Myozyme (alglucosidase alfa) consists of the human enzyme acid alpha-glucosidase (GAA), encoded by the most predominant of nine observed haplotypes of this gene. Myozyme is formed by recombinant DNA technology in a Chinese hamster ovary cell line. Myozyme degrades glycogen by catalyzing the hydrolysis of alpha 1,4 and alpha 1,6 glycosidic linkages of lysosomal glycogen.

Myozyme is a glycoprotein with a calculated mass of 99,377 daltons for the polypeptide chain, and a total mass of approximately 109,000 daltons, including carbohydrates. Myozyme has a specific activity of 3 to 5 U/mg (one unit is defined as that amount of activity that results in the hydrolysis of 1 ?mole of synthetic substrate per minute under the specified assay conditions). Myozyme is intended for intravenous infusion. It is supplied as a sterile, nonpyrogenic, white to off-white, lyophilized cake or powder for reconstitution with 10.3 mL Sterile Water for Injection. Each 50 mg vial contains 52.5 mg alglucosidase alfa, 210 mg mannitol, 0.5 mg polysorbate 80, 9.9 mg sodium phosphate dibasic heptahydrate, and 31.2 mg sodium phosphate monobasic monohydrate. Following reconstitution as directed, each vial contains 10.5 mL reconstituted solution and a total extractable volume of 10 mL at 5.0 mg/mL alglucosidase alfa. Myozyme does not contain preservatives; each vial is only for single use.

Mechanism of Action

Pompe disease is an inherited disorder of glycogen metabolism caused by the absence or marked deficiency of the lysosomal enzyme GAA. Binding to mannose-6-phosphate receptors on the cell surface has been revealed to occur via carbohydrate groups on the GAA molecule, after which it is internalized and transported into lysosomes, where it undergoes proteolytic cleavage, which results in increased enzymatic activity.