Topical Tavaborole in the Treatment of Onychomycosis Complicated by Dermatophytoma: A Post-hoc Assessment of Phase II Subjects.

Dermatophytoma is a little-known, difficult to treat fungal infection that complicates onychomycosis. First described by Roberts and Evans in the late 1990's, dermatophytoma presents as a dense concentration of fungal hyphae within or under the nail plate and is generally white or yellow/brown in color, and linear (streaks) or round (patches) in shape; primary etiologic organisms are dermatophytes. Oral antifungals have limited success in treating dermatophytoma owing to difficulties accessing and penetrating what is hypothesized to be a fungal biofilm. In this respect, dermatophytoma is generally treated with a combination therapy approach, often including both surgical and pharmacologic intervention for improved outcomes. A post-hoc assessment of Phase II tavaborole onychomycosis studies was conducted in order to assess the prevalence of dermatophytoma and outcomes in patients treated with topical tavaborole. Of the 366 subjects enrolled in the Phase II onychomycosis studies, we identified 102 cases of dermatophytoma; 21 of 86 (24.4%) subjects treated with tavaborole were able to achieve complete resolution of dermatophytoma by day 180, while no subjects on vehicle obtained resolution. Similarly, 23 of 86 subjects (26.7%) treated with tavaborole solution had complete resolution of dermatophytoma by day 360, while only 1 of 16 subjects (6.3%) on vehicle obtained resolution. Moreover, 13 of 19 subjects (68.4%) treated with tavaborole solution were able to sustain resolution, while only 6 of 19 (31.6%) had reoccurrence, of dermatophytoma during the 180-day washout period (day 360). We present 5 cases of dermatophytoma identified in Phase II trials that responded in a positive manner following treatment with tavaborole solution for onychomycosis of the great toenail. Although not representative of all subject outcomes, these findings provide insight into the use of topical tavaborole for dermatophytoma, a condition previously thought to respond only to oral or combination therapy. <p><em>J Drugs Dermatol. 2018;17(3):347-354.</em></p>.