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Abstract
Triazoles have demonstrated significant efficacy in the treatment of fungal infections. However, increasing drug resistance is a growing concern that negatively impacts their effectiveness. By designing a well-crafted side chain, triazoles can be endowed with advantages, like higher potency and the ability to overcome drug resistance. This highlights the diverse interactions between side chains and CYP51. To explore novel triazole antifungal agents, we synthesized three series of fluconazole-core compounds and focused on optimizing the chain based on molecule docking and in vitro results. The most potent S-F24 exhibited excellent broad-spectrum antifungal activity that was better or comparable to clinically used azoles. S-F24 maintained its potency even against multi-resistant Candida albicans. Additionally, S-F24 displayed a good safety profile with high selectivity, low hemolytic effects, and low tendency to induce resistance. Our findings collectively demonstrated that there was still a high potential for side-chain modification in the development of novel azoles.
... The inclusion of cyclic amine linkers into a hybrid structure with a triazole pharmacophore is widely used in the exploratory work of researchers in medical chemistry [15]. A number of compounds recently obtained by Zhu Figure 3) demonstrated high antifungal activity not only in vitro, but also on animals with disseminated Candida infection [16]. The activity of the molecules largely depended on the substituent adjacent to the carbonyl group of the piperazine amide ( Figure 3). ...
... The inclusion of cyclic amine linkers into a hybrid structure with a triazole pharmacophore is widely used in the exploratory work of researchers in medical chemistry [15]. A number of compounds recently obtained by Zhu et al. (IX, Xa,b, Figure 3) demonstrated high antifungal activity not only in vitro, but also on animals with disseminated Candida infection [16]. The activity of the molecules largely depended on the substituent adjacent to the carbonyl group of the piperazine amide ( Figure 3). ...
... The structures of key compounds 31a (L-173) 20-23 and L-310 16 Figure S15), performed at the natural abundance of the 13 C isotope. Analysis of these 2D spectra allowed us to completely assign the 1 H and 13 C signals of the compounds L-173 and L-310 (Table 2) and to confirm their structure. ...
A series of hybrid compounds with triazole and thiazolidine nuclei connected by a linker has been synthesized and extensively studied. Various synthetic methods for the target compounds have been tested. A microbiological assessment of the obtained compounds was carried out on strains of pathogenic fungi C. albicans, C. non-albicans, multidrug-resistant C. auris, Rhizopus arrhizus, Aspergillus spp. and some dermatophytes and other yeasts. The lowest obtained MIC values for target compounds lie between 0.003 µg/mL and 0.5 µg/mL and therefore the compounds are not inferior or several times better than commercial azole drugs. The length of the acylpiperazine linker has a limited effect on antifungal activity. Some bioisosteric analogues were tested in microbiological analysis, but turned out to be weaker than the leader in activity. The highest activity was demonstrated by a compound with para-chlorobenzylidene substituent in the thiazolidine fragment. Molecular modelling was used to predict binding modes of synthesized molecules and rationalize experimentally observed SAR. The leader compound is twice more effective in inhibiting the formation of germ tubes by Candida albicans yeast cells compared to voriconazole. An increased level of Pdr5, an azoles drug efflux pump was observed, but the increase is lower than that caused by azoles. The results can be useful for further development of more powerful and safe antifungal agents.
... For the triazole group of 2d, in turn, three hydrogen bonds were predicted between its amino group at the N4 position and the carbonyl group of Tyr-505, the N2 nitrogen atom and the carbonyl group of Pro-375, as well as between the N1 nitrogen atom and the amino group of conserved residue (His-377) in all CYP51 enzymes from the Candida genera 36 , In contrast to long-tailed native inhibitor VT1161, neither coordination bond with the prosthetic heme iron through the triazole ring of 2d nor its close contacts with the heme-binding core region were recorded. Additionally, no close interactions of 2d with Tyr-132, recognized as a crucial residue to the antifungal ability 38 were observed. Thus, we can conclude that although short-tailed 2d can inhibit CYP51 activity by competing with the sterol substrate for the space within the enzyme-active site, it cannot affect the iron potential to be reduced 36 . ...
