Not yet recruitingPHASE2INTERVENTIONAL

A Study of Imlunestrant (LY3484356) in Premenopausal Women With Estrogen Receptor-Positive (ER+) Human Epidermal Growth Factor Receptor 2 Negative (HER2-) Early Breast Cancer

This study is investigating a new medication called imlunestrant for premenopausal women with early breast cancer that's sensitive to hormones (Estrogen Receptor-positive, HER2-negative). The study has two main groups, called cohorts. Cohort 1 aims to understand how imlunestrant affects cancer cells. Some women will take imlunestrant with treatment to stop their ovaries working, and some without. This will be compared to tamoxifen, another common breast cancer drug. The treatment for this group lasts up to 29 days. Cohort 2 focuses on how imlunestrant affects the ovaries when taken without ovarian suppression. Again, this will be compared to tamoxifen. This group's treatment will last up to 6 months. Both groups involve women who can still have periods. The overall goal is to see if imlunestrant could be a future treatment option for this type of breast cancer.

At a glance

Status

Not yet recruiting

Phase

PHASE2

Sponsor

Eli Lilly and Company

Enrolment target

600

Start

01 May 2026

Estimated completion

01 Dec 2029

Breast Neoplasms

What is this study about?

This research study is about a new medicine called imlunestrant (also known by its code LY3484356), which is being tested for a specific type of early breast cancer. This particular type of breast cancer is called "estrogen receptor-positive" and "HER2-negative." This means the cancer cells grow because of the hormone oestrogen, and they don't have too much of a protein called HER2. This is a common type of breast cancer, and the study is focused on women who are still having periods (premenopausal).

The study is divided into two main parts, called cohorts, each looking at slightly different things. Cohort 1 will help doctors learn how imlunestrant directly affects cancer cells. They will compare it to an existing treatment called tamoxifen. Some women will also receive treatment to suppress their ovaries, while others won't, to see how that affects the new medicine's impact. Cohort 2 will specifically look at how imlunestrant affects the ovaries themselves when ovarian function isn't suppressed, again comparing it to tamoxifen.

The overall aim is to understand if imlunestrant could be a new and effective treatment option for premenopausal women with this type of early breast cancer. By comparing it to tamoxifen, which is a standard treatment, researchers can see if it works similarly or even better. This kind of research is important for finding new ways to help people with cancer.

Key takeaways

Study is for premenopausal women with specific type of early breast cancer.
Investigates a new drug, imlunestrant, compared to tamoxifen.
Aims to understand drug's effect on cancer cells and ovaries.
Treatment duration varies from less than a month to up to six months.
Participation involves taking study medication and regular medical check-ups.
You can withdraw from the study at any time.

Who may be eligible?

This study is specifically looking for premenopausal women (meaning you still have periods) who have been diagnosed with a certain type of early breast cancer. This must be breast cancer that is sensitive to oestrogen (ER-positive) and doesn't have too much of the HER2 protein (HER2-negative). You should generally feel well and be able to swallow tablets or capsules.

For Cohort 1, your breast cancer should be in stages I to III and show a certain level of cell growth (Ki-67 at least 10%). You'd also need to be willing to provide tissue samples from your tumour before and during treatment. For Cohort 2, you should have already had surgery for your ER+, HER2- early breast cancer and received at least 4.5 years of hormone therapy, or at least 2 years with no further ovarian suppression planned.

There are also some reasons why you might not be able to join. For example, if you have inflammatory breast cancer, other serious medical conditions, or have recently had major surgery. You also can't have had certain other cancers unless they've been gone for a long time without treatment. If you could become pregnant, you would need to use effective non-hormonal contraception during the study.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

Am I a premenopausal woman (do I still have periods)?
Do I have ER-positive, HER2-negative early breast cancer?
Do I generally feel well and am I able to swallow tablets?
Have I had surgery for my breast cancer (for Cohort 2)?
Am I using effective non-hormonal contraception if I could become pregnant?

Answer every question to see your result.

What does participation involve?

If you decide to take part in this study, what happens next depends on which group (cohort) you would be in. For Cohort 1, the treatment period will be quite short, lasting up to 29 days. For Cohort 2, the treatment might last longer, up to 6 months. During this time, you would take either the new medicine, imlunestrant, or an existing one, tamoxifen, depending on which group you're assigned to. Some participants might also receive a treatment to suppress their ovarian function.

You would have regular appointments and tests so the doctors can monitor how the treatment is affecting you and your cancer. This could include providing tumour samples (for Cohort 1), blood tests, and scans. The team will explain exactly what's involved in your specific case, including how often you'd need to visit the clinic and any follow-up appointments after the main treatment period ends. All the details will be discussed with you before you make any decisions.

Potential risks and benefits

Taking part in any clinical trial has potential benefits and risks. You might benefit from receiving a new and potentially effective treatment for your breast cancer. You'll also be closely monitored by a medical team, and your participation helps advance medical knowledge, potentially helping others in the future. However, there could be side effects from the study medicines, which will be fully explained to you. The new medicine might not work as hoped, or it could even be less effective than standard treatments. You have the right to withdraw from the study at any time, for any reason, without it affecting your usual medical care.

Locations (60)

University of Alabama at Birmingham
Verified postcode
Birmingham, United States
Ironwood Cancer & Research Centers
Verified postcode
Chandler, United States
USC/Norris Comprehensive Cancer Center
Verified postcode
Los Angeles, United States
UCLA Hematology/Oncology - Parkside
Verified postcode
Santa Monica, United States
Banner MD Anderson Cancer Center at North Colorado Medical Center
Verified postcode
Greeley, United States
Banner MD Anderson Cancer Center at McKee Medical Center
Verified postcode
Loveland, United States
AdventHealth Altamonte Springs
Verified postcode
Altamonte Springs, United States
Winship Cancer Institute
Verified postcode
Atlanta, United States
Indiana University Melvin and Bren Simon Cancer Center
Verified postcode
Indianapolis, United States
Massachusetts General Hospital
Verified postcode
Boston, United States
Dana-Farber Cancer Institute
Verified postcode
Boston, United States
Washington University School of Medicine
Verified postcode
St Louis, United States

Common questions

What type of breast cancer is this study for?

This study is for premenopausal women with early-stage breast cancer that is Estrogen Receptor-positive (ER+) and HER2-negative (HER2-). This means your cancer grows because of oestrogen.

What is imlunestrant?

Imlunestrant is a new medicine being tested. Researchers want to see how it affects breast cancer cells and the ovaries, comparing it to an existing drug called tamoxifen.

How long will I be on the treatment?

For one group (Cohort 1), treatment lasts up to 29 days. For the other group (Cohort 2), treatment can last up to 6 months.

Will I have to take other medications?

Depending on the group, you might also take a treatment to suppress your ovarian function, or you might be taking tamoxifen instead of imlunestrant.

Can I still take part if I've had breast cancer before?

Usually no, if it was an invasive or inflammatory type. However, some very early or non-melanoma skin cancers are usually allowed if they have been treated and are gone for a long time.

How to find out more

Trial questions or participation questions: 1-877-CTLILLY (1-877-285-4559) or

lillytrials@lilly.com 1-317-615-4559 Official trial record

Always speak to your GP or specialist before deciding to take part in a study.