Is there a need for new antifungal agents?

Preclinical Pharmacokinetic/Pharmacodynamic Studies and Clinical Trials in the Drug Development Process of EMA-Approved Antifungal Agents: A Review

Antifungal drug development is essential as invasive fungal disease is still associated with a very high mortality rate and the emergence of resistant species in the last decade. In Europe, the European Medical Agency (EMA) approves antifungals and publishes the European Public Assessment Report (EPAR) including the information leading up to the authorisation. We looked at EMA-approved antifungals and their reports within the last 23 years. We focused primarily on the role of pharmacokinetic/pharmacodynamic indices in antifungal development and the level of information depicted in their corresponding report. Furthermore, we investigated guidelines applicable to the development process at the time and compared the content with a focus on pharmacokinetic/pharmacodynamic studies and preclinical requirements. Since 2000, six new antifungal substances have been authorised. Most were authorised for treatment of Candida infections or Aspergillus infections but also included rarer pathogens. Pharmacokinetic/pharmacodynamic indices were scarcely investigated and/or mentioned in the report. Current antifungal EMA guidelines started emphasising investigating pharmacokinetic/pharmacodynamic indices in 2010 and then again in 2016. It remains to be seen how this translates into the authorisation process for new antifungals.

The Emergence of N. sativa L. as a Green Antifungal Agent

BACKGROUND

Nigella sativa L. has been widely used in the Unani, Ayurveda, Chinese, and Arabic medicine systems and has a long history of medicinal and folk uses. Several phytoconstituents of the plant are reported to have excellent therapeutic properties. In-vitro and in-vivo studies have revealed that seed oil and thymoquinone have excellent inhibitory efficacy on a wide range of both pathogenic and non-pathogenic fungi.

OBJECTIVE

The present review aims to undertake a comprehensive and systematic evaluation of the antifungal effects of different phytochemical constituents of black cumin.

METHOD

An exhaustive database retrieval was conducted on PubMed, Scopus, ISI Web of Science, SciFinder, Google Scholar, and CABI to collect scientific information about the antifungal activity of N. sativa L. with 1990 to 2023 as a reference range using 'Nigella sativa,' 'Nigella oil,' 'antifungal uses,' 'dermatophytic fungi,' 'candidiasis,' 'anti-aflatoxin,' 'anti-biofilm' and 'biological activity' as the keywords.

RESULTS

Black cumin seeds, as well as the extract of aerial parts, were found to exhibit strong antifungal activity against a wide range of fungi. Among the active compounds, thymoquinone exhibited the most potent antifungal effect. Several recent studies proved that black cumin inhibits biofilm formation and growth.

CONCLUSION

The review provides an in-depth analysis of the antifungal activity of black cumin. This work emphasizes the need to expand studies on this plant to exploit its antifungal properties for biomedical applications.

Antidermatophytic quinolizidine alkaloids from Calpurnia aurea subsp. aurea (Aiton) Benth

From the leaves and stem bark of the Kenyan medicinal plant Calpurnia aurea subsp. aurea, four previously undescribed quinolizidine alkaloids namely, 2β-methoxy-13α-O-(2'-pyrrolylcarbonyl) virgiline, 2α-methoxy-13β-O-(2'-pyrrolylcarbonyl) virgiline, 3α-O-angelate-2β-hydroxy-13α-O-(2'-pyrrolylcarbonyl) virgiline, 2,3-dehydro-virgiline were isolated together with four known ones. Structural elucidation of the compounds was based on 1D and 2D NMR spectroscopy and mass spectrometry. Their relative configurations were determined by NOESY correlations and literature. The quinolizidine alkaloids were tested against Trichophyton rubrum, Trichophyton interdigitale, Trichophyton benhamiae, Microsporum canis and Nannizzia gypsea, common causative agents of most of the tinea infections in human. All the isolated quinolizidine alkaloids exhibited antidermatophytic activity with MIC ranging from 37.5 μg/ml to 300 μg/ml.

