Repurposing Approach Identifies Auranofin with Broad Spectrum Antifungal Activity That Targets Mia40-Erv1 Pathway

Aurothioglucose encapsulated nanoparticles fostered neuroprotection in streptozotocin-induced Alzheimer's disease

Alzherimer's disease (AD) is an age-dependent ubiquitous ailment worldwide with limited therapies that only alleviate the symptoms of AD but do not cure them entirely because of the restricted blood-brain barrier passage of the drug. Hence with new advanced technology, nanoparticles can offer an opportunity as the active candidate to overcome the above limitations. Aurothioglucose, a synthetic glucose derivative of the gold compound, has been clinically proven to be an effective anti-inflammatory drug for rheumatic arthritis. Recently, several scientific groups have developed gold nanoparticle preparations and tested them for the treatment of dementia. This study was planned to prepare the PLGA nanoparticles of aurothioglucose (ATG) and check the neuroprotective potential against STZ-induced AD in rats. The nanoparticles were prepared using the double emulsion solvent evaporation method and characterized for various parameters such as drug-excipient interaction, particle size, zeta potential, and morphology. Then, rats were injected STZ (3 mg/kg/i.c.v., days 1 and 3) and ATG (5 and 10 mg/kg/s.c.), ATG NPs (2.5 and 5 mg/kg/s.c.) and donepezil (2 mg/kg/p.o) from 15th to 29th day. Behavior parameters were performed using an actophotometer, MWM, and ORT. On the 30th day, all the animals were sacrificed, and the brains were isolated for estimating biochemical, neurochemical, and proinflammatory markers. It was observed that ATG NPs significantly restored all behavior and neurotransmitter alterations caused by STZ. Also, it increased antioxidant levels and decreased inflammatory cytokines significantly, then ATG alone. Thus, the study suggests that ATG loaded PLGA NPs could be used as a novel therapeutic strategy to slow the process of AD.

An overview to drug repurposing

Identification and implementation of novel drug are not only time consuming and expensive but also it poses huge challenge to reach into the market. Currently, thousands of USFDA approved drugs licence are being expired that can be repurposed for treating other diseases. Drug repurposing is an alternative solution to reduce time, cost and steps for development of drugs and their applications for treating disease. The current chapter emphases to brief the steps involved in drug discovery and drug repurposing. The chapter also includes repurposed drugs for treating bacterial, fungal and viral diseases. Unlocking the potential of already existed drug and repurposing them for other diseases that could accelerate drug discovery and aid in managing outbreaks.

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.

An update on the global treatment of invasive fungal infections

Fungal infections are a serious problem affecting many people worldwide, creating critical economic and medical consequences. Fungi are ubiquitous and can cause invasive diseases in individuals mostly living in developing countries or with weakened immune systems, and antifungal drugs currently available have important limitations in tolerability and efficacy. In an effort to counteract the high morbidity and mortality rates associated with invasive fungal infections, various approaches are being utilized to discover and develop new antifungal agents. This review discusses the challenges posed by fungal infections, outlines different methods for developing antifungal drugs and reports on the status of drugs currently in clinical trials, which offer hope for combating this serious global problem.

Auranofin coated catheters inhibit bacterial and fungal biofilms in a murine subcutaneous model

Microbe entry through catheter ports can lead to biofilm accumulation and complications from catheter-related bloodstream infection and ultimately require antimicrobial treatment and catheter replacement. Although strides have been made with microbial prevention by applying standardized antiseptic techniques during catheter implantation, both bacterial and fungal microbes can present health risks to already sick individuals. To reduce microbial adhesion, murine and human catheters were coated with polyurethane and auranofin using a dip coating method and compared to non-coated materials. Upon passage of fluid through the coated material in vitro, flow dynamics were not impacted. The unique antimicrobial properties of the coating material auranofin has shown inhibitory activity against bacteria such as Staphylococcus aureus and fungi such as Candida albicans. Auranofin coating on catheters at 10mg/mL reduced C. albicans accumulation in vitro from 2.0 x 10⁸ to 7.8 x 10⁵ CFU for mouse catheters and from 1.6 x 10⁷ to 2.8 x 10⁶ for human catheters, showing an impact to mature biofilms. Assessment of a dual microbe biofilm on auranofin-coated catheters resulted in a 2-log reduction in S. aureus and a 3-log reduction in C. albicans compared to uncoated catheters. In vivo assessment in a murine subcutaneous model demonstrated that catheters coated with 10 mg/mL auranofin reduced independent S. aureus and C. albicans accumulation by 4-log and 1-log, respectively, compared to non-coated catheters. In conclusion, the auranofin-coated catheters demonstrate proficiency at inhibiting multiple pathogens by decreasing S. aureus and C. albicans biofilm accumulation.

Atazanavir Resensitizes Candida auris to Azoles

Candida auris represents an urgent health threat. Here, we identified atazanavir as a potent drug capable of resensitizing C. auris clinical isolates to the activity of azole antifungals. Atazanavir was able to significantly inhibit the efflux pumps, glucose transport, and ATP synthesis of all tested isolates of C. auris. In addition, the combination of itraconazole with atazanavir-ritonavir significantly reduced the burden of azole-resistant C. auris in murine kidneys by 1.3 log10 (95%), compared to itraconazole alone.

Redox-Based Strategies against Infections by Eukaryotic Pathogens

Redox homeostasis is an equilibrium between reducing and oxidizing reactions within cells. It is an essential, dynamic process, which allows proper cellular reactions and regulates biological responses. Unbalanced redox homeostasis is the hallmark of many diseases, including cancer or inflammatory responses, and can eventually lead to cell death. Specifically, disrupting redox balance, essentially by increasing pro-oxidative molecules and favouring hyperoxidation, is a smart strategy to eliminate cells and has been used for cancer treatment, for example. Selectivity between cancer and normal cells thus appears crucial to avoid toxicity as much as possible. Redox-based approaches are also employed in the case of infectious diseases to tackle the pathogens specifically, with limited impacts on host cells. In this review, we focus on recent advances in redox-based strategies to fight eukaryotic pathogens, especially fungi and eukaryotic parasites. We report molecules recently described for causing or being associated with compromising redox homeostasis in pathogens and discuss therapeutic possibilities.

