Pompe disease is an inherited lysosomal storage disorder that results from a 
deficiency in acid α-glucosidase (GAA) activity due to mutations in the GAA 
gene. Pompe disease is characterized by accumulation of lysosomal glycogen 
primarily in heart and skeletal muscles, which leads to progressive muscle 
weakness. We have shown previously that the small molecule pharmacological 
chaperone AT2220 (1-deoxynojirimycin hydrochloride, duvoglustat hydrochloride) 
binds and stabilizes wild-type as well as multiple mutant forms of GAA, and can 
lead to higher cellular levels of GAA. In this study, we examined the effect of 
AT2220 on mutant GAA, in vitro and in vivo, with a primary focus on the 
endoplasmic reticulum (ER)-retained P545L mutant form of human GAA (P545L GAA). 
AT2220 increased the specific activity of P545L GAA toward both natural 
(glycogen) and artificial substrates in vitro. Incubation with AT2220 also 
increased the ER export, lysosomal delivery, proteolytic processing, and 
stability of P545L GAA. In a new transgenic mouse model of Pompe disease that 
expresses human P545L on a Gaa knockout background (Tg/KO) and is characterized 
by reduced GAA activity and elevated glycogen levels in disease-relevant 
tissues, daily oral administration of AT2220 for 4 weeks resulted in significant 
and dose-dependent increases in mature lysosomal GAA isoforms and GAA activity 
in heart and skeletal muscles. Importantly, oral administration of AT2220 also 
resulted in significant glycogen reduction in disease-relevant tissues. Compared 
to daily administration, less-frequent AT2220 administration, including repeated 
cycles of 4 or 5 days with AT2220 followed by 3 or 2 days without drug, 
respectively, resulted in even greater glycogen reductions. Collectively, these 
data indicate that AT2220 increases the specific activity, trafficking, and 
lysosomal stability of P545L GAA, leads to increased levels of mature GAA in 
lysosomes, and promotes glycogen reduction in situ. As such, AT2220 may warrant 
further evaluation as a treatment for Pompe disease.