Spotlight on tavaborole for the treatment of onychomycosis

Antifungal Selection for the Treatment of Onychomycosis: Patient Considerations and Outcomes

Onychomycosis, a common fungal nail infection, affects >20% of adults over age 60 and >50% of people over age 70. Onychomycosis may cause pain, psychosocial problems, and secondary infections, therefore meriting treatment. This review describes the range of treatment modalities, including FDA-approved systemic drugs and topical therapies. Additionally, new and emerging oral and topical therapies are discussed. We emphasize the importance of tailoring onychomycosis therapy to individual patient characteristics, comorbidities, preferences, extent of nail involvement, and fungal species, such that physicians may optimize treatment outcomes, patient satisfaction, and safety.

Computational Insight into Substrate-Induced Conformational Changes in Methionyl-tRNA Synthetase of Mycobacterium Tuberculosis

Tuberculosis caused by Mycobacterium tuberculosis (M.tb) has killed millions worldwide. Antibiotic resistance leads to the ineffectiveness of the current therapies. Aminoacyl tRNA synthetase (aaRS) class of proteins involved in protein synthesis are promising bacterial targets for developing new therapies. Here, we carried out a systematic comparative study on the aaRS sequences from M.tb and human. We listed important M.tb aaRS that could be explored as potential M.tb targets alongside the detailed conformational space analysis of methionyl-tRNA synthetase (MetRS) in apo- and substrate-bound form, which is among the proposed targets. Understanding the conformational dynamics is central to the mechanistic understanding of MetRS, as the substrate binding leads to the conformational changes causing the reaction to proceed. We performed the most complete simulation study of M.tb MetRS for 6 microseconds (2 systems × 3 runs × 1 microsecond) in the apo and substrate-bound states. Interestingly, we observed differential features, showing comparatively large dynamics for the holo simulations, whereas the apo structures became slightly compact with reduced solvent exposed area. In contrast, the ligand size decreased significantly in holo structures possibly to relax ligand conformation. Our findings correlate with experimental studies, thus validating our protocol. Adenosine monophosphate moiety of the substrate exhibited quite higher fluctuations than the methionine. His21 and Lys54 were found to be the important residues forming prominent hydrogen bond and salt-bridge interactions with the ligand. The ligand-protein affinity decreased during simulations as computed by MMGBSA analysis over the last 500 ns trajectories, which indicates the conformational changes upon ligand binding. These differential features could be further explored for designing new M.tb inhibitors.

A Red-Emitting Fluorescence Sensor for Detecting Boronic Acid-Containing Agents in Cells

The amount and localization of boron-10 atoms delivered into tumor cells determines the therapeutic effect of boron neutron capture therapy (BNCT) and, consequently, efforts have been directed to develop fluorescence sensors to detect intracellular boronic acid compounds. Currently, these sensors are blue-emitting and hence are impracticable for co-staining with nucleus staining reagents, such as DAPI and Hoechst 33342. Here, we designed and synthesized a novel fluorescence boron sensor, BS-631, that emits fluorescence with a maximum emission wavelength of 631 nm after reaction with the clinically available boronic acid agent, 4-borono-l-phenylalanine (BPA). BS-631 quantitatively detected BPA with sufficiently high sensitivity (detection limit = 19.6 µM) for evaluating BNCT agents. Furthermore, BS-631 did not emit fluorescence after incubation with metal cations. Notably, red-emitting BS-631 could easily and clearly visualize the localization of BPA within cells with nuclei co-stained using Hoechst 33342. This study highlights the promising properties of BS-631 as a versatile boron sensor for evaluating and analyzing boronic acid agents in cancer therapy.

Fluorescent-Oxaboroles: Synthesis and Optical Property by Sugar Recognition

The optical property of fluorescent unit-conjugated aliphatic oxaboroles has been investigated. The oxaboroles provide good fluorescence quantum yields and selective recognition toward D-ribose and D-ribose containing molecules. The molecular recognition induced significant fluorescence quenching. The property of the boroles showed the possibility of the boron-based nicotinamide adenine dinucleotide (NAD) sensor probe.

A Mycological and Molecular Epidemiologic Study on Onychomycosis and Determination In Vitro Susceptibilities of Isolated Fungal Strains to Conventional and New Antifungals

Background

Onychomycosis is one of the most common and recurrent dermatological diseases worldwide. The antimycotic activity of prescribed medications varies according to the causative agents, and treatment failure rates exceeding 30%. This study aimed to assess the epidemiological profile of onychomycosis in Iran. Also, the susceptibilities to conventional and new antifungals were investigated.