Prokaryotic expression of human-sourced and zebrafish-sourced protein kinase A alpha catalytic subunits combined with in vitro and in silico assay

The extensively studied cAMP-dependent protein kinase A (PKA) is involved in the regulation of critical cell processes, including metabolism, gene expression, and cell proliferation. Therefore, PKA has been viewed increasingly as potential target for variety of drugs and environmental endocrine disruptors. Consequentially, the preparation of PKA protein became an important initial step for the subsequent exploration of PKA's character in endocrine disrupting effects of pesticides. To investigate PKA protein, which is potential to be the environmental endocrine toxicity target of triazole fungicides, a strategy to heterologously express protein kinase A catalytic alpha subunit of human (hPKAcα) and zebrafish (zPKAcα) in Escherichia coli (E. coli) BL21(DE3) host cells was demonstrated. After optimizing conditions and protein purification, we successfully obtained enzymatically active hPKAcα and zPKAcα. Western blot analysis indicated that the recombinant hPKAcα and zPKAcα still retained their characteristic antigenicity and binding activity, while in vitro kinase activity assays revealed that the recombinant hPKAcα and zPKAcα maintained enzyme activity. By in silico methods including homology modelling and molecular docking, the affinity of ligands and the models of hPKAcα and zPKAcα were further tested. The present study offered a valuable method to achieve the prokaryotic expression of a eukaryotic protein kinase and laid a foundation to facilitate further investigation of toxicological target of triazole pesticides.

Sophorolipid Biosurfactant Can Control Cutaneous Dermatophytosis Caused by Trichophyton mentagrophytes

Trichophyton mentagrophytes, a zoophilic species, is one of the most frequently isolated dermatophytes in many parts of the world. This study investigated the efficacy of a sophorolipid (SL-YS3) produced by Rhodotorula babjevae YS3 against dermatophytosis caused by T. mentagrophytes. SL-YS3 was characterized by gas chromatography–mass spectrometry (GC–MS) and ultra-performance liquid chromatography, coupled with electrospray mass spectrometry (UPLC-ESI-MS). SL-YS3 comprised of six different fatty acids as the hydrophobic components of constituent congeners and sophorose as the hydrophilic component. Inhibitory effects of purified SL-YS3 against hyphal growth was found to be 85% at a 2 mg ml^–1 concentration, and MIC was 1 mg ml^–1. Microscopic examination with scanning electron microscopy (SEM), atomic force microscopy, and confocal laser scanning microscopy (CLSM) revealed that SL-YS3 exerts its effect by disrupting cell membrane integrity causing cell death. SL-YS3 was also effective in reducing the biofilms formed by T. mentagrophytes, which was observed spectrophotometrically with crystal-violet staining and further validated with SEM and CLSM studies of treated biofilms. In vivo studies in a mouse model of cutaneous dermatophytosis involving macroscopic observations, percent culture recovery from skin samples, and histopathological studies showed that SL-YS3 could effectively cure the infected mice after 21 days of topical treatment. Terbinafine (TRB) was used as a standard drug in the experiments. We demonstrate, for the first time, the antidermatophytic activity of a sophorolipid biosurfactant. The findings are suggestive that SL-YS3 can be formulated as a novel antifungal compound to treat cutaneous mycoses caused by T. mentagrophytes.

Antifungal Drugs for Invasive Candida Infections (ICI) in Neonates: Future Perspectives

Fungal infections may complicate the neonatal clinical course, and the spectrum of therapies for their treatment in the perinatal period is limited. Polyenes, Azoles and Echinocandins represent the three classes of antifungal drugs commonly used in the neonatal period. The present review provides an overview about the most recent therapeutic strategies for the treatment of fungal infections in neonates.

