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Study of Camizestrant and CDK4/6 Inhibitor for Patients with Advanced Breast Cancer with ESR1 Mutation

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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 treatments for Estrogen Receptor-Positive, HER2-negative Advanced Breast Cancer. The study will compare the effectiveness of a new treatment combination, Camizestrant (also known as AZD9833) plus a CDK4/6 inhibitor, against the current standard treatment of an Aromatase Inhibitor (such as Letrozole or Anastrozole) plus a CDK4/6 inhibitor. The purpose of the study is to determine if switching to the new treatment combination is more effective in patients who have a specific genetic change called the ESR1 mutation and have not experienced disease progression during their initial treatment.

Participants in the study will be randomly assigned to receive either the new treatment combination or continue with the current standard treatment. The study will be conducted in a double-blind manner, meaning neither the participants nor the researchers will know which treatment is being given to each participant. This helps ensure that the results are not biased. The study will last for a period of up to 77 weeks, during which participants will take the medications orally in the form of tablets or capsules. Some participants may receive a placebo, which looks like the real medication but does not contain the active substance.

The main goal of the study is to assess the progression-free survival, which is the time during which the cancer does not get worse. Secondary goals include evaluating overall survival, response rates to the treatment, and the time until further cancer treatment is needed. The study will also monitor the concentration of Camizestrant in the blood and assess changes in quality of life using specific questionnaires. This trial aims to provide valuable information on whether the new treatment combination can offer better outcomes for patients with this type of breast cancer.

The research process

The trial runs in 5 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, participation begins with a confirmation of eligibility. This includes a diagnosis of estrogen receptor-positive, HER2-negative advanced breast cancer, and the presence of an ESR1 mutation.

    Initial treatment involves continuing with an aromatase inhibitor, either letrozole or anastrozole, combined with a CDK4/6 inhibitor.

  2. Step 2

    Randomization

    Participants are randomly assigned to one of two groups. One group will switch to AZD9833, a next-generation oral SERD, combined with a CDK4/6 inhibitor. The other group will continue with the current aromatase inhibitor and CDK4/6 inhibitor.

  3. Step 3

    Treatment administration

    For those switching to AZD9833, the medication is taken orally. The specific dosage and frequency will be provided by the study team.

    Participants continuing with the aromatase inhibitor will maintain their current regimen, which includes oral administration of letrozole or anastrozole, along with the CDK4/6 inhibitor.

  4. Step 4

    Monitoring and assessments

    Regular visits are scheduled to monitor health status and treatment effects. This includes laboratory tests and other necessary procedures.

    Progression-free survival is assessed to determine the effectiveness of the treatment. This involves tracking the time from randomization until disease progression or death.

  5. Step 5

    End of study participation

    The study is estimated to conclude by November 2027. Participants will continue their assigned treatment until the study ends or until disease progression is observed.

    Upon completion, further treatment options will be discussed based on individual health status and study outcomes.

Who can join the trial?

7 criteria

  • The patient must have a confirmed diagnosis of a type of breast cancer called adenocarcinoma, which has spread to nearby areas or other parts of the body and cannot be treated with surgery or radiation to cure it.
  • The patient must have a diagnosis of breast cancer that is estrogen receptor-positive (ER+) and HER2-negative, confirmed by a local lab. This means the cancer grows in response to estrogen but does not have too much of a protein called HER2.
  • The patient must currently be receiving treatment with a type of medication called an AI (aromatase inhibitor) like letrozole or anastrozole, along with a CDK4/6 inhibitor, with or without another treatment called LHRH, as their first hormone-based treatment for advanced cancer.
  • The patient must have an Eastern Cooperative Oncology Group performance status of 0 or 1, which means they are fully active or have some symptoms but can still carry out light work.
  • The patient must have a specific change in their DNA called ESR1m, which will be checked through a blood test.
  • The patient must be willing and able to attend scheduled visits, follow the treatment plan, and undergo lab tests and other procedures required by the study.
  • The patient must have organs and bone marrow that are working well enough to participate in the study.

Who cannot join the trial?

5 criteria

  • Patients who have a different type of breast cancer than Estrogen Receptor-Positive, HER-2 negative Advanced Breast Cancer cannot participate. This means the cancer must be sensitive to estrogen and not have a protein called HER-2.
  • Patients who are not within the specified age range for the study cannot participate. The study has specific age requirements.
  • Patients who are not part of the specified clinical trial groups cannot participate. This means the study is looking for specific characteristics in participants.
  • Patients who are not female or male cannot participate. The study includes both genders.
  • Patients who are considered part of a vulnerable population cannot participate. This means people who might need special protection or care.
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Investigated drugs

  • AZD9833

    is a new type of oral medication being tested in this study. It is designed to block certain receptors in the body that can help cancer cells grow. This medication is being studied to see if it can help patients with a specific type of breast cancer that has a detectable ESR1 mutation. The goal is to see if switching to this medication can improve the time patients live without their disease getting worse.

  • CDK4/6 Inhibitor

    is a type of medication that helps stop cancer cells from dividing and growing. It is often used in combination with other treatments to help control the growth of cancer. In this study, it is used alongside other medications to see if it can help improve outcomes for patients with breast cancer.

  • Letrozole

    is a medication that lowers estrogen levels in the body. It is commonly used to treat breast cancer in postmenopausal women by slowing or stopping the growth of cancer cells that need estrogen to grow.

  • Anastrozole

    is another medication that reduces estrogen levels in the body. Like letrozole, it is used to treat breast cancer in postmenopausal women by targeting cancer cells that rely on estrogen for growth.

What is already known about the treatment

AZD9833 – This medication is administered orally and is currently being studied in clinical trials for its effectiveness in treating estrogen receptor-positive, HER-2 negative advanced breast cancer. It is a next-generation oral selective estrogen receptor degrader (SERD) that works by binding to estrogen receptors and promoting their degradation, thereby reducing the growth of cancer cells that rely on estrogen. AZD9833 is classified as a hormonal therapy and is being evaluated for its potential to improve progression-free survival in patients with specific genetic mutations.

Investigated diseases

Estrogen Receptor-Positive, HER-2 Negative Advanced Breast Cancer – This type of breast cancer is characterized by the presence of estrogen receptors on the surface of the cancer cells, which means the cancer cells may receive signals from estrogen that could promote their growth. It is also HER-2 negative, indicating that the cancer cells do not have an excess of the HER-2 protein on their surfaces. This form of breast cancer is considered advanced when it has spread beyond the breast to other parts of the body. The progression of this disease can vary, but it typically involves the growth and spread of cancer cells to other organs. The disease may progress slowly or rapidly, depending on various factors, including the biology of the cancer and the patient's overall health. Monitoring the progression is crucial to managing the disease effectively.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2023-503990-39-00Protocol codeD8534C00001Estimated enrolment300 patientsSponsorAstraZeneca AB

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