A Single Arm Phase II Study Evaluating the Efficacy and Safety of MEDI4736 in Combination with Tremelimumab in Patients with Metastatic HER2 Negative Breast Cancer

Hypothesis: 1. PDL1 and CTLA-4 inhibition will result in clinical benefit (stable disease, partial or complete response) in patients with metastatic HER2-negative breast cancer. 2. PDL1 and CTLA-4 inhibition will result in prolonged progression-free survival (PFS) and overall survival (OS). 3. PDL1 and CTLA-4 inhibition will be safe with a favorable side effect profile. 4. Tissue and serum based biomarkers will act as predictors of response to PDL1 and CTLA-4 blockade and result in pharmacodynamic modulation. Objectives: 1. To evaluate clinical benefit rate in patients with metastatic HER2-negative breast cancer treated with PDL1 and CTLA-4 inhibition. 2. To evaluate the PFS and OS. 3. To evaluate safety and toxicity. 4. To evaluate if tissue-based biomarkers (IHC expression of PDL1; tumor infiltrating lymphocytes (TILs); T cell subpopulations; changes in tissue and peripheral T-cell receptor genotype; human leukocyte antigen (HLA) genotype; and immune-related candidate gene signatures) predict response to treatment and demonstrate pharmacodynamic effects.