Hit Optimization Of A Trypanosoma Cruzi Bromodomain Inhibitor Identified Using Combinatorial Chemistry

Abstract

Recently, our group has used Dynamic Combinatorial Chemistry targeting the Trypanosoma cruzi Bromodomain factor 3 (BDF3), as a strategy for the identification of a parasite inhibitor, this hit is an acylhydrazone with a Kd of 1.7 µM and and IC50 for epimastigotes, amastigotes and trypomastigotes between 13 and 23 µM. TcBDF3 interacts with acetylated alpha-tubulin present in the cytoskeleton and flagella of T. cruzi and is essential for the viability. TcBDF3 is an interesting target for the development of new trypanocidal drugs that disrupt the bromodomain-acetylated ligand interaction during the parasite differentiation. There are six other proteins with bromodomain in T. cruzi, among which TcBDF2 has also been shown to be essential for the parasite. Today it is a challenge to find selective inhibitors that can distinguish between the different bromodomains, and are more effective and less toxic than the trypanocidal drugs currently use. We prepare a small library of acylhydrazones synthesized from an acylhydrazide nucleus and various aldehydes selected according to the hit previously described by our group for TcBDF3, with the goal of finding more potent and selective inhibitors against TcBDF2 and TcBDF3. The interaction of each hydrazone with TcBDF2 and TcBDF3 from T. cruzi was determined by microplate protein fluorescence quenching assays and Thermal Shift. The results obtained so far allow us to conclude that i) all synthesized hydrazones interact with the hydrophobic pocket of TcBDF3, ii) none of them interact with TcBDF2 up to the highest concentration tested (20 µM), iii) two of the synthesized hydrazones are attractive due to its affinity to TcBDF3 and iv) only one of these hydrazones inhibits the development of epimastigotes of T. cruzi (IC50 <10 µM).