Abstract
Onychomycosis is a therapeutically challenging fungal infection. Systemic antifungals are limited by adverse effects and drug interactions, while topical therapies may fail to achieve therapeutic nail bed concentrations. Nitric oxide (NO), a small, diffusible free radical with broad-spectrum antimicrobial activity, offers a novel approach to overcoming these barriers. We assessed the penetration and subsequent efficacy of a nitric oxide-releasing gel (NORG) in the treatment of onychomycosis. Ex vivo human nail models assessed NORG's transungual penetration and antifungal activity via colorimetric, immunohistochemical, and microbiological assays. NORG eradicated Trichophyton mentagrophytes completely (0 CFU/g), outperforming terbinafine (3.58 ± 0.2 log(10) CFU/g). In an ex vivo infection model, NORG achieved fungal clearance within 14 days, continuing to Day 30 treatment end, with no regrowth during 21 days of incubation post-treatment. Clinical data from patients with onychomycosis who received topical NORG therapy show that NORG penetrated the nail plate and nail bed, as evidenced by s-nitrosothiol accumulation and progressive discoloration. The NORG formulation demonstrates in vitro efficacy; controlled trials are warranted to fully assess clinical efficacy and safety of this NORG formulation in humans, and establish optimal treatment protocols.