Inclusion Criteria: * Documented MPS IIIA diagnosis based on genotyping confirming the SGSH gene mutations * Cognitive DQ score on BSID-III: 50% and above Exclusion Criteria: * Homozygous for the S298P mutation or non-classical severe form of MPS IIIA, based on investigator's judgement. * Participation in another gene or cell therapy clinical trial. * Past use of SGSH enzyme replacement therapy for a period exceeding 3 months. A washout period of at least 2 months is required prior to screening. * Current participation in a clinical trial of another investigational medicinal product. * History of bleeding disorder or current use of medications that, in the opinion of the investigator, place them at risk of bleeding following surgery. * Any condition that would contraindicate treatment with immunosuppressants such as tacrolimus, mycophenolate mofetil or steroids.