Repurposing of clinically safe drugs for CRISPR/Cas9 editing

We evaluated the effect of most FDA-approved drugs (>7,000 conditions) on double-strand DNA breakrepair pathways by analyzing mutational outcomes in human induced pluripotent stem cells. We identifieddrugs that can be repurposed as inhibitors and enhancers of repair outcomes attributed to non-homologousand microhomology-mediated end joining (NHEJ, MMEJ), and homology-directed repair (HDR). We alsoidentified novel functions of the proteins estrogen receptor 2 (ESR2) and aldehyde oxidase 1 (AOX1),affecting several key DNA repair proteins, such as ATM and 53BP1. Silencing of ESR2 can have asynergistic effect on increasing HDR when combined with NHEJ inhibition (mean 4.6-fold increase). Wefurther identified drugs that induce synthetic lethality when NHEJ or HDR is blocked and may therefore becandidates for precision medicine. We anticipate that the ability to modulate the DNA repair outcomes withclinically safe drugs will help disease modeling, gene therapy, chimeric antigen receptor immunotherapy,and cancer treatment.