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Study of Tersolisib and a drug combination for adults with advanced hormone receptor-positive, HER2-negative breast cancer with a PIK3CA mutation

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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 individuals with advanced Breast Cancer, specifically a type known as HR-positive, HER2-negative cancer. This means the cancer cells grow in response to certain hormones and do not have high levels of a specific protein called human epidermal growth factor receptor 2. The study also involves patients whose cancer has a PIK3CA mutation, which is a genetic change that can help the cancer grow. Additionally, the study considers cases where the cancer has spread to other parts of the body, a process called Neoplasm Metastasis.

The purpose of the study is to evaluate how well a new drug called tersolisib works when added to other treatments. The medications being studied include CDK4/6 inhibitors, such as palbociclib, ribociclib, or abemaciclib, and endocrine therapy, which includes drugs like anastrozole, exemestane, letrozole, or fulvestrant. Participants will receive combinations of these medicines to see if the addition of tersolisib improves the treatment of the disease.

The study is conducted in different stages. In the first part, the focus is on finding the best dose of the new medication. In the second part, the new drug is compared to a placebo. Participants will take these medications through oral tablets or injections as assigned. The study continues for as long as the treatment is effective and the side effects are manageable.

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

    Participation in the study

    After joining the study, tersolisib is taken by mouth.

    Tersolisib is combined with either a CDK4/6 inhibitor or endocrine therapy to treat advanced breast cancer that has a specific genetic change called a PIK3CA mutation.

  2. Step 2

    Medication administration

    The specific medications used in the treatment include anastrozole (1 mg), palbociclib (125 mg), ribociclib (600 mg), exemestane (25 mg), fulvestrant (500 mg administered by injection into a muscle), abemaciclib (500 mg), or letrozole (2.5 mg).

    All these medications are taken by mouth, except for fulvestrant, which is given via intramuscular use, meaning an injection into the muscle.

  3. Step 3

    Treatment monitoring

    The effectiveness of the treatment is monitored from the start of the study until the cancer grows or death occurs, which may last up to 5 years.

    The duration of the study depends on how the cancer responds to the drugs and whether any side effects become too difficult to manage.

Who can join the trial?

9 criteria

  • People who were assigned female at birth can be at any stage of menopause, which is the period when a woman stops having periods. However, those who have not yet gone through menopause must agree to take medication called a GnRH agonist to stop their body from producing certain hormones.
  • People who were assigned male at birth with estrogen receptor positive (ER+) breast cancer must agree to use a GnRH agonist to lower hormone levels.
  • Participants must have a breast cancer diagnosis that has been confirmed by a doctor looking at cells under a microscope, a process known as histological or cytological confirmation.
  • Participants must have an activating PIK3CA mutation, which is a specific change or error in the DNA of the cancer cells found in a tumor or blood sample.
  • The cancer must be measurable, meaning it can be seen and measured on scans, or it can be evaluable bone disease, which means bone changes caused by cancer that a doctor can track.
  • For Part 1 of the study, patients must have received between 0 and 2 previous systemic treatments (medicines that travel through the whole body) for advanced breast cancer that cannot be cured by surgery. Of these treatments, no more than one can be chemotherapy (a type of strong medicine used to kill cancer cells).
  • For Part 2 of the study, patients must not have received any previous systemic treatments for advanced breast cancer that cannot be cured by surgery.
  • In Part 2, patients may be categorized as endocrine sensitive, meaning the cancer has responded well to hormone therapy, or endocrine resistant, meaning the cancer has continued to grow despite hormone therapy.
  • In Part 2, patients must have had their cancer grow again (relapsed) either more than 12 months after finishing adjuvant or neoadjuvant therapy (treatments given before or after the main treatment like surgery) or 12 months or less after finishing those treatments.

Who cannot join the trial?

