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Cruzain Inhibitors for Chagas Disease: Anticorrelated Optimisation Landscapes and the Multiparametric Path to Clinical Candidates

Dos Reis CRC, de Souza HVCM, Parra LC, de Souza GVCM, Zorzanelli BC, Boechat N, Hoelz LVB, Fernandes TVA

Chemical biology & drug design, 2026

Abstract

Over three decades, cruzain, the principal cysteine protease of Trypanosoma cruzi and a validated drug target for Chagas disease, has accumulated 215 inhibitors with IC50 ≤ 1 μM, more than 30 crystal structures, and no clinical candidates. This review argues that the resulting translational paradox reflects not target invalidity, but a persistent strategic mismatch between how cruzain inhibitors have been optimised and what intracellular efficacy requires. Across peptidyl vinyl sulfones, non-peptidic scaffolds, and thiosemicarbazones, enzymatic potency has been systematically prioritised over the coupled determinants of intracellular exposure: permeability, metabolic stability, and cathepsin selectivity. Each inhibitor class fails for a distinct proximal reason, and these failures converge on the same optimisation bias. Computational approaches (docking, molecular dynamics, free-energy perturbation and machine-learning QSAR) have been applied with increasing sophistication, but against affinity-centred objectives that underrepresent exposure constraints. As its principal contribution, this work proposes a multiparametric optimisation framework, provisional viability benchmarks, and a feasibility-envelope concept that reframes cruzain inhibitor discovery as a constraint-satisfaction rather than a potency-maximisation problem. The framework outlines provisional quantitative criteria that a next-generation cruzain lead would likely need to satisfy and explains why structurally…

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Evidence Hub reads this as a review, done in computer models (in silico), not in people. Its evidence level is 5 of 5 (Very low · case / narrative / animal / in vitro / in silico). Case reports, narrative reviews, and animal, cell or computer-model studies give the weakest evidence for human health.

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