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Study on Giredestrant or Tamoxifen for Premenopausal Women with Early ER-Positive, HER2-Negative Breast Cancer

Verified siteRegistered drugNo placebo
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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 a type of breast cancer known as ER-positive/HER2-negative early breast cancer. This type of cancer is characterized by the presence of estrogen receptors (ER) and the absence of human epidermal growth factor receptor 2 (HER2) in the cancer cells. The study involves two treatments: Giredestrant, also known by its code name GDC-9545, and Tamoxifen. Giredestrant is a new type of medication that works by degrading estrogen receptors, while Tamoxifen is a well-known treatment that blocks estrogen receptors.

The purpose of the study is to observe changes in the growth of cancer cells by measuring a protein called Ki67, which is associated with cell proliferation. Participants in the study will receive either Giredestrant or Tamoxifen. The study will involve taking a sample of the tumor before and after the treatment to assess the effect of the medication on the cancer cells. This will help researchers understand how these treatments affect the growth of cancer cells in patients with this specific type of breast cancer.

Participants will be monitored throughout the study to track any changes in their condition and to identify any side effects of the treatments. The study aims to provide valuable information on the effectiveness of Giredestrant compared to Tamoxifen in treating ER-positive/HER2-negative early breast cancer. This research could potentially lead to improved treatment options for patients with this type of breast cancer.

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

    Joining the study

    Upon joining the study, the first step involves signing an Informed Consent Form (ICF). This form confirms understanding of the study and agreement to participate.

    Participants must be able to swallow and absorb oral medication and be at least 18 years old.

  2. Step 2

    Initial assessments

    Initial assessments include confirming premenopausal status and conducting a diagnostic biopsy if not done within the last 8 weeks.

    Blood samples are taken to ensure adequate bone marrow, liver, and kidney function.

  3. Step 3

    Treatment assignment

    Participants are assigned to one of two treatment groups: giredestrant or tamoxifen.

    Both medications are taken orally in the form of hard capsules.

  4. Step 4

    Medication administration

    Participants take the assigned medication daily. The specific dosage and duration are determined by the study protocol.

    Regular monitoring is conducted to assess the body's response to the medication.

  5. Step 5

    Follow-up assessments

    Follow-up assessments include additional blood samples and tumor biopsies to measure changes in tumor cell activity.

    These assessments help evaluate the effectiveness of the treatment.

  6. Step 6

    Completion of study

    Upon completion of the treatment period, a final set of assessments is conducted.

    Participants may be asked to provide feedback on their experience and any side effects encountered.

Who can join the trial?

14 criteria

  • Sign the Informed Consent Form before starting any study procedures.
  • Be able and willing to swallow and absorb oral medication.
  • Be at least 18 years old at the time of signing the consent form.
  • Have an ECOG performance status of 0-1, which means you are fully active or have some symptoms but do not need bed rest during the day.
  • Be a woman with a well-determined premenopausal status, meaning you are still having regular menstrual cycles.
  • Have a confirmed diagnosis of invasive breast cancer with the following characteristics:
    • ER[+] tumor, meaning the cancer cells grow in response to the hormone estrogen.
    • HER2[-] tumor, meaning the cancer does not have high levels of the protein HER2.
    • Ki67 score ≥10%, which is a measure of how quickly cancer cells are growing.
    • Tumor size must be at least 1.0 cm in the longest diameter as measured by ultrasound.
    • Be willing to provide a primary tumor tissue and blood sample at the start and after treatment.
    • Have adequate bone marrow, liver, and kidney function, which will be checked by specific blood tests.
    • Have a negative pregnancy test before starting the study treatment if you are of childbearing potential.
    • Agree to use effective contraception methods during the study and for a specified period after the study, or remain abstinent from sexual activity.
    • Be accessible for treatment and follow-up visits.

Who cannot join the trial?

4 criteria

  • Patients with a type of breast cancer that is not ER[+]/HER2[-] and does not have a Ki67 level of 10% or higher cannot participate. ER[+]/HER2[-] refers to specific characteristics of breast cancer cells, and Ki67 is a marker that shows how fast cancer cells are growing.
  • Only female patients are eligible to participate in this study.
  • Male patients cannot participate in this study.
  • Patients who are considered part of a vulnerable population are not eligible. A vulnerable population includes groups who may have limited ability to protect their own interests, such as children or those with certain disabilities.
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Investigated drugs

  • Giredestrant (GDC-9545)

    is a medication being studied for its potential to treat early breast cancer in premenopausal women. It works by targeting and blocking the activity of estrogen receptors in cancer cells. Estrogen can promote the growth of certain types of breast cancer, so by blocking these receptors, giredestrant may help slow down or stop the growth of the cancer.

  • Tamoxifen

    is a well-known medication used to treat breast cancer. It works by blocking estrogen receptors on breast cancer cells, which can help prevent the cancer from growing. Tamoxifen is often used in premenopausal women with hormone receptor-positive breast cancer, and it has been a standard treatment for many years. In this trial, it is being compared to giredestrant to see which is more effective in reducing cancer cell growth.

What is already known about the treatment

  • Giredestrant

    Giredestrant is administered orally and is currently being studied in clinical trials for its potential use in treating early breast cancer, specifically in premenopausal women with ER-positive, HER2-negative tumors with high Ki67 levels. This medication works by blocking estrogen receptors on cancer cells, which can slow down or stop the growth of these cells. It is classified as a selective estrogen receptor degrader (SERD), a type of hormone therapy. The main goal of the ongoing study is to observe changes in tumor cell growth before and after treatment with Giredestrant.

  • Tamoxifen

    Tamoxifen is an oral medication that has been widely used and studied in the treatment of breast cancer, particularly for hormone receptor-positive types. It functions by binding to estrogen receptors on cancer cells, preventing estrogen from stimulating the growth of these cells. Tamoxifen is classified as a selective estrogen receptor modulator (SERM). In the current clinical trial, it is being compared to Giredestrant to assess its effectiveness in reducing tumor cell proliferation in premenopausal women with early breast cancer.

Investigated diseases

Early Breast Cancer (ER[+]/HER2[-] & Ki67≥10%) – Early breast cancer is a form of breast cancer where the tumor is confined to the breast or nearby lymph nodes. In this subtype, the cancer cells have estrogen receptors (ER-positive) but do not have excess human epidermal growth factor receptor 2 (HER2-negative). The Ki67 index, which is a marker of cell proliferation, is 10% or higher, indicating a higher rate of cell growth. The disease progresses as cancer cells multiply and potentially spread to nearby tissues. Over time, the tumor may grow larger and affect more areas within the breast or nearby lymph nodes. Monitoring the Ki67 index helps in understanding the aggressiveness of the cancer.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IITrial ID2023-503565-36-00Protocol codeMedOPP459 "EMPRESS"Estimated enrolment92 patientsSponsorMedica Scientia Innovation Research S.L.

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