Repurposing existing drugs: identification of irreversible IMPDH inhibitors by high-throughput screening

Abstract

Inosine 5′-monophosphate dehydrogenase (IMPDH) is an essential enzyme for the production of guanine nucleotides. Disruption of IMPDH activity has been explored as a therapeutic strategy for numerous purposes, such as for anticancer, immunosuppression, antiviral, and antimicrobial therapy. In the present study, we established a luciferase-based high-throughput screening system to identify IMPDH inhibitors from our chemical library of known bioactive small molecules. The screening of 1400 compounds resulted in the discovery of three irreversible inhibitors: disulfiram, bronopol, and ebselen. Each compound has a distinct chemical moiety that differs from other reported IMPDH inhibitors. Further evaluation revealed that these compounds are potent inhibitors of IMPDHs with kon values of 0.7 × 104 to 9.3 × 104 M−1·s−1. Both disulfiram and bronopol exerted similar degree of inhibition to protozoan and mammalian IMPDHs. Ebselen showed an intriguing difference in mode of inhibition for different IMPDHs, with reversible and irreversible inhibition to each Cryptosporidium parvum IMPDH and human IMPDH type II, respectively. In the preliminary efficacy experiment against cryptosporidiosis in severe combined immunodeficiency (SCID) mouse, a decrease in the number of oocyst shed was observed upon the oral administration of disulfiram and bronopol, providing an early clinical proof-of-concept for further utilization of these compounds as IMPDH inhibitors.

Selenium and selenoproteins in viral infection with potential relevance to COVID-19

“…Ebselen has been found to have therapeutic potential against many infectious diseases. In most cases, ebselen acts as a covalent inhibitor of numerous thiol-dependent enzymes or functional proteins in various pathogens [ 134 , 135 , 136 , 137 , 138 , 139 , 140 , 141 , 142 , 143 , 144 , 145 , 146 ]. The selenol derived from ebselen is reactive to cysteine residues in proteins.…”

“…Following a high intake of dietary selenium or supranutritional selenium supplementation beyond the requirement for selenoprotein biosynthesis, small molecular weight selenium compounds are accumulated [ 140 , 141 , 142 , 143 , 144 , 145 ]. Hydrogen selenide, methylselenol, dimethylselenide and dimethyldiselenide are volatile small molecules and thus are likely to be found in the respiratory tract [ 147 , 153 , 154 ].…”

In cellulo crystallization of Trypanosoma brucei IMP dehydrogenase enables the identification of genuine co-factors

“…If inhibited, the imbalance between the guanine and adenine nucleotide pools has dramatic consequences for cell proliferation 16 , rendering IMPDHs into a suitable cellular target of drugs widely used to date in chemotherapy as antivirals or as immunosuppressive and antitumor agents 17 . Due to the crucial role in de novo nucleotide biosynthesis and the significant clinical relevance, IMPDHs from various species are in the focus of investigations 18,19 .…”

Evaluation of Bronopol and Disulfiram as Potential Candidatus Liberibacter asiaticus Inosine 5′-Monophosphate Dehydrogenase Inhibitors by Using Molecular Docking and Enzyme Kinetic

“…Mycophenolate mofetil is a prodrug of mycophenolic acid [60], yielding K i = 24.42 µM ( Figure S7e). Three compounds, namely, disulfiram, bronopol, and ebselen, have been repurposed as IMPDH inhibitors [61]. Bronopol had the best inhibitory effect with K i = 234 nM (Figure 5a).…”