Nowadays, dermatophyte infections are relatively easy to cure, especially since the introduction of orally administered antifungals such as terbinafine and itraconazole. However, these drugs may cause side effects due to liver damage or their interactions with other therapeutics. Hence, the search for new effective chemotherapeutics showing antidermatophyte activity seems to be the urge of the moment. Potassium salts of N-acylhydrazinecarbodithioates are used commonly as precursors for the synthesis of biologically active compounds. Keeping that in mind, the activity of a series of five potassium N-acylhydrazinecarbodithioates (1a–e) and their aminotriazole-thione derivatives (2a–e) was evaluated against a set of pathogenic, keratinolytic fungi, such as Trichophyton ssp., Microsporum ssp. and Chrysosporium keratinophilum, but also against some Gram-positive and Gram-negative bacteria. All tested compounds were found non-toxic for L-929 and HeLa cells, with the IC30 and IC50 values assessed in the MTT assay above 128 mg/L. The compound 5-amino-3-(naphtalene-1-yl)-4,5-dihydro-1H-1,2,4-triazole-5-thione (2d) was found active against all fungal strains tested. Scanning Electron Microscopy (SEM) revealed inhibition of mycelium development of Trichophyton rubrum cultivated on nail fragments and treated with 2d 24 h after infection with fungal spores. Transmission Electron Microscopy (TEM) observation of mycelium treated with 2d showed ultrastructural changes in the morphology of germinated spores. Finally, the RNA-seq analysis indicated that a broad spectrum of genes responded to stress induced by the 2d compound. In conclusion, the results confirm the potential of N-acylhydrazinecarbodithioate derivatives for future use as promising leads for new antidermatophyte agents development.
Invasive fungal infections, with their high morbidity and mortality, have become one of the most serious threats to human health. There are a few kinds of clinical antifungal drugs but...
Luliconazole is a new topical imidazole antifungal drug for the treatment of skin infections. It has low solubility and poor skin penetration which limits its therapeutic applications. In order to improve its therapeutic efficacy, spanlastics nanoformulation was developed and optimized using a combined mixture-process variable design (CMPV). The optimized formulation was converted into a hydrogel formula to enhance skin penetration and increase the efficacy in experimental cutaneous Candida albicans infections in Swiss mice wounds. The optimized formulation was generated at percentages of Span and Tween of 48% and 52%, respectively, and a sonication time of 6.6 min. The software predicted that the proposed formulation would achieve a particle size of 50 nm with a desirability of 0.997. The entrapment of luliconazole within the spanlastics carrier showed significant (p < 0.0001) antifungal efficacy in the immunocompromised Candida-infected Swiss mice without causing any irritation, when compared to the luliconazole treated groups. The microscopic observation showed almost complete removal of the fungal colonies on the skin of the infected animals (0.2 ± 0.05 log CFU), whereas the control animals had 0.2 ± 0.05 log CFU. Therefore, luliconazole spanlastics could be an effective formulation with improved topical delivery for antifungal activity against C. albicans.
Metal nanoparticles used as antifungals have increased the occurrence of fungal-metal interactions. However, there is a lack of knowledge about how these interactions cause genomic and physiological changes, which can produce fungal superbugs. Despite interest in these interactions, there is limited understanding of resistance mechanisms in most fungi studied until now. We highlight the current knowledge of fungal homeostasis of zinc, copper, iron, manganese, and silver to comprehensively examine associated mechanisms of resistance. Such mechanisms have been widely studied in Saccharomyces cerevisiae, but limited reports exist in filamentous fungi, though they are frequently the subject of nanoparticle biosynthesis and targets of antifungal metals. In most cases, microarray analyses uncovered resistance mechanisms as a response to metal exposure. In yeast, metal resistance is mainly due to the down-regulation of metal ion importers, utilization of metal-lothionein and metallothionein-like structures, and ion sequestration to the vacuole. In contrast, metal resistance in filamentous fungi heavily relies upon cellular ion export. However, there are instances of resistance that utilized vacuole sequestration, ion metallothionein, and chelator binding , deleting a metal ion importer, and ion storage in hyphal cell walls. In general, resistance to zinc, copper, iron, and manganese is extensively reported in yeast and partially known in filamentous fungi; and silver resistance lacks comprehensive understanding in both.
Background
Candida auris is a new pathogen called “superbug fungus” which caused panic worldwide. There are no large-scale epidemiology studies by now, therefore a systematic review and meta-analysis was undertaken to determine the epidemic situation, drug resistance patterns and mortality of C. auris.
Methods
We systematically searched studies on the clinical report of Candida auris in Pubmed, Embase and Cochrane databases until October 6, 2019. A standardized form was used for data collection, and then statics was performed with STATA11.0.
