The TACTIVE-K clinical trial will help us learn if a combination of 2 study medicines is safe and effective for treating people with advanced or metastatic breast cancer.

If your advanced or metastatic breast cancer has worsened after previous treatment and you are considering your next treatment option, participating in TACTIVE-K may be an option for you.

Participants in TACTIVE-K will receive care from a team of healthcare providers, who will be closely monitoring their health and their cancer

We appreciate your taking the time to learn more.

Who may participate

You may be able to take part in TACTIVE-K if you are 18 years old or older and have advanced or metastatic breast cancer that:

  • expresses estrogen receptors and is called ER-positive
  • does not express a marker, human epidermal growth factor receptor 2 (HER2), and is called HER2-negative
  • cannot be fully treated by surgery
  • is no longer responding to previous treatments

If you think this clinical trial may be right for you, you can call the Pfizer Clinical Trial Contact Center at 1-800-887-7002 to find your nearest study site. When calling, please reference study number NCT06206837.


ER-positive, HER2-negative advanced or metastatic breast cancer


18+ years


Male or Female

Each clinical study has its own guidelines for who can participate, called eligibility criteria. However, only the research study staff can determine if you qualify to enroll in the study.

View more eligibility criteria

What to expect

If you choose to participate, you will review and sign the Informed Consent Document and visit the study doctor’s office to continue with screening to confirm whether you meet all the eligibility criteria and are able to participate.

This clinical trial has two phases (Phase 1b and Phase 2). The study team will let you know which phase is enrolling participants.

The treatment periods will be divided into ‘cycles’ of 4 weeks (28 days). Participants will attend 2-3 visits in the first cycle, 2 visits in the second cycle, and once every 4 weeks (once per cycle) thereafter. All participants will attend an end-of-treatment visit and post-treatment follow-up visit. What happens at each study visit will vary, but may include a physical examination, electrocardiogram (heart check), imaging scans (e.g. MRI or X-ray) and blood sample collection.

Participants in Phase 2 will also have a long-term follow-up visit every 3 months which may be done by telephone or in-person.

Length of treatment

Depends on how you tolerate the study medicines, how your cancer responds, and your personal choice

Number of study visits

4-5 visits in the first 2 months, and once every month thereafter

Long-term follow up

Some participants will be contacted every 3 months

About the study medicines

All participants will receive the 2 study medicines, known as vepdegestrant and PF-07220060. Both study medicines are taken as tablets by mouth. There is no placebo in this clinical trial.

The first study medicine, vepdegestrant is believed to work by targeting and degrading the estrogen receptor that is found in breast cancer cells. This prevents estrogen from connecting to the cancer cells, which may block estrogen’s effects of helping the cancer cells grow.

The second study medicine, PF-07220060 is thought to work by blocking specific growth signals within breast cancer cells, preventing the cells from dividing. PF-07220060, when combined with hormone therapy, may work as a “brake” to slow down the growth of cancer cells.

About the study medicines

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Image of a woman sitting outside a cafe

Be represented

Image of a woman hugging a man – Pfizer Clinical Trials
Image of a woman hugging a man – Pfizer Clinical Trials

Be represented

People who take part in clinical trials are key to advancing medical research. By taking part in the TACTIVE-K clinical trial, you will be helping to improve scientific knowledge of breast cancer and potentially help yourself and others with breast cancer in the future.

Multiple factors, including genetics, race, ethnicity, age, and sex can all impact how different people respond to the same treatment. That is why it is important that clinical trials include people of all backgrounds. The greater the diversity among clinical trial participants, the more we can learn about potential medicines, including how they work for different people.

When you participate in a clinical trial, you’re helping to represent both your community and all people who are affected by advanced or metastatic breast cancer.

Frequently asked questions

Where can I find more information about this clinical trial?
Details about the study medicines provided in TACTIVE-K and other aspects of this clinical trial will be answered during the informed consent process.
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Will I receive active medicine?
Yes. All participants will receive active medicines. There is no placebo in this clinical trial
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Will I know which treatments I will receive?
Yes. All participants will receive both study medicines, vepdegestrant and PF-07220060, and will know the doses that they are receiving. Medicine doses may vary across participants in order to find the best dosing options for treating advanced or metastatic breast cancer.
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How should I take the study medicines in TACTIVE-K?

Vepdegestrant is taken by mouth once a day at the same time in the morning with food and should be taken first.

PF-07220060 is taken by mouth twice a day at the same time with food. The first dose should be taken in the morning after taking the other study medicine and the second dose about 12 hours later.

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Do I need to provide tumor samples during the clinical trial?

You will be asked to provide a sample of your tumor from when you were diagnosed with either metastatic disease (spread of breast cancer to other parts of your body) or local recurrence (reappearance of your tumor after a period of improvement).

There may be an optional (not required) biopsy collected at the end of the study treatment. This biopsy will only occur if you stop taking the study medicines because your cancer gets worse, if your study doctor considers the procedure safe for you, and if you agree to provide separate consent for this procedure.

The biopsy can be done with a needle or through a minor surgery, and it is usually done with local anesthesia (shots to numb the skin). You may or may not also receive sedation (medicines to help you be calm and comfortable). The study doctor will discuss with you the safest method and location to perform the biopsy.

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How often do you assess my tumor?
Your tumor will be assessed every 8 weeks during the first year, and then every 12 weeks thereafter. This includes scans and measurement of skin lesions. Bone scans will be carried out every 24 weeks, if needed.
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How long do study visits last?
Most study visits last for about 2 hours. There will be one or more longer visits which will last about 12 hours. You will be given information in advance on which study visits will take longer.
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Will I be reimbursed for any clinical trial-related costs?
You may be reimbursed for any reasonable expenses that you may have as a result of taking part in this clinical trial. This may include parking, meals, or other travel-related expenses.
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