The seminal discovery of synthetic lethality between defective homologous recombination (HR) and chemical inhibition of poly(ADP-ribose) polymerases (PARPs) led to the development of clinical PARP inhibitors (PARPis) that represent a significant breakthrough in the therapy of familial breast and ovarian cancers linked to mutations in the BRCA1/2 genes (1–3). The gene discussed is BRCA1; the disease is ovarian cancer.