A Study of Imlunestrant, Investigator's Choice of Endocrine Therapy, and Imlunestrant Plus Abemaciclib in Participants With ER+, HER2- Advanced Breast Cancer (EMBER-3)

The main purpose of this study is to measure how well imlunestrant works compared to standard hormone therapy, and how well imlunestrant with abemaciclib work compared to imlunestrant in participants with breast cancer that is estrogen receptor positive (ER+) and human epidermal receptor 2 negative (HER2-). Participants must have breast cancer that is advanced or has spread to another part of the body. Study participation could last up to 5 years.

In order to participate you must meet the following criteria:

• Have a diagnosis of ER+, HER2- locally advanced or metastatic breast cancer.
• Have disease that has demonstrated progression on or after an aromatase inhibitor alone or in combination with a cyclin-dependent kinase (CDK)4/6 inhibitor.
• Have been deemed appropriate for treatment with endocrine therapy.

You will be excluded from the study if any of the following criteria apply to you:

• Have received prior treatment with chemotherapy (except for neoadjuvant/ adjuvant chemotherapy), fulvestrant, or any investigational-ER-directed therapy (including SERDs and non-SERDs), any PI3K-, mTOR- or AKT- inhibitor.
• wHave visceral crisis, lymphangitic spread within the lung, or any evidence of leptomeningeal disease.
• 3). Have symptomatic or untreated brain metastasis.

This is a partial list of eligibility requirements. To inquire about your eligibility, please call the contact number provided. If you wish to inquire via email, please include the title of the study in your message.