Results
It showed that more than 4733 cases of C. auris were reported in over 33 countries, with more cases in South Africa, United States of America, India, Spain, United Kingdom, South Korea, Colombia and Pakistan. C. auirs exhibited a decrease in case count after 2016. Clade I and III were the most prevalent clades with more cases reported and wider geographical distribution. Blood stream infection was observed in 32% of the cases, which varied depending on the clades. Resistance to fluconazole, amphotericin B, caspofungin, micafungin and anidulafungin in C. auris were 91, 12, 12.1, 0.8 and 1.1%. The overall mortality of C. auris infection was 39%. Furthermore, subgroup analyses showed that mortality was higher in bloodstream infections (45%), and lower in Europe (20%).
Conclusions
Over 4000 cases of C. auris were reported in at least 33 countries, which showed high resistance to fluconazole, moderate resistance to amphotericin B and caspofungin, high sensitivity to micafungin and anidulafungin. The crude mortality for BSI of C. auris was 45% which was similar to some drug-resistant bacteria previously reported. In conclusion, C. auris displayed similar characteristics to some drug resistance organisms. This study depicts several issues of C. auris that are most concerned, and is of great significance for the clinical management.
Bacterial or virus co-infections with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been reported in many studies, however, the knowledge on Aspergillus co-infection among patients with coronavirus disease 2019 (COVID-19) was limited. This literature review aims to explore and describe the updated information about COVID-19 associated with pulmonary aspergillosis. We found that Aspergillus spp. can cause co-infections in patients with COVID-19, especially in severe/critical illness. The incidence of IPA in COVID-19 ranged from 19.6% to 33.3%. Acute respiratory distress syndrome requiring mechanical ventilation was the common complications, and the overall mortality was high, which could be up to 64.7% (n = 22) in the pooled analysis of 34 reported cases. The conventional risk factors of invasive aspergillosis were not common among these specific populations. Fungus culture and galactomannan test, especially from respiratory specimens could help early diagnosis. Aspergillus fumigatus was the most common species causing co-infection in COVID-19 patients, followed by Aspergillus flavus. Although voriconazole is the recommended anti-Aspergillus agent and also the most commonly used antifungal agent, aspergillosis caused by azole-resistant Aspergillus is also possible. Additionally, voriconazole should be used carefully in the concern of complicated drug–drug interaction and enhancing cardiovascular toxicity on anti-SARS-CoV-2 agents. Finally, this review suggests that clinicians should keep alerting the possible occurrence of pulmonary aspergillosis in severe/critical COVID-19 patients, and aggressively microbiologic study in addition to SARS-CoV-2 via respiratory specimens should be indicated.
With some advances in modern medicine (such as cancer chemotherapy, broad exposure to antibiotics, and immunosuppression) the incidence of opportunistic fungal pathogens such as Candida albicans has increased. Cases of drug resistance among these pathogens have become more frequent, requiring the development of new drugs and a better understanding of the targeted enzymes. Sterol 14α-demethylase (CYP51) is a cytochrome P450 enzyme required for biosynthesis of sterols in eukaryotic cells and the major target of clinical drugs for managing fungal pathogens, but some of the CYP51 key features important for rational drug design have remained obscure. We report the catalytic properties, ligand-binding profiles, and inhibition of enzymatic activity of C. albicans CYP51 by clinical antifungal drugs that are used systemically (fluconazole, voriconazole, ketoconazole, itraconazole, and posaconazole) and topically (miconazole and clotrimazole) and by a tetrazole-based drug candidate, VT-1161 (oteseconazole; (R)-2- (2,4-difluorophenyl)-1,1-difluoro-3-(1H-tetrazol-1- yl)-1-(5-(4-(2,2,2-trifluoroethoxy) phenyl)pyridin-2- yl)propan-2-ol). Among the compounds tested, the first-line drug fluconazole was the weakest inhibitor, while posaconazole and VT-1161 were the strongest CYP51 inhibitors. We determined the X-ray structures of C. albicans CYP51 complexes with posaconazole and VT-1161, providing a molecular mechanism for the potencies of these drugs, including the activity of VT-1161 against C. krusei and C. glabrata, pathogens that are intrinsically resistant to fluconazole. Our comparative structural analysis outlines phylum-specific CYP51 features that could direct future rational development of more efficient broad-spectrum antifungals.
