Primary Objective: To evaluate the efficacy of investigational agent compared with standard endocrine therapy in in reducing Ki67 values based on digital pathology (QuPath) from baseline to on-treatment biopsy after an specific treatment duration (i.e. 14 days) in ER-positive, HER2-negative tumors (tumor size ≥1 cm) with Ki67 ≥ 10%, for different integrative subtype categories identified at integrative subtype screening.~Secondary Objective: To evaluate the efficacy of investigational agent compared with standard endocrine therapy on the proportion of subjects with Ki67 < 10% after a specific treatment duration (i.e. 14 days)
The purpose of this study is to learn if adding a new drug that is targeted at a specific genetic change found in some breast tumors pre-operatively will slow the growth of the tumor more than standard anti-hormone therapy used to treat this type of breast cancer. Different therapies are being tested based on the specific gene changes in the tumor. Not every tumor will have a gene change that is being studied.