Methods

In this descriptive cross-sectional study, during the period of 18 months starting from September 2019 until March 2020, 594 nail specimens were obtained from patients who presented nail changes compatible with a clinical diagnosis of onychomycosis. The patients were referred from different cities, including Tehran, Kermanshah, Arak, Kashan, Rasht, Qom, Urmia, Zahedan, Hamadan, Zanjan, Borujerd, Bushehr, and Yazd. All the samples were subjected to microscopic examination and fungal culture. Fungi identified were confirmed through the PCR-sequencing method. The susceptibility to itraconazole, fluconazole, terbinafine, griseofulvin, posaconazole, ravuconazole, efinaconazole, luliconazole, and tavaborole was evaluated according to the Clinical and Laboratory Standards Institute (CLSI) guidelines, document M38-A2 for filamentous fungi, and document M27-A3 for yeasts.

Results

594 patients were included. Of these, in 179 cases (30.1%) (95% CI:0.3 ± 0.037) onychomycosis was confirmed. The majority of patients were ≥ 60 years of age (n=58, 32.6%) and female (n=113, 63.1%). Saprophytic fungi accounted for the vast majority of the nail isolates (n=92, 51.4%) (95% CI:0.051 ± 0.0.073), followed by dermatophytes (n=45, 25.1%) (95% CI:0.25 ± 0.063), and yeasts (n=42, 23.5%) (95% CI:0.23 ± 0.061). Diabetes mellitus (77.3%), hypothyroidism (18.2%), and solid tumors (4.5%) were documented as the most prevalent underlying conditions. Antifungal susceptibility testing was performed against 60 fungal isolates (20 each of Candida species, saprophytic fungi, and dermatophytes). Efinaconazole, ravuconazole, and luliconazole were the most active agents against Candida species. Also, luliconazole, posaconazole, and efinaconazole were most potent against dermatophytes. Luliconazole had the greatest antifungal activity against saprophytic fungi.

Conclusions

The prevalence of onychomycosis in Iranian patients was relatively high. LUL exhibited potent antifungal activity against the three groups of fungi tested, determining its broad-spectrum antimycotic activity and its probable use as the first-line therapy for onychomycosis.

The Success of Topical Treatment of Onychomycosis Seems to Be Influenced by Fungal Features

Aim

To evaluate the topical treatment of onychomycosis using a 10% hydroalcoholic propolis extract (PE) in two aleatorily chosen patients and analyze possible risk factors from hosts including some particularities of the isolated fungi that may justify the outcomes achieved.

Materials and Methods

A topical treatment, with PE, was started in two cases of toe onychomycosis due to T. rubrum. The in vitro PE antifungal activity against these isolates was confirmed. Moreover, the ability of the fungi to infect the human nail was evaluated also in an ex vivo study, analyzed by histopathology.

Results

Within four months, both patients showed evident improvement, but with different outcomes. The possible host-related risk factors justifying the poorer outcome in patient 1 include a longer duration time of onychomycosis (50 years). Some particularities in the T. rubrum strain isolated from this patient in relation to that found in patient 2 were observed: (1) the hypha morphology suggesting a major adaptation of the fungus to the host; (2) a 16 times greater propolis concentration was required in vitro; and (3) a faster ability to start a growth using the nail as the only nutritional source. Additionally, this isolate was more efficient in producing a biofilm on the nail surface.

Conclusions

A partial clinical and complete mycological cure for the two patients was achieved after four months of PE daily use. Despite a complete recovery, a different outcome was observed between both cases. A more persistent onychomycosis, added to greater fungal potential to produce biofilm on the nail, seems to influence greatly the success of a topical treatment with PE.

Identification of Resistance Determinants for a Promising Antileishmanial Oxaborole Series

Current treatment options for visceral leishmaniasis have several drawbacks, and clinicians are confronted with an increasing number of treatment failures. To overcome this, the Drugs for Neglected Diseases initiative (DNDi) has invested in the development of novel antileishmanial leads, including a very promising class of oxaboroles. The mode of action/resistance of this series to Leishmania is still unknown and may be important for its further development and implementation. Repeated in vivo drug exposure and an in vitro selection procedure on both extracellular promastigote and intracellular amastigote stages were both unable to select for resistance. The use of specific inhibitors for ABC-transporters could not demonstrate the putative involvement of efflux pumps. Selection experiments and inhibitor studies, therefore, suggest that resistance to oxaboroles may not emerge readily in the field. The selection of a genome-wide cosmid library coupled to next-generation sequencing (Cos-seq) was used to identify resistance determinants and putative targets. This resulted in the identification of a highly enriched cosmid, harboring genes of chromosome 2 that confer a subtly increased resistance to the oxaboroles tested. Moderately enriched cosmids encompassing a region of chromosome 34 contained the cleavage and polyadenylation specificity factor (cpsf) gene, encoding the molecular target of several related benzoxaboroles in other organisms.

