Discovery of Dipeptides as Potent Botulinum Neurotoxin A Light-Chain Inhibitors

The botulinum neurotoxin, the caustic agent that causes botulism, is the most lethal toxin known to man. The neurotoxin composed of a heavy chain (HC) and a light chain (LC) enters neurons and cleaves SNARE proteins, leading to flaccid paralysis, which, in severe occurrences, can result in death. A therapeutic target for botulinum neurotoxin (BoNT) intoxication is the LC, a zinc metalloprotease that directly cleaves SNARE proteins. Herein we report dipeptides containing an aromatic connected to the N-terminus via a sulfonamide and a hydroxamic acid at the C-terminus as BoNT/A LC inhibitors. On the basis of a structure-activity relationship study, 33 was discovered to inhibit the BoNT/A LC with an IC₅₀ of 21 nM. X-ray crystallography analysis of 30 and 33 revealed that the dipeptides inhibit through a competitive mechanism and identified several key intermolecular interactions.

Synthesis and activity of isoleucine sulfonamide derivatives as novel botulinum neurotoxin serotype A light chain inhibitors

The botulinum neurotoxin (BoNT) is the most lethal protein known to man causing the deadly disease botulinum. The neurotoxin, composed of a heavy (HC) and light (LC) chain, work in concert to cause muscle paralysis. A therapeutic strategy to treat individuals infected with the neurotoxin is inhibiting the catalytic activity of the BoNT LC. We report the synthesis, inhibition study and computational docking analysis of novel small molecule BoNT/A LC inhibitors. A structure activity relationship study resulted in the discovery of d-isoleucine functionalized with a hydroxamic acid on the C-terminal and a biphenyl with chlorine at C- 2 connected by a sulfonamide linker at the N-terminus. This compound has a measured IC₅₀ of 0.587 µM for the BoNT/A LC. Computational docking analysis indicates the sulfonamide linker adopts a geometry that is advantageous for binding to the BoNT LC active site. In addition, Arg363 is predicted to be involved in key binding interactions with the scaffold in this study.