ABSTRACT
Drug repurposing has the advantage of shortening regulatory preclinical development steps. Here, we screened a library of drug compounds, already registered in one or several geographical areas, to identify those exhibiting antiviral activity against SARS-CoV-2 with relevant potency. Of the 1,942 compounds tested, 21 exhibited a substantial antiviral activity in Vero-81 cells. Among them, clofoctol, an antibacterial drug used for the treatment of bacterial respiratory tract infections, was further investigated due to its favorable safety profile and pharmacokinetic properties. Notably, the peak concentration of clofoctol that can be achieved in human lungs is more than 20 times higher than its IC50 measured against SARS-CoV-2 in human pulmonary cells. This compound inhibits SARS-CoV-2 at a post-entry step. Lastly, therapeutic treatment of human ACE2 receptor transgenic mice decreased viral load, reduced inflammatory gene expression and lowered pulmonary pathology. Altogether, these data strongly support clofoctol as a therapeutic candidate for the treatment of COVID-19 patients.
Subject(s)
COVID-19 Drug Treatment , SARS-CoV-2 , Animals , Antiviral Agents/pharmacology , Chlorobenzenes , Chlorocebus aethiops , Cresols , Humans , Lung , Mice , Vero CellsABSTRACT
The COVID-19 pandemic has presented itself as one of the most critical public health challenges of the century, with SARS-CoV-2 being the third member of the Coronaviridae family to cause a fatal disease in humans. There is currently only one antiviral compound, remdesivir, that can be used for the treatment of COVID-19. To identify additional potential therapeutics, we investigated the enzymatic proteins encoded in the SARS-CoV-2 genome. In this study, we focussed on the viral RNA cap methyltransferases, which play key roles in enabling viral protein translation and facilitating viral escape from the immune system. We expressed and purified both the guanine-N7 methyltransferase nsp14, and the nsp16 2'-O-methyltransferase with its activating cofactor, nsp10. We performed an in vitro high-throughput screen for inhibitors of nsp14 using a custom compound library of over 5000 pharmaceutical compounds that have previously been characterised in either clinical or basic research. We identified four compounds as potential inhibitors of nsp14, all of which also showed antiviral capacity in a cell-based model of SARS-CoV-2 infection. Three of the four compounds also exhibited synergistic effects on viral replication with remdesivir.
Subject(s)
Antiviral Agents/pharmacology , Drug Evaluation, Preclinical , Exoribonucleases/antagonists & inhibitors , Methyltransferases/antagonists & inhibitors , RNA Caps/metabolism , SARS-CoV-2/enzymology , Small Molecule Libraries/pharmacology , Viral Nonstructural Proteins/antagonists & inhibitors , Adenosine Monophosphate/analogs & derivatives , Adenosine Monophosphate/pharmacology , Alanine/analogs & derivatives , Alanine/pharmacology , Animals , Antiviral Agents/chemistry , Chlorobenzenes/pharmacology , Chlorocebus aethiops , Enzyme Assays , Exoribonucleases/genetics , Exoribonucleases/isolation & purification , Exoribonucleases/metabolism , Fluorescence Resonance Energy Transfer , High-Throughput Screening Assays , Indazoles/pharmacology , Indenes/pharmacology , Indoles/pharmacology , Methyltransferases/genetics , Methyltransferases/isolation & purification , Methyltransferases/metabolism , Nitriles/pharmacology , Phenothiazines/pharmacology , Purines/pharmacology , Reproducibility of Results , SARS-CoV-2/drug effects , Small Molecule Libraries/chemistry , Substrate Specificity , Trifluperidol/pharmacology , Vero Cells , Viral Nonstructural Proteins/genetics , Viral Nonstructural Proteins/isolation & purification , Viral Nonstructural Proteins/metabolism , Viral Regulatory and Accessory Proteins/genetics , Viral Regulatory and Accessory Proteins/isolation & purification , Viral Regulatory and Accessory Proteins/metabolismABSTRACT
The synthetic antibacterial drug clofoctol (CFT) has long been used to treat respiratory tract infections in Europe. In recent years, the drug was found to target two biologically important proteins, the Cdc7/Dbf4 protein kinase complex and the mRNA-binding protein cold shock domain containing E1 (CSDE1), also known as upstream-of-N-Ras protein (UNR). These interactions are at the origin of the antitumor activity of CFT, recently evidenced in prostate cancer and neuroglioma. Drug-protein binding models provide a structural basis to guide the design of more potent anticancer compounds. A renewed interest in CFT can be anticipated for the treatment of cancers, and possibly Coronavirus 2019 (COVID-19).