Idursulfase treatment of Hunter syndrome in children younger than 6 years: results from the Hunter Outcome Survey.

Abstract

To use the Hunter Outcome Survey, an international database, to assess the safety and effectiveness of enzyme replacement therapy with idursulfase in patients with Hunter syndrome who started treatment before 6 years of age. The study population included all patients enrolled in the Hunter Outcome Survey who started idursulfase infusions (0.5 mg/kg every other week) before 6 years of age and who had at least one follow-up examination recorded. The study population included 124 patients, younger than 6 years, who had a mean age at start of idursulfase of 3.6 ± 1.6 years (mean ± SD). The mean duration of treatment was 22.9 ± 14.6 months. A total of 69 infusion-related reactions occurred in 33 (26.6%) patients, including three serious infusion-related reactions occurring in a single patient. After at least 6 months of idursulfase, urine glycosaminoglycan levels decreased from 592 ± 188 to 218 ± 115 μg/mg creatinine (P < 0.0001, n = 34). Liver size, estimated by palpation, was also significantly decreased (P = 0.005, n = 23). Similar safety and effectiveness results were seen in patients who were aged 6 years or older when initiating idursulfase. No new safety concerns were identified in patients younger than 6 years, and clinical benefit was suggested by the reduction in liver size.