AAV‐mediated expression of galactose‐1‐phosphate uridyltransferase corrects defects of galactose metabolism in classic galactosemia patient fibroblasts

Classic galactosemia (CG) is a rare disorder of autosomal recessive inheritance. It is caused predominantly by point mutations as well as deletions in the gene encoding the enzyme galactose‐1‐phosphate uridyltransferase (GALT). The majority of the more than 350 mutations identified in the GALT gene cause a significant reduction in GALT enzyme activity resulting in the toxic buildup of galactose metabolites that in turn is associated with cellular stress and injury. Consequently, developing a therapeutic strategy that reverses both the oxidative and ER stress in CG cells may be helpful in combating this disease. Recombinant adeno‐associated virus (AAV)‐mediated gene therapy to restore GALT activity offers the potential to address the unmet medical needs of galactosemia patients. Here, utilizing fibroblasts derived from CG patients we demonstrated that AAV‐mediated augmentation of GALT protein and activity resulted in the prevention of ER and oxidative stress. We also demonstrate that these CG patient fibroblasts exhibit reduced CD109 and TGFβRII protein levels and that these effectors of cellular homeostasis could be restored following AAV‐mediated expression of GALT. Finally, we show initial in vivo proof‐of‐concept restoration of galactose metabolism in a GALT knockout mouse model following treatment with AAV‐GALT.