Inhibitor Report for: A-232-Nerve-agent

Novichoks are a novel class of nerve agents (also referred to as the A-series) that were employed in several poisonings over the last few years. This calls for the development of novel countermeasures that can be applied in protective concepts (e.g., protective clothing) or in decontamination methods. The Zr metal-organic framework MOF-808 has recently emerged as a promising catalyst in the hydrolysis of the V- and G-series of nerve agents as well as their simulants. In this paper, we report a detailed study of the degradation of three Novichok agents by MOF-808 in buffers with varying pH. MOF-808 is revealed to be a highly efficient and regenerable catalyst for Novichok agent hydrolysis under basic conditions. In contrast to the V- and G-series of agents, degradation of Novichoks is demonstrated to proceed in two consecutive hydrolysis steps. Initial extremely rapid P-F bond breaking is followed by MOF-catalyzed removal of the amidine group from the intermediate product. The intermediate thus acted as a competitive substrate that was rate-determining for the whole two-step degradation route. Under acidic conditions, the amidine group in Novichok A-230 is more rapidly hydrolyzed than the P-F bond, giving rise to another moderately toxic intermediate. This intermediate could in turn be efficiently hydrolyzed by MOF-808 under basic conditions. These experimental observations were corroborated by density functional theory calculations to shed light on molecular mechanisms.

Organophosphorus nerve agents (OPNAs) are highly toxic compounds inhibiting cholinergic enzymes in the central and autonomic nervous systems and neuromuscular junctions, causing severe intoxications in humans. Medical countermeasures and efficient decontamination solutions are needed to counteract the toxicity of a wide spectrum of harmful OPNAs including G, V and Novichok agents. Here, we describe the use of engineered OPNA-degrading enzymes for the degradation of various toxic agents including insecticides, a series of OPNA surrogates, as well as real chemical warfare agents (cyclosarin, sarin, soman, tabun, VX, A230, A232, A234). We demonstrate that only two enzymes can degrade most of these molecules at high concentrations (25 mM) in less than 5 min. Using surface assays adapted from NATO AEP-65 guidelines, we further show that enzyme-based solutions can decontaminate 97.6% and 99.4% of 10 gm(-)(2) of soman- and VX-contaminated surfaces, respectively. Finally, we demonstrate that these enzymes can degrade ethyl-paraoxon down to sub-inhibitory concentrations of acetylcholinesterase, confirming their efficacy from high to micromolar doses.

To identify biomarkers of ethyl (1-(diethylamino)ethylidene)phosphoramidofluoridate (A234)- or methyl (1-(diethylamino)ethylidene)phosphoramidofluoridate (A232)-inhibited butyrylcholinesterase (BChE), we investigated nonapeptide adducts containing the active site serine, which plays a key role in enzyme activity, using LC-MS/HRMS. Biomarkers were acquired as expected, and they exhibited a significant amount of fragment ions from the inhibiting agent itself, in contrast to the MS2 spectra of conventional nerve agents. These biomarkers had a higher abundance of [M+2H](2+) ions than [M+H](+) ions, making doubly charged ions more suitable for trace analysis.

Novichoks are a novel class of nerve agents (also referred to as the A-series) that were employed in several poisonings over the last few years. This calls for the development of novel countermeasures that can be applied in protective concepts (e.g., protective clothing) or in decontamination methods. The Zr metal-organic framework MOF-808 has recently emerged as a promising catalyst in the hydrolysis of the V- and G-series of nerve agents as well as their simulants. In this paper, we report a detailed study of the degradation of three Novichok agents by MOF-808 in buffers with varying pH. MOF-808 is revealed to be a highly efficient and regenerable catalyst for Novichok agent hydrolysis under basic conditions. In contrast to the V- and G-series of agents, degradation of Novichoks is demonstrated to proceed in two consecutive hydrolysis steps. Initial extremely rapid P-F bond breaking is followed by MOF-catalyzed removal of the amidine group from the intermediate product. The intermediate thus acted as a competitive substrate that was rate-determining for the whole two-step degradation route. Under acidic conditions, the amidine group in Novichok A-230 is more rapidly hydrolyzed than the P-F bond, giving rise to another moderately toxic intermediate. This intermediate could in turn be efficiently hydrolyzed by MOF-808 under basic conditions. These experimental observations were corroborated by density functional theory calculations to shed light on molecular mechanisms.

Organophosphorus nerve agents (OPNAs) are highly toxic compounds inhibiting cholinergic enzymes in the central and autonomic nervous systems and neuromuscular junctions, causing severe intoxications in humans. Medical countermeasures and efficient decontamination solutions are needed to counteract the toxicity of a wide spectrum of harmful OPNAs including G, V and Novichok agents. Here, we describe the use of engineered OPNA-degrading enzymes for the degradation of various toxic agents including insecticides, a series of OPNA surrogates, as well as real chemical warfare agents (cyclosarin, sarin, soman, tabun, VX, A230, A232, A234). We demonstrate that only two enzymes can degrade most of these molecules at high concentrations (25 mM) in less than 5 min. Using surface assays adapted from NATO AEP-65 guidelines, we further show that enzyme-based solutions can decontaminate 97.6% and 99.4% of 10 gm(-)(2) of soman- and VX-contaminated surfaces, respectively. Finally, we demonstrate that these enzymes can degrade ethyl-paraoxon down to sub-inhibitory concentrations of acetylcholinesterase, confirming their efficacy from high to micromolar doses.

