These data are also in concordance with observations in the MPS II mouse model where Ids KO mice have an elevation in CSF lysosomal lipid content [31], and where a brain penetrant form of Idursulfase (ETV:IDS) is able to correct these lysosomal changes in as early as 4 weeks of dosing at clinically relevant doses. The gene discussed is IDS; the disease is mucopolysaccharidosis type 2.