Objective: To assess the potential efficacy, safety, and optimal dosing concentration of tavaborole, a novel, boron-based pharmaceutical agent with broad-spectrum antifungal activity, for the treatment of onychomycosis of the toenail due to dermatophytes.
Methods: One double-blind, randomized, vehicle-controlled study (study 1) and two open-label studies (studies 2 and 3) examined the efficacy, safety, and optimal dosing concentration of tavaborole topical solution applied once daily or three times weekly for 180 days at concentrations of 1.0%, 2.5%, 5.0%, or 7.5%. Patient cohort 3 of study 2 received open-label tavaborole 5.0% once daily for 360 days. All three studies assessed day 180 treatment success, defined as complete or partial clinical evidence of clear nail growth plus negative fungal culture.
Results: A total of 336 patients were included in the intent-to-treat (ITT) or modified ITT populations and efficacy analyses across the 3 studies. In study 1, treatment success rates at day 180 were higher with tavaborole 2.5%, 5.0%, and 7.5% vs vehicle (27%, 26%, and 32% vs 14%, respectively; slope P=0.030). In cohort 3 of study 2, 7% of patients achieved treatment success with tavaborole 5.0% at day 360. Negative culture rates at day 180 in study 1 were numerically higher for tavaborole 2.5%, 5.0%, and 7.5% vs vehicle (slope P=0.046). Application-site reactions of general irritation, erythema, scaling, and stinging/burning were most common with tavaborole 7.5%, were generally mild to moderate, and resolved with treatment discontinuation and/or a reduction in dosing frequency. No systemic safety concerns were observed.
Conclusion: Tavaborole solution demonstrated favorable efficacy and safety in phase 2 clinical studies. Based on these findings, tavaborole topical solution, 5% was further investigated in larger, more definitive phase 3 studies. Results from these completed phase 3 studies will provide additional evidence regarding the safety and efficacy of tavaborole in the treatment of toenail onychomycosis.