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Study on the Safety and Antitumor Activity of ARV-471 and Ribociclib in Adults with ER+ Advanced or Metastatic Breast Cancer

Fast replyRegistered drugNo placebo
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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 ER-positive (ER+) and HER2-negative (HER2-) advanced or metastatic breast cancer. This type of cancer is characterized by the presence of estrogen receptors (ER+) and the absence of human epidermal growth factor receptor 2 (HER2-), which can influence how the cancer grows and responds to treatment. The study is investigating a new treatment approach using a medication called ARV-471, also known by its code name PF-07850327, in combination with another medication called ribociclib. ARV-471 is an oral medication designed to target and break down specific proteins in cancer cells, while ribociclib is a medication that helps to slow down or stop the growth of cancer cells.

The purpose of this study is to evaluate the safety and effectiveness of the combination of ARV-471 and ribociclib in treating patients with this specific type of breast cancer. Participants in the study will receive the medications and be monitored for their response to the treatment, as well as any side effects they may experience. The study will be conducted in two phases: Phase 1b will focus on assessing the safety and tolerability of the treatment combination, while Phase 2 will evaluate the antitumor activity, which means how well the treatment works in reducing or controlling the cancer.

Throughout the study, participants will take the medications orally, in the form of film-coated tablets. The study will involve regular check-ups and assessments to monitor the participants' health and the progress of the treatment. The goal is to determine the best dose of ARV-471 when used with ribociclib and to understand how the combination affects the cancer. This research aims to provide valuable information that could lead to improved treatment options for patients with ER+ and HER2- advanced or metastatic breast cancer.

The research process

The trial runs in 6 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, participants will be informed about the trial's purpose, procedures, and potential risks and benefits. Participants will be required to provide informed consent, indicating their understanding and willingness to participate.

  2. Step 2

    Initial assessment

    Participants will undergo an initial assessment to confirm eligibility. This includes a review of medical history, a physical examination, and necessary laboratory tests to ensure the participant meets the study criteria.

  3. Step 3

    Treatment phase 1b

    Participants will begin the treatment phase, receiving a combination of ARV-471 and ribociclib. ARV-471 is an oral medication taken as a film-coated tablet. Ribociclib is also taken orally in the form of Kisqali 200 mg film-coated tablets. The specific dosage and frequency will be determined by the study team based on individual needs and responses.

    The primary goal during this phase is to assess the safety and tolerability of the medication combination. Participants will be closely monitored for any side effects or adverse reactions.

  4. Step 4

    Monitoring and follow-up

    Throughout the trial, participants will have regular follow-up visits. These visits will include physical exams, laboratory tests, and imaging studies to monitor the participant's health and the effectiveness of the treatment.

    Participants will be asked to report any side effects or changes in their condition. The study team will adjust treatment as necessary to ensure participant safety.

  5. Step 5

    Treatment phase 2

    In phase 2, the focus will shift to assessing the clinical antitumor activity of the medication combination. Participants will continue to receive ARV-471 and ribociclib as prescribed.

    The study team will evaluate the response to treatment, including any reduction in tumor size or progression of the disease.

  6. Step 6

    End of study

    Upon completion of the study, participants will undergo a final assessment. This will include a comprehensive evaluation of their health status and any changes observed during the trial.

    Participants will receive information about their treatment outcomes and any further steps or recommendations for their ongoing care.

Who can join the trial?

6 criteria

  • Participants must be 18 years or older at the time of screening.
  • Must have a diagnosis of ER+/HER2- Advanced or Metastatic Breast Cancer, which means the cancer has spread and cannot be removed by surgery to cure it. At least 1% of the cancer cells must test positive for estrogen receptors (ER+) on the most recent tumor biopsy.
  • Must have had at least one and no more than two previous treatments for advanced or metastatic cancer.
  • Must have had one previous treatment with a CDK4/6 inhibitor, a type of cancer drug. If this treatment was stopped permanently due to side effects, the participant is not eligible. If the dose was reduced due to side effects, further evaluation is needed.
  • Must have at least one measurable tumor as defined by specific medical guidelines (RECIST v1.1).
  • Must have an ECOG performance status of 0 or 1, which means the participant is fully active or has some symptoms but does not need bed rest during the day.

Who cannot join the trial?

13 criteria

  • Patients with any other type of cancer that is not **ER+/HER2- Advanced or Metastatic Breast Cancer**.
  • Patients who have not reached the age of 18.
  • Patients who are pregnant or breastfeeding.
  • Patients with severe heart problems.
  • Patients with uncontrolled high blood pressure.
  • Patients with active infections that require treatment.
  • Patients who have had another cancer treatment within the last 4 weeks.
  • Patients with known allergies to the study drugs.
  • Patients with a history of severe allergic reactions.
  • Patients who are unable to swallow pills.
  • Patients with significant liver or kidney disease.
  • Patients with a history of drug or alcohol abuse.
  • Patients who are participating in another clinical trial.
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Investigated drugs

  • Vepdegestrant (ARV-471 / PF-07850327)

    is an experimental medication being studied for its potential to treat advanced or metastatic breast cancer. It works by targeting and breaking down specific proteins in cancer cells, which may help to stop the growth of the cancer. This medication is taken orally, meaning it is swallowed in pill form. In this trial, it is being tested to see how well it works and how safe it is when used in combination with another cancer treatment.

  • Ribociclib

    is a medication used to treat certain types of breast cancer. It works by blocking proteins that help cancer cells grow and divide. By inhibiting these proteins, ribociclib can slow down or stop the progression of cancer. It is also taken orally and is being studied in combination with vepdegestrant to see if the two medications together can be more effective in treating breast cancer than either one alone. The trial aims to understand how these medications interact and their combined effect on cancer cells.

What is already known about the treatment

  • Vepdegestrant (ARV-471 / PF-07850327)

    This medication is taken orally and is currently being studied in clinical trials for its safety and effectiveness in treating advanced or metastatic breast cancer that is positive for estrogen receptors and negative for HER2 receptors. It is a new type of drug called a proteolysis targeting chimera, which works by helping the body break down specific proteins that are involved in cancer growth. Vepdegestrant is being tested in combination with other cancer treatments to see if it can improve outcomes for patients with this type of breast cancer.

  • Ribociclib

    This medication is also taken orally and is already approved for use in treating certain types of breast cancer. It is being studied in combination with vepdegestrant to see if the two drugs together can be more effective. Ribociclib works by blocking proteins called cyclin-dependent kinases, which are involved in cell division, thereby slowing down the growth of cancer cells. It is classified as a CDK4/6 inhibitor and is used to treat hormone receptor-positive, HER2-negative advanced or metastatic breast cancer.

Investigated diseases

ER+/HER2- Advanced or Metastatic Breast Cancer – This type of breast cancer is characterized by the presence of estrogen receptors (ER+) and the absence of human epidermal growth factor receptor 2 (HER2-) on the cancer cells. It is considered advanced or metastatic when it has spread beyond the breast to other parts of the body. The disease progresses as cancer cells grow and multiply, potentially affecting organs such as bones, liver, lungs, or brain. The growth of these cancer cells is often driven by hormones, particularly estrogen. Over time, the cancer may become more aggressive and resistant to hormone therapies. The progression can vary significantly among individuals, with some experiencing slow growth and others facing rapid advancement.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase ITrial ID2022-502231-19-00Protocol codeC4891023Estimated enrolment35 patientsSponsorPfizer Inc.

sourced from the EU Clinical Trials Register and site verification

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