GDC-0084 in Combination With Trastuzumab for Patients With HER2-Positive Breast Cancer Brain Metastases

This research study is a Phase II clinical trial. Phase II clinical trials test 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 GDC-0084 as a treatment for any disease. Trastuzumab is a targeted therapy approved by the FDA to be used alone or in combination with a chemotherapy drug to treat HER2-positive metastatic breast cancer. GDC-0084 has been shown to stop the activity of a protein called PI3-kinase. This action blocks a pathway in the body that cancer cells commonly use to grow and divide. Trastuzumab is called a "targeted therapy" because it works by attaching itself to specific receptors on the surface of breast cancer cells, known as HER2 receptors. When targeted therapies attach to HER2 receptors, the signals that tell the cells to grow are blocked and the cancer cell may be marked for destruction by the immune system. This process allows trastuzumab to help slow or stop the growth of the breast cancer. In this research study, the investigators are looking to see how your cancer responds to the combination of GDC-0084 and Trastuzumab.