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 mu M, respectively. In addition, these compounds were found to have devoid of any significant cytotoxicity even at a higher concentration of 20 mu M 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.