Repurposing antipsychotic drugs into antifungal agents: Synergistic combinations of azoles and bromperidol derivatives in the treatment of various fungal infections

Tackling multi-drug resistant fungi by efflux pump inhibitors

The emergence of multidrug-resistant fungi is of grave concern, and its infections are responsible for significant deaths among immunocompromised patients. The treatment of fungal infections primarily relies on a clinical class of antibiotics, including azoles, polyenes, echinocandins, polyketides, and a nucleotide analogue. However, the incidence of fungal infections is increasing as the treatment for human and plant fungal infections overlaps with antifungal drugs. The need for new antifungal agents acting on different targets than known targets is undeniable. Also, the pace at which loss of fungal susceptibility to antibiotics cannot be undermined. There are several modes by which fungi can develop resistance to antibiotics, including reduced drug uptake, drug target alteration, and a reduction in the cellular concentration of the drug due to active extrusions and biofilm formation. The efflux pump's overexpression in the fungi primarily reduced the antibiotic's concentration to a sub-lethal concentration, thus responsible for developing resistant fungus strains. Several strategies are used to check antibiotic resistance in multi-drug resistant fungi, including synthesizing antibiotic analogs and giving antibiotics in combination therapies. Among them, the efflux pump protein inhibitors are considered potential adjuvants to antibiotics and can block the efflux of antibiotics by inhibiting efflux pump protein transporters. Moreover, it can sensitize the antifungal drugs to multi-drug resistant fungi with overexpressed efflux pump proteins. This review discusses the natural lead molecules, repurposable drugs, and formulation strategies to overcome the efflux pump activity in the fungi.

Drug repurposing for fungal infections

The rise of multidrug-resistant bacteria is a well-recognized threat to world health, necessitating the implementation of effective treatments. This issue has been identified as a top priority on the global agenda by the World Health Organization. Certain strains, such as Candida glabrata, Candida krusei, Candida lusitaniae, Candida auris, select cryptococcal species, and opportunistic Aspergillus or Fusarium species, have significant intrinsic resistance to numerous antifungal medicines. This inherent resistance and subsequent suboptimal clinical outcomes underscore the critical imperative for enhanced therapeutic alternatives and management protocols. The challenge of effectively treating fungal infections, compounded by the protracted timelines involved in developing novel drugs, underscores the pressing need to explore alternative therapeutic avenues. Among these, drug repurposing emerges as a particularly promising and expeditious solution, providing cost-effective solutions and safety benefits. In the fight against life-threatening resistant fungal infections, the idea of repurposing existing medications has encouraged research into both established and new compounds as a last-resort therapy. This chapter seeks to provide a comprehensive overview of contemporary antifungal drugs, as well as their key resistance mechanisms. Additionally, it seeks to provide insight into the antimicrobial properties of non-traditional drugs, thereby offering a holistic perspective on the evolving landscape of antifungal therapeutics.

Halogenated Antimicrobial Agents to Combat Drug-Resistant Pathogens

Antimicrobial resistance presents us with a potential global crisis as it undermines the abilities of conventional antibiotics to combat pathogenic microbes. The history of antimicrobial agents is replete with examples of scaffolds containing halogens. In this review, we discuss the impacts of halogen atoms in various antibiotic types and antimicrobial scaffolds and their modes of action, structure-activity relationships, and the contributions of halogen atoms in antimicrobial activity and drug resistance. Other halogenated molecules, including carbohydrates, peptides, lipids, and polymeric complexes, are also reviewed, and the effects of halogenated scaffolds on pharmacokinetics, pharmacodynamics, and factors affecting antimicrobial and antivirulence activities are presented. Furthermore, the potential of halogenation to circumvent antimicrobial resistance and rejuvenate impotent antibiotics is addressed. This review provides an overview of the significance of halogenation, the abilities of halogens to interact in biomolecular settings and enhance pharmacological properties, and their potential therapeutic usages in preventing a postantibiotic era. SIGNIFICANCE STATEMENT: Antimicrobial resistance and the increasing impotence of antibiotics are critical threats to global health. The roles and importance of halogen atoms in antimicrobial drug scaffolds have been established, but comparatively little is known of their pharmacological impacts on drug resistance and antivirulence activities. This review is the first to extensively evaluate the roles of halogen atoms in various antibiotic classes and pharmacological scaffolds and to provide an overview of their ability to overcome antimicrobial resistance.

Sex-based influential factors for dental caries in patients with schizophrenia

BACKGROUND

Schizophrenia is a common mental disorder that seriously affects patients' daily lives and brings heavy psychological and economic burdens to their families and society. The oral problems of patients with schizophrenia are gradually gaining attention, among which dental caries are among the most common oral diseases. Sex differences may be related not only to the various clinical symptoms of schizophrenia but also to different oral hygiene statuses; therefore, the main purpose of this paper is to investigate sex differences related to influencing factors for dental caries in patients with schizophrenia.

