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Comparing RO7771950 with a drug combination of tucatinib, trastuzumab, and capecitabine in patients with HER2-positive metastatic or locally advanced 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 involves patients with HER2-positive breast cancer, a type of cancer where cells have too much of a certain protein that helps them grow. The cancer being studied may be locally advanced, meaning it has spread to nearby tissues, or metastatic, meaning it has spread to other parts of the body. Some patients may also have central nervous system metastases, which refers to cancer that has spread to the brain or spinal cord. The purpose of the study is to compare the effectiveness of a new drug called RO7771950 against a drug named tucatinib.

Participants in the study will receive a combination of medications. One group will take RO7771950 along with trastuzumab and capecitabine. The other group will receive tucatinib combined with trastuzumab and capecitabine. The trastuzumab may be given through an IV infusion, which is a liquid medicine delivered directly into a vein, or as a subcutaneous injection, which is administered just under the skin. The other medications are taken as an oral tablet by mouth.

During the study, medical professionals will monitor how the treatments affect the cancer and how the body responds over time. The research will look at how long the cancer stays stable without growing, a measure known as progression-free survival. Other aspects of the study include monitoring overall survival, how much the tumors shrink, and any side effects experienced during the treatment period.

The research process

The trial runs in 3 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Assignment to a treatment group

    Upon joining the study, a random assignment occurs. this means a method of chance is used to decide which treatment plan will be followed.

    One group will receive ro7771950, trastuzumab, and capecitabine.

    The other group will receive tucatinib, trastuzumab, and capecitabine.

  2. Step 2

    Administration of medications

    The medication capecitabine is taken by mouth at a dose of 2000 mg/m2 (milligrams per square meter of body surface area).

    The medication trastuzumab is administered in one of two ways. it may be given as an intravenous infusion (medicine delivered directly into a vein) at a dose of 8 mg/kg (milligrams per kilogram of body weight), or it may be given via subcutaneous use (an injection under the skin) at a dose of 600 mg.

    If assigned to the comparison group, tucatinib is taken by mouth at a dose of 600 mg.

    If assigned to the test group, ro7771950 is taken in the form of a coated tablet or film-coated tablet.

  3. Step 3

    Monitoring and evaluation

    During the trial, clinical laboratory tests, vital signs, echocardiograms (an ultrasound of the heart), and electrocardiograms (a test that records the electrical activity of the heart) are performed.

    The effectiveness of the treatment is monitored by tracking how long the disease remains stable without getting worse, known as progression-free survival.

    side effects are monitored through assessments of symptoms such as nausea, vomiting, diarrhea, fatigue, or skin rashes.

    quality of life and how symptoms affect daily activities are also tracked using specific questionnaires.

Who can join the trial?

9 criteria

  • You must have a confirmed diagnosis of breast cancer that is either locally advanced (meaning the cancer has grown into nearby tissues and cannot be removed by surgery) or metastatic (meaning the cancer has spread to other parts of the body).
  • Your cancer must be HER2-positive, which means a laboratory test has confirmed that your cancer cells have too much of a specific protein called human epidermal growth factor receptor 2.
  • The HER2 status must be confirmed by a central laboratory using a specific tissue sample called formalin-fixed, paraffin-embedded (FFPE), which is a standard way of preserving tissue for testing.
  • The cancer must be measurable, meaning the tumors can be clearly seen and tracked using medical imaging such as a CT scan, MRI, or X-ray.
  • If you have bone lesions (areas of damage in the bone caused by cancer), they must be lytic or mixed lytic, which describes how the cancer is affecting the bone structure, and they must be visible on scans.
  • You must have already received at least one previous treatment designed to target the HER2 protein.
  • You must have previously used an antibody-drug conjugate (ADC), which is a type of targeted therapy that uses an antibody to deliver a drug directly to cancer cells.
  • If you have previously taken a tyrosine kinase inhibitor (TKI)—a type of drug that blocks signals that help cancer cells grow—it must have been used as a preventive treatment (neoadjuvant or adjuvant) at least 12 months before your cancer was found to be advanced or spread.
  • You cannot have previously used a tyrosine kinase inhibitor (TKI) specifically to treat metastatic or locally advanced breast cancer.

Who cannot join the trial?

