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Study of Tucatinib and Ado-Trastuzumab Emtansine for Patients with Advanced HER2+ Breast Cancer

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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 a type of breast cancer known as HER2-positive breast cancer, which is a form of cancer that has high levels of a protein called HER2. The study is specifically for patients with breast cancer that cannot be surgically removed or has spread to other parts of the body, known as unresectable locally-advanced or metastatic HER2-positive breast cancer. The trial is testing a combination of treatments to see if they can help control the cancer. The treatments being studied include a medication called TUKYSA (tucatinib), which is taken as a tablet, and Kadcyla (ado-trastuzumab emtansine), which is given through an infusion into a vein. Some participants will receive a placebo instead of TUKYSA to compare the effects.

The purpose of the study is to see if the combination of TUKYSA and Kadcyla can help patients live longer without their cancer getting worse. Participants in the study will be randomly assigned to receive either the combination of TUKYSA and Kadcyla or Kadcyla with a placebo. The study is designed to be "double-blind," meaning neither the participants nor the researchers will know who is receiving the actual medication or the placebo, to ensure unbiased results. The study will last for a period of time, during which participants will receive regular treatments and have their health monitored closely by the research team.

Throughout the study, participants will undergo various assessments to track the progress of their cancer. These assessments may include imaging tests like MRI (magnetic resonance imaging) to check for any changes in the cancer, especially in the brain if there are concerns about cancer spreading there. The main goal is to compare how long patients can live without their cancer worsening, using a standard set of criteria known as RECIST (Response Evaluation Criteria in Solid Tumors). The study will also look at other outcomes, such as overall survival and response rates to the treatment.

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, participation is confirmed based on specific criteria, including a confirmed diagnosis of HER2+ breast cancer and a history of prior treatment with certain medications.

    Eligibility is determined through medical assessments, including imaging tests to evaluate the presence of brain metastases.

  2. Step 2

    Treatment initiation

    The treatment phase begins with the administration of ado-trastuzumab emtansine (T-DM1) through an intravenous infusion. This medication is given to target cancer cells.

    Participants may also receive tucatinib or a placebo in the form of oral tablets. The dosage for tucatinib is either 150 mg or 50 mg, depending on the specific treatment plan.

  3. Step 3

    Treatment schedule

    The intravenous infusion of T-DM1 is administered on a regular schedule, typically every three weeks, as part of the treatment cycle.

    Oral tablets of tucatinib or placebo are taken daily, with the dosage and frequency determined by the study protocol.

  4. Step 4

    Monitoring and assessments

    Regular monitoring is conducted to assess the response to treatment. This includes imaging tests and other evaluations to measure the progression of the disease.

    Participants are assessed for any side effects or adverse reactions to the medications, with adjustments made as necessary.

  5. Step 5

    Completion of treatment

    The treatment phase continues until the study's end date or until specific criteria for discontinuation are met, such as disease progression or unacceptable side effects.

    Upon completion, participants undergo final assessments to evaluate the overall effectiveness of the treatment.

Who can join the trial?

17 criteria

  • The patient must have a type of breast cancer called HER2+, which means the cancer cells have more of a protein called HER2.
  • The patient must have had a test confirming the presence of HER2+ breast cancer from a specific laboratory.
  • The patient must have been treated before with a type of chemotherapy called a taxane and a drug called trastuzumab.
  • The patient's cancer must have gotten worse after the last treatment, or the patient cannot tolerate the last treatment.
  • The patient must have cancer that can be measured or assessed using a specific method called RECIST v1.1.
  • The patient must have a performance status score of 0 or 1, which means they are fully active or have some symptoms but can still do light work.
  • If the patient has cancer that has spread to the brain, they must meet certain conditions based on a brain scan called an MRI:
    • No signs of cancer in the brain.
    • If there are untreated brain tumors, they should not need immediate treatment.
    • If brain tumors were treated before, they should be stable or have worsened but not need immediate treatment.
    • If new brain tumors were treated, the patient can join if:
      • At least 7 days have passed since a treatment called SRS.
      • At least 14 days have passed since a treatment called WBRT.
      • At least 28 days have passed since brain surgery.
      • There are other areas of cancer that can be evaluated.
      • Records of any brain treatments must be available.
      • The patient must be within a certain age range, which includes adults.
      • Both female and male patients can participate.
      • The study may include patients who are considered vulnerable.

Who cannot join the trial?

6 criteria

  • Patients with other types of cancer that are not **HER2+ breast cancer**. **HER2+** means the cancer has a protein that promotes the growth of cancer cells.
  • Patients who have had surgery to remove the cancer. **Unresectable** means the cancer cannot be removed by surgery.
  • Patients with cancer that is not **locally-advanced** or **metastatic**. **Locally-advanced** means the cancer has spread to nearby tissues, and **metastatic** means it has spread to other parts of the body.
  • Patients who are not within the specified age range for the study.
  • Patients who are not willing or able to follow the study procedures.
  • Patients who are part of a vulnerable population that requires special protection.
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Investigated drugs

  • Tucatinib

    is a medication used in this trial to treat patients with HER2-positive breast cancer. It works by blocking the HER2 protein, which can help slow down or stop the growth of cancer cells. In this study, it is being tested to see if it can improve the outcomes for patients when used in combination with another cancer treatment.

  • Ado-trastuzumab emtansine (T-DM1)

    is a medication used to treat HER2-positive breast cancer. It combines two components: trastuzumab, which targets the HER2 protein on cancer cells, and a chemotherapy drug that helps kill these cells. This combination allows for targeted delivery of chemotherapy directly to the cancer cells, potentially reducing side effects and improving effectiveness. In this trial, it is used alongside tucatinib to evaluate their combined effect on cancer progression.

What is already known about the treatment

  • Tucatinib

    Tucatinib is administered orally in tablet form. It is currently being studied in clinical trials for its effectiveness in treating HER2-positive breast cancer that is either locally advanced and cannot be surgically removed or has spread to other parts of the body. Tucatinib works by specifically inhibiting the HER2 protein, which is involved in the growth and spread of cancer cells. It belongs to the pharmacological class of tyrosine kinase inhibitors.

  • Ado-trastuzumab emtansine (T-DM1)

    Ado-trastuzumab emtansine is administered intravenously. It is an established treatment for HER2-positive breast cancer, particularly in cases where the cancer is advanced or has metastasized. This medication combines trastuzumab, which targets the HER2 protein on cancer cells, with a chemotherapy agent, emtansine, to deliver targeted treatment directly to the cancer cells. It is classified as an antibody-drug conjugate.

Investigated diseases

HER2-positive breast cancer – This is a type of breast cancer characterized by the overexpression of the HER2 protein, which promotes the growth of cancer cells. It can be locally advanced, meaning it has spread to nearby tissues, or metastatic, indicating it has spread to other parts of the body. The disease progresses as cancer cells continue to grow and spread, potentially affecting various organs. HER2-positive breast cancer is known for its aggressive nature compared to other types of breast cancer. The progression of the disease can vary, with some patients experiencing rapid advancement while others may have a slower progression. Understanding the specific characteristics of the cancer is crucial for determining the appropriate management approach.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2024-514733-38-00Protocol codeSGNTUC-016Estimated enrolment567 patientsSponsorSeagen Inc.

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