To date, five PARP inhibitors (olaparib, rucaparib, niraparib, talazoparib and veliparib) have been approved by the United States Food and Drug Administration (FDA) as single agents for the treatment of cancers with defects in homologous recombination (HRD), such as those bearing BRCA1/2 mutations. The gene discussed is PARP1; the disease is cancer.