BRCA1 and cancer: Given that DNA repair genes are frequently mutated in cancer, and that mutations in the major DSB repair pathway regulators—BRCA1/2 (HR), PRKDC (NHEJ), and POLQ (MMEJ)—account for 11% of all cancers61 (Fig. 5b), we set out to investigate the potential of repurposed drugs to exhibit synthetic lethality.