New 4,5-Diarylimidazol-2-ylidene-iodidogold(I) Complexes with High Activity against Esophageal Adenocarcinoma Cells

Inspired by the vascular-disrupting agent combretastatin A-4 and recently published anticancer active N-heterocyclic carbene (NHC) complexes of Au(I), a series of new iodidogold(I)-NHC complexes was synthesized and characterized. The iodidogold(I) complexes were synthesized by a route involving van Leusen imidazole formation and N-alkylation, followed by complexation with Ag2O, transmetalation with chloro(dimethylsulfide)gold(I) [Au(DMS)Cl], and anion exchange with KI. The target complexes were characterized by IR spectroscopy, 1H and 13C NMR spectroscopy, and mass spectrometry. The structure of 6c was validated via single-crystal X-ray diffraction. A preliminary anticancer screening of the complexes using two esophageal adenocarcinoma cell lines showed promising nanomolar activities for certain iodidogold(I) complexes accompanied with apoptosis induction, as well as c-Myc and cyclin D1 suppression in esophageal adenocarcinoma cells treated with the most promising derivative 6b.

In vitro antifungal and antibiofilm activities of auranofin against itraconazole-resistant Aspergillus fumigatus

BACKGROUND

Infections caused by azole-resistant Aspergillus are a rising public health threat with high mortality rates, high treatment costs and limited available antifungals, indicating an urgent need for new antifungals or strategies. Our aim was to investigate antifungal and antibiofilm activities of auranofin, an FDA-approved anti-antirheumatic drug.

METHODS

Fungal susceptibility testing for auranofin was carried out by the broth-based microdilution methods. Cell viability treated by auranofin was tested by resazurin dye testing. The synergistic effect of auranofin and antifungal drugs was evaluated using checkboard assay. The inhibitory of biofilms were measured by crystal violet staining. Gene expression level analysis and enzyme activity was investigated with qRT-PCR analysis and DTNB assay. The key amino acid residues in the binding of auranofin with A. fumigatus thioredoxin reductase (AfTrxR) were indicated by structural analyses, site-directed mutagenesis, and microscale thermophoresis (MST) assays.

RESULTS

Auranofin has fungicidal activity and in vitro antifungal spectrum including Aspergillus flavus, Aspergillus fumigatus, Aspergillus terreus, Aspergillus niger, even itraconazole (ITC)-resistant A. fumigatus. Additionally, it has antibiofilm activities against ITC-resistant A. fumigatus by reducing the expression level of SomA and MedA. Moreover, we discovered a synergistic effect of auranofin and ITC or amphotericin B against ITC-resistant A. fumigatus. Auranofin downregulated the gene transcription of AfTrxR, and strongly inhibited the enzyme activity of AfTrxR through interacting with residues C145 and C148.

CONCLUSIONS

Auranofin has fungicidal and antibiofilm activities in Aspergillus spp. and is also a potentiator of ITC or amphotericin B in vitro.

Repurposing non-antifungal drugs auranofin and pentamidine in combination as fungistatic antifungal agents against C. albicans

Fungal infection is a serious global health issue, causing approximately 1.5 million mortalities annually. However, clinically available anti-fungal drugs are limited, especially for multidrug-resistant fungal infections. Therefore, new antifungal drugs are urgently needed to address this clinical challenge. In this study, we proposed two non-antifungal drugs, auranofin and pentamidine, in combination to fight against multidrug-resistant C. albicans. The insufficient antifungal activity of anti-rheumatic drug auranofin is partially due to fungal membrane barrier preventing the drug uptake, and anti-protozoal drug pentamidine was used here to improve the permeability of membrane. The auranofin/pentamidine combination displayed synergistic inhibitory effect against both drug-susceptible and drug-resistant C. albicans, as well as biofilm, and significantly reduced the minimum inhibitory concentration of each drug. At non-antifungal concentration, pentamidine can disrupt the membrane integrity and increase membrane permeability, leading to enhanced cellular uptake of auranofin in C. albicans. This repurposing strategy using the combination of non-antifungal drugs with complementary antifungal mechanism may provide a novel approach for discovery of antifungal drugs to fight against multidrug-resistant fungal infections.

Antifungal activity of vitamin D3 against Candida albicans in vitro and in vivo

The incidence of intra-abdominal candidiasis (IAC), characterized by high morbidity and mortality, has become a serious concern. The limitations of current antifungal drugs on the market underscores the importance of the development of novel antifungal agents. In the present study, the antifungal activity of vitamin D₃ (VD₃) against various Candida species was investigated. In vitro, the broth microdilution method and solid plate assay confirmed that VD₃ inhibited the growth of Candida spp. in a broad-spectrum, dose-dependent manner. VD₃ also had a significant antifungal effect on the initiation, development, and maturation phases of biofilm formation in Candida albicans. The mechanism of VD₃ action was explored by transcriptomics and reverse transcription quantitative PCR (RT-qPCR) analysis, and showed that VD₃ affects ribosome biogenesis, coenzyme metabolism, and carbon metabolism. These results suggested that VD₃ may have multitarget effects against C. albicans. In the murine IAC model, VD₃ reduced the fungal burden in the liver, kidneys, and small intestine. Further histopathological analysis and quantification of plasma cytokine levels confirmed that VD₃ treatment significantly decreased the infiltration of inflammatory cells and the levels of plasma interferon (IFN)-γ and tumor necrosis factor (TNF)-α. Taken together, these findings suggest a new antifungal mechanism for VD₃ and indicate that VD₃ could be an effective therapeutic agent for use in IAC treatment.

Development and research progress of anti-drug resistant fungal drugs

With the widespread use of immunosuppressive agents and the increase in patients with severe infections, the incidence of fungal infections worldwide has increased year by year. The fungal pathogens Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus cause a total of more than 1 million deaths each year. Long-term use of antifungal drugs can easily lead to fungal resistance, and the prevalence of drug-resistant fungi is a major global health challenge. In order to effectively control global fungal infections, there is an urgent need for new drugs that can exert effective antifungal activity and overcome drug resistance. We must promote the discovery of new antifungal targets and drugs, and find effective ways to control drug-resistant fungi through different ways, so as to reduce the threat of drug-resistant fungi to human life, health and safety. In the past few years, certain progress has been made in the research and development of antifungal drugs. In addition to summarizing some of the antifungal drugs currently approved by the FDA, this review also focuses on potential antifungal drugs, the repositioned drugs, and drugs that can treat drug-resistant bacteria and fungal infections, and provide new ideas for the development of antifungal drugs in the future.

