Idursulfase for enzyme-replacement therapy in mucopolysaccharidosis II

J Edmond Wraith

Hunter syndrome (mucopolysaccharidosis II) is a rare, X-linked disorder caused by the missing or deficient lysosomal enzyme, iduronate-2-sulfatase, which leads to tissue and organ accumulation of glycosaminoglycans, resulting in multisystem dysfunction with death occurring most commonly in the first or second decade of life. Enzyme-replacement therapy with idursulfase (recombinant human iduronate-2-sulfatase) has been shown in a Phase II/III clinical trial to statistically significantly improve the primary end point – the sum of ranked changes in 6-min walking test distance and ranked changes in percentage predicted forced vital capacity compared with placebo – with the improvement being larger in the group treated with weekly doses compared with those treated every other week. Significant reductions in spleen and liver volume were also observed. Suspected hypersensitivity reactions were observed during the infusions in some patients, but were successfully managed, and no patients discontinued therapy. Idursulfase is now approved in the USA and EU and may offer the opportunity to affect the progression of Hunter disease in treated patients.