Analysis of botulinum neurotoxin serotype A metalloprotease inhibitors: analogs of a chemotype for therapeutic development in the context of a three-zone pharmacophore
James C Burnett1, Bing Li2, Ramdas Pai2, Steven C Cardinale2, Michelle M Butler2, Norton P Peet2, Donald Moir2, Sina Bavari3, Terry Bowlin2
1Target, Structure-Based Drug Discovery Group, SAIC-Frederick, Inc., National Cancer Institute at Frederick; Frederick, MD 21702, USA; 2Microbiotix, Inc., Worcester, MA 01605, USA; 3Division of Integrated Toxicology, United States Army Medical Research Institute of Infectious Diseases, Frederick, MD 21702, USA
Abstract: Botulinum neurotoxins (BoNTs), and in particular serotype A, are the most poisonous of known biological substances, and are responsible for the flaccid paralysis of the disease state botulism. Because of the extreme toxicity of these enzymes, BoNTs are considered highest priority biothreat agents. To counter BoNT serotype A (BoNT/A) poisoning, the discovery and development of small molecule, drug like inhibitors as post intoxication therapeutic agents is being pursued. Specifically, we are focusing on inhibitors of the BoNT/A light chain (LC) (ie, a metalloprotease) subunit, since such compounds can enter neurons and provide post intoxication protection of the enzyme target substrate. To aid/facilitate this drug development effort, a pharmacophore for inhibition of the BoNT/A LC subunit was previously developed, and is continually being refined via the incorporation of novel and diverse inhibitor chemotypes. Here, we describe several analogs of a promising therapeutic chemotype in the context of the pharmacophore for BoNT/A LC inhibition. Specifically, we describe: 1) the pharmacophoric ‘fits’ of the analogs and how these ‘fits’ rationalize the in vitro inhibitory potencies of the analogs, and 2) pharmacophore refinement via the inclusion of new components from the most potent of the presented analogs.
Keywords: botulinum, neurotoxin, inhibitor, pharmacophore, metalloprotease, biothreat
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