Palbociclib With Everolimus + Exemestane In BC

This is a Phase I/II clinical trial. The Phase I portion of this clinical trial tests the safety of an investigational intervention and also tries to define the appropriate dose of the investigational intervention to use for further studies. The Phase II portion of the study tests the safety and effectiveness of an investigational intervention to learn whether the intervention works in treating a specific disease. "Investigational" means that the intervention is being studied. The FDA (the U.S. Food and Drug Administration) has not approved the combination of Palbociclib, Everolimus, and Exemestane as a treatment for any disease. This is the first time that the combination of Palbociclib, Everolimus, and Exemestane will be given to humans. Palbociclib is a drug that may stop cancer cells from growing. Palbociclib blocks activity of two closely related enzymes (proteins that help chemical reactions occur in the body), called Cyclin D Kinases 4 and 6 (CDK 4/6). These proteins are part of a pathway, or a sequence of steps, which is known to regulate cell growth. Laboratory testing has suggested Palbociclib may stop the growth of HR+ breast cancer. Everolimus is a type of drug called an mTORinhibitor that treats breast cancer by preventing the cells from multiplying by inhibiting the pathway, or a sequence of steps, known to regulate cell reproduction. Everolimus also may stop the growth of cancer cells by decreasing blood supply to the cancer cells. Exemestane is an anti-hormone therapy that prevents breast cancer cell growth by blocking estrogen receptor stimulation. Premenopausal women will also receive an injection drug called an LHRH (luteinizing hormone-releasing hormone) agonist to shut down ovary function. It is standard of care for people with breast cancer, specifically with HR+ breast cancer, to take anti-hormone therapy. The combination of everolimus and exemestane is FDA approved to treat this type of breast cancer. The purpose of the Phase I portion of this research study is to determine a safe and tolerable dose of the combination of Palbociclib, Everolimus, and Exemestane for participants with ER-positive, HER2-negative advanced breast cancer. The purpose of the Phase II portion of this research study is to determine whether the combination of Palbociclib, Everolimus, and Exemestane is an effective treatment for participants with ER-positive, HER2-negative advanced breast cancer.