Identification of 1,2,3-triazolium salt-based inhibitors of Leishmania infantum trypanothione disulfide reductase with enhanced antileishmanial potency in cellulo and increased selectivity

N -methylation of the triazole moiety present in our recently described triazole-phenyl-thiazole dimerization disruptors of Leishmania infantum trypanothione disulfide reductase ( Li TryR) led to a new class of potent inhibitors that target different binding sites on this enzyme. Subtle structural changes among representative library members modified their mechanism of action, switching from models of classical competitive inhibition to time-dependent mixed noncompetitive inhibition. X-ray crystallography and molecular modeling results provided a rationale for this distinct behavior. The remarkable potency and selectivity improvements, particularly against intracellular amastigotes, of the Li TryR dimerization disruptors 4c and 4d reveal that they could be exploited as leishmanicidal agents. Of note, L. infantum promastigotes treated with 4c significantly reduced their low-molecular-weight thiol content, thus providing additional evidence that Li TryR is the main target of this novel compound. • N -methylation of triazole-based TryR disruptors alters their inhibitory mechanism. • Binding of competitive inhibitors to TryR is characterized by X-ray crystallography. • Computational studies locate TryR dimerization disruptors in the interfacial cavity. • TryR dimerization disruptors potently and selectively kill intracellular amastigotes. • 4c diminishes the low-molecular-weight thiol content in L. infantum parasites.