Extended Use of Topical Efinaconazole Remains Safe and Can Provide Continuing Benefits for Dermatophyte Toenail Onychomycosis

Introduction: Efinaconazole 10% topical solution labeling for onychomycosis describes phase III trials of 12 months of treatment; the slow growth of onychomycotic nails suggests a longer treatment period may increase efficacy. We present here the first evaluation of extended use of efinaconazole 10% topical solution for up to 24 months. Materials and Methods: Enrolled patients (n = 101) had one target great toenail with mild to moderate distal lateral subungual onychomycosis and applied efinaconazole 10% topical solution to all affected toenails once daily for 18 months (EFN18) or 24 months (EFN24). Efficacy and safety were evaluated at each visit by visual review and mycology sampling. Results: Regarding the target toenail for patients treated for 24 months (EFN24), mycological cure (negative microscopy and culture) was 66.0% at Month 12, increasing to 71.7% at Month 24; effective cure (mycological cure and ≤10% affected nail) was 13.2% at Month 12, rising to 22.6% at Month 24. Mild to moderate application site reactions (symptoms of erythema/scaling) were the only efinaconazole-related reactions, in eight patients (7.9%). No systemic efinaconazole events or drug interactions were found. Patients aged 70 years or more had similar efficacy to younger patients at all time periods and did not show any increased treatment risks. Thinner nails exhibited better clearance versus thicker nails. A higher proportion of patients with Trichophyton mentagrophytes complex infection experienced application site reactions (35.7%), and a higher effective cure was found at Month 24 versus T. rubrum patients. Conclusion: There is a trend of increasing mycological cure and effective cure beyond Month 12 to Month 24, without an increased safety risk. The enrolled population in this trial was significantly older than in the phase III trials, with a greater degree of onychomycosis severity; however, increased age did not appear to reduce the chance of efficacy to Month 24 in this study. Our data suggest that lack of ability to clear nail dystrophy remains a significant problem for patients, rather than any lack of efinaconazole action over long-term treatment periods.