2-Year animal carcinogenicity results for crisaborole, a novel phosphodiesterase 4 inhibitor for atopic dermatitis.

BACKGROUND: Crisaborole is a novel, topical nonsteroidal, anti-inflammatory, phosphodiesterase 4 (PDE4) inhibitor for the treatment of mild to moderate atopic dermatitis. OBJECTIVE: As part of a nonclinical safety testing program, these 2-year studies tested the carcinogenic potential of crisaborole. METHODS: Crisaborole ointment, 2%, 5%, or 7%, was applied once daily topically to mice, and crisaborole was administered orally to rats at doses of 30, 100, or 300mg/kg/day for up to 104 weeks. Systemic exposure to crisaborole and its metabolites, moribundity/death, clinical signs, and tumor formation were assessed in each study. RESULTS: Crisaborole treatment was not tumorigenic in mice at any of the doses administered and did not increase the incidence of neoplastic or nonneoplastic microscopic lesions compared with controls. Oral administration of crisaborole at the high dose (300mg/kg/day) to female rats increased the incidence of treatment-related benign granular cell tumors in the distal reproductive tract (uterus with cervix and vagina) but did not cause moribundity/death. CONCLUSION: Crisaborole was well tolerated and not tumorigenic in mice. It was not tumorigenic in male rats at 300mg/kg/day at exposures that were 3× the human area under the concentration-time curve (AUC24) and was nontumorigenic in female rats at 100mg/kg/day at exposures that were 1× the human AUC24.

Antifungal agents for onychomycosis: new treatment strategies to improve safety.

Onychomycosis is a common and difficult-to-treat fungal infection of the nail unit that gradually leads to dystrophic changes of the nail plate and nail bed. If untreated, infection progresses and may lead to discomfort, reduced quality of life, and risk of complications in patients with comorbid conditions (eg, diabetes, human immunodeficiency virus, peripheral vascular disease). Onychomycosis treatments are designed to eradicate causative pathogens (most commonly Trichophyton rubrum and Trichophyton mentagrophytes), restore healthy nails, and prevent recurrence or spread of infection. Given the deep-seated nature of most cases of onychomycosis, an effective antifungal agent needs to achieve and maintain sufficient drug concentrations throughout the nail unit for the duration of healthy nail in-growth. Oral antifungal drugs are the most effective available therapy and are generally well tolerated, but may be limited by safety concerns and the potential for drug-drug interactions (DDIs). Thus, treating physicians and pharmacists must be cognizant of a patient's current medications; indeed, it may not be feasible to treat onychomycosis in patients with diabetes, heart disease, or depression because of the risk for DDIs. Current topical therapy is not associated with risk of DDIs. Tavaborole and efinaconazole, two recently approved topical agents, have demonstrated good nail penetration and high negative culture rates in clinical trials of patients with onychomycosis. This article provides the treating physician and pharmacist with information on the safety and effectiveness of current oral (allylamine, azole) and topical (ciclopirox, efinaconazole, tavaborole) treatment to aid in making informed treatment decisions based on the unique characteristics (medication history, comorbidities, nature of onychomycosis) of each patient.

Tavaborole, a Novel Boron-Containing Small Molecule Pharmaceutical Agent for Topical Treatment of Onychomycosis: II. Prenatal and Postnatal Developmental Toxicity and Maternal Function Study.

Tavaborole is a topical antifungal agent approved by the US Food and Drug Administration for the treatment of toenail onychomycosis. The effects of tavaborole on gestation, parturition (delivery, labor), offspring development, and survival during the perinatal and postnatal periods were assessed in mated female rats. Females (F0 generation) were administered single daily oral (gavage) doses of 15, 60, or 100 mg/kg/d from gestation day 6 through lactation day 20. The females were allowed to deliver naturally and rear their offspring until lactation day 21, at which time the F0 females were euthanized. One male and female from each litter were selected (F1 generation) and retained for assessments, including growth, neurobehavior, fertility, and their ability to produce an F2 generation. Reproductive and offspring parameters were determined for the F1 and F2 generations, as applicable. F1 females and F2 pups were euthanized on postnatal day 7. In the F0 females, decreased activity was observed in the 100 mg/kg/d dose group. Excess salivation was observed in the 60 and 100 mg/kg/d dose groups (slight to moderate), however, this finding was not considered adverse. There were no tavaborole-related effects on the growth, viability, development, neurobehavioral assessments, or reproductive performance of the F1 generation. Survivability and mean body weight of the F2 pups were unaffected. The no observed adverse effect level (NOAEL) for maternal toxicity (F0 generation) was 60 mg/kg/d, based on the decreased activity observed in the 100 mg/kg/d dose group. The NOAEL for the offspring effects was ≥100 mg/kg/d, based on the lack of test article-related changes.