Invasive fungal infections and systemic mycosis, whether from nosocomial infection or immunodeficiency, have been on an upward trend for numerous years. Despite advancements in antifungal medication treatment in certain patients can still be difficult for reasons such as impaired organ function, limited administration routes or poor safety profiles of the available antifungal medications. The growing number of invasive fungal species becoming resistant to current antifungal medications is of appreciable concern. Triazole compounds containing one or more 1,2,4-triazole rings have been shown to contain some of the most potent antifungal properties. Itraconazole and fluconazole were some of the first triazoles synthesized, but had limitations associated with their use. Second-generation triazoles such as voriconazole, posa- conazole, albaconazole, efinaconazole, ravuconazole and isavuconazole are all derivatives of either itraconazole or fluconazole, and designed to overcome the deficiencies of their parent drugs. The goal of this manuscript is to review antifungal agents derived from triazole. Copyright © 2015 Prous Science, S.A.U. or its licensors. All rights reserved.
Aspergillus fumigatus is the opportunistic fungal pathogen that predominantly affects the immunocompromised population and causes 600,000 deaths per year. The cytochrome P450 (CYP) 51 inhibitor voriconazole is currently the drug of choice, yet the treatment efficiency remains low, calling for rational development of more efficient agents. A. fumigatus has two CYP51 genes, CYP51A and CYP51B, which share 59% amino acid sequence identity. CYP51B is expressed constitutively, while gene CYP51A is reported to be inducible. We expressed, purified, and characterized A. fumigatus CYP51B, including determination of its substrate preferences, catalytic parameters, inhibition, and X-ray structure in complexes with voriconazole and the experimental inhibitor (R)-N-(1-(2,4-dichlorophenyl)-2-(1H-imidazol-1-yl)ethyl)-4-(5-phenyl-1,3,4-oxadiazol-2-yl)benzamide (VNI). The enzyme demethylated its natural substrate eburicol and the plant CYP51 substrate obtusifoliol at steady-state rates of 17 and 16 min-1, respectively, but did not metabolize lanosterol, and the topical antifungal drug miconazole was the strongest inhibitor that we identified. The X-ray crystal structures displayed high overall similarity of A. fumigatus CYP51B to CYP51 orthologs from other biological kingdoms but revealed phylum-specific differences relevant to enzyme catalysis and inhibition. The complex with voriconazole provides an explanation for the potency of this relatively small molecule, while the complex with VNI outlines a direction for further enhancement of the efficiency of this new inhibitory scaffold to treat humans afflicted with filamentous fungal infections.
Copyright © 2015, The American Society for Biochemistry and Molecular Biology.
Design and synthesis of triazole library antifungal agents having piperazine side chains, analogues to fluconazole were documented. The synthesis highlighted utilization of the click chemistry on the basis of the active site of the cytochrome P450 14α-demethylase (CYP51). Their structures were characterized by 1H-NMR, 13C-NMR, MS and IR. The influences of piperazine moiety on in vitro antifungal activities of all the target compounds were evaluated against eight human pathogenic fungi.
Azole antimycotics are a well-known and important class of agents that are used in hospital practice, everyday health care, veterinary medicine and for crop protection. The era of azole fungicides began with the breakthrough of chlormidazole roughly 50 years ago. Since then, more than 20 drugs of this group, including triazoles, have been brought to the market. The specific chemical structure and mechanism of the action of azoles along with the eukaryotic character of fungal pathogens raise several serious issues. Resistance to drugs and disturbance to metabolic pathways are among the most important. On the other hand, these same features are responsible for unique and novel applications of these drugs. As a result, old and ineffective antifungal drugs can be successfully used in the treatment of parasitic diseases, bacterial infections or cancers. Are azoles getting their second wind?
Drug-drug interactions are a recurring problem in immunocompromised patients treated with triazole antifungals. While the introduction of new antifungals has expanded opportunities for lowering drug toxicity, virtually all antifungal regimens carry the risk of pharmacokinetic and pharmacodynamic interaction. This review presents the published data on molecular determinants (enzymes, transporters, orphan nuclear receptors) of systemic triazole pharmacokinetics in humans, including itraconazole, fluconazole, voriconazole and posaconazole. Systemic triazoles are inhibitors of cytochrome P450 (CYP) isozymes, such as CYP3A4, CYP2C9 and CYP2C19, to varying degrees. In addition, some are substrates and/or inhibitors of drug transporters such as multidrug resistance-1 gene product, P-glycoprotein, or breast cancer resistance protein. The interactions of triazole antifungals can be divided into the following categories: modifications of antifungal pharmacokinetics by other drugs, modifications of other drug pharmacokinetics by antifungals, and two-way interactions. These features are the basis of most interactions that occur during triazole therapy.
