ELACESTRANT in Women and Men With CDK4/6 Inhibitor-Naive Estrogen Receptor Positive, HER-2 Negative Metastatic Breast Cancer Study

This is a Phase 2 trial evaluating the efficacy of elacestrant in patients with ER+/HER2- advanced/metastatic breast cancer who received one or two prior hormonal therapies and no prior CDK4/6i in the metastatic setting. The study duration for each patient is estimated to be: * Screening Phase: Up to 28 days prior to Cycle 1, Day 1 (C1D1); * Treatment Phase: From C1D1 until the date of radiologically documented progression, or treatment discontinuation due to other reasons. * Survival Follow-Up Phase: All patients will be followed for survival approximately every 3 months up to 24 months after enrollment of the last patient. Patients will be followed for adverse events (AEs) for 28 days after the last treatment administration.