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Study on the Safety and Effectiveness of Trastuzumab Deruxtecan vs. Palbociclib-Based Drug Combination for Advanced HR-Positive, HER2-Low Breast Cancer Patients

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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 advanced breast cancer, specifically a type known as hormone receptor (HR)-positive and HER2-low/ultralow breast cancer. This type of cancer is characterized by certain proteins that are present in lower amounts on the surface of cancer cells. The study aims to compare the safety and effectiveness of a new treatment called trastuzumab deruxtecan (also known as DS-8201a) with a combination of existing treatments, which include CDK4/6 inhibitors and endocrine therapy. CDK4/6 inhibitors are a type of medication that helps stop cancer cells from growing, while endocrine therapy targets hormones that can fuel cancer growth.

The purpose of the study is to see if trastuzumab deruxtecan can better delay the progression of the disease compared to the current standard treatment. Participants in the study will be randomly assigned to receive either trastuzumab deruxtecan or the combination of CDK4/6 inhibitors and endocrine therapy. The study will monitor the participants over a period to assess how long the treatments can keep the cancer from getting worse. The study will also look at the overall safety and any side effects of the treatments.

Participants will receive their assigned treatment and will be regularly monitored by healthcare professionals. The study will involve various assessments, including imaging tests like MRI or CT scans, to track the cancer's response to the treatment. The study is expected to continue until 2029, with recruitment starting in 2025. This research is important for understanding how to better treat this specific type of breast cancer and improve outcomes for patients in the future.

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

    Joining the study

    Upon joining the study, you will be randomly assigned to one of two groups. One group will receive trastuzumab deruxtecan, and the other group will receive a combination of CDK4/6 inhibitor and endocrine therapy.

    You will be informed about the specific treatment you will receive and the schedule for your medication.

  2. Step 2

    Treatment with trastuzumab deruxtecan

    If you are in the group receiving trastuzumab deruxtecan, the medication will be administered through an intravenous infusion. This means the drug will be given directly into your vein.

    The infusion will be scheduled at regular intervals, and the healthcare team will provide you with the exact timing and frequency.

  3. Step 3

    Treatment with CDK4/6 inhibitor and endocrine therapy

    If you are in the group receiving CDK4/6 inhibitor and endocrine therapy, you will take these medications orally in the form of tablets.

    The specific medications may include options like palbociclib, abemaciclib, or ribociclib, combined with endocrine therapies such as letrozole, anastrozole, exemestane, or fulvestrant.

    The healthcare team will provide detailed instructions on the dosage and frequency of each medication.

  4. Step 4

    Monitoring and follow-up

    Throughout the study, regular monitoring will be conducted to assess your health and the effectiveness of the treatment.

    This may include physical examinations, blood tests, and imaging studies like CT scans or MRIs.

    The healthcare team will inform you about the schedule for these assessments and any specific preparations required.

  5. Step 5

    End of treatment

    The study will continue until the estimated end date in October 2029, or until the treatment is no longer effective or safe for you.

    At the end of the study, or if you decide to withdraw, the healthcare team will discuss the next steps and any further treatment options available.

Who can join the trial?

