The Anti-helminthic Compound Mebendazole Has Multiple Antifungal Effects against Cryptococcus neoformans

Abstract

<i>Cryptococcus neoformans</i> is the most lethal pathogen of the central nervous system. The gold standard treatment of cryptococcosis, a combination of amphotericin B with 5-fluorocytosine, involves broad toxicity, high costs, low efficacy, and limited worldwide availability. Although the need for new antifungals is clear, drug research and development (R&D) is costly and time-consuming. Thus, drug repurposing is an alternative to R&D and to the currently available tools for treating fungal diseases. Here we screened a collection of compounds approved for use in humans seeking for those with anti-cryptococcal activity. We found that benzimidazoles consist of a broad class of chemicals inhibiting <i>C. neoformans</i> growth. Mebendazole and fenbendazole were the most efficient antifungals showing <i>in vitro</i> fungicidal activity. Since previous studies showed that mebendazole reaches the brain in biologically active concentrations, this compound was selected for further studies. Mebendazole showed antifungal activity against phagocytized <i>C. neoformans</i>, affected cryptococcal biofilms profoundly and caused marked morphological alterations in <i>C. neoformans</i>, including reduction of capsular dimensions. Amphotericin B and mebendazole had additive anti-cryptococcal effects. Mebendazole was also active against the <i>C. neoformans</i> sibling species, <i>C. gattii</i>. To further characterize the effects of the drug a random <i>C. gattii</i> mutant library was screened and indicated that the antifungal activity of mebendazole requires previously unknown cryptococcal targets. Our results indicate that mebendazole is as a promising prototype for the future development of anti-cryptococcal drugs.