Small molecules restore azole activity against drug-tolerant and drug-resistant Candida isolates

Abstract

Each year, fungi cause more than 1.5 billion infections worldwide and havea devastating impact on human health, particularly in immunocompromised individuals or patients in intensive care units. The limited antifungal arsenal and emerging multidrug-resistant species necessitate the development of new therapies. One strategy for combating drug-resistant pathogens is the administration of molecules that restore fungal susceptibility to approved drugs. Accordingly, we carried out a screen to identify small molecules that could restore the susceptibility of pathogenic Candida species to azole antifungals. This screening effortled to the discovery of novel 1,4-benzodiazepines that restore fluconazolesusceptibility in resistant isolates of Candida albicans, as evidenced by 100-1,000-fold potentiation of fluconazoleactivity. This potentiation effectwas also observed in azole-tolerant strains of C. albicans and in other pathogenic Candida species. The 1,4-benzodiazepines selectively potentiated differentazoles, but not other approved antifungals. A remarkable feature of the potentiation was that the combination of the compounds with fluconazolewas fungicidal, whereas fluconazolealone is fungistatic. Interestingly, the potentiators were not toxic to C. albicans in the absence of fluconazole,but inhibited virulence-associated filamentationof the fungus. We found that the combination of the potentiators and fluconazolesignificantlyenhanced host survival in a Galleria mellonella model of systemic fungal infection. Taken together, these observations validate a strategy wherein small molecules can restore the activity of highly used anti-infectives that have lost potency.