Skip to content
Clinical Trials – home

Rare diseases

Investigational molecules

Locations

Our offerNewsroom

Recruiting

Study of PF-07248144 and fulvestrant in adults with hormone receptor-positive, HER2-negative advanced or metastatic breast cancer who had progression after CDK4/6 inhibitor therapy

Verified siteRegistered drugNo placebo
Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

What is this trial about?

A plain-language summary of the goals, design and what participants do

This study focuses on advanced/metastatic breast cancer that is hormone receptor-positive and HER2-negative. The study will test a new medication called PF-07248144 used together with fulvestrant in patients whose cancer has grown after previous treatment. This type of breast cancer depends on hormones to grow and has already spread to other parts of the body.

The treatment will involve taking PF-07248144 tablets by mouth along with fulvestrant injections into the muscle. Some patients will receive this combination, while others will receive different standard treatments such as everolimus or exemestane. The purpose is to determine if the combination of PF-07248144 and fulvestrant works better than currently available treatments in stopping the cancer from growing.

The study will last for up to 24 months. During this time, patients will have regular check-ups to monitor their health and see how well the treatment is working. Doctors will use special scans to measure if tumors are shrinking, staying the same size, or growing. They will also keep track of any side effects that patients may experience during the treatment.

The research process

The trial runs in 4 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial assessment

    Your eligibility for the trial will be confirmed through medical examination and review of your breast cancer diagnosis, which must be hormone receptor-positive and HER2-negative

    You must be at least 18 years old and have advanced or metastatic breast cancer that cannot be treated with surgery or radiation therapy

    Your previous treatments will be reviewed to confirm you have received prior CDK4/6 inhibitor therapy

    A tumor tissue sample will be required for analysis

  2. Step 2

    Treatment assignment

    You will be randomly assigned to one of two treatment groups:

    Group A: You will receive PF-07248144 tablets taken by mouth plus fulvestrant given as an injection into the muscle

    Group B: You will receive the investigator's choice of therapy

  3. Step 3

    Treatment period

    Your treatment will continue until your disease progresses or you experience unacceptable side effects

    Regular assessments will monitor your response to treatment using imaging scans

    Blood samples will be collected to measure drug levels in your body

    Your health status and any side effects will be monitored throughout the study

  4. Step 4

    Follow-up period

    After completing or stopping treatment, you will continue to be monitored for survival status

    The study is expected to continue until January 2027

    Your participation may end earlier if your disease progresses or you experience unacceptable side effects

Who can join the trial?

9 criteria

  • Must be at least 18 years old when joining the study
  • Must have confirmed HR-positive HER2-negative breast cancer that has spread locally or to other parts of the body (metastatic), and cannot be treated with surgery or radiation therapy alone
  • Must have previously received treatment with CDK4/6 inhibitor (a type of cancer medication) in one of these situations:
    • Combined with hormone therapy for advanced/metastatic breast cancer, or
    • As additional treatment with hormone therapy where cancer returned within 12 months after stopping CDK4/6 inhibitor
    • Must be able to provide a sufficient tumor tissue sample that has been preserved in a special way (FFPE tissue specimen)
    • Must have cancer that can be measured by scans, or cancer that only affects the bones
    • Must have good overall physical function, measured by ECOG Performance Status of:
      • 0 (fully active) or
      • 1 (restricted in physically strenuous activity but able to walk and do light work), or
      • 2 (able to walk and care for self) may be considered if other health conditions are satisfactory

Who cannot join the trial?

14 criteria

  • Prior treatment with any CDK4/6 inhibitor (medications that block specific proteins involved in cell growth)
  • Active brain metastases (cancer that has spread to the brain) that are untreated or unstable
  • History of other cancer types within the last 3 years, except for adequately treated non-melanoma skin cancer or cervical cancer in situ
  • Significant heart conditions, including:
    • Uncontrolled high blood pressure
    • Unstable heart rhythm problems
    • Heart attack within the past 6 months
    • Heart failure with symptoms
    • Severe liver problems or abnormal liver function tests
    • Known hypersensitivity (severe allergic reaction) to fulvestrant or any of the study medications
    • Participation in another clinical trial within 28 days before starting this study
    • Any serious medical condition that could interfere with study participation
    • Pregnancy or breastfeeding
    • Unable or unwilling to use effective contraception during the study period
    • Any psychological, social, or geographical condition that would prevent regular follow-up visits
Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

Tell us about your condition – we search every trial in Europe and connect you with the right site.

We usually reply within a few days

Verified sites

All sites with verified contact details – recruitment status may not be available; ask directly

Trial locations

Where you can join this trial

Countries are shaded by recruitment status. Click a recruiting country to ask about joining there.

Recruiting
Not finding your country?

Not sure what to do next?

Joining a clinical trial can seem overwhelming. We guide you step by step, so you know exactly what to expect and how we support you through the process.

See the full process and FAQ

Investigated drugs

PF-07248144 is an investigational medication being studied for treating breast cancer. It's being tested in combination with other treatments in patients whose cancer has progressed after previous therapy. As this is a new drug in development, it's currently known by its code name. Fulvestrant is a hormone therapy medication used to treat breast cancer. It works by blocking the effects of estrogen, which can help slow or stop the growth of certain types of breast cancer cells. It's commonly used in patients with hormone receptor-positive breast cancer. Investigator's Choice of Therapy (ICT) refers to standard treatment options that doctors may choose for their patients based on individual needs. This is not a specific medication but rather represents various established treatment options that may be selected by the treating physician.

What is already known about the treatment

  • PF-07248144

    An investigational drug being studied in combination with fulvestrant for treating hormone receptor-positive, HER2-negative advanced/metastatic breast cancer. This medication is currently in Phase 3 clinical trials, specifically targeting patients whose disease has progressed after prior CDK4/6 inhibitor therapy. The drug is being evaluated for its potential to improve progression-free survival in breast cancer patients, though its specific mechanism of action is not publicly disclosed in the current trial data.

  • Fulvestrant

    An injectable estrogen receptor antagonist administered intramuscularly, used in the treatment of hormone receptor-positive metastatic breast cancer. It works by binding to and degrading estrogen receptors, thereby blocking the effects of estrogen on breast cancer cells. This medication belongs to the class of selective estrogen receptor degraders (SERDs) and is commonly used in combination therapy for advanced breast cancer treatment.

Investigated diseases

Hormone Receptor-Positive HER2-Negative Breast Cancer - A type of breast cancer where cancer cells have receptors for estrogen and/or progesterone hormones but lack excess HER2 protein on their surface. This is the most common form of breast cancer, where tumor growth is driven by female hormones. The cancer begins in the breast tissue and can develop from cells lining the milk ducts or the milk-producing lobules. As it advances to metastatic stage, cancer cells can spread beyond the breast to other parts of the body through lymphatic system or bloodstream. The disease typically develops slowly compared to other breast cancer types.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-520566-22-00Protocol codeC4551002Estimated enrolment400 patientsSponsorPfizer Inc.

sourced from the EU Clinical Trials Register and site verification

Want to learn more about this trial or check if you can participate?

Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

Tell us about your condition – we search every trial in Europe and connect you with the right site.