2400. Activity of a Long-Acting Echinocandin, Rezafungin, Tested Against Invasive Fungal Isolates Collected Worldwide

BACKGROUND: Echinocandins are important agents for treating invasive fungal infections. We evaluated the activity of rezafungin (RZF; previously CD101), an echinocandin with extended half-life, and comparators using CLSI broth microdilution methods against 719 invasive fungal isolates collected worldwide during 2017. METHODS: Susceptibility tests were conducted on 616 Candida spp. (6 species), 25 C. neoformans (CNEO), 18 A. flavus (AFL), and 60 A. fumigatus (AFU) for RZF, anidulafungin, caspofungin, micafungin, and azoles. CLSI clinical breakpoint (CBP) and epidemiological cutoff value (ECV) interpretive criteria were applied. RESULTS: RZF inhibited 100.0% of C. albicans (CA) isolates, 96.3% of C. tropicalis (CT), 93.4% of C. glabrata (CG), 100.0% of C. krusei, and 100.0% of C. dubliniensis at ≤0.12 µg/mL. All but 2 (116/118 [98.3%]) C. parapsilosis (CP) isolates were inhibited by RZF at ≤2 µg/mL. Resistance to fluconazole was detected among 10.7% of CG, 10.2% of CP, 1.9% of CT, and 0.7% of CA. The activity of RZF against these 6 Candida spp. was similar to that of the other echinocandins, the vast majority of which were susceptible/wild type (WT) using CBP/ECV. Fluconazole and other triazoles displayed good activity against CNEO whereas echinocandins, including RZF, displayed limited activity against CNEO isolates (MIC90 >8 µg/mL). Echinocandins displayed good activity against ASF and AFL, and RZF activity was similar to that of anidulafungin, caspofungin, and micafungin. All isolates displayed WT MIC values for the mold-active azoles. CONCLUSION: Rezafungin was as active as other echinocandins against common fungal organisms recovered from invasive fungal infections. The extended half-life and stability of rezafungin is very desirable for prevention and treatment, especially in patients who could be discharged on outpatient therapy. [Image: see text] DISCLOSURES: M. A. Pfaller, Cidara Pharmaceuticals: Research Contractor, Research support. S. A. Messer, Cidara Pharmaceuticals: Research Contractor, Research support. P. R. Rhomberg, Cidara Pharmaceuticals: Research Contractor, Research support. B. A. Schaefer, Cidara Pharmaceuticals: Research Contractor, Research support. M. Castanheira, Cidara Pharmaceuticals: Research Contractor, Research support.