In vitro antiviral effects of an mTORC1 inhibitor targeting the rapamycin-binding protein complex.

The persistent threat of mutable viral pathogens highlights the need for broad-spectrum antiviral drugs that target stable host factors to provide a high genetic barrier to resistance. The mammalian target of rapamycin complex 1 (mTORC1) serves as a central metabolic bottleneck in cellular metabolism. It is commonly co-opted by both DNA and RNA viruses to enhance the translation of their structural proteins. Here, we evaluated WRX606, a novel mTORC1 inhibitor, as a broad-spectrum antiviral candidate against representative RNA viruses. WRX606 demonstrated low cytotoxicity across multiple host cell lines, including MRC-5, HeLa, COS-1, and MDCK cells, with CC50 values consistently exceeding 40 μM. Antiviral assays confirmed that WRX606 effectively inhibits the replication of both Influenza A virus and human coronavirus 229E. This compound exhibited exceptional potency against Influenza A virus with a half-maximal inhibitory concentration (IC50) of 13.0 nM (determined by water-soluble tetrazolium salt-8 assay) and 32.0 nM (determined by cytopathic effect observation), yielding a Selectivity Index (SI) of 6376.9 and 2590.6, respectively. Mechanistic investigations, including RT-qPCR and western blotting, revealed that WRX606 does not interfere with viral adsorption or intracellular genome replication. Rather, it likely exerts its antiviral effect by interfering with the intracellular translation or stability of viral structural proteins such as hemagglutinin and neuraminidase, leading to a significant reduction in the release of progeny virions. Time-of-addition assays further confirmed that WRX606 affects broad stages of the viral life cycle leading up to release. By targeting mTORC1, WRX606 offers a potential host-directed strategy for addressing viral infections.