Gaucher disease is caused by mutations in the gene that encodes the lysosomal enzyme acid b-glucosidase (GCase). We have shown previously that the small molecule pharmacological chaperone isofagomine (IFG) binds and stabilizes N370S GCase, resulting in increased lysosomal trafficking and cellular activity. In this study, we investigated the effect of IFG on L444P GCase. Incubation of Gaucher patient-derived lymphoblastoid cell lines (LCLs) or fibroblasts with IFG led to approximately 3.5-and 1.3-fold increases in L444P GCase activity, respectively, as measured in cell lysates. The effect in fibroblasts was increased approximately 2-fold using glycoprotein-enrichment, GCase-immunocapture, or by incubating cells overnight in IFG-free media prior to assay, methods designed to maximize GCase activity by reducing IFG carryover and inhibition in the enzymatic assay. IFG incubation also increased the lysosomal trafficking and in situ activity of L444P GCase in intact cells, as measured by reduction in endogenous glucosylceramide levels. Importantly, this reduction was seen only following three-day incubation in IFG-free media, underscoring the importance of IFG removal to restore lysosomal GCase activity. In mice expressing murine L444P GCase, oral administration of IFG resulted in significant increases (2-to 5-fold) in GCase activity in disease-relevant tissues, including brain. Additionally, eight-week IFG administration significantly lowered plasma chitin III and IgG levels, and 24-week administration significantly reduced spleen and liver weights. Taken together, these data suggest that IFG can increase the lysosomal activity of L444P GCase in cells and tissues. Moreover, IFG is orally available and distributes into multiple tissues, including brain, and may thus merit therapeutic evaluation for patients with neuronopathic and non-neuronopathic Gaucher disease.

Fabry disease is an X-linked lysosomal storage disorder caused by a deficiency in alpha-galactosidase A (alpha-Gal A) activity and subsequent accumulation of the substrate globotriaosylceramide (GL-3), which contributes to disease pathology. The pharmacological chaperone (PC) DGJ (1-deoxygalactonojirimycin) binds and stabilizes alpha-Gal A, increasing enzyme levels in cultured cells and in vivo. The ability of DGJ to reduce GL-3 in vivo was investigated using transgenic (Tg) mice that express a mutant form of human alpha-Gal A (R301Q) on a knockout background (Tg/KO), which leads to GL-3 accumulation in disease-relevant tissues. Four-week daily oral administration of DGJ to Tg/KO mice resulted in significant and dose-dependent increases in alpha-Gal A activity, with concomitant GL-3 reduction in skin, heart, kidney, brain, and plasma; 24-week administration resulted in even greater reductions. Compared to daily administration, less frequent DGJ administration, including repeated cycles of 4 days with DGJ followed by 3 days without or every other day with DGJ, resulted in even greater GL-3 reductions that were comparable to those obtained with Fabrazyme. Collectively, these data indicate that oral administration of DGJ increases mutant alpha-Gal A activity and reduces GL-3 in disease-relevant tissues in Tg/KO mice, and thus merits further evaluation as a treatment for Fabry disease.

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Fabry disease is an X-linked lysosomal storage disorder (LSD) caused by mutations in the gene (GLA) that encodes the lysosomal hydrolase α-galactosidase A (α-Gal A), and is characterized by pathological accumulation of the substrate, globotriaosylceramide (GL-3). Regular infusion of recombinant human α-Gal A (rhα-Gal A), termed enzyme replacement therapy (ERT), is the primary treatment for Fabry disease. However, rhα-Gal A has low physical stability, a short circulating half-life, and variable uptake into different disease-relevant tissues. We hypothesized that coadministration of the orally available, small molecule pharmacological chaperone AT1001 (GR181413A, 1-deoxygalactonojirimycin, migalastat hydrochloride) may improve the pharmacological properties of rhα-Gal A via binding and stabilization. AT1001 prevented rhα-Gal A denaturation and activity loss in vitro at neutral pH and 37 °C. Coincubation of Fabry fibroblasts with rhα-Gal A and AT1001 resulted in up to fourfold higher cellular α-Gal A and ~30% greater GL-3 reduction compared to rhα-Gal A alone. Furthermore, coadministration of AT1001 to rats increased the circulating half-life of rhα-Gal A by >2.5-fold, and in GLA knockout mice resulted in up to fivefold higher α-Gal A levels and fourfold greater GL-3 reduction than rhα-Gal A alone. Collectively, these data highlight the potentially beneficial effects of AT1001 on rhα-Gal A, thus warranting clinical investigation.

Pompe disease is an inherited lysosomal storage disease that results from a deficiency in the enzyme acid α-glucosidase (GAA), and is characterized by progressive accumulation of lysosomal glycogen primarily in heart and skeletal muscles. Recombinant human GAA (rhGAA) is the only approved enzyme replacement therapy (ERT) available for the treatment of Pompe disease. Although rhGAA has been shown to slow disease progression and improve some of the pathophysiogical manifestations, the infused enzyme tends to be unstable at neutral pH and body temperature, shows low uptake into some key target tissues, and may elicit immune responses that adversely affect tolerability and efficacy. We hypothesized that co-administration of the orally-available, small molecule pharmacological chaperone AT2220 (1-deoxynojirimycin hydrochloride, duvoglustat hydrochloride) may improve the pharmacological properties of rhGAA via binding and stabilization. AT2220 co-incubation prevented rhGAA denaturation and loss of activity in vitro at neutral pH and 37°C in both buffer and blood. In addition, oral pre-administration of AT2220 to rats led to a greater than two-fold increase in the circulating half-life of intravenous rhGAA. Importantly, co-administration of AT2220 and rhGAA to GAA knock-out (KO) mice resulted in significantly greater rhGAA levels in plasma, and greater uptake and glycogen reduction in heart and skeletal muscles, compared to administration of rhGAA alone. Collectively, these preclinical data highlight the potentially beneficial effects of AT2220 on rhGAA in vitro and in vivo. As such, a Phase 2 clinical study has been initiated to investigate the effects of co-administered AT2220 on rhGAA in Pompe patients.