Enzyme replacement therapy outcomes across the disease spectrum: Findings from the mucopolysaccharidosis VI Clinical Surveillance Program.

The impact of galsulfase enzyme replacement therapy in patients with mucopolysaccharidosis (MPS) VI with phenotypes at either end of the disease spectrum was evaluated. The MPS VI Clinical Surveillance Program (CSP) was established to collect long-term observational data from routine clinical and laboratory assessments. A subanalysis of the CSP was performed in patients with pretreatment urinary glycosaminoglycan (uGAG) levels <100 μg/mg and ≥200 μg/mg creatinine (low- and high-uGAG) who had received galsulfase for ≥6 months. uGAG, 6-minute walk test (6MWT), 3-minute stair climb test (3MSCT), pulmonary function measures, height/growth, cardiac function, and safety were evaluated. Patients with a high-uGAG level at pre-treatment baseline (N = 68) showed greater impairments in endurance and pulmonary function than those with low-baseline uGAG levels (N = 39). From pre-treatment baseline, the distance walked on the 6MWT in the low- and high-uGAG groups increased by a mean (±SD) of 49 (±151) meters and 42 (±165) meters (median follow-up 5.5 and 7.7 years), respectively. The number of stairs/min climbed in the 3MSCT in the low- and high-uGAG groups increased by a mean of 18 (±33) and 30 (±45) (median follow-up 2.8 and 3.5 years), respectively. Overall, pulmonary function remained unchanged for both groups. No impact was seen on cardiac function. Galsulfase was generally well tolerated in both groups, with most adverse events being MPS-related complications unrelated to galsulfase. Results of this CSP sub-analysis suggest that galsulfase stabilizes MPS VI in the long-term and has an acceptable safety profile, regardless of baseline disease severity.