Small molecule inhibitors of anthrax edema factor.

Anthrax is a highly lethal disease caused by the Gram-(+) bacteria Bacillus anthracis. Edema toxin (ET) is a major contributor to the pathogenesis of disease in humans exposed to B. anthracis. ET is a bipartite toxin composed of two proteins secreted by the vegetative bacteria, edema factor (EF) and protective antigen (PA). Our work towards identifying a small molecule inhibitor of anthrax edema factor is the subject of this letter. First we demonstrate that the small molecule probe 5'-Fluorosulfonylbenzoyl 5'-adenosine (FSBA) reacts irreversibly with EF and blocks enzymatic activity. We then show that the adenosine portion of FSBA can be replaced to provide more drug-like molecules which are up to 1000-fold more potent against EF relative to FSBA, display low cross reactivity when tested against a panel of kinases, and are nanomolar inhibitors of EF in a cell-based assay of cAMP production.

Virtual medicinal chemistry: in silico pre-docking functional group transformation for discovery of novel inhibitors of botulinum toxin serotype A light chain.

A novel method for applying high-throughput docking to challenging metalloenzyme targets is described. The method utilizes information-based virtual transformation of library carboxylates to hydroxamic acids prior to docking, followed by compound acquisition, one-pot (two steps) chemical synthesis and in vitro screening. In two experiments targeting the botulinum neurotoxin serotype A metalloprotease light chain, hit rates of 32% and 18% were observed.

Antidotes to anthrax lethal factor intoxication. Part 3: Evaluation of core structures and further modifications to the C2-side chain.

Four core structures capable of providing sub-nanomolar inhibitors of anthrax lethal factor (LF) were evaluated by comparing the potential for toxicity, physicochemical properties, in vitro ADME profiles, and relative efficacy in a rat lethal toxin (LT) model of LF intoxication. Poor efficacy in the rat LT model exhibited by the phenoxyacetic acid series (3) correlated with low rat microsome and plasma stability. Specific molecular interactions contributing to the high affinity of inhibitors with a secondary amine in the C2-side chain were revealed by X-ray crystallography.

Antidotes to anthrax lethal factor intoxication. Part 2: structural modifications leading to improved in vivo efficacy.

New anthrax lethal factor inhibitors (LFIs) were designed based upon previously identified potent inhibitors 1a and 2. Combining the new core structures with modifications to the C2-side chain yielded analogs with improved efficacy in the rat lethal toxin model.

Antidotes to anthrax lethal factor intoxication. Part 1: Discovery of potent lethal factor inhibitors with in vivo efficacy.

Sub-nanomolar small molecule inhibitors of anthrax lethal factor have been identified using SAR and Merck L915 (4) as a model compound. One of these compounds (16) provided 100% protection in a rat lethal toxin model of anthrax disease.