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Study of Camizestrant plus Ribociclib as First‑Line Treatment for Patients with ER‑Positive, HER2‑Negative Advanced 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

The study focuses on Breast Cancer that is classified as ER-positive, HER2-negative, meaning the cancer cells grow in response to estrogen but do not have excess HER2 protein. The treatment being tested combines two oral medicines, a tablet called Camizestrant taken once daily and a second tablet called Ribociclib also taken daily.

The purpose of the study is to determine how effectively this drug combination can delay the need for additional cancer therapy. Participants receive the study tablets for up to two years while attending regular check‑ups where doctors monitor health, side effects, and any changes in the cancer. Safety is closely watched through routine tests and reporting of any adverse effects.

The research process

The trial runs in 9 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    First dose of study medication

    The first administration of the study drugs marks the start of participation in the trial.

    On this day you will receive camizestrant 75 mg in a film‑coated tablet and ribociclib 600 mg to be taken by mouth.

  2. Step 2

    Daily intake of camizestrant

    You will take one tablet of camizestrant 75 mg each day as instructed by the study team.

    The medication is taken orally and should be swallowed with water.

  3. Step 3

    Daily intake of ribociclib

    You will take the prescribed amount of ribociclib 600 mg each day by mouth.

    The exact timing and any rest periods will be explained by the study physician.

  4. Step 4

    Regular monitoring visits

    You will attend scheduled appointments to allow the study team to assess how the treatment is working and to check for side effects.

    During these visits the doctor may perform physical examinations, review laboratory results, and request imaging studies to evaluate disease status.

  5. Step 5

    Reporting side effects

    Any new symptoms, discomfort, or changes in health should be reported promptly to the study staff.

    These reports help determine the safety of the treatment.

  6. Step 6

    Continuation of treatment

    You will continue taking both medications until the study protocol advises stopping, which may occur if the disease progresses, if unacceptable side effects arise, or for any other reason determined by the physician.

  7. Step 7

    Assessment of primary outcome (ttnt)

    The trial measures ttnt (time to next treatment), which is the period from the first dose until the start of any new cancer therapy or death.

    The primary goal is to determine the proportion of participants who remain free of a new treatment for two years.

  8. Step 8

    Assessment of secondary outcomes

    The study also records ttd (time to discontinuation), which is the time from the first dose until stopping camizestrant or death.

    Progression‑free survival (pfs) is measured as the time from the first dose until disease progression or death, based on standard imaging criteria.

    The incidence of serious side effects (grade 3 or higher) is tracked during the first six months of treatment.

    Overall safety is evaluated through regular checks of vital signs, laboratory tests, and other diagnostic assessments.

  9. Step 9

    Study completion

    The trial continues until the participant reaches the defined endpoints, completes the required follow‑up period, or withdraws consent.

    Final data are collected to determine the effectiveness and safety of the combined therapy.

Who can join the trial?

12 criteria

  • Be able to sign a written informed consent form, which means you understand the study and agree to take part.
  • Be at least 18 years old (or meet the minimum age allowed locally) and be either female or male.
  • Have a breast cancer diagnosis that is estrogen receptor positive (ER+) and HER2‑negative (HER2-), confirmed by lab testing of your tumor tissue, and your cancer cannot be cured with surgery or radiation aimed at cure.
  • Not have received any systemic anti‑cancer medicines (drugs that travel through the bloodstream) for your current recurrent or metastatic ER+ breast cancer.
  • Either have newly diagnosed stage 4 disease or a recurrence after early‑stage disease that was treated with standard hormone therapy, with at least 12 months since your last dose of an aromatase inhibitor (AI) and no cancer growth during that time, and you must wait 2 weeks after stopping tamoxifen before randomisation.
  • Have an ECOG performance status of 0 or 1, meaning you are fully active (0) or able to do light work but not strenuous activity (1).
  • Have adequate function of major organs (heart, liver, kidneys, etc.) and bone marrow (the tissue that makes blood cells).
  • Follow birth‑control rules if you could become pregnant or could cause a pregnancy in a partner:
    • Women of child‑bearing potential must use a highly effective contraceptive method from screening until 4 weeks after stopping the study drug and have a negative pregnancy test before the first dose.
    • Women who are post‑menopausal (no periods for at least 12 months) meet the criteria if they are 60 years or older, or under 60 with lab tests showing post‑menopausal hormone levels, or have had both ovaries removed or confirmed ovarian failure.
    • Pre‑ or peri‑menopausal women can join if they agree to take a monthly LHRH agonist (such as goserelin or leuprorelin [leuprolide]) and continue it for the whole study.
    • Male partners of women who could become pregnant must use a condom plus spermicide (or condom alone where spermicide is not available) throughout the study period.
    • Male participants must be surgically sterile or use an acceptable contraceptive method, must not donate or bank sperm, and may also need a monthly LHRH agonist unless they have had an orchiectomy.

