Repurposing Oseltamivir Against C<b><u>A</u></b>G Repeat Mediated Toxicity in Huntington’s Disease and Spinocerebellar Ataxia Using Cellular and <i>Drosophila</i> Model

Huntington's disease (HD) and Spinocerebellar Ataxia (SCA) are debilitating neurological disorders triggered by the expansion of C<b>A</b>G sequences within the specific genes (HTT and ATXN, respectively). These are characterized as poly glutamine (polyQ) disorders, which are marked by widespread neurodegeneration and metabolic irregularities across systemic, cellular, and intracellular levels. This study aimed to identify small molecules that specifically interact with and target the toxic C<b>A</b>G repeat RNA. Here, we investigated the neuroprotective effects of Oseltamivir, an antiviral drug, against the HD and SCA-causing C<b>A</b>G repeats, through biophysical, cellular, and <i>Drosophila</i> model-based studies. Using a multidimensional approach encompassing biophysical techniques, cellular assays, and a <i>Drosophila</i> model, we explored Oseltamivir's interaction with toxic C<b>A</b>G repeat RNA. Our comprehensive analyses, including circular dichroism (CD), isothermal titration calorimetry (ITC), electrophoretic mobility shift assay (EMSA), and nuclear magnetic resonance (NMR) spectroscopy, demonstrated Oseltamivir's specific binding affinity for AA mismatches and its potential to mitigate the toxicity associated with polyQ aggregation. Moreover, the identified U.S. FDA-approved drug effectively mitigated polyQ-induced toxicity in both HD cells and the <i>Drosophila</i> model of the disease. The results obtained from this drug repurposing approach are indicative of the neuro-shielding role of Oseltamivir in HD and several SCAs, paving the way for its translation into clinical practice to benefit patients afflicted with these devastating diseases.