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Study of inavolisib and fulvestrant for patients with PIK3CA-mutated, hormone receptor-positive, HER2-negative advanced or metastatic 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 involves people with breast cancer that has specific features. The cancer must be HR-positive, which means it grows in response to certain hormones, and HER2-negative, which refers to a protein that is not present in high amounts in this type of cancer. Additionally, the cancer must have a change in a gene called PIK3CA, which is a mutation that can affect how cancer cells grow. The cancer must have spread to other parts of the body or grown in a way that cannot be removed by surgery. The study will test a medication called inavolisib, which is also known by its code name GDC-0077, given together with another medication called fulvestrant. Two different dose amounts of inavolisib will be compared to see which one works better and is safer when combined with fulvestrant.

The purpose of this study is to evaluate how well inavolisib works and how safe it is when given at two different dose levels in combination with fulvestrant. The study will look at whether the cancer shrinks or disappears in response to treatment, and will pay special attention to certain side effects that can happen with inavolisib, such as high blood sugar levels, mouth sores, and diarrhea. People in the study will be randomly assigned to receive either a 9 milligram dose or a 6 milligram dose of inavolisib each day, along with fulvestrant. The study is designed for people who have already received treatment with a combination of a type of medication called a cyclin-dependent kinase 4/6 inhibitor and hormone therapy, but whose cancer has continued to grow.

During the study, participants will receive their assigned treatment and will be monitored regularly to see how the cancer responds and to check for any side effects. The study will measure things like how many people have their cancer shrink, how long the cancer stays under control, and how long it takes for the cancer to respond to treatment. Participants will also be asked to report symptoms they experience through questionnaires to help understand how the treatment affects their daily life and well-being. The treatment can continue for up to two years, and the entire study is expected to last until mid-2028.

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

    Random assignment to treatment group

    Upon joining the study, you will be randomly assigned to one of two treatment groups. This process is similar to flipping a coin and determines which dose level of inavolisib you will receive.

    Both groups will receive inavolisib in combination with fulvestrant, but at different dose levels of inavolisib.

  2. Step 2

    Treatment with inavolisib and fulvestrant

    You will receive inavolisib as a film-coated tablet taken by mouth. The dose will be either 9 mg once daily or 6 mg once daily, depending on which group you were assigned to.

    You will also receive fulvestrant as an injection into the muscle. The specific dosage and frequency of fulvestrant injections will be determined by the study protocol.

    You will continue taking inavolisib daily and receiving fulvestrant injections according to the schedule provided by the study team.

  3. Step 3

    Regular monitoring visits

    Throughout the study, you will attend regular visits where the study team will monitor your health and how the treatment is affecting you.

    During these visits, your tumor response will be assessed to determine if the cancer is responding to treatment. This will be done at least 4 weeks apart on consecutive occasions to confirm any response.

    Blood tests and other clinical laboratory tests will be performed to check for side effects and monitor your overall health.

  4. Step 4

    Reporting symptoms and side effects

    You will be asked to report any symptoms or side effects you experience during the study. The study team will pay particular attention to high blood sugar, mouth sores, and diarrhea, as these are known side effects associated with this type of treatment.

    You will complete questionnaires about symptoms such as diarrhea, nausea, vomiting, decreased appetite, fatigue, mouth sores, and rash. These questionnaires help the study team understand how the treatment affects your daily activities.

    You will also be asked about specific symptoms related to high blood sugar, such as increased thirst and frequent urination.

    Additionally, you will complete questionnaires about how bothersome the treatment side effects are to you.

  5. Step 5

    Ongoing treatment and assessments

    You will continue receiving the study treatment and attending monitoring visits as long as the treatment is working for you and you are not experiencing unacceptable side effects.

    The study team will regularly check if your cancer is progressing or if the treatment is still effective.

    If you experience serious side effects, the study team may adjust your treatment or you may need to stop participating in the study.

  6. Step 6

    End of treatment

    Your participation in the treatment phase will end if your cancer progresses, if you experience unacceptable side effects, or if you decide to withdraw from the study.

    The study is expected to continue until approximately July 2028, but your individual participation length will depend on how you respond to treatment.

Who can join the trial?

