In vivo efficacy of AAV9-mediated gene transfer was evaluated following a single intravenous administration of AAV9.CAG.BiP.vIGF2.hGAAco.rBG.KanR (systemic; SYS) vector (Amicus proprietary) into young (3–3.5 months of age) or old (8–9 months of age) Gaa-KO mice (referred to as KO), a model of Pompe disease (29). This evidence concerns the gene GAA and Glycogen storage disease due to acid maltase deficiency.