Rezafungin

Rezafungin is a novel antifungal agent of the echinocandin class with potent activity against species ofCandidaand Aspergillus, including subsets of resistant strains, and Pneumocystis jirovecii. The objective of this analysis was to develop a population pharmacokinetic (PK) model to characterize the disposition of rezafungin in plasma following intravenous (IV) administration in healthy volunteers and in patients with candidemia and/or invasive candidiasis. The population PK model was based on a previous model from phase 1 data; formal covariate analyses were conducted to identify any relationships between subject characteristics and rezafungin PK variability. A four-compartment model with linear elimination and zero-order drug input provided a robust fit to the pooled data. Several statistically significant relationships between subject descriptors (sex, infection status, serum albumin, and body surface area [BSA]) and rezafungin PK parameters were identified, but none were deemed clinically relevant. Previous dose justification analyses conducted using data from phase 1 subjects alone are expected to remain appropriate. The final model provided a precise and unbiased fit to the observed concentrations and can be used to reliably predict rezafungin PK in infected patients.

Rezafungin is a new echinocandin in development for treatment of candidemia and invasive candidiasis, and for prophylaxis of invasive fungal infections. Rezafungin is the first echinocandin to undergo definitive QT/QTc study. This phase 1, single-center, randomized, double-blind trial was conducted to assess effects of intravenous rezafungin vs intravenous placebo (with moxifloxacin as positive control) on the QT interval of the electrocardiogram, corrected for heart rate by Fridericia's formula (QTcF), in healthy adults. Therapeutic (600 mg) and supratherapeutic (1400 mg) rezafungin doses were selected to achieve exposures 2.5-fold higher than produced by the highest dose used in a phase 2 trial (400 mg once weekly). The primary end point was change in QTcF from baseline (ΔQTcF) as a function of plasma concentration, assessed by comparing upper bounds of the 2-sided 90% confidence interval. The estimated mean ΔΔQTcF at the mean plasma concentrations for the rezafungin doses had upper bounds<10 milliseconds, within the upper bound of the 2-sided 90% confidence interval. Intravenous rezafungin up to 1400 mg in a single dose did not prolong QT interval and had no apparent effect on repolarization or QRS duration. Electrocardiogram results showed no clinically significant effects of concern. These findings support the continued development of rezafungin.

Rezafungin (formerly CD101) is a novel echinocandin in clinical development. EUCAST epidemiological cutoff values (ECOFFs) have not yet been established. We determined thein vitroactivity of rezafungin and comparators against 1,293 Nordic yeast isolates and 122 IndianCandida aurisisolates and established single-center wild-type upper limits (WT-UL). The isolates (19Candidaspp. and 13 other yeast species) were identified using Chromagar; matrix-assisted laser desorption ionization-time of flight (MALDI-TOF); and, when needed, internal transcribed spacer sequencing. EUCAST E.Def 7.3.1 susceptibility testing included rezafungin, anidulafungin, micafungin, amphotericin B, and fluconazole. WT-UL were established following EUCAST principles for visual and statistical ECOFF setting.fkstarget genes were sequenced for rezafungin non-wild-type isolates. EUCAST clinical breakpoints for fungi version 9.0 were adopted for susceptibility classification. Rezafungin had species-specific activity similar to that of anidulafungin and micafungin. On a milligram-per-liter basis, rezafungin was overall less active than anidulafungin and micafungin but equally or more active than fluconazole and amphotericin B against the most commonCandidaspecies, exceptC. parapsilosisWe identified 37 (3.1%) rezafungin non-wild-type isolates ofC. albicans(1.9%),C. glabrata(3.0%),C. tropicalis(2.7%),C. dubliniensis(2.9%),C. krusei(1.2%), andC. auris(14.8%). Alterations in Fks hot spots were found in 26/26 Nordic and 8/18 non-wild-typeC. aurisisolates. Rezafungin displayed broadin vitroactivity againstCandidaspp., includingC. aurisAdopting WT-UL established here, few Nordic strains, but a significant proportion ofC. aurisisolates, had elevated MICs with mutations infkstarget genes that conferred echinocandin cross-resistance.fks1mutations raised rezafungin MICs notably less than anidulafungin and micafungin MICs inC. auris.