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A study testing zanidatamab combined with chemotherapy before surgery in patients with HER2-positive 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 is looking at HER2-positive breast cancer, which is a type of breast cancer where cancer cells have high levels of a protein called HER2. The study will test a medication called zanidatamab, also known as JZP598, given before surgery along with different chemotherapy medicines. The chemotherapy medicines that may be used include paclitaxel, docetaxel, and carboplatin. Some participants will receive zanidatamab with paclitaxel, others will receive zanidatamab with docetaxel and carboplatin, and another group will receive trastuzumab with pertuzumab along with docetaxel and carboplatin. After completing the treatment period, participants may also receive trastuzumab emtansine or paclitaxel albumin-bound. All study medicines are given through a vein as an infusion.

The purpose of this study is to find out how many people in each treatment group have no remaining cancer or only a small amount in the breast and nearby lymph nodes after receiving the study treatment and before having surgery. The study will also look at how safe these treatments are, what side effects they may cause, and how they affect the body. Additionally, the study will examine whether participants are able to have surgery as planned and will follow participants over time to check if the cancer comes back and how long they survive.

Participants in this study will be randomly assigned to one of the treatment groups and will receive the study medicines for several months before having surgery to remove the cancer. During the study, participants will have regular visits where doctors will perform examinations, take blood samples, and do heart tests to check how the treatment is working and monitor for any side effects. Participants will also be asked to complete questionnaires about how they are feeling and any symptoms they may be experiencing. After surgery, participants will continue to be followed to see how well the treatment worked and to monitor their overall health.

The research process

The trial runs in 8 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Treatment assignment

    Upon joining the study, you will be assigned to one of three treatment groups. The assignment will be done randomly, similar to flipping a coin.

    Group A will receive zanidatamab combined with paclitaxel. Group B will receive zanidatamab combined with docetaxel and carboplatin. Group C will receive trastuzumab combined with pertuzumab, docetaxel, and carboplatin.

    The specific group you are assigned to will determine which medications you receive during the treatment period.

  2. Step 2

    Initial assessments

    Before receiving the first dose of study medication, certain tests will be performed to check your health status.

    A heart function test will be conducted using either an echocardiogram (a type of ultrasound of the heart) or a MUGA scan (a nuclear imaging test of the heart). This test must show that your heart is pumping at least 50% of the blood it contains with each beat.

    Blood tests will be performed to check your organ function and blood cell counts.

    Your physical performance status will be assessed using the ECOG scale, which measures how the disease affects your daily living abilities.

  3. Step 3

    Neoadjuvant treatment period

    You will receive treatment with medications before surgery. This approach is called neoadjuvant therapy.

    All medications in this study are given through a vein, either by injection or infusion (a slow drip into your vein).

    The specific medications, dosages, and schedule will depend on which treatment group you have been assigned to.

    If you are in Group A, you will receive zanidatamab and paclitaxel.

    If you are in Group B, you will receive zanidatamab, docetaxel, and carboplatin.

    If you are in Group C, you will receive trastuzumab, pertuzumab, docetaxel, and carboplatin.

    The treatment will continue for a specified number of cycles as determined by the study protocol.

  4. Step 4

    Monitoring during treatment

    Throughout the treatment period, you will be monitored regularly for any side effects or changes in your health.

    Blood samples will be taken at scheduled times to measure the levels of zanidatamab in your blood and to check for any immune response to the medication.

    You will be asked to report any symptoms or side effects you experience. This will be done using questionnaires called PRO-CTCAE and EORTC Item Library, which help track how you are feeling.

    Another questionnaire called FACIT-GP5 will be used to assess how bothersome any side effects are to you.

    If you are a premenopausal woman, your ovarian function will be monitored through clinical assessments and blood tests.

  5. Step 5

    Surgery

    After completing the neoadjuvant treatment, you will undergo surgery to remove the tumor.

    The surgery will be either a mastectomy (removal of the entire breast) or breast-conserving surgery (removal of the tumor and some surrounding tissue while preserving most of the breast).