A reconstituted monooxygenase system containing a form of cytochrome P-450, termed P-450(14)DM, and NADPH-cytochrome P-450 reductase, both purified from yeast microsomes, catalyzed the conversion of lanosterol (4,4,14 alpha-trimethyl-5 alpha-cholesta-8,24-dien-3 beta-01) to a sterol metabolite in the presence of NADPH and molecular oxygen. This conversion did not occur anaerobically or when either P-450(14)DM, the reductase, or NADPH was omitted from the system. In both free and trimethylsilylated forms, this metabolite showed a relative retention time (relative to lanosterol) of 1.10 in gas chromatography on OV-17 columns. Comparison of its mass spectrum and retention time with those of lanosterol and 4,4-dimethylzymosterol (4,4-dimethyl-5 alpha-cholesta-8,24-dien-3 beta-ol) indicated that the metabolite was 4,4-dimethyl-5 alpha-cholesta-8,14,24-trien-3 beta-ol. Upon aerobic incubation of microsomes from semianaerobically grown yeast cells in the presence of NADPH and cyanide, endogenous lanosterol was converted to 4,4-dimethylzymosterol. This metabolism was inhibited by CO, metyrapone, SKF-525A, and antibodies to P-450(14)DM. It is concluded that in yeast microsomes lanosterol is 14 alpha-demethylated by a P-450(14)DM-containing monooxygenase system to give rise to 4,4-dimethyl-5 alpha-cholesta-8,14,24-trien-3 beta-ol, which is then reduced to 4,4-dimethylzymosterol by an NADPH-linked reductase.
In our continuing efforts to discover novel triazoles with improved antifungal activity in vitro and in vivo, a series of 41 novel compounds containing 1,2,3-triazole side chains were designed and synthesized via a click reaction based on our previous work. Most of the compounds showed moderate to excellent broad-spectrum antifungal activity in vitro. Among them, the most promising compound 9A16 displayed excellent antifungal and anti-drug-resistant fungal ability (MIC80 = 0.0156-8 μg/mL). In addition, compound 9A16 showed powerful in vivo efficacy on mice systematically infected with Candida albicans SC5314, Cryptococcus neoformans H99, fluconazole-resistant C. albicans 100, and Aspergillus fumigatus 7544. Moreover, compared to fluconazole, compound 9A16 showed better in vitro anti-biofilm activity and was more difficult to induce drug resistance in a 1 month induction of resistance assay in C. albicans. With favorable pharmacokinetics, an acceptable safety profile, and high potency in vitro and in vivo, compound 9A16 is currently under preclinical investigation.
What is known and objective:
Posaconazole is the second-generation triazole antifungal agent with widespread clinical application. Posaconazole exposure is influenced by various factors such as drug interactions, disease state and diet, resulting in a high interindividual variability in many patients and failure to ensure therapeutic efficacy. Therefore, it is necessary to conduct individualized therapy on posaconazole to ensure the efficacy and safety of treatment.
Methods:
Articles were identified through PubMed using the keywords such as "posaconazole," "therapeutic drug monitoring" and "Population pharmacokinetics" from 1 January 2001 to 30 April 2022.
Results and discussion:
In this paper, we review the individualized treatment studies of posaconazole from the three aspects of therapeutic drug monitoring, population pharmacokinetic study and Monte Carlo simulation to provide reference for in-depth individualized posaconazole dosing studies.
What is new and conclusion:
This review suggests that therapeutic drug monitoring should be performed in patients taking posaconazole to adjust the dosage and assess the efficacy and cost-effectiveness of posaconazole under different clinical conditions and different dosing regimens through Monte Carlo simulations. In the future, a more detailed delineation and comprehensive examination of posaconazole PPK for specific populations requires further study.
