For example, systemic ERT has been successful in treating some types of MPS with extensive somatic involvement (MPS I,4 II,5 IVA,6 and VI7), but this approach is not feasible for MPS IIIB because of the inability of the NAGLU enzyme to cross the blood-brain barrier and alleviate the neurological deficits associated with MPS IIIB. This evidence concerns the gene NAGLU and mucopolysaccharidosis type 3B.