PVX-410 Vaccine Plus Pembrolizumab in HLA-A2+ Metastatic Triple Negative Breast Cancer

This research study is studying immunotherapy as a possible treatment for metastatic Triple Negative Breast Cancer (TNBC) in participants who are HLA-A2+. The drugs involved in this study are: * PVX-410 * Pembrolizumab * Hiltonol * Montanide

This research study is a Phase Ib clinical trial, which tests the safety of an investigational drug combination and also tries to better understand how the investigational intervention affects the body. "Investigational" means that the FDA (the U.S. Food and Drug Administration) has not approved the combination of PVX-410 and pembrolizumab as a treatment regimen for this specific disease. The FDA has not approved PVX-410 as a treatment for any disease. PVX-410 is a type of vaccine that may help the immune system stimulate immunity against the cancer cells. The FDA has not approved pembrolizumab for this specific disease but it has been approved in the United Sates for other types of cancer. Pembrolizumab is a drug that may treat cancer by working with the immune system. The immune system is the body's natural defense against disease. The immune system sends types of cells throughout the body to detect and fight infections and diseases, including cancer. For some types of cancer, the immune cells do not work as they should and are prevented from attacking the tumors. Pembrolizumab is thought to work by blocking a protein in the cells called Programmed Death-1 (PD-1), which then allows these cells and other parts of the immune system to attack tumors. In this research study, the investigators are studying the body's immune response to the PVX-410 study vaccine in combination with pembrolizumab. This study will help researchers understand if the vaccine and pembrolizumab can work together to help the body's immune system recognize and treat triple negative breast cancer. The investigators are also studying the safety of the PVX-410 together with the pembrolizumab