CTLA4 and breast cancer: Some recent examples include the addition of pertuzumab to trastuzumab for the treatment of human epidermal growth factor receptor-2 (HER-2)-positive breast cancer and the use of programmed cell death protein (PD-1) and programmed cell death ligand (PD-L1) inhibitors in combination with anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) therapies in metastatic melanoma.