circulating freely in the blood, rather than being bound to proteins, affects how people respond to treatment and whether this relates to other health factors. By combining information about medication levels in the blood over time with information about when side effects occur, researchers aim to develop a mathematical model that could help predict which patients might experience more severe side effects. This information may help doctors adjust treatment doses in the future to reduce side effects while maintaining the benefits of the medication.

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

    Starting treatment with abemaciclib

    Your doctor will prescribe abemaciclib, which is an oral medication available in three strengths: 50 mg, 100 mg, or 150 mg tablets. The tablets are film-coated and taken by mouth.

    Abemaciclib will be combined with hormone therapy as part of your treatment after surgery.

    This treatment is designed for patients with hormone receptor-positive, HER2-negative breast cancer at high risk of recurrence.

  2. Step 2

    Blood tests before starting treatment

    Before receiving the first dose of abemaciclib, your blood will be tested to ensure your blood cell counts are within safe ranges.

    The required blood values include: neutrophil count (a type of white blood cell) of at least 1500 cells per cubic millimeter, platelet count of at least 100,000 per cubic millimeter, and hemoglobin level of at least 8 grams per deciliter.

    No growth factor injections should have been administered in the 15 days before this blood test.

  3. Step 3

    Taking abemaciclib daily

    You will take abemaciclib tablets by mouth as prescribed by your doctor.

    The medication is taken as part of your ongoing treatment following surgery for breast cancer.

    Your doctor will determine the appropriate dose and schedule based on your individual needs.

  4. Step 4

    Monitoring for side effects

    During treatment, your doctor will monitor you for potential side effects, particularly diarrhea and neutropenia (low white blood cell count).

    Diarrhea severity is classified into grades: grade 2 (moderate), grade 3 (severe), and grade 4 (life-threatening). Your doctor will assess any diarrhea symptoms according to these grades.

    Neutropenia is also classified by severity, with grades 3 and 4 indicating serious reductions in white blood cell counts that require close monitoring.

  5. Step 5

    Blood sample collection during treatment

    Blood samples will be collected at specific times during your treatment to measure the levels of abemaciclib and its breakdown products (called metabolites M2 and M20) in your blood.

    These measurements help determine how your body processes the medication and whether drug levels are related to side effects.

    Regular blood tests will also monitor your neutrophil concentration to check for changes in your white blood cell count.

  6. Step 6

    Ongoing treatment and monitoring

    You will continue taking abemaciclib combined with hormone therapy as prescribed.

    Your doctor will continue to monitor your overall health status, including your ability to perform daily activities.

    Any side effects or changes in your condition will be documented and managed by your medical team throughout the treatment period.

Who can join the trial?

11 criteria

  • You must be a woman aged 18 years or older with breast cancer
  • You must have hormone receptor positive breast cancer, which means your cancer cells have receptors for estrogen (a female hormone) and/or progesterone (another female hormone) with more than 10% expression
  • You must have HER2 negative or low breast cancer, which means your cancer cells have little or no HER2 protein (a protein that can make cancer grow faster)
  • Your cancer must be classified as stage 2 or stage 3, which refers to the size and spread of the cancer
  • You must have had complete surgery to remove all visible cancer
  • Your cancer must be considered high risk of coming back, which means either 4 or more lymph nodes in your armpit contained cancer, or 1 to 3 lymph nodes in your armpit contained cancer along with a high grade tumor or a tumor measuring 5 centimeters or larger
  • You must be starting treatment with abemaciclib (a cancer medicine) combined with hormone therapy (treatment that blocks hormones)
  • Your performance status (ability to perform daily activities) must be rated between 0 and 2 on the ECOG scale, meaning you are able to care for yourself
  • Your blood tests must show normal levels of white blood cells (cells that fight infection) with at least 1500 per cubic millimeter, platelets (cells that help blood clot) with at least 100,000 per cubic millimeter, and hemoglobin (protein that carries oxygen in blood) at least 8 grams per deciliter
  • You must be enrolled in the social security system or receive benefits through another person
  • You must be able to understand the study information and sign the consent form on your own

Who cannot join the trial?

6 criteria

  • You cannot participate if you are male, as this study only includes female patients
  • You cannot participate if you are under 18 years of age, as this study is only for adult patients
  • You cannot participate if you do not have HR positive, HER2 negative breast cancer, which means your breast cancer must test positive for hormone receptors (proteins that allow hormones to affect cancer growth) and negative for HER2 (a protein that can make cancer grow faster)
  • You cannot participate if your breast cancer is not at high risk of coming back, meaning your cancer must have certain features that make it more likely to return after treatment
  • You cannot participate if you are not receiving adjuvant treatment, which is treatment given after surgery to reduce the risk of cancer returning
  • You cannot participate if you are not being treated with abemaciclib, which is a medicine that helps stop cancer cells from growing
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Investigated drugs

Abemaciclib is a cancer medication used to treat certain types of breast cancer. In this trial, it is being studied in patients with hormone receptor-positive, HER2-negative breast cancer that has a high risk of coming back after initial treatment. The study is looking at how the amount of abemaciclib and its breakdown products in the blood relates to the side effect of severe diarrhea.

What is already known about the treatment

Abemaciclib – Abemaciclib is a medication taken by mouth in tablet form that is used to treat certain types of breast cancer, specifically hormone receptor-positive and HER2-negative breast cancer that has a high chance of coming back after initial treatment. It works by blocking specific proteins called CDK4 and CDK6, which are molecules inside cancer cells that help them grow and divide; by stopping these proteins, the medication slows down or stops the growth of cancer cells. This drug belongs to a class of medications known as CDK4/6 inhibitors and is currently approved and used in clinical practice as part of cancer treatment plans. One of the common side effects that doctors monitor closely is diarrhea, which can sometimes be severe and requires careful management during treatment.

Investigated diseases

Hormone Receptor-Positive, HER2-Negative Breast Cancer – This is a type of breast cancer where the cancer cells have receptors for hormones like estrogen or progesterone on their surface, but do not have an excess of the HER2 protein. The presence of hormone receptors means the cancer cells can grow in response to these hormones. This subtype accounts for a significant portion of all breast cancer cases. When described as high risk of recurrence, it means the cancer has characteristics that make it more likely to return after initial treatment. The disease can spread from the breast tissue to nearby lymph nodes and potentially to other parts of the body over time.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-521696-31-00Protocol codeDOSABEMAEstimated enrolment235 patientsSponsorCentre Hospitalier Universitaire De Poitiers

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