Identification and characterization of potent, broad-spectrum antifungal compounds using a yeast reporter bioassay.. Candida albicans

New antifungal drugs are urgently needed due to the currently limited selection, the emergence of drug resistance, and the toxicity of several commonly used drugs. To identify drug leads, we screened small molecules using a Saccharomyces reporter bioassay in which the yeast heterologously expresses Hik1, a group III hybrid histidine kinase (HHK) from Magnaporthe grisea. Group III HHKs are integral in fungal cell physiology, and highly conserved throughout this kingdom; they are absent in mammals, making them an attractive drug target. Our screen identified compounds 13 and 33, which showed robust activity against numerous fungal genera including Candida, Cryptococcus and molds such as Aspergillus and Rhizopus. Drug-resistant Candida from patients were also highly susceptible to compounds 13 and 33. While the compounds do not act directly on HHKs, microarray analysis showed that compound 13 induced transcripts associated with oxidative stress, and compound 33, transcripts linked with heavy metal stress. Both compounds were highly active against Candida biofilm, in vitro and in vivo, and exerted synergy with fluconazole, which was inactive alone. Thus, we identified potent, broad-spectrum antifungal drug leads from a small molecule screen using a high-throughput, yeast reporter bioassay. Overall design: Two-color experimental design testing the effects of 2 antifungal compounds (13 and 33) after 0, 20, 40 60 min. In the referred publication, the t=20, 40, 60 data was normalized against the t=0 data