A screening of the MMV Pathogen Box® reveals new potential antifungal drugs against the etiologic agents of chromoblastomycosis

Multidrug-resistant keratinolytic dermatophytes and non-dermatophytes causing onychomycosis in outpatients

AIMS

This study identified and determined antibiograms of keratinolytic dermatophytes (DM), non-dermatophytic molds (NDM), and yeasts causing onychomycosis.

METHODS

Morphological, cultural, and biochemical characteristics were used to identify DM and NDM. The keratinolytic activity (KA) and antibiograms were conducted with keratin azure and the agar diffusion method, respectively. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) were determined using the microdilution method.

RESULTS

Onychomycosis was more prevalent in males (53%) than females, toenails (57%) than fingernails, and commercial employees (40%) than other employees or unemployed. Fungal growth was observed in 92.5% nail samples. DM, NDM, and yeasts caused 46%, 35%, and 19% onychomycosis, respectively. Trichophyton rubrum and Trichophyton mentagrophytes were the common DM. Five different genus of NDM and three different yeasts were isolated. The KA of DM was 30-45% higher than that of NDM and yeasts. All fungal isolates (FI) were resistant to griseofulvin and fluconazole. However, 71%, 64%, and 36% of FI were sensitive to terbinafine hydrochloride, nystatin, and ketoconazole, respectively, while 84% of DM and 46% of NDM were multidrug-resistant. The MIC and MFC of these antifungals against FI ranged from micrograms to milligrams.

CONCLUSION

Multidrug resistance is growing in keratinolytic DM and NDM.

Auranofin is active against Histoplasma capsulatum and reduces the expression of virulence-related genes

BACKGROUND

Auranofin is an approved anti-rheumatic drug that has a broad-range inhibitory action against several microorganisms, including human pathogenic fungi. The auranofin activity against Histoplasma capsulatum, the dimorphic fungus that causes histoplasmosis, has not been properly addressed. Since there are few therapeutic options for this life-threatening systemic mycosis, this study evaluated the effects of auranofin on H. capsulatum growth and expression of virulence factors.

METHODOLOGY/PRINCIPAL FINDINGS

Minimal inhibitory and fungicidal concentrations (MIC and MFC, respectively) of auranofin against 15 H. capsulatum strains with distinct genetic backgrounds were determined using the yeast form of the fungus and a microdilution protocol. Auranofin activity was also assessed on a macrophage model of infection and on a Tenebrio molitor invertebrate animal model. Expression of virulence-related genes was compared between auranofin treated and untreated H. capsulatum yeast cells using a quantitative PCR assay. Auranofin affected the growth of different strains of H. capsulatum, with MIC and MFC values ranging from 1.25 to 5.0 μM and from 2.5 to >10 μM, respectively. Auranofin was able to kill intracellular H. capsulatum yeast cells and conferred protection against the fungus in the experimental animal model of infection. Moreover, the expression of catalase A, HSP70, superoxide dismutase, thioredoxin reductase, serine proteinase, cytochrome C peroxidase, histone 2B, formamidase, metallopeptidase, Y20 and YPS3 proteins were reduced after six hours of auranofin treatment. CONCLUSIONS/SIGNIFICANCE: Auranofin is fungicidal against H. capsulatum and reduces the expression of several virulence-related genes, which makes this anti-rheumatic drug a good candidate for new medicines against histoplasmosis.

In vitro antifungal activity of MMV Pathogen Box® compounds alone or in combination with antifungal drugs against mucormycosis agents

