Amino Acid-Derived 1,2-Benzisothiazolinone Derivatives as Novel Small-Molecule Antifungal Inhibitors: Identification of Potential Genetic Targets

Abstract

ABSTRACTWe have identified four synthetic compounds (DFD-VI-15, BD-I-186, DFD-V-49, and DFD-V-66) from an amino acid-derived 1,2-benzisothiazolinone (BZT) scaffold that have reasonable MIC50values against a panel of fungal pathogens. These compounds have no structural similarity to existing antifungal drugs. Three of the four compounds have fungicidal activity againstCandidaspp.,Cryptococcus neoformans, and several dermatophytes, while one is fungicidal toAspergillus fumigatus. The kill rates of our compounds are equal to those in clinical usage. The BZT compounds remain active against azole-, polyene-, and micafungin-resistant strains ofCandidaspp. A genetics-based approach, along with phenotype analysis, was used to begin mode of action (MOA) studies of one of these compounds, DFD-VI-15. The genetics-based screen utilized a homozygous deletion collection of approximately 4,700Saccharomyces cerevisiaemutants. We identified mutants that are both hypersensitive and resistant. Using FunSpec, the hypersensitive mutants and a resistantace2mutant clustered within a category of genes related directly or indirectly to mitochondrial functions. InCandida albicans, the functions of the Ace2p transcription factor include the regulation of glycolysis. Our model is that DFD-VI-15 targets a respiratory pathway that limits energy production. Supporting this hypothesis are phenotypic data indicating that DFD-VI-15 causes increased cell-reactive oxidants (ROS) and a decrease in mitochondrial membrane potential. Also, the same compound has activity when cells are grown in a medium containing glycerol (mitochondrial substrate) but is much less active when cells are grown anaerobically.