The risk of the use of toxic chemicals for unlawful acts has been a matter of concern for different governments and multilateral agencies. The Organisation for the Prohibition of Chemical Weapons (OPCW), which oversees the implementation of the Chemical Weapons Convention (CWC), considering recent events employing chemical warfare agents as means of assassination, has recently included in the CWC "Annex on Chemicals" some organophosphorus compounds that are regarded as acting in a similar fashion to the classical G- and V-series of nerve agents, inhibiting the pivotal enzyme acetylcholinesterase. Therefore, knowledge of the activity of the pyridinium oximes, the sole class of clinically available acetylcholinesterase reactivators to date, is plainly justified. In this paper, continuing our research efforts in medicinal chemistry on this class of toxic chemicals, we synthesized an A-230 nerve agent surrogate and applied a modified Ellman's assay to evaluate its ability to inhibit our enzymatic model, acetylcholinesterase from Electrophorus eel, and if the clinically available antidotes are able to rescue the enzyme activity for the purpose of relating the findings to the previously disclosed in silico data for the authentic nerve agent and other studies with similar A-series surrogates. Our experimental data indicates that pralidoxime is the most efficient compound for reactivating acetylcholinesterase inhibited by A-230 surrogate, which is the opposite of the in silico data previously disclosed.

• Keywords
• A-230, Acetylcholinesterase, Antidotes, Chemical Weapons Convention, Nerve agent surrogates,
• MeSH
• Acetylcholinesterase * metabolism   MeSH
• Antidotes pharmacology   MeSH
• Chemical Warfare Agents * toxicity   MeSH
• Cholinesterase Inhibitors * toxicity   MeSH
• Nerve Agents * toxicity   MeSH
• Organothiophosphorus Compounds toxicity   MeSH
• Oximes * pharmacology   MeSH
• Pralidoxime Compounds pharmacology   MeSH
• Pyridinium Compounds * pharmacology   MeSH
• Cholinesterase Reactivators * pharmacology   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Acetylcholinesterase * MeSH
• Antidotes MeSH
• Chemical Warfare Agents * MeSH
• Cholinesterase Inhibitors * MeSH
• Nerve Agents * MeSH
• Organothiophosphorus Compounds MeSH
• Oximes * MeSH
• pralidoxime MeSH Browser
• Pralidoxime Compounds MeSH
• Pyridinium Compounds * MeSH
• Cholinesterase Reactivators * MeSH

The misuse of novichok agents in assassination attempts has been reported in the international media since 2018. These relatively new class of neurotoxic agents is claimed to be more toxic than the agents of the G and V series and so far, there is no report yet in literature about potential antidotes against them. To shed some light into this issue, we report here the design and synthesis of NTMGMP, a surrogate of A-242 and also the first surrogate of a novichok agent useful for experimental evaluation of antidotes. Furthermore, the efficiency of the current commercial oximes to reactivate NTMGMP-inhibited acetylcholinesterase (AChE) was evaluated. The Ellman test was used to confirm the complete inhibition of AChE, and to compare the subsequent rates of reactivation in vitro as well as to evaluate aging. In parallel, molecular docking, molecular dynamics and MM-PBSA studies were performed on a computational model of the human AChE (HssAChE)/NTMGMP complex to assess the reactivation performances of the commercial oximes in silico. Experimental and theoretical studies matched the exact hierarchy of efficiency and pointed to trimedoxime as the most promising commercial oxime for reactivation of AChE inhibited by A-242.

