Disulfiram can inhibit MERS and SARS coronavirus papain-like proteases via different modes

Abstract

Severe acute respiratory syndrome coronavirus (SARS-CoV) emerged in southern China in late 2002 and caused a global outbreak with a fatality rate around 10% in 2003. Ten years later, a second highly pathogenic human CoV, MERS-CoV, emerged in the Middle East and has spread to other countries in Europe, North Africa, North America and Asia. As of November 2017, MERS-CoV had infected at least 2102 people with a fatality rate of about 35% globally, and hence there is an urgent need to identify antiviral drugs that are active against MERS-CoV. Here we show that a clinically available alcohol-aversive drug, disulfiram, can inhibit the papain-like proteases (PLs) of MERS-CoV and SARS-CoV. Our findings suggest that disulfiram acts as an allosteric inhibitor of MERS-CoV PL but as a competitive (or mixed) inhibitor of SARS-CoV PL. The phenomenon of slow-binding inhibition and the irrecoverability of enzyme activity after removing unbound disulfiram indicate covalent inactivation of SARS-CoV PL by disulfiram, while synergistic inhibition of MERS-CoV PL by disulfiram and 6-thioguanine or mycophenolic acid implies the potential for combination treatments using these three clinically available drugs.

Recent discovery and development of inhibitors targeting coronaviruses

“…This drug was reported to inhibit the activity of methyltransferase [93], kinase [94], and urease [94], all by reacting with cysteine residues, suggesting broad-spectrum characteristics [95]. Notably, disulfiram (47) has been reported as an allosteric inhibitor of MERS-CoV PL pro [95]. It was suggested that the administration of 41 together with compound 44 and/or 45, could synergistically inhibit MERS-CoV papain-like protease [95].…”

“…Notably, disulfiram (47) has been reported as an allosteric inhibitor of MERS-CoV PL pro [95]. It was suggested that the administration of 41 together with compound 44 and/or 45, could synergistically inhibit MERS-CoV papain-like protease [95].…”

Porcine epidemic diarrhea virus papain-like protease 2 can be noncompetitively inhibited by 6-thioguanine

“…Several coronaviral PL pro inhibitors have been identified in previous studies (Chen et al, 2009;Cheng et al, 2015;Chou et al, 2008;Lin et al, 2018;Ratia et al, 2008). In the present study, these compounds were screened to determine whether they can inhibit PEDV PL2 pro (Table 2).…”

“…Like other CoVs, PEDV depends on its own proteases, including main protease (M pro ) and papain-like protease (PL pro ) to cleave the polyprotein, and alpha CoVs have both papain-like protease 1 (PL1 pro ) and papain-like protease 2 (PL2 pro ) (Lee, 2015;Wojdyla et al, 2010). Polyprotein cleavage is required for viral maturation and thus these proteases are ideal antiviral targets (Bacha et al, 2008;Cheng et al, 2015;Chou T et al, 2008;Kumar et al, 2017;Lin et al, 2018;Park et al, 2012;Ratia et al, 2008;Wu et al, 2006). Furthermore, in contrast to highly variable spike proteins targeted by antibodies (Li et al, 2005(Li et al, , 2017; Wang et al, 2013;Wu et al, 2009), proteases with more conserved structure and catalytic function may serve as a general target across different CoVs Bailey-Elkin et al, 2014;Chou et al, 2014;Ho et al, 2015;Ratia et al, 2006;Yang et al, 2003).…”

“…Further studies suggest that PEDV PL2 pro exhibits much higher DUB activity than that of SARS-and MERS-CoV PL pro s and can be inhibited by the anti-leukemia drug 6-thioguanine (6TG). 6TG has been found to be able to inhibit multiple DUB enzymes including human USP2 as well as SARS-and MERS-CoV PL pro s (Chen et al, 2009;Cheng et al, 2015;Chou et al, 2008;Chuang et al, 2018;Lin et al, 2018). Inhibition assays and docking simulations were used to clarify the detailed inhibition mechanism of 6TG against PEDV PL2 pro .…”