Discovery of Chalcone-Based Hybrid Structures as High Affinity and Site-Specific Inhibitors Against COVID-19; a Study Based on Various Host-Based and Viral Targets
Abstract 3-Chymotrypsin-like protease (3CLpro) and papain-like protease (PLpro) of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) are at the forefront of attention for finding therapeutic agents for the treatment of COVID-19. In addition, proper modulation of host-based antiviral targets (HBATs) has also been highlighted by scientists as a promising approach for the suppression of the SARS-CoV-2. Previous studies indicated that some natural-based chalcones have significant inhibitory effect on the coronavirus enzymes 3CLpro and PLpro as well as modulation of some HBATs. In this study, a computational screening was performed to investigate the affinity of our compound library consisting of 757 chalcone-based structures (CHA-1 to CHA-757) for inhibiting the 3CLpro and PLpro enzymes, and also against twelve selected host-based targets. The twelve selected HBATs were chosen based on their involvement in viral reproduction. Our results indicated that CHA-12 (VUF 4819) is the most potent and a multi-target inhibitor in our chemical library over all viral and host-based targets. Correspondingly, CHA-384 and its congeners containing ureide moieties were found to be potent and selective 3CLpro inhibitors, and benzotriazole moiety in CHA-37 was found to be a main fragment for inhibiting the 3CLpro and PLpro. Surprisingly, our results were fully consistent with recent reports on the site-specific 3CLpro inhibitors. The results also indicate that the ureide and sulfonamide moieties are integral fragments for the optimum 3CLpro inhibition while occupying the S1 and S3 subsites. Finding the multi-target inhibitor CHA-12, previously reported as a LTD4 antagonist for the treatment of inflammatory pulmonary diseases, prompted us to suggest it as a concomitant antiviral agent for relieving respiratory symptoms and suppressing COVID-19 infection.