The rapid emergence of COVID-19 pandemics has posed humans particularly vulnerable to the novel SARS-CoV-2 virus. Since de novo drug discovery is both expensive and time-consuming, drug repurposing approaches are believed to be of particular help. The SARS-CoV-2 spike (S) protein is known to attach human angiotensin-converting enzyme-2 (hACE2) through its receptor-binding domain (RBD). We screened 1930 FDA-approved ligands for the selection of optimal ones blocking this interaction. Virtual screening predicted top 25 ligands docking to any of the reported binding sites. After exclusion of those ligands which were unsuitable for systemic use, the remaining 69 RBD-ligand complexes were screened based on the masking capacity of the amino acid residues engaged in RBD-hACE2 interaction, excluding 47 RBD-ligand complexes. A short molecular dynamics (MD) simulation analysis identified 11 globally stable complexes with the lowest RMSD (root-mean-square deviation). Next, a moderately long MD analysis revealed those six RBD-ligand complexes with the lowest RMSD variation, as a measure of global stability. Finally, a long MD analysis revealed two select candidate ligands, including ritonavir and naloxegol, highly stabilizing those key residues engaged in RBD-hACE2 interaction. A similar MD analysis of a few antiviral drugs which are under clinical trials or approved for COVID-19 treatment showed them inferior to both select ligands in terms of stabilizing the RBD globally and locally at binding sites. Because of the crucial role of the S protein in virus virulence, our results highly propose ritonavir and naloxegol as the potentially helpful therapeutics against COVID-19, mandating appropriate clinical trials.Communicated by Ramaswamy H. Sarma.
Keywords: ACE2; COVID-19; naloxegol; ritonavir; spike protein.