Liver-directed gene therapy corrects Fabry disease in mice

Fabry disease is an X-linked lysosomal storage disorder (LSD) resulting from mutations in the gene encoding for α-galactosidase A (GLA). It is characterised by the abnormal accumulation of neutral glycosphingolipids (GSL), predominantly Globotriaosylceramide (Gb3), in the lysosomes of multiple cell types including vascular endothelial cells. It is associated with early-onset stroke, cardiomyopathy, and progression to end-stage renal failure. We examined the therapeutic efficacy of GLA gene therapy in Fabry mice using recombinant adeno-associated virus (rAAV) vectors, directed by the liver-specific promoter (FRE1). In this study, we showed that a single intravenous (IV) injection of rAAV8-FRE1-GLAco (2x1012 vg/kg) achieved supraphysiological levels of plasma GLA activity up to 1061-fold of normal with concomitant correction of lysosomal storage pathology in multiple key organs in a Fabry mouse model. Animals injected with our novel codon-optimised (“GLAco”) GLA construct exhibited a rapid elevation in plasma GLA activity levels reaching a peak level by 4 weeks post-injection, and this level of expression was maintained for the duration of the study (14 weeks). Furthermore, mass spectrometry (LC-MC/MS) analysis of GSL extract from different tissues provided proof of exposure and storage clearance in various key organs, which is indicative of metabolic cross-correction of liver-derived GLA enzyme. Gb3 levels in the plasma were reduced by 91% (p=0.008) in the kidney by 64% (p=0.045) in the heart by 98% (p