A Study of Zanidatamab for Patients with Previously Treated HER2-Expressing Solid Tumors

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What is this study about?

This study is looking at patients who have solid tumors that show a protein called HER2 on their surface. These are cancers that have spread or grown in a way that cannot be removed by surgery, and previous treatments have not worked. The study will use a medicine called zanidatamab, which is also known by its code name JZP598. This medicine is given through a needle into a vein over a period of time, known as an infusion. The purpose of the study is to see how well zanidatamab works against these tumors and how safe it is for patients to use.

Patients in this study will receive zanidatamab on its own, without combining it with other cancer treatments. The medicine will be given regularly over a treatment period that can last up to 60 weeks. The doctors will check how the tumors respond to the treatment by doing regular scans and tests. Some patients in the study may have breast cancer or cancers of the stomach and food pipe area, and they may have received a specific type of HER2-targeted therapy before, which is a treatment that works against the HER2 protein. For other types of solid tumors, patients should not have had this type of treatment before.

During the study, doctors will monitor patients carefully to see if the treatment is working and to watch for any side effects. This includes checking heart function, blood tests to see how the liver and kidneys are working, and measuring the size of the tumors. Patients will also be asked about symptoms they experience using questionnaires. The study will look at how many patients see their tumors shrink, how long the treatment keeps working, and how long patients live. Blood samples will be taken to measure the amount of medicine in the body and to check if the body makes any reaction against the medicine.

1 Initial assessment and baseline procedures

Before receiving the first dose of the study medication, several assessments will be conducted to establish your baseline health status.

A pregnancy test will be performed within 3 days before the first dose if you are a woman of childbearing potential. This test must be negative to proceed.

Your heart function will be assessed using an echocardiogram or a multiple gated acquisition scan within 4 weeks before the first dose. This measures how well your heart pumps blood, and the result must be at least 50 percent.

Your tumor will be assessed to confirm the presence of at least one measurable lesion. This is done using imaging scans to determine the size and location of your tumor.

Blood tests will be performed to check your blood cell counts, liver function, and kidney function. These tests ensure your body can safely process the study medication.

2 Beginning treatment with zanidatamab

You will receive zanidatamab, the study medication, which is also referred to as JZP598.

The medication is given as an intravenous infusion, meaning it will be administered directly into your vein through a needle or catheter.

The medication comes in the form of a powder for concentrate for solution for infusion, which will be prepared by medical staff before administration.

Treatment is organized in cycles. Each cycle is defined as Cycle 1 Day 1, Cycle 2 Day 1, and so on, representing the first day of each treatment cycle.

The exact dosage, frequency of infusions, and duration of each cycle will be determined by the study protocol and your medical team based on your individual response to treatment.

3 Ongoing monitoring during treatment

Throughout the treatment period, you will be monitored regularly for any side effects or adverse events. These are unwanted effects that may occur as a result of the medication.

Side effects will be assessed and graded according to a standardized system called the Common Terminology Criteria for Adverse Events version 5.0 or higher.

You will be asked to report any symptoms you experience. This may include completing questionnaires about your symptoms and how they affect your daily life.

Blood tests will be performed regularly to monitor your blood cell counts, liver function, and kidney function throughout the treatment period.

Imaging scans will be conducted at specified intervals to assess how your tumor is responding to the treatment. These scans measure changes in the size of your tumor.

If you have a history of brain metastases, meaning cancer that has spread to the brain, additional monitoring may be required. If you are taking corticosteroids for brain metastases, your dose must be stable or decreasing within 14 days of starting treatment.

4 Blood sample collection for medication levels and antibody testing

Blood samples will be collected at specific times during your treatment to measure the serum concentrations of zanidatamab. This means the amount of the study medication present in your blood.

Additional blood samples will be taken to check for anti-zanidatamab antibodies and neutralizing antibodies. These are substances your immune system might produce in response to the medication, which could affect how the medication works.

The frequency, duration, and timing of when these antibodies appear will be recorded and analyzed.

5 Dose adjustments or treatment modifications

If you experience certain side effects, your dose of zanidatamab may need to be reduced. The frequency of these dose reductions will be tracked.

In some cases, if side effects are severe or do not improve, treatment with zanidatamab may need to be stopped temporarily or permanently. The frequency of treatment discontinuations due to side effects will be recorded.

Any changes to your treatment plan will be discussed with you by your medical team.

6 Assessment of treatment response

The primary way your response to treatment will be measured is through the confirmed objective response rate. This is the percentage of patients whose tumors shrink or disappear in response to the medication.

Your tumor response will be assessed by an independent central review using a standardized system called Response Evaluation Criteria in Solid Tumors version 1.1.

Additional measurements will include duration of response, which is how long your tumor continues to respond to treatment, and time to response, which is how long it takes for your tumor to respond.

The disease control rate will also be measured. This includes patients whose tumors shrink, disappear, or remain stable without growing.

Your progression-free survival will be tracked. This is the length of time during and after treatment that your disease does not get worse.

Your overall survival, meaning the length of time you remain alive after starting treatment, will also be recorded.

7 Quality of life and symptom reporting

You will be asked to complete questionnaires about your symptoms and quality of life before starting treatment and regularly during the treatment period.

These questionnaires include the Patient-Reported Outcomes version of the Common Terminology Criteria for Adverse Events and items from the European Organisation for Research and Treatment of Cancer Item Library. These tools help capture how you are feeling and any symptoms you are experiencing.