Mucormycosis is a severe fungal infection that demands immediate and decisive intervention upon suspicion. The causative agents of mucormycosis exhibit inherent resistance to echinocandins and voriconazole, and their in vitro susceptibility to terbinafine is highly variable and species-specific. Considering these factors and the limitations of currently available antifungal therapies, the identification of novel antifungals with potent activity against mucormycosis is of paramount importance. This study aims to identify compounds from the MMV Pathogen Box® presenting antifungal activity against selected mucormycosis agents and to evaluate their potential synergistic effects when combined with antifungal drugs. A screening of the Pathogen Box® compounds was conducted, isolated or in combination with sub-inhibitory concentrations of amphotericin B, isavuconazole or posaconazole, against a Rhizopus oryzae strain. Hits from the screenings were further evaluated against eight Mucoralean strains for minimal inhibitory and fungicidal concentration determinations and to confirm synergistic interactions using the checkerboard method. Ultrastructural studies were performed using scanning electron microscopy. MMV675968 exhibited fungicidal activity against a R. oryzae strain. All but one Rhizopus spp. strains presented MIC ≤ 1 μg/mL, with a geometric mean of 0.78 μg/mL observed across all isolates for this compound, which did not change significantly the cellular structure of this fungus. The combination screening with antifungal drugs revealed six additional compounds potentially active against the R. oryzae strain, two of them demonstrated proven synergism through the checkerboard assay. This first study with the MMV Pathogen Box® and Zigomycetes highlights promising new treatment options for mucormycosis in the future.

Repurposing drugs for fungal infections: advantages and limitations

Tweetable abstract Repurposing existing drugs for fungal infections has demonstrated potential in both in vitro and animal models, but there are still obstacles to overcome for clinical application. #antifungal #drugrepurposing #fungalinfections.

Leveraging the MMV Pathogen Box to Engineer an Antifungal Compound with Improved Efficacy and Selectivity against Candida auris

Fungal infections pose a significant and increasing threat to human health, but the current arsenal of antifungal drugs is inadequate. We screened the Medicines for Malaria Venture (MMV) Pathogen Box for new antifungal agents against three of the most critical Candida species (Candida albicans, Candida auris, and Candida glabrata). Of the 14 identified hit compounds, most were active against C. albicans and C. auris. We selected the pyrazolo-pyrimidine MMV022478 for chemical modifications to build structure-activity relationships and study their antifungal properties. Two analogues, 7a and 8g, with distinct fluorine substitutions, greatly improved the efficacy against C. auris and inhibited fungal replication inside immune cells. Additionally, analogue 7a had improved selectivity toward fungal killing compared to mammalian cytotoxicity. Evolution experiments generating MMV022478-resistant isolates revealed a change in morphology from oblong to round cells. Most notably, the resistant isolates blocked the uptake of the fluorescent dye rhodamine 6G and showed reduced susceptibility toward fluconazole, indicative of structural changes in the yeast cell surface. In summary, our study identified a promising antifungal compound with activity against high-priority fungal pathogens. Additionally, we demonstrated how structure-activity relationship studies of known and publicly available compounds can expand the repertoire of molecules with antifungal efficacy and reduced cytotoxicity to drive the development of novel therapeutics.

Screening of MMV pandemic response and pathogen box compounds against pan-drug-resistant Klebsiella pneumoniae to identify potent inhibitory compounds

Background

The recent emergence of pan-drug-resistant (PDR) K. pneumoniae strains hinders the success rate of treatment procedures for patients. High mortality, extended duration of hospitalization with high costs is associated with such infections. Discovery and identification of new drugs are inevitable to combat PDR clinical pathogens. We aim to identify and evaluate new compounds in vitro against a PDR clinical K. pneumoniae isolate using compounds of Pathogen Box and Pandemic Response Box from Medicines for Malaria Venture (MMV).

Methods

The PDR strain was initially screened with the 601 compounds from both Boxes at 10 ​μM concentration. Formation of dormant cells against the drug activity was assessed using persister assay. MIC was determined for the drugs inhibiting PDR K. pneumoniae during initial screening.

Results

Five compounds were identified to inhibit the test strain. MMV1580854 (94.60 ​%), MMV1579788 (94.65 ​%), MMV1578574 (eravacycline; 93.13 ​%), MMV1578566 (epetraborole; 95.29 ​%) and MMV1578564 (96.32 ​%) were able to exhibit a higher percentage of growth inhibition. Persisters were found to be growing in a range from 104 to 107 ​CFU/ml. Minimum inhibitory concentrations (MIC) of all compounds were ≥ 2 ​μM except for MMV1579788, which had a MIC of ≥ 5 ​μM.

