Despite the clinical benefits of ERT, the efficacy of rhGAA may be limited by insufficient targeting and uptake into key diseaserelevant tissues, as well as poor tolerability due to immunogenic and anaphylactic reactions to the exogenous enzyme. In addition, ERT does not address the neurological manifestations associated with Pompe disease since rhGAA does not cross the blood-brain barrier. Hence, a clear unmet medical need still exists for many Pompe patients. GAA is synthesized as a 110 kDa immature glycoprotein precursor in the endoplasmic reticulum, and undergoes a series of proteolytic and N-glycan processing events to yield the 95 kDa intermediate and the 76 and 70 kDa mature isoforms. Processing into the intermediate and mature Adenine hydrochloride species occurs in late endosomes and lysosomes, respectively, with the final mature isoforms showing significantly increased affinity and activity towards glycogen compared to the precursor forms. Hence, increasing the amount of mature, active GAA in lysosomes is an important step toward the goal of increasing glycogen hydrolysis and reducing substrate accumulation in this disease. Small molecule pharmacological chaperones have been proposed as a potential alternative to ERT for the treatment of Pompe disease. PCs are thought to selectively bind and stabilize enzymes during synthesis in the ER, facilitating proper protein folding and trafficking, and increasing lysosomal levels and activity. We and others have shown that the iminosugar 1-deoxynojirimycin hydrochloride can selectively bind and stabilize multiple mutant forms of GAA, thereby facilitating proper protein folding and increasing the cellular levels of mature GAA, indicative of improved trafficking to lysosomes. Similarly, N-butyl-DNJ was also shown to increase the cellular levels of mature mutant GAA. However, these earlier studies did not delineate the points during GAA synthesis and maturation at which these PCs act, nor did they demonstrate increases in lysosomal GAA activity as SL 0101-1 measured by reduced glycogen levels in situ.