Deferoxamine mesylate improves splicing and GAA activity of the common c.-32-13T>G allele in late-onset Pompe disease patient fibroblasts.

Abstract Pompe disease (PD) is an autosomal recessive lysosomal storage disorder due to deficient activity of the acid alpha glucosidase enzyme (GAA). As a consequence of the enzymatic defect, undigested glycogen accumulates within lysosomes. Most patients affected by the late onset (LO) phenotype carry in at least one allele the c.-32-13T>G variant, which leads to exon 2 exclusion-from the pre-mRNA. These patients display a variable and suboptimal response to enzyme replacement therapy. To identify novel therapeutic approaches, we developed a fluorescent GAA exon 2 splicing assay and screened a library of FDA-approved compounds. This led to the identification of several drugs able to restore normal splicing. Among these, we further validated the effects of the iron chelator deferoxamine (Defe) in c.-32-13T>G fibroblasts. Defe treatment resulted in a 2-fold increase of GAA exon 2 inclusion and a 40% increase in enzymatic activity. Preliminary results suggest that this effect is mediated by the regulation of iron availability, at least partially. RNA-seq experiments also showed that Defe might shift the balance of splicing factors levels towards a profile promoting GAA exon 2 inclusion. This work provides the bases for drug repurposing and development of new chemically modified molecules aimed at improving the clinical outcome in LO-PD patients.