Conclusion

Five novel compounds were identified against the highly evolved pan-drug-resistant K. pneumoniae. Among the five, epetraborole andMMV1578564 were identified as highly potent based on the persister frequency and MICs. The pan-drug resistant clinical isolate used in this study was found to be acting differently from the reference or wild type strains against the test compounds in a previous study.

Diagnostic capacities and treatment practices on implantation mycoses: Results from the 2022 WHO global online survey

Between January and March 2022, WHO conducted a global online survey to collect data on diagnostic capacities and treatment practices in different settings for four implantation mycoses: eumycetoma, actinomycetoma, cutaneous sporotrichosis and chromoblastomycosis. The survey investigated the type of diagnostic methods available in countries at various health system levels (tertiary, secondary, primary level) and the medicines used to treat implantation mycoses, with a view to understanding the level of drug repurposing for treatment of these diseases. 142 respondents from 47 countries, including all continents, contributed data: 60% were from middle-income countries, with 59% working at the tertiary level of the health system and 30% at the secondary level. The results presented in this article provide information on the current diagnostic capacity and treatment trends for both pharmacological and non-pharmacological interventions. In addition, the survey provides insight on refractory case rates, as well as other challenges, such as availability and affordability of medicines, especially in middle-income countries. Although the study has limitations, the survey-collected data confirms that drug repurposing is occurring for all four surveyed implantation mycoses. The implementation of an openly accessible global and/or a national treatment registry for implantation mycoses could contribute to address the gaps in epidemiological information and collect valuable observational data to inform treatment guidelines and clinical research.

Antifungal Development and the Urgency of Minimizing the Impact of Fungal Diseases on Public Health

Fungal infections are a major public health problem resulting from the lack of public policies addressing these diseases, toxic and/or expensive therapeutic tools, scarce diagnostic tests, and unavailable vaccines. In this Perspective, we discuss the need for novel antifungal alternatives, highlighting new initiatives based on drug repurposing and the development of novel antifungals.

Pandemic Response Box® library as a source of antifungal drugs against Scedosporium and Lomentospora species

Scedosporium and Lomentospora species are opportunistic filamentous fungi that cause localized and disseminated infections in immunocompetent and immunocompromised patients. These species are considered resistant fungi due to their low susceptibility to most current antifungal agents used in healthcare settings. The search for new compounds that could work as promising candidate antifungal drugs is an increasing field of interest. In this context, in the present study we screened the Pandemic Response Box® library (Medicines for Malaria Venture [MMV], Switzerland) to identify compounds with antifungal activity against Scedosporium and Lomentospora species. An initial screening of the drugs from this collection at 5 μM was performed using a clinical Scedosporium aurantiacum isolate according to the EUCAST protocol. Compounds with activity against this fungus were also tested against four other species (S. boydii¸ S. dehoogii, S. apiospermum and L. prolificans) at concentrations ranging from 0.078 to 10 μM. Seven compounds inhibited more than 80% of S. aurantiacum growth, three of them (alexidine, amorolfine and olorofim) were selected due to their differences in mechanism of action, especially when compared to drugs from the azole class. These compounds were more active against biofilm formation than against preformed biofilm in Scedosporium and Lomentospora species, except alexidine, which was able to decrease preformed biofilm about 50%. Analysis of the potential synergism of these compounds with voriconazole and caspofungin was performed by the checkerboard method for S. aurantiacum. The analysis by Bliss methodology revealed synergistic effects among selected drugs with caspofungin. When these drugs were combined with voriconazole, only alexidine and amorolfine showed a synergistic effect, whereas olorofim showed an antagonistic effect. Scanning electron microscopy revealed that alexidine induces morphology alterations in S. aurantiacum biofilm grown on a catheter surface. Reactive oxygen species production, mitochondrial activity and surface components were analyzed by fluorescent probes when S. aurantiacum was treated with selected drugs and revealed that some cell parameters are altered by these compounds. In conclusion, alexidine, amorolfine and olorofim were identified as promising compounds to be studied against scedosporiosis and lomentosporiosis.

