PARP inhibitors are the first clinically approved cancer drugs designed to exploit synthetic lethality.426 At present, PARP inhibitors therapy has been successfully used to treat advanced breast and ovarian cancer patients harboring BRCA1/2 mutations and exhibiting homologous recombination (HR) deficiency.427 But some of these patients showed signs of resistance that limit the efficacy of PARP inhibitor monotherapy. The gene discussed is PARP1; the disease is cancer.