Despite advances in cancer treatments overall, more options are needed for people with advanced breast cancer. With clinical research we can do this together.

The C4391002 study is a clinical study to learn about three study medicine combinations for people with advanced breast cancer. Participants will take one of the study medicine combinations, and their experiences will be compared to help determine how safe, tolerable and effective the study medicine combinations are.

Who may participate

This study may be an option for you if you:


  • Have HR-positive/HER2-negative breast cancer
  • Are fully or reasonably active
  • Are aged 18 years or older

There are other requirements for participation in this study. Find out more by answering a few questions online or over the phone.


Breast cancer


18 years or older


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.

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

In addition to taking/receiving the study medicine combination, you will be asked to visit the clinic for regular health checks. These include health questions, physical examinations, blood and urine samples, electrocardiograms (ECGs), and imaging scans. These assessments help us to monitor your safety and well-being, and to see how your cancer is responding.

Length of study treatment

Approximately 2 years

Number of study visits

At least 8 visits

Follow up

For at least 28 days after the last dose of study medicine

Frequently asked questions

What is breast cancer?

Breast cancer is a type of cancer that starts in one or both breasts. It occurs most commonly in women, but men can get it too. It accounts for about 1 in 3 of all new female cancers in the United States each year. (Source: American Cancer Society).

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What is advanced breast cancer?

Advanced breast cancer means the cancer has spread. Breast cancer spreads when the cancer cells get into the blood or lymph system and then are carried to other parts of the body.

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What is HR-positive/HER2-negative breast cancer?

Although breast cancer is often thought of as one disease, there are many different types and ways to describe it. For example, a breast cancer is classified as HR-positive if its cells have receptors for the hormones estrogen and progesterone. Cancer tissue is also tested for HER-2 proteins, or receptors, that help control the growth and repair of breast cells. HER-2-negative breast cancers have cells that contain little to no HER-2 protein, so they tend to grow more slowly. Knowing the hormone receptor status of your cancer helps doctors decide how to treat it. (Source: American Cancer Society).

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What are the benefits and risks of the C4391002 study?

Your breast cancer may get better, get worse, or stay the same. Your health will be closely monitored during the study. Participation may help people in the future by increasing our understanding of the study medicines and breast cancer. If your health gets worse, the study team will help you decide what to do, which may mean stopping your participation in the study. Potential risks from taking part in the study may include side effects from taking the study medicine combination; risks or discomforts from study procedures such as blood tests and body scans; risk of allergic reaction to the study medicine.

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How are the study medicines administered?

Participants will take two of the study medicines by mouth. In addition, participants will take a third study medicine. Some participants will take the third study medicine by mouth; others will receive an injection.

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How many people will take part in the study?

There will be approximately 120 participants in this study.

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