New possibilities for chromoblastomycosis and phaeohyphomycosis treatment: identification of two compounds from the MMV Pathogen Box® that present synergism with itraconazole

BACKGROUND

Black fungi of the Herpotrichiellaceae family are agents of chromoblastomycosis and phaeohyphomycosis. There are few therapeutic options for these infections and it is common to associate antifungal drugs in their treatment.

OBJECTIVES

To investigate the Medicines for Malaria Venture (MMV) Pathogen Box^® for possible compounds presenting synergism with antifungal drugs used to treat black fungal infections.

METHODS

An initial screening of the Pathogen Box^® compounds was performed in combination with itraconazole or terbinafine at sub-inhibitory concentrations against Fonsecaea pedrosoi. Hits were further tested against eight Herpotrichiellaceae using the checkerboard method.

FINDINGS

No synergism was observed with terbinafine. MMV687273 (SQ109) and MMV688415 showed synergism with itraconazole against F. pedrosoi. Synergism of these compounds was confirmed with some black fungi by the checkerboard method. SQ109 and itraconazole presented synergism for Exophiala dermatitidis, F. pedrosoi, F. monophora and F. nubica, with fungicidal activity for F. pedrosoi and F. monophora. MMV688415 presented synergism with itraconazole only for F. pedrosoi, with fungicidal activity. The synergic compounds had high selectivity index values when combined with itraconazole.

MAIN CONCLUSIONS

These compounds in combination, particularly SQ109, are promising candidates to treat Fonsecaea spp. and E. dermatitidis infections, which account for most cases of chromoblastomycosis and phaeohyphomycosis.

Novel avenues for identification of new antifungal drugs and current challenges

INTRODUCTION

: Some of otherwise useful fungi are pathogenic to humans, and unfortunately, the number of these pathogens is increasing. In addition to common skin infections, these opportunistic pathogens are able to cause severe, often incurable, systemic mycoses.

AREAS COVERED

: The number of antifungal drugs is limited, especially drugs that can be used for systemic administration, and resistance to these drugs is very common. This review summarizes various approaches to the discovery and development of new antifungal drugs, provides an overview of the most important molecules in terms of basic (laboratory) research and compounds currently in clinical trials, and focuses on drug repurposing strategy, while providing an overview of drugs of other indications that have been tested in vitro for their antifungal activity for possible expansion of antifungal drugs and/or support of existing antimycotics.

EXPERT OPINION

: Despite the limitations of the research of new antifungal drugs by pharmaceutical manufacturers, in addition to innovated molecules based on clinically used drugs, several completely new small entities with unique mechanisms of actions have been identified. The identification of new molecular targets that offer alternatives for the development of new unique selective antifungal highly effective agents has been an important outcome of repurposing of non-antifungal drugs to antifungal drug. Also, given the advances in monoclonal antibodies and their application to immunosuppressed patients, it may seem possible to predict a more optimistic future for antifungal therapy than has been the case in recent decades.

The Antifungal Itraconazole Is a Potent Inhibitor of Chikungunya Virus Replication

Chikungunya virus (CHIKV) is the causative agent of chikungunya fever, a disabling disease that can cause long-term severe arthritis. Since the last large CHIKV outbreak in 2015, the reemergence of the virus represents a serious public health concern. The morbidity associated with viral infection emphasizes the need for the development of specific anti-CHIKV drugs. Herein, we describe the development and characterization of a CHIKV reporter replicon cell line and its use in replicon-based screenings. We tested 960 compounds from MMV/DNDi Open Box libraries and identified four candidates with interesting antiviral activities, which were confirmed in viral infection assays employing CHIKV-nanoluc and BHK-21 cells. The most noteworthy compound identified was itraconazole (ITZ), an orally available, safe, and cheap antifungal, that showed high selectivity indexes of >312 and >294 in both replicon-based and viral infection assays, respectively. The antiviral activity of this molecule has been described against positive-sense single stranded RNA viruses (+ssRNA) and was related to cholesterol metabolism that could affect the formation of the replication organelles. Although its precise mechanism of action against CHIKV still needs to be elucidated, our results demonstrate that ITZ is a potent inhibitor of the viral replication that could be repurposed as a broad-spectrum antiviral.

