Synthesis and Activity Evaluation of Selenazole-Coupled CPI-1 Irreversible Bifunctional Inhibitors for Botulinum Toxin A Light Chain.

A series of novel conjugates of benzoselenazole or selenazole and CPI-1 were designed, synthesized, and evaluated for inhibitory activities against the botulinum neurotoxin A (BoNT/A) light chain (LC) and BoNT/A in vivo. The results show that these compounds exhibit potent inhibitory activities to the LC with IC50 of 0.5-4.1 mu M. The reaction kinetics and the mass spectra of the reaction products of LC with benzoselenazole- or selenazolecoupled CPI-1 demonstrate that the benzoselenazole group of most inhibitors is coupled to the LC of BoNT/A. These data indicate that the CPI-1 conjugates can inhibit both the active center of BoNT/A LC as well as Cys165, therefore functioning as irreversible bifunctional inhibitors. The detoxification activities in vivo show that one of the benzoselenazole-CPI-1 compounds prolongs the survival time of mice challenged by 2 x LD50 of BoNT/A. This work provides a new strategy to design potent antidotes of BoNT/A.