In vitro and in vivo evaluation of a non-carbohydrate targeting platform for lysosomal proteins

Department of Therapeutic Protein Research, Genzyme Corporation, Framingham, MA 01701, USA.
Journal of Controlled Release (Impact Factor: 7.71). 04/2009; 135(2):113-8. DOI: 10.1016/j.jconrel.2008.12.006
Source: PubMed


Lysosomal storage diseases arise from a genetic loss-of-function defect in enzymes mediating key catabolic steps resulting in accumulation of substrate within the lysosome. Treatment of several of these disorders has been achieved by enzyme replacement therapy (ERT), in which a recombinant version of the defective enzyme is expressed in vitro and administered by infusion. However, in many cases the biodistribution of the administered protein does not match that of the accumulated substrate due to the glycosylation-mediated clearance of the enzymes from circulation, resulting in poor or absent substrate clearance from some tissues. To overcome this limitation, we have evaluated several peptide-based targeting motifs to redirect recombinant human alpha-galactosidase (rhalphaGal) to specific receptors. A reversible thiol-based PEGylation chemistry was developed to achieve multivalent peptide display with lysosomal release. In vitro, cell uptake was peptide dependent and independent of the normal mannose-6-phosphate receptor mediated pathway. Surprisingly, despite increased plasma half-life and decreased liver uptake, none of the peptide conjugates showed significantly altered biodistribution in alphaGal-knockout mice. This suggests that these peptide-based targeting motifs are unlikely to provide substantial therapeutic benefit likely due to the complexity of factors affecting PK and biodistribution.

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    • "New approaches rely on the uptake mechanisms different from the M6P-based using protein-based mechanisms. Recently, a non-carbohydrate targeting platform for lysosomal proteins was evaluated [61]. The authors described that a fusion protein of β-glucuronidase with IGF-II, a high-affinity M6PR ligand, improved the targeting to podocytes in Mucopolysacccharidosis VII, another lysosomal disorder, where the podocyte is the most severely-affected kidney cell-type [62]. "
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