G.P.46

Mutations in RYR1 are the most common cause of congenital myopathies. Despite a growing understanding of the relationship between RYR1 mutations and muscle disease, no therapies currently exist for these disorders. We previously identified N-acetylcysteine (NAC) as a chemical modifier of disease using both a zebrafish model and patient-derived myotubes. This treatment is now being tested in a clinical trial for core myopathies. In an effort to identify additional new potential therapeutic targets for RYR1-related myopathies, we have developed a novel high throughput in vivo drug screening methodology. This methodology utilizes a large scale chemical modifier screen in the unc-68 C. elegans mutant strain which harbors a recessive (loss-of-function) mutation in ryr, followed by target chemical validation in the zebrafish model of RYR1-related myopathy and in patient myotubes using techniques similar to those from our NAC study. To date, we have screened 3120 chemicals in unc-68 worms using a synthetic growth attenuation paradigm. We have identified 46 chemicals of interest that are "positive hits" from our screen. Among these chemicals are several drugs that modify oxidative stress, thus corroborating our previous data obtained with NAC. We also identified several novel targets, which we are further investigating. The most promising positive hits are now being tested/validated in our zebrafish model, where will examine phenotypic parameters including motor function and survival, as well as histopathologic alterations and physiologic properties. We will additionally examine the successful compounds in patient myotubes, with the ultimate goal of identifying the most promising drug targets to bring to the clinic. In all, we will describe the results of our unique and exciting drug discovery pipeline for RYR1-related myopathies.