Antisense oligonucleotide treatment targeting glycogen synthase (GYS1) in a mouse model of Pompe disease

Pompe disease is a progressive myopathy resulting from the deficiency of acid α-glucosidase (GAA). The standard of care is ERT with recombinant human (rh) GAA. ERT works well in alleviating the cardiomyopathy however, many patients continue to have progressive muscle weakness from muscle glycogen accumulation produced by muscle glycogen synthase (GYS1). Previous studies have shown that inhibition of GYS1 reduced lysosomal glycogen. Knockdown of GYS1 mRNA by phosphorodiamidate morpholino oligonucleotide conjugated with a cell penetrating peptide however wasnephrotoxic. Antisense Oligonucleotides (ASO) technology has emerged as a powerful therapeutic alternative for the treatment of genetic disorders by targeting RNA. In order to impart specificity for the muscle variant of GYS1, we propose the use of ASO-mediated gene silencing through the RNaseH1 dependent degradation mechanism. Most recently therapy for spinal muscular atrophy has been successful using ASOs, and our hope is that ASO technology will be successful in Pompe disease. Over 150 ASOs were designed and screened in vitro to identify the most efficacious ASO for testing in wild type mice. The lead from the screen were validated in a dose response study and the top 10 ASOs were screened in vivo. The 2 ASOs (GYS1 ASO#1 and GYS1 ASO#2) showed the best tolerability and efficacy profile leading to knock down of GYS1 mRNA by approximately 50% of control. We have performed a pilot study of the efficacy of two GYS1 ASOs in Pompe mice as monotherapy and have reduced muscle GYS1 mRNA levels versus PBS and a mismatch ASO. ASO#2 resulted in weight loss of the mice. We will present the results of the study of the effect of the GYS1 ASOs on muscle glycogen, histology, GYS1 RNA and muscle function in Pompe mice. These preliminary studies provide proof of principle for a promising adjunct treatment for Pompe disease.