Safety and Efficacy of a 48-Month Efinaconazole 10% Solution Treatment/Maintenance Regimen: 24-Month Daily Use Followed by 24-Month Intermittent Use

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Background/Objectives: In an 18- to 24-month Treatment Phase with once-daily efinaconazole 10% solution, subjects with onychomycosis showed an increased rate of cure at Month 24 versus the phase III trials. In order to further improve efficacy, we initiated an extended intermittent efinaconazole Maintenance Phase with use 2–3 times weekly for an additional 24 months from Month 24 to Month 48. These are the first data presented for a 48-month efinaconazole use period. Methods: For patients completing 18–24 months of once-daily efinaconazole, the target great toenail from the Treatment Phase was graded as ‘Clinical Cure’ (≤10% affected area) or ‘No Clinical Cure’ (>10% affected area) at Month 24. Mycological and clinical outcomes were assessed every 4 months from Month 24 to Month 48. There were 35 patients who enrolled in the extension and continued intermittent efinaconazole use to Month 48. Patients with ‘Clinical Cure’ at M24 were reviewed for sustained cure at M48; patients with ‘No Clinical Cure’ were reviewed for development of ‘Cure’ at M48. All patients were reviewed at all visits for adverse events that may be related to efinaconazole use. Results: ‘Clinical Cure’ was found in 6 of 35 enrolled patients at Month 24, and clinical cure status was sustained to Month 48 with intermittent efinaconazole maintenance use. For 29 patients with ‘No Clinical Cure’, 3/29 achieved ‘Clinical Cure’ status at Month 48 with intermittent efinaconazole. Effective Cure and Complete Cure rates improved over the maintenance period to Month 48 in subjects without clinical cure at Month 24. Younger patients showed higher cure rates over the maintenance period, but age group cure differences did not reach statistical significance in this dataset, and 49% of the ≥70-year population had at least a 20% reduction in nail area with maintenance therapy to Month 48. There was only 1 case of possible efinaconazole application site reaction in the Intermittent Maintenance Period to Month 48; prolonged efinaconazole use to Month 48 does not appear to increase the risk of reaction. Efinaconazole use periods are associated with very low positive culture rates in this dataset, including typical contaminant organisms, suggesting efinaconazole presence in the nail plate is providing prophylactic therapy. Conclusions: Intermittent efinaconazole may provide suitable prophylaxis of onychomycosis relapse. Prolonged efinaconazole therapy to Month 48 appears to be safe for all ages and can continue to provide prophylaxis of onychomycosis with Intermittent Maintenance use beyond Month 24 to Month 48.