A Study of Elacestrant Versus Standard Endocrine Therapy in Women and Men With ER+,HER2-, Early Breast Cancer With High Risk of Recurrence

Key Inclusion Criteria:

• Histopathologically or cytologically confirmed ER-positive (≥ 10% byimmunohistochemistry [IHC]), HER2-negative [IHC = 0 or 1, or (IHC = 2 and in situhybridization [ISH]-negative)] on tumor biopsy or final surgical pathology specimenearly stage resected invasive breast cancer without evidence of recurrence ordistant metastases, per local laboratory, according to the American Society ofClinical Oncology (ASCO)/College of American Pathologists (CAP) guidelines

• Participants considered at high risk of recurrence at initial staging

• Participants who have received at least 24 months but not more than 60 months ofendocrine therapy (AIs or tamoxifen) with or without a CDK 4 and CKD 6 inhibitor (CDK4/6i)

• Participants who received prior CDK4/6i or a poly adenosine diphosphate-ribosepolymerase (PARP) inhibitor must have already completed or discontinued thesetreatments.

Key Exclusion Criteria:

• Participants with inflammatory breast cancer

• History of any prior (ipsilateral and/or contralateral) invasive breast cancer

• Participant with history of malignancy within 3 years of the date of randomization,except for adequately treated basal or squamous cell skin cancer, superficialbladder cancer or carcinoma in situ of the cervix

• Participants who have had more than a 6-month continuous interruption of prior SoCadjuvant endocrine therapy or who discontinued adjuvant endocrine therapy more than 6 months prior to randomization

Note: Other protocol defined Inclusion/Exclusion criteria may apply.