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Study of inavolisib, ribociclib, and fulvestrant for patients with advanced hormone-receptor-positive, HER2-negative breast cancer.

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What is this trial about?

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

This study focuses on a type of Advanced Breast Cancer that is Hormone-Receptor-Positive and HER2-Negative. This means the cancer cells grow in response to certain hormones and do not have an excess of a specific protein called HER2. The condition is also Endocrine-Resistant, meaning the cancer has stopped responding to hormone therapy, and it involves a Chromosome 8p Loss, which is a change in the genetic material of the cells. Additionally, the cancer does not have a PIK3CA Mutation, which is a specific change in a gene that often drives cancer growth.

The purpose of the study is to evaluate the effectiveness and safety of a combination of three medications. One group will receive Inavolisib, Ribociclib, and Fulvestrant, while another group will receive a placebo along with Ribociclib and Fulvestrant. Inavolisib and Ribociclib are taken as pills, while Fulvestrant is given as an injection into the muscle.

Participants in the study will be assigned to one of the two treatment groups. Over the course of the study, the combination of drugs will be monitored to see how the cancer responds and to observe any side effects. The study will track how long the cancer stays stable and how long patients live while receiving these treatments.

The research process

The trial runs in 3 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Study entry and medication assignment

    After joining the study, a randomization process occurs. this means a method is used to assign you to one of two different treatment groups by chance, similar to drawing names from a hat.

    You will be assigned to receive either the active treatment group or the placebo group. this study is double-blind, meaning neither you nor the medical staff know which specific treatment is being given during the trial.

  2. Step 2

    Treatment administration

    If assigned to the active treatment group, you will take two types of oral medications: inavolisib at a dose of 9 mg as a film-coated tablet, and ribociclib at a dose of 600 mg. you will also receive an intramuscular injection (an injection into the muscle) of fulvestrant at a dose of 500 mg.

    If assigned to the placebo group, you will take ribociclib at a dose of 600 mg orally and receive the fulvestrant injection of 500 mg into the muscle. instead of the active inavolisib, you will receive a placebo, which is a substance that looks like the medicine but contains no active ingredients.

  3. Step 3

    Monitoring and evaluation

    Throughout the study, the efficacy (how well the treatment works) and safety (the side effects experienced) will be monitored.

    Medical professionals will assess your objective response rate, which is a measure of how much the cancer shrinks or disappears in response to the treatment.

    Various assessments will be performed to track progression-free survival (the length of time during and after treatment that the disease does not get worse), overall survival (the length of time from the start of the study that patients are still alive), and duration of response (how long the cancer remains in response to the treatment).

    Your vital signs (such as blood pressure or heart rate) and clinical laboratory test results (such as blood tests) will be checked to identify any changes from the start of the trial.

    The incidence and severity of adverse events (side effects) will be recorded using standardized scales to understand how the treatments affect your health and daily activities.

Who can join the trial?

7 criteria

  • The patient must be a woman or a man with a confirmed diagnosis of breast cancer that has either spread to other parts of the body or is at an advanced stage where surgery or radiation cannot fully cure it.
  • The cancer must be hormone receptor-positive, which means at least 1% of the cancer cells react to the hormones estrogen or progesterone.
  • The patient must not have undergone any previous systemic therapy, which is medicine that travels through the entire body (like chemotherapy or hormone therapy), to treat their advanced or spreading breast cancer.
  • The patient must have had their cancer get worse while taking endocrine-based treatment (hormone therapy) or within 12 months after finishing such treatment with medications like aromatase inhibitors or tamoxifen.
  • Testing of the tumor tissue must show that the cancer does not have a specific genetic change called a PIK3CA mutation.
  • Testing must confirm the presence of heterozygous loss of chromosome 8p, which is a specific type of missing genetic material on a part of a cell's structure called a chromosome.
  • The cancer must include measurable disease, meaning the tumors are large enough and in locations that allow doctors to clearly track their size using standard medical rules.

Who cannot join the trial?

8 criteria

  • Having metaplastic breast cancer, which is a rare and aggressive type of breast cancer.
  • Receiving radiotherapy, which is a treatment using high doses of radiation to kill cancer cells, within 2 weeks before being assigned to a study group.
  • Being a candidate for cytotoxic chemotherapy, which is a type of strong medicine used to kill fast-growing cells, based on local medical rules.
  • Experiencing a visceral crisis, which is a sudden and severe medical emergency caused by cancer affecting internal organs like the liver or lungs.
  • Having Type 2 diabetes that requires ongoing medication, or having any history of Type 1 diabetes.
  • Having active CNS metastases, which means cancer has spread to the central nervous system (the brain or spinal cord) and is currently growing or causing symptoms.
  • Needing anticonvulsants, which are medicines used to prevent seizures, or corticosteroids, which are powerful anti-inflammatory medicines, to control symptoms of brain cancer.
  • Having any history of leptomeningeal disease or carcinomatous meningitis, which are conditions where cancer cells spread into the fluid surrounding the brain and spinal cord.
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Investigated drugs

  • Inavolisib

    is a medication taken by mouth that is being studied to see if it can help treat certain types of advanced breast cancer by targeting specific pathways in the cells.

  • Ribociclib

    is a pill taken daily that helps to slow down the growth of cancer cells by blocking specific signals that allow the cancer to multiply.

  • Fulvestrant

    is a medication given by injection into the muscle that works by blocking the effects of hormones that certain breast cancers use to grow.

What is already known about the treatment

  • Inavolisib

    This medication is taken as an oral film-coated tablet and is currently being studied in clinical trials for its effectiveness. It is categorized as a PI3K inhibitor, a type of targeted therapy used to treat certain advanced cancers. At a molecular level, it works by blocking a specific protein called PI3K that helps cancer cells grow and survive.

  • Ribociclib

    This drug is administered orally and is an established treatment used primarily for advanced breast cancer. It belongs to a class of drugs known as CDK4/6 inhibitors. It works by blocking specific enzymes that signal cancer cells to divide, thereby slowing down the growth of the tumor.

  • Fulvestrant

    This medication is given as an intramuscular injection and is a well-known treatment in oncology. It is classified as a selective estrogen receptor degrader, which is a type of hormone therapy. It works by attaching to estrogen receptors on cancer cells and causing them to break down, which prevents the cancer from using estrogen to grow.

Investigated diseases

Endocrine-Resistant Hormone-Receptor-Positive, HER2-Negative Advanced Breast Cancer with Chromosome 8p Loss and Without PIK3CA Mutation - This is a type of breast cancer where the cells grow in response to hormones like estrogen or progesterone. It is characterized by a lack of the HER2 protein on the cell surface. Over time, the cancer may stop responding to standard hormone-based therapies. Specific genetic changes, such as the loss of part of chromosome 8, may be present in the tumor cells. This particular form does not have a specific mutation in the PIK3CA gene. The disease progresses as cancer cells continue to multiply and spread within the body.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IITrial ID2025-523013-28-00Protocol codeCO46274Estimated enrolment80 patientsSponsorF. Hoffmann-La Roche AG

sourced from the EU Clinical Trials Register and site verification

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