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.

Discovery of spirooxindole-pyrrolidine heterocyclic hybrids with potent antifungal activity against fungal pathogens

Fungal pathogens mainly Candida and Cryptococcus species causes serious life-threating infections to humans, especially in individuals who are immunocompromised. Increasing frequency of antifungal drug resistance along with paucity of FDA-approved drugs suggest a dire need for new antifungal drugs. Our screening of newly synthesized spirooxindole heterocyclic hybrid compounds revealed that the novel small molecule, DPA-3, has potent antifungal activity without inducing mammalian cell cytotoxicity. Furthermore, DPA-3 significantly reduced hyphal and biofilm formation of Candida albicans ATCC 10231 strain, out-competing two FDA approved antifungal drugs. The results of our study conclude that DPA-3 is a compelling candidate for further development as an antifungal drug.

Gold Nanoclusters as Nanoantibiotic Auranofin Analogues

Auranofin, a gold(I)-complex with tetraacetylated thioglucose (Ac4 GlcSH) and triethylphosphine ligands, is an FDA-approved drug used as an anti-inflammatory aid in the treatment of rheumatoid arthritis. In repurposing auranofin for other diseases, it was found that the drug showed significant activity against Gram-positive but was inactive against Gram-negative bacteria. Herein, the design and synthesis of gold nanoclusters (AuNCs) based on the structural motif of auranofin are reported. Phosphine-capped AuNCs are synthesized and glycosylated, yielding auranofin analogues with mixed triphenylphosphine monosulfonate (TPPMS)/Ac4 GlcSH ligand shells. These AuNCs are active against both Gram-negative and Gram-positive bacteria, including multidrug-resistant pathogens. Notably, an auranofin analogue, a mixed-ligand 1.6 nm AuNC 4b, is more active than auranofin against Pseudomonas aeruginosa, while exhibiting lower toxicity against human A549 cells. The enhanced antibacterial activity of these AuNCs is characterized by a greater uptake of Au by the bacteria compared to AuI complexes. Additional factors include increased oxidative stress, moderate inhibition of thioredoxin reductase (TrxR), and DNA damage. Most intriguingly, the uptake of AuNCs are not affected by the bacterial outer membrane (OM) barrier or by binding with the extracellular proteins. This contrasts with AuI complexes like auranofin that are susceptible to protein binding and hindered by the OM barrier.

Anti-Staphylococcal Activity of the Auranofin Analogue Bearing Acetylcysteine in Place of the Thiosugar: An Experimental and Theoretical Investigation

Auranofin (AF, hereafter) is an orally administered chrysotherapeutic agent approved for the treatment of rheumatoid arthritis that is being repurposed for various indications including bacterial infections. Its likely mode of action involves the impairment of the TrxR system through the binding of the pharmacophoric cation [AuPEt₃]⁺. Accordingly, a reliable strategy to expand the medicinal profile of AF is the replacement of the thiosugar moiety with different ligands. Herein, we aimed to prepare the AF analogue bearing the acetylcysteine ligand (AF-AcCys, hereafter) and characterize its anti-staphylococcal activity. Biological studies revealed that AF-AcCys retains an antibacterial effect superimposable with that of AF against Staphylococcus aureus, whereas it is about 20 times less effective against Staphylococcus epidermidis. Bioinorganic studies confirmed that upon incubation with human serum albumin, AF-AcCys, similarly to AF, induced protein metalation through the [AuPEt₃]⁺ fragment. Additionally, AF-AcCys appeared capable of binding the dodecapeptide Ac-SGGDILQSGCUG-NH₂, corresponding to the tryptic C-terminal fragment (488–499) of hTrxR. To shed light on the pharmacological differences between AF and AF-AcCys, we carried out a comparative experimental stability study and a theoretical estimation of bond dissociation energies, unveiling the higher strength of the Au–S bond in AF-AcCys. From the results, it emerged that the lower lipophilicity of AF-AcCys with respect to AF could be a key feature for its different antibacterial activity. The differences and similarities between AF and AF-AcCys are discussed, alongside the opportunities and consequences that chemical structure modifications imply.

Anti-Staphylococcal Activity of the Auranofin Analogue Bearing Acetylcysteine in Place of the Thiosugar: An Experimental and Theoretical Investigation

Auranofin (AF, hereafter) is an orally administered chrysotherapeutic agent approved for the treatment of rheumatoid arthritis that is being repurposed for various indications including bacterial infections. Its likely mode of action involves the impairment of the TrxR system through the binding of the pharmacophoric cation [AuPEt₃]⁺. Accordingly, a reliable strategy to expand the medicinal profile of AF is the replacement of the thiosugar moiety with different ligands. Herein, we aimed to prepare the AF analogue bearing the acetylcysteine ligand (AF-AcCys, hereafter) and characterize its anti-staphylococcal activity. Biological studies revealed that AF-AcCys retains an antibacterial effect superimposable with that of AF against Staphylococcus aureus, whereas it is about 20 times less effective against Staphylococcus epidermidis. Bioinorganic studies confirmed that upon incubation with human serum albumin, AF-AcCys, similarly to AF, induced protein metalation through the [AuPEt₃]⁺ fragment. Additionally, AF-AcCys appeared capable of binding the dodecapeptide Ac-SGGDILQSGCUG-NH₂, corresponding to the tryptic C-terminal fragment (488-499) of hTrxR. To shed light on the pharmacological differences between AF and AF-AcCys, we carried out a comparative experimental stability study and a theoretical estimation of bond dissociation energies, unveiling the higher strength of the Au-S bond in AF-AcCys. From the results, it emerged that the lower lipophilicity of AF-AcCys with respect to AF could be a key feature for its different antibacterial activity. The differences and similarities between AF and AF-AcCys are discussed, alongside the opportunities and consequences that chemical structure modifications imply.

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.

Auranofin and its analogs as prospective agents for the treatment of colorectal cancer

Today colorectal cancer (CRC) is one of the leading causes of cancer death worldwide. This disease is poorly chemo-sensitive toward the existing medical treatments so that new and more effective therapeutic agents are urgently needed and intensely sought. Platinum drugs, oxaliplatin in particular, were reported to produce some significant benefit in CRC treatment, triggering the general interest of medicinal chemists and oncologists for metal-based compounds as candidate anti-CRC drugs. Within this frame, gold compounds and, specifically, the established antiarthritic drug auranofin with its analogs, form a novel group of promising anticancer agents. Owing to its innovative mechanism of action and its favorable pharmacological profile, auranofin together with its derivatives are proposed here as novel experimental agents for CRC treatment, capable of overcoming resistance to platinum drugs. Some encouraging results in this direction have already been obtained. A few recent studies demonstrate that the action of auranofin may be further potentiated through the preparation of suitable pharmaceutical formulations capable of protecting the gold pharmacophore from unselective reactivity or through the design of highly synergic drug combinations. The perspectives of the research in this field are outlined.

