Discovery of a novel benzimidazole conjugated quinazolinone derivative as a promising SARS-CoV-2 3CL protease inhibitor.

This report presents the design and synthesis of quinazolinone-based derivatives as promising SARS-CoV-2 3CL protease inhibitors. Two novel series, namely, febrifugine analogues 4a-i and quinazolinone conjugated benzimidazoles 9a-c, were successfully synthesized starting from isatoic anhydride. The synthesized quinazolinone derivatives were evaluated for their cytotoxicity against cancer cell lines and SARS-CoV-2 3CL inhibitory activity. The results showed that the synthesized compounds did not have significant toxicity for the non-cancer HEK293 cell line and MCF-7, MDA-MB-231, HEPG2 and HEPG2.2.15 cancer cell lines. Notably, compound 9b exhibited anti-3CL enzymatic activity in a dose-dependent manner, with the calculated IC value of 10.73 ± 1.17 μM. Docking results highlighted the interaction between 9b and 3CL protease through hydrogen bonding with key amino acids, including His41, Met49, Cys145, Met165, Arg188, His164, and Glu166, at the active site of the protease. Pharmacokinetic studies and ADME analyses provide valuable insights into the potential of compound 9b as a drug candidate. These findings support the new scaffold as a candidate for 3CL inhibition and advanced anti-coronavirus drug research.