PARP Inhibitor With CDK4/6 Inhibitor and Endocrine Therapy in HR+/ HER2-Advanced Breast Cancer

This trial is testing a combination of three medications — a PARP inhibitor, a CDK4/6 inhibitor, and hormone therapy — in women with advanced hormone receptor-positive, HER2-negative breast cancer that belongs to a specific molecular subtype (SNF-3). Combining these drugs targets multiple pathways the cancer uses to grow. **You may be eligible if...** - You are a female, 18–75 years old - You have advanced breast cancer that is hormone receptor-positive (ER/PR positive) and HER2-negative - Your cancer has been confirmed to be the SNF-3 molecular subtype - You are postmenopausal or can have ovarian suppression **You may NOT be eligible if...** - Your cancer is HER2-positive or hormone receptor-negative - You have previously received CDK4/6 inhibitor therapy - You have another active cancer or serious organ problems - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.