Design of 1,2,3-triazoles as inhibitors of Cruzipain (CZP): Target validation, in silico modeling and vHTS screening

RIBONE, S.R.; QUEVEDO, M.A.; OPSOMER, T.; CERUTTI, JUAN PABLO; DEHAEN, W.

Salta

Workshop; 1st Workshop on Drug Discovery; 2019

Chagas disease constitutes a relevant public health issue throughout the world. Unfortunately, limited pharmacological options are available for its treatment, with only two drugs currently approved (i.e. benznidazole (BZN) and nifurtimox (NFX)). Both, BZN and NFX, exhibit important side effects, thus the development of new antichagasic agents constitutes an urgent need. Different druggable targets have been identified for the development of therapeutically useful antichagasic compounds. Among them, cruzipain (CZP) has been actively studied, with its modulation being possible by both reversible and irreversible inhibitors. The latter ones have gained significant interest due to their potential of eliciting high inhibitory potencies. Structurally, CZP belongs to cysteine proteases family, bearing a catalytically active cysteine (CYS25) residue required for its proteolytic activity. Also, at least three subdomains (S1-S3) have been identified within its catalytic site. The rational design of CZP inhibitors is focused towards the obtention of molecules able to bind to this catalytic site with high affinity and selectivity. Derivatives of 1,2,3-triazoles constitute very promising compounds for the design of CZP irreversible inhibitors due to its bioisosteric relationship with the peptidic bond. Noteworthy, the chemical space accessible for the preparation of 1,2,3-triazole derivatives is huge, representing both an opportunity for the design of bioactive molecules, but also signifying a challenge regarding the requirements for the screening of candidates. Thus, the development and validation of an in silico screening platform constitutes an important requirement.In this work, we present an in silico workflow designed for the preparation and validation of a CZP receptor model based on available crystallographic structures, followed by automated procedures for ligand modeling, molecular docking, molecular dynamics and free-energy of interaction analyses, with the aim of providing a platform able to describe the recognition and binding mode of 1,2,3-triazole derivatives to CZP. A set of 20 previously reported 1,2,3-triazole derived irreversible inhibitors (IC50: 5-23000 nM) was used as training set, with the corresponding structure-activity relationships being established. The workflow led to identification of key pharmacophoric contacts driving inhibitors binding, elucidating also the structural basis for the observed ligand enantioselectivity. The methodology was afterwards extended to the vHTS of a library containing above 100K 1,2,3-triazoles derivatives, which was virtually constructed based on commercially available regents and feasible synthetic procedures. Overall, the presented methodology constitutes a valuable vHTS platform for the automated screening of large 1,2,3-triazoles databases, constituting a valuable structure-guided aid to our ongoing synthetic efforts towards the obtention of new antichagasic agents.