Drug Repurposing for Covid-19: Discovery of Potential Small-Molecule Inhibitors of Spike Protein-ACE2 Receptor Interaction Through Virtual Screening and Consensus Scoring

Objective There is an increased interest in drug repurposing against Covid-19 (SARS-CoV-2) as its spread has significantly outpaced development of effective therapeutics. Our aim is to identify approved drugs that can inhibit the interaction of SARS-CoV-2 spike protein with human angiotensin-converting enzyme 2 (ACE2) that is critical for coronavirus infection. Methods The published crystal structure of SARS-CoV-2 spike protein-ACE2 receptor interaction was first analyzed for druggable binding pockets. The binding interface was then probed by an integrated virtual screening protocol executed by a high-performance computer cluster, involving docking and consensus scoring using various machine-learning, empirical and knowledge-based scoring functions. The consensus-ranked lists of screened drugs were generated via ‘rank-by-rank’ and ‘rank-by-number’ schemes. Findings Although spike protein and ACE2 lacked druggable pockets in their unbound forms, they presented a well-defined pocket when bound together. Accordingly, we identified many drugs with high binding potential against this protein-protein interaction pocket. Importantly, several antivirals against two major (+)ssRNA viruses (HCV and HIV) constituted major group of our top hits, of which Atazanavir, Grazoprevir, Saquinavir, Simeprevir, Telaprevir and Tipranavir could be of most importance for immediate experimental/clinical investigations. Additional notable hits included many anti-inflammatory/antioxidant, antibiotic/antifungal, and other relevant compounds with proven activity against respiratory diseases, further emphasizing robustness of our current study. Notably, we also discovered Maraviroc, the only FDA-approved drug capable of targeting virus-host interaction and blocking HIV entry. Conclusion Our newly identified compounds warrant further experimental investigation against SARS-CoV-2 spike-ACE2 interaction, which if proven effective may present much-needed immediate clinical potential against Covid-19

Sampangine Inhibits Heme Biosynthesis in both Yeast and Human ▿ †

The azaoxoaporphine alkaloid sampangine exhibits strong antiproliferation activity in various organisms. Previous studies suggested that it somehow affects heme metabolism and stimulates production of reactive oxygen species (ROS). In this study, we show that inhibition of heme biosynthesis is the primary mechanism of action by sampangine and that increases in the levels of reactive oxygen species are secondary to heme deficiency. We directly demonstrate that sampangine inhibits heme synthesis in the yeast Saccharomyces cerevisiae. It also causes accumulation of uroporphyrinogen and its decarboxylated derivatives, intermediate products of the heme biosynthesis pathway. Our results also suggest that sampangine likely works through an unusual mechanism—by hyperactivating uroporhyrinogen III synthase—to inhibit heme biosynthesis. We also show that the inhibitory effect of sampangine on heme synthesis is conserved in human cells. This study also reveals a surprising essential role for the interaction between the mitochondrial ATP synthase and the electron transport chain