Reactivation of organophosphate-inhibited human, Cynomolgus monkey, swine and guinea pig acetylcholinesterase by MMB-4: a modified kinetic approach.
Treatment of poisoning by highly toxic organophosphorus compounds (OP, nerve agents) is a continuous challenge. Standard treatment with atropine and a clinically used oxime, obidoxime or pralidoxime is inadequate against various nerve agents. For ethical reasons testing of oxime efficacy has to be performed in animals. Now, it was tempting to investigate the reactivation kinetics of MMB-4, a candidate oxime to replace pralidoxime, with nerve agent-inhibited acetylcholinesterase (AChE) from human and animal origin in order to provide a kinetic basis for the proper assessment of in vivo data. By applying a modified kinetic approach, allowing the use of necessary high MMB-4 concentrations, it was possible to determine the reactivation constants with sarin-, cyclosarin-, VX-, VR- and tabun-inhibited AChE. MMB-4 exhibited a high reactivity and low affinity towards OP-inhibited AChE, except of tabun-inhibited enzyme where MMB-4 had an extremely low reactivity. Species differences between human and animal AChE were low (Cynomolgus) to moderate (swine, guinea pig). Due to the high reactivity of MMB-4 a rapid reactivation of inhibited AChE can be anticipated at adequate oxime concentrations which are substantially higher compared to HI-6. Additional studies are necessary to determine the in vivo toxicity, tolerability and pharmacokinetics of MMB-4 in humans in order to enable a proper assessment of the value of this oxime as an antidote against nerve agent poisoning.
Worek
Franz
F
Bundeswehr Institute of Pharmacology and Toxicology, Neuherbergstrasse 11, 80937 Munich, Germany. franzworek@bundeswehr.org
Wille
Timo
T
Aurbek
Nadine
N
Eyer
Peter
P
Thiermann
Horst
H
D000110:Acetylcholinesterase; D000818:Animals; D002619:Chemical Warfare Agents / Q000633:toxicity; D002800:Cholinesterase Inhibitors / Q000633:toxicity*; D002801:Cholinesterase Reactivators / Q000494:pharmacology*; D006168:Guinea Pigs; D006801:Humans; D008252:Macaca fascicularis; D009943:Organophosphorus Compounds / Q000633:toxicity*; D010091:Oximes / Q000494:pharmacology*; D013552:Swine
D002619:Chemical Warfare Agents; D002800:Cholinesterase Inhibitors; D002801:Cholinesterase Reactivators; D009943:Organophosphorus Compounds; D010091:Oximes; C005514:N,N'-monomethylenebis(pyridiniumaldoxime); D000110:Acetylcholinesterase