OUP accepted manuscript

Candida auris is an emerging, multi drug resistant fungal pathogen that has caused infectious outbreaks in over 45 countries since its first isolation over a decade ago, leading to in-hospital crude mortality rates as high as 72%. The fungus is also acclimated to disinfection procedures and persists for weeks in nosocomial ecosystems. Alarmingly, the outbreaks of C. auris infections in Coronavirus Disease-2019 (COVID-19) patients have also been reported. The pathogenicity, drug resistance and global spread of C. auris have led to an urgent exploration of novel, candidate antifungal agents for C. auris therapeutics. This narrative review codifies the emerging data on the following new/emerging antifungal compounds and strategies: antimicrobial peptides, combinational therapy, immunotherapy, metals and nano particles, natural compounds, and repurposed drugs. Encouragingly, a vast majority of these exhibit excellent anti- C. auris properties, with promising drugs now in the pipeline in various stages of development. Nevertheless, further research on the modes of action, toxicity, and the dosage of the new formulations are warranted. Studies are needed with representation from all five C. auris clades, so as to produce data of grater relevance, and broader significance and validity.

Target-based drug repurposing against Candida albicans-A computational modeling, docking, and molecular dynamic simulations study

The emergence of multidrug-resistant strains of Candida albicans has become a global threat mostly due to co-infection with immune-compromised patients leading to invasive candidiasis. The life-threatening form of the disease can be managed quickly and effectively by drug repurposing. Thus, the study used in silico approaches to evaluate Food and Drug Administration (FDA) approved drugs against three drug targets-TRR1, TOM40, and YHB1. The tertiary structures of three drug targets were modeled, refined, and evaluated for their structural integrity based on PROCHECK, ERRAT, and PROSA. High-throughput virtual screening of FDA-approved drugs (8815), interaction analysis, and energy profiles had revealed that DB01102 (Arbutamine), DB01611 (Hydroxychloroquine), and DB09319 (Carindacillin) exhibited better binding affinity with TRR1, TOM40, and YHB1, respectively. Notably, the molecular dynamic simulation explored that Gln45, Thr119, and Asp288 of TRR1; Thr107 and Ser121 of TOM40; Arg193, Glu213, and Ser228 of YHB1 are crucial residues for stable drug-target interaction. Additionally, it also prioritized Arbutamine-TRR1 as the best drug-target complex based on MM-PBSA (-52.72 kcal/mol), RMSD (2.43 Å), and radius of gyration (-21.49 Å) analysis. In-depth, PCA results supported the findings of molecular dynamic simulations. Interestingly, the conserved region (>70%) among the TRR1 sequences from pathogenic Candida species indicated the effectiveness of Arbutamine against multiple species of Candida as well. Thus, the study dispenses new insight and enriches the understanding of developing an advanced technique to consider potential antifungals against C. albicans. Nonetheless, a detailed experimental validation is needed to investigate the efficacy of Arbutamin against life-threatening candidiasis.

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.

Aprepitant, an antiemetic agent, interferes with metal ion homeostasis of Candida auris and displays potent synergistic interactions with azole drugs

With the rapid increase in the frequency of azole-resistant species, combination therapy appears to be a promising tool to augment the antifungal activity of azole drugs against resistant Candida species. Here, we report the effect of aprepitant, an antiemetic agent, on the antifungal activities of azole drugs against the multidrug-resistant Candida auris. Aprepitant reduced the minimum inhibitory concentration (MIC) of itraconazole in vitro, by up to eight-folds. Additionally, the aprepitant/itraconazole combination interfered significantly with the biofilm-forming ability of C. auris by 95 ± 0.13%, and significantly disrupted mature biofilms by 52 ± 0.83%, relative to the untreated control. In a Caenorhabditis elegans infection model, the aprepitant/itraconazole combination significantly prolonged the survival of infected nematodes by ~90% (five days post-infection) and reduced the fungal burden by ~92% relative to the untreated control. Further, this novel drug combination displayed broad-spectrum synergistic interactions against other medically important Candida species such as C. albicans, C. krusei, C. tropicalis, and C. parapsilosis (ƩFICI ranged from 0.08 to 0.31). Comparative transcriptomic profiling and mechanistic studies indicated aprepitant/itraconazole interferes significantly with metal ion homeostasis and compromises the ROS detoxification ability of C. auris. This study presents aprepitant as a novel, potent, and broad-spectrum azole chemosensitizing agent that warrants further investigation.

Encephalitozoon intestinalis: A new target for auranofin in a mice model

Despite the fact that many approaches have been developed over years to find efficient and well-tolerated therapeutic regimens for microsporidiosis, the effectiveness of current drugs remains doubtful, and effective drugs against specific targets are still scarce. The present study is the first that was designed to evaluate the potency of auranofin, an anti-rheumatoid FDA approved drug, against intestinal Encephalitozoon intestinalis. Evaluation of the drug was achieved through counting of fecal and intestinal spores, studying the intestinal histopathological changes, measuring of intestinal hydrogen peroxide level, and post therapy follow-up of mice for 2 weeks for detection of relapse. Results showed that auranofin has promising anti-microsporidia potential. It showed a promising efficacy in mice experimentally infected with E. intestinalis. It has revealed an obvious reduction in fecal spore shedding and intestinal tissue spore load, amelioration of intestinal tissue pathological changes, and improvement of the local inflammatory infiltration without significant changes in hydrogen peroxide level. Interestingly, auranofin prevented the relapse of infection. Thus, considering the results of the present work, auranofin could be considered a therapeutic alternative for the gold standard drug 'albendazole' against the intestinal E. intestinalis infection especially in relapsing cases.

