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A Study of Datopotamab Deruxtecan for Patients with Hormone Receptor-Positive, HER2-Negative Advanced or Metastatic Breast Cancer That Did Not Respond to Hormone Therapy

Verified siteInvestigationalNo placebo
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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 a type of cancer called breast cancer that has spread to other parts of the body or cannot be removed by surgery. The cancer being studied is a specific type that is hormone receptor-positive and HER2 IHC 0, which means the cancer cells have receptors for hormones but do not have a protein called HER2 on their surface, or have very low levels of it. The cancer must also be resistant to or not suitable for hormone-based treatments, which are medications that work by blocking hormones that help cancer grow. The treatment being tested in this study is called Datopotamab deruxtecan, which is given through a vein as an infusion. This medication is a type of drug that combines an antibody with a cancer-fighting substance to target cancer cells more directly.

The purpose of this study is to see how well Datopotamab deruxtecan works in stopping the cancer from getting worse, which is measured by looking at how long patients live without their cancer progressing. The study will also look at how safe the medication is by checking for side effects such as mouth sores, eye problems, and other serious reactions. Patients in this study will receive the study medication and will be monitored regularly to see how their cancer responds to treatment and to check for any side effects. The study will also measure how many patients have their cancer shrink or stay the same size, how long any positive response to treatment lasts, and how long patients survive after starting the treatment.

During the study, doctors will take images and samples to track how the cancer is responding to the medication. The study is designed for patients whose cancer has a specific pattern of hormone receptors and HER2 levels, and who are not suitable candidates for another similar medication. Patients will need to have a certain level of general health and organ function to participate, and their cancer must be measurable or visible on scans. The study will continue for several years to collect information about how well the treatment works over time.

The research process

The trial runs in 7 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial assessment and confirmation of eligibility

    Your medical team will confirm that your breast cancer is hormone receptor-positive (meaning the cancer cells have receptors for estrogen or progesterone) and HER2 IHC 0 (a specific type of protein test showing no or minimal HER2 protein on cancer cells).

    Your cancer must be either locally advanced and cannot be removed by surgery, or has spread to other parts of the body (metastatic).

    Your cancer must have progressed during or after hormone therapy, or you are not suitable for further hormone-based treatment.

    Your ECOG performance status (a measure of how the disease affects your daily living abilities) must be 0 or 1, meaning you are fully active or restricted in physically strenuous activity but able to carry out light work.

    Your life expectancy must be at least 12 weeks.

    A sample of your tumor tissue will be provided for testing.

    Your disease must be measurable or evaluable on imaging scans according to specific criteria called RECIST 1.1.

    Blood tests will be performed within 7 days before starting treatment to ensure your bone marrow, liver, and kidneys are functioning adequately.

    You must not be a candidate for another treatment called T-DXd, either because your tumor characteristics do not match, you have other health conditions that prevent its use, or the treatment is not available to you.

  2. Step 2

    Beginning treatment with datopotamab deruxtecan

    You will receive datopotamab deruxtecan (also called Dato-DXd), which is the study medication being tested.

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

    The infusion will be prepared as a solution specifically for this purpose.

  3. Step 3

    Regular treatment cycles and monitoring

    You will receive the study medication according to a regular schedule determined by your medical team.

    During treatment, you will have regular imaging scans to monitor how your cancer is responding to the medication.

    Your medical team will assess whether your disease is progressing, staying stable, or shrinking according to RECIST 1.1 criteria.

    Blood tests and physical examinations will be performed regularly to monitor your overall health and organ function.

  4. Step 4

    Safety monitoring throughout the study

    Your medical team will closely monitor you for side effects related to the study medication.

    Specific attention will be paid to monitoring for oral mucositis or stomatitis (inflammation or sores in the mouth), ocular events (eye-related problems), and any severe side effects (Grade 3 or higher).

    Any side effects will be recorded and graded according to a standard system called NCI CTCAE 5.0.

    Your medical team will manage any side effects that occur during treatment.

  5. Step 5

    Response assessment

    Your response to treatment will be evaluated at regular intervals, including at 24 weeks after starting the medication.

    The assessment will determine if your cancer has completely disappeared (complete response), partially shrunk (partial response), remained stable (stable disease), or progressed.

    If your cancer responds to treatment, the duration of that response will be tracked from when the response is first confirmed until the disease progresses or other specified events occur.

  6. Step 6

    Continuation of treatment

    You will continue receiving the study medication as long as your disease is not progressing and you are tolerating the treatment.

