Leveraging the MMV Pathogen Box to Engineer an Antifungal Compound with Improved Efficacy and Selectivity against Candida auris

Fungal
infections pose a significant and increasing threat to human
health, but the current arsenal of antifungal drugs is inadequate.
We screened the Medicines for Malaria Venture (MMV) Pathogen Box for
new antifungal agents against three of the most critical Candida species (Candida albicans, Candida auris, and Candida glabrata). Of the 14 identified hit compounds, most were active against C. albicans and C. auris. We selected the pyrazolo-pyrimidine MMV022478 for chemical modifications
to build structure–activity relationships and study their antifungal
properties. Two analogues, 7a and 8g, with
distinct fluorine substitutions, greatly improved the efficacy against C. auris and inhibited fungal replication inside
immune cells. Additionally, analogue 7a had improved
selectivity toward fungal killing compared to mammalian cytotoxicity.
Evolution experiments generating MMV022478-resistant isolates revealed
a change in morphology from oblong to round cells. Most notably, the
resistant isolates blocked the uptake of the fluorescent dye rhodamine
6G and showed reduced susceptibility toward fluconazole, indicative
of structural changes in the yeast cell surface. In summary, our study
identified a promising antifungal compound with activity against high-priority
fungal pathogens. Additionally, we demonstrated how structure–activity
relationship studies of known and publicly available compounds can
expand the repertoire of molecules with antifungal efficacy and reduced
cytotoxicity to drive the development of novel therapeutics.