This notion has been elegantly exemplified by the success of PARP inhibitors in BRCA-mutant cancers, that has represented the first example of a synthetic lethality-based therapeutic approach, resulting in the approval of the PARP-1 inhibitor olaparib for the treatment of advanced-stage, BRCA1/2-mutant ovarian cancers in 2014 [80]. The gene discussed is PARP1; the disease is ovarian cancer.