New pharmacotherapy for the treatment of onychomycosis: an update

Response surface methodological approach for optimization of photodynamic therapy of onychomycosis using chlorin e6 loaded nail penetration enhancer vesicles

Antimicrobial photodynamic inactivation (aPDI) has a tremendous potential as an alternative therapeutic modality to conventional antifungals in treatment of onychomycosis, yet the nail barrier properties and the deep-seated nature of fungi within the nails remain challenging. Therefore, the aim of this study was to prepare, optimize, and characterize Chorin e6 (Ce6) nail penetration enhancer containing vesicles (Ce6-nPEVs) and evaluate their photodynamic mediated effect against Trichophyton rubrum (T.rubrum); the main causative agent of onychomycosis. Optimization of the particle size and encapsulation efficiency of nPEVs was performed using a four-factor two-level full factorial design. The transungual delivery potential of the selected formulation was assessed in comparison with the free drug. The photodynamic treatment conditions for T.rubrum aPDI by free Ce6 was optimized using response surface methodology based on Box-Behnken design, and the aPDI effect of the selected Ce6-nPEVs was evaluated versus the free Ce6 at the optimized condition. Results showed that formulations exhibited high encapsulation efficiency for Ce6 ranging from 79.4 to 98%, particle sizes ranging from 225 to 859 nm, positive zeta potential values ranging from +30 to +70 mV, and viscosity ranging from 1.26 to 3.43 cP. The predominant parameters for maximizing the encapsulation efficiency and minimizing the particle size of Ce6-nPEVs were identified. The selected formulation showed 1.8-folds higher nail hydration and 2.3 folds improvement in percentage of Ce6 up-taken by nails compared to the free drug. Results of the microbiological study confirmed the reliability and adequacy of the Box-Behnken model, and delineated Ce6 concentration and incubation time as the significant model terms. Free Ce6 and Ce6-nPEVs showed an equipotent in vitro fungicidal effect on T.rubrum at the optimized conditions, however Ce6-nPEVs is expected to show a differential effect at the in vivo level where the advantage of the enhanced nail penetration feature will be demonstrated.

Photodynamic Therapy for the Treatment of Fungal Infections

Cutaneous fungal infections are common in humans and are associated with significant physical and psychological distress to patients. Although conventional topical and/or oral anti-fungal medications are commonly recommended treatments, drug resistance has emerged as a significant concern in this patient population, and safer, more efficacious, and cost-effective alternatives are warranted. Recent studies have reported effectiveness of photodynamic therapy (PDT) against fungal infections without severe adverse effects. In this review, we briefly discuss the mechanisms underlying PDT, current progress, adverse effects, and limitations of this treatment in the management of superficial and deep fungal infections.

Antifungal and antioxidant effect of the lachnophyllum ester, isolated from the essential oil of Baccharis trinervis (Lam.) Pers., against dermatophytes fungi

ABSTRACT Dermatophytes are hyaline fungi that parasitize the keratinized tissue of humans and animals causing mycotic infections. Natural products are promising molecules for the development of new antifungal drugs, due to the phenomenon of resistance and toxicity. This study reports the isolation and identification of lachnophyllum ester and evaluates its antioxidant, antifungal and modulatory activities against dermatophytes fungi. Lachnophyllum ester was obtained using a silica gel column chromatography of the essential oil from the aerial parts of Baccharis trinervis and analyzed by gas chromatography/mass spectrometry. Antimicrobial activity was determined by the broth microdilution method. The modulatory activity assays were performed by the checkerboard technique using lachnophyllum ester and ketoconazole as standard. The lachnophyllum ester exhibited good antioxidant activity as measured by a β-carotene/linoleic acid bleaching system, with 71.43% ± 0.01% inhibition rate. In addition, it showed antifungal activity against Trichophyton rubrum and Microsporum canis strains. In the modulatory assay, interaction between lachnophyllum ester and ketoconazole was synergistic, reducing the minimum inhibitory concentration (MIC) values of the antifungal drug and modulating its antifungal action against dermatophyte strains. In conclusion, lachnophyllum ester has been shown to act as a natural antioxidant compound, as well as an antimicrobial alternative against dermatophyte fungi of the genus Trichophyton and Microsporum.