Investigating auranofin for the treatment of infected diabetic pressure ulcers in mice and dermal toxicity in pigs

Bacterial infection of pressure ulcers (PUs) are a notable source of hospitalization for individuals with diabetes. This study evaluated the safety profile and efficacy of auranofin to treat diabetic PUs infected with methicillin-resistant Staphylococcus aureus (MRSA). PUs were infected with MRSA in diabetic TALLYHO/JngJ mice and then treated with topical auranofin (2%), topical mupirocin (2%), or oral clindamycin (30 mg/kg) for four days. PUs were harvested post-treatment to enumerate bacterial burden and determine expression of cytokines/growth factors. Landrace cross pigs were exposed topically to auranofin (1%, 2%, and 3%) for 4-14 days and evaluated for signs of localized or systemic toxicity. Auranofin eradicated MRSA in PUs within four days (7.92-log10 reduction) in contrast to mupirocin (2.15-log10 reduction) and clindamycin (0.73-log10 reduction). Additionally, auranofin treatment resulted in decreased expression of pro-inflammatory cytokines and increased expression of biomarkers associated with re-epithelization of wounded tissue, confirmed with histopathologic analysis. No significant histopathologic lesions were present on porcine skin sites exposed to topical auranofin. Additionally, minimal accumulation of plasma gold and no systemic toxicity was observed in pigs exposed to topical auranofin. Auranofin appears to be a potent and safe topical agent to further investigate for treatment of mild-to-moderate MRSA-infected diabetic PUs.

Repurposing of auranofin and honokiol as antifungals against Scedosporium species and the related fungus Lomentospora prolificans

The slowing-down de novo drug-discovery emphasized the importance of repurposing old drugs. This is particularly true when combating infections caused by therapy-refractory microorganisms, such as Scedosporium species and Lomentospora prolificans. Recent studies on Scedosporium responses to oxidative stress underscored the importance of targeting the underlying mechanisms. Auranofin, ebselen, PX-12, honokiol, and to a lesser extent, conoidin A are known to disturb redox-homeostasis systems in many organisms. Their antifungal activity was assessed against 27 isolates belonging to the major Scedosporium species: S. apiospermum, S. aurantiacum, S. boydii, S. dehoogii, S. minutisporum, and Lomentospora prolificans. Auranofin and honokiol were the most active against all Scedosporium species (mean MIC₅₀ values of 2.875 and 6.143 μg/ml, respectively) and against L. prolificans isolates (mean MIC₅₀ values of 4.0 and 3.563μg/ml respectively). Combinations of auranofin with voriconazole or honokiol revealed additive effects against 9/27 and 18/27 isolates, respectively. Synergistic interaction between auranofin and honokiol was only found against one isolate of L. prolificans. The effects of auranofin upon exposure to oxidative stress were also investigated. For all species except S. dehoogii, the maximal growth in the presence of auranofin significantly decreased when adding a sublethal dose of menadione. The analysis of the expression of genes encoding oxidoreductase enzymes upon exposure of S. apiospermum to honokiol unveiled the upregulation of many genes, especially those coding peroxiredoxins, thioredoxin reductases, and glutaredoxins. Altogether, these data suggest that auranofin and honokiol act via dampening the redox balance and support their repurposing as antifungals against Scedosporium species and L. prolificans.

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.

Combination Therapy to Treat Fungal Biofilm-Based Infections

An increasing number of people is affected by fungal biofilm-based infections, which are resistant to the majority of currently-used antifungal drugs. Such infections are often caused by species from the genera Candida, Aspergillus or Cryptococcus. Only a few antifungal drugs, including echinocandins and liposomal formulations of amphotericin B, are available to treat such biofilm-based fungal infections. This review discusses combination therapy as a novel antibiofilm strategy. More specifically, in vitro methods to discover new antibiofilm combinations will be discussed. Furthermore, an overview of the main modes of action of promising antibiofilm combination treatments will be provided as this knowledge may facilitate the optimization of existing antibiofilm combinations or the development of new ones with a similar mode of action.

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.

Recent Advances of Gold Compounds in Anticancer Immunity

In recent years, gold compounds have gained more and more attentions in the design of new metal anticancer drugs. Numerous researches have reported that gold compounds, in addition to their widely studied cytotoxic antitumor effects, also reverse tumor immune escape and directly facilitate the functions of immune cells, leading to enhanced anticancer effects. This review mainly summarizes our current understandings of antitumor effects of gold drugs and their relationships with various aspects of antitumor immunity, including innate immunity, adaptive immunity, immunogenic cell death, and immune checkpoints, as well as their roles in adverse effects. Some recent examples of anticancer gold compounds are highlighted. The property of gold compounds is expected to combine with anticancer immunotherapy, such as immune checkpoint inhibitors, to develop new anticancer therapeutic strategies.

Repurposing Fenamic Acid Drugs To Combat Multidrug-Resistant Neisseria gonorrhoeae

The rise of extensively drug-resistant and multidrug-resistant strains of Neisseria gonorrhoeae has occurred in parallel with the increasing demand for new drugs. However, the current methods of drug discovery are burdened with rigorous assessments and require more time than can be spared until gonococcal infections become difficult to control. To address this urgency, we utilized a drug-repurposing strategy and identified three clinically approved anthranilic acid drugs (tolfenamic acid, flufenamic acid, and meclofenamic acid) with potent antigonococcal activity, inhibiting 50% of the strains (MIC₅₀) from 4 to 16 μg/ml. Furthermore, tolfenamic acid showed indifferent activity with antibiotics of choice for gonococcal infections, azithromycin and ceftriaxone, in checkerboard assays with a fractional inhibitory concentration index ranging from 0.75 to 1.5. Fenamic acids reduced a high inoculum of N. gonorrhoeae below the limit of detection within 12 h and exhibited a low frequency of resistance. Interestingly, the fenamic acids did not inhibit the growth of commensal Lactobacillus spp. that comprise the healthy female genital microbiota. Fenamic acids were also superior to ceftriaxone in reducing the burden of intracellular N. gonorrhoeae within infected endocervical cells by 99%. Furthermore, all three fenamic acids significantly reduced the expression of proinflammatory cytokines by infected endocervical cells. Finally, fenamic acids and other structurally related anthranilic acid derivatives were evaluated to ascertain a more in-depth structure-activity relationship (SAR) that revealed N-phenylanthranilic acid as a novel antigonorrheal scaffold. This SAR study will pave the road to repositioning more potent fenamic acids analogues against N. gonorrhoeae.

