Synthesis, in silico and in vitro studies of novel quinazolinone derivatives as potential SARS-CoV-2 3CLpro inhibitors

A series of new quinazolinone derivatives (5a-l) were designed as 3CL protease inhibitors for SARS-CoV-2 infection. The designed derivatives were efficiently synthesized by S-alkylation/arylation of an intermediate, 6-fluoro-3-(4-fluorophenyl)-2-mercaptoquinazolin-4(3H)-one and their successful synthesis was established by analytical methods, viz. IR, ¹H NMR, & ¹³C NMR spectroscopy. The in silico inhibitory potential against 3CLpro of SARS-CoV-2 were studied by means of docking and dynamics simulations, and compared with the co-crystallized ligand (VR4) of SARS-CoV-2 3CLpro. The compounds interacted strongly within the active catalytic dyad (Cys-His) site, thereby anticipated to obstruct the function of 3CLpro of SARS-CoV-2. Compounds 5b, 5c, 5i, 5j and 5l showed efficient binding with protease 3CLpro with XP Gscore of −7.4, −8.3, −7.8, −7.5 and −8.2 respectively. Furthermore, molecular dynamic simulation study of these compounds (5b, 5c, 5i, 5j and 5 l) showed stable interaction over 50 ns production run. Swiss ADME and pkCSM web tools showed favorable physicochemical and pharmacokinetic properties and fulfilled the criteria for drug-likeness of these selected studied compounds. The toxicity determination of these selected compounds predicted that some compounds were hepatotoxic, but were not AMES toxic. Compounds 5b, 5c, 5i, 5j and 5 l revealed their inhibitory potential against the SARS-CoV-2 3CLpro, and their IC₅₀ values were attained at 1.58, 1.25, 1.97, 0.44 and 2.56 µM, respectively. In addition, these compounds were found to have devoid of any significant cytotoxicity even at a higher concentration of 20 µM against VeroE6 cells. These quinazolinone derivatives showed potent binding and inhibitory potential against SARS-CoV-2 3CLpro and may emerge as compounds that might act as prospective inhibitors.