Onvansertib and vilazodone inhibit SARS-CoV-2 replication via suppression of METTL3 RNA-m6A enzymatic activity.

The continuous emergence of new SARS-CoV-2 variants limits the effectiveness of current vaccines and monoclonal antibodies, highlighting the urgent need for complementary antiviral strategies. Targeting host proteins that are exploited by the virus represents a promising approach to achieve broad-spectrum inhibition. Given the recently established proviral role of METTL3-dependent RNA m6A modification in SARS-CoV-2 replication, we conducted a structure-based virtual screening to repurpose compounds with acceptable safety profiles. Subsequent biochemical validation identified onvansertib and vilazodone as direct METTL3 binders and potent inhibitors of its methyltransferase activity. Notably, both compounds effectively suppressed the replication of ancestral SARS-CoV-2 and Omicron BA.2 variant in vitro. Mechanistically, each compound potentially enhanced the innate antiviral response of the host and repressed the expression of viral entry-associated host factors during infection; this observation is consistent with the established proviral role of METTL3. In summary, these findings not only substantiate METTL3 as a viable antiviral target but also lay the foundation for further research on the therapeutic potential of onvansertib and vilazodone against COVID-19.