Fungal Mitogenomes: Relevant Features to Planning Plant Disease Management

Mitochondrial genomes (mt-genomes) are characterized by a distinct codon usage and their autonomous replication. Mt-genomes encode highly conserved genes (mt-genes), like proteins involved in electron transport and oxidative phosphorylation but they also carry highly variable regions that are in part responsible for their high plasticity. The degree of conservation of their genes is such that they allow the establishment of phylogenetic relationships even across distantly related species. Here, we describe the mechanisms that generate changes along mt-genomes, which play key roles at enlarging the ability of fungi to adapt to changing environments. Within mt-genomes of fungal pathogens, there are dispensable as well as indispensable genes for survival, virulence and/or pathogenicity. We also describe the different complexes or mechanisms targeted by fungicides, thus addressing a relevant issue regarding disease management. Despite the controversial origin and evolution of fungal mt-genomes, the intrinsic mechanisms and molecular biology involved in their evolution will help to understand, at the molecular level, the strategies for fungal disease management.

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

Chromoblastomycosis (CBM) is a chronic subcutaneous mycosis caused by traumatic implantation of many species of black fungi. Due to the refractoriness of some cases and common recurrence of CBM, a more effective and less time-consuming treatment is mandatory. The aim of this study was to identify compounds with in vitro antifungal activity in the Pathogen Box® compound collection against different CBM agents. Synergism of these compounds with drugs currently used to treat CBM was also assessed. An initial screening of the drugs present in this collection at 1 μM was performed with a Fonsecaea pedrosoi clinical strain according to the EUCAST protocol. The compounds with activity against this fungus were also tested against other seven etiologic agents of CBM (Cladophialophora carrionii, Phialophora verrucosa, Exophiala jeanselmei, Exophiala dermatitidis, Fonsecaea monophora, Fonsecaea nubica, and Rhinocladiella similis) at concentrations ranging from 0.039 to 10 μM. The analysis of potential synergism of these compounds with itraconazole and terbinafine was performed by the checkerboard method. Eight compounds inhibited more than 60% of the F. pedrosoi growth: difenoconazole, bitertanol, iodoquinol, azoxystrobin, MMV688179, MMV021013, trifloxystrobin, and auranofin. Iodoquinol produced the lowest MIC values (1.25-2.5 μM) and MMV688179 showed MICs that were higher than all compounds tested (5 - >10 μM). When auranofin and itraconazole were tested in combination, a synergistic interaction (FICI = 0.37) was observed against the C. carrionii isolate. Toxicity analysis revealed that MMV021013 showed high selectivity indices (SI ≥ 10) against the fungi tested. In summary, auranofin, iodoquinol, and MMV021013 were identified as promising compounds to be tested in CBM models of infection.

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.

Auranofin, at clinically achievable dose, protects mice and prevents recurrence from Clostridioides difficile infection

Clostridioides difficile is the leading cause of nosocomial infections and a worldwide urgent public health threat. Without doubt, there is an urgent need for new effective anticlostridial agents due to the increasing incidence and severity of C. difficile infection (CDI). The aim of the present study is to investigate the in vivo efficacy of auranofin (rheumatoid arthritis FDA-approved drug) in a CDI mouse model and establish an adequate dosage for treatment. The effects of increased C. difficile inoculum, and pre-exposure to simulated gastric intestinal fluid (SGF) and simulated intestinal fluid (SIF), on the antibacterial activity of auranofin were investigated. Auranofin's in vitro antibacterial activity was stable in the presence of high bacterial inoculum size compared to vancomycin and fidaxomicin. Moreover, it maintained its anti-C. difficile activity after being exposed to SGF and SIF. Upon testing in a CDI mouse model, auranofin at low clinically achievable doses (0.125 mg/kg and 0.25 mg/kg) significantly protected mice against CDI with 100% and 80% survival, respectively. Most importantly, auranofin (0.125 mg/kg and 0.25 mg/kg) significantly prevented CDI recurrence when compared with vancomycin. Collectively, these results indicate that auranofin could potentially provide an effective, safe and quick supplement to the current approaches for treating CDI.

Dispiropyrrolidine tethered piperidone heterocyclic hybrids with broad-spectrum antifungal activity against Candida albicans and Cryptococcus neoformans

Invasive fungal infections along with rising incidence of resistance to antifungal drugs pose increasing threat to immunocompromised individuals, including cancer patients. In this study, we examined the antifungal activity of dispiropyrrolidine tethered piperidone heterocyclic hybrids. Results indicate that compounds 5a and 6i have demonstrated a potent antifungal effect on multiple fungal strains, including Candida albicans, without exhibiting cytotoxicity to mammalian cells. Furthermore, these two compounds exhibited significant inhibition on Candida albicans hyphae and biofilm development that surpasses the FDA-approved antifungal drug currently used for treatment. Taken together, our results suggest that 5a and 6i are promising candidates for development into new antifungal drugs.

Screening of Natural Products and Approved Oncology Drug Libraries for Activity against Clostridioides difficile

Clostridioides difficile is the most common cause of healthcare-associated diarrhea. Infection of the gastrointestinal tract with this Gram-positive, obligate anaerobe can lead to potentially life-threatening conditions in the antibiotic-treated populace. New therapeutics are urgently needed to treat this infection and prevent its recurrence. Here, we screened two libraries from the National Cancer Institute, namely, the natural product set III library (117 compounds) and the approved oncology drugs set V library (114 compounds), against C. difficile. In the two libraries screened, 17 compounds from the natural product set III library and 7 compounds from the approved oncology drugs set V library were found to exhibit anticlostridial activity. The most potent FDA-approved drugs (mitomycin C and mithramycin A) and a promising natural product (aureomycin) were further screened against 20 clinical isolates of C. difficile. The anticancer drugs, mitomycin C (MIC₅₀ = 0.25 μg/ml) and mithramycin A (MIC₅₀ = 0.015 μg/ml), and the naturally derived tetracycline derivative, aureomycin (MIC₅₀ = 0.06 μg/ml), exhibited potent activity against C. difficile strains. Mithramycin A and aureomycin were further found to inhibit toxin production by this pathogen. Given their efficacy, these compounds can provide a quick supplement to current treatment to address the unmet needs in treating C. difficile infection and preventing its recurrence.

