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

Abstract

Pathogenic fungi pose significant societal challenges. The limited availability of therapeutic targets due to the eukaryotic nature of fungi emphasizes the importance of available drug targets such as Cyp51, a crucial enzyme in ergosterol biosynthesis, inhibited by azole antifungals. This study explored the susceptibility patterns of azole antifungals against Cyp51 isozyme deletion strains ({Delta}cyp51A and {Delta}cyp51B) in Trichophyton rubrum, the predominant dermatophyte species. Distinct susceptible patterns were observed among azole antifungals for {Delta}cyp51A and {Delta}cyp51B. Although most azole antifungal agents exhibited increased antifungal activity against {Delta}cyp51A, select agents demonstrated increased antifungal activity against {Delta}cyp51B. Remarkably, fluconazole, sulconazole, and imazalil exhibited relatively increased activity against {Delta}cyp51A, whereas prochloraz demonstrated increased activity against {Delta}cyp51B. 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. Hence, the two Cyp51 isozymes, Cyp51A and Cyp51B, may be inhibited by distinct azole antifungals, exerting a synergistic effect with the dual azole antifungal combination. 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. This study proposes a novel therapeutic approach for addressing fungal infections through the combination of antifungal drugs that inhibit the same enzymatic activity but exhibit different isozyme selectivity. It also emphasizes the potential for developing drugs targeting specific isozymes, a previously underutilized approach in the realm of antifungal drug development.