Title: Effect of seven newly synthesized and currently available oxime cholinesterase reactivators on cyclosarin-intoxicated rats Karasova JZ, Kassa J, Musilek K, Pohanka M, Novotny L, Kuca K Ref: Int J Mol Sci, 10:3065, 2009 : PubMed
Seven new oxime-based acetylcholinesterase reactivators were compared with three currently available ones (obidoxime, trimedoxime, HI-6) for their ability to lessen cholinesterase inhibition in blood and brain of cyclosarin-treated rats. Oximes were given at doses of 5% their LD(50) along with 21 mg/kg atropine five min before the LD(50) of cyclosarin (120 ug/kg) was administered. Blood and brain samples were collected 30 minutes later. The greatest difference between acetylcholinesterase inhibition in blood of cyclosarin-treated rats was found after administration of HI-6 (40%), compared to 22% for trimedoxime and 6% for obidoxime. Only two of the seven newly synthesized oximes had any effect (K203 at 7%, K156 at 5%). Effective oximes against cyclosarin-inhibited plasma butyrylcholinesterase were HI-6 (42%), trimedoxime (11%), and K156 (4%). The oximes were less effective in brain than in blood, with reactivation values for HI-6 30% against acetylcholinesterase and 10% against butyrylcholinesterase. Values for newly synthesized oximes were less than 10% for K206, K269 and K203.
        
Title: A comparison of reactivating and therapeutic efficacy of newly-developed oximes (K156, K203) and commonly used oximes (obidoxime, HI-6) in cyclosarin-poisoned rats and mice Kassa J, Karasova JZ, Musilek K, Kuca K Ref: Toxicol Mech Methods, 19:346, 2009 : PubMed
A potency of newly-developed oximes (K156, K203) and commonly used oximes (obidoxime, HI-6) to reactivate cyclosarin-inhibited acetylcholinesterase and to reduce cyclosarin-induced acute toxic effects was evaluated in this study. In vivo determined percentage of reactivation of cyclosarin-inhibited blood and tissue acetylcholinesterase in poisoned rats showed that the potency of a newly-developed oxime (K203) to reactivate cyclosarin-inhibited acetylcholinesterase and to reduce the acute lethal effects of cyclosarin, corresponding to the relatively low reactivating and therapeutic efficacy of obidoxime. The potency of another newly-developed oxime (K156) to counteract the inhibitory and acute clinical effects of cyclosarin is almost negligible. On the other hand, the oxime HI-6 is a very efficient reactivator of cyclosarin-inhibited acetylcholinesterase in the peripheral (blood, diaphragm) as well as central (brain) compartment, and it is able to reduce the acute toxicity of cyclosarin more than three times. Although the reactivating and therapeutic efficacy of the oxime K203 is higher compared to another newly-developed oxime K156, the reactivating and therapeutic potency of both newly-developed oximes is significantly lower in comparison with the oxime HI-6 and, therefore, none of them is suitable for replacement of HI-6 in the case of the treatment of cyclosarin poisoning.
        
Title: An evaluation of therapeutic and reactivating effects of newly developed oximes (K156, K203) and commonly used oximes (obidoxime, trimedoxime, HI-6) in tabun-poisoned rats and mice Kassa J, Karasova J, Musilek K, Kuca K Ref: Toxicology, 243:311, 2008 : PubMed
The potency of newly developed monoxime bispyridinium compounds (K156, K203) in reactivating tabun-inhibited acetylcholinesterase and reducing tabun-induced lethal toxic effects was compared with commonly used oximes (obidoxime, trimedoxime, the oxime HI-6) using in vivo methods. Studies determining percentage of reactivation of tabun-inhibited blood and tissue acetylcholinesterase in poisoned rats showed that the reactivating efficacy of newly developed oxime K203 is comparable with obidoxime and trimedoxime in blood and higher than the reactivating potency of trimedoxime and obidoxime in diaphragm and brain, where the difference in reactivating efficacy of obidoxime, trimedoxime and K203 is significant. On the other hand, the potency of newly developed K156 to reactivate tabun-inhibited acetylcholinesterase is comparable with obidoxime or trimedoxime in diaphragm and brain. It is significantly lower than the reactivating efficacy of trimedoxime and obidoxime in blood. Moreover, both newly developed oximes were found to be relatively efficacious in the reduction of lethal toxic effects in tabun-poisoned mice. Especially, the oxime K203 is able to decrease the acute toxicity of tabun nearly two times. The therapeutic efficacy of K156 and K203 corresponds to their potency to reactivate tabun-inhibited acetylcholinesterase, especially in diaphragm and brain. In contrast to obidoxime and trimedoxime, the oxime HI-6 is not effective in reactivation of tabun-inhibited acetycholinesterase and in reducing tabun lethality. While the oxime K156 does not improve the reactivating and therapeutic effectiveness of currently available obidoxime and trimedoxime, the newly developed oxime K203 is markedly more effective in reactivation of tabun-inhibited acetylcholinesterase in rats, especially in brain, and in reducing lethal toxic effects of tabun in mice and, therefore, it is suitable for the replacement of commonly used oximes for the antidotal treatment of acute tabun poisoning.