METHOD

Inpatients with schizophrenia over 18 years old were included in this study, and multidimensional indicators such as demographics, symptom and cognitive impairment assessments, medications, and the caries index of decayed, missing, and filled teeth (DMFT) were collected. An analysis of sex-based influential factors for dental caries in schizophrenia patients was performed.

RESULTS

Four-hundred and ninety-six patients with schizophrenia were included, with a mean age of 46.73 ± 12.23 years, of which 142 were females and 354 were males. The mean DMFT was significantly higher in males (8.81 ± 8.50) than in females (5.63 ± 6.61, p < 0.001), and the odd ratio of caries in males to females was significantly higher as well (OR = 2.305, p < 0.001). The influential factors of caries in male patients were independently associated with age and smoking status, in which current smokers were at the highest risk for developing caries, and different smoking statuses had various influencing factors for caries. The influencing factors for caries in female patients were independently associated with age, antipsychotic dose, PANSS-positive symptoms, and MMSE levels.

CONCLUSION

Our findings suggest sex differences exist among influential factors for caries in patients with schizophrenia. These risk factors may even be associated with and affect the treatment and prognosis of psychiatric symptoms in patients. Therefore, oral hygiene management of patients with schizophrenia should be enhanced. These differential factors provide new visions and ideas for formulating individual interventions, treatments, and care priorities.

Azole potentiation in Candida species

Fungal infections are rising, with over 1.5 billion cases and more than 1 million deaths recorded each year. Among these, Candida infections are frequent in at-risk populations and the rapid development of drug resistance and tolerance contributes to their clinical persistence. Few antifungal drugs are available, and their efficacy is declining due to the environmental overuse and the expansion of multidrug-resistant species. One way to prolong their utility is by applying them in combination therapy. Here, we highlight recently described azole potentiators belonging to different categories: natural, repurposed, or novel compounds. We showcase examples of molecules and discuss their identified or proposed mode of action. We also emphasise the challenges in azole potentiator development, compounded by the lack of animal testing, the overreliance on Candida albicans and Candida auris, as well as the limited understanding of compound efficacy.

Discovery and development of novel substituted monohydrazides as potent antifungal agents

Novel substituted monohydrazides synthesized for this study displayed broad-spectrum activity against various fungal strains, including a panel of clinically relevant Candida auris strains. The activity of these compounds was either comparable or superior to amphotericin B against most of the fungal strains tested. These compounds possessed fungistatic activity in a time-kill assay and exhibited no mammalian cell toxicity. In addition, they prevented the formation of fungal biofilms. Even after repeated exposures, the Candida albicans ATCC 10231 (strain A) fungal strain did not develop resistance to these monohydrazides.

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.

Augmenting Azoles with Drug Synergy to Expand the Antifungal Toolbox

Fungal infections impact the lives of at least 12 million people every year, killing over 1.5 million. Wide-spread use of fungicides and prophylactic antifungal therapy have driven resistance in many serious fungal pathogens, and there is an urgent need to expand the current antifungal arsenal. Recent research has focused on improving azoles, our most successful class of antifungals, by looking for synergistic interactions with secondary compounds. Synergists can co-operate with azoles by targeting steps in related pathways, or they may act on mechanisms related to resistance such as active efflux or on totally disparate pathways or processes. A variety of sources of potential synergists have been explored, including pre-existing antimicrobials, pharmaceuticals approved for other uses, bioactive natural compounds and phytochemicals, and novel synthetic compounds. Synergy can successfully widen the antifungal spectrum, decrease inhibitory dosages, reduce toxicity, and prevent the development of resistance. This review highlights the diversity of mechanisms that have been exploited for the purposes of azole synergy and demonstrates that synergy remains a promising approach for meeting the urgent need for novel antifungal strategies.

HTR1A Inhibits the Progression of Triple-Negative Breast Cancer via TGF-β Canonical and Noncanonical Pathways

Triple-negative breast cancer is the most aggressive subtype of breast cancer and the incidence of depression in breast cancer patients is high, which leading to worse survival and increased risk of recurrence. The effect of antidepressants on breast cancer patients remains contradictory, which might be due to variations in antidepression targets. Therefore, there is significant value to explore the antitumor potential of antidepressants and discover new therapeutic targets for breast patients. The authors screen antidepressant-related oncogenes or suppressors by using siRNAs. After combining functional experiments with online database analysis, 5-hydroxytryptamine receptor 1A (HTR1A is selected with antitumor potential in breast cancer cells in vivo and in vitro. RNA-seq analysis and coimmunoprecipitation assays indicate that HTR1A interacts with TRIM21 and PSMD7 to inhibit the degradation of TβRII through the ubiquitin-proteasome pathway, thereby inhibiting the transforming growth factor-β (TGF-β) canonical and noncanonical pathway. In addition, HTR1A is an independent predictive factor for breast cancer patients. The combined treatment of HTR1A agonists with demethylation drugs may significantly improve patient survival. It is of great significance to clarify the function and mechanism of the depression-related gene HTR1A in breast cancer, which might provide a new approach for triple-negative breast cancer patients.