Review: Glucose-sensitive insulin

BACKGROUND

Hypoglycemia, the condition of low blood sugar, is a common occurance in people with diabetes using insulin therapy. Protecting against hypoglycaemia by engineering an insulin preparation that can auto-adjust its biological activity to fluctuating blood glucose levels has been pursued since the 1970s, but despite numerous publications, no system that works well enough for practical use has reached clinical practise.

SCOPE OF REVIEW

This review will summarise and scrutinise known approaches for producing glucose-sensitive insulin therapies. Notably, systems described in patent applications will be extensively covered, which has not been the case for earlier reviews of this area.

MAJOR CONCLUSIONS

The vast majority of published systems are not suitable for product development, but a few glucose-sensitive insulin concepts have recently reached clinical trials, and there is hope that glucose-sensitive insulin will become available to people with diabetes in the near future.

In Vitro Resistance and Evolution of Resistance to Tavaborole in Trichophyton rubrum

Tavaborole is currently used in the topical treatment of onychomycosis. In this study, we analyzed the in vitro emergence/evolution of resistance against tavaborole in Trichophyton rubrum When T. rubrum strains were propagated on media containing the MIC of tavaborole, spontaneous resistant mutants were isolated at a frequency of 10^-8 The frequency was almost 100-fold higher following fungal growth in the presence of a subinhibitory tavaborole concentration (0.5-fold the MIC) for 10 transfers. All collected mutants showed similar 4- to 8-fold increases in the drug MIC. No cross-resistance to other antifungals was evident.

Exploiting evolutionary trade-offs for posttreatment management of drug-resistant populations

Antibiotic resistance frequently evolves through fitness trade-offs in which the genetic alterations that confer resistance to a drug can also cause growth defects in resistant cells. Here, through experimental evolution in a microfluidics-based turbidostat, we demonstrate that antibiotic-resistant cells can be efficiently inhibited by amplifying the fitness costs associated with drug-resistance evolution. Using tavaborole-resistant Escherichia coli as a model, we show that genetic mutations in leucyl-tRNA synthetase (that underlie tavaborole resistance) make resistant cells intolerant to norvaline, a chemical analog of leucine that is mistakenly used by tavaborole-resistant cells for protein synthesis. We then show that tavaborole-sensitive cells quickly outcompete tavaborole-resistant cells in the presence of norvaline due to the amplified cost of the molecular defect of tavaborole resistance. This finding illustrates that understanding molecular mechanisms of drug resistance allows us to effectively amplify even small evolutionary vulnerabilities of resistant cells to potentially enhance or enable adaptive therapies by accelerating posttreatment competition between resistant and susceptible cells.

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.

Dimeric boroles: effective sources of monomeric boroles for heterocycle synthesis

Dimeric boroles as thermal sources of monomers.

Monomeric boroles have been gaining attention as reagents for the synthesis of heterocycles due to their ability to insert atoms into the BC₄ ring in a single step. Although unique boron frameworks can be accessed via this methodology, the products feature aryl substitution on the carbon centers as steric bulk is required to preclude borole dimerization. This work demonstrates that insertion chemistry is possible with Diels–Alder dimeric boroles and that such reactivity is not exclusive to monomeric boroles with bulky groups. With 1-phenyl-2,3,4,5-tetramethylborole dimer, the formal 1,1-insertion of a nitrene and sulfur generate the six-membered aromatic 1,2-azaborine and 1,2-thiaborine, respectively. The isolation of the 1,2-thiaborine enabled the synthesis of an η⁶-chromium complex. Benzophenone and diphenylketene readily insert a CO unit to generate BOC₅ seven-membered rings confirming dimeric boroles can serve as monomeric synthons in 1,2-insertion reactions. An epoxide did not furnish the anticipated eight-membered BOC₆ ring, instead provided a bicyclic system with a BOC₃ ring. The insertion chemistry was demonstrated with two other borole dimers featuring different substitution with diphenylketene as a substrate. This work elevates borole insertion chemistry to a new level to access products that do not require bulky substitution.

