Base editing strategies for in vivo correction of two highly recurrent phenylketonuria variants

Phenylketonuria (PKU) is an autosomal recessive disorder caused by mutations in the phenylalanine hydroxylase (<i>PAH</i>) gene. Previously, we have shown correction of the most recurrent PKU variant using both base editing and prime editing. In this work, we set out to screen base editors and single guide RNAs (sgRNAs) <i>in vitro</i> to identify sgRNA-editor combinations that would provide sufficient correction for phenotypic rescue of the next four most recurrent PKU variants. For three candidates, we established efficient corrective editing <i>in vitro</i>. We then assessed the off-target editing profile of each sgRNA-editor combination. For two of these variants, we demonstrated efficient corrective editing in the livers of humanized mouse models via adeno-associated viral (AAV) delivery. This work identifies base editing strategies for <i>in vivo</i> correction of the second and third most common pathogenic variants of PKU.