Hydroxyethylamine & phthalimide analogs restoring defects due to GNE dysfunction: rare disease therapeutic significance

Rare diseases refer to a group of neglected diseases with low prevalence that face challenges in diagnostics as well as therapeutics due to phenotypic heterogeneity and ineffective clinical trials. In this study, we evaluated two novel analogs of hydroxyethylamine & phthalimide (LTC-181 and LTC-1717) for their potential effect on the epimerase activity of mutant GNE proteins associated with GNE myopathy. GNE gene encodes a key bifunctional sialic acid biosynthetic enzyme, UDP-N-acetyl Glucosamine 2-epimerase/N-acetyl Mannosamine Kinase; GNE). The compounds have significantly increased the epimerase activity of r-F307C-GNE and r-A555V-GNE mutant proteins in vitro. Reduced GNE epimerase activity and sialic acid content in muscle cell-based model for GNE function (SKM-GNEHz) was increased by 2-fold after addition of these compounds. The proteomic study showed that the compounds affected cytoskeletal organization, autophagy and muscle atrophy. Also, treatment with analogs enhanced the cell viability of SKM-GNEHz cells with increased F-actin polymerization and cell migration, thereby, restoring GNE deficient function. Additionally, effect of these compounds was observed with enhanced autophagy and reduced muscle atrophy function in GNE deficient muscle cell. Docking and interaction studies showed that LTC-1717 stabilize GNE better than LTC-181, indicating better therapeutic potential. Overall, this study indicates that HEA-phthalimide analog could be promising leads for treating GNE myopathy.