Anidulafungin is a Useful Surrogate Marker for Predicting In Vitro Susceptibility to Rezafungin among five Candida species Using CLSI Methods and Interpretive Criteria

Rezafungin, a second-generation echinocandin with improved chemical and biological properties compared to other echinocandins, was approved in 2023 by the United States Food and Drug Administration (US FDA) for the treatment of candidemia and invasive candidiasis. Rezafungin possesses activity against diverse Candida species including isolates susceptible and nonsusceptible to azoles and other echinocandins. This study addresses the use of susceptibility against other echinocandins as surrogate markers to predict the rezafungin susceptibility against the six most common Candida species collected as part of a global surveillance program between 2014-2022. Echinocandin broth microdilution susceptibility testing was performed on the collection of nonduplicate Candida isolates. The cell wall biosynthesis enzymes FKS1 and FKS2, each possessing known mutational hotspots reducing the activity of other echinocandins, were further examined in rezafungin-nonsusceptible isolates.