A Refined Pharmacophore Identifies Potent 4-Amino-7-chloroquinoline-Based Inhibitors of the Botulinum Neurotoxin Serotype A Metalloprotease

Abstract

We previously identified structurally diverse small molecule (non-peptidic) inhibitors (SMNPIs) of the botulinum neurotoxin serotype A (BoNT/A) light chain (LC). Of these, several (including antimalarial drugs) contained a 4-amino-7-chloroquinoline (ACQ) substructure and a separate positive ionizable amine component. The same antimalarials have also been found to interfere with BoNT/A translocation into neurons, via pH elevation of the toxin-mediated endosome. Thus, this structural class of small molecules may serve as dualfunction BoNT/A inhibitors. In this study, we used a refined pharmacophore for BoNT/A LC inhibition to identify four new, potent inhibitors of this structural class (IC 50 's ranged from 3.2 to 17 µM). Molecular docking indicated that the binding modes for the new SMNPIs are consistent with those of other inhibitors that we have identified, further supporting our structure-based pharmacophore. Finally, structural motifs of the new SMNPIs, as well as two structure-based derivatives, were examined for activity, providing valuable information about pharmacophore component contributions to inhibition.

Three‐Dimensional Database Mining Identifies a Unique Chemotype that Unites Structurally Diverse Botulinum Neurotoxin Serotype A Inhibitors in a Three‐Zone Pharmacophore

“…This is evidenced by the fact that only a handful of small molecules with IC 50 and/or K i values < 15 mm are described in the literature. [28,29,[32][33][34][35][36][37][38] Among these, only one compound, Zn coordinating o,p-(dichloro)-cinnamic hydroxamate (o,p-DCH), is reported to possess an inhibition constant lower than 0.5 mm (IC 50 = 0.41 mm); however, when examined in our HPLC-based assay, o,p-DCH was found to be significantly less potent, with an IC 50 value of > 29 mm, [28] and in a subsequent publication [37] it was shown to be toxic to neurons and demonstrated poor in vivo protection.…”

“…[28][29][30][31] In this study, we describe how an SMNPI that is active in neurons was used to generate a three-dimensional (3D) search query that identified a rigid diazaA C H T U N G T R E N N U N G chrysene-based inhibitor, and how the steric limitations imposed by this scaffold provided the basis for the evolution of a refined, three-zone (3-zone) pharmaA C H T U N G T R E N N U N G cophore model for BoNT/A LC inhibition. Finally, we describe how the addition of a third zone facilitated the discovery of a novel compound that represents a distinct A C H T U N G T R E N N U N G structural class of SMNPI.…”

The Strange Case of the Botulinum Neurotoxin: Using Chemistry and Biology to Modulate the Most Deadly Poison

“…[132] Four inhibitors were identified (Scheme 9) from the refined, eight-component pharmacophore model for in vitro testing with LC/A, and were synthesized. [134] All four compounds exhibited IC 50 values in the low micromolar range (3-17 mm). The unique aspect of three of the novel inhibitors was the incorporation of an additional recognition motif in a steroidal region to act as a hydrophobic anchor at the edge of the binding cleft.…”

Der seltsame Fall des Botulinum‐Neurotoxins: chemische und biologische Modulierung des tödlichsten aller Gifte

“…[132] Die Studie basierte auf einer Kristallstruktur der LC/A, [133] [132] Unter Verwendung des verfeinerten AchtkomponentenPharmakophormodells konnten vier Inhibitoren für In-vitroUntersuchungen mit LC/A identifiziert (Schema 9) und synthetisiert werden, [134] einen Calciuminflux zu induzieren und damit einen Acetylcholinefflux aus der Zelle zu verursachen. Solche Substanzen könnten insbesondere in der Lage sein, BoNT-induzierte Lähmungen rückgängig zu machen.…”