Identifying novel drugs with new modes of action for neglected tropical fungal skin diseases (fungal skinNTDs) using an Open Source Drug discovery approach

INTRODUCTION

The three fungal skin neglected tropical diseases (NTD) mycetoma, chromoblastomycosis and sporotrichosis currently lack prioritization and support to establish drug discovery programs in search for novel treatment options. This has made the efforts to identify novel drugs for these skinNTDs fragmented.

AREAS COVERED

To help escalate the discovery of novel drugs to treat these fungal skinNTDs, the authors have prepared an overview of the compounds with activity against fungal skinNTDs by analyzing data from individual drug discovery studies including those performed on the Medicines for Malaria Venture (MMV) open access boxes.

EXPERT OPINION

The authors were unable to identify studies in which causative agents of all three skinNTDs were included, indicating that an integrated approach is currently lacking. From the currently available data, the azoles and iodoquinol were the only compounds with activity against causative agents from the three different fungal skinNTDs. Fungal melanin inhibition enhanced the activity of antifungal agents. For mycetoma, the fenarimols, aminothiazoles and benzimidazole carbamates are currently being investigated in the MycetOS initiative. To come to a more integrated approach to identify drugs active against all three fungal skinNTDs, compounds made in the MycetOS initiative could also be explored for chromoblastomycosis and sporotrichosis.

In vitro activity of Schinus terebinthifolius extract and fractions against Sporothrix brasiliensis

BACKGROUND

Sporothrix brasiliensis is the causative agent of zoonotic cases of sporotrichosis in Brazil and is associated with atypical and severe presentations in cats, dogs, and humans. Sporotrichosis treatment is usually time- and cost-consuming, sometimes with poor response and host toxicity. Schinus terebinthifolius has proven efficacy against bacteria and fungi of clinical interest.

OBJECTIVE

To determine the in vitro activity of S. terebinthifolius against S. brasiliensis.

METHODS

Five S. brasiliensis isolates and three reference strains were subjected to a hydroethanol extract derived from the leaves of S. terebinthifolius and its fractions. The minimal inhibitory concentration (MIC) was determined using the broth microdilution method according to the M38-A2 CLSI guidelines. Also, the fungicidal/fungistatic activity of the extract and fractions was studied.

FINDINGS

The crude extract of S. terebinthifolius inhibited the growth of S. brasiliensis (MIC: 0.5-1.0 µg/mL), while the partitioned extracts dichloromethane, ethyl acetate, and butanol demonstrated growth inhibition at 8 µg/mL due to a fungistatic activity.

MAIN CONCLUSIONS

Due to its in vitro efficacy against S. brasiliensis and its known pharmacological safety, S. terebinthifolius is a candidate to be tested using in vivo models of sporotrichosis.

Medicines for Malaria Venture COVID Box: a source for repurposing drugs with antifungal activity against human pathogenic fungi

BACKGROUND

Treatment of mycoses is often ineffective, usually prolonged, and has some side effects. These facts highlight the importance of discovering new molecules to treat fungal infections.

OBJECTIVES

To search the Medicines for Malaria Venture COVID Box for drugs with antifungal activity.

METHODS

Fourteen human pathogenic fungi were tested against the 160 drugs of this collection at 1.0 µM concentration. We evaluated the ability of the drugs to impair fungal growth, their fungicidal nature, and morphological changes caused to cells.

