Ebselen derivatives inhibit SARS-CoV-2 replication by inhibition of its essential proteins: PLpro and Mpro proteases, and nsp14 guanine N7-methyltransferase

Abstract

Proteases encoded by SARS-CoV-2 constitute a promising target for new therapies against COVID-19. SARS-CoV-2 main protease (Mpro, 3CLpro) and papain-like protease (PLpro) are responsible for viral polyprotein cleavage—a process crucial for viral survival and replication. Recently it was shown that 2-phenylbenzisoselenazol-3(2H)-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 antiviral assays. In this study, we screened a collection of 34 ebselen and ebselen diselenide derivatives for SARS-CoV-2 PLpro and Mpro inhibitors. Our studies revealed that ebselen derivatives are potent inhibitors of both the proteases. We identified three PLpro and four Mpro 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.

New insights in the mechanism of the SARS-CoV-2 Mpro inhibition by benzisoselenazolones and diselenides

“…Subsequently, it was demonstrated that ebselen also inhibits the papain-like protease (PL pro ) from SARS-CoV-1 and SARS-CoV-2 (with an IC50= 2.26 µM for PL pro of SARS-CoV-2) 11 . The same authors of such pioneering study recently also reported a series of ebselen analogues as potent inhibitors of nsp14 guanine N7-methyltransferase 12 .…”

Selenium compounds as promising antiviral agents

“…Ebselen and its phenyl substituted derivatives have been screened as inhibitors for SARS-CoV-2 M Pro , PL Pro and other non-structural proteins (nsps). 105–110 Biological assays employed to evaluate their anti-SARS-CoV-2 activity in Vero cells revealed that some of these compounds are superior to ebselen as antiviral agents. 110 Like M Pro , the papain-like protease (PL Pro ) of SARS-CoV-2 is also a cysteine protease and is pivotal for viral replication.…”

“…105–110 Biological assays employed to evaluate their anti-SARS-CoV-2 activity in Vero cells revealed that some of these compounds are superior to ebselen as antiviral agents. 110 Like M Pro , the papain-like protease (PL Pro ) of SARS-CoV-2 is also a cysteine protease and is pivotal for viral replication. The IC 50 value for most of the ebselen derivatives against SARS-CoV-2 M Pro inhibition lies in the 1–7.4 μM range.…”

“…107 The IC 50 values for M Pro and PL Pro are in the nano-molar and micro-molar range, respectively. 110 A number of 21 derivatives with R = substituted phenyl and pyridyl groups at 0.3 μM concentration have been screened as M Pro and PL Pro inhibitors by HPLC and FRET assays. Compounds 21 with R = 2-methoxyphenyl and 3-fluoropydridyl have been found to be six-fold and three-fold more potent than ebselen in inhibiting SARS-CoV-2 viral replication.…”

“…106,108 Some of these compounds have also been identified as potent inhibitors of both the proteases, PL pro and M pro , as well as the nsp14 protein of SARS-CoV-2. 110…”