Alternative Treatment Strategies for Secondary Bacterial and Fungal Infections Associated with COVID-19

Antimicrobials are essential for combating infectious diseases. However, an increase in resistance to them is a major cause of concern. The empirical use of drugs in managing COVID-19 and the associated secondary infections have further exacerbated the problem of antimicrobial resistance. Hence, the situation mandates exploring and developing efficient alternatives for the treatment of bacterial and fungal infections in patients suffering from COVID-19 or other viral infections. In this review, we have described the alternatives to conventional antimicrobials that have shown promising results and are at various stages of development. An acceleration of efforts to investigate their potential as therapeutics can provide more treatment options for clinical management of drug-resistant secondary bacterial and fungal infections in the current pandemic and similar potential outbreaks in the future. The alternatives include bacteriophages and their lytic enzymes, anti-fungal enzymes, antimicrobial peptides, nanoparticles and small molecule inhibitors among others. What is required at this stage is to critically examine the challenges in developing the listed compounds and biomolecules as therapeutics and to establish guidelines for their safe and effective application within a suitable time frame. In this review, we have attempted to highlight the importance of rational use of antimicrobials in patients suffering from COVID-19 and boost the deployment of alternative therapeutics.

Antimicrobial Properties of Antidepressants and Antipsychotics-Possibilities and Implications

The spreading of antibiotic resistance is responsible annually for over 700,000 deaths worldwide, and the prevision is that this number will increase exponentially. The identification of new antimicrobial treatments is a challenge that requires scientists all over the world to collaborate. Developing new drugs is an extremely long and costly process, but it could be paralleled by drug repositioning. The latter aims at identifying new clinical targets of an “old” drug that has already been tested, approved, and even marketed. This approach is very intriguing as it could reduce costs and speed up approval timelines, since data from preclinical studies and on pharmacokinetics, pharmacodynamics, and toxicity are already available. Antidepressants and antipsychotics have been described to inhibit planktonic and sessile growth of different yeasts and bacteria. The main findings in the field are discussed in this critical review, along with the description of the possible microbial targets of these molecules. Considering their antimicrobial activity, the manuscript highlights important implications that the administration of antidepressants and antipsychotics may have on the gut microbiome.

Inhibition of Pseudomonas aeruginosa Alginate Synthesis by Ebselen Oxide and Its Analogues

Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that is frequently found in the airways of cystic fibrosis (CF) patients due to the dehydrated mucus that collapses the underlying cilia and prevents mucociliary clearance. During this life-long chronic infection, P. aeruginosa cell accumulates mutations that lead to inactivation of the mucA gene that results in the constitutive expression of algD-algA operon and the production of alginate exopolysaccharide. The viscous alginate polysaccharide further occludes the airways of CF patients and serves as a protective matrix to shield P. aeruginosa from host immune cells and antibiotic therapy. Development of inhibitors of alginate production by P. aeruginosa would reduce the negative impact from this viscous polysaccharide. In addition to transcriptional regulation, alginate biosynthesis requires allosteric activation by bis (3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP) binding to an Alg44 protein. Previously, we found that ebselen (Eb) and ebselen oxide (EbO) inhibited diguanylate cyclase from synthesizing c-di-GMP. In this study, we show that EbO, Eb, ebsulfur (EbS), and their analogues inhibit alginate production. Eb and EbS can covalently modify the cysteine 98 (C98) residue of Alg44 and prevent its ability to bind c-di-GMP. However, P. aeruginosa with Alg44 C98 substituted with alanine or serine was still inhibited for alginate production by Eb and EbS. Our results indicate that EbO, Eb, and EbS are lead compounds for reducing alginate production by P. aeruginosa. Future development of these inhibitors could provide a potential treatment for CF patients infected with mucoid P. aeruginosa.