Who cannot join the trial?

9 criteria

  • People who are not supposed to receive endocrine (hormone) therapy together with the medicine ribociclib, which is a CDK4/6 inhibitor that blocks proteins helping cancer grow.
  • People whose cancer is not advanced and cannot be removed by surgery, or whose cancer is only in the bone with dense hardening areas called sclerotic/osteoblastic bone lesions as seen on standard scans.
  • People who have cancer that has spread to internal organs (visceral spread) causing symptoms and may lead to serious, life‑threatening problems soon, or who have pulmonary lymphangitis (cancer spread in the lung’s lymph vessels).
  • People with ongoing side effects from previous treatments that affect parts of the body other than blood, and are moderate to severe (greater than CTCAE Grade 2). CTCAE is a system doctors use to grade side effects.
  • People who have a current infection such as tuberculosis, hepatitis B (HBV), or hepatitis C (HCV). Hepatitis refers to a liver infection.
  • People who have tested positive for HIV (the virus that attacks the immune system), unless they meet special medical criteria.
  • People with important heart rhythm problems that affect the way electrical signals travel in the heart (heart conduction patterns). Having a pacemaker or well‑controlled atrial fibrillation (irregular heartbeat) does not exclude you.
  • People who have ongoing low blood pressure that causes symptoms (hypotension).
  • Women who are pregnant, breastfeeding (lactating), or who are not willing to use a highly effective method of birth control (contraception).
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Investigated drugs

  • Camizestrant

    is an oral tablet that works by breaking down estrogen receptors in breast cancer cells. By removing these receptors, the drug helps stop the cancer cells from growing when they rely on estrogen. In this study, camizestrant is being tested as part of the first treatment for patients whose breast cancer is estrogen‑receptor positive and HER2‑negative.

  • Ribociclib

    is an oral medication that blocks proteins called CDK4 and CDK6, which are needed for cancer cells to divide and multiply. By inhibiting these proteins, ribociclib helps slow down the growth of the tumor. In the trial, ribociclib is given together with camizestrant to see if the combination works better than either drug alone for treating advanced estrogen‑receptor positive, HER2‑negative breast cancer.

What is already known about the treatment

  • Camizestrant

    Camizestrant is taken as a film‑coated tablet swallowed by mouth, usually 75 mg per dose. It is still an investigational drug being studied in clinical trials and is not yet approved for general use. The medicine is being tested for treating advanced breast cancer that has estrogen receptors but no HER2 protein. It works by attaching to the estrogen receptor and causing it to be broken down, which helps stop cancer cells from growing, and it belongs to the class of oral selective estrogen receptor degraders (SERDs).

  • Ribociclib

    Ribociclib is taken as an oral tablet, typically 600 mg once daily. It is an approved medication that is already used in standard breast‑cancer treatment. The drug is used for estrogen‑receptor‑positive, HER2‑negative advanced breast cancer, often together with hormone therapy. It blocks the activity of proteins called CDK4 and CDK6 that control cell division, so it belongs to the class of CDK4/6 inhibitors.

Investigated diseases

Breast Cancer - Breast cancer is a condition where cells in the breast begin to grow without control. It usually starts in the milk‑producing ducts or the glandular tissue that makes milk. The tumor can enlarge and invade nearby breast tissue as it develops. Cancer cells may spread through the lymphatic system or bloodstream to regional lymph nodes and distant organs such as bone, liver, lung, or brain. As the disease progresses, more areas of the body become involved, leading to a broader distribution of cancer cells.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-523444-12-00Protocol codeD8532C00008Estimated enrolment149 patientsSponsorAstraZeneca AB

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