Pompe disease (PD) is a progressive myopathy caused by the deficiency of acid alphaglucosidase (GAA). Enzyme replacement therapy (ERT) with recombinant human GAA alleviates the cardiomyopathy; however, many patients continue to have progressive muscle weakness from glycogen accumulation. Studies in 1- and 3-month-old mice demonstrated effective knockdown of GYS1 mRNA by antisense oligonucleotide (ASO) therapy and subsequent glycogen clearance in muscle, but partial clearance in the heart. We reasoned that earlier treatment may be more effective in clearing muscle and heart glycogen.
Post-natal day 4 (P4) Gaa-/- mice were treated with ASO at dose of 5, 12.5 or 25 mg/kg every week for 16 weeks. Motor testing was done every month, after which the mice were euthanized. Quadriceps, heart and diaphragm samples were tested for Gys1 knocking down, glycogen content, autophagy markers and histopathological manifestations of PD. Another cohort of P4 mice started treatment with ASO at 25 mg/kg, ERT was added at 2 months and both treatments continued until 6 months.
Results: Motor tests showed best performance at 25 mg/kg. Complete downregulation of Gys1 protein and mRNA expression were reached at 12.5 and 25 mg/kg, and reduction of LC3-II and LAMP1 were demonstrated at 25 mg/kg in quadriceps and diaphragm. PAS staining and biochemical assay showed reduction of glycogen content, and histopathology analysis showed a reduction of vacuolation in quadriceps at 12.5 and 25 mg/kg. There were no toxicity signs during treatment. Mice treated with a combination of ERT and ASO at 25 mg/kg for 6 months showed best improvement in strength compared to monotreatment with ERT or ASO.
These results provide proof of principle that ASOs inhibiting GYS1 can reduce glycogen in PD in neonatal Gaa-/- mice. ASO therapy may be considered as an option in the treatment of patients with PD, as an adjunct treatment with ERT.