Drug Repurposing in Medical Mycology: Identification of Compounds as Potential Antifungals to Overcome the Emergence of Multidrug-Resistant Fungi

Immunodepression, whether due to HIV infection or organ transplantation, has increased human vulnerability to fungal infections. These conditions have created an optimal environment for the emergence of opportunistic infections, which is concomitant to the increase in antifungal resistance. The use of conventional antifungal drugs as azoles and polyenes can lead to clinical failure, particularly in immunocompromised individuals. Difficulties related to treating fungal infections combined with the time required to develop new drugs, require urgent consideration of other therapeutic alternatives. Drug repurposing is one of the most promising and rapid solutions that the scientific and medical community can turn to, with low costs and safety advantages. To treat life-threatening resistant fungal infections, drug repurposing has led to the consideration of well-known and potential molecules as a last-line therapy. The aim of this review is to provide a summary of current antifungal compounds and their main resistance mechanisms, following by an overview of the antifungal activity of non-traditional antimicrobial drugs. We provide their eventual mechanisms of action and the synergistic combinations that improve the activity of current antifungal treatments. Finally, we discuss drug repurposing for the main emerging multidrug resistant (MDR) fungus, including the Candida auris, Aspergillus or Cryptococcus species.

Mechanistic Understanding of Candida albicans Biofilm Formation and Approaches for Its Inhibition

In recent years, the demand for novel antifungal therapies has increased several- folds due to its potential to treat severe biofilm-associated infections. Biofilms are made by the sessile microorganisms attached to the abiotic or biotic surfaces, enclosed in a matrix of exopolymeric substances. This results in new phenotypic characteristics and intrinsic resistance from both host immune response and antimicrobial drugs. Candida albicans biofilm is a complex association of hyphal cells that are associated with both abiotic and animal tissues. It is an invasive fungal infection and acts as an important virulent factor. The challenges linked with biofilm-associated diseases have urged scientists to uncover the factors responsible for the formation and maturation of biofilm. Several strategies have been developed that could be adopted to eradicate biofilm-associated infections. This article presents an overview of the role of C. albicans biofilm in its pathogenicity, challenges it poses and threats associated with its formation. Further, it discusses strategies that are currently available or under development targeting prostaglandins, quorum-sensing, changing surface properties of biomedical devices, natural scaffolds, and small molecule-based chemical approaches to combat the threat of C. albicans biofilm. This review also highlights the recent developments in finding ways to increase the penetration of drugs into the extracellular matrix of biofilm using different nanomaterials against C. albicans.

Deep-learning based repurposing of FDA-approved drugs against Candida albicans dihydrofolate reductase and molecular dynamics study

Candida albicans causes the fatal fungal bloodstream infection in humans called Candidiasis. Most of the Candida species are resistant to the antifungals used to treat them. Drug-resistant C. albicans poses very serious public health issues. To overcome this, the development of effective drugs with novel mechanism(s) of action is requisite. Drug repurposing is considered a viable alternative approach to overcome the above issue. In the present study, we have attempted to identify drugs that could target the essential enzyme, dihydrofolate reductase of C. albicans (CaDHFR) to find out potent and selective antifungal antifolates. FDA-approved-drug-library from the Selleck database containing 1930 drugs was screened against CaDHFR using deep-learning, molecular docking, X-score and similarity search methods. The screened compounds showing better binding with CaDHFR were subjected to molecular dynamics simulation (MDS). The results of post-MDS analysis like RMSD, RMSF, RG, SASA, the number of hydrogen bonds and PCA suggest that Paritaprevir, Lumacaftor and Rifampin can make good interaction with CaDHFR. Furthermore, analysis of binding free energy corroborated the stability of interactions as they had binding energy of -114.91 kJ mol^-1, -79.22 kJ mol^-1 and -78.52 kJ mol^-1 for Paritaprevir, Lumacaftor and Rifampin respectively as compared to the reference (-63.10 kJ mol^-1). From the results, we conclude that these drugs have great potential to inhibit CaDHFR and would add to the drug discovery against candidiasis, and hence these drugs for repurposing should be explored further.

Potentiated inhibition of Trichoderma virens and other environmental fungi by new biocide combinations

Abstract

Fungi cause diverse, serious socio-economic problems, including biodeterioration of valuable products and materials that spawns a biocides industry worth ~$11 billion globally. To help combat environmental fungi that commonly colonise material products, this study tested the hypothesis that combination of an approved fungicide with diverse agents approved by the FDA (Food and Drug Administration) could reveal potent combinatorial activities with promise for fungicidal applications. The strategy to use approved compounds lowers potential development risks for any effective combinations. A high-throughput assay of 1280 FDA-approved compounds was conducted to find those that potentiate the effect of iodopropynyl-butyl-carbamate (IPBC) on the growth of Trichoderma virens; IPBC is one of the two most widely used Biocidal Products Regulations–approved fungicides. From this library, 34 compounds in combination with IPBC strongly inhibited fungal growth. Low-cost compounds that gave the most effective growth inhibition were tested against other environmental fungi that are standard biomarkers for resistance of synthetic materials to fungal colonisation. Trifluoperazine (TFZ) in combination with IPBC enhanced growth inhibition of three of the five test fungi. The antifungal hexetidine (HEX) potentiated IPBC action against two of the test organisms. Testable hypotheses on the mechanisms of these combinatorial actions are discussed. Neither IPBC + TFZ nor IPBC + HEX exhibited a combinatorial effect against mammalian cells. These combinations retained strong fungal growth inhibition properties after incorporation to a polymer matrix (alginate) with potential for fungicide delivery. The study reveals the potential of such approved compounds for novel combinatorial applications in the control of fungal environmental opportunists.

