The organophosphorus antidotes, so-called oximes, are able to restore the enzymatic function of acetylcholinesterase (AChE) or butyrylcholinesterase (BChE) via cleavage of organophosphate from the active site of the phosphylated enzyme. In this work, the charged pyridinium oximes containing thiocarboxamide moiety were designed, prepared and tested. Their stability and pKa properties were found to be analogous to parent carboxamides (K027, K048 and K203). The inhibitory ability of thiocarboxamides was found in low µM levels for AChE and high µM levels for BChE. Their reactivation properties were screened on human recombinant AChE and BChE inhibited by nerve agent surrogates and paraoxon. One thiocarboxamide was able to effectively restore function of NEMP- and NEDPA-AChE, whereas two thiocarboxamides were able to reactivate BChE inhibited by all tested organophosphates. These results were confirmed by reactivation kinetics, where thiocarboxamides were proved to be effective, but less potent reactivators if compared to carboxamides.

• Keywords
• Cholinesterase, inhibition, organophosphate, oxime, reactivation,
• MeSH
• Acetylcholinesterase metabolism   MeSH
• Butyrylcholinesterase metabolism   MeSH
• Cholinesterase Inhibitors chemical synthesis   chemistry   pharmacology   MeSH
• Humans MeSH
• Molecular Structure MeSH
• Organophosphates chemical synthesis   chemistry   pharmacology   MeSH
• Oximes chemical synthesis   chemistry   pharmacology   MeSH
• Pyridinium Compounds chemical synthesis   chemistry   pharmacology   MeSH
• Sulfhydryl Compounds chemical synthesis   chemistry   pharmacology   MeSH
• Dose-Response Relationship, Drug MeSH
• Structure-Activity Relationship MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Acetylcholinesterase MeSH
• Butyrylcholinesterase MeSH
• Cholinesterase Inhibitors MeSH
• Organophosphates MeSH
• Oximes MeSH
• Pyridinium Compounds MeSH
• Sulfhydryl Compounds MeSH

To date, the only treatments developed for poisoning by organophosphorus compounds, the most toxic chemical weapons of mass destruction, have exhibited limited efficacy and versatility. The available causal antidotes are based on reactivation of the enzyme acetylcholinesterase (AChE), which is rapidly and pseudo-irreversibly inhibited by these agents. In this study, we developed a novel series of monoquaternary reactivators combining permanently charged moieties tethered to position 6- of 3-hydroxypyridine-2-aldoxime reactivating subunit. Highlighted representatives (21, 24, and 27; also coded as K1371, K1374, and K1375, respectively) that contained 1-phenylisoquinolinium, 7-amino-1-phenylisoquinolinium and 4-carbamoylpyridinium moieties as peripheral anionic site ligands, respectively, showed efficacy superior or comparable to that of the clinically used standards. More importantly, these reactivators exhibited wide-spectrum efficacy and were minutely investigated via determination of their reactivation kinetics in parallel with molecular dynamics simulations to study their mechanisms of reactivation of the tabun-inhibited AChE conjugate. To further confirm the potential applicability of these candidates, a mouse in vivo assay was conducted. While K1375 had the lowest acute toxicity and the most suitable pharmacokinetic profile, the oxime K1374 with delayed elimination half-life was the most effective in ameliorating the signs of tabun toxicity. Moreover, both in vitro and in vivo, the versatility of the agents was substantially superior to that of clinically used standards. Their high efficacy and broad-spectrum capability make K1374 and K1375 promising candidates that should be further investigated for their potential as nerve agents and insecticide antidotes.

• Keywords
• Acetylcholinesterase, Butyrylcholinesterase, Insecticides, Nerve agents, Organophosphates, Organophosphorus compounds, Oxime reactivator,
• MeSH
• Acetylcholinesterase drug effects   metabolism   MeSH
• Antidotes chemical synthesis   chemistry   pharmacology   MeSH
• Mice, Inbred BALB C MeSH
• Mice MeSH
• Oximes chemical synthesis   chemistry   pharmacology   MeSH
• Cholinesterase Reactivators chemical synthesis   chemistry   pharmacology   MeSH
• Molecular Dynamics Simulation MeSH
• Structure-Activity Relationship MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Mice MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Acetylcholinesterase MeSH
• Antidotes MeSH
• Oximes MeSH
• Cholinesterase Reactivators MeSH

The acetylcholinesterase (AChE) reactivators (e.g., obidoxime, asoxime) became an essential part of organophosphorus (OP) poisoning treatment, together with atropine and diazepam. They are referred to as a causal treatment of OP poisoning, because they are able to split the OP moiety from AChE active site and thus renew its function. In this approach, fifteen novel AChE reactivators were determined. Their molecular design originated from former K-oxime compounds K048 and K074 with remaining oxime part of the molecule and modified part with heteroarenium moiety. The novel compounds were prepared, evaluated in vitro on human AChE (HssAChE) inhibited by tabun, paraoxon, methylparaoxon or DFP and compared to commercial HssAChE reactivators (pralidoxime, methoxime, trimedoxime, obidoxime, asoxime) or previously prepared compounds (K048, K074, K075, K203). Some of presented oxime reactivators showed promising ability to reactivate HssAChE comparable or higher than the used standards. The molecular modelling study was performed with one compound that presented the ability to reactivate GA-inhibited HssAChE. The SAR features concerning the heteroarenium part of the reactivator's molecule are described.

• Keywords
• acetylcholinesterase, in vitro, molecular docking, organophosphate, oxime, reactivation,
• MeSH
• Acetylcholinesterase metabolism   MeSH
• Cholinesterase Inhibitors toxicity   MeSH
• Spectrometry, Mass, Electrospray Ionization MeSH
• Inhibitory Concentration 50 MeSH
• Humans MeSH
• Carbon-13 Magnetic Resonance Spectroscopy MeSH
• Organophosphorus Compounds toxicity   MeSH
• Proton Magnetic Resonance Spectroscopy MeSH
• Cholinesterase Reactivators chemical synthesis   chemistry   pharmacology   MeSH
• Recombinant Proteins metabolism   MeSH
• Molecular Docking Simulation * MeSH
• In Vitro Techniques MeSH
• Structure-Activity Relationship MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Acetylcholinesterase MeSH
• Cholinesterase Inhibitors MeSH
• Organophosphorus Compounds MeSH
• Cholinesterase Reactivators MeSH
• Recombinant Proteins MeSH

Chemical warfare agents constitute an increasing threat to both military and civilian populations. Therefore, effective prophylactic approaches are urgently needed. Herein, we present a novel hybrid compound which is able not only to keep acetylcholinesterase resistant to organophosphate (OP) inhibitors, but also to serve as an enzyme reactivator in the case of OP intoxication.

• Publication type
• Journal Article MeSH