Discovery of diazahexa/hepta cyclic cage-like compounds with broad-spectrum antifungal activity against Candida and Cryptococcus species

Invasive fungal infections caused by Candida and Cryptococcus species lead to life threating infections in immunocompromised individuals. Furthermore, increasing incidence of fungal strains resistant to FDA-approved antifungal drugs along with the paucity of antifungal drugs warrants novel drugs to treat invasive fungal infections. In this study, we investigated the antifungal activity of a novel series of diazahexa/hepta cyclic cage-like compounds. Results indicate that compounds with unsubstituted and o-methyl substitution on aryl rings exhibit potent broad-spectrum antifungal activity against various fungal strains. In addition, these compounds showed significant inhibitory activity against Candida hyphae and biofilm formation. Collectively, results from this study indicate that these compounds are promising candidates to develop as novel antifungal drugs to treat drug-resistant fungal infections.

The synthesized cage-like compounds has been investigated for their antifungal activity against Candida and Cryptococcus species.

Echinocandins: Their role in the management of Candida biofilms

The importance of antifungal agents and their clinical implications has received little attention in comparison to antibiotics, particularly in the health-care setting. However, apart from bacterial infections rising in hospitals, the incidences of fungal infections are growing with the development of resistance to conventional antifungal agents. Newer antifungal agents such as echinocandins (ECs) have been extensively studied over the past decade and are recognised as a superior treatment compared with prior antifungals as a first line of therapy in tertiary institutions. Caspofungin (CAS), micafungin (MICA) and anidulafungin (ANID) are the three most widely used EC antifungal agents. The treatment of biofilm-associated fungal infections affecting patients in tertiary health-care facilities has been identified as a challenge, particularly in Indian Intensive Care Unit (ICU) settings. With the rising number of critically ill patients requiring invasive devices such as central venous catheters for treatment, especially in ICUs, these devices serve as a potential source of nosocomial infections. Candida spp. colonisation is a major precursor of these infections and further complicates and prolongs treatment procedures, adding to increasing costs both for hospitals and the patient. Analysing studies involving the use of these agents can help in making critical decisions for antifungal therapy in the event of a fungal infection in the ICU. In addition, the development of resistance to antifungal agents is a crucial factor for assessing the appropriate antifungals that can be used for treatment. This review provides an overview of ANID in biofilms, along with CAS and MICA, in terms of clinical efficacy, resistance development and potency, primarily against Candida spp.

In Vivo Evaluation of Galla chinensis Solution in the Topical Treatment of Dermatophytosis

AIM

Dermatophytosis is one of the main fungal diseases in humans and animals all over the world. Galla chinensis, a traditional medicine, has various pharmacological effects. The goal of this study was to evaluate the treatment effect of Galla chinensis solution (GCS) on dermatophytosis-infected dogs (Microsporum canis, Microsporum gypseum, and Trichophyton mentagrophytes, resp.).

METHODS

The treatment effects of GCS were evaluated by mycological cure rates and clinical score comprised of three indices, including inflammation, hair loss, and lesion scale.

RESULTS

The results showed that, in the three models of dermatophytosis, GCS significantly (P < 0.05) improved skin lesions and fungal eradication. GCS (10% and 5%) had higher efficacy compared to the positive control (Tujingpi Tincture). The fungal eradication efficacy exceeds 85% after treatment with GCS (10%, 5%, and 2.5%) on day 14.

CONCLUSION

The GCS has antidermatophytosis effect in dogs, which may be a candidate drug for the treatment of dermatophytosis.

