Fah–/– mice were rescued by transplanting gene-corrected hepatocytes co-transduced ex vivo using lentiviral vectors containing Fah-aiming CRISPR-Cas9 and AAV vector containing a donor template.32 In a separate study, hepatocytes transduced utilizing a pair of AAVs to deliver Fah-CRISPR-Cas9 and donor template followed by culturing for up to 72 h were capable of engraftment in vivo and prevented liver failure.33 These studies demonstrate the feasibility of ex vivo gene editing in hepatocytes to treat IMDs of the liver. This evidence concerns the gene FAH and liver failure.