Development and experimental validation of a docking model to identify novel T. cruzi carbonic anhydrase inhibitors with potential antichagasic activity

LLANOS MANUEL; SBARAGLINI MARÍA L; VILLALBA MARÍA L. ; MARÍA L. VILLALBA; TALEVI ALAN; SUPURÁN CLAUDIU T.; GAVERNET LUCIANA

Buenos Aires

Congreso; DRUG DISCOVERY FOR NEGLECTED DISEASES INTERNATIONAL CONGRESS 2018; 2018

/ Instituto de la Química y Metabolismo del Fármaco FFyB UBA

the last few years, T. cruzi Carbonic Anhydrase (TcCA) has emerged as a promising target to derive novel therapeutic opportunities against Chagas disease [1]. Nonetheless, carbonic anhydrases belong to a huge enzyme family widely expressed in mammals. Thus, in the subtle structural differences between the parasite and the human isoforms lies the key to develop selective compounds with improved therapeutic properties.Because the crystal structure of TcCA hasn?t been solved so far, we have created a multi-template homology model of the enzyme. This structural model was refined combining Rosetta?s Relax algorithm with all-atoms molecular dynamics to explore the conformational space around the initial model. Ten representative snapshots were extracted from the simulation by clustering analysis and used to develop a docking model of the target. A validation set of 68 molecules and its inhibition constants was compiled from literature and used to assess the scoring power of the model.Additionally, molecules within the validation set were classified either as actives or inactives, considering a threshold value of 1 μM. Docking this set on every protein structure allowed us to identify the best docking model, which showed a good classification performance evaluated by means of ROC curves (AUC-ROC=0.93).After applying the final model to screen an in-house compiled library of compounds either acquired or synthesized in our laboratory, some interesting hits containing either sulfamide or sulfamate moieties were selected for in vitro evaluation. 10 compounds were evaluated in the enzyme inhibition assay, and 8 of them showed activities in the low micromolar range. Sodium Cyclamate (SC), a widely used non-caloric sweetener, showed a Ki of 0.35 μM against TcCA.In the non-infective form of the parasite, SC reduced epimastigote proliferation by 22% (50 μM, strain Y), whereas it reduced trypomastigote viability by 48% (20 μM, strain RA).We have developed and properly validated a docking model of TcCA which allowed us to identify potential antichagasic compounds acting as carbonic anhydrase inhibitors. All tested compounds have previously shown to be inactive againstthe ubiquitously expressed human carbonic anhydrases I and II, being highly selective towards TcCA. We are currently running molecular dynamics simulations of TcCA with some of the identified hits, to shed light on the key molecularinteractions responsible for the activity. These results will allow us to maximize these important interactions, as a part of the hit optimization process.