Mechanistic Insights of Formulation Approaches for the Treatment of Nail Infection: Conventional and Novel Drug Delivery Approaches

Onychomycosis is a chronic disorder that is difficult to manage and hard to eradicate with perilous trends to relapse. Due to increased prevalence of HIV, use of immunosuppressant drugs and lifestyle-related factors, population affected with fungal infection of nail (Onychomycosis) happens to increase extensively in last two decades. Modalities available for the treatment of onychomycosis include systemically administered antifungals, mechanical procedures, and topical drug therapy. But the efficacy of the most of approaches to deliver drug at targeted site, i.e., deep-seated infected nail bed is limited due to compact and highly keratinized nail structure. A series of advanced formulation approaches, such as transfersomes, liposomes, nano/micro emulsion, nail lacquers etc., have been attempted to improve the drug penetration into nail plate more efficiently. The manuscript reviews these formulation approaches with their possible mechanisms by which they improve the drug penetration.Comparative analysis of available treatment modalities for onychomycosis has been provided with pros and cons of each alternatives. Additionally, ongoing research about the application of biological materials such as modified cationic antimicrobial peptides (AMPs), plant-derived proteins, and synthetic antimicrobial peptidomimetics have also been explored.

Improving cellular uptake of therapeutic entities through interaction with components of cell membrane

Efficient cellular delivery of biologically active molecules is one of the key factors that affect the discovery and development of novel drugs. The plasma membrane is the first barrier that prevents direct translocation of chemic entities, and thus obstructs their efficient intracellular delivery. Generally, hydrophilic small molecule drugs are poor permeability that reduce bioavailability and thus limit the clinic application. The cellular uptake of macromolecules and drug carriers is very inefficient without external assistance. Therefore, it is desirable to develop potent delivery systems for achieving effective intracellular delivery of chemic entities. Apart from of the types of delivery strategies, the composition of the cell membrane is critical for delivery efficiency due to the fact that cellular uptake is affected by the interaction between the chemical entity and the plasma membrane. In this review, we aimed to develop a profound understanding of the interactions between delivery systems and components of the plasma membrane. For the purpose, we attempt to present a broad overview of what delivery systems can be used to enhance the intracellular delivery of poorly permeable chemic entities, and how various delivery strategies are applied according to the components of plasma membrane.

Recent advances in therapies for onychomycosis and its management

Onychomycosis is the most common affliction of the nail. It may be caused by dermatophytes, yeasts, and non-dermatophyte molds. Traditionally, oral antifungal treatments have been used to treat the fungus, although they can be accompanied by side effects and drug interactions. Topical treatments provide an alternative modality, bypassing the systemic effects of oral drugs; recent research has centered on topical drug improvement and development. Physical and laser treatments are being used in conjunction with topicals, which may help penetrate the thick nail plate. In this review, techniques from all categories are outlined: both novel experimental approaches and progress and effectiveness of recently developed treatments. More long-term studies are required to determine the efficacy of various treatments, but cure rates are improved when patients adhere to treatments and follow preventative measures to avoid disease recurrence.

Cross-Linked Fluorescent Supramolecular Nanoparticles for Intradermal Controlled Release of Antifungal Drug-A Therapeutic Approach for Onychomycosis

The existing approaches to onychomycosis demonstrate limited success since the commonly used oral administration and topical cream only achieve temporary effective drug concentration at the fungal infection sites. An ideal therapeutic approach for onychomycosis should have (i) the ability to introduce antifungal drugs directly to the infected sites; (ii) finite intradermal sustainable release to maintain effective drug levels over prolonged time; (iii) a reporter system for monitoring maintenance of drug level; and (iv) minimum level of inflammatory responses at or around the fungal infection sites. To meet these expectations, we introduced ketoconazole-encapsulated cross-linked fluorescent supramolecular nanoparticles (KTZ⊂c-FSMNPs) as an intradermal controlled release solution for treating onychomycosis. A two-step synthetic approach was adopted to prepare a variety of KTZ⊂c-FSMNPs. Initial characterization revealed that 4800 nm KTZ⊂c-FSMNPs exhibited high KTZ encapsulation efficiency/capacity, optimal fluorescent property, and sustained KTZ release profile. Subsequently, 4800 nm KTZ⊂c-FSMNPs were chosen for in vivo studies using a mouse model, wherein the KTZ⊂c-FSMNPs were deposited intradermally via tattoo. The results obtained from (i) in vivo fluorescence imaging, (ii) high-performance liquid chromatography quantification of residual KTZ, (iii) matrix-assisted laser desorption/ionization mass spectrometry imaging mapping of KTZ distribution in intradermal regions around the tattoo site, and (iv) histology for assessment of local inflammatory responses and biocompatibility, suggest that 4800 nm KTZ⊂c-FSMNPs can serve as an effective treatment for onychomycosis.