In vitro and in vivo antidermatophytic activities of some Iranian medicinal plants

In the last decades, the number of people suffering from dermatophytoses has seriously increased, which may be due to the development of resistant strains to a range of antifungal drugs. The present study was aimed to evaluate the antidermatophytic properties of eight extracts from the selected spices and herbs, which were ethno-medicinally used in Iran against Trichophyton mentagrophytes, Trichophyton interdigitale, Microsporum canis, and Microsporum gypseum (10 strain of each). The in vitro antifungal activities of the extracts from four spices and four plants were evaluated by the broth macro dilution method against four dermatophyte strains. In addition, the in vivo therapeutic effects of Myrtus communis L. and Cinnamomum zeylanicum Blume extracts (the most active extracts) on dermatophytosis induced by M. canis and T. mentagrophytes in guinea pigs were evaluated. Results of in vitro antifungal assay revealed that all the tested extracts demonstrated both fungistatic and fungicidal activities with the geometric mean (GM) MIC ranging from 0.058 to 3.73 mg/ml and GM (MFC) ranging from 0.058 to 7.46 mg/ml, respectively. Two extracts (M. communis and C. zeylanicum) significantly inhibited the growth of all the tested dermatophytes, while other extracts demonstrated weak (MICs of >0.625 mg/ml) to moderate (MICs ranging from 100 to 0.625 mg/ml) activities. In vivo antidermatophytic assay demonstrated that clotrimazole cured T. mentagrophytes and M. canis infection on days 21 and 17, respectively, whereas M. communis and C. zeylanicum extracts significantly (p < 0.05) cured T. mentagrophytes and M. canis infection on days 9 and 13 as well as 9, 11, respectively. Phytochemical screening showed the presence of flavonoids, tannins, phenols, and alkaloids in M. communis and alkaloids, flavonoids, and tannins in C. zeylanicum. Findings of the present study also provided the scientific evidence that natural plants could be used in traditional medicine for the prevention and treatment of dermatophytic infections.

Evaluation of the antifungal activities of various extracts from Pistacia atlantica Desf

Background and Purpose:

Despite the availability of various treatments for fungal diseases, there are some limitations in the management of these conditions due to multiple treatment-related side-effects. The present study was designed to investigate the antifungal properties of different extracts from Pistacia atlantica Desf.

Materials and Methods:

Different parts of P. atlantica (i.e., dried fruit, fresh fruit and dried leaf) were separately extracted via percolation method with 80% methanol and water. Gas chromatography/mass spectrometry (GC/MS) analysis was performed to determine the main constituents of leaf and fruit extracts from P. atlantica. In vitro anti-Candida activities of the extracts against Candida albicans, Candida glabrata and Saccharomyces cerevisiae were studied. For this purpose, the minimum inhibitory concentrations (MICs) and minimum fungicidal concentrations (MFCs) were determined, using broth microdilution method, according to the modified M27-A3 protocol on yeasts, proposed by the Clinical and Laboratory Standards Institute (CLSI).

Results:

Based on GC/MS analysis, the main constituents of P. atlantica fruit extracts were β-myrcene (41.4%), α-pinene (32.48%) and limonene (4.66%), respectively, whereas the major constituents of P. atlantica leaf extracts were trans-caryophyllene (15.18%), α-amorphene (8.1%) and neo-allo-ocimene (6.21%), respectively. As the findings indicated, all the constituents exhibited both fungistatic and fungicidal activities, with MICs ranging from 6.66 to 26.66 mg/mL and MFCs ranging from 13.3 to 37.3 mg/mL, respectively. Among the evaluated extracts, the methanolic fresh fruit extract of P. atlantica was significantly more effective than other extracts (P<0.05).

Conclusion:

Based on the findings of the present study, novel antifungal agents need to be developed, and use of P. atlantica should be promoted in the traditional treatment of Candida infections.

Evaluation of antifungal activities of the essential oil and various extracts of Nigella sativa and its main component, thymoquinone against pathogenic dermatophyte strains

OBJECTIVE

Plant extracts and plant-derived compounds are valuable sources as folk medicine for the treatment and prevention of a wide range of diseases including infectious diseases. In the present study, the antifungal activities of the essential oil and various extracts Nigella sativa and its active principle, thymoquinone against Trichophyton mentagrophytes, Microsporum canis and Microsporum gypseum as pathogenic dermatophyte strains have been evaluated. In addition, the cytotoxic effects of N. sativa against murine macrophage cells were determined.