Investigation of auranofin and gold-containing analogues antibacterial activity against multidrug-resistant Neisseria gonorrhoeae

Neisseria gonorrhoeae represents an urgent public health threat due to the rapid emergence of resistance to current antibiotics and the limited number of anti-gonococcal agents currently in clinical trials. This study utilized a drug repositioning strategy to investigate FDA-approved gold-containing drugs against N. gonorrhoeae. Auranofin, sodium aurothiomalate and aurothioglucose inhibited 48 clinical isolates of N. gonorrhoeae including multidrug-resistant strains at a concentration as low as 0.03 µg/mL. A time-kill assay revealed that auranofin exhibited rapid bactericidal activity against N. gonorrhoeae. Moreover, both sodium aurothiomalate and aurothioglucose did not inhibit growth of vaginal protective commensal lactobacilli. Auranofin, in combination with azithromycin, ceftriaxone, cefixime or tetracycline showed an additive effect against four N. gonorrhoeae strains, suggesting the possibility of using auranofin in dual therapy. Moreover, auranofin reduced the burden of intracellular N. gonorrhoeae by over 99% outperforming the drug of choice ceftriaxone. Auranofin was found superior to ceftriaxone in reducing the secretion of the pro-inflammatory cytokine IL-8 by endocervical cells infected with N. gonorrhoeae. Furthermore, auranofin exhibited a prolonged post-antibiotic effect over 10 h, as well as inability to generate resistant mutants. Overall, the current study suggests that repurposing gold-containing drugs, like auranofin, for treatment of gonorrhea warrants further investigation.

Identification of Off-Patent Drugs That Show Synergism with Amphotericin B or That Present Antifungal Action against Cryptococcus neoformans and Candida spp

Amphotericin B (AmB) is the antifungal with the strongest fungicidal activity, but its use has several limitations, mainly associated with its toxicity. Although some lipidic and liposomal formulations that present reduced toxicity are available, their price limits their application in developing countries. Flucytosine (5FC) has shown synergistic effect with AmB for treatment of some fungal infections, such as cryptococcosis, but again, its price is a limitation for its use in many regions. In the present work, we aimed to identify new drugs that have a minor effect on Cryptococcus neoformans, reducing its growth in the presence of subinhibitory concentrations of AmB. In the initial screening, we found fourteen drugs that had this pattern. Later, checkerboard assays of selected compounds, such as erythromycin, riluzole, nortriptyline, chenodiol, nisoldipine, promazine, chlorcyclizine, cloperastine, and glimepiride, were performed and all of them confirmed for their synergistic effect (fractional inhibitory concentration index [FICI] < 0.5). Additionally, toxicity of these drugs in combination with AmB was tested in mammalian cells and in zebrafish embryos. Harmless compounds, such as the antibiotic erythromycin, were found to have synergic activity with AmB, not only against C. neoformans but also against some Candida spp., in particular against Candida albicans In parallel, we identified drugs that had antifungal activity against C. neoformans and found 43 drugs that completely inhibited the growth of this fungus, such as ciclopirox and auranofin. Our results expand our knowledge about antifungal compounds and open new perspectives in the treatment of invasive mycosis based on repurposing off-patent drugs.

Whole-Genome Approach to Understanding the Mechanism of Action of a Histatin 5-Derived Peptide

The incidence of opportunistic fungal infections that threaten immunocompromised patients, along with the limited arsenal of antifungal drugs, calls for renewed efforts to develop novel antifungal therapies. Antimicrobial peptides have garnered interest as potential therapeutics. Among naturally occurring peptides, histatin 5 is a well-characterized 24-amino-acid peptide with strong antifungal activity. Our lab has identified a smaller histatin derivative, KM29, with stronger activity against multiple Candida spp., prompting us to investigate its fungicidal mechanism. A genetic screen was developed to test the Saccharomyces cerevisiae genomewide deletion collection for mutants with increased or decreased peptide sensitivity. The goal was to identify genes that would reveal insights into the mechanism of action of KM29, to be assessed in Candida albicans Several biological processes yielded increased sensitivity, with endosomal transport and vacuolar function appearing at high frequencies. Among the pathways involved in increased resistance, mitochondrial function showed the highest normalized genome frequency; hence, we focused on characterizing this pathway. KM29 localizes to mitochondria, and the killing activity depends on a functional electron transport chain. In addition, KM29 triggered reactive oxygen species (ROS) production, which was responsible for some cell death but insufficient to account for the complete killing activity. In agreement with this finding, we found that KM29 induced mitochondrial fragmentation and a mild loss of mitochondrial membrane potential. Furthermore, respiratory mutants exhibited severely diminished KM29 uptake. We confirmed this behavior in a C. albicans respiratory mutant. Taking our findings together, this work delineates the mitochondrial functions associated with KM29 fungicidal activity and provides additional pathways for further characterization in Candida spp.

Thioredoxin Reductase 1 Is a Highly Immunogenic Cell Surface Antigen in Paracoccidioides spp., Candida albicans, and Cryptococcus neoformans

The increasing number of immunocompromised people has made invasive fungal infections more common. The antifungal armamentarium, in contrast, is limited to a few classes of drugs, with frequent toxicity and low efficacy pointing to the need for new agents. Antibodies are great candidates for novel antifungals, as their specificity can result in lower toxicity. Additionally, the immunomodulatory activity of antibodies could treat the underlying cause of many invasive mycoses, immune disfunction. In a previous comparative genomics study, we identified several potential targets for novel antifungals. Here we validate one of these targets, thioredoxin reductase (TRR1), to produce antibodies that could be useful therapeutic tools. Recombinant TRR1 proteins were produced by heterologous expression in Escherichia coli of genes encoding the proteins from Candida albicans, Cryptococcus neoformans, and Paracoccidioides lutzii. These proteins were then used to immunize mice, followed by detection of serum antibodies against them by ELISA and western blot. A first set of experiments in which individual mice were immunized repeatedly with TRR1 from a single species showed that all three were highly immunogenic, inducing mostly IgG1 antibodies, and that antibodies produced against one species cross-reacted with the others. In a second experiment, individual mice were immunized three times, each with the protein from a different species. The high titers of antibodies confirmed the presence of antigenic epitopes that were conserved in fungi but absent in humans. Immunofluorescence with sera from these immunized mice detected the protein in the cytoplasm and on the cell surface of fungi from all three species. These results validate TRR1 as a good target for potentially broad-spectrum antifungal antibodies.

