Antifungal Activity of Efinaconazole Compared with Fluconazole, Itraconazole, and Terbinafine Against Terbinafine- and Itraconazole-Resistant/Susceptible Clinical Isolates of Dermatophytes, Candida, and Molds.

Background: Recently, an increasing number of resistant-to-terbinafine dermatophytosis cases have been reported. Thus, identifying an alternative antifungal agent that possesses broad-spectrum activity, including against resistant strains, is needed.

Methods: We compared the antifungal activity of efinaconazole with that of fluconazole, itraconazole, and terbinafine against clinical isolates of dermatophytes, Candida, and molds using in vitro assays. Minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of each antifungal agent were quantified and compared. Susceptible and resistant clinical isolates of Trichophyton mentagrophytes (n = 16), Trichophyton rubrum (n = 43), Trichophyton tonsurans (n = 18), Trichophyton violaceum (n = 4), Candida albicans (n = 55), Candida auris (n = 30), Fusarium spp, Scedosporium spp, and Scopulariopsis spp (n = 15 for each) were tested.

Results: Efinaconazole was the most active antifungal agent tested against dermatophytes, with MIC50 and MIC90 (concentrations that inhibited 50% and 90% of strains tested, respectively) values of 0.002 and 0.03 µg/mL, respectively. Fluconazole, itraconazole, and terbinafine showed MIC50 and MIC90 values of 1 and 8 µg/mL, 0.03 and 0.25 µg/mL, and 0.03 and 16 µg/mL, respectively. Against Candida isolates, efinaconazole MIC50 and MIC90 values were 0.016 and 0.25 µg/mL, respectively, whereas fluconazole, itraconazole, and terbinafine had MIC50 and MIC90 values of 1 and 16 µg/mL, 0.25 and 0.5 µg/mL, and 2 and 8 µg/mL, respectively. Against various mold species, efinaconazole MIC values ranged from 0.016 to 2 µg/mL versus 0.5 to greater than 64 µg/mL for the comparators.

Conclusions: Efinaconazole showed superior potent activity against a broad panel of susceptible and resistant dermatophyte, Candida, and mold isolates.