Systematic gene therapy derived from an investigative study of AAV2/8 vector gene therapy for Fabry disease

Fabry disease (FD) is a progressive multisystemic disease characterized by a lysosomal enzyme deficiency. A lack of α-galactosidase A (α-Gal A) activity results in the progressive systemic accumulation of its substrates, including globotriaosylceramide (Gb3) and globotriaosylsphingosine (Lyso-Gb3), which results in renal, cardiac, and/or cerebrovascular disease and early death. Enzyme replacement therapy (ERT) is the current standard of care for FD; however, it has important limitations, including a low half-life, limited distribution, and requirement of lifelong biweekly infusions of recombinant enzymes.Herein, we evaluated a gene therapy approach using an episomal adeno-associated viral 2/8 (AAV2/8) vector that encodes the human GLA cDNA driven by a liver-specific expression cassette in a mouse model of FD that lacks α-Gal A activity and progressively accumulates Gb3 and Lyso-Gb3 in plasma and tissues.A pharmacology and toxicology study showed that administration of AAV2/8-hGLA vectors (AAV2/8-hGLA) in FD mice without immunosuppression resulted in significantly increased plasma and tissue α-Gal A activity and substantially normalized Gb3 and Lyso-Gb3 content.Moreover, the plasma enzymatic activity of α-Gal A continued to be stably expressed for up to 38 weeks and sometimes even longer, indicating that AAV2/8-hGLA is effective in treating FD mice, and that α-Gal A is continuously and highly expressed in the liver, secreted into plasma, and absorbed by various tissues. These findings provide a basis for the clinical development of AAV2/8-hGLA.