BRCA1 and breast cancer: Olaparib, a poly ADP ribose polymerase (PARP) inhibitor, has recently been approved in the treatment of patients with BRCA1 and BRCA2 mutant breast cancer.27 Olaparib has been shown to be specifically toxic to BRCA1/2 mutant cells by generating DNA lesions, in part due to its PARP-trapping activity, that require homologous recombination for efficient repair.