8 criteria

  • You must have a tumor that is ER-positive (estrogen receptor-positive, meaning the cancer cells have receptors for the hormone estrogen) or PR-positive (progesterone receptor-positive, meaning the cancer cells have receptors for the hormone progesterone), confirmed by laboratory tests
  • You must have a HER2-negative tumor, which means the cancer cells do not have too much of a protein called human epidermal growth factor receptor 2, confirmed by laboratory tests
  • Your cancer must have gotten worse during or after treatment with a combination of a CDK4/6 inhibitor (a type of medicine that blocks proteins that help cancer cells grow) and endocrine therapy (hormone-based treatment) for cancer that has spread to other parts of the body, and you must have received no more than one prior treatment for cancer that has spread or come back
  • You must have cancer that can be measured using imaging tests according to specific medical criteria, and if you have cancer only in the bones, you must have at least one area of soft tissue that can be measured
  • You must be suitable for hormone-based treatment and not need chemotherapy at the time of joining the study
  • You must have at least one specific change in a gene called PIK3CA (a gene mutation that affects how cells grow) confirmed by testing
  • You must have a life expectancy of more than 6 months
  • You must be able and willing to follow all study procedures, including completing questionnaires about how you feel

Who cannot join the trial?

3 criteria

  • The specific exclusion criteria (reasons why patients cannot participate) have not been provided in the available study information
  • Generally, clinical trials for breast cancer (a disease affecting breast tissue) may exclude patients based on certain medical conditions or previous treatments, but these details are not listed in the current documentation
  • Patients interested in this study should discuss with their doctor whether they meet the requirements for participation
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Investigated drugs

  • Inavolisib

    is a medication being tested in this clinical trial. It is given in combination with another drug called fulvestrant to treat a specific type of breast cancer. This medication is being studied at two different dose levels to see which works better and is safer for patients.

  • Fulvestrant

    is a medication used to treat hormone receptor-positive breast cancer. In this trial, it is given together with inavolisib to see how well the combination works in treating patients whose cancer has spread or grown locally.

What is already known about the treatment

  • Inavolisib

    Inavolisib is an investigational medication taken orally once daily that is being studied in combination with fulvestrant for the treatment of advanced or metastatic breast cancer that has specific genetic mutations (PIK3CA gene changes) and is hormone receptor-positive and HER2-negative. This drug works by blocking a protein called PI3K alpha, which helps cancer cells grow and survive, and when this protein is inhibited, it can slow down or stop the growth of cancer cells. Inavolisib belongs to a class of medications known as PI3K inhibitors, which target specific molecular pathways involved in cancer cell development. The medication is currently being evaluated in clinical trials to determine the most effective dose level when used together with fulvestrant.

  • Fulvestrant

    Fulvestrant is an approved hormonal therapy medication administered as an injection into the muscle, typically given once monthly after initial loading doses, and is used to treat hormone receptor-positive breast cancer that has spread to other parts of the body. This medication works by attaching to estrogen receptors on cancer cells and causing these receptors to be broken down, which blocks the effects of estrogen that would otherwise help the cancer cells grow. Fulvestrant is classified as a selective estrogen receptor degrader and is widely used in clinical practice for patients whose cancer has progressed after other hormonal treatments. In this clinical trial, it is being combined with inavolisib to potentially improve treatment outcomes for patients with specific genetic mutations in their breast cancer.

Investigated diseases

Breast Cancer – Breast cancer is a disease where abnormal cells in the breast tissue grow uncontrollably and form a tumor. In this study, the focus is on a specific type that has spread beyond the breast to nearby tissues or other parts of the body. This form of breast cancer contains certain proteins called hormone receptors that respond to hormones like estrogen or progesterone, which can fuel cancer growth. The cancer cells do not have excessive amounts of a protein called HER2 on their surface. Additionally, these cancer cells carry a specific genetic change in the PIK3CA gene, which affects how cells grow and divide. As the disease progresses, it can spread through the lymphatic system or bloodstream to other organs in the body.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IITrial ID2025-522805-39-00Protocol codeWO46063Estimated enrolment80 patientsSponsorF. Hoffmann-La Roche AG

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