FINDINGS

Thirty-four molecules (21.25%) presented antifungal activity. Seven are antifungal drugs and one is the agricultural fungicide cycloheximide. The other drugs with antifungal activity included antibiotics (n = 3), antimalarials (n = 4), antivirals (n = 2), antiparasitcs (n = 3), antitumor agents (n = 5), nervous system agents (n = 3), immunosuppressants (n = 3), antivomiting (n = 1), antiasthmatic (n = 1), and a genetic disorder agent (n = 1). Several of these drugs inhibited Histoplasma capsulatum and Paracoccidioides brasiliensis growth (15 and 20, respectively), while Fusarium solani was not affected by the drugs tested. Most drugs were fungistatic, but niclosamide presented fungicidal activity against the three dimorphic fungi tested. Cyclosporine affected morphology of Cryptococcus neoformans.

MAIN CONCLUSIONS

These drugs represent new alternatives to the development of more accessible and effective therapies to treat human fungal infections.

Gut Microbial Alterations in Diarrheal Baer's Pochards (Aythya baeri)

The structure and composition of gut microbiota correlate with the occurrence and development of host health and disease. Diarrhea can cause alterations in gut microbiota in animals, and the changes in the gut microbial structure and composition may affect the development of diarrhea. However, there is a scarcity of information on the effects of diarrhea on gut fungal composition and structure, particularly in Baer's pochard (Aythya baeri). The current study was performed for high-throughput sequencing of the fungal-specific internal transcribed spacer 1 (ITS-1) to detect the differences of gut mycobiota in healthy and diarrheal Baer's pochard. Results showed that the gut mycobiota not only decreased significantly in diversity but also in structure and composition. Statistical analysis between two groups revealed a significant decrease in the abundance of phylum Rozellomycota, Zoopagomycota, Mortierellomycota, and Kickxellomycota in diarrheal Baer's pochard. At the genus levels, fungal relative abundance changed significantly in 95 genera, with 56 fungal genera, such as Wickerhamomyces, Alternaria, Penicillium, Cystofilobasidium, and Filobasidium, increasing significantly in the gut of the diarrheal Baer's pochard. In conclusion, the current study revealed the discrepancy in the gut fungal diversity and community composition between the healthy and diarrheal Baer's pochard, laying the basis for elucidating the relationship between diarrhea and the gut mycobiota in Baer's pochard.

Identification of Promising Antifungal Drugs against Scedosporium and Lomentospora Species after Screening of Pathogen Box Library

Fungal infections have been increasing during the last decades. Scedosporium and Lomentospora species are filamentous fungi most associated to those infections, especially in immunocompromised patients. Considering the limited options of treatment and the emergence of resistant isolates, an increasing concern motivates the development of new therapeutic alternatives. In this context, the present study screened the Pathogen Box library to identify compounds with antifungal activity against Scedosporium and Lomentospora. Using antifungal susceptibility tests, biofilm analysis, scanning electron microscopy (SEM), and synergism assay, auranofin and iodoquinol were found to present promising repurposing applications. Both compounds were active against different Scedosporium and Lomentospora, including planktonic cells and biofilm. SEM revealed morphological alterations and synergism analysis showed that both drugs present positive interactions with voriconazole, fluconazole, and caspofungin. These data suggest that auranofin and iodoquinol are promising compounds to be studied as repurposing approaches against scedosporiosis and lomentosporiosis.

Antifungal Drug Repurposing

Control of fungal pathogens is increasingly problematic due to the limited number of effective drugs available for antifungal therapy. Conventional antifungal drugs could also trigger human cytotoxicity associated with the kidneys and liver, including the generation of reactive oxygen species. Moreover, increased incidences of fungal resistance to the classes of azoles, such as fluconazole, itraconazole, voriconazole, or posaconazole, or echinocandins, including caspofungin, anidulafungin, or micafungin, have been documented. Of note, certain azole fungicides such as propiconazole or tebuconazole that are applied to agricultural fields have the same mechanism of antifungal action as clinical azole drugs. Such long-term application of azole fungicides to crop fields provides environmental selection pressure for the emergence of pan-azole-resistant fungal strains such as Aspergillus fumigatus having TR34/L98H mutations, specifically, a 34 bp insertion into the cytochrome P450 51A (CYP51A) gene promoter region and a leucine-to-histidine substitution at codon 98 of CYP51A. Altogether, the emerging resistance of pathogens to currently available antifungal drugs and insufficiency in the discovery of new therapeutics engender the urgent need for the development of new antifungals and/or alternative therapies for effective control of fungal pathogens. We discuss the current needs for the discovery of new clinical antifungal drugs and the recent drug repurposing endeavors as alternative methods for fungal pathogen control.