Key points

• Search with an approved fungicide to find new fungicidal synergies in drug libraries.

• New combinations inhibit growth of key environmental fungi on different matrices.

• The approach enables a more rapid response to demand for new biocides.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00253-021-11211-3.

Current and promising pharmacotherapeutic options for candidiasis

Introduction: Candida spp. are commensal yeasts capable of causing infections such as superficial, oral, vaginal, or systemic infections. Despite medical advances, the antifungal pharmacopeia remains limited and the development of alternative strategies is needed.Areas covered: We discuss available treatments for Candida spp. infections, highlighting advantages and limitations related to pharmacokinetics, cytotoxicity, and antimicrobial resistance. Moreover, we present new perspectives to improve the activity of the available antifungals, discussing their immunomodulatory potential and advances on drug delivery carriers. New therapeutic approaches are presented including recent synthesized antifungal compounds (Enchochleated-Amphotericin B, tetrazoles, rezafungin, enfumafungin, manogepix and arylamidine); drug repurposing using a diversity of antibacterial, antiviral and non-antimicrobial drugs; combination therapies with different compounds or photodynamic therapy; and innovations based on nano-particulate delivery systems.Expert opinion: With the lack of novel drugs, the available assets must be leveraged to their best advantage through modifications that enhance delivery, efficacy, and solubility. However, these efforts are met with continuous challenges presented by microbes in their infinite plight to resist and survive therapeutic drugs. The pharmacotherapeutic options in development need to focus on new antimicrobial targets. The success of each antimicrobial agent brings strategic insights to the next phased approach in treatingCandida spp. infections.

Broad-Spectrum Antifungal Agents: Fluorinated Aryl- and Heteroaryl-Substituted Hydrazones

Fluorinated aryl- and heteroaryl-substituted monohydrazones displayed excellent broad-spectrum activity against various fungal strains, including a panel of clinically relevant Candida auris strains relative to a control antifungal agent, voriconazole (VRC). These monohydrazones displayed less hemolysis of murine red blood cells than that of VRC at the same concentrations, possessed fungicidal activity in a time-kill study, and exhibited no mammalian cell cytotoxicity. In addition, these monohydrazones prevented the formation of biofilms that otherwise block antibiotic effectiveness and did not trigger the development of resistance when exposed to C. auris AR Bank # 0390 over 15 passages.

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.

Repurposing Nonantifungal Approved Drugs for Synergistic Targeting of Fungal Pathogens

With the spread of drug resistance, new antimicrobials are urgently needed. Here, we set out to tackle this problem by high-throughput exploration for novel antifungal synergies among combinations of approved, nonantifungal drugs; a novel strategy exploiting the potential of alternative targets, low chemicals usage and low development risk. We screened the fungal pathogen Candida albicans by combining a small panel of nonantifungal drugs (all in current use for other clinical applications) with 1280 compounds from an approved drug library. Screens at sublethal concentrations of the antibiotic paromomycin (PM), the antimalarial primaquine (PQ), or the anti-inflammatory drug ibuprofen (IF) revealed a total of 17 potential strong, synergistic interactions with the library compounds. Susceptibility testing with the most promising combinations corroborated marked synergies [fractional inhibitory concentration (FIC) indices ≤0.5] between PM + β-escin, PQ + celecoxib, and IF + pentamidine, reducing the MICs of PM, PQ, and IF in C. albicans by >64-, 16-, and 8-fold, respectively. Paromomycin + β-escin and PQ + celecoxib were effective also against C. albicans biofilms, azole-resistant clinical isolates, and other fungal pathogens. Actions were specific, as no synergistic effect was observed in mammalian cells. Mode of action was investigated for one of the combinations, revealing that PM + β-escin synergistically increase the error-rate of mRNA translation and suggesting a different molecular target to current antifungals. The study unveils the potential of the described combinatorial strategy in enabling acceleration of drug-repurposing discovery for combatting fungal pathogens.

Repurposing of respiratory drug theophylline against Candida albicans: mechanistic insights unveil alterations in membrane properties and metabolic fitness

AIMS

Drug repurposing is an attractive chemotherapeutic strategy that serves to make up for the inadequacy of current antifungal drugs. The present study aims to repurpose theophylline (THP) against Candida albicans. THP is a methylxanthine derived from cocoa beans and tea extracts, generally used as the first-line drug for asthma and other respiratory disorders.