ONYCHOMYCOSIS: A Review of New and Emerging Topical and Device-based Treatments

Onychomycosis is a challenging nail condition to treat. The gold standard treatment relies on long-term systemic therapy, which carries risks of potential side effects and drug interactions. Topical alternatives exist; however, treatment outcomes remain disappointing. In this article, we review newer topical formulations that are approved by the United States Food and Drug Administration, as well as other topical drugs that are still undergoing clinical trials. Lasers and energy-based devices have also been used for the treatment of onychomycosis; however, standardized parameters and clear treatment endpoints have yet to be specified. Currently, device-based therapies are considered as options for improving the cosmetic appearance of nails. The use of lasers to improve the penetration of topical antifungal treatments as possible combination treatments is also reviewed.

Pharmacy Technicians and Improving Onychomycosis Treatment Outcomes

Objective: To provide an overview of onychomycosis and current treatments and to identify opportunities for pharmacy technicians to improve treatment outcomes. Data Sources: A MEDLINE/PubMed search (1966 to October 2018) was performed using search terms designed to identify English-language articles on onychomycosis diagnosis, treatment, and prevention, as well as articles on the impact of pharmacy technicians on onychomycosis outcomes and the use of pharmacy technicians to improve treatment adherence. Study Selection and Data Extraction: Review articles and clinical studies describing onychomycosis, risk factors, treatment efficacy, and prevention of recurrent infections were included. Data Synthesis: Although no articles on the impact of pharmacy technicians in the treatment of onychomycosis were found, the importance of treatment adherence on positive outcomes highlights a potential role of pharmacy technicians. Pharmacy technicians can identify patients with potential onychomycosis based on questions about over-the-counter products and refer patients to the pharmacist for counseling on treatment. Pharmacy technicians can also reinforce treatment adherence at refill visits. Conclusions: Pharmacy technicians can have a positive impact on onychomycosis treatment outcomes by addressing barriers to successful treatment and promoting treatment adherence.

Synthesis and biological evaluation of aminothiazoles against Histoplasma capsulatum and Cryptococcus neoformans

The design and synthesis of a library of forty novel 2-aminoazole analogues as well as their evaluation as antifungal compounds against Histoplasma capsulatum and Cryptococcus neoformans is described. These structures were derived from N-[5-(1-naphthalenylmethyl)-2-thiazolyl]cyclohexanecarboxamide (41F5), a fungistatic agent previously identified through phenotypic screening (Antimicrob Agents Chemother. 2013;57:4349). Modifications to improve potency and water-solubility of 41F5 focused primarily on the 5-naphthalenyl group, the thiazole core, and the methylene linker between these two structural elements. In general, compounds with lipophilic [5+6] bicyclic ring systems, such as the 7-benzothiophenyl- and 4-indanyl groups, at the 5-position were 2-3 times more active against both fungal species as compared to 41F5. Also, introduction of a carbonyl group at the methylene linker of 41F5 resulted in a 2-3-fold increase in potency. These highly active compounds also showed generally low toxicities against murine P388D1 macrophages resulting in selectivity indices ranging from 63 to >200. Compounds that were highly active against fluconazole-sensitive C. neoformans strains had almost identical activity against fluconazole-resistant variants of this fungus indicating that 14α-demethylase is not their molecular target. Highly active compounds also retained activity against H. capsulatum phagocytosed into P388D1 macrophages.

Phenylboronic Acid Templated Gold Nanoclusters for Mucin Detection Using a Smartphone-Based Device and Targeted Cancer Cell Theranostics

A phenylboronic acid templated gold nanocluster probe was developed to detect biomarker mucin by a noninvasive fluorescence-based method using a point-of-care smartphone-based fluorescence detection device. The gold nanocluster probe is able to detect mucin specifically. The same probe was applied for in vitro targeted bioimaging of HeLa and Hep G2 cancer cells, and it demonstrated specific therapeutic effects toward cancer cells as well as multicellular tumor spheroids imparting theranostic properties. The module is found to be more effective toward HeLa cells, and a pathway of cell death was established using flow-cytometry-based assays.

Development and Elucidation of a Novel Fluorescent Boron-Sensor for the Analysis of Boronic Acid-Containing Compounds

Novel boron-containing drugs have recently been suggested as a new class of pharmaceuticals. However, the majority of current boron-detection techniques require expensive facilities and/or tedious pretreatment methods. Thus, to develop a novel and convenient detection method for boron-based pharmaceuticals, imine-type boron-chelating-ligands were previously synthesized for use in a fluorescent sensor for boronic acid containing compounds. However, the fluorescence quantum yield of the imine-type sensor was particularly low, and the sensor was easily decomposed in aqueous media. Thus, in this paper, we report the development of a novel, convenient, and stable fluorescent boron-sensor based on O- and N-chelation (i.e., 2-(pyridine-2yl)phenol), and a corresponding method for the quantitative and qualitative detection of boronic acid-containing compounds using this commercially available sensor is presented.

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.