You will also complete a questionnaire called the Functional Assessment of Chronic Illness Therapy General Physical Health and Treatment Side Effects. This assesses how much side effects are bothering you.

The frequency and severity of your symptoms will be recorded, and the level of bother caused by side effects will be tracked over time.

8 Contraception requirements during treatment

If you are a male participant, you must agree to use a male condom during any sexual activity during the treatment period and for at least 4 months after your last dose of zanidatamab.

If you are a female participant of childbearing potential, you must use a highly effective method of contraception with a failure rate of less than 1 percent per year during the treatment period and for at least 4 months after your last dose.

If you are a woman of childbearing potential, you will have pregnancy tests performed during the treatment period and after treatment ends to ensure you do not become pregnant.

Male participants must refrain from donating fresh unwashed semen during the treatment period and for at least 4 months after the last dose.

9 End of treatment and follow-up

Once you complete treatment with zanidatamab or if treatment is discontinued, you will enter a follow-up period.

During follow-up, you will continue to be monitored for any long-term effects of the medication and for the status of your disease.

The study is estimated to continue until December 31, 2027, though your individual participation length will depend on how you respond to treatment and whether you experience any side effects that require stopping treatment.

Who Can Join the Study?

You must be at least 18 years old or the legal age of adulthood in your country when you sign the consent form
You must have a cancer that has spread to other parts of your body or grown locally and cannot be removed by surgery, and you must have already tried at least one treatment for your advanced cancer without success, and you must have no other treatment options that are known to help
You must have a type of cancer that shows high levels of a protein called HER2, which is a protein that can help cancer cells grow. This must be confirmed by a specific laboratory test showing IHC 3+, which means the highest level of HER2 protein on your cancer cells
You must provide a tissue sample from your tumor for testing. The tissue sample should be less than 2 years old from when it was taken
You must have at least one tumor that can be measured by imaging scans
You must be able to perform normal daily activities with little or no help, as measured by a score of 0 or 1 on a scale that doctors use to assess how well you function
Your doctor must believe you are expected to live for at least 3 months
If cancer has spread to your brain, it must have been treated and be stable. You must have cancer outside the brain that can be measured and shows high HER2 levels. If you are taking steroids for brain cancer, the dose must be stable or decreasing for at least 14 days before starting the study treatment
You must have healthy blood counts including: enough white blood cells called neutrophils which fight infection, enough platelets which help blood clot, and enough hemoglobin which carries oxygen in your blood
Your liver must be working well enough, as measured by blood tests that check bilirubin which is a substance made when your liver breaks down old blood cells, and enzymes called AST and ALT which show how well your liver is functioning
Your kidneys must be working well enough to filter waste from your blood
Your heart must be pumping blood effectively, with at least 50% of the blood in your heart being pumped out with each heartbeat. This is measured by a heart scan done within 4 weeks before starting treatment
If you are a man, you must agree not to donate semen and use condoms during sexual activity while on the study and for at least 4 months after your last dose of study treatment
If you are a woman who can become pregnant, you must use highly effective birth control during the study and for at least 4 months after your last dose of study treatment. You must have a negative pregnancy test within 3 days before starting the study treatment
You must be able to understand and sign the consent form and follow all study requirements

Who Cannot Join the Study?

The source data does not provide specific exclusion criteria for this clinical trial
If you are interested in participating in this study, you will need to discuss with the research team to learn about any conditions or situations that would prevent you from taking part
Generally, clinical trials may exclude patients based on factors such as other medical conditions, previous treatments, or test results, but these specific details are not available in the provided information

Where you can join this trial?

Verified and Recommended Sites

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Verified Sites

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Other Sites

Site Name	City	Country
Hospital Universitario 12 De Octubre	Madrid	Spain
Hospital Clinic De Barcelona	Barcelona	Spain
Hvkpoaxw Vvdn dqpxcnov	Barcelona	Spain

Trial status

Country	Status	Recruitment Start
Spain	Recruiting	28.11.2025

Trial locations

Investigated drugs:

Zanidatamab

Zanidatamab is a treatment being tested in this study for people with certain types of cancer that have a protein called HER2 on their surface. This medication is designed to target and attach to the HER2 protein on cancer cells, which may help stop the cancer from growing or spreading. Zanidatamab works by binding to two different parts of the HER2 protein at the same time, which is different from some other HER2-targeting treatments. This study is looking at how well zanidatamab works in patients whose cancer has already been treated with other medications but has continued to grow or spread.

HER2-positive solid tumors – HER2-positive solid tumors are cancers that have an abnormally high amount of a protein called HER2 on the surface of their cells. This protein promotes the growth and division of cancer cells. These tumors can occur in various parts of the body, including the breast, stomach, and other organs. The overexpression of HER2 causes the cancer cells to grow and multiply more rapidly than normal cells. As the disease progresses, the tumor may grow larger and can spread to nearby tissues. In advanced stages, the cancer may become unresectable, meaning it cannot be completely removed by surgery, or metastatic, meaning it has spread to distant parts of the body.

Trial ID:

2024-516551-41-00

Protocol code:

JZP598-206

NCT ID:

NCT06695845

Trial Phase:

Therapeutic exploratory (Phase II)

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A Study of Zanidatamab for Patients with Previously Treated HER2-Expressing Solid Tumors

What is this study about?

Who Can Join the Study?

Who Cannot Join the Study?