Crisaborole Topical Ointment, 2%: A Nonsteroidal, Topical, Anti-Inflammatory Phosphodiesterase 4 Inhibitor in Clinical Development for the Treatment of Atopic Dermatitis.

Crisaborole topical ointment, 2% (formerly known as AN2728) is a benzoxaborole, nonsteroidal, topical, anti-inflammatory phosphodiesterase 4 (PDE4) inhibitor investigational compound that recently completed phase 3 studies for the treatment of mild to moderate atopic dermatitis (AD). The unique configuration of boron within the crisaborole molecule enables selective targeting and inhibition of PDE4, an enzyme that converts the intracellular second messenger 3'5'-cyclic adenosine monophosphate (cAMP) into the active metabolite adenosine monophosphate (AMP). By inhibiting PDE4 and thus increasing levels of cAMP, crisaborole controls inflammation. The use of boron chemistry enabled synthesis of a low-molecular-weight compound (251 daltons), thereby facilitating effective penetration of crisaborole through human skin. In vitro experiments showed that crisaborole inhibits cytokine production from peripheral blood mononuclear cells in a pattern similar to other PDE4 inhibitors and distinct from corticosteroids. Crisaborole also displayed topical anti-inflammatory activity in a skin inflammation model. Once crisaborole reaches systemic circulation after topical application, it is metabolized to inactive metabolites. This limits systemic exposure to crisaborole and systemic PDE4 inhibition. In phase 1 and 2 clinical studies, crisaborole ointment, 2% was generally well tolerated and improved AD disease severity scores, pruritus, and all other AD signs and symptoms. Two large, randomized, controlled, phase 3, pivotal clinical trials assessing the efficacy and safety of crisaborole topical ointment, 2% in children, adolescents, and adults with mild to moderate AD were recently completed with positive results.

Tavaborole, a Novel Boron-Containing Small Molecule Pharmaceutical Agent for Topical Treatment of Onychomycosis: I. Reproductive and Developmental Toxicity Studies.

Tavaborole is a topical antifungal agent approved by the US Food and Drug Administration for the treatment of toenail onychomycosis. As part of the nonclinical development program, reproductive and developmental toxicity studies were conducted (rat oral fertility and early embryonic development, rat (oral) and rabbit (dermal) embryo-fetal development). There were no effects on fertility or reproductive performance at doses up to 300 mg/kg/d (107 times the maximum recommended human dose [MRHD] based on mean area under the plasma concentration-time curve comparisons). In the rat embryo-fetal development toxicity studies, teratogenicity was not observed at doses up to 100 mg/kg/d (29 times the MRHD). However, several treatment-related skeletal malformations and variations were observed at 300 mg/kg/d (570 times the MRHD). In rabbit embryo-fetal development toxicity studies dosed via oral or dermal administration, the no observable adverse effect level for maternal toxicity and embryo-fetal toxicity was 50 mg/kg/d (16 times the MRHD) and 5% (26 times the MRHD), respectively.

Evaluation of the Appearance of Nail Polish Following Daily Treatment of Ex Vivo Human Fingernails With Topical Solutions of Tavaborole or Efinaconazole.

INTRODUCTION: Patients with onychomycosis may mask infected nails with polish. Tavaborole topical solution, 5% is a boron-based, small-molecule pharmaceutical approved for the treatment of toenail onychomycosis caused by Trichophyton rubrum and Trichophyton mentagrophytes; efinaconazole topical solution, 10% is approved for the same indication. Nail polish appearance after application of tavaborole (dropper) or efinaconazole (brush); respective applicator appearance; presence of color transfer from respective applicators; and color transfer to remaining solutions after dosing of polished nails were evaluated. METHODS: Twelve ex vivo human cadaver fingernails were cleaned, polished with two coats of L'Oréal® Nail Color, Devil Wears Red #420, and mounted on floral foam. Nails were treated with tavaborole or efinaconazole solutions once daily for 7 days. Dropper and brush applicators were applied to white watercolor paper immediately after dosing to evaluate color transfer from polished nails. On day 7, remaining solutions were transferred to clear glass vials to evaluate color transfer from applicators to solutions. Nails, applicators, and papers were photographed daily following application; remaining solutions were photographed after 7 days of dosing. RESULTS: Tavaborole-treated polished nails showed no polish discoloration, and tavaborole applicators did not change in appearance during treatment. No color transfer from polished nails was evident to applicator, paper, or remaining solution. Efinaconazole-treated polished nails showed substantial polish changes after the first day of treatment, with polish appearance and discoloration progressively worsening over 7 days of treatment. Color transfer from nails was evident to applicator, paper, and remaining solution. CONCLUSIONS: Daily dropper application of tavaborole to ex vivo polished nails did not alter polish appearance. Brush application of efinaconazole produced visible changes in polish appearance and color transfer to applicators, paper, and remaining solution. Tavaborole topical solution, 5% may not alter nail polish appearance; the impact of nail polish on tavaborole clinical efficacy has not been evaluated.