Challenges and Opportunities in the Management of Onychomycosis

Onychomycosis is an increasingly common fungal nail infection, chiefly caused by dermatophyte fungi. The disease is notoriously difficult to treat due to the deep-seated nature of fungi within the nail plate, prolonged treatment requirements, poor patient adherence and frequent recurrences. Given the poor efficacy of currently available topical and systemic therapies, there is a renewed interest in exploring alternative treatment modalities for onychomycosis. Natural therapies, physical treatments and various combination therapies have all shown potential for the management of onychomycosis, though research on many of these methods is still in preliminary stages. Further large, well-designed, randomised controlled trials are necessary to confirm the efficacy of these novel treatments in order to make formal recommendations regarding their use in the management of onychomycosis.

Onychomycosis in the 21st Century: An Update on Diagnosis, Epidemiology, and Treatment

Onychomycosis accounts for 50% of all nail disease cases and is commonly caused by dermatophytes. Diabetes, human immunodeficiency virus, immunosuppression, obesity, smoking, and advancing age are predisposing factors of this fungal infection. Potassium hydroxide and culture are considered the current standard for diagnosing onychomycosis, revealing both fungal viability and species identification. Other diagnostic tests currently available include periodic acid-Schiff staining, polymerase chain reaction techniques, and fluorescent staining. Across 6 recently published epidemiology studies, the global prevalence of onychomycosis was estimated to be 5.5%, falling within the range of previously reported estimates (2%-8%). Newly approved onychomycosis treatments include efinaconazole, tavaborole, and laser therapy with lasers only approved to temporarily increase the amount of clear nail. Additional onychomycosis treatments being investigated include iontophoresis and photodynamic therapy with small open-label studies reported thus far. Preventative strategies, to help decrease recurrence and reinfection rates, include sanitisation of footwear and prophylactic topical antifungal agents.

Self-controlled Study of Onychomycosis Treated with Long-pulsed Nd:YAG 1064-nm Laser Combined with Itraconazole

Background:

Onychomycosis is a fungal infection of the nail plate and subungual area. In this study, we examined the efficacy of laser treatment using self-controlled study programs involving a long-pulsed Nd:YAG 1064-nm laser combined with oral medication.

Methods:

Self-controlled strategies were followed in this study. The patients received treatment with oral itraconazole in conjunction with long-pulsed Nd:YAG 1064-nm laser treatment at the nails of the unilateral limb once a week for a total of four times. A total of 84 affected nails were divided into Group A (mild to moderate) and Group B (severe) according to disease severity. Affected nails with the same Scoring Clinical Index for Onychomycosis scores were selected to compare the therapeutic effects of the pure medication treatment group and the combination treatment group with a 24-week follow-up period.

Results:

In Group A, at the 8^th, 16^th, and 24^th weeks of follow-up, the efficacies in the pure medication treatment group were 81.0%, 81.0%, and 90.5%, respectively, while those in the combination treatment group were 100%, 95.2%, and 90.5%, respectively. The differences between groups were not significant (8^th week: χ² = 4.421, P > 0.05; 16^th week: χ² = 2.043, P > 0.05; 24^th week: χ² = 0.00, P > 0.05). In Group B, at the 8^th, 16^th, and 24^th weeks of follow-up, the efficacies in the pure medication treatment group were 61.9%, 66.7%, and 52.4%, respectively, while those in the combination treatment group were 95.2%, 90.5%, and 100%, respectively. The differences between groups at the 8^th and 24^th weeks of follow-up were statistically significant (8^th week: χ² = 6.929, P < 0.05; 24^th week: χ² = 13.125, P < 0.05).

