OPERA-01Palazestrant vs Standard Endocrine Therapy for ER+, HER2- Advanced or Metastatic Breast Cancer

This study focuses on patients with advanced or metastatic breast cancer that is positive for estrogen receptors (ER+) but negative for human epidermal growth factor receptor 2 (HER2-). The goal is to compare a new treatment called palazestrant (OP-1250) to the standard treatments currently in use, which include medications like fulvestrant and various aromatase inhibitors such as anastrozole, letrozole, or exemestane. This trial is important because it aims to find out if palazestrant can offer a more effective treatment option for those whose cancer has worsened despite previous therapies, including a combination of endocrine therapy and CDK 4/6 inhibitors. In this trial, adult participants will be randomly assigned to receive either the new drug palazestrant or one of the standard treatments. The study will first determine the best dose of palazestrant by testing two different amounts on about 120 participants. After finding the optimal dose, an additional 390 participants will be enrolled to further evaluate the effectiveness and safety of palazestrant compared to the standard treatments. The study will monitor the participants' health to see how well the cancer responds to the treatment and to check for any side effects, aiming to provide clearer insights into the most beneficial treatment approach for this type of breast cancer.