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Updated: Jul 15, 2025
Quantifying the Antifungal Activity of Peptides Against Candida albicans
Published on: January 13, 2023
Leveraging the MMV Pathogen Box to Engineer an Antifungal Compound with Improved Efficacy and Selectivity against
Baolong Pan1, Harshini Weerasinghe2,3, Aysha Sezmis4
1Monash Institute of Pharmaceutical Sciences, Monash University, Parkville 3052, VIC, Australia.
Abstract:
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.
Insights
Researchers identified a promising new antifungal compound effective against critical Candida species, including drug-resistant strains. This discovery offers hope for developing novel treatments against invasive fungal infections.
Area of Science:
- Mycology and Infectious Diseases
- Medicinal Chemistry
- Drug Discovery
Background:
- Fungal infections represent a growing global health concern, exacerbated by a limited and often inadequate supply of effective antifungal medications.
- The rise of drug-resistant fungal pathogens, particularly *Candida* species, necessitates the urgent development of new therapeutic agents.
Purpose of the Study:
- To screen the Medicines for Malaria Venture (MMV) Pathogen Box for novel antifungal compounds targeting critical *Candida* species (*C. albicans*, *C. auris*, *C. glabrata*).
- To optimize lead compounds through structure-activity relationship (SAR) studies, aiming to enhance antifungal efficacy and reduce cytotoxicity.
- To investigate mechanisms of resistance and potential cross-resistance to existing antifungal drugs.
Main Methods:
- Screening of the MMV Pathogen Box against *Candida* species.
- Chemical modification of a pyrazolo-pyrimidine hit compound (MMV022478) to generate analogues.
- Antifungal activity assays, including inhibition of fungal replication within immune cells.
- Cytotoxicity assessments against mammalian cells.
- Fungal evolution experiments to generate resistant isolates and investigate resistance mechanisms (e.g., dye uptake, fluconazole susceptibility).
Main Results:
- Identification of 14 hit compounds with antifungal activity, predominantly against *C. albicans* and *C. auris*.
- Two modified analogues, 7a and 8g, demonstrated significantly enhanced efficacy against *C. auris* and inhibited intracellular fungal growth.
- Analogue 7a exhibited improved selectivity, showing greater fungal cell killing compared to mammalian cell toxicity.
- Resistant *Candida* isolates developed altered cell morphology, reduced rhodamine 6G uptake, and decreased susceptibility to fluconazole, suggesting cell surface alterations.
Conclusions:
- A novel pyrazolo-pyrimidine derivative shows significant potential as an antifungal agent against high-priority *Candida* pathogens.
- SAR studies on publicly available compounds can effectively expand the pipeline of antifungal drug candidates.
- Understanding resistance mechanisms, including cell surface changes, is crucial for developing next-generation antifungal therapies with reduced cross-resistance.