Conclusions:

For patients with mild or moderate onychomycosis, we recommended a pure medication treatment or combination treatment with medication and laser. For those patients with severe onychomycosis, we recommended a combination of medication and laser therapy.

The Effect of Long-Pulsed Nd:YAG Laser for the Treatment of Onychomycosis

BACKGROUND

Topical onychomycosis therapies are usually inadequate, and patient compliance to systemic therapies is poor. Recently, interest in laser therapy for the treatment of onychomycosis has increased. We sought to investigate the efficacy of long-pulsed Nd:YAG laser therapy for onychomycosis.

METHODS

Thirty patients with mycologically confirmed onychomycosis received long-pulsed 1064-nm Nd:YAG laser therapy, moving the beam in a spiral pattern over the whole nail plate two times, with a 1-minute pause between passes. Laser therapy was performed with a spot diameter of 4 mm at a speed of 25 mm/sec once weekly for 4 weeks using fluencies ranging from 40 to 60 J/cm², depending on the thickness of the nail plate. Patients were evaluated in terms of clinical improvement and mycologic cure.

RESULTS

Thirty patients started and 15 completed the study. Mycologic cure was achieved in nine patients (60%), of whom eight (89%) were infected with Trichophyton sp. Complete clinical improvement was achieved in seven patients (47%), all of whom were infected with Trichophyton sp. Mycologic cure was not achieved in one of two patients infected with Epidermophyton or in either patient in whom the agent was Candida or Aspergillus; complete clinical improvement did not occur in any of these patients. No serious adverse events were observed.

CONCLUSIONS

Based on these results, long-pulsed Nd:YAG laser can be used as an effective treatment for onychomycosis, but further studies are needed to draw firmer conclusions.

Tinea Unguium: Diagnosis and Treatment in Practice

Onychomycosis is caused by dermatophytes, yeasts or non-dermatophyte molds; when caused by dermatophytes, it is called tinea unguium. The main etiological agents are Trichophyton rubrum and Trichophyton interdigitale. The most frequent types are distal and lateral subungual onychomycosis. Diagnosis usually requires mycological laboratory confirmation. Dermoscopy can be helpful and also biopsy is an excellent diagnostic method in uncommon cases or when mycological test is negative. Treatment must be chosen according to clinical type, number of affected nails and severity. The goal for antifungal therapy is the clearing of clinical signs or mycological cure.

Novel investigational therapies for onychomycosis: an update

INTRODUCTION

Onychomycosis is an infection of the nail plate that is prevalent among the ageing population. Onychomycosis is difficult to treat with low initial cure rates, high rates of relapse, and reinfection. Present treatment options include oral and topical therapies, with oral therapies yielding better results. However, there has been a greater emphasis on the development of topical antifungal therapies as they have fewer side effects and drug interactions.

AREAS COVERED

This review summarizes new and reformulated drugs. Results from in vitro studies to Phase III clinical trials are discussed. Novel drugs include: the oral azole VT-1161, the topical azole efinaconazole, the benzoxaborole tavaborole, reformulations of terbinafine P-3058 and LI-P, novel inhibitor of succinate dehydrogenase ME1111, and off-label use of tazarotene. Enhanced permeation of the morpholine amorolfine through the nail plate is also discussed using ultraviolet (UV) curable gels, and a fractional CO2 laser.

EXPERT OPINION

Novel topical antifungals and the reformulation of current antifungals have demonstrated marked improvement in nail penetration. Current research has an emphasis on topical therapies due to their minimized risk for adverse effects and higher patient demand. Nevertheless, few topical agents have surfaced in the past few years and the investigation of efficacious combination therapies may become more important.

