Investigation of Novel Chemical Antidotes for Organophosphate Poisoning: Design, Synthesis, and Evaluation

Organophosphate (OP) compounds are extensively employed as agricultural pesticides and have also been developed as chemical warfare nerve agents, posing a significant threat to human health due to their potent neurotoxicity. These compounds exert their toxic effects primarily by irreversibly inhibiting acetylcholinesterase (AChE), resulting in the excessive accumulation of acetylcholine at cholinergic synapses and subsequent overstimulation of muscarinic and nicotinic receptors. Clinically, this manifests as acute cholinergic crisis, respiratory failure, seizures, and, if untreated, death. Although current therapeutic regimens involve the combined administration of antimuscarinic agents, such as atropine, and oxime-based AChE reactivators, including pralidoxime (2-PAM) and obidoxime, these antidotes exhibit several critical limitations. These include suboptimal blood–brain barrier penetration, insufficient reactivation of aged OP–AChE complexes, variable efficacy against different OP agents, and dose-related adverse effects. The present study focuses on the rational design, chemical synthesis, and comprehensive pharmacological evaluation of novel chemical antidotes for OP poisoning, with particular emphasis on next-generation oxime-based reactivators and multifunctional hybrid molecules. Structural modifications were guided by molecular modeling and structure–activity relationship considerations to enhance nucleophilicity, lipophilicity, and central nervous system accessibility. The synthesized compounds were thoroughly characterized using physicochemical and spectroscopic techniques, including nuclear magnetic resonance (NMR), infrared (IR) spectroscopy, and mass spectrometry. In vitro enzymatic assays were employed to assess AChE inhibition reversal and reactivation kinetics against representative OP agents, while cytotoxicity and preliminary safety profiles were evaluated using relevant biological models.