Efficacy and safety of topical terbinafine 10% solution (MOB-015) in the treatment of mild to moderate distal subungual onychomycosis: A randomized, multicenter, double-blind, vehicle-controlled phase 3 study

Penetration Profile of Terbinafine Compared to Amorolfine in Mycotic Human Toenails Quantified by Matrix-Assisted Laser Desorption Ionization-Fourier Transform Ion Cyclotron Resonance Imaging

INTRODUCTION

Amorolfine 5% lacquer is an established topical treatment for fungal infection of the nails. The success of topical therapy for onychomycosis depends on whether the permeated drug concentration in the deep nail bed is retained above the effective antifungal minimum inhibitory concentration (MIC). We compared the penetration profile of amorolfine and a new topical formula of terbinafine in human mycotic toenails using matrix-assisted laser desorption ionization mass spectrometry imaging-Fourier transform ion cyclotron resonance (MALDI-FTICR) imaging.

METHODS

Amorolfine 5% lacquer and terbinafine 7.8% lacquer were applied to mycotic nails (n = 17); nail sections were prepared, and MALDI-FTICR analysis was performed. Based on the MICs of amorolfine and terbinafine needed to kill 90% (MIC90) of Trichophyton rubrum, the fold differences between the MIC90 and the antifungal concentrations in the nails (the multiplicity of the MIC90) were calculated overall and for the keratin-unbound fractions.

RESULTS

Both amorolfine and terbinafine penetrated the entire thickness of the nail. The mean concentration across the entire nail section 3 h following terbinafine treatment was 1414 μg/g of tissue (equivalent to 4.9 mM) compared with 780 μg/g (2.5 mM) following amorolfine treatment (not significantly different; p = 0.878). The median multiplicity of the MIC90 was significantly higher in amorolfine- than terbinafine-treated nails overall (191 vs. 48; p = 0.010) and for the keratin-unbound fractions only (7.4 vs. 0.8; p = 0.002).

CONCLUSION

In this ex vivo study, MALDI-FTICR demonstrated that, although amorolfine 5% and terbinafine 7.8% had similar distribution profiles, both penetrating from the surface to the nail bed, the concentration of amorolfine in the nail was significantly higher than that of terbinafine relative to their respective MIC90 values. Clinical studies are required to determine whether these effects translate to a clinical difference in treatment success.

Efficacy of Laser Therapy in Comparison With Other Methods for the Treatment of Onychomycosis: A Systematic Review and Meta-Analysis

Onychomycosis, a fungal infection of the nails, presents a significant challenge in clinical management due to its chronic nature and resistance to conventional therapies. This study aims to evaluate the efficacy of laser therapy in treating onychomycosis compared to traditional methods such as terbinafine. A systematic review and meta-analysis were conducted to analyze existing literature on the subject. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) diagram illustrates the selection process of studies. Findings suggest that laser therapy demonstrates promising results in the treatment of onychomycosis, with comparable efficacy to terbinafine and fewer adverse effects. Further large-scale randomized controlled trials are warranted to validate these findings and establish laser therapy as a standard treatment option for onychomycosis.

Nail Society of India (NSI) Recommendations for Pharmacologic Therapy of Onychomycosis

Onychomycosis (OM) is the commonest cause of dystrophic nails, responsible for upto 50% of cases. Apart from significantly damaging the nails, quality of life, and self-image of the sufferer, it also acts as a reservoir of fungal infections carrying important implications for emerging recalcitrant dermatophytoses. Treatment of OM is based on guidelines released almost a decade back, in addition to published literature and personal preferences. Hence, an expert group of nail society of India (NSI) worked towards drafting these guidelines aimed at compiling recommendations for pharmacologic treatment of OM, based on scientific evidence, along with practical experience. The group did an extensive analysis of available English language literature on OM published during the period 2014-2022. The evidence compiled was graded and discussed to derive consensus recommendations for practice. Special focus was placed on combination therapies and adjunct therapies, including experience of members, to improve treatment outcomes.

