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4/25/2003

Treatment for Fabry's Disease Approved

Cheryl A. Thompson

Agalsidase beta, a pharmaceutical with the same amino acid sequence as the enzyme whose deficiency leads to Fabry's disease, was approved yesterday by the Food and Drug Administration. Genzyme Corp. will market the product under the brand name Fabrazyme (PDF).

Fabry's disease is a rare genetic disorder resulting from insufficient production of alpha-galactosidase A, an enzyme essential to the breakdown of certain lipids, including ceramide trihexoside, also known as globotriaosylceramide (GL-3). Over time in persons with the enzyme deficiency, GL-3 accumulates in plasma and the cells lining the tiny blood vessels in the kidneys, heart, skin, and other organs. According to the National Tay-Sachs & Allied Diseases Association, persons with Fabry's disease commonly die of renal and cardiac failure before the age of 45, although some patients live into their 60s.

The labeling for agalsidase beta states that the product is for use in patients with Fabry's disease to reduce deposits of GL-3 in the capillary endothelium of the kidney and certain other types of cells.

There are no known contraindications to therapy with agalsidase beta.

The recommended dosage of agalsidase beta is 1 mg per kilogram of body weight administered by intravenous infusion every two weeks. According to the product's labeling, each dose should be diluted to a total volume of 500 mL and infused at a rate no faster than 0.25 mg/min (or 15 mg/hr). A dose for a 70-kg patient, for example, should be administered over at least 4 hours and 20 minutes.

During the major study of agalsidase beta in patients with Fabry's disease, 48 percent of those who received the drug had a fever, 52 percent had rigors, and 45 percent had a headache. The instructions for administration of the drug state that patients should receive antipyretics before the infusion starts and that, once tolerance to the infusion has been well established, the delivery rate can be increased in increments of 0.05–0.08 mg/min (or 3–5 mg/hr) with each subsequent dose.

Genzyme said Fabrazyme will be available, starting June 1, in single-use glass vials containing 35 mg of agalsidase beta and requiring storage at 2–8 degrees Centigrade.