The CRISPR–Cas9 system enables programmable genetic and epigenetic manipulations which present exciting opportunities for personalized therapeutics. As CRISPR–Cas9 approaches the clinic, efficacy and safety for the patient are overriding. On that note, many have endeavored to deploy CRISPR–Cas9 with adeno-associated virus (AAV), delivery vectors that are prevalent, serologically compatible with a large fraction of the human population, and generally considered nonpathogenic. Besides, AAVs allow semiselective tissue tropism via local or systemic delivery.