Identification of a Phenylthiazole Small Molecule with Dual Antifungal and Antibiofilm Activity Against Candida albicans and Candida auris

Candida species are a leading source of healthcare infections globally. The limited number of antifungal drugs combined with the isolation of Candida species, namely C. albicans and C. auris, exhibiting resistance to current antifungals necessitates the development of new therapeutics. The present study tested 85 synthetic phenylthiazole small molecules for antifungal activity against drug-resistant C. albicans. Compound 1 emerged as the most potent molecule, inhibiting growth of C. albicans and C. auris strains at concentrations ranging from 0.25–2 µg/mL. Additionally, compound 1 inhibited growth of other clinically-relevant yeast (Cryptococcus) and molds (Aspergillus) at a concentration as low as 0.50 µg/mL. Compound 1 exhibited rapid fungicidal activity, reducing the burden of C. albicans and C. auris below the limit of detection within 30 minutes. Compound 1 exhibited potent antibiofilm activity, similar to amphotericin B, reducing the metabolic activity of adherent C. albicans and C. auris biofilms by more than 66% and 50%, respectively. Furthermore, compound 1 prolonged survival of Caenorhabditis elegans infected with strains of C. albicans and C. auris, relative to the untreated control. The present study highlights phenylthiazole small molecules, such as compound 1, warrant further investigation as novel antifungal agents for drug-resistant Candida infections.

Repurposing salicylamide for combating multidrug-resistant Neisseria gonorrhoeae

The U.S. Centers for Disease Control and Prevention (CDC) lists Neisseria gonorrhoeae as one of the most urgent antibiotic-resistant threats in the United States. This is due to the emergence of clinical isolates that have developed resistance to nearly every antibiotic used to treat gonorrhea and highlights the critical need to find new therapeutics. The present study discovered salicylamide, an analgesic and antipyretic drug, has antibacterial activity against 40 different antibiotic-resistant strains of N. gonorrhoeae (MIC 8-32 μg/ml) with low frequency of resistance <2.4x10^-9 Interestingly, salicylamide did not inhibit growth of bacterial species in the vaginal microflora involved in defense against gonococcal infections, such as Lactobacillus gasseri, L. jensenii, L. johnsonii, and L. crispatus A time-kill assay revealed that salicylamide is a rapidly bactericidal drug as it eradicated a high inoculum of N. gonorrhoeae within 10 hours. Salicylamide was superior to the drug of choice, ceftriaxone, in reducing the burden of intracellular N. gonorrhoeae by 97% in infected endocervical cells. Furthermore, salicylamide outperformed ceftriaxone in reducing expression of the pro-inflammatory cytokine IL-8 from endocervical cells infected with N. gonorrhoeae A checkerboard assay revealed that salicylamide exhibited a synergistic interaction with tetracycline and an additive relationship with azithromycin and ciprofloxacin, and ceftriaxone. A more in-depth investigation of the structure-activity-relationship of derivatives of salicylamide revealed the amide and hydroxyl groups are important for anti-gonorrheal activity. In conclusion, this study identified salicylamide as a promising candidate for further investigation as a novel treatment option for multidrug-resistant gonorrhea.

Organogold drug Auranofin exhibits anti-melanogenic activity in B16F10 and MNT-1 melanoma cells

Auranofin (AF) is an organogold FDA-approved drug for treating rheumatism and has been repurposed for several pharmacological applications based on its anti-bacterial, anti-fungal and anti-inflammatory activities. To the best of our knowledge, there has been no study on effects of AF on melanogenesis yet. Hence, in this work, we studied the effect of AF on melanogenesis using B16F10 mouse melanoma cells and validated results in MNT-1 human melanoma cells. Melanogenesis assay was conducted with concentrations of AF determined to be nontoxic in B16F10 cells as well as HaCaT human epidermal cell line for a duration of 48 h, followed by various assays to delineate mechanisms of melanogenesis inhibition. Ultrastructural analysis was conducted to study further if AF affected melanosome maturation and protein levels of a key melanogenic protein, tyrosinase, and the maturation signaling molecule, cyclic adenosine monophosphate (cAMP), was estimated. Our results demonstrate that AF at nontoxic concentrations of 0.25-1 µM significantly inhibited melanin synthesis in a dose-dependent manner with significant inhibition of 32.85% at 1 µM. The study of mechanisms of melanogenesis inhibition revealed that AF inhibited tyrosinase activity in lysates of B16F10 cells but did not show a direct effect on purified mushroom tyrosinase activity or on copper chelation in a cell-free system, nor did it affect levels of B16F10 tyrosinase protein levels. However, AF significantly down-regulated cAMP levels, inhibited cellular ROS and increased number of melanosomes in immature stages, and also exhibited anti-melanogenic activity in B16F10-HaCaT cocultures. Furthermore, AF showed anti-melanogenic efficacy in MNT-1 cell monocultures and cocultures with an inhibition of intracellular tyrosinase activity. In summary, our results demonstrate a proof-of-principle for AF as a depigmenting agent for hyperpigmentation disorders and adjuvant for melanoma therapeutics.

Potential impact of the antirheumatic agent auranofin on proviral HIV-1 DNA in individuals under intensified antiretroviral therapy: Results from a randomised clinical trial

Antiretroviral therapy (ART) is typically composed of a combination of three antiretroviral drugs and is the treatment of choice for people with human immunodeficiency virus type 1/acquired immune deficiency syndrome (HIV-1/AIDS). However, it is unable to impact on viral reservoirs, which harbour latent HIV-1 genomes that are able to reignite the infection upon treatment suspension. The aim of this study was to provide an estimate of the safety of the disease-modifying antirheumatic agent auranofin and its impact on the HIV-1 reservoir in humans under intensified ART. For this purpose, an interim analysis was conducted of three of the six arms of the NCT02961829 clinical trial (five patients each) with: no intervention, i.e. continuation of first-line ART; intensified ART (ART + dolutegravir and maraviroc); and intensified ART plus auranofin. Auranofin treatment was found to be well tolerated. No major adverse events were detected apart from a transient decrease in CD4⁺ T-cell counts at Weeks 8 and 12. Auranofin decreased total viral DNA in peripheral blood mononuclear cells compared with ART-only regimens at Week 20 (P = 0.036) and induced a decrease in integrated viral DNA as quantified by Alu PCR. Despite the limited number of patient-derived sequences available in this study, phylogenetic analyses of nef sequences support the idea that auranofin may impact on the viral reservoir. [ClinicalTrials.gov ID: NCT02961829].