Discovery of 3-phenyl-2H-aziridine derivatives as potent irreversible inhibitors of SARS-CoV-2 main protease via enzyme kinetics and microscale thermophoresis.

Severe Acute Respiratory Syndrome Coronavirus 2 main protease (SARS-CoV-2 Mpro) is an ideal drug target due to its critical role in viral genome replication and high conservation among coronaviruses. This study employed a fluorescence resonance energy transfer (FRET)-based s0063reening method to evaluate the inhibitory activity of thirty-one 3-phenyl-2H-aziridine heterocyclic derivatives against Mpro. The mechanism of action for effective inhibitors was investigated using enzymatic inhibition assays, enzyme kinetics, fluorescence quenching, synchronous fluorescence, 3D fluorescence, circular dichroism spectroscopy, microscale thermophoresis, molecular docking, and molecular dynamics simulations. Results showed that 3-phenyl-2H-aziridine heterocyclic derivatives exhibit significant potential to inhibit SARS-CoV-2 Mpro. The most potent compound, 3ab (methyl 3-phenyl-2-selenocyano-2H-aziridine-2-carboxylate), showed an IC50 value of 0.41 ± 0.03 μM, acting as a covalent irreversible inhibitor, by forming a covalent bond between the -CN group and the critical amino acid residue Cys145 in Mpro, with a dissociation constant (Kd) of 247.37 ± 53.73 nM. This work advances understanding of Mpro inhibitor mechanisms and provides novel insights for Mpro inhibitor development. The identified inhibitors represent promising lead compounds for antiviral drug discovery.