Delivery of an enzyme-IGFII fusion protein to the mouse brain is therapeutic for mucopolysaccharidosis type IIIB

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 111; no. 41; pp. 14870 - 14875
• Main Authors: Kan, Shih-hsin, Aoyagi-Scharber, Mika, Le, Steven Q., Vincelette, Jon, Ohmi, Kazuhiro, Bullens, Sherry, Wendt, Daniel J., Christiansen, Terri M., Tiger, Pascale M. N., Brown, Julian R., Lawrence, Roger, Yip, Bryan K., Holtzinger, John, Bagri, Anil, Crippen-Harmon, Danielle, Vondrak, Kristen N., Chen, Zhi, Hague, Chuck M., Woloszynek, Josh C., Cheung, Diana S., Webster, Katherine A., Adintori, Evan G., Lo, Melanie J., Wong, Wesley, Fitzpatrick, Paul A., LeBowitz, Jonathan H., Crawford, Brett E., Bunting, Stuart, Dickson, Patricia I., Neufeld, Elizabeth F.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 14-10-2014; National Acad Sciences
• Subjects: Acetylglucosaminidase - therapeutic use; Animals; beta-N-Acetylhexosaminidases - metabolism; Biological Sciences; Biomarkers - metabolism; Brain; Brain - metabolism; Brain - pathology; Cells, Cultured; CHO Cells; Cricetinae; Cricetulus; Dementia; Drug Delivery Systems; Endocytosis; Enzyme replacement therapy; Enzymes; Fibroblasts - metabolism; Fibroblasts - pathology; Heparitin Sulfate - metabolism; Humans; Injections, Intraventricular; Insulin-Like Growth Factor II - therapeutic use; Learning disabilities; Liver; Liver - metabolism; Lysosomal Membrane Proteins - metabolism; Mice; Mucopolysaccharidoses; Mucopolysaccharidosis III - drug therapy; Mucopolysaccharidosis III - pathology; Mutation; Neurons; Neurons - metabolism; Neurons - pathology; Protein Binding; Proteins; Receptors; Recombinant Fusion Proteins - administration & dosage; Recombinant Fusion Proteins - therapeutic use; Sulfates; Vehicles
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1416660111

Significance Mucopolysaccharidosis type IIIB (MPS IIIB) is a devastating and currently untreatable disease affecting mainly the brain. The cause is lack of the lysosomal enzyme, α– N -acetylglucosaminidase (NAGLU), and storage of heparan sulfate. Using a mouse model of MPS IIIB, we administered a modified NAGLU by injection into the left ventricle of the brain, bypassing the blood–brain barrier. The modification consisted of a fragment of IGFII, which allows receptor-mediated uptake and delivery to lysosomes. The modified enzyme was taken up avidly by cells in both brain and liver, where it reduced pathological accumulation of heparan sulfate and other metabolites to normal or near-normal levels. The results suggest the possibility of treatment for MPS IIIB.
Mucopolysaccharidosis type IIIB (MPS IIIB, Sanfilippo syndrome type B) is a lysosomal storage disease characterized by profound intellectual disability, dementia, and a lifespan of about two decades. The cause is mutation in the gene encoding α– N -acetylglucosaminidase (NAGLU), deficiency of NAGLU, and accumulation of heparan sulfate. Impediments to enzyme replacement therapy are the absence of mannose 6-phosphate on recombinant human NAGLU and the blood–brain barrier. To overcome the first impediment, a fusion protein of recombinant NAGLU and a fragment of insulin-like growth factor II (IGFII) was prepared for endocytosis by the mannose 6-phosphate/IGFII receptor. To bypass the blood–brain barrier, the fusion protein (“enzyme”) in artificial cerebrospinal fluid (“vehicle”) was administered intracerebroventricularly to the brain of adult MPS IIIB mice, four times over 2 wk. The brains were analyzed 1–28 d later and compared with brains of MPS IIIB mice that received vehicle alone or control (heterozygous) mice that received vehicle. There was marked uptake of the administered enzyme in many parts of the brain, where it persisted with a half-life of approximately 10 d. Heparan sulfate, and especially disease-specific heparan sulfate, was reduced to control level. A number of secondary accumulations in neurons [β-hexosaminidase, LAMP1(lysosome-associated membrane protein 1), SCMAS (subunit c of mitochondrial ATP synthase), glypican 5, β-amyloid, P-tau] were reduced almost to control level. CD68, a microglial protein, was reduced halfway. A large amount of enzyme also appeared in liver cells, where it reduced heparan sulfate and β-hexosaminidase accumulation to control levels. These results suggest the feasibility of enzyme replacement therapy for MPS IIIB.