The In Vitro Activity of Rezafungin Against Uncommon Species of Candida.

Background: Invasive candidiasis (IC) is increasing due to the rising numbers of immunocompromised patients. Increasing azole resistance rates and daily dosing required for most echinocandins have complicated its treatment. The approval of rezafungin has provided an option for weekly echinocandin treatment. The susceptibility of less common Candida spp. to rezafungin is unclear. We looked at the minimum inhibitory concentrations (MICs) of rezafungin and comparator agents against Candida spp. collected as part of a global surveillance program.

Method: The CLSI reference broth microdilution method was performed to test 590 clinical isolates of 28 different Candida species, including Candida auris. Species-specific interpretative criteria by breakpoints or epidemiological cutoff values were applied where available.

Results: Rezafungin was within ±2-fold MIC₅₀/₉₀ values of other echinocandins against all Candida spp. The lowest rezafungin MIC₅₀/₉₀ values were noted against C. kefyr (0.03/0.06 mg/L) and C. pelliculosa (0.015/0.03 mg/L). Higher rezafungin MIC₅₀/₉₀ values were noted for C. guilliermondii (1/1 mg/L) and for isolates in the C. parapsilosis complex (C. orthopsilosis, 0.5/1 mg/L, C. metapsilosis, 0.12/0.5 mg/L). Rezafungin was active against 97.7% of C. dubliniensis and 95.4% of C. auris by CLSI breakpoints. For fluconazole, 69.7% of C. guilliermondii, 85.7% of C. orthopsilosis, and 100% of C. metapsilosis were wildtype by ECV, and 10.8% of C. auris were susceptible by CDC breakpoint.

Conclusions: Rezafungin was highly active by in vitro testing against less common Candida spp. Rezafungin MICs were comparable to other echinocandins. Rezafungin is a desirable therapeutic alternative due to its reduced dosing frequency.