18 criteria

  • Taking an experimental drug or a new treatment being tested in other studies within the last 28 days.
  • Receiving other anti-cancer treatments at the same time, though certain hormone treatments for non-cancer issues or specific bone medicines are allowed.
  • Having brain metastases (cancer that has spread to the brain) that cause worsening nerve problems or increased intracranial pressure (pressure inside the skull) leading to symptoms like vomiting, headaches, or vision changes.
  • Having brain cancer spots that need immediate local therapy (treatment focused on a specific area, such as surgery or radiation).
  • Needing a high daily dose of systemic corticosteroids (strong medicines used to reduce inflammation) to manage brain-related symptoms.
  • Needing anti-epileptic medication (drugs used to prevent seizures) to control seizures, unless the person is on a stable dose of a specific medicine called levetiracetam.
  • Having congestive heart failure (a condition where the heart does not pump blood as well as it should) that is moderate or severe.
  • Having significant peripheral arterial disease (narrowed or blocked blood vessels) or issues with the heart muscle, such as hypertrophic cardiomyopathy (thickening of the heart muscle).
  • Showing abnormal results on an ECG (a test that records the electrical activity of the heart), such as heart blocks (interruptions in the heart's electrical signals) or a prolonged PR interval (a delay in the electrical signal moving through the heart).
  • Having an arrhythmia (an irregular heartbeat) that requires medical treatment or intervention.
  • Having unstable angina (chest pain that happens unpredictably or while resting) or having had a myocardial infarction (a heart attack) within the last 6 months.
  • Having undergone coronary artery bypass graft (surgery to improve blood flow to the heart) or stenting (placing a small tube to keep an artery open) within the last 6 months.
  • Having a prolonged QT interval (a measurement of the time it takes for the heart's electrical system to recharge) or a history of Torsade de Pointes (a specific type of dangerous irregular heartbeat).
  • Having poorly controlled hypertension (high blood pressure) where the top number is above 180 or the bottom number is above 100.
  • Having a history of ventricular dysrhythmias (irregular heartbeats starting in the lower chambers of the heart) or structural heart disease (physical changes to the heart's shape or size).
  • Having coronary heart disease (damage to the heart's blood vessels) that causes symptoms or shows signs of low oxygen to the heart.
  • Having significant electrolyte abnormalities (unhealthy levels of essential minerals like potassium, magnesium, or calcium in the blood).
  • Having active or untreated hepatitis B or hepatitis C (viral infections that affect the liver) or any chronic liver disease (long-term liver damage).
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Investigated drugs

  • Trastuzumab

    is a targeted therapy used to treat certain types of breast cancer by blocking a specific protein that helps cancer cells grow.

  • Tucatinib

    is a medication taken by mouth that targets and inhibits a specific enzyme involved in the growth of cancer cells.

  • RO7771950

    is an experimental medication taken as a tablet that is being studied for its ability to cross the blood-brain barrier to treat cancer cells.

  • Capecitabine

    is a type of chemotherapy pill used to stop the growth of cancer cells throughout the body.

What is already known about the treatment

  • Trastuzumab

    This medication is a targeted therapy used to treat certain types of breast cancer and is administered either through an intravenous infusion or as a subcutaneous injection under the skin. It is a widely established treatment in medical practice that works by attaching to specific proteins on the surface of cancer cells to stop them from growing. By blocking these signals, the drug helps prevent the cancer from spreading further.

  • Tucatinib

    This is an oral medication, taken as a pill, that is currently used as a standard treatment for specific advanced breast cancers. It belongs to a class of drugs known as tyrosine kinase inhibitors, which work by blocking specific enzymes inside cancer cells to interrupt their growth signals. This targeted approach helps slow down the progression of the disease at a molecular level.

  • RO7771950

    This substance is administered orally in the form of a coated tablet and is currently being studied in clinical trials for its potential to treat advanced breast cancer. It is classified as a targeted therapy designed to penetrate the blood-brain barrier to reach cancer cells in the central nervous system. The drug works by interfering with specific molecular pathways that cancer cells use to multiply and survive.

  • Capecitabine

    This medication is an oral chemotherapy drug taken in tablet form that is commonly used to treat various types of solid tumors, including breast cancer. It works by being converted into an active substance inside the body, where it interferes with the DNA production required for cancer cells to divide. By disrupting this process, the drug helps stop the rapid growth of cancer cells.

Investigated diseases

HER2-Positive Breast Cancer - This is a type of cancer where cells in the breast grow abnormally due to an excess of a specific protein called human epidermal growth factor receptor 2. The disease can be locally advanced, meaning it has grown into nearby tissues, or metastatic, meaning it has spread to distant parts of the body. In some cases, the cancer cells may also spread to the central nervous system, such as the brain. The condition progresses as these abnormal cells multiply and move through the body. This specific form of cancer is characterized by the presence of the HER2 protein on the surface of the cancer cells.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IVTrial ID2025-524498-17-00Protocol codeWO46069Estimated enrolment650 patientsSponsorF. Hoffmann-La Roche AG

sourced from the EU Clinical Trials Register and site verification

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