Novel and Investigational Treatments for Onychomycosis

Onychomycosis is a common nail disease caused by fungi. The primary pathogens are dermatophytes; however, yeasts, non-dermatophyte moulds, and mixed fungal populations may also contribute to the development of a recalcitrant condition, usually accompanied by difficulties in everyday life and severe emotional stress. Treatment failure and relapse of the infection are the most frequent problems, though new issues have become the new challenges in the therapeutic approach to onychomycosis. Resistance to antifungals, an increasing number of comorbidities, and polydrug use among the ageing population are imperatives that impose a shift to safer drugs. Topical antifungals are considered less toxic and minimally interact with other drugs. The development of new topical drugs for onychomycosis is driven by the unmet need for effective agents with prolonged post-treatment disease-free time and a lack of systemic impact on the patients’ health. Efinaconazole, Tavaborole, and Luliconazole have been added to physicians’ weaponry during the last decade, though launched on the market of a limited number of countries. The pipeline is either developing new products (e.g., ME-1111 and NP213) with an appealing combination of pharmacokinetic, efficacy, and safety properties or reformulating old, well-known drugs (Terbinafine and Amphotericin B) by using new excipients as penetration enhancers.

Updated Perspectives on the Diagnosis and Management of Onychomycosis

Onychomycosis is the most common nail disease encountered in clinical practice and can cause pain, difficulty with ambulation, and psycho-social problems. A thorough history and physical examination, including dermoscopy, should be performed for each patient presenting with nail findings suggestive of onychomycosis. Several approaches are available for definitive diagnostic testing, including potassium hydroxide and microscopy, fungal culture, histopathology, polymerase chain reaction, or a combination of techniques. Confirmatory testing should be performed for each patient prior to initiating any antifungal therapies. There are several different therapeutic options available, including oral and topical medications as well as device-based treatments. Oral antifungals are generally recommended for moderate to severe onychomycosis and have higher cure rates, while topical antifungals are recommended for mild to moderate disease and have more favorable safety profiles. Oral terbinafine, itraconazole, and griseofulvin and topical ciclopirox 8% nail lacquer, efinaconazole 10% solution, and tavaborole 5% solution are approved by the Food and Drug Administration for treatment of onychomycosis in the United States and amorolfine 5% nail lacquer is approved in Europe. Laser treatment is approved in the United States for temporary increases in clear nail, but clinical results are suboptimal. Oral fluconazole is not approved in the United States for onychomycosis treatment, but is frequently used off-label with good efficacy. Several novel oral, topical, and over-the-counter therapies are currently under investigation. Physicians should consider the disease severity, infecting pathogen, medication safety, efficacy and cost, and patient age, comorbidities, medication history, and likelihood of compliance when determining management plans. Onychomycosis is a chronic disease with high recurrence rates and patients should be counseled on an appropriate plan to minimize recurrence risk following effective antifungal therapy.

Relevant insights into onychomycosis' pathogenesis related to the effectiveness topical treatment

Onychomycosis (OM) is a fungal infection, responsible for about 50% of nail diseases. OM has been attributed to the ability of fungi to naturally organize themselves into biofilms on nail surfaces. However, little is known about the exact role of the biofilm in the etiopathogenesis of OM, as well as its influence in the permeation of a topical treatment. The objectives of this study were to review the literature for topical OM treatments in clinical trials, assess the efficiency of these treatments, and discuss factors that could affect the success of these treatments. First, a systematic search of articles published in the MEDLINE database (PubMed) between January 2010 and December 2019 was conducted, focusing on drugs under clinical trials for the topical treatment of OM. Of the publications selected, it was clear that none of them had considered the fungi organized in biofilm. Therefore, we reflected on some important variables involved in OM, such as the nail structure and the mechanism of fungal invasion. Some methods, such as histopathologic analysis and spectroscopy techniques, were found to be effective in the detection of nail biofilm, and could be used in future drug permeation studies. This review allowed us to conclude that novel antifungals for the topical treatment of OM must consider the drug to permeate through biofilm. Natural products, such as propolis, seem strong candidates in this respect.

Efficacy of Lasers for the Management of Dermatophyte Toenail Onychomycosis

BACKGROUND

Onychomycosis is a chronic fungal nail infection caused predominantly by dermatophytes, and less commonly by nondermatophyte molds and Candida species. Onychomycosis treatment includes oral and topical antifungals, the efficacy of which is evaluated through randomized, double-blind, controlled trials for US Food and Drug Administration approval. The primary efficacy measure is complete cure (complete mycologic and clinical cure). The secondary measures are clinical cure (usually ≤10% involvement of target nail) and mycologic cure (negative microscopy and culture). Some lasers are US Food and Drug Administration approved for the mild temporary increase in clear nail; however, some practitioners attempt to use lasers to treat and cure onychomycosis.