In Vitro Nail Penetration of Tavaborole Topical Solution, 5%, Through Nail Polish on Ex Vivo Human Fingernails.

BACKGROUND: Onychomycosis is a common infection of the toenails that causes nail thickening and discoloration. The physical appearance of the infected nail can diminish self-image and negatively impact quality of life. Patients may use nail polish to mask the appearance of infected nails. OBJECTIVE: To evaluate the in vitro nail penetration properties of tavaborole topical solution, 5%, through nail polish using ex vivo, non-diseased human fingernails. METHODS: In study 1, tavaborole penetration was evaluated over 20 days of dosing using the Franz finite dose technique and modified Franz diffusion cells. Nails received either 1 coat of over-the-counter (OTC) typical polish or were left unpolished (controls). In study 2, tavaborole penetration was measured over 14 days of dosing using the finite dose technique and vertical diffusion cells. Nails were polished with either 4 coats or 1 coat of salon typical polish or with 2 coats or 1 coat of OTC typical polish, or they were left unpolished. RESULTS: In study 1, the mean ± standard deviation (SD) cumulative tavaborole penetration at day 21 was numerically higher, though not statistically significant, through polished nails (3,526 ± 1,433 µg/cm(2))vs unpolished nails (2,661 ± 1,319 µg/cm(2)).In study 2, the mean cumulative tavaborole penetration was also numerically higher (statistical significance not assessed) through all nails that received polish vs unpolished nails. At day 15, mean ± SD cumulative tavaborole nail penetration was 1,179 ± 554 µg/cm(2) through 4 coats of salon typical polish, 1,227 ± 974 µg/cm(2) through 1 coat of salon typical polish, 1,493 ± 1,322 µg/cm(2) through 2 coats of OTC typical polish, 1,428 ± 841 µg/cm(2) through 1 coat of OTC typical polish, and 566 ± 318 µg/cm(2) through unpolished nails. CONCLUSION: Results from these in vitro studies demonstrated that tavaborole penetrated through human nails with up to 4 layers of nail polish.

In Vitro Nail Penetration and Antifungal Activity of Tavaborole, a Boron-Based Pharmaceutical.

An effective topical antifungal medication must penetrate through the nail plate at sufficient concentrations to eradicate the fungal infection. Tavaborole topical solution, 5% is a novel boron-based pharmaceutical approved for the treatment of toenail onychomycosis due to Trichophyton rubrum or T mentagrophytes. Four in vitro studies assessed the antifungal activity and nail penetration of tavaborole. In Study 1, tavaborole demonstrated minimum inhibitory concentration (MIC) values ranging from 0.25-2 µg/mL against all fungi tested; addition of 5% keratin powder did not affect the MIC against T rubrum. The minimum fungicidal concentration (MFC) values for tavaborole against T rubrum and T mentagrophytes were 8 and 16 µg/mL, respectively. In Study 2, tavaborole effectively penetrated through the nail plate; mean concentrations in the ventral/intermediate nail layer were significantly higher than ciclopirox at day 15. In Study 3, mean cumulative tavaborole penetration through ex vivo human nails was significantly higher than ciclopirox at day 15. In Study 4, tavaborole demonstrated superior nail penetration and fungicidal activity, as measured by zones of inhibition. These studies demonstrated the superior penetration of tavaborole through the nail plate vs ciclopirox. Tavaborole demonstrated robust antifungal activity, with low MIC and MFC values, even in the presence of keratin.

Tavaborole, a novel boron-containing small molecule for the topical treatment of onychomycosis, is noncarcinogenic in 2-year carcinogenicity studies.

Tavaborole, a cyclized boronic acid, has been approved by the Food and Drug Administration for the topical treatment of toenail onychomycosis. This novel, low-molecular-weight pharmaceutical compound has broad-spectrum antifungal activity against dermatophytes, yeasts, and molds responsible for the disease. Tavaborole was tested in 2-year carcinogenicity studies in mice (once daily dermal administration) and rats (once daily by oral gavage) as part of the extensive nonclinical safety program. There was no evidence of tavaborole-related neoplasms observed in either study. Based on the data gathered from these 2 carcinogenicity studies, tavaborole is considered noncarcinogenic.