    The type of surgery performed will be determined based on your specific situation and discussion with your medical team.

  6. Step 6

    Tissue evaluation after surgery

    After surgery, the removed tissue will be examined by a pathologist who will not know which treatment group you were in.

    The pathologist will determine whether there is any remaining cancer in the breast and lymph nodes. This is called assessing the pathologic complete response, which means no invasive cancer cells remain.

    The tissue will also be evaluated using the RCB classification, which is a scoring system that measures how much cancer remains after treatment.

  7. Step 7

    Follow-up period

    After surgery, you will continue to be followed for a period of time to monitor your recovery and health status.

    During follow-up, you will be monitored for any signs of disease returning or progressing. This is measured as event-free survival, which tracks the time from when you joined the study until the cancer returns, spreads, or any other significant health event occurs.

    Overall survival will also be tracked, which measures the time from when you joined the study until death from any cause.

    The study is expected to continue follow-up until approximately August 2030.

  8. Step 8

    Contraception requirements

    If you are a woman of childbearing potential, you must use highly effective birth control methods during the treatment period and for at least 7 months after receiving the last dose of study medication.

    If you are a male participant, you must also follow contraception guidelines during the treatment period and for at least 7 months after the last dose of study medication.

    You must not be pregnant or breastfeeding to participate in this study.

Who can join the trial?

12 criteria

  • You must be at least 18 years old or the legal adult age in your country when signing the consent form.
  • If you are a man, you must agree to use birth control methods during the treatment period and for at least 7 months after the last dose of study medications.
  • If you are a woman, you must not be pregnant or breastfeeding. You must either be unable to become pregnant, or if you can become pregnant, you must use highly effective birth control methods during the treatment period and for at least 7 months after the last dose of study medications.
  • You must be able to understand and sign the consent form, and agree to follow all study requirements.
  • You must have Stage II or Stage III breast cancer, which means the cancer is in the breast and possibly nearby lymph nodes but has not spread to distant parts of the body. Your tumor must be at least 2 centimeters in size as shown by imaging tests. People with inflammatory breast cancer, which is a type that causes swelling and redness of the breast, can also participate.
  • Your breast cancer must be HER2-positive, which means the cancer cells have high levels of a protein called HER2 that promotes cancer growth. This must be confirmed by laboratory testing.
  • Your cancer must have been tested to determine its hormone receptor status, which tells whether the cancer cells have receptors for hormones like estrogen or progesterone. You can participate whether your cancer is hormone receptor-positive or hormone receptor-negative.
  • If you have cancer in more than one area of your breast, the largest tumor, which must be at least 2 centimeters, must be HER2-positive, and your doctor must have decided to treat you as HER2-positive.
  • You must agree to have surgery to remove the breast tumor after receiving the study medications. This surgery can be either removal of the entire breast or removal of just the tumor with surrounding tissue.
  • You must have an ECOG performance status of 0 or 1, which is a measure of how well you can perform daily activities. A score of 0 means you are fully active, and a score of 1 means you have some restrictions but can still do light work.
  • Your blood test results must meet certain minimum requirements for things like blood cell counts, liver function, and kidney function.
  • Your heart must be functioning well, with a left ventricular ejection fraction of at least 50 percent. This measures how well your heart pumps blood and must be tested within 4 weeks before starting the study medications.

Who cannot join the trial?

3 criteria

  • The study information does not list specific reasons why patients cannot participate in this clinical trial
  • To find out if you can join this study, you will need to discuss your individual health situation with the study doctor
  • The study team will review your medical history and current health to determine if the trial is right for you
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Investigated drugs

  • Zanidatamab

    is a medication being tested in this study for treating HER2-positive breast cancer. It is designed to target a specific protein called HER2 that is found on the surface of some breast cancer cells. This medication works by attaching to the HER2 protein in two different places, which may help stop the cancer cells from growing.

