The generation of an ETV containing the enzyme iduronate 2-sulfatase (IDS) (ETV:IDS), a 61 kDa lysosomal enzyme that is deficient in a group of lysosomal storage diseases (specifically, Mucopolysaccharidosis Type II), demonstrated enhanced delivery to the brain and a reduction in the accumulation of toxic lysosomal lipids and proteins in a pre-clinical model of disease [62]. Here, IDS is linked to lysosomal storage disease.