The Tetrazole VT-1161 Is a Potent Inhibitor of Trichophyton rubrum through Its Inhibition of T. rubrum CYP51

Abstract

Prior to characterization of antifungal inhibitors that target CYP51, Trichophyton rubrum CYP51 was expressed in Escherichia coli, purified, and characterized. T. rubrum CYP51 bound lanosterol, obtusifoliol, and eburicol with similar affinities (dissociation constant [K d ] values, 22.7, 20.3, and 20.9 M, respectively) but displayed substrate specificity, insofar as only eburicol was demethylated in CYP51 reconstitution assays (turnover number, 1.55 min Ϫ1 ; K m value, 2 M). The investigational agent VT-1161 bound tightly to T. rubrum CYP51 (K d ϭ 242 nM) with an affinity similar to that of clotrimazole, fluconazole, ketoconazole, and voriconazole (K d values, 179, 173, 312, and 304 nM, respectively) and with an affinity lower than that of itraconazole (K d ϭ 53 nM). Determinations of 50% inhibitory concentrations (IC 50 s) using 0.5 M CYP51 showed that VT-1161 was a tight-binding inhibitor of T. rubrum CYP51 activity, yielding an IC 50 of 0.14 M, whereas itraconazole, fluconazole, and ketoconazole had IC 50 s of 0.26, 0.4, and 0.6 M, respectively. When the activity of VT-1161 was tested against 34 clinical isolates, VT-1161 was a potent inhibitor of T. rubrum growth, with MIC 50 , MIC 90 , and geometric mean MIC values of Յ0.03, 0.06, and 0.033 g ml Ϫ1 , respectively. With its selectivity versus human CYP51 and drugmetabolizing cytochrome P450s having already been established, VT-1161 should prove to be safe and effective in combating T. rubrum infections in patients.

Azole Resistance Reduces Susceptibility to the Tetrazole Antifungal VT-1161

“…The structurally related compounds VT-1161 and VT-1129 have been proposed as antifungal agents that effectively target the LDMs of several fungal pathogens, ranging from Ascomycetes and Basidiomycetes to Zygomycetes (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12). These drugs use the weaker affinity for the heme iron conferred by a tetrazole instead of a triazole, together with additional contacts within the LBP, to bind preferentially with their fungal target and minimize interaction with human cytochrome P450s (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)40). We have used a yeast expression system and clinical isolates of the fungal pathogens C. albicans and C. glabrata to demonstrate that the efficacy of this new class of azole drugs can be compromised by mechanisms of antifungal resistance common in these organisms.…”

Amino acid–derived defense metabolites from plants: A potential source to facilitate novel antimicrobial development

“…The bioactive compounds erchinine A and B contain a unique 1,4-diazepine structure joined to an oxazolidine and showed activities against the fungus T. rubrum comparable with the standard antifungal drug griseofulvin, whereas the inhibitory effect on the bacterium B. subtilis was comparable with that of the antibiotic cefotaxime ( 229 ). Although T. rubrum is generally non-life threatening, chronic T. rubrum infections facilitate secondary fungal infections, which can become lethal when systemic ( 230 , 231 ). Although the mechanisms of action are not yet understood, erchinine A and B are promising for the development of novel antifungal leads.…”

The Fungal CYP51s: Their Functions, Structures, Related Drug Resistance, and Inhibitors

“…The MIC 50 of VT-1161 against fluconazole-resistant C. albicans is 0.03 μg/ml (Break et al, 2018b). For T. rubrum CYP51 proteins, The K d and IC 50 values are 242 nM and 0.14 μM, respectively (Warrilow et al, 2017). Its non-selective inhibition of human CYP450 is also weak, appears in its IC 50 of CYP2C9, CYP2C19 and CYP3A4 are 99, 72, and 65 μM.…”