A Study to Assess the Safety, Tolerability, and Efficacy of Long-term SOBI003 Treatment in Pediatric MPS IIIA Patients

MPS IIIA, also known as Sanfilippo A, is an inherited lysosomal storage disease (LSD). MPS IIIA is caused by a deficiency in sulfamidase, one of the enzymes involved in the lysosomal degradation of the glycosaminoglycan (GAG) heparan sulfate (HS). The natural course of MPS IIIA is characterized by devastating neurodegeneration with initially mild somatic involvement. The aim of the present study is to assess the safety, tolerability and efficacy of long-term SOBI003 treatment. SOBI003 is a chemically modified recombinant human (rh) Sulfamidase developed as an enzyme replacement therapy (ERT).

This is an open, single-arm, multicenter extension study to assess the safety, tolerability and efficacy of long-term SOBI003 treatment in pediatric MPS IIIA patients. The study is an extension of the First in Human (FIH) SOBI003-001 study, allowing continuous treatment of SOBI003 for up to 2 years. Study patients who complete Week 24 of the FIH study (SOBI003-001) will be invited to continue to Week 25 in the extension study. When entering the extension study, these patients will receive the highest dose that has been declared safe in the ongoing FIH study (SOBI003-001). Upon completion of the FIH study, an analysis aimed at selecting the dose for forthcoming studies will take place. Once the dose has been selected, this dose will be applied to all patients enrolled in the extension study. The total duration of the extension study for an individual patient is 80 weeks, resulting in a total of 104 weeks (2 years) of SOBI003 treatment.