17 criteria

  • Patients must be able to understand the purpose of the study and have signed a written informed consent form before starting any specific procedures.
  • Patients must meet certain criteria related to hormone therapy resistance or sensitivity. This includes:
    • Disease progression during or shortly after hormone therapy.
    • Specific characteristics of the cancer, such as a certain percentage of estrogen receptor-positive cells, high tumor grade, or liver metastases.
    • No prior treatment with any systemic therapy for advanced disease. Patients who had certain treatments in the past and have been off them for a specified time may be eligible.
    • Patients must have adequate bone marrow, liver, and kidney function. This includes specific blood counts and liver enzyme levels.
    • Any side effects from previous cancer treatments must have resolved to a mild level, except for hair loss or other non-risky side effects.
    • Women who can become pregnant must have a negative pregnancy test before starting the study and agree to use effective birth control during the study and for a period after.
    • Men must use effective contraception if they have a partner who can become pregnant and must not donate sperm during the study and for a period after.
    • Patients must be available for treatment and follow-up appointments.
    • Patients must be at least 18 years old at the time of signing the consent form.
    • Patients must have an ECOG performance status of 0-1, which means they are fully active or have some symptoms but do not need bed rest.
    • Patients must have a life expectancy of at least 12 weeks at the time of screening.
    • Patients must have evidence of HER2-low or HER2-ultralow breast cancer, as determined by specific tests on tumor tissue.
    • Patients must have a non-luminal breast cancer subtype, as determined by specific tests on tumor tissue.
    • Patients must have HR-positive status, meaning their cancer cells have receptors for hormones like estrogen or progesterone.
    • Patients must have breast cancer that is locally recurrent or metastatic and cannot be surgically removed with the intent to cure.
    • Patients must have measurable disease according to specific criteria. Patients with only bone disease are not eligible, but those with bone metastases and soft tissue masses larger than 10 mm are eligible.

Who cannot join the trial?

3 criteria

  • Patients with **unresectable** (cannot be removed by surgery) locally recurrent or **metastatic** (cancer that has spread to other parts of the body) breast cancer that is **hormone receptor (HR)-positive** and **human epidermal growth factor receptor 2 (HER2)-low/ultralow** and classified as **non-luminal** by gene expression profiling cannot participate.
  • Patients who do not meet the age requirements specified for the study.
  • Patients who are part of a vulnerable population, which means they might need special protection or care, are not eligible.
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Investigated drugs

  • Trastuzumab deruxtecan

    is a medication used in this clinical trial to treat advanced breast cancer. It is designed to target and attach to specific proteins on cancer cells, helping to deliver a powerful anti-cancer drug directly to the tumor. This targeted approach aims to kill cancer cells more effectively while minimizing damage to healthy cells.

  • CDK4/6 inhibitor-based endocrine therapy

    is another treatment option being studied in this trial. This therapy combines a type of medication known as a CDK4/6 inhibitor with hormone therapy. CDK4/6 inhibitors work by blocking certain proteins that cancer cells need to grow and divide. When used with hormone therapy, which targets hormone receptors on cancer cells, this combination aims to slow down or stop the growth of cancer cells in patients with hormone receptor-positive breast cancer.

What is already known about the treatment

Trastuzumab deruxtecan – This medication is administered as an intravenous infusion, meaning it is given directly into the bloodstream through a vein. It is currently being studied in clinical trials for its effectiveness in treating a specific type of advanced breast cancer that is hormone receptor-positive and has low levels of a protein called HER2. The main goal is to see if it can help patients live longer without their cancer getting worse. Trastuzumab deruxtecan works by delivering a powerful anti-cancer drug directly to the cancer cells, targeting them more precisely. It belongs to a class of drugs known as antibody-drug conjugates, which combine an antibody with a chemotherapy drug to attack cancer cells more effectively.

Investigated diseases

Unresectable Locally Recurrent or Metastatic Hormone Receptor-Positive and Human Epidermal Growth Factor Receptor 2-Low/Ultralow Breast Cancer – This type of breast cancer is characterized by its inability to be surgically removed and its recurrence in the local area or spread to other parts of the body. It is hormone receptor-positive, meaning the cancer cells grow in response to hormones like estrogen or progesterone. The cancer is also classified as HER2-low or ultralow, indicating low levels of the HER2 protein, which can affect the growth of cancer cells. The progression of this disease involves the continued growth and spread of cancer cells, which can invade nearby tissues or metastasize to distant organs. The classification as non-luminal by gene expression profiling suggests a specific pattern of gene activity that influences the cancer's behavior. This type of breast cancer can be challenging to manage due to its advanced stage and specific biological characteristics.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IITrial ID2024-512360-55-00Protocol codeMEDOPP556Estimated enrolment200 patientsSponsorMedica Scientia Innovation Research S.L.

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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.

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