Idursulfase in Hunter syndrome treatment.

Hunter syndrome (mucopolysaccharidosis II, MPS II) is a rare X-linked lysosomal storage disorder caused by the deficiency of enzyme iduronate-2-sulfatase (I2S), which results in accumulation of undegraded dermatan and heparan sulfate in various tissues and organs. Enzyme replacement therapy with Elaprase (idursulfase, a recently approved orphan product) is the first treatment for Hunter syndrome. Results of the randomized, double-blind, placebo-controlled phase II/III clinical trial of idursulfase demonstrated that weekly infusions of idursulfase increase walking distance and improve pulmonary function as well as reduce organ size and urinary glycosaminoglycans (GAGs) excretion in MPS II patients. Idursulfase is generally well tolerated, although infusion reactions do occur. Clinical studies demonstrate that idursulfase may be the first successful symptomatic therapy that can benefit patients with MPS II by addressing the enzymatic defect.