MATERIALS AND METHODS

In this study, the antifungal activity was studied by disk diffusion method and assessment of minimum inhibitory concentration (MIC) of extracts using broth macrodilution method. In addition, the cytotoxic activity of N. sativa was evaluated by colorimetric assay (MTT). The components of the N. sativa essential oil were also identified by gas chromatography/mass spectroscopy (GC/MS) analysis.

RESULTS

The results showed that the essential oil and various extracts of N. sativa particularly thymoquinone have potent antifungal effects on T. mentagrophytes, M. canis and M. gypseum as pathogenic dermatophyte strains. In the assessment of the cytotoxicity activity, it could be observed that N. sativa had no significant cytotoxicity in the murine macrophages at low concentrations. While, thymoquinone in comparison with essential oil and various extracts of N. sativa showed higher cytotoxicity on murine macrophage cells. In the GC/MS analysis, thymoquinone (42.4%), p-cymene (14.1%), carvacrol (10.3%) and longifolene (6.1%) were found to be the major components of N. sativa essential oil.

CONCLUSION

The findings of this study suggest a first step in the search of new antidermatophytic drugs and aid the use of N. sativa seeds in the traditional medicine for dermatophytic infections.

In pursuit of the ideal antifungal agent for Candida infections: high-throughput screening of small molecules

Candida infections have created a great burden on the public healthcare sector. The situation is worsened by recent epidemiological changes. Furthermore, the current arsenal of antifungal agents is limited and associated with undesirable drawbacks. Therefore, new antifungal agents that surpass the existing ones are urgently needed. High-throughput screening of small molecule libraries enables rapid hit identification and, possibly, increases hit rate. Moreover, the identified hits could be associated with unrecognized or multiple drug targets, which would provide novel insights into the biological processes of the pathogen. Hence, it is proposed that high-throughput screening of small molecules is particularly important in the pursuit of the ideal antifungal agents for Candida infections.

Antifungal, Antileishmanial, and Cytotoxicity Activities of Various Extracts of Berberis vulgaris (Berberidaceae) and Its Active Principle Berberine

In this study, in vitro antidermatophytic activity against Trichophyton mentagrophytes, Trichophyton rubrum, Microsporum canis, and Microsporum gypseum was studied by disk diffusion test and assessment of minimum inhibitory concentration (MIC) using CLSI broth macrodilution method (M38-A2). Moreover, antileishmanial and cytotoxicity activity of B. vulgaris and berberine against promastigotes of Leishmania major and Leishmania tropica were evaluated by colorimetric MTT assay. The findings indicated that the various extracts of B. vulgaris particularly berberine showed high potential antidermatophytic against pathogenic dermatophytes tested with MIC values varying from 0.125 to >4 mg/mL. The results revealed that B. vulgaris extracts as well as berberine were effective in inhibiting L. major and L. tropica promastigotes growth in a dose-dependent manner with IC50 (50% inhibitory concentration) values varying from 2.1 to 26.6  μ g/mL. Moreover, it could be observed that berberine as compared with B. vulgaris exhibited more cytotoxicity against murine macrophages with CC50 (cytotoxicity concentration for 50% of cells) values varying from 27.3 to 362.6  μ g/mL. Results of this investigation were the first step in the search for new antidermatophytic and antileishmanial drugs. However, further works are required to evaluate exact effect of these extracts in animal models as well as volunteer human subjects.

