AAV2/6 Gene Therapy in a Murine Model of Fabry Disease Results in Supraphysiological Enzyme Activity and Effective Substrate Reduction

• Main Authors: Makiko Yasuda, Marshall W. Huston, Silvere Pagant, Lin Gan, Susan St. Martin, Scott Sproul, Daniel Richards, Stephen Ballaron, Khaled Hettini, Annemarie Ledeboer, Lillian Falese, Liching Cao, Yanmei Lu, Michael C. Holmes, Kathleen Meyer, Robert J. Desnick, Thomas Wechsler
• Format: Article
• Language: English
• Published: Elsevier 2020-09-01
• Series: Molecular Therapy: Methods & Clinical Development
• Subjects: AAV gene therapy; GLA; alpha galactosidase A; Fabry; preclinical studies; GLAKO mouse
• Online Access: http://www.sciencedirect.com/science/article/pii/S2329050120301510

Fabry disease is an X-linked lysosomal storage disorder caused by mutations in the alpha-galactosidase A (GLA) gene, which encodes the exogalactosyl hydrolase, alpha-galactosidase A (α-Gal A). Deficient α-Gal A activity results in the progressive, systemic accumulation of its substrates, globotriaosylceramide (Gb3) and globotriaosylsphingosine (Lyso-Gb3), leading to renal, cardiac, and/or cerebrovascular disease and early demise. The current standard treatment for Fabry disease is enzyme replacement therapy, which necessitates lifelong biweekly infusions of recombinant enzyme. A more long-lasting treatment would benefit Fabry patients. Here, a gene therapy approach using an episomal adeno-associated viral 2/6 (AAV2/6) vector that encodes the human GLA cDNA driven by a liver-specific expression cassette was evaluated in a Fabry mouse model that lacks α-Gal A activity and progressively accumulates Gb3 and Lyso-Gb3 in plasma and tissues. A detailed 3-month pharmacology and toxicology study showed that administration of a clinical-scale-manufactured AAV2/6 vector resulted in markedly increased plasma and tissue α-Gal A activities, and essentially normalized Gb3 and Lyso-Gb3 at key sites of pathology. Further optimization of vector design identified the clinical lead vector, ST-920, which produced several-fold higher plasma and tissue α-Gal A activity levels with a good safety profile. Together, these studies provide the basis for the clinical development of ST-920.