# Synergistic effects of Cyp51 isozyme-specific azole antifungal agents on fungi with multiple cyp51 isozyme genes

## TL;DR

This paper shows that combining specific antifungal drugs can work better against fungi with multiple Cyp51 enzymes, offering new treatment strategies.

## Contribution

The study reveals synergistic effects of isozyme-specific azole antifungals against fungi with multiple Cyp51 isozymes.

## Key findings

- Cyp51B is essential for basal growth, while Cyp51A is inducible and linked to azole tolerance in Trichophyton rubrum.
- Combining isozyme-specific azoles shows synergistic effects against wild-type fungi and another species, Aspergillus welwitschiae.
- Different azoles show increased activity against specific Cyp51 knockout strains, suggesting isozyme-specific drug selectivity.

## Abstract

Pathogenic fungi pose significant societal challenges due to limited therapeutic targets resulting from the eukaryotic nature of fungi. This limitation emphasizes the importance of enhancing susceptibility to inhibitors of Cyp51, a crucial enzyme in ergosterol biosynthesis targeted by azole antifungals. In Cyp51 isozyme deletion strains (Δcyp51A and Δcyp51B) of Trichophyton rubrum, the predominant dermatophyte species, we found that Cyp51B is essential for basal mycelial growth, while Cyp51A functions as an inducible isozyme associated with azole tolerance. Based on these differential functions, we hypothesized that each isozyme would show distinct susceptibility to azole antifungals. Our study demonstrated that most azoles exhibited increased antifungal activity against Δcyp51A, while select agents demonstrated increased antifungal activity against Δcyp51B. Remarkably, fluconazole, sulconazole, and imazalil exhibited relatively increased activity against Δcyp51A, whereas prochloraz demonstrated increased activity against Δcyp51B. Combining these isozyme-selective agents exerted synergistic effects against the wild-type strain and the parent ku80-knockout strain but not against individual Cyp51 knockout mutants. Our data revealed that the two Cyp51 isozymes can be selectively inhibited by different azole antifungals, resulting in a synergistic effect when combined. This synergistic effect was also observed on another fungal species, Aspergillus welwitschiae, which also has two Cyp51 isozymes. These data demonstrate that combining azole antifungals with different Cyp51 isozyme selectivities exerts synergistic effects against fungi possessing multiple Cyp51 isozymes. These findings advance antifungal therapeutic strategies by demonstrating that the combination of antifungals with different Cyp51 isozyme selectivities offers a promising approach for treating fungal infections, opening new avenues for isozyme-specific drug development.