Amantadine has potential for the treatment of COVID-19 because it inhibits known and novel ion channels encoded by SARS-CoV-2.

The dire need for COVID-19 treatments has inspired strategies of repurposing approved drugs. Amantadine has been suggested as a candidate, and cellular as well as clinical studies have indicated beneficial effects of this drug. We demonstrate that amantadine and hexamethylene-amiloride (HMA), but not rimantadine, block the ion channel activity of Protein E from SARS-CoV-2, a conserved viroporin among coronaviruses. These findings agree with their binding to Protein E as evaluated by solution NMR and molecular dynamics simulations. Moreover, we identify two novel viroporins of SARS-CoV-2; ORF7b and ORF10, by showing ion channel activity in a X. laevis oocyte expression system. Notably, amantadine also blocks the ion channel activity of ORF10, thereby providing two ion channel targets in SARS-CoV-2 for amantadine treatment in COVID-19 patients. A screen of known viroporin inhibitors on Protein E, ORF7b, ORF10 and Protein 3a from SARS-CoV-2 revealed inhibition of Protein E and ORF7b by emodin and xanthene, the latter also blocking Protein 3a. This illustrates a general potential of well-known ion channel blockers against SARS-CoV-2 and specifically a dual molecular basis for the promising effects of amantadine in COVID-19 treatment. We therefore propose amantadine as a novel, cheap, readily available and effective way to treat COVID-19.

Insights to the Binding of a Selective Adenosine A3 Receptor Antagonist Using Molecular Dynamic Simulations, MM-PBSA and MM-GBSA Free Energy Calculations, and Mutagenesis.

Adenosine A3 receptor (A3R) is a promising drug target cancer and for a number of other conditions like inflammatory diseases, including asthma and rheumatoid arthritis, glaucoma, chronic obstructive pulmonary disease, and ischemic injury. Currently, there is no experimentally determined structure of A3R. We explored the binding profile of O4-{[3-(2,6-dichlorophenyl)-5-methylisoxazol-4-yl]carbonyl}-2-methyl-1,3-thiazole-4-carbohydroximamide (K18), which is a new specific and competitive antagonist at the orthosteric binding site of A3R. MD simulations and MM-GBSA calculations of the WT A3R in complex with K18 combined with in vitro mutagenic studies show that the most plausible binding conformation for the dichlorophenyl group of K18 is oriented toward trans-membrane helices (TM) 5, 6 and reveal important residues for binding. Further, MM-GBSA calculations distinguish mutations that reduce or maintain or increase antagonistic activity. Our studies show that selectivity of K18 toward A3R is defined not only by direct interactions with residues within the orthosteric binding area but also by remote residues playing a significant role. Although V1695.30 is considered to be a selectivity filter for A3R binders, when it was mutated to glutamic acid, K18 maintained antagonistic potency, in agreement with our previous results obtained for agonists binding profile investigation. Mutation of the direct interacting residue L903.32 in the low region and the remote L2647.35 in the middle/upper region to alanine increases antagonistic potency, suggesting an empty space in the orthosteric area available for increasing antagonist potency. These results approve the computational model for the description of K18 binding at A3R, which we previously performed for agonists binding to A3R, and the design of more effective antagonists based on K18.