NIMBUS: Nivolumab Plus Ipilimumab in Metastatic Hypermutated HER2-negative Breast Cancer

This research study is a Phase II clinical trial. Phase II clinical trials test the safety and effectiveness of an investigational drug to learn whether the drug works in treating a specific disease. "Investigational" means that the drug is being studied. Nivolumab is called an anti- PD-1 or a checkpoint inhibitor and is an antibody (a type of human protein) designed to allow the body's own immune system to destroy tumors. Ipilimumab is called an anti-CTLA-4 and is a type of antibody that works to prevent your body's immune system from stopping to fight this specific cancer. The U.S. Food and Drug Administration (FDA) has not approved nivolumab for this specific disease but it has been approved for other uses including but not limited to non-small cell lung cancer, melanoma and renal cell carcinoma. The U.S. Food and Drug Administration (FDA) has not approved ipilimumab for this specific disease but it has been approved for other uses such as melanoma and renal cell carcinoma. The combination of nivolumab with ipilimumab may or may not increase anti-cancer activity by further boosting the immune system. At this time, the FDA has not approved nivolumab in combination with ipilimumab for this specific disease although these drugs have been approved for other uses such as melanoma and renal cell carcinoma. The purpose of this research study is to determine how nivolumab together with ipilimumab, works in treating breast cancer that has spread to other parts of the body. The investigators are also investigating whether there are certain DNA or protein markers in the blood or tumor tissue that may indicate whether the combination will work in future patients