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

Purpose: 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. Methods: 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. Results: 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 mu g/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. Conclusion: No new safety concerns were identified in patients younger than 6 years, and clinical benefit was suggested by the reduction in liver size. Genet Med 2011:13(2):102-109.