MLD is an inherited, autosomal recessive disorder of lipid metabolism characterized by deficient activity of the lysosomal enzyme, arylsulfatase A (ASA). MLD is a rare orphan disease that occurs in most parts of the world. The estimated overall incidence of the disease in the western world is approximately 1 in 100,000 live births that varies by geographic location. There are no approved therapies for MLD.~This study is a multicenter open-label study designed to evaluate safety and efficacy outcomes of HGT-1110 administered intrathecally in children with MLD who have participated in the dose escalation study, HGT-MLD-070 (NCT01510028), through Week 40 and are receiving study drug every other week (EOW).~Treatment groups will be identical to those in HGT-MLD-070 (NCT01510028), ie, participants assigned to Cohort 1 in Study HGT-MLD-070 (NCT01510028) will continue to receive a dose of 10 milligrams (mg), participants assigned to Cohort 2 in Study HGT-MLD-070 (NCT01510028) will continue to receive a dose of 30 mg, and participants assigned to Cohorts 3 and 4 in Study HGT-MLD-070 (NCT01510028) will continue to receive a dose of 100 mg. Participants in Cohort 4 are to exclusively receive drug product produced with Process B in Study HGT-MLD-070 (NCT01510028) and will continue receiving this drug product in this study. Participants enrolled in this study from Cohorts 1 to 3 in Study HGT-MLD-070 (NCT01510028) were transitioned to Process B after all necessary approvals were obtained. In HGT-MLD-071, all participants in the 10 mg dose cohort who experienced disease progression, as determined by the Investigator, increased to the 30 mg dose after agreement by the Medical Monitor. Based on the interim analysis results from HGT-MLD-070 (NCT01510028 [Cohorts 1-3]), the dose of HGT-1110 will be increased to 100 mg for all participants in HGT-MLD-071 after all necessary approvals were obtained.
The purpose of this study is to collect long-term safety data in participants with metachromatic leukodystrophy (MLD) who are receiving HGT-1110 and have participated in Study HGT-MLD-070 (NCT01510028) through Week 40.