Poster Presentation 40th Annual Lorne Genome Conference 2019

Late onset Pompe disease: rescue of acid alpha-glucosidase expression by splice modification (#113)

May T Aung-Htut 1 2 , Kristin A West 1 2 , Russell Johnsen 1 , Frederick J Schnell 3 , Sue Fletcher 1 2 , Steve Wilton 1 2
  1. Murdoch University, Murdoch, WA, Australia
  2. Western Australia Neuroscience Research Institute, Perth, Western Australia, Australia
  3. Sarepta Therapeutics , Cambridge MA, USA

Recently, there has been an increase in the number of approvals for nucleic acid therapies to treat various diseases. Exondys 51, a splice modulating morpholino oligomer designed and evaluated in our laboratory, has been granted accelerated approval for the treatment of a subset of Duchenne muscular dystrophy patients in the United States. We are extending splice intervention therapy to Pompe disease, also known as glycogen storage disease II (GSDII), caused by a deficiency of the enzyme acid alpha-glucosidase.

GSDII is an autosomal recessive disorder, and affected individuals are unable to degrade glycogen stored within lysosomes, leading to an accumulation of glycogen in tissues, mainly muscles. Clinically, GSDII may range from severe/infantile to a milder late-onset adult form. The most common GAA mutation associated with the latter is IVS1-13T>G, found in over two-thirds of the adult-onset GSDII patients. The consequence of this mutation is the production of mostly non-functional GAA isoforms due to aberrant exon 2 splicing during pre-RNA processing. Current enzyme replacement therapy for Pompe disease has drawbacks, including immune reaction and poor delivery to target tissues. Therefore, effective alternative therapies are needed.

We sought to enhance GAA exon 2 selection during pre-mRNA processing, using splice-switching antisense oligomers (AO) directed at splice silencer elements to promote recognition and retention of exon 2 in the mature GAA mRNA, thereby restoring enzyme function. Selection of AO sequences that promote GAA exon 2 inclusion in the mature transcript was carried out in fibroblasts derived from five adult Pompe patients. Phosphorodiamidate morpholino oligomers (PMOs) were transfected into patient cells and RT-PCR and acid-alpha-glucosidase enzyme assays were performed. Several PMO sequences showed an increase in the full-length amplicon, GAA expression, and activity. These data show that PMO mediated modification of GAA transcript could have therapeutic potential for a large portion of adult-onset Pompe patients.