Sodium Valproate for GSDV

McArdle disease is a metabolic myopathy characterised by the absence of glycogen phosphorylase in skeletal muscle. Sodium Valproate is part of a group of drugs known as histone deacetylase inhibitors, which have a direct effect on chromatin. Recently a drug trial in an animal model of McArdle disease showed that sodium valproate stimulated the expression of a different isoform of the missing enzyme in skeletal muscle. A safety and feasibility study of sodium valproate in people with McArdle disease has been carried out in London (UK) and Copenhagen (DK) since January 2015. Participants will receive 20mg/Kg/day of sodium valproate for 6 months. The primary outcome measure is exercise performance assessed by cycle ergometry. Pre and post-treatment skeletal muscle biopsies will be performed to assess for glycogen phosphorylase. Together with blood analyses for safety. Additional functional exercise tests will be performed.