METHODS AND RESULTS

We investigated the antifungal activity of THP against C. albicans and non-albicans species. Mechanistic insights revealed that THP induces membrane damage. Enhanced ionic disturbances and depleted ergosterol levels with the concomitant rise in membrane fluidity due to elevated flippase activity confirmed the membrane damaging effect. THP impeded the metabolic adaptability of C. albicans by inhibiting malate synthase and isocitrate lyase enzymes of the glyoxylate cycle. In vivo efficacy of THP was depicted by increased survival of C. albicans infected Caenorhabditis elegans model.

CONCLUSIONS

This study elucidates the antifungal potential of THP with mechanistic insights.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study unveils the antifungal potential of THP, a known respiratory drug that can be further utilized for a wider range of applications such as combating fungal infections. The effect of THP with the known antifungal drugs can be exploited in the combinatorial drug approach for treating candidiasis.

Drug Repurposing of Haloperidol: Discovery of New Benzocyclane Derivatives as Potent Antifungal Agents against Cryptococcosis and Candidiasis

Despite the high morbidity and mortality of invasive fungal infections (IFIs), effective and safe antifungal agents are rather limited. Starting from antifungal lead compound haloperidol that was identified by drug repurposing, a series of novel benzocyclane derivatives were designed, synthesized, and assayed. Several compounds showed improved antifungal potency and broader antifungal spectra. Particularly, compound B10 showed good inhibitory activities against a variety of fungal pathogens and was proven to be an inhibitor of several virulence factors important for drug resistance. In the in vivo cryptococcosis and candidiasis models, compound B10 could effectively reduce the brain fungal burden of Cryptococcus neoformans and synergize with fluconazole to treat resistant Candida albicans infections. Preliminary antifungal mechanism studies revealed that compound B10 regained cell membrane damage and down-regulated the overexpression of ERG11 and MDR1 genes when used in combination with fluconazole. Taken together, haloperidol derivative B10 represents a promising lead compound for the development of a new generation of antifungal agents.

A comprehensive overview of the medicinal chemistry of antifungal drugs: perspectives and promise

The emergence of new fungal pathogens makes the development of new antifungal drugs a medical imperative that in recent years motivates the talents of numerous investigators across the world. Understanding not only the structural families of these drugs but also their biological targets provides a rational means for evaluating the merits and selectivity of new agents for fungal pathogens and normal cells. An equally important aspect of modern antifungal drug development takes a balanced look at the problems of drug potency and drug resistance. The future development of new antifungal agents will rest with those who employ synthetic and semisynthetic methodology as well as natural product isolation to tackle these problems and with those who possess a clear understanding of fungal cell architecture and drug resistance mechanisms. This review endeavors to provide an introduction to a growing and increasingly important literature, including coverage of the new developments in medicinal chemistry since 2015, and also endeavors to spark the curiosity of investigators who might enter this fascinatingly complex fungal landscape.

Synergistic combinations of azoles and antihistamines against Candida species in vitro

Fungal infections are a major cause of skin and mucosal membrane disease. Immunocompromised individuals, such as those undergoing chemotherapy, are most susceptible to fungal infections. With a growing population of immunocompromised patients, there are many reports of increasing numbers of infections and of fungal strains resistant to current antifungals. One way to treat drug-resistant infections is to administer combinations of drugs to patients. Azoles are the most prescribed antifungals, as they are broad-spectrum and orally bioavailable. Terfenadine (TERF) and ebastine (EBA) are second-generation antihistamines, with EBA being used in many countries. In this study, we explored combinations of seven azole antifungals and two antihistamines (TERF and EBA) against a panel of 13 Candida fungal strains. We found 55 out of 91 combinations tested of TERF and EBA against the various fungal strains to be synergistic with the azoles. To evaluate the efficiency of these combinations to inhibit fungal growth, we performed time-kill assays. We also investigated the ability of these combinations to disrupt biofilm formation. Finally, we tested the specificity of the combinations towards fungal cells by mammalian cytotoxicity assays. These findings suggest a potential new strategy for targeting drug-resistant Candida infections.