METHODS

A systematic review of the literature was performed in July of 2020 to evaluate the efficacy rates demonstrated by randomized controlled trials of laser monotherapy for dermatophyte onychomycosis of the great toenail.

RESULTS

Randomized controlled trials assessing the efficacy of laser monotherapy for dermatophyte toenail onychomycosis are limited. Many studies measured cure rates by means of nails instead of patients, and performed only microscopy or culture, not both. Only one included study reported mycologic cure rate in patients as negative light microscopy and culture (0%). The combined clinical cure rates in short- and long-pulsed laser studies were 13.0%-16.7% and 25.9%, respectively. There was no study that reported the complete cure rate; however, one did report treatment success (mycologic cure [negative microscopy and culture] and ≤10% clinical involvement) in nails as 16.7%.

CONCLUSIONS

The effectiveness of lasers as a therapeutic intervention for dermatophyte toenail onychomycosis is limited based on complete, mycologic, and clinical cure rates. However, it may be possible to use different treatment parameters or lasers with a different wavelength to increase the efficacy. Lasers could be a potential management option for older patients and onychomycosis patients with coexisting conditions such as diabetes, liver, and/or kidney diseases for whom systemic antifungal agents are contraindicated or have failed.

Advances in Antifungal Drug Development: An Up-To-Date Mini Review

The utility of clinically available antifungals is limited by their narrow spectrum of activity, high toxicity, and emerging resistance. Antifungal drug discovery has always been a challenging area, since fungi and their human host are eukaryotes, making it difficult to identify unique targets for antifungals. Novel antifungals in clinical development include first-in-class agents, new structures for an established target, and formulation modifications to marketed antifungals, in addition to repurposed agents. Membrane interacting peptides and aromatherapy are gaining increased attention in the field. Immunotherapy is another promising treatment option, with antifungal antibodies advancing into clinical trials. Novel targets for antifungal therapy are also being discovered, allowing the design of new promising agents that may overcome the resistance issue. In this mini review, we will summarize the current status of antifungal drug pipelines in clinical stages, and the most recent advancements in preclinical antifungal drug development, with special focus on their chemistry.

Cure Rates of Control Interventions in Randomized Trials for Onychomycosis Treatments: A Systematic Review and Meta-Analysis

Background: The efficacy of antifungals for onychomycosis has been determined in randomized controlled trials (RCTs); interestingly their control arms have demonstrated some therapeutic effects. These controls constitute either placebos (inert pills) or vehicles (all but the antifungal component of the creams). The objective of this research was to determine (i) whether RCT controls exhibited statistically-relevant efficacy rates (i.e. beyond the "placebo effect"), (ii) whether oral and topical controls differed in their efficacies, and (iii) if the efficacy rates of the controls correlated with those of the active comparator associated with that control.

Methods: RCTs of oral and topical monotherapies for dermatophyte toenail onychomycosis were identified through a systematic literature search. For our meta-analyses of cure rates the double arcsine transformation was used. The N-1 chi squared test was used to determine whether the cure rates significantly differed between topical and oral controls. Correlation was investigated using Kendall rank correlation tests.

Results: The pooled mycological, complete, and clinical cure rates of all control interventions (n = 19 trials) were 9%, 1%, and 6%, respectively. The pooled efficacy rates for oral and topical controls were: mycological cure rate, 7% and 12% (p=0.0016); complete cure rate, 1% for both; and clinical cure rate, 4% and 8%, respectively (p=0.0033). For oral RCTs, the respective cure rates of the active therapies were not correlated with controls. However, for topical RCTs, as the mycological and clinical cure rates of the active therapy increased, so did those of the topical vehicle associated with the active therapy in question, and vice versa.

Conclusions: The topical vehicle cure rates were often higher than the oral placebo cure rates, likely due to the presence of non-antifungal chemicals (e.g. moisturizers, urea) with antifungal and debriding properties, which are not present in oral controls.

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