MEDI4736, an anti-PD-L1 checkpoint inhibitor made by MedImmune/AstraZeneca, is being tested in three trials: a phase I trial of MEDI4736 for patients with solid tumors, including breast cancer (NCT01693562); a phase I trial of MEDI0680 (AMP-514), an anti-PD-1 antibody, and MEDI4736 in patients with advanced cancers (NCT02118337); and a phase I/II trial of MEDI6469, an anti-OX40 agonist antibody, alone or with tremelimumab, an anti-CTLA-4 antibody, and/or MEDI4736 (NCT02205333). This evidence concerns the gene CTLA4 and breast cancer.