MEDI4736 and Tremelimumab in Treating Patients With Metastatic HER2 Negative Breast Cancer

The main purpose of this study is to determine the anti-tumor activity of MEDI4736 in combination with tremelimumab in patients with metastatic HER2-negative breast cancer. Both MEDI4736 and tremelimumab are antibodies (proteins used by the immune system to fight infections and cancers). MEDI4736 attaches to a protein in tumors called PD-L1. It may prevent cancer growth by helping certain blood cells of the immune system get rid of the tumor. Tremelimumab stimulates (wakes up) the immune system to attack the tumor by inhibiting a protein molecule called CTLA-4 on immune cells. Combining the actions of these drugs may result in better treatment options for patients with breast cancer.