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Study of PF-07220060 and Letrozole for Adults with HR-Positive, HER2-Negative Advanced Breast Cancer Without Prior Treatment

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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 Advanced/Metastatic Breast Cancer. This form of cancer has spread beyond the breast to other parts of the body. The study is specifically looking at patients with HR-positive and HER2-negative breast cancer. These terms refer to the presence of certain receptors on the cancer cells that can influence how the cancer grows and responds to treatment.

The purpose of the study is to compare the effectiveness of a new medicine called PF-07220060 when used in combination with another drug called letrozole, against a group of medicines known as CDK4/6 inhibitors (which include abemaciclib, palbociclib, and ribociclib) also used with letrozole. Letrozole is a medication that helps to lower estrogen levels in the body, which can slow the growth of certain types of breast cancer. CDK4/6 inhibitors are a class of drugs that work by interfering with cancer cell division, potentially slowing down or stopping the growth of cancer.

Participants in the study will be randomly assigned to receive either the combination of PF-07220060 and letrozole or one of the CDK4/6 inhibitors with letrozole. The study will last for a period of up to 36 months, during which the progress of the disease will be closely monitored. The main goal is to see which treatment combination is more effective in delaying the progression of the cancer. This study is open to individuals over the age of 18 who have not received any prior systemic treatment for their 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 randomly assigned to one of two groups. This process is called randomization and ensures that each participant has an equal chance of being placed in either group.

  2. Step 2

    Treatment group assignment

    Participants in Arm A will receive a combination of two medications: PF-07220060 and letrozole. Both medications are taken orally, meaning they are swallowed in the form of pills or capsules.

    Participants in Arm B will receive a combination of a CDK4/6 inhibitor (either abemaciclib, palbociclib, or ribociclib) and letrozole. The specific CDK4/6 inhibitor will be chosen by the study investigator.

  3. Step 3

    Medication administration

    The medications are to be taken as prescribed by the study doctor. The exact dosage and frequency will be provided by the healthcare team and must be followed carefully.

    Participants will continue taking the medications for the duration of the study unless advised otherwise by the study doctor.

  4. Step 4

    Regular health assessments

    Throughout the study, participants will undergo regular health assessments. These assessments are designed to monitor the participant's health and the effectiveness of the treatment.

    The assessments may include physical exams, blood tests, and imaging tests. The frequency and type of assessments will be determined by the study protocol.

  5. Step 5

    Monitoring and follow-up

    Participants will be closely monitored for any side effects or changes in their condition. It is important to report any new symptoms or concerns to the study team immediately.

    Follow-up visits will be scheduled to ensure the participant's safety and to gather data on the treatment's effectiveness.

  6. Step 6

    End of study participation

    The study is expected to continue until February 19, 2038. Participants will be informed about the end of their participation and any necessary steps to transition out of the study.

    Upon completion, participants may receive information about the study results and any potential next steps regarding their treatment.

Who can join the trial?

8 criteria

  • Must be at least 18 years old (or the minimum age of consent according to local laws) at the time of screening.
  • If you are a premenopausal or perimenopausal female, or a male participant, you must receive treatment with an LHRH agonist before the first dose of the study treatment and continue throughout the study. An LHRH agonist is a type of medication that affects hormone levels.
  • Must have a confirmed diagnosis of breast cancer that is either locally advanced or has spread to other parts of the body (metastatic), and cannot be treated with surgery or radiation to cure it.
  • Must have a tumor that is positive for estrogen receptor (ER) and/or progesterone receptor (PR). These are proteins found in some breast cancer cells that can attach to the hormones estrogen and progesterone, which can fuel the growth of the cancer.
  • Must have a tumor that is HER2-negative. HER2 is a protein that can promote the growth of cancer cells. In HER2-negative breast cancer, the cancer cells do not have high levels of this protein.
  • Must not have received any previous systemic anticancer treatment for their locally advanced or metastatic breast cancer.
  • Must have either measurable disease or non-measurable disease that is only in the bones, as defined by specific medical guidelines (RECIST v1.1).
  • Must have an ECOG Performance Status of 0, 1, or 2. This is a scale used to assess how a patient's disease is progressing, including their level of functioning and ability to care for themselves.