Astrocytes are direct cellular targets of lithium treatment: novel roles for lysyl oxidase and peroxisome-proliferator activated receptor-γ as astroglial targets of lithium

Astrocytes are multifunctional glial cells that play essential roles in supporting synaptic signalling and white matter-associated connectivity. There is increasing evidence that astrocyte dysfunction is involved in several brain disorders, including bipolar disorder (BD), depression and schizophrenia. The mood stabiliser lithium is a frontline treatment for BD, but the mechanisms of action remain unclear. Here, we demonstrate that astrocytes are direct targets of lithium and identify unique astroglial transcriptional networks that regulate specific molecular changes in astrocytes associated with BD and schizophrenia, together with Alzheimer's disease (AD). Using pharmacogenomic analyses, we identified novel roles for the extracellular matrix (ECM) regulatory enzyme lysyl oxidase (LOX) and peroxisome proliferator-activated receptor gamma (PPAR-γ) as profound regulators of astrocyte morphogenesis. This study unravels new pathophysiological mechanisms in astrocytes that have potential as novel biomarkers and potential therapeutic targets for regulating astroglial responses in diverse neurological disorders.

How We Approach Combination Antifungal Therapy for Invasive Aspergillosis and Mucormycosis in Transplant Recipients

Invasive aspergillosis and mucormycosis are life-threatening infections in solid organ and hematopoietic cell transplant recipients. Despite medical advancements in the care of these patients and the availability of new mold-active drugs, the outcomes remain suboptimal. Therefore, there has been increased interest in the use of combination antifungal therapy, in hopes that leveraging the possible in vitro synergy of these agents will improve the prognosis of invasive mold disease. However, there has been a large disconnect between the results of experimental and clinical investigations, as clinical studies have not unequivocally demonstrated the superiority of combination therapy over monotherapy. This is particularly true for mucormycosis, where the rarity of the condition has made it nearly impossible to prospectively study novel therapeutic strategies. We review the current standard of antifungal therapy and the preclinical and clinical data addressing the merit of combination therapy, and we provide guidance to optimize the management of these mycoses.

Drug Repurposing for the Treatment of Bacterial and Fungal Infections

Multidrug-resistant (MDR) pathogens pose a well-recognized global health threat that demands effective solutions; the situation is deemed a global priority by the World Health Organization and the European Centre for Disease Prevention and Control. Therefore, the development of new antimicrobial therapeutic strategies requires immediate attention to avoid the ten million deaths predicted to occur by 2050 as a result of MDR bacteria. The repurposing of drugs as therapeutic alternatives for infections has recently gained renewed interest. As drugs approved by the United States Food and Drug Administration, information about their pharmacological characteristics in preclinical and clinical trials is available. Therefore, the time and economic costs required to evaluate these drugs for other therapeutic applications, such as the treatment of bacterial and fungal infections, are mitigated. The goal of this review is to provide an overview of the scientific evidence on potential non-antimicrobial drugs targeting bacteria and fungi. In particular, we aim to: (i) list the approved drugs identified in drug screens as potential alternative treatments for infections caused by MDR pathogens; (ii) review their mechanisms of action against bacteria and fungi; and (iii) summarize the outcome of preclinical and clinical trials investigating approved drugs that target these pathogens.

N,N'-diaryl-bishydrazones in a biphenyl platform: Broad spectrum antifungal agents

N,N'-Diaryl-bishydrazones of [1,1'-biphenyl]-3,4'-dicarboxaldehyde, [1,1'-biphenyl]-4,4'-dicarboxaldehyde, and 4,4'-bisacetyl-1,1-biphenyl exhibited excellent antifungal activity against a broad spectrum of filamentous and non-filamentous fungi. These N,N'-diaryl-bishydrazones displayed no antibacterial activity in contrast to previously reported N,N'-diamidino-bishydrazones and N-amidino-N'-aryl-bishydrazones. The leading candidate, 4,4'-bis((E)-1-(2-(4-fluorophenyl)hydrazono)ethyl)-1,1'-biphenyl, displayed less hemolysis of murine red blood cells at concentrations at or below that of a control antifungal agent (voriconazole), was fungistatic in a time-kill study, and possessed no mammalian cytotoxicity and no toxicity with respect to hERG inhibition.

Repurposing approach identifies new treatment options for invasive fungal disease

Drug repositioning is the process of discovery, validation and marketing of previously approved drugs for new indications. Our aim was drug repositioning, using ligand-based and structure-based computational methods, of compounds that are similar to two hit compounds previously selected by our group that show promising antifungal activity. Through the ligand-based method, 100 compounds from each of three databases (MDDR, DrugBank and TargetMol) were selected by the Tanimoto coefficient, as similar to LMM5 or LMM11. These compounds were analyzed by the scaffold trees, and up to 10 compounds from each database were selected. The structure-based method (molecular docking) using thioredoxin reductase as the target drug was performed as a complementary approach, resulting in six compounds that were tested in an in vitro assay. All compounds, particularly raltegravir, showed antifungal activity against the genus Paracoccidioides. Raltegravir, an antiviral drug, showed promising antifungal activity against the experimental murine paracoccidioidomycosis, with significant reduction of the fungal burden and decreased alterations in the lung structure of mice treated with 1 mg/kg of raltegravir. In conclusion, the combination of two in silico methods for drug repositioning was able to select an antiviral drug with promising antifungal activity for treatment of paracoccidioidomycosis.

