Safety and Pharmacokinetics of CD101 IV, a Novel Echinocandin, in Healthy Adults

Pharmacokinetics of the Novel Echinocandin CD101 in Multiple Animal Species

CD101 is a novel semisynthetic echinocandin with antifungal activity against Candida and Aspergillus spp. The pharmacokinetics (PK) of CD101 administered intravenously to mice, rats, dogs, cynomolgus monkeys, and chimpanzees are presented. CD101 consistently exhibited very low clearance, a modest volume of distribution at steady state (Vss), and a long half-life (t1/2) across all species tested. In mouse, rat, dog, cynomolgus monkey, and chimpanzee, CD101 clearance was 0.10, 0.47, 0.30, 0.41, and 0.06 ml/min/kg, respectively; Vss was 206, 1,390, not determined, 597, and 400 ml/kg, respectively; and t1/2 was 25, 39, 53, 40, and 81 h, respectively. CD101 demonstrated a lower clearance and correspondingly longer half-life than those of anidulafungin, with more pronounced differences in higher species (anidulafungin t1/2, 8 h in cynomolgus monkey and 30 h in chimpanzee). In the rat, tissue/plasma area under the concentration-time curve (AUC) ratios, in descending order, were 4.62 (kidney), 4.33 (lung), 4.14 (liver), 3.87 (spleen), 1.09 (heart), and 0.609 (brain), indicating that CD101 exposure relative to plasma levels was comparable for major organs (approximately 4-fold higher in tissue than in plasma), with the exception of the heart and brain. Biliary elimination of intact CD101 was the predominant route of excretion; the mean cumulative amount of CD101 excreted into the bile and feces over the course of 5 days accounted for 22.6% and 27.7% of the total dose administered, respectively. There were no sex differences in the pharmacokinetics of CD101. Given its low clearance, long half-life, and wide tissue distribution, CD101 once weekly is expected to provide appropriate systemic levels for treatment and prevention of invasive fungal infections.

Structure-Activity Relationships of a Series of Echinocandins and the Discovery of CD101, a Highly Stable and Soluble Echinocandin with Distinctive Pharmacokinetic Properties

Echinocandins are a first-line therapy for candidemia and invasive candidiasis. They are generally safe with few drug interactions, but the stability and pharmacokinetic properties of currently approved echinocandins are such that each was developed for daily intravenous infusion. We sought to discover a novel echinocandin with properties that would enable more flexible dosing regimens, alternate routes of delivery, and expanded utility. Derivatives of known echinocandin scaffolds were generated, and an iterative process of design and screening led to the discovery of CD101, a novel echinocandin that has since demonstrated improved chemical stability and pharmacokinetics. Here, we report the structure-activity relationships (including preclinical efficacy and pharmacokinetic data) for the series of echinocandin analogs from which CD101 was selected. In a mouse model of disseminated candidiasis, the test compounds displayed clear dose responses and were generally associated with lower fungal burdens than that of anidulafungin. Single-dose pharmacokinetic studies in beagle dogs revealed a wide disparity in the half-lives and volumes of distribution, with one compound (now known as CD101) displaying a half-life that is nearly 5-fold longer than that of anidulafungin (53.1 h versus 11.6 h, respectively). In vitro activity data against panels of Candida spp. and Aspergillus spp. demonstrated that CD101 behaved similarly to approved echinocandins in terms of potency and spectrum of activity, suggesting that the improved efficacy observed in vivo for CD101 is a result of features beyond the antifungal potency inherent to the molecule. Factors that potentially contribute to the improved in vivo efficacy of CD101 are discussed.