Who cannot join the trial?

7 criteria

  • Patients with other types of cancer besides advanced/metastatic breast cancer cannot participate.
  • Patients who have had a different treatment for their breast cancer that is not part of the study cannot participate.
  • Patients with serious medical conditions that could interfere with the study cannot participate.
  • Patients who are pregnant or breastfeeding cannot participate.
  • Patients who are unable to follow the study procedures cannot participate.
  • Patients who have allergies to the study medications cannot participate.
  • Patients who have participated in another clinical trial recently cannot participate.
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Investigated drugs

  • PF-07220060

    is an experimental medication being tested in this clinical trial. It is being studied to see how well it works when used together with another medication called letrozole. The goal is to find out if this combination can help slow down the progression of advanced or metastatic breast cancer that is hormone receptor-positive and HER2-negative. This means the cancer grows in response to hormones but does not have a protein called HER2 on its surface.

  • Letrozole

    is a medication that is already used to treat certain types of breast cancer. It works by lowering the levels of estrogen in the body, which can help slow or stop the growth of some breast cancers that need estrogen to grow. In this trial, letrozole is used in combination with other medications to see if it can improve outcomes for patients with advanced or metastatic breast cancer.

  • Abemaciclib

    is one of the medications that can be chosen by the investigator in this study. It is a type of drug known as a CDK4/6 inhibitor. These inhibitors work by blocking certain proteins in cancer cells, which can slow down or stop the growth of the cancer. In this trial, abemaciclib is used together with letrozole to see if this combination can help patients with advanced or metastatic breast cancer.

  • Palbociclib

    is another option for the investigator to choose in this study. Like abemaciclib, it is a CDK4/6 inhibitor. It helps to stop cancer cells from dividing and growing. When used with letrozole, the study aims to determine if this combination can be effective in treating advanced or metastatic breast cancer.

  • Ribociclib

    is also a CDK4/6 inhibitor that can be selected by the investigator in this trial. It works similarly to abemaciclib and palbociclib by targeting specific proteins in cancer cells to prevent them from growing. The trial is testing whether using ribociclib with letrozole can help improve the treatment of advanced or metastatic breast cancer.

What is already known about the treatment

  • PF-07220060

    This medication is administered orally and is currently being studied in clinical trials for its effectiveness in treating advanced or metastatic breast cancer. It is not yet widely used in medical practice, as it is still under investigation. The main therapeutic indication for PF-07220060 is hormone receptor-positive, HER2-negative advanced or metastatic breast cancer. At the molecular level, it works by targeting specific proteins involved in cancer cell growth, aiming to slow down or stop the progression of the disease. PF-07220060 is classified as a targeted therapy, which means it specifically targets cancer cells while minimizing damage to normal cells.

  • Letrozole

    Letrozole is an oral medication that is well-established in medical practice for the treatment of hormone receptor-positive breast cancer, particularly in postmenopausal women. It is used to treat advanced or metastatic breast cancer by lowering estrogen levels in the body, which helps slow or stop the growth of certain types of breast cancer cells that need estrogen to grow. Letrozole is classified as an aromatase inhibitor, a type of hormone therapy that reduces the production of estrogen, thereby inhibiting the growth of hormone-sensitive tumors.

Investigated diseases

Advanced/Metastatic Breast Cancer – Advanced/Metastatic Breast Cancer is a stage of breast cancer where the disease has spread beyond the breast and nearby lymph nodes to other parts of the body. This progression often involves the bones, liver, lungs, or brain. The cancer cells in metastatic breast cancer are the same type as the original breast cancer. As the disease advances, it can cause symptoms related to the areas affected, such as bone pain or difficulty breathing. The progression of the disease can vary, with periods of stability and periods of growth. The spread of cancer cells occurs through the bloodstream or lymphatic system.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2024-512925-95-00Protocol codeC4391024Estimated enrolment1 020 patientsSponsorPfizer Inc.

sourced from the EU Clinical Trials Register and site verification

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