Preclinical Evaluation Shows CD101, a Novel Echinocandin, is Highly Stable with No Hepatotoxicity in Rats

V. Ong, G. Hough, M. Schlosser, K. Bartizal, J. Balkovec, K. James, R. Krishnan

Author address: 

Cidara Therapeutics, San Diego, CA

Abstract: 

Background: 

CD101 shows robust efficacy in mouse antifungal models. In preclinical evaluation, studies were conducted to compare the toxicity of CD101 to anidulafungin (ANID), with focus on assessing hepatotoxicity at comparable exposures. 

Methods: 

Metabolic stability and CYP activity were determined with human liver microsomes. Protein binding of CD101 in plasma and dose range toxicity/PK were determined. SD rats (10/sex/group) were administered CD101 (0, 2, 6, and 20 mg/kg) or ANID (40 mg/kg) by IV infusion via the tail vein. Clinical signs, chemistries, hematology, and liver histopathology were studied. Reactive species screening was performed by incubation of CD101 or ANID in PBS at 37oC for 2 h in the presence of 5 M excess of glutathione (GSH). Samples were analyzed using high resolution LC/MS with concurrent low and high energy scans to obtain full scan parent and product fragment ions. 

Results:

 CD101 was stable to biotransformation in liver microsomes and hepatocytes and during in vivo studies. In vitro CYP inhibition studies suggest minimal interaction with recombinant CYP enzymes with IC50s >10 µM. Similar to ANID, CD101 bound avidly (>98%) to human, mouse, rat, and primate plasma proteins. In a 2-wk rat hepatotoxicity screen, animals treated with CD101 did not exhibit effects on BW, hematology, coagulation or urinalysis. No microscopic liver findings were observed for CD101 at all doses. ANID at 40 mg/kg gave similar plasma levels as 20 mg/kg of CD101. At this dose, ANID treatment resulted in reduced BW, decreases in RBC, hemoglobin, hematocrit, mean cell volume, mean corpuscular hemoglobin, platelet and reticulocyte counts, increases in neutrophil and eosinophil counts, polychromasia and decreased aPTT. Elevated ALT, AST, total bilirubin, cholesterol and globulin, dark and enlarged spleens and single cell hepatocyte necrosis were also observed for ANID. We hypothesized that hepatotoxicity may be due to the inherent chemical lability of ANID generating potentially reactive intermediates. A GSH trapping experiment confirmed the presence of a reactive species for ANID whereas CD101 did not exhibit instability or any reactive intermediate.

Conclusions: 

Preclinical studies demonstrated CD101 was metabolically stable and was devoid of hepatotoxicity at doses up to 20 mg/kg when dosed in rats for 2 weeks.

abstract No: 

A-015
    • ICAAC 55th (2015)