Brain Targeting in MPS-IIIA.

Mucopolysaccharidosis type IIIA (MPS-IIIA) is a childhood metabolic neuropathology caused by the inherited deficiency of the lysosomal enzyme sulfamidase and is characterized by the accumulation of undegraded glycosaminoglycans in the lysosomes of cells and tissues of affected patients. MPS-IIIA represents one of the most common forms of lysosomal storage disorders (LSDs) and to date there is no cure. Since neurodegeneration is the most relevant pathological feature in MPS-IIIA patients, the treatment of the central nervous system (CNS) lesions represents the goal of any effective therapy for this devastating disorder. During the last years many advances have been made in developing and testing new therapies for brain involvement in MPS-IIIA. These studies have been possible because of the availability of mouse and dog models that recapitulate the MPS-IIIA neuropathological features. Some of these approaches are based on direct CNS administration routes through which the therapeutic molecules access the CNS via the parenchyma (intracerebral injections) or via the cerebrospinal fluid (intraventricular/intrathecal injections). These approaches are highly invasive and poorly suited for clinical use. Minimally invasive approaches are based on systemic injections into the blood stream of therapeutics capable of crossing the blood-brain barrier (BBB). This review will present the background of the clinic and pathology aspects of MPS-IIIA and will describe the current MPS-IIIA preclinical and clinical studies focusing on how a systemic therapeutic strategy based on crossing the BBB has been successfully used to treat CNS pathology and behavioral abnormalities in a mouse model of MPS-IIIA. Future clinical applications of this approach to MPS-IIIA patients will be also discussed together with the possibility of using similar strategies in other LSDs with neurological involvement.