In vitro antifungal activity of extracts and neolignans from Piper regnellii against dermatophytes

The present study was designated to evaluate the in vitro antidermatophyte activity of extracts from leaves of Piper regnellii as well as of the bioactivity-directed isolation of neolignans. The antifungal assay was performed by microdilution techniques. The hydroalcoholic extract of Piper regnellii leaves presented a strong activity against the dermatophyte fungi Trichophyton mentagrophytes, Trichophyton rubrum, Microsporum canis and Microsporum gypseum with MICs of 15.62, 15.62, 15.62 and 62.5 microg/ml, respectively. On light microscopy and scanning electron microscopy of nail fragments not exposed to hydroalcoholic extract of Piper regnelli leaves, well-formed and extensive mycelial growth was seen. On nail fragments exposed to hydroalcoholic extract at concentrations more than 1.2mg/ml and then inoculated with spore suspension, growth was not seen. The hydroalcoholic extract was fractionated on silica gel in to nine fractions. The active chloroform fraction was lyophilized and chromatographed by column chromatography on silica gel. Structures were established by comparison with literature data and identified as eupomatenoid-3 and eupomatenoid-5. The pure compounds showed strong activity on Trichophyton rubrum with MIC of 50 and 6.2 microg/ml, respectively. Comparing the activity of the active chloroform fraction obtained from hydroalcoholic crude extract with that of isolated compound eupomatenoid-5, it is clear that this showed the same results against Trichophyton rubrum. The results showed that the plant could be explored for possible antifungal agents and provides preliminary scientific validation for the traditional medicinal use of this plant.

Antidermatophyte activity of ether extract of Nigella sativa and its active principle, thymoquinone

The antifungal activity of ether extract of Nigella sativa seed and its active principle thymoquinone was tested against eight species of dermatophytes: four species of Trichophyton rubrum and one each of Trichophyton interdigitale, Trichophyton mentagrophytes, Epidermophyton floccosum and Microsporum canis. Agar diffusion method with serial dilutions of ether extract of Nigella sativa, thymoquinone and griseofulvin was employed. The incubation was carried out at 30 degrees C for 14 days. The diameter of fungal colonies and the percentage inhibition of the fungal growth at each dilution were determined, taking those of the controls as 100%. The minimum inhibitory concentration (MIC) was considered as the minimum concentration of the drug, which inhibited 80-100% of the fungal growth. The MICs of the ether extract of Nigella sativa and thymoquinone were between 10 and 40 and 0.125 and 0.25 mg/ml, respectively, while those of griseofulvin ranged from 0.00095 to 0.0155 mg/ml. These results denote the potentiality of Nigella sativa as a source for antidermatophyte drugs and support its use in folk medicine for the treatment of fungal skin infections.

Uptake of Aspergillus fumigatus Conidia by phagocytic and nonphagocytic cells in vitro: quantitation using strains expressing green fluorescent protein

Several pathogenic fungal organisms enter eukaryotic cells and manipulate the host cell environment to favor their own growth and survival. Aspergillus fumigatus is a saprophytic fungus that causes invasive lung disease in the immunocompromised host. To determine whether A. fumigatus could enter eukaryotic cells, we studied the uptake of two different GFP-expressing A. fumigatus strains into A549 lung epithelial cells, human umbilical vein endothelial (HUVE) cells, and J774 murine macrophages in vitro. A549 cells internalized 30% of the bound conidia whereas HUVE and J774 cells internalized 50 and 90%, respectively. Conidia within A549 cells remained viable for 6 h; however, 60 to 80% of conidia within J774 cells were killed after only 4 h. Live and heat-killed conidia were internalized to the same extent by A549 cells. After 6 h, almost none of the conidia inside A549 cells had germinated, whereas extracellular conidia had developed germ tubes. Internalization of conidia by A549 cells was a temperature-dependent process and required rearrangement of the underlying host cell cytoskeleton; uptake was inhibited by 75% with 0.5 microM cytochalasin D and by 65% with 5 microM colchicine. Fluorescent labeling of infected A549 cells with rhodamine phalloidin provided visible evidence of cytoskeletal alteration as many of the intracellular conidia were contained in actin-coated phagosomes. These data provide evidence that significant numbers of A. fumigatus conidia can be internalized by nonprofessional phagocytes in vitro and these cells may serve as reservoirs for immune cell evasion and dissemination throughout the host.