This is an open-label, non-controlled, parallel, sequential ascending multiple-dose, multicenter study to assess the dose related safety, tolerability, PK and PD of SOBI003 in pediatric MPS IIIA patients. Patients between 1 and 6 years of age who have not received previous treatment for MPS IIIA with an ERT, gene- or stem cell therapy will be eligible to participate in the study. The study is planned to consist of 3 dose cohorts, each comprising 3 patients. Treatment initiations will be staggered within each cohort in order to be able to observe, interpret and treat possible adverse reactions. SOBI003 is administered as weekly i.v. infusions over a period of 24 weeks. Upon completion of the 24-week treatment period with satisfactory tolerability, the patient is offered to receive continued SOBI003 treatment by participation in an extension study.