    Treatment may continue until your disease progresses according to RECIST 1.1 criteria, unacceptable side effects occur, or you and your medical team decide to discontinue for other reasons.

    Your medical team will continue to monitor your condition throughout the treatment period.

  7. Step 7

    Long-term follow-up

    After completing or discontinuing the study medication, you will continue to be followed by your medical team.

    Follow-up will continue to track your overall survival and long-term outcomes.

    This follow-up period is expected to continue until the study concludes, which is estimated to be in August 2028.

Who can join the trial?

8 criteria

  • You have breast cancer that cannot be removed by surgery or has spread to other parts of the body (called metastatic), and your cancer cells have hormone receptors (proteins that respond to hormones like estrogen or progesterone) but do not have a protein called HER2 on their surface
  • Your cancer has gotten worse while taking hormone therapy, or your doctor believes hormone therapy is no longer a good treatment option for you
  • You are able to take care of yourself and perform daily activities without significant limitations, with no worsening in your ability to function over the past 2 weeks
  • Your doctor expects you to live at least 12 weeks
  • You can provide a sample of your tumor tissue for testing, either from a previous procedure or a new one
  • Your cancer can be measured on scans, or there is evidence of cancer that can be evaluated by your doctor
  • Your blood tests show that your bone marrow, liver, and kidneys are working well enough
  • You are not suitable for treatment with a medication called T-DXd because either your tumor does not have the specific protein marker needed for that drug to work, or you have other health conditions that make T-DXd unsafe for you, or T-DXd is not available where you live

Who cannot join the trial?

1 criterion

  • The study information provided does not list specific reasons why patients cannot participate in this clinical trial. Please consult with the research team or your doctor to learn about all conditions that would prevent you from joining this study.
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Investigated drugs

Dato-DXd is an investigational cancer treatment being studied for patients with a specific type of breast cancer. This medication is designed to target and fight cancer cells in people whose breast cancer has certain characteristics: it responds to hormones (HR-positive), does not have a particular protein called HER2 on the cancer cells (HER2 IHC 0), and has either spread to other parts of the body or grown locally in a way that cannot be removed by surgery. This treatment is being tested in patients whose cancer has stopped responding to hormone-based therapies.

What is already known about the treatment

Dato-DXd – Dato-DXd is an investigational medication currently being studied in clinical trials for the treatment of advanced breast cancer that has spread to other parts of the body and no longer responds to hormone-based treatments. This drug is administered intravenously, meaning it is given directly into a vein through an injection or infusion. It works as an antibody-drug conjugate, which means it combines a targeted antibody that finds cancer cells with a chemotherapy drug that kills them, delivering the treatment directly to the tumor while minimizing damage to healthy cells. The medication is specifically being tested in patients whose breast cancer is hormone receptor-positive and does not have the HER2 protein on the cancer cell surface.

Investigated diseases

  • Locally Advanced Inoperable Breast Cancer

    This is a form of breast cancer where the tumor has grown significantly within the breast or spread to nearby tissues, but cannot be removed through surgery. The cancer may have extended to the chest wall, skin, or nearby lymph nodes. The disease progresses as cancer cells continue to multiply and invade surrounding structures. Despite being confined to the breast region and nearby areas, the extent of spread makes surgical removal impossible or unsafe. This condition represents an advanced stage of breast cancer that requires systemic treatment approaches. The cancer remains in the regional area rather than spreading to distant organs.

  • Metastatic Breast Cancer

    This occurs when breast cancer cells spread beyond the breast and nearby lymph nodes to distant parts of the body. Common sites of spread include bones, lungs, liver, and brain. The disease progresses as cancer cells travel through the bloodstream or lymphatic system to establish new tumors in other organs. These distant tumors are still breast cancer cells, not cancers of the organs where they have spread. The condition represents the most advanced stage of breast cancer. As the disease progresses, it can affect multiple organ systems throughout the body.

  • Endocrine Therapy Refractory Breast Cancer

    This refers to breast cancer that no longer responds to hormone-based treatments. The cancer initially may have been sensitive to medications that block or reduce hormone effects, but has developed resistance over time. This resistance occurs when cancer cells find ways to grow and multiply despite the presence of hormone-blocking medications. The disease progresses as these resistant cancer cells continue to divide and spread. This condition typically develops in hormone receptor-positive breast cancers after a period of successful hormone therapy. The loss of response to endocrine therapy represents a significant change in how the cancer behaves.

Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IITrial ID2025-521904-23-00Protocol codeD9260C00003Estimated enrolment100 patientsSponsorAstraZeneca AB

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