Ebselen derivatives inhibit SARS-CoV-2 replication by inhibition of its essential proteins – PL pro and M pro proteases, and nsp14 guanine N7- methyltransferase (preprint)

Proteases encoded by SARS-CoV-2 constitute a promising target for new therapies against COVID-19. SARS-CoV-2 main protease (M pro , 3CL pro ) and papain-like protease (PL pro ) are responsible for viral polyprotein cleavage – a process crucial for viral survival and replication. Recently it was shown that 2-phenylbenzisoselenazol-3(2 H )-one (ebselen), an organoselenium anti-inflammatory small-molecule drug, is a potent, covalent inhibitor of both the proteases and its potency was evaluated in enzymatic and anti-viral assays. In this study, we screened a collection of 34 ebselen and ebselen diselenide derivatives for SARS-CoV-2 PL pro and M pro inhibitors. Our studies revealed that ebselen derivatives are potent inhibitors of both the proteases. We identified three PL pro and four M pro inhibitors superior to ebselen. Independently, ebselen was shown to inhibit the N7-methyltransferase activity of SARS-CoV-2 nsp14 protein involved in viral RNA cap modification. Hence, selected compounds were also evaluated as nsp14 inhibitors. In the second part of our work, we employed 11 ebselen analogues – bis(2-carbamoylaryl)phenyl diselenides – in biological assays to evaluate their anti-SARS-CoV-2 activity in Vero E6 cells. We present their antiviral and cytoprotective activity and also low cytotoxicity. Our work shows that ebselen, its derivatives and diselenide analogues constitute a promising platform for development of new antivirals targeting the SARS-CoV-2 virus.

Identification and Evaluation of Potential SARS-CoV-2 Antiviral Agents Targeting mRNA Cap Guanine N7-Methyltransferase (preprint)

SARS-CoV-2, the cause of the currently ongoing COVID-19 pandemic, encodes its own mRNA capping machinery. Insights into this capping system may provide new ideas for therapeutic interventions and drug discovery. In this work, we employ a previously developed Py-FLINT screening approach to study the inhibitory effects of compounds against the cap guanine N7-methyltransferase enzyme, which is involved in SARS-CoV-2 mRNA capping. We screened five commercially available libraries (7039 compounds in total) to identify 83 inhibitors with IC50 < 50 μM, which were further validated using RP HPLC and dot blot assays. Novel fluorescence anisotropy binding assays were developed to examine the targeted binding site. The inhibitor structures were analyzed for structure-activity relationships in order to define common structural patterns. Finally, the most potent inhibitors were tested for antiviral activity on SARS-CoV-2 in a cell based assay