Infusion of alpha-galactosidase A reduces tissue globotriaosylceramide storage in patients with Fabry disease

Abstract

Fabry disease is a lysosomal storage disorder caused by a deficiency of the lysosomal enzyme alpha-galactosidase A (alpha-gal A). This enzymatic defect results in the accumulation of the glycosphingolipid globotriaosylceramide (Gb(3); also referred to as ceramidetrihexoside) throughout the body. To investigate the effects of purified alpha-gal A, 10 patients with Fabry disease received a single i.v. infusion of one of five escalating dose levels of the enzyme. The objectives of this study were: (i) to evaluate the safety of administered alpha-gal A, (ii) to assess the pharmacokinetics of i.v.-administered alpha-gal A in plasma and liver, and (iii) to determine the effect of this replacement enzyme on hepatic, urine sediment and plasma concentrations of Gb(3). alpha-Gal A infusions were well tolerated in all patients. Immunohistochemical staining of liver tissue approximately 2 days after enzyme infusion identified alpha-gal A in several cell types, including sinusoidal endothelial cells, Kupffer cells, and hepatocytes, suggesting diffuse uptake via the mannose 6-phosphate receptor. The tissue half-life in the liver was greater than 24 hr. After the single dose of alpha-gal A, nine of the 10 patients had significantly reduced Gb(3) levels both in the liver and shed renal tubular epithelial cells in the urine sediment. These data demonstrate that single infusions of alpha-gal A prepared from transfected human fibroblasts are both safe and biochemically active in patients with Fabry disease. The degree of substrate reduction seen in the study is potentially clinically significant in view of the fact that Gb(3) burden in Fabry patients increases gradually over decades. Taken together, these results suggest that enzyme replacement is likely to be an effective therapy for patients with this metabolic disorder.

Figure 1

Analysis of α-gal A by SDS/PAGE. α-gal A was reduced and analyzed on 4–15% polyacrylamide gels. (A) 0.6 μg of α-gal was loaded and visualized with silver stain. Molecular mass markers are in the left lane. (B) 0.08 μg of α-gal A was subjected to electrophoresis and transferred to an Immobilon-P poly(vinylidene difluoride) membrane. Western blotting was performed by using polyclonal antibodies specific for human α-gal A.

Figure 2

Plasma pharmacokinetics of α-gal A. Each of 10 patients received a single dose of purified α-gal A by i.v. infusion. C_max (A) and AUC_∞ (B) are plotted against dose.

Figure 3

Immunohistochemical localization of α-gal A. A polyclonal rabbit anti-human α-gal A antibody was used to stain liver biopsy sections from a patient in the study (A) just before treatment with α-gal A and (B) 44 hr after treatment with α-gal A.