In patients with HER2-negative (human epidermal growth factor receptor type 2) metastatic breast cancer and a germline BRCA mutation, olaparib monotherapy significantly improved progression-free survival compared with standard single-agent chemotherapy. Reported in the New England Journal of Medicine, the phase 3 trial is the first in which a poly(adenosine diphosphate–ribose) polymerase (PARP) inhibitor has shown a significant benefit other than for patients with ovarian cancer. PARP inhibitors interfere with DNA repair in cancer cells, leading to cancer cell death.