Inhibition in vivo of the activity of botulinum neurotoxin A by small molecules selected by virtual screening

• Published in: Toxicon (Oxford) 2012-11, Vol.60 (6), p.1180-1190
• Main Authors: Eichhorn, Tolga, Dolimbek, Behzod Z., Deeg, Katharina, Efferth, Thomas, Atassi, M. Zouhair
• Format: Article
• Language: English
• Subjects: Animal poisons toxicology. Antivenoms; Animals; Bacteriology; Biological and medical sciences; Botulinum neurotoxin A; botulinum toxin; Botulinum Toxins, Type A - antagonists & inhibitors; Botulinum Toxins, Type A - chemistry; Computational Biology; computer software; Fundamental and applied biological sciences. Psychology; intravenous injection; In vivo activity; lethal dose; Medical sciences; Mice; Microbiology; molecular weight; mortality; Mouse protection assay; Neurotoxins - antagonists & inhibitors; Neurotoxins - chemistry; Pathogenicity, virulence, toxins, bacteriocins, pyrogens, host-bacteria relations, miscellaneous strains; Protective Agents - chemistry; Protein Conformation; screening; Sequence Alignment; Small molecule inhibitors; Software; Toxicology; Virtual screening
• ISSN: 0041-0101; 1879-3150
• DOI: 10.1016/j.toxicon.2012.07.010

To search for small molecular size inhibitors of botulinum neurotoxin A (BoNT/A) endopeptidase activity, we have screened the NCI library containing about 1 million structures against the substrate binding pocket of BoNT/A. Virtual screening (VS) was performed with the software Glide (Grid-based ligand docking energetics) and the findings were confirmed by AutoDock. Ten compounds were found that had favorable energetic and glide criteria and 5 of these compounds were selected for their ability to protect mice in vivo against a lethal dose of BoNT/A. Each compound was incubated at different molar excesses with a lethal dose of the toxin and then the mixture injected intravenously into mice. At 4690 M excess, compounds NSC94520 and NSC99639 protected all (100%) the mice from lethal toxicity. Compounds NSC48461 and NSC627733 gave 75% protection. Compound NSC348884 showed the least inhibition of toxicity allowing only a fraction (25%) of the mice to survive challenge with a lethal dose; and in the case of the mice that did not survive there was a considerable delay of mortality. At 2400 M excess compounds NSC94520 remained fully protective while and NSC99639 afforded 75% protection and at 1200 M excess each of these two compounds gave 50% protection. The two compounds gave no protection at 600 or less molar excess. When each compound was administered intravenously at 4690 M excess at different times (from 1 h to 6 h) after the intravenous injection of the active toxin, none of the compounds was able to protect the animals from toxicity. The findings show the value of VS in identifying potential inhibitors of the toxin for further development and improvement. ► We did virtual screening of about 1 million compounds vs BoNT/A substrate binding pocket. ► Five compounds that had favorable fit were tested in a mouse protection assay. ► Two compounds bound into the binding site, protected all mice from lethal toxicity. ► Two compounds protected 75%, and one 25%, of the mice against a lethal toxin dose. ► Virtual screening helps to identify likely toxin inhibitors for more improvement.