Agalsidase alfa: a review of its use in the management of Fabry disease.

The enzyme replacement therapy agalsidase alfa (Replagal®) has an amino acid sequence identical to that of native α-galactosidase A; intravenous agalsidase alfa 0.2 mg/kg every other week is indicated for the long-term treatment of patients with confirmed Fabry disease. This article reviews the efficacy and tolerability of agalsidase alfa in patients with Fabry disease, as well as summarizing its pharmacologic properties. Agalsidase alfa had beneficial effects in adult men with Fabry disease, according to the results of two randomized, double-blind, placebo-controlled, 6-month trials (n = 15 and 26). For example, left ventricular mass index was reduced to a significantly greater extent with agalsidase alfa than with placebo. Although the change in myocardial globotriaosylceramide content (primary endpoint in one study) did not significantly differ between agalsidase alfa and placebo recipients, the change in the Brief Pain Inventory (BPI) 'pain at its worst' score (reflecting neuropathic pain while without pain medications; primary endpoint in the second study) was improved to a significantly greater extent with agalsidase alfa than with placebo. In addition, the change in creatinine clearance, but not inulin clearance, significantly favored agalsidase alfa versus placebo recipients. Abnormalities in functional cerebral blood flow and cerebrovascular responses were also reversed with agalsidase alfa therapy. In extensions of these placebo-controlled trials, the reduction in left ventricular mass and improvements in BPI pain scores were maintained after longer-term agalsidase alfa therapy. The significant decline in estimated glomerular filtration rate (eGFR) seen after 48 months' agalsidase alfa treatment was mainly driven by a marked decline in eGFR seen in four patients with stage 3 chronic kidney disease at baseline (although the progression of decline appeared slower than that seen in historic controls); renal function appeared stable in patients with stage 1 or 2 chronic kidney disease. Certain benefits of agalsidase alfa became apparent with longer-term therapy. For example, a significant reduction in cold and warm detection thresholds and a significant improvement in sweat function were seen after 3 years' therapy. Final results from a head-to-head trial comparing the effects of agalsidase alfa and agalsidase beta at approved dosages are not yet available. The only available fully published study compared agalsidase alfa 0.2 mg/kg every other week with an off-label dosage of agalsidase beta 0.2 mg/kg every other week. This randomized, open-label, 24-month trial in adult men and women with Fabry disease generally found no significant differences in outcome between treatment arms. It should be noted that concerns were subsequently raised by the European Medicines Agency regarding the use of agalsidase beta at dosages other than the approved dosage of 1 mg/kg every other week. Preliminary results from an ongoing, randomized, open-label study suggest no differences in outcome between patients with Fabry disease receiving intravenous agalsidase alfa 0.2 mg/kg every other week and those receiving the approved regimen of agalsidase beta 1 mg/kg every other week. In three switching studies, no safety concerns were raised and disease stability was generally maintained following the switch from agalsidase beta 1 mg/kg every other week to agalsidase alfa 0.2 mg/kg every other week. Agalsidase alfa also demonstrated beneficial effects, including in women and pediatric patients, in noncomparative studies and in the Fabry Outcome Survey. Agalsidase alfa was generally well tolerated in patients with Fabry disease, with infusion reactions (e.g. rigors, pyrexia, flushing) being the most commonly occurring adverse event. IgG antibodies developed in ≈24% of male patients with Fabry disease who received agalsidase alfa. After 12-54 months of treatment, 17% of agalsidase alfa recipients were still IgG antibody positive, with immunologic tolerance developing in 7% of agalsidase alfa recipients. No IgE antibodies have been detected in any patient receiving agalsidase alfa. No antibody formation was reported in women receiving agalsidase alfa in noncomparative studies. In conclusion, agalsidase alfa is an effective and well tolerated treatment option for use in patients with Fabry disease.