Exploiting Chemical Libraries to Identify and Characterize Novel Bioactives with Efficacy Against Pathogenic Candida Species

Candida species are amongst the most prevalent causes of systemic fungal infections, which account for over 1.5 million annual fatalities. Candida albicans represents the most common etiological agent; however, the rate of infections caused by non-albicans Candida species continues to rise. Here, I employed small-molecule screening and target-based approaches to identify and characterize compounds with novel antifungal activity. Initially, I discovered compounds with novel bioactivity against Candida auris by leveraging the Pathogen Box library. Of the hits identified, the tri-substituted isoxazole MMV688766, was pursued and was classified as a disruptor of cellular lipid homeostasis. Secondly, I further investigated the mechanism of action of a hit molecule from the University of Tokyo’s Core Chemical Library, NP-BTA, a compound predicted to inhibit the C. albicans glutaminyl tRNA synthetase Gln4. Co-crystallography and biochemical studies identified NP-BTA’s binding mechanism, and microbiological approaches confirmed that the Met496 residue is critical for compound binding. Accordingly, species possessing Met496 Gln4 variants, including Trichophyton rubrum, are susceptible to NP-BTA, while species harboring leucine or valine at this position are resistant. The poor metabolic profile of NP-BTA prompted us to assess the efficacy of this molecule in a mouse skin model of dermatomycosis. Finally, I engaged in a collaborative program to optimize inhibitors of the fungal casein kinase, Yck2. An existing Yck2 inhibitor, GW, was rationally modified to generate substituted analogues and imidazo[1,2-a]pyridine bio-isosters to improve metabolic stability. I identified four analogues with improved stability that retained anti-Candida bioactivity. Furthermore, all four analogues selectively inhibited C. albicans Yck2 over the human CK1 isoform, CK1α. Collectively, this work highlights molecules with efficacy against diverse fungal pathogens, which may pave the way for future antifungal drug development.

Department dc:contributor.department

Molecular Genetics

Year dc:date.issued

2024

Author dc:creator

• Puumala, Emily Shae

Advisor dc:contributor.advisor

• Cowen, Leah E

• Antifungals
• Antimicrobial resistance
• Candida
• Drug discovery
• Fungal pathogens

Statement dc:rights

• Attribution 4.0 International

Licence dc:rights.uri

• http://creativecommons.org/licenses/by/4.0/

Handle dc:identifier.uri

https://hdl.handle.net/1807/142548

OAI identifier oai:identifier

oai:utoronto.scholaris.ca:1807/142548