With the increase of fungal infection and drug resistance, it is becoming an urgent task to discover the highly effective antifungal drugs. In the study, we selected the key ergosterol bio-synthetic enzymes (Squalene epoxidase, SE; 14 α-demethylase, CYP51) as dual-target receptors to guide the construction of novel antifungal compounds, which could achieve the purpose of improving drug efficacy and reducing drug-resistance. Three different series of amide naphthyl compounds were generated through the method of skeleton growth, and their corresponding target products were synthesized. Most of compounds displayed the obvious biological activity against different Candida spp. and Aspergillus fumigatus. Among of them, target compounds 14a-2 and 20b-2 not only possessed the excellent broad-spectrum anti-fungal activity (MIC50, 0.125–2 μg/mL), but also maintained the anti-drug-resistant fungal activity (MIC50, 1–4 μg/mL). Preliminary mechanism study revealed the compounds (14a-2, 20b-2) could block the bio-synthetic pathway of ergosterol by inhibiting the dual-target (SE/CYP51) activity, and this finally caused the cleavage and death of fungal cells. In addition, we also discovered that compounds 14a-2 and 20b-2 with low toxic and side effects could exert the excellent therapeutic effect in mice model of fungal infection, which was worthy for further in-depth study.
l-amino alcohol derivatives exhibited high antifungal activity, but the metabolic stability of human liver microsomes in vitro was poor, and the half-life of optimal compound 5 was less than 5 min. To improve the metabolic properties of the compounds, the scaffold hopping strategy was adopted and a series of antifungal compounds with a dihydrooxazole scaffold was designed and synthesized. Compounds A33-A38 substituted with 4-phenyl group on dihydrooxazole ring exhibited excellent antifungal activities against C. albicans, C. tropicalis and C. krusei, with MIC values in the range of 0.03–0.25 μg/mL. In addition, the metabolic stability of compounds A33 and A34 in human liver microsomes in vitro was improved significantly, with the half-life greater than 145 min and the half-life of 59.1 min, respectively. Moreover, pharmacokinetic studies in SD rats showed that A33 exhibited favourable pharmacokinetic properties, with a bioavailability of 77.69%, and half-life (intravenous administration) of 9.35 h, indicating that A33 is worthy of further study.
Azole antifungals are commonly used to treat fungal infections but have resulted in the occurrence of drug resistance. Therefore, developing azole derivatives (AZDs) that can both combat established drug-resistant fungal strains and evade drug resistance is of great importance. In this study, we synthesized a series of AZDs with a fluconazole (FLC) skeleton conjugated with a mitochondria-targeting triphenylphosphonium cation (TPP⁺). These AZDs displayed potent activity against both azole-sensitive and azole-resistant Candida strains without eliciting obvious resistance. Moreover, two representative AZDs, 20 and 25, exerted synergistic antifungal activity with Hsp90 inhibitors against C. albicans strains resistant to the combination treatment of FLC and Hsp90 inhibitors. AZD 25, which had minimal cytotoxicity, was effective in preventing C. albicans biofilm formation. Mechanistic investigation revealed that AZD 25 inhibited the biosynthesis of the fungal membrane component ergosterol and interfered with mitochondrial function. Our findings provide an alternative approach to address fungal resistance problems.
The epidemiology of invasive fungal infections (IFIs) in immunocompromised individuals has changed over the last few decades, partially due to the increased use of antifungal agents to prevent IFIs. Although this strategy has resulted in an overall reduction in IFIs, a subset of patients develop breakthrough IFIs with substantial morbidity and mortality in this population. Here we review the most significant risk factors for breakthrough IFIs in hematology patients, solid organ transplant recipients, and patients in the intensive care unit, focusing particularly on host factors, and highlight areas that require future investigation.
Over the past decades, a dramatically tremendous rise in invasive fungal infection diseases attributed to the yeast Candida albicans in immunocompromised individuals poses a serious challenging issue. Another alarming concern is the emergence of multi-drug resistant pathogens to the existing medicines due to their overuse and misuse. 25% to 55% mortality, caused by the invasive infection, was recently reported. Despite a large variety of drugs available to treating invasive candidiasis, only two of them containing a 1,2,4-triazole core, fluconazole and itraconazole, are efficient for the infection therapy induced by fungal Candida species. Moreover, the long-term therapy associated with the azole medications has led to an increase in azole resistance and to high risk of toxicity. Despite numerous outstanding achievements in antifungal drug discovery, the development of novel potent antifungal agents in view to develop more potent and safer fungicides and to overcome the resistance problem associated with the actual drugs is becoming the main focus point for medicinal chemists. Thus, the purpose of the present review is to outline the progresses of the last decade in medicinal chemistry research devoted to the 1,2,4-triazole-based derivatives as potential antifungal agents. The structure activity relationship of these compounds is also discussed.
