Each day we learn more about advanced and metastatic breast cancer, and researchers continue to work on ways to treat it. If you have ER-positive, HER2-negative advanced or metastatic breast cancer, the TACTIVE-U study may be an option for you.

The TACTIVE-U study is researching if a study medicine (vepdegestrant, also known as ARV-471) is safe and effective when given with other medicines in people with advanced or metastatic breast cancer.

Who may participate

Thank you for considering the TACTIVE-U study. Joining a clinical trial is an important and personal decision. By volunteering in clinical research, you can make a difference.

You may be able to take part in the TACTIVE-U study if you:

  • Are 18 years old or older
  • Have advanced or metastatic (may have spread to other organs) breast cancer that:
    • Is sensitive to hormonal therapy (it is called estrogen receptor positive)
    • Does not express human epidermal growth factor receptor 2 protein (it is called HER2 negative)
    • Cannot be fully treated by surgery
    • Is no longer responding to previous treatments

If you think this study could be right for you, you can review the details with the study team who can answer any questions you may have. If you choose to participate, you will sign the informed consent document and continue with screening to confirm whether you meet all the eligibility criteria and are able to participate.


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

Get started — See if you may qualify

A first step as you consider participating in these studies is to answer a 5-minute online questionnaire about your health and medical history. Please answer the questions to the best of your ability and to the extent you feel comfortable. You can skip questions, however, providing more information will help our clinical trial finder, a secure system powered by Leal Health, to see if you may be eligible for a study based on your health and medical history.

By entering your information into the online questionnaire, you are creating an account and profile with Leal Health which will allow you to see if you may be eligible for any breast cancer studies. At the end of the online questionnaire, you will be able to see how many studies you may potentially qualify for. By providing your contact information, you are providing permission for a member of the Leal Health Patient Support Team to contact you and discuss next steps. They will be available to help you navigate the process of finding a study, answering your questions, and helping you prepare to talk with your oncologist.

If you would like to be referred to a nearby clinic, your Patient Support Team Member will ask you to provide written permission for Leal Health to share your contact information with the study team at the clinic who will then contact you and will likely ask you to come in for an appointment. Only the study team can determine if you meet all the study’s eligibility criteria and are able to enroll in the study.

If it appears that you may be eligible to participate in a Pfizer breast cancer study after completing the online questionnaire, you will see the list of potential Pfizer sponsored studies first. If there are no Pfizer sponsored studies in the list, you can provide permission for Leal Health to continue searching for an appropriate study sponsored by another organization.

We encourage you to review Leal Health’s privacy policy (linked below) before you complete the online questionnaire. Your answers including any personal information will be kept confidential by Leal Health throughout the prescreening process.

Your answers to the online questionnaire will only be linked to you if your responses indicate that you may be eligible to participate in a study and you choose to share your contact information with that study team. Pfizer study team members and our partners will have access to reports containing aggregated (combined) data that will not be directly linked back to you.

What to expect

If you’ve met all eligibility criteria and agree to take part, you will be given the study medicine (ARV-471) and another medicine for you to take by mouth at home.

You may visit your study doctor every week to four weeks. A member of the study site will be able to provide more details around the frequency of your study visits. What happens at each study visit will vary, but your health will be monitored and may include a physical exam, electrocardiogram, imaging scans (e.g. CT scan) and blood sample collection.

About one month after your last dose of study medicine, you will attend a final visit so the study team can observe your health.

Length of study treatment

The time you can expect to be in the study depends upon a few things, including how you tolerate the study drugs, how your cancer responds, and your personal choice

Number of study visits


Safety follow up

You will be asked to attend a visit about a month after your last dose of the study medicine

Frequently asked questions

How should I take study treatments?

If you receive ARV-471 and

  • Abemaciclib: You need to take ARV-471 and abemaciclib at the same time in the morning with food. ARV-471 should be taken first. You need to take abemaciclib alone also in the evening with or without food, and this will be repeated for 28 days.
  • Ribociclib: You need to take ARV-471 and ribociclib at the same time in the morning with food. Ribociclib will be taken on a cycle for 21 days with 7 days off but is only taken alongside ARV-471 in the morning.
  • Samuraciclib: You need to take ARV-471 in the morning with food. Samuraciclib may be taken at any time during the day with or without food.
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Do I need to provide tumor samples during the study?

You will be asked to provide a sample of your tumor from time of diagnosis or at the time of reappearance of your tumor locally or tumors that have spread to your body after a period of improvement.

There will be an optional (not required) biopsy collected at the end of treatment if you have stopped the treatment 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 (drugs 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.

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How long do study visits last?

Most study visits last for about 1-2 hours. There are some longer visits which will last about 5-6 hours, and a few visits for up to 8 hours. You will be given information in advance on which study visit will take longer.

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View locations for this study

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