For instance, a fusion of lysosomal enzyme iduronate 2- sulfatase (IDS) with anti- TfR antibody (JR-141) enabled successful delivery of the fusion protein into the CNS of patients with Hunter Syndrome under systemic settings (i.v.)in a phase I/II trial (NCT03128593) which shows promising therapeutic efficacy with no significant safety issue [114]. This evidence concerns the gene IDS and mucopolysaccharidosis type 2.