Structure-based drug design of multi-targeting inhibitors of human pathogen fungi

The development of multi-targeting inhibitors is proposed to improve the antifungal effect. In a single chemical entity it is possible to inhibit two different targets. Thioredoxin reductase and glutathione reductase belong to the two main systems responsible for the maintenance of cell homeostasis. Herein, we describe the discovery and selection of dual-inhibitors targeting thioredoxin reductase and glutathione reductase proteins of Aspergillus fumigatus. Both proteins were modeled and molecular dynamics were performed to obtain different conformational frames to ensemble docking. After the independent virtual screening of each protein, a ranking containing molecules selected for both proteins were generated. Fourteen molecules were tested in vitro against A. fumigatus, Fusarium oxysporum, Paracoccidioides brasiliensis, Candida albicans and Cryptococcus neoformans by broth microdilution assay. Octenidine (OCT) was the most promising molecule which exhibited MIC < 0.5 µg/mL for all fungi tested. The literature describes the action of OCT in the cell membrane of gram-negative bacteria. Thus, we assume that the mechanism in which OCT acts on fungal cells is an association of disrupting the cell membrane and also the dual-inhibition of thioredoxin reductase and glutathione reductase which implies the increase of ROS and further fungal cell death.