FDA-Approved Drugs with Potent In Vitro Antiviral Activity against Severe Acute Respiratory Syndrome Coronavirus 2

Abstract

(1) Background: Drug repositioning is an unconventional drug discovery approach to explore new therapeutic benefits of existing drugs. Currently, it emerges as a rapid avenue to alleviate the COVID-19 pandemic disease. (2) Methods: Herein, we tested the antiviral activity of anti-microbial and anti-inflammatory Food and Drug Administration (FDA)-approved drugs, commonly prescribed to relieve respiratory symptoms, against Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the viral causative agent of the COVID-19 pandemic. (3) Results: Of these FDA-approved antimicrobial drugs, Azithromycin, Niclosamide, and Nitazoxanide showed a promising ability to hinder the replication of a SARS-CoV-2 isolate, with IC₅₀ of 0.32, 0.16, and 1.29 µM, respectively. We provided evidence that several antihistamine and anti-inflammatory drugs could partially reduce SARS-CoV-2 replication in vitro. Furthermore, this study showed that Azithromycin can selectively impair SARS-CoV-2 replication, but not the Middle East Respiratory Syndrome Coronavirus (MERS-CoV). A virtual screening study illustrated that Azithromycin, Niclosamide, and Nitazoxanide bind to the main protease of SARS-CoV-2 (Protein data bank (PDB) ID: 6lu7) in binding mode similar to the reported co-crystalized ligand. Also, Niclosamide displayed hydrogen bond (HB) interaction with the key peptide moiety GLN: 493A of the spike glycoprotein active site. (4) Conclusions: The results suggest that Piroxicam should be prescribed in combination with Azithromycin for COVID-19 patients.

Keywords: COVID-19; SARS-CoV-2; antiviral; drug repurposing; virtual screening.

Figure 1

Dose-inhibition curves for anti-microbial and anti-inflammatory FDA-approved drugs with high selectivity indices against NRC-03-nhCoV. (a) Amikacin sulphate, Azithromycin, Ceftazidime, Doxycycline, Levofloxacin, Moxifloxacin, Niclosamide, and Nitazoxanide, (b) Aspirin, Chlorpheniramine maleate, and Piroxicam. Inhibitory concentration 50% (IC₅₀) values were calculated using nonlinear regression analysis of GraphPad Prism software (version 5.01) by plotting log inhibitor versus normalized response (variable slope).

Figure 2

Chemical structure of ligands α-ketomaide and N3 for SARS-CoV-2 M^pro (PDB ID: 6lu7, 6y2f), and Ligand 1 for SARS-CoV-2 spike glycoprotein (PDB ID: 6vsb).

Figure 3

Visual representation by volumetric image display and analysis (VIDA) of docking with M^pro (PDB ID: 6lu7). (a) Azithromycin docked with the formation of two HBs (green color). (b) Niclosamide (grey color) and Nitazoxanide (thiazole ring with yellow-blue color) occupied the active site without detection of HB.

Figure 4

Visual representation by VIDA for docking with spike glycoprotein (PDB ID: 6vsb). (a) Standard ligand docked inside the receptor (HB in green color), (b) ligand inside the inner grid for validation, (c) Azithromycin docked peripherally, (d) Nitazoxanide docked with formation of weak HB (green color), and (e) Niclosamide docked with formation of strong HB (green color).

Figure 4

Visual representation by VIDA for docking with spike glycoprotein (PDB ID: 6vsb). (a) Standard ligand docked inside the receptor (HB in green color), (b) ligand inside the inner grid for validation, (c) Azithromycin docked peripherally, (d) Nitazoxanide docked with formation of weak HB (green color), and (e) Niclosamide docked with formation of strong HB (green color).

Figure 5

Differential anti-SARS-CoV-2 and Anti-MERS-CoV activities for Azithromycin, Niclosamide, and Nitazoxanide. (a) Anti-SARS-CoV-2 activity for Azithromycin, Niclosamide, and Nitazoxanide, as measured by Plaque reduction assay. (b) Anti-MERS-CoV activity for Azithromycin, Niclosamide, and Nitazoxanide, as measured by Plaque reduction assay.

Figure 6

Visual representation by VIDA for docking with the main protease of MERS-CoV (PDB ID: 4ylu). (a) Niclosamide (green color) and Nitazoxanide (grey color) overlay each other, (b) ligand (grey color), Niclosamide (green color), and Nitazoxanide (grey color with yellow sulfur atom color) inside the inner grid for validation, and (c) Azithromycin with amino outside the grid.

Figure 7

Visual representation by VIDA for docking with the main protease of MERS-CoV (PDB ID: 5x4r). (a) Azithromycin forms HB with ASN:125A, and (b) Niclosamide (grey color) and Nitazoxanide (green color) overlay each other.