  • Paclitaxel

    is a chemotherapy medication that is commonly used to treat various types of cancer, including breast cancer. It works by stopping cancer cells from dividing and growing, which helps to slow down or stop the spread of cancer in the body.

  • Docetaxel

    is another chemotherapy medication similar to paclitaxel. It is used to treat breast cancer and other types of cancer by preventing cancer cells from multiplying. This helps to reduce the size of tumors and control the disease.

  • Carboplatin

    is a chemotherapy medication that damages the DNA inside cancer cells, which prevents them from growing and dividing. It is often used in combination with other chemotherapy drugs to treat various types of cancer, including breast cancer.

  • Trastuzumab

    is a targeted therapy medication used to treat HER2-positive breast cancer. It works by attaching to the HER2 protein on cancer cells and helps the immune system destroy these cells. It also blocks signals that tell cancer cells to grow.

  • Pertuzumab

    is another targeted therapy medication for HER2-positive breast cancer. It also attaches to the HER2 protein but at a different location than trastuzumab. When used together with trastuzumab, it can provide a more complete blockade of HER2 signaling, which may improve treatment effectiveness.

What is already known about the treatment

  • Zanidatamab

    Zanidatamab is an investigational medication currently being studied in clinical trials for treating HER2-positive breast cancer, which means it has not yet received full approval for widespread use. It is administered through intravenous infusion, typically given in combination with chemotherapy drugs such as paclitaxel or docetaxel and carboplatin as part of treatment before surgery. This medication works by targeting the HER2 protein, which is found in excessive amounts on certain breast cancer cells, and it attaches to two different spots on this protein simultaneously, helping to block cancer cell growth and potentially triggering the immune system to destroy these cells. Zanidatamab belongs to a class of drugs called bispecific antibodies, which are designed to recognize and bind to two different targets on cancer cells more effectively than traditional antibody treatments.

  • Trastuzumab

    Trastuzumab is an approved cancer treatment medication administered through intravenous infusion into a vein, usually given in combination with other chemotherapy drugs for treating HER2-positive breast cancer. It works by attaching to the HER2 protein receptor on the surface of cancer cells, blocking signals that tell the cancer cells to grow and multiply, while also alerting the body's immune system to help destroy these abnormal cells. This medication belongs to a class of drugs called monoclonal antibodies, which are laboratory-made proteins that mimic the immune system's ability to fight harmful cells. Trastuzumab is widely used both before and after surgery, as well as for advanced breast cancer that has spread to other parts of the body.

  • Pertuzumab

    Pertuzumab is an approved cancer medication given through intravenous infusion, typically used in combination with trastuzumab and chemotherapy drugs for treating HER2-positive breast cancer. It works by binding to a different part of the HER2 protein receptor than trastuzumab does, preventing the HER2 protein from pairing with other growth receptors and thereby blocking the signals that cause cancer cells to grow and divide. This medication is classified as a monoclonal antibody and is often used together with trastuzumab to create a more complete blockade of HER2-driven cancer growth. Pertuzumab is used in various treatment settings, including before surgery to shrink tumors, after surgery to reduce recurrence risk, and for advanced cancer that has spread beyond the breast.

Investigated diseases

HER2-positive breast cancer – This is a type of breast cancer where the cancer cells have higher than normal levels of a protein called HER2 on their surface. HER2 is a growth-promoting protein that, when overexpressed, causes cancer cells to grow and divide more rapidly than normal cells. This form of breast cancer tends to be more aggressive and faster-growing compared to HER2-negative breast cancers. The disease can spread to nearby lymph nodes in the armpit area and potentially to other parts of the body. It accounts for approximately 15 to 20 percent of all breast cancer cases. The cancer develops when cells in the breast tissue begin to grow abnormally and form a tumor that can be detected through physical examination or imaging.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IITrial ID2025-523204-68-00Protocol codeEmpowHER 208Estimated enrolment165 patientsSponsorJazz Pharmaceuticals Ireland Limited

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