• Keywords
• A-242, AChE, Commercial reactivators, Novichoks, Surrogates,
• MeSH
• Acetylcholinesterase MeSH
• Antidotes pharmacology   MeSH
• Cholinesterase Inhibitors toxicity   MeSH
• Humans MeSH
• Nerve Agents * toxicity   MeSH
• Oximes pharmacology   MeSH
• Cholinesterase Reactivators * pharmacology   MeSH
• Molecular Docking Simulation MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Acetylcholinesterase MeSH
• Antidotes MeSH
• Cholinesterase Inhibitors MeSH
• Nerve Agents * MeSH
• Oximes MeSH
• Cholinesterase Reactivators * MeSH

Organophosphorus poisoning caused by some pesticides and nerve agents is a life-threating condition that must be swiftly addressed to avoid casualties. Despite the availability of medical countermeasures, the clinically available compounds lack a broad spectrum, are not effective towards all organophosphorus toxins, and have poor pharmacokinetics properties to allow them crossing the blood-brain barrier, hampering cholinesterase reactivation at the central nervous system. In this work, we designed and synthesised novel isatin derivatives, linked to a pyridinium 4-oxime moiety by an alkyl chain with improved calculated properties, and tested their reactivation potency against paraoxon- and NEMP-inhibited acetylcholinesterase in comparison to the standard antidote pralidoxime. Our results showed that these compounds displayed comparable in vitro reactivation also pointed by the in silico studies, suggesting that they are promising compounds to tackle organophosphorus poisoning.

• Keywords
• Isatin, antidotes, cholinesterase reactivators, nerve agents, organophosphorus poisoning, pyridine oximes,
• MeSH
• Acetylcholinesterase drug effects   MeSH
• Isatin pharmacology   MeSH
• Computer Simulation MeSH
• Pyridines pharmacology   MeSH
• Cholinesterase Reactivators pharmacology   MeSH
• In Vitro Techniques MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Acetylcholinesterase MeSH
• Isatin MeSH
• pyridine MeSH Browser
• Pyridines MeSH
• Cholinesterase Reactivators MeSH

This article describes acetylcholinesterase (AChE), an enzyme involved in parasympathetic neurotransmission, its activity, and how its inhibition can be pharmacologically useful for treating dementia, caused by Alzheimer's disease, or as a warfare method due to the action of nerve agents. The chemical concepts related to the irreversible inhibition of AChE, its reactivation, and aging are discussed, along with a relationship to the current international legislation on chemical weapons.

• Keywords
• Alzheimer’s disease, Chemical Weapons Convention, acetylcholinesterase, nerve agents,
• MeSH
• Acetylcholinesterase * metabolism   MeSH
• Alzheimer Disease * drug therapy   enzymology   MeSH
• Chemical Warfare legislation & jurisprudence   MeSH
• Cholinesterase Inhibitors therapeutic use   MeSH
• GPI-Linked Proteins antagonists & inhibitors   metabolism   MeSH
• Humans MeSH
• Nerve Agents * MeSH
• Aging metabolism   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH
• Names of Substances
• Acetylcholinesterase * MeSH
• ACHE protein, human MeSH Browser
• Cholinesterase Inhibitors MeSH
• GPI-Linked Proteins MeSH
• Nerve Agents * MeSH

Casualties caused by organophosphorus pesticides are a burden for health systems in developing and poor countries. Such compounds are potent acetylcholinesterase irreversible inhibitors, and share the toxic profile with nerve agents. Pyridinium oximes are the only clinically available antidotes against poisoning by these substances, but their poor penetration into the blood-brain barrier hampers the efficient enzyme reactivation at the central nervous system. In searching for structural factors that may be explored in future SAR studies, we evaluated neutral aryloximes as reactivators for paraoxon-inhibited Electrophorus eel acetylcholinesterase. Our findings may result into lead compounds, useful for development of more active compounds for emergencies and supportive care.

• Keywords
• acetylcholinesterase, antidotes, drug design, neutral oximes, pesticides,
• MeSH
• Acetylcholinesterase metabolism   MeSH
• Electrophorus metabolism   MeSH
• Enzyme Reactivators chemistry   pharmacology   MeSH
• Molecular Structure MeSH
• Oximes chemistry   pharmacology   MeSH
• Paraoxon toxicity   MeSH
• Fish Proteins metabolism   MeSH
• In Vitro Techniques MeSH
• Structure-Activity Relationship MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Acetylcholinesterase MeSH
• Enzyme Reactivators MeSH
• Oximes MeSH
• Paraoxon MeSH
• Fish Proteins MeSH