Active not recruitingPHASE3INTERVENTIONAL

A Study of Imlunestrant, Investigator's Choice of Endocrine Therapy, and Imlunestrant Plus Abemaciclib in Participants With ER+, HER2- Advanced Breast Cancer

This research study is for women with advanced breast cancer that is estrogen receptor-positive (ER+) and HER2-negative (HER2-). This means the cancer uses estrogen to grow and doesn't have too much of the HER2 protein. The main goal is to see how well a new drug, imlunestrant, works compared to standard hormone treatments. We also want to find out if combining imlunestrant with another drug called abemaciclib is even more effective. Participants will have cancer that has either spread to another part of the body or is locally advanced. The study could last up to five years, helping us find better ways to treat this type of breast cancer.

At a glance

Status

Active not recruiting

Phase

PHASE3

Sponsor

Eli Lilly and Company

Enrolment target

874

Start

04 Oct 2021

Estimated completion

01 Aug 2027

Breast Neoplasms Neoplasm Metastasis

Results

Results from this study

Posted July 2025

Results have been published for this study.

Primary outcome

Investigator-assessed Progression Free Survival (PFS) (Between Arm A and Arm B)

PFS was defined as the time from randomization to the date of first documented progression of disease or death from any cause in the absence of disease progression using Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 criteria, as assessed by investigator. Progressive disease (PD) was defined as at least a 20% increase in the sum of the diameters of target lesions, with reference being the smallest sum on study and an absolute increase of at least 5 mm, or unequivocal progression of non-target lesions, or 1 or more new lesions. Participants known to be alive and without disease progression were censored at the date of their last adequate tumor assessment per RECIST 1.1 criteria, or date of randomization (whichever is later).

Full results on the registry

What is this study about?

This study is looking for better ways to treat a common type of breast cancer called ER-positive, HER2-negative (ER+, HER2-). This means the cancer cells respond to the hormone estrogen to grow, but don't have high levels of a protein called HER2. When this type of breast cancer is advanced or has spread (metastasized) to other parts of the body, finding effective treatments is very important.

The researchers want to compare a new drug called imlunestrant with the usual hormone treatments currently given. They're also investigating if adding another existing drug, abemaciclib, to imlunestrant works even better. By comparing these treatments, the study aims to understand which approach offers the most benefit to patients with this condition, potentially leading to new standard treatments in the future.

Taking part in this study could mean you receive imlunestrant, standard hormone therapy like exemestane or fulvestrant, or a combination of imlunestrant and abemaciclib. The study is carefully designed to ensure we gather reliable information about how well these treatments work and if they have any side effects. This research is a crucial step in improving the lives of people affected by advanced ER+, HER2- breast cancer.

Key takeaways

This study is for advanced ER+, HER2- breast cancer that has grown or spread.
It compares a new drug, imlunestrant, with existing standard hormone therapies.
It also checks if adding abemaciclib to imlunestrant works better.
Participation could last up to 5 years, with regular medical checks.
You must have had previous hormone treatment for your breast cancer.
The aim is to find more effective treatments for this specific type of breast cancer.

Who may be eligible?

To join this study, you must be an adult (18 years or older) with breast cancer that is ER-positive and HER2-negative. Your cancer needs to be advanced, meaning it has either grown locally into surrounding tissues or has spread to other parts of your body. You should have already received a previous treatment for your breast cancer that included an aromatase inhibitor, and likely a CDK4/6 inhibitor if that treatment was available and covered where you live.

You should be well enough to receive hormone-based treatment, and if you are a woman, you must be past menopause – either naturally, through surgery, or with medication that stops your ovaries from working. Doctors will also check that your cancer can be measured to see if the treatment is working, and you should be generally healthy enough, with good organ function, and able to swallow pills.

There are also reasons why you might not be able to join. For example, if you've already had certain types of chemotherapy (beyond initial treatment) or other specific targeted drugs, or if your cancer is in a critical state like badly affecting your lungs or brain. The doctors will review your full medical history to make sure the study is a safe and suitable option for you.

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.

Are you 18 years or older?
Do you have advanced ER-positive, HER2-negative breast cancer?
Have you already received an aromatase inhibitor (and likely a CDK4/6 inhibitor) for your cancer?
Are you able to swallow tablets or capsules?
Are you usually well enough to receive treatment, with good organ function?
If you are a woman, are you past menopause (naturally, surgically, or due to medication)?

Answer every question to see your result.

What does participation involve?

If you decide to take part in this study, you could be on the study for up to five years. Throughout this time, you will have regular visits to the clinic for check-ups and tests. These tests may include blood samples, urine tests, and scans (like X-rays or CT scans) to see how your cancer is responding to the treatment.

You will be given either the new study drug (imlunestrant), a standard hormone treatment, or a combination of imlunestrant and abemaciclib, usually in pill form. You'll need to take your medication as instructed and report any changes in your health or any side effects you notice to the study team. You will have regular appointments with the study doctors and nurses to monitor your progress, manage any side effects, and ensure your safety. While the study officially lasts up to five years, your treatment will continue as long as it is helping you and you are tolerating it well.

Potential risks and benefits

Taking part in a clinical trial offers potential benefits, including access to new treatments like imlunestrant before they are widely available. You'll also receive close medical attention and monitoring throughout the study. However, there are also potential risks. The study drugs may have side effects, some of which could be serious or unexpected, and there’s no guarantee that the treatment will be effective for you. You will be fully informed about all known risks before you decide to join. It’s important to remember that participating in this study is completely voluntary, and you have the right to withdraw from the study at any time, for any reason, without it affecting your usual medical care.

Locations (243)

Ironwood Cancer & Research Centers
Verified postcode
Chandler, United States
Banner MD Anderson Cancer Center
Verified postcode
Gilbert, United States
Marin Cancer Care
Verified postcode
Greenbrae, United States
University of California Davis (UC Davis) Comprehensive Cancer Center
Verified postcode
Sacramento, United States
Sharp Memorial Hospital
Verified postcode
San Diego, United States
Banner MD Anderson Cancer Center at McKee Medical Center
Verified postcode
Loveland, United States
Clermont Oncology Center
Verified postcode
Clermont, United States
University of Florida College of Medicine
Verified postcode
Gainesville, United States
Mid Florida Hematology and Oncology Center
Verified postcode
Orange City, United States
Florida Cancer Specialists
Verified postcode
Sarasota, United States
Florida Cancer Specialists
Verified postcode
St. Petersburg, United States
Kaiser Permanente Moanalua Medical Center
Verified postcode
Honolulu, United States

Common questions

What type of breast cancer is this study for?

This study is for advanced breast cancer that is ER-positive (meaning it grows with estrogen) and HER2-negative (meaning it doesn't have too much of the HER2 protein).

What are the main drugs being tested?

The main drug being tested is imlunestrant, either by itself or combined with abemaciclib. These are compared to standard hormone treatments like exemestane or fulvestrant.

How long would I be in the study?

Participation in the study could last for up to five years, with regular check-ups and treatments during that time.

Do I have to have had previous treatment for my cancer?

Yes, you should have already received a hormone treatment called an aromatase inhibitor, and very likely a CDK4/6 inhibitor, if it was available to you.

Can men join this study?

The study is open to all genders, but the eligibility criteria mention "postmenopausal status" for women, suggesting it is primarily for women given the nature of ER+ breast cancer treatments often related to female hormones.