Enhanced transungual delivery from a film-forming nail platform under wash conditions: Evidence from bovine hoof and human nail models.

Onychomycosis is difficult to treat topically because the keratinized nail plate restricts drug diffusion and solution-based products are readily removed by washing. This study evaluated a fast-drying, polymer-based film-forming nail platform designed to create a wash-resistant surface reservoir and enhance transungual delivery. Terbinafine, efinaconazole, and amorolfine were formulated in the same platform and compared with marketed products (Terclara®, Jublia®, and Loceryl®) using bovine hoof keratin membranes and distal human nail clippings in Franz diffusion cells. In this bovine hoof model, cumulative permeation at 72 h was 9.5-fold higher for terbinafine versus Terclara® and 25.5-fold higher efinaconazole versus Jublia®; although the amorolfine permeation difference was not significant, receptor solutions from all three platform formulations produced significantly larger zones of inhibition against Trichophyton rubrum and Trichophyton mentagrophytes than their comparators, indicating that permeated drug remained biologically active. In a 28-day once-daily distal human nail model, the optimized terbinafine formulation (HLK-5003) maintained cumulative permeation and antifungal activity whereas the solution comparator showed minimal delivery and no detectable inhibition; advantages for the efinaconazole and amorolfine formulations were not established. These in vitro findings indicate that rapid film formation and wash-resistant reservoir behavior can improve sustained transungual delivery in a formulation- and API-dependent manner.