In order to develop novel antifungal agents, based on our previous work, a series of (2R,3R)-3-((3-substitutied-isoxazol-5-yl)methoxy)-2-(2,4-difluorophenyl)-1-(1H-1,2,4-triazol-1-yl) butan-2-ol (a1-a26) were designed and synthesized. All of the compounds exhibited good in vitro antifungal activities against eight human pathogenic fungi. Among them, compound a6 showed excellent inhibitory activity against Candida albicans and Candida parasilosis with MIC80 values of 0.0313 μg/mL. In addition, compounds a6, a9, a12, a13 and a14 exhibited moderate inhibitory activities against fluconazole-resistant isolates with MIC80 values ranging from 8 μg/mL to 16 μg/mL. Furthermore, compounds a6, a12 and a23 exhibited low inhibition profiles for CYP3A4. Clear SARs were analyzed, and the molecular docking experiment was carried out to further investigate the relationship between a6 and the target enzyme CYP51.
Invasive fungal infections (particularly candidiasis) are emerging as severe infectious diseases worldwide. Due to serious antifungal drug resistance, therapeutic efficacy of the current treatment for candidiasis are limited and associated with high mortality. However, it is highly challenging to develop novel strategies and effective therapeutic agents to combat with drug resistance. Herein, the first generation of lanosterol 14α-demethylase (CYP51)-histone deacetylase (HDAC) dual inhibitors were designed, which exhibited potent antifungal activity against azole-resistant clinical isolates. In particular, compounds 12h and 15j were highly active both in vitro and in vivo to treat azole-resistant candidiasis. Antifungal mechanism studies revealed that they acted by blocking ergosterol biosynthesis and HDAC catalytic activity in fungus, suppressing the function of efflux pump, yeast-to-hypha morphological transition and biofilm formation. Therefore, CYP51-HDAC dual inhibitors represent a promising strategy to develop novel antifungal agents against azole-resistant candidiasis.
Formaldehyde (FA, HCHO) is a highly reactive carbonyl species (hRCS), which is very harmful to humans and environments as a tissue fixative and preservative. Therefore, developing some highly sensitive, selective and rapid detection methods is significant for human health in food safety and environmental protection. Herein, a two-photon (TP) ratiometric sensor CmNp-CHO has been constructed by conjugating a TP donor (Π-push-pull-structure) with a FA off-on acceptor (functioned with hydrazides moiety) via a non-conjugated linker through fluorescence resonance energy transfer (FRET) mechanism. Such the scaffold affords CmNp-CHO a reliable and specific probe for detecting FA with two-well-resolved emission peaks separated by 124 nm. And it responds to FA rapidly with high selectivity and sensitivity during 1.0 minute, and a large ratio enhancement at I550/I426 with addition of 0-20μM FA, exhibiting~4-fold ratio increase and a fairly low LOD of 8.3±0.3 nM. Moreover, CmNp-CHO has been successfully employed for detecting FA in live cells, onion tissues and zebrafish, which exhibiting CmNp-CHO can be serve as a useful tool for investigating FA in real food application, and offering strong theoretical support and technical means for investigation of physiological and pathological function of FA.
We identified a new series of azole antifungal agents bearing a pyrrolotriazinone scaffold. These compounds exhibited a broad in vitro antifungal activity against pathogenic Candida spp. (fluconazole-susceptible and fluconazole-resistant) and were 10- to 100-fold more active than voriconazole against two Candida albicans isolates with known mechanisms of azole resistance (overexpression of efflux pumps and/or specific point substitutions in the Erg11p/CYP51 enzyme). Our lead compound 12 also displayed promising in vitro antifungal activity against some filamentous fungi such as Aspergillus fumigatus and the zygomycetes Rhizopus oryzae and Mucor circinelloides and an in vivo efficiency against two murine models of lethal systemic infections caused by Candida albicans.
Background:
Recently there has been an increase in Candida infections worldwide. A handful of species in the genus Candida are opportunistic pathogens and have been known to cause infections in immunocompromised or otherwise impaired hosts. These infections can be superficial, affecting the skin or mucous membrane, or invasive, which can be life-threatening. Azoles and echinocandins are