5 criteria

  • People with Type 1 diabetes or Type 2 diabetes who have a high hemoglobin A1c (an average measure of blood sugar over the past few months) of 8% or higher, a fasting blood glucose (blood sugar level after not eating) of 140 mg/dL or higher, or who need to use insulin.
  • People diagnosed with inflammatory breast cancer (a rare and aggressive form of breast cancer) or metaplastic breast cancer (a type of breast cancer that has different characteristics than common breast cancer).
  • People who have a history of leptomeningeal disease or carcinomatous meningitis (conditions where cancer cells spread to the fluid and membranes surrounding the brain and spinal cord).
  • People with known, active, or untreated central nervous system metastases (cancer that has spread to the brain or spinal cord).
  • A person may still join if they have asymptomatic brain or spinal metastases (cancer in the brain or spine that is not causing symptoms) that has been treated with surgery or radiotherapy (the use of high-energy rays to kill cancer cells), provided the cancer has not grown or caused bleeding for at least 28 days and the person has not needed anticonvulsants (medicine to prevent seizures) or systemic corticosteroids (strong anti-inflammatory medicines) for at least 28 days.
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Investigated drugs

  • Anastrozole

    is an oral medication used to treat certain types of breast cancer by lowering the amount of estrogen in the body.

  • Palbociclib

    is an oral medication that helps stop the growth of cancer cells by blocking specific proteins that allow cells to divide.

  • Tersolisib

    is an oral medication being studied for its ability to target specific genetic changes in cancer cells to help stop cancer growth.

  • Ribociclib

    is an oral medication designed to slow down the progression of cancer by interfering with the cell cycle of cancer cells.

  • Exemestane

    is an oral medication used to treat breast cancer by preventing the production of estrogen.

  • Fulvestrant

    is a medication given by injection that works to block estrogen receptors in cancer cells, preventing them from growing.

What is already known about the treatment

  • Anastrozole

    This medication is taken by mouth as an oral pill to treat certain types of breast cancer. It belongs to a class of drugs called aromatase inhibitors, which are commonly used in medical practice for hormone-sensitive cancers. The drug works by blocking the enzyme in the body that produces estrogen, thereby reducing the amount of estrogen available to fuel cancer growth.

  • Palbociclib

    This drug is administered orally and is a well-known treatment used in cancer therapy. It is classified as a CDK4/6 inhibitor, which helps manage advanced breast cancer. At the molecular level, it works by stopping specific proteins from helping cancer cells divide, effectively slowing down the spread of the disease.

  • TERSOLISIB

    This substance is administered orally in tablet form and is currently being studied in clinical research. It belongs to a class of drugs known as PI3K inhibitors, which are investigated for their ability to target specific genetic mutations. It works by blocking a specific signaling protein in the cell that tells cancer cells to grow and survive.

  • Ribociclib

    This medication is taken by mouth and is an established treatment in oncology. It is categorized as a CDK4/6 inhibitor, primarily used for advanced breast cancer. It functions by interfering with the cell cycle, specifically preventing the proteins that allow cancer cells to multiply uncontrollably.

  • Exemestane

    This is an oral medication used in the treatment of hormone-related breast cancers. It belongs to a group of drugs called aromatase inhibitors. The medication works by permanently binding to and disabling the enzyme responsible for making estrogen, which helps limit the growth of cancer cells.

  • Fulvestrant

    This medication is administered through an injection into the muscle. It is a recognized treatment classified as a selective estrogen receptor degrader. It works by attaching to estrogen receptors on cancer cells and destroying them, which prevents the hormone from stimulating tumor growth.

Investigated diseases

  • Neoplasm Metastasis

    This condition occurs when cancer cells break away from the original tumor and travel through the blood or lymphatic system to other parts of the body. Once these cells settle in a new location, they begin to grow into new tumors. This process allows the disease to spread beyond its initial site of origin. The progression involves the formation of secondary growths in distant organs or tissues.

  • Breast Neoplasms

    This refers to an abnormal growth of cells within the breast tissue. These growths can be classified based on how they interact with surrounding tissues and their specific biological characteristics. In certain types, the cells may be driven by specific hormones or proteins that encourage further development. The condition can progress from localized growths to more widespread involvement of the breast and surrounding areas.

Trial detailsLast updated 11 Nov 2026
Age18+ yearsPhasePhase IIITrial ID2025-522791-92-00Protocol codeJ6M-MC-JSGDEstimated enrolment913 patientsSponsorEli Lilly & Co.

sourced from the EU Clinical Trials Register and site verification

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