title: Mechanism of Action of ME1111, a Novel Antifungal Agent for Topical Treatment of Onychomycosis.
abstract: Despite the existing treatment options for onychomycosis, there remains a strong demand for potent topical medications. ME1111 is a novel antifungal agent that is active against dermatophytes, has an excellent ability to penetrate human nails, and is being developed as a topical agent for onychomycosis. In the present study, we investigated its mechanism of action. Trichophyton mentagrophytes mutants with reduced susceptibility to ME1111 were selected in our laboratory, and genome sequences were determined for 3 resistant mutants. The inhibitory effect on a candidate target was evaluated by a spectrophotometric enzyme assay using mitochondrial fractions. Point mutations were introduced into candidate genes by a reverse genetics approach. Whole-genome analysis of the 3 selected mutants revealed point mutations in the structural regions of genes encoding subunits of succinate dehydrogenase (complex II). All of the laboratory-generated resistant mutants tested harbored a mutation in one of the subunits of succinate dehydrogenase (SdhB, SdhC, or SdhD). Most of the mutants showed cross-resistance to carboxin and boscalid, which are succinate dehydrogenase inhibitors. ME1111 strongly inhibited the succinate-2,6-dichlorophenolindophenol reductase reaction in Trichophyton rubrum and T. mentagrophytes (50% inhibitory concentrations [IC50s] of 0.029 and 0.025 μg/ml, respectively) but demonstrated only moderate inhibition of the same reaction in human cell lines. Furthermore, the target protein of ME1111 was confirmed by the introduction of point mutations causing the amino acid substitutions in SdhB, SdhC, and SdhD found in the laboratory-generated resistant mutants, which resulted in reduced susceptibility to ME1111. Thus, ME1111 is a novel inhibitor of the succinate dehydrogenase of Trichophyton species, and its mechanism of action indicates its selective profile.
authors.affiliation: Meiji Seika Pharma Co., Ltd., Tokyo, Japan shou.takahata@meiji.com.
authors.forename: Sho
authors.initials: S
authors.lastname: Takahata
authors.affiliation: Meiji Seika Pharma Co., Ltd., Tokyo, Japan.
authors.forename: Natsuki
authors.initials: N
authors.lastname: Kubota
authors.affiliation: Meiji Seika Pharma Co., Ltd., Tokyo, Japan.
authors.forename: Naomi
authors.initials: N
authors.lastname: Takei-Masuda
authors.affiliation: Teikyo University Institute of Medical Mycology, Tokyo, Japan.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Yamada
authors.affiliation: Teikyo University Institute of Medical Mycology, Tokyo, Japan.
authors.forename: Mari
authors.initials: M
authors.lastname: Maeda
authors.affiliation: Graduate School of Medicine, Teikyo University, Tokyo, Japan.
authors.forename: Mohamed Mahdi
authors.initials: MM
authors.lastname: Alshahni
authors.affiliation: Teikyo University Institute of Medical Mycology, Tokyo, Japan.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Abe
authors.affiliation: Meiji Seika Pharma Co., Ltd., Tokyo, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Tabata
authors.affiliation: Meiji Seika Pharma Co., Ltd., Tokyo, Japan.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Maebashi
mesh_terms: D000287:Administration, Topical; D019943:Amino Acid Substitution / Q000235:genetics; D000935:Antifungal Agents / Q000494:pharmacology*; D003883:Arthrodermataceae / Q000187:drug effects; D001483:Base Sequence; D002460:Cell Line; D004271:DNA, Fungal / Q000235:genetics; D025141:Drug Resistance, Fungal / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D014009:Onychomycosis / Q000188:drug therapy* / Q000382:microbiology; D010636:Phenols / Q000494:pharmacology*; D011720:Pyrazoles / Q000494:pharmacology*; D017422:Sequence Analysis, DNA; D013385:Succinate Dehydrogenase / Q000235:genetics*; D014249:Trichophyton / Q000187:drug effects* / Q000235:genetics*
chemical_list: C000611893:2-(3,5-dimethyl-1H-pyrazol-1-yl)-5-methylphenol; D000935:Antifungal Agents; D004271:DNA, Fungal; D010636:Phenols; D011720:Pyrazoles; C491545:SDHD protein, human; C108095:SDHB protein, human; D013385:Succinate Dehydrogenase