Drug properties of fosravuconazole L-lysine ethanolate (NAILIN<sup>®</sup> Capsules 100 mg), a new oral azole therapeutic for onychomycosis: an analysis based on non-clinical and clinical trial data

Abstract

Ravuconazole is a fourth generation azole exerting strong antifungal activity, with low drug-drug interaction and hepatic dysfunction risks. Fosravuconazole l-lysine ethanolate (fosravuconazole; NAILIN® Capsules 100 mg) was developed as a ravuconazole prodrug. Ravuconazole exerts strong antifungal activity against various pathogenic fungi including dermatophytes and Candida. Through prodrug formation, pharmacokinetic improvement was achieved, and bioavailability after oral administration reached 100%. The plasma ravuconazole concentration became 10-35 times higher than with current oral anti-onychomycosis drugs, and showed good skin and nail tissue transition plus tissue retention. This improvement obtained with fosravuconazole reflects its superior pharmacokinetic properties. We conducted a clinical trial with fosravuconazole orally administered once a day (100 mg ravuconazole) for 12 weeks in Japanese onychomycosis patients. The ravuconazole concentration in nail tissues exceeded the MIC90 against dermatophytes, even after treatment completion. Furthermore, the placebo-controlled, double-blind, comparative trial showed significantly superior effects (at 48 weeks after starting treatment, with a complete cure rate of 59.4%, a marked clinical improvement rate of 83.1%, and a mycological cure rate by direct microscopy of 82.0%). The major adverse reactions were laboratory abnormalities and gastrointestinal disorders with no severe symptoms, suggesting good tolerability. Fosravuconazole has fewer drug-drug interactions, is not affected by food, and is also expected to improve medication adherence since the administration period is only 12 weeks and there is no drug-free period as required with pulse therapy. Thus, fosravuconazole has many favorable pharmacological properties and can reasonably be expected to become a new oral treatment option for onychomycosis.