To identify biomarkers of ethyl (1-(diethylamino)ethylidene)phosphoramidofluoridate (A234)- or methyl (1-(diethylamino)ethylidene)phosphoramidofluoridate (A232)-inhibited butyrylcholinesterase (BChE), we investigated nonapeptide adducts containing the active site serine, which plays a key role in enzyme activity, using LC-MS/HRMS. Biomarkers were acquired as expected, and they exhibited a significant amount of fragment ions from the inhibiting agent itself, in contrast to the MS2 spectra of conventional nerve agents. These biomarkers had a higher abundance of [M+2H](2+) ions than [M+H](+) ions, making doubly charged ions more suitable for trace analysis.

Conformations of Calpha backbones in X-ray structures of most organophosphate (OP)-inhibited human acetylcholinesterases (hAChEs) have been previously shown to be similar to that of the native hAChE. One of the exceptions is the structure of the diethylphosphoryl-hAChE conjugate, where stabilization of a large ethoxy group into the acyl pocket (AP) of hAChE-triggered notable loop distortions and consequential dissociation of the hAChE homodimer. Recently, six X-ray structures of hAChE conjugated with large OP nerve agents of the A-type, Novichoks, have been deposited to PDB. In this study we analyzed backbone conformation shifts in those structures, as well as in OP-hAChE conjugates formed by Paraoxon, Soman, Tabun, and VX. A Java-based pairwise alpha carbon comparison tool (PACCT 3) was used for analysis. Surprisingly, despite the snug fit of large substituents on phosphorus, inside Novichok-conjugated hAChEs only minor conformational changes were detected in their backbones. Small magnitudes of observed changes were due to a 1.2-2.4 A shift of the entire conjugated OP away from the AP. It thus appears that the small AP of AChEs can accommodate, without distortion, substituents of the size of ethoxy or butyryl groups, provided that conjugated OP is "pulled" away from the AP. This observation has practical consequences in the structure-based design of nucleophilic reactivation antidotes as well as in the definition of the AChE specificity that relies on the size of its AP

Novichok (NV) nerve agents were recently added to the list of Schedule 1 chemicals of the Chemical Weapons Convention. There is a well-accepted method for assessment of nerve agent exposure based on mass spectrometric analysis of a nonapeptide with the serine-198 residue modified by the nerve agent, but this approach has not yet been reported for the class of NV agents and requires the availability of reference standards, which may be a limitation for NV agent exposure assessment. Thus, a goal of this study was to first verify the utility of the nonapeptide method for the characterization of human plasma samples exposed in vitro to the NV agents A-230, A-232, and A-234. A second aim was to evaluate the possibility of identifying unknown exposures by applying precursor ion scanning in combination with high resolution mass spectrometry (HRMS). Thus, precursor ion scanning, with a generic fragment ion (m/z 778) of the nonapeptide, was used to pinpoint any modified nonapeptide, while HRMS was used for structural elucidation of the adduct moiety. By this approach, use of HRMS enabled differentiation between adducts of agents with similar molecular masses. A new unique feature that could be exploited for NV nonapeptide analysis was that the modification was released from the peptide during fragmentation in the mass spectrometer and was detected in the low-mass region of the mass spectrum. This low-mass region was extremely informative and contributed to the assignment of the structure of the particular agent used, which is especially important in case no reference materials are available. The presented method is important for verification purposes by the Organisation for Prohibition of Chemical Weapons (OPCW), e.g., in case of investigations of alleged use of NV agents, and for regular forensic investigations.

Novichok is an organophosphate compound found as a nerve agent chemical weapon. However, the information about its chemical properties, biological activities, and molecular interactions in the body are still protected under the 'top secret' security clearance. Novichok, with the codes A230, A232 and A234, is a compound whose structure has been successfully determined. The compound is synthesized from a precursor through a nucleophilic substitution reaction. Novichok agents are considered more potent than VX gas and can be applied in unitary and binary forms. This compound has ability for the binding with acetylcholinesterase (AChE) due to inability of acetylcholine metabolism. AChE catalyzes the rapid hydrolysis of acetylcholine to acetate and choline. The treatment of Novichok agent poisoning is similar to management of other nerve agents, such as atropine and pralidoxime administered intravenously. In this paper, we reviewed the Novichok component from chemical and biological perspective. Moreover, we discussed the potential molecular interaction and treatment of this compound.

The Novichok, or "newcomer" class of nerve agents are lesser characterized, weaponized organophosphate agents. The use of known Novichok agents in warfare is banned under the Chemical Weapons Convention of 1997. Novichok agents are considered more potent than VX gas and can be applied in unitary and binary forms. Like other nerve agents, Novichok agents irreversibly bind acetylcholinesterase and produce a cholinergic toxidrome. Uniquely, these agents are thought to also target neurons in the peripheral nervous system. Delayed treatment or massive exposure may therefore cause a debilitating neuropathy. The recent 2018 assassination attempt of Russian dissident Sergei Skripal and his daughter Yulia in the United Kingdom highlights the importance of recognizing the potential lethal effects of these nerve agents. Treatment of Novichok agent poisoning is similar to management of other nerve agents. Given increasing worldwide incidents attributed to chemical weapons such as Novichok agents, clinicians should know how to rapidly recognize symptoms of acute poisoning and administer life-saving antidotal therapy, when indicated.

The Cold War period is characterized by the infighting between the Western countries and the USSR in diverse areas. One of such fields was development of the weapons of mass destruction. Within various programs on both sides, a wide scale of different agents have been developed. However, information about some of them are still protected under the designation "top secret". Notwithstanding, in history several cases are known when such information beheld the daylight. One of such cases was the program FOLIANT and NOVICHOK. Both programs were developed by the USSR as a reaction to English/American invention of VX agent. If at least a part of available information is truthful, we can allege that these compounds belong among the most toxic synthetic agents ever. Within this contribution, we have reviewed available Eastern and Western data about the A-agents and their precursors, so-called NOVICHOKs, including their history, synthesis, physical-chemical properties, pharmacological characteristics and clinical manifestation.