Differential Effects of Linkers on the Activity of Amphiphilic Tobramycin Antifungals

As the threat associated with fungal infections continues to rise and the availability of antifungal drugs remains a concern, it becomes obvious that the need to bolster the antifungal armamentarium is urgent. Building from our previous findings of tobramycin (TOB) derivatives with antifungal activity, we further investigate the effects of various linkers on the biological activity of these aminoglycosides. Herein, we analyze how thioether, sulfone, triazole, amide, and ether functionalities affect the antifungal activity of alkylated TOB derivatives against 22 Candida, Cryptococcus, and Aspergillus species. We also evaluate their impact on the hemolysis of murine erythrocytes and the cytotoxicity against mammalian cell lines. While the triazole linker appears to confer optimal activity overall, all of the linkers incorporated into the TOB derivatives resulted in compounds that are very effective against the Cryptococcus neoformans species, with MIC values ranging from 0.48 to 3.9 μg/mL.

Spectroscopic (FT-IR, FT-Raman, UV, 1H and 13C NMR) insights, electronic profiling and DFT computations on ({(E)-[3-(1H-imidazol-1-yl)-1-phenylpropylidene] amino}oxy)(4-nitrophenyl)methanone, an imidazole-bearing anti-Candida agent

The anti-Candida agent, ({(E)-[3-(1H-imidazol-1-yl)-1-phenylpropylidene]amnio}oxy(4-nitropheny) methanone (IPAONM), was subjected to comprehensive spectroscopic (FT-IR, FT-Raman, UV–Vis 1H and 13C NMR) characterization as well as Hartree Fock and density functional theory computation studies. The selected optimized geometric bond lengths and bond angles of the IPAONM molecule were compared with the experimental values. The calculated wavenumbers have been scaled and compared with the experimental spectra. Mulliken charges and natural bond orbital analysis of the title molecule were calculated and interpreted. The energy and oscillator strengths of the IPAONM molecule were calculated by time-dependent density functional theory (TD-DFT). In addition, frontier molecular orbitals and molecular electrostatic potential diagram of the title compound were computed and analyzed. A study on the electronic properties, such as HOMO, HOMO-1, LUMO and LUMO+1 energies was carried out using TD-DFT approach. The 1H and 13C NMR chemical shift values of the title compound were calculated by the gauge independent atomic orbital method and compared with the experimental results.

Repurposing psychiatric drugs as anti-cancer agents

Cancer is a major public health problem and one of the leading contributors to the global disease burden. The high cost of development of new drugs and the increasingly severe burden of cancer globally have led to increased interest in the search and development of novel, affordable anti-neoplastic medications. Antipsychotic drugs have a long history of clinical use and tolerable safety; they have been used as good targets for drug repurposing. Being used for various psychiatric diseases for decades, antipsychotic drugs are now reported to have potent anti-cancer properties against a wide variety of malignancies in addition to their antipsychotic effects. In this review, an overview of repurposing various psychiatric drugs for cancer treatment is presented, and the putative mechanisms for the anti-neoplastic actions of these antipsychotic drugs are reviewed.

Synthesis, Single Crystal X-ray Analysis, and Antifungal Profiling of Certain New Oximino Ethers Bearing Imidazole Nuclei

Fungal infections threaten human health, particularly in immune-compromised patients worldwide. Although there are a large number of antifungal agents available, the desired clinical attributes for the treatment of fungal infections have not yet been achieved. Azoles are the mainstay class of the clinically used antifungal agents. In the current study, the synthesis, spectroscopic characterization, and antifungal activity of certain new oximino ethers Va–n bearing imidazole nuclei are reported. The (E)-configuration of the imine double bond of the synthesized compounds Va–n has been confirmed via single crystal X-ray analysis of compound Vi as a representative example of this class of compounds. The molecular structure of compound Vi was crystallized in the monoclinic, P2₁/c, a = 18.7879(14) Å, b = 5.8944(4) Å, c = 16.7621(12) Å, β = 93.063(3)°, V = 1855.5(2) ų, Z = 4. The in vitro antifungal activity of the synthesized compounds Va–n were evaluated using diameter of the inhibition zone (DIZ) and minimum inhibitory concentration (MIC) assays against different fungal strains. Compound Ve manifested anti-Candida albicans activity with an MIC value of 0.050 µmol/mL, being almost equipotent with the reference antifungal drug fluconazole (FLC),while compounds Vi and Vn are the most active congeners against Candida parapsilosis, being equipotent and about twenty-three times more potent than FLC with an MIC value of 0.002 µmol/mL. The results of the current report might support the development of new potent and safer antifungal azoles.