Pembrolizumab in Combination With Olaparib in Advanced BRCA-mutated or HDR-defect Breast Cancer

There are two BRCA genes, BRCA1 and BRCA2, and they play a role in protecting cells from cancer. HDR-defect is another type of gene mutation that can contribute to development and progression of cancer. If one of these genes is mutated, cells may rapidly change and divide, which can lead to cancer. Pembrolizumab is a drug that works with the immune system to target the tumor (immunotherapy). The investigators want to know if combining pembrolizumab and Olaparib therapy will be able to reduce the size and amount of cancer cells with fewer side effects than standard treatment by targeting the tumor. This research study is designed to test the investigational use of pembrolizumab and Olaparib in breast cancer.