indication

For the treatment of Hunter syndrome in adults and children ages 5 and older.

pharmacology

Idursulfase is a purified form of the lysosomal enzyme human iduronate-2-sulfatase of recombinant DNA origin. It is designed to replace the natural enzyme, increasing catabolism of certain accumulated glycosaminoglycans (GAG), which abnormally accumulate in multiple tissue types in patients with mucopolysaccharidosis II (MPS-II, or Hunter syndrome).

mechanism of action

Hunter's Syndrome is an X-linked recessive disease caused by insufficient levels of the lysosomal enzyme iduronate-2-sulfatase. This enzyme cleaves the terminal 2-O-sulfate moieties from the glycosaminoglycans (GAG) dermatan sulfate and heparan sulfate. Due to the missing or defective iduronate-2-sulfatase enzyme in patients with Hunter's Syndrome, GAG progressively accumulate in the lysosomes of a variety of cells, leading to cellular engorgement, organomegaly, tissue destruction and organ system dysfunction. Treatment of Hunter's Syndrome patients with idursulfase provides exogenous enzyme for uptake into cellular lysosomes. Targeting of idursulfase to the lysosome occurs by endocytosis from the cell surface. Mannose-6-phosphate (M6P) residues on the oligosaccharide chains allow specific binding of the enzymes to the M6P receptors on the cell surface, leading to cellular internalization of the enzyme, targeting to intracellular lysosomes and subsequent catabolism of accumulated GAG.

toxicity

There is no experience with overdosage of Idursulfase in humans. Single intravenous doses of idursulfase up to 20 mg/kg were not lethal in male rats and cynomolgus monkeys (approximately 6.5 and 13 times, respectively, of the recommended human dose based on body surface area) and there were no clinical signs of toxicity.

half life

44 ± 19 minutes