Onychomycosis: Potential of Nail Lacquers in Transungual Delivery of Antifungals

Onychomycosis constitutes the most common fungal infection of the nail (skin beneath the nail bed) that affects the finger as well as toe nails. It is an infection that is initiated by yeasts, dermatophytes, and nondermatophyte molds. Nail lacquers are topical solutions intended only for use on fingernails as well as toenails and have been found to be useful in the treatment of onychomycosis. Thus, in the present review an attempt has been made to focus on the treatment aspects of onychomycosis and the ungual delivery of antifungals via nail lacquer. Several patents issued on nail lacquer till date have also been discussed. Penetration efficiency was assessed by several researchers across the human nail plate to investigate the potentiality of nail lacquer based formulations. Various clinical trials have also been conducted in order to evaluate the safety and efficacy of nail lacquers in delivering antifungal agents. Thus, it can be concluded that nail lacquer based preparations are efficacious and stable formulations. These possess tremendous potential for clinical topical application to the nail bed in the treatment of onychomycosis.

Application of Hansen Solubility Parameters to predict drug-nail interactions, which can assist the design of nail medicines

We hypothesised that Hansen Solubility Parameters (HSPs) can be used to predict drug-nail affinities. Our aims were to: (i) determine the HSPs (δD, δP, δH) of the nail plate, the hoof membrane (a model for the nail plate), and of the drugs terbinafine HCl, amorolfine HCl, ciclopirox olamine and efinaconazole, by measuring their swelling/solubility in organic liquids, (ii) predict nail-drug interactions by comparing drug and nail HSPs, and (iii) evaluate the accuracy of these predictions using literature reports of experimentally-determined affinities of these drugs for keratin, the main constituent of the nail plate and hoof. Many solvents caused no change in the mass of nail plates, a few solvents deswelled the nail, while others swelled the nail to varying extents. Fingernail and toenail HSPs were almost the same, while hoof HSPs were similar, except for a slightly lower δP. High nail-terbinafine HCl, nail-amorolfine HCl and nail-ciclopirox olamine affinities, and low nail-efinaconazole affinities were then predicted, and found to accurately match experimental reports of these drugs' affinities to keratin. We therefore propose that drug and nail Hansen Solubility Parameters may be used to predict drug-nail interactions, and that these results can assist in the design of drugs for the treatment of nail diseases, such as onychomycosis and psoriasis. To our knowledge, this is the first report of the application of HSPs in ungual research.

Spotlight on tavaborole for the treatment of onychomycosis

Onychomycosis is a fungal nail plate infection that has been increasing in prevalence. A variety of oral and topical anti-fungal agents are currently available but their use is limited by their adverse effect profile, drug–drug interactions, and limited efficacy. Therefore, there is a great need for newer anti-fungal agents. Tavaborole is one of these newer agents and was approved by the US Food and Drug Administration in July 2014 for the topical treatment of mild to moderate toenail onychomycosis. Tavaborole is a novel, boron-based anti-fungal agent with greater nail plate penetration than its predecessors, due to its smaller molecular weight. It has proven through several Phase II and III trials that it can be a safe and effective topical agent for the treatment of mild to moderate toenail onychomycosis without the need for debridement. In this paper, we review the landscape of topical and systemic treatment of onychomycosis, with particular attention to the pharmacokinetics, safety, and efficacy of topical tavaborole.

Essential Oils for Treatment for Onychomycosis: A Mini-Review

Onychomycosis are fungal infections affecting finger and toenails mainly caused by dermatophyte fungi and some Candida species. Low cure rates and frequent recurrence, development of a fungal resistance front to various antimicrobial agents topical and systemic, and an ineffective topical treatment make onychomycosis difficult to treat. Essential oils are excellent candidates for the topical treatment for onychomycosis because the development of resistance by fungi is rare, and the presence of side effects is low. They are composed of a complex variety of compounds, mainly terpenes, with low molecular weight, which may easily penetrate into the nail plate, finding the fungi elements. The complex mixture confers a broad antifungal spectrum of action, through interaction with biological membranes, interference in radical and enzymatic reaction of fungi cells. Essential oils may become the source of new therapeutic molecules, and the use of an essential oil incorporated into a topical formulation is an interesting, safe, and effective alternative for the treatment for onychomycosis. However, studies are needed to evaluate the efficacy of essential oils in the treatment for onychomycosis in vivo. This mini-review aims to present the potential use of essential oils for the treatment for onychomycosis, focusing on the last decade.