Characterization of an allosteric inhibitor of fungal-specific C-24 sterol methyltransferase to treat Candida albicans infections

Summary Filamentation is an important virulence factor of the pathogenic fungus Candida albicans . The abolition of Candida albicans hyphal formation by disrupting sterol synthesis is an important concept for the development of antifungal drugs with high safety. Here, we conduct a high-throughput screen using a C . albicans strain expressing green fluorescent protein-labeled Dpp3 to identify anti-hypha agents by interfering with ergosterol synthesis. The antipyrine derivative H55 is characterized to have minimal cytotoxicity and potent inhibition of C . albicans hyphal formation in multiple cultural conditions. H55 monotherapy exhibits therapeutic efficacy in mouse models of azole-resistant candidiasis. H55 treatment increases the accumulation of zymosterol , the substrate of C-24 sterol methyltransferase (Erg6). The results of enzyme assays, photoaffinity labeling , molecular simulation, mutagenesis , and cellular thermal shift assays support H55 as an allosteric inhibitor of Erg6. Collectively, H55, an inhibitor of the fungal-specific enzyme Erg6, holds potential to treat C . albicans infections.