Enzyme replacement therapy initiated in adulthood: Findings from the mucopolysaccharidosis VI Clinical Surveillance Program

Objective: To evaluate the impact of galsulfase enzyme replacement therapy (ERT) when initiated in adulthood for patients with mucopolysaccharidosis (MPS) VI. Methods: In 2005, the multi-national, MPS VI Clinical Surveillance Program (CSP) was established to collect long-term observational data from routine clinical and laboratory assessments. A sub-analysis was performed in patients who started ERT at >= 16 years of age and had received galsulfase for >= 6 months. Urinary glycosaminoglycans (uGAG), 6-min walk test (6MWT), 3-min stair climb test (3MSCT), pulmonary function measures, cardiac function, ophthalmology measures, liver and spleen sizes, and safety were evaluated. Results: Of 223 patients enrolled in the CSP, 51 were included in the sub-analysis. Patients were between 16 and 63 years of age at first infusion. From pre-treatment baseline, uGAG level decreased by a mean (+/- standard deviation [SD]) of 66 (+/- 45)% (N = 29) after a median follow-up of 7.2 years. 6MWT distance decreased slightly by a mean of 17 (+/- 107) meters (N = 23) after 6.6 years. Stairs/min in the 3MSCT increased by a mean of 26 (+/- 33) (N = 14) after 2.8 years. Pulmonary function measures, forced expiratory volume in 1 second and forced vital capacity, increased by a mean of 0.06 (+/- 0.21) L after 7.3 years and 0.05 (+/- 0.28) L after 7.2 years, respectively (N = 19 for both measures). Overall, galsulfase was well tolerated, with most adverse events reported being MPS-related clinical manifestations and not related to galsulfase. Conclusions: Results of this sub-analysis of the CSP suggest that initiation of galsulfase in adulthood is well tolerated and can possibly stabilize MPS VI in the long term.