Tavaborole, sold under the brand name Kerydin, is a topical antifungal medication for the treatment of onychomycosis, a fungal infection of the nail and nail bed with a complete clearance rate of 6-7% and partial clearance rate of 23-24% in individuals with toenail infection; it is a small boron-containing benzoxaborole compound formulated as a 5 percent topical solution that penetrates the nail plate to reach the nail bed, selectively inhibits fungal leucyl-tRNA synthetase leading to interruption of protein synthesis, has activity against Trichophyton rubrum and Trichophyton mentagrophytes, requires long-term daily application typically up to 48 weeks for clinical effect, and exhibits minimal systemic absorption with low plasma exposure after topical administration.
Typical API and product quality control specifications for tavaborole address related substances and degradation products using validated reversed-phase HPLC and LC-MS methods; common related compounds monitored include deboronated species (boron-free ring-opened products), desfluoro or other halogen positional isomers, oxidative metabolites and hydroxy derivatives, and ring-opened boronic acids; typical acceptance criteria used in many specifications are individual identified related substances not greater than 0.20 percent, individual unspecified impurities reported above 0.05 percent and controlled below 0.10 percent, and total impurities generally limited to not more than 1.0 percent, with residual solvents and heavy metals controlled to limits in ICH Q3C and ICH Q3D/USP monographs and qualification/identification performed per ICH Q3A and Q3B guidance.
Tavaborole has demonstrated modest but measurable clinical benefit in controlled trials when applied topically once daily for extended periods; complete clinical clearance rates are low at about 6-7 percent while partial clearance or improvement is more common at roughly 23-24 percent, and mycological eradication rates in some studies are higher than clinical complete cure, so outcomes depend strongly on baseline disease severity, adherence to the 48-week regimen, and organism susceptibility.
Although commonly supplied as a 5 percent topical solution, tavaborole is used topically to treat onychomycosis of the toenails caused by dermatophytes such as Trichophyton rubrum and Trichophyton mentagrophytes; it is intended for local application to the affected nail and surrounding skin to reduce fungal load and promote nail improvement over many months and is not indicated for systemic fungal infections.
Tavaborole is a boron-containing benzoxaborole that inhibits fungal leucyl-tRNA synthetase by interacting with the enzyme editing site and forming a stable adduct that blocks transfer of leucine to tRNA, thereby halting protein synthesis and exerting fungicidal or fungistatic effects depending on organism and concentration; its low molecular size and physicochemical properties facilitate penetration through the keratinized nail plate.
Adverse effects are predominantly local and generally mild to moderate, the most commonly reported being application site irritation such as erythema, exfoliation, dermatitis, or burning sensation; less common events include secondary nail abnormalities and contact allergic reactions; systemic adverse events are rare due to minimal systemic absorption, but any signs of severe hypersensitivity should prompt discontinuation and medical evaluation.
