A retrospective analysis of the potential impact of IgG antibodies to agalsidase β on efficacy during enzyme replacement therapy for Fabry disease

Fabry disease results from a genetic deficiency of α-galactosidase A (αGAL) and the impaired catabolism of globotriasoylceramide (GL-3) and other glycosphingolipid substrates, which then accumulate pathogenically within most cells. Enzyme replacement therapy (ERT) with agalsidase β (Fabrazyme®), one of two available forms of recombinant human αGAL, involves regular intravenous infusions of the therapeutic protein. Immunoglobulin G (IgG) antibodies to recombinant αGAL develop in the majority of patients upon repeated infusion. To explore whether anti-αGAL IgG interferes with therapeutic efficacy, retrospective analyses were conducted using data obtained from a total of 134 adult male and female patients with Fabry disease who were treated with agalsidase β at 1 mg/kg every 2 weeks for up to 5 years during placebo-controlled trials and the corresponding open-label extension studies. The analyses did not reveal a correlation between anti-αGAL IgG titers and the onset of clinical events or the rate of change in estimated GFR during treatment, and no statistically significant association was found between anti-αGAL IgG titers and abnormal elevations in plasma GL-3 during treatment. However, a statistically significant association was found between anti-αGAL IgG titers and observation of some GL-3 deposition in the dermal capillary endothelial cells of skin during treatment, suggesting that GL-3 clearance may be partially impaired in some patients with high antibody titers. Determination of the long-term impact of circulating anti-αGAL IgG antibodies on clinical outcomes will require continued monitoring, and serology testing is recommended as part of the routine care of Fabry disease patients during ERT.