Identification of two potential inhibitors of Sporothrix brasiliensis and Sporothrix schenckii in the Pathogen Box collection

Sporotrichosis is a neglected endemic mycosis with a high incidence in Latin America, mainly in Brazil. Sporothrix schenckii is the most frequent species in Latin America, whereas Sporothrix brasiliensis is the predominant species observed in Brazil and is associated with both human and animal sporotrichosis. Sporotrichosis treatment remains restricted to a few options, itraconazole being the first choice for human and animal therapy. In this work, we screened the molecular library Pathogen Box (Medicines for Malaria Venture [MMV], Switzerland) in search of compounds with anti-Sporothrix activity. Our initial screen of the 400 compounds identified five compounds that inhibited more than 80% of S. brasiliensis and S. schenkii growth. Among those, three compounds (MMV675968, MMV102872, and MMV002817 (known as iodoquinol)) not previously described as antifungals or agrochemicals, were selected for further evaluation. MMV102872 and iodoquinol showed the most promising combination of antifungal activity (lower inhibitory concentration) and fungal selectivity (lower cytotoxicity in LLC-MK2 cells). Scanning electron microscopy and flow cytometry analyses revealed that MMV102872 and iodoquinol induced changes in cell morphology, membrane integrity, and the presence of neutral lipids, impairing fungal survival. Our results indicate that MMV102872 and iodoquinol are promising molecules for use as scaffolds for the development of new antifungal agents.

Cinnamyl Schiff bases: synthesis, cytotoxic effects and antifungal activity of clinical interest

The aim of this study was to synthesize and investigate the in vitro antifungal properties of 23 cinnamyl Schiff bases. In addition, cytotoxic effects of such cinnamyl Schiff bases against human lung, kidney or red blood cells were also checked. The compounds were synthesized in a single-step, 2 min of reaction under microwave irradiation produced up to 97% yield. Six of the 23 cinnamyl Schiff bases possessed antifungal activities against strains of Candida, Aspergillus, Fonsecaea and, particularly, Cryptococcus species. Indeed, cinnamyl Schiff bases 1 and 23 exhibited minimum inhibitory concentration (MIC) values more than twofold lower than fluconazole (FCZ) against all the Cryptococcus neoformans strains (MIC = 1·33, 1·4 and 5·2 µg ml^-1 , respectively) and Cryptococcus gattii strains (MIC = 5·3, 2·8 and 9·2 µg ml^-1 , respectively) (12 strains of each species) while cinnamyl Schiff base 11 was as potent as FCZ against all strains from both Cryptococcus species. No significant cytotoxic effects were observed for Schiff bases against human lung, kidney or red blood cells, all presenting selective indexes higher than 10. In conclusion, this study revealed cinnamyl Schiff bases, especially 1 and 23, as new lead anticryptococcal agents for the discovery of novel antifungal drugs. SIGNIFICANCE AND IMPACT OF THE STUDY: The occurrence and severity of fungal infections have increased in recent decades due to resistance to available antifungal drugs and the appearance of new emerging pathogens. Thus, the search for new antifungal agents is mandatory. From a series of 23 cinnamyl Schiff bases, two compounds (1 and 23) were interrogated as new anticryptococcal agents without significant cytotoxicity against human lung, kidney or red blood cells. In turns, these new Schiff bases are lead compounds for the discovery of novel antifungal drugs.