Glycoengineered Acid α-Glucosidase With Improved Efficacy at Correcting the Metabolic Aberrations and Motor Function Deficits in a Mouse Model of Pompe Disease

Abstract

Improving the delivery of therapeutics to disease-affected tissues can increase their efficacy and safety. Here, we show that chemical conjugation of a synthetic oligosaccharide harboring mannose 6-phosphate (M6P) residues onto recombinant human acid alpha-glucosidase (rhGAA) via oxime chemistry significantly improved its affinity for the cation-independent mannose 6-phosphate receptor (CI-MPR) and subsequent uptake by muscle cells. Administration of the carbohydrate-remodeled enzyme (oxime-neo-rhGAA) into Pompe mice resulted in an approximately fivefold higher clearance of lysosomal glycogen in muscles when compared to the unmodified counterpart. Importantly, treatment of immunotolerized Pompe mice with oxime-neo-rhGAA translated to greater improvements in muscle function and strength. Treating older, symptomatic Pompe mice also reduced tissue glycogen levels but provided only modest improvements in motor function. Examination of the muscle pathology suggested that the poor response in the older animals might have been due to a reduced regenerative capacity of the skeletal muscles. These findings lend support to early therapeutic intervention with a targeted enzyme as important considerations in the management of Pompe disease.

Efficacy of Enzyme and Substrate Reduction Therapy with a Novel Antagonist of Glucosylceramide Synthase for Fabry Disease

“…For the enzyme alone and combination therapy studies, Fabry mice were first immunotolerized to the recombinant human enzyme by treating the animals with a recombinant AAV vector encoding an inactive, but stable mutant form of α-Gal A (point mutation in amino acid 170). We and others have previously shown that AAVmediated hepatic-restricted expression of proteins resulted in the induction of immune tolerance to the expressed protein (22,(28)(29)(30)(31)(32). Administration of rh α-Gal A into AAV2/8 α-galD170Mut-treated Fabry mice did not elicit antibodies to the enzyme (data not shown).…”

Synergistic Efficacy from Gene Therapy with Coreceptor Blockade and a β2-Agonist in Murine Pompe Disease

“…Receptor-mediated uptake of GAA, like other lysosomal enzymes, occurs mainly through a receptor-mediated endocytosis mechanism using CI-MPR, 22,23 and clenbuterol treatment during ERT or gene therapy increased CI-MPR expression in the skeletal muscle of GAA-KO mice with positive therapeutic effects. 11,13 In this study, clenbuterol significantly increased the expression of CI-MPR in skeletal muscle (Fig.…”

New insights into therapeutic options for Pompe disease

“…A comparable reduction of glycogen level was obtained in heart and diaphragm using a 8-fold lower dose, and in skeletal muscle using a 4-fold lower dose. The oxime-neo-rhGAA variant displayed higher stability, increased affinity for the CI-MPR, and approximately 5-fold higher efficacy at clearing glycogen with only one-fifth the dose of unmodified enzyme (67). Interestingly, the oxime-neorhGAA generated a more rapid clearance of glycogen thereby reducing or minimizing muscle damage.…”

“…This hypermannose-6-phosphorylated enzyme (HP-GAA) was no more effective at clearing glycogen from Pompe mice than the unmodified enzyme, due to a sequestration by mannose receptors on endothelial cells and macrophages (66). Synthetic oligosaccharides carrying mannose-6-phosphate residues were then conjugated to the rhGAA using carbonyl/hydrazide (neorhGAA) or carbonyl/oxime-mediated chemistry (oxime-neorhGAA) (66,67). The resulting neo-rhGAA enzyme displayed near normal specific activity, increased affinity for the CI-MPR, and was internalized 20-fold more efficiently than the naïve enzyme into myoblasts in vitro.…”