Synthesis/biological evaluation of hydroxamic acids and their prodrugs as inhibitors for Botulinum neurotoxin A light chain

Abstract

Botulinum neurotoxin A (BoNT/A) is the most potent toxin known. Unfortunately, it is also a potential bioweapon in terrorism, which is without an approved therapeutic treatment once cellular intoxication takes place. Previously, we reported how hydroxamic acid prodrug carbamates increased cellular uptake, which translated to successful inhibition of this neurotoxin. Building upon this research, we detail BoNT/A protease molecular modeling studies accompanied by the construction of small library of hydroxamic acids based on 2,4-dichlorocinnamic hydroxamic acid scaffold and their carbamate prodrug derivatization along with the evaluation of these molecules in both enzymatic and cellular models.

Design, synthesis, and biological evaluation of dual targeting inhibitors of histone deacetylase 6/8 and bromodomain BRPF1

“…To achieve that, we masked the hydroxamic acid functionality in 23a and 44b by synthesizing the corresponding benzyl and para-acetoxy-benzyl ester prodrugs of hydroxamic acids 59a,b and 60b (Figure 12) as prodrugs. Masking hydroxamic acids was recently reported as an approach to overcome problems like fast elimination, decreased cellular uptake and poor tissue penetration caused by the highly polar hydroxamic acid group [85][86][87][88][89][90]. In addition, paraacetoxybenzyl-based prodrugs were shown to be completely converted to the parent hydroxamic acid in plasma [91].…”

Cellular Protection of SNAP-25 against Botulinum Neurotoxin/A: Inhibition of Thioredoxin Reductase through a Suicide Substrate Mechanism

“…Although we previously obtained some success using a prodrug approach, leveraged through carbamate-protected hydroxamic acids, to counteract BoNT/A LC in the cell, we also noted that this design strategy still needed improvement. (15) As an alternative means to enhance the potency of LC inhibitors, we turned our attention to Cys165, which is embedded within the active site of the BoNT/LC (highlighted with yellow in the crystal structure, Figure 1). (16) Moreover, Dive and co-workers reported that when this Cys residue was covalently modified, catalysis was stopped and the enzyme was inactivated.…”

Catch and Anchor Approach To Combat Both Toxicity and Longevity of Botulinum Toxin A

“…Extensive efforts over the last 2 decades have produced several in vitro and in vivo inhibitors of BoNT/A LC translocation and enzyme activity . The most potent class of BoNT/A inhibitors remains zinc-chelating molecules, particularly those inclusive of a hydroxamic acid pharmacophore. − Zinc-chelating inhibitors bind competitively at the BoNT/A active site, directly preventing the association of the substrate with the enzyme catalytic site. While best-in-class reversible inhibitors have achieved sub-micromolar potency and modest protection against BoNT/A challenge in murine models, no drug candidate has reached clinical trials.…”