GAA-KO mice injected with an advanced generation Ad vector began expressing, and more importantly, secreting high P450 inhibitor levels of precursor hGAA from their transduced liver hepatocytes. Since this form of hGAA is likely correctly processed by the mammalian Golgi

apparatus to contain the “motifs”: (i.e.: mannose-6-phosphate residues) required for receptor mediated uptake and lysosomal targeting, liver derived hGAA was taken up by all affected muscle cells in the Ad treated GAA-KO animals. This resulted in both cardiac and skeletal muscle glycogen clearance within 12 days of the gene therapy treatment, and like Inhibitors,research,lifescience,medical ERT, was most effective in cardiac and diaphragm muscles (17). This report was the first to demonstrate the complete systemic correction of a form of muscular dystrophy by a simple intravenous injection technique. This observation Inhibitors,research,lifescience,medical has been subsequently repeated by us and others using Ad or AAV based approaches, as well in alternative species, such as the AMD quail model of GSD-II (18–20). Long term Ad mediated hGAA gene therapy studies showed that hepatically derived hGAA enzyme persisted

in the heart and diaphragm for at least 6 months post injection. However, we also noted that plasma levels of hGAA diminished over time in the vector treated GAA-KO Inhibitors,research,lifescience,medical mice (21). We have subsequently confirmed in numerous publications that the loss of plasma hGAA following intravenous injection of an Ad-hGAA vector was not due to loss of the vector, but rather was due to the onset of anti-hGAA antibodies (11, 22–24). These anti-hGAA antibodies prevent Inhibitors,research,lifescience,medical efficient, high level skeletal or cardiac muscle cell uptake of hepatically expressed hGAA, and limited long term efficacy of the approach, a limitation also noted after ERT treatments of GSD-II patients (4, 25). In our most recent studies, use of an optimized Inhibitors,research,lifescience,medical Adenovirus vector expressing hGAA via a tissue specific promoter in adult, hGAA tolerant GAA-KO mice permitted glycogen correction and muscle strength to be preserved in hGAA tolerant, GAA-KO mice for greater than one year. This result was

primarily Etomidate achieved by avoiding the elicitation of anti-hGAA antibody production in the treated animals (26). To begin to investigate the potential for disease reversibility in older GSD-II mice, we studied their responsiveness to hGAA gene therapy. This became especially relevent, since ERT in older mice had been shown to have significant limitations (27). Upon intravenous Ad-hGAA vector injection, we found that extremely high amounts of hepatically secreted hGAA could be produced, and subsequently taken up by multiple muscle tissues in old (12-17 months) GAA-KO mice. As a result, all muscle groups in the hGAA gene treated mice showed significant glycogen reductions, relative to that of age-matched, but mock-injected old GAA-KO mice.