Drug Repurposing: In Vitro Evaluation of Simeprevir as a Novel Antiviral Drug Against Severe Fever With Thrombocytopenia Syndrome Virus.

Severe Fever with Thrombocytopenia Syndrome Virus (SFTSV), a tick-borne virus with high mortality, currently lacks approved antiviral therapies. In this study, we evaluated the in vitro activity of 19 FDA-approved drugs against a clinical isolate of SFTSV using cell-based assays, and immunofluorescence analysis. Simeprevir, Novobiocin, and Levofloxacin hydrochloride demonstrated significant antiviral activity (EC50: 0.009774, 25.12, and 46.30 μM, respectively) with minimal cytotoxicity. Immunofluorescence analysis revealed a dose-dependent reduction in SFTSV nucleoprotein expression, correlating with decreased viral replication. The remaining 16 drugs exhibited low antiviral efficacy or high cytotoxicity. Although these three small-molecule drugs show promise for SFTSV treatment, further in vivo studies are necessary to confirm their safety and optimize their structures. Our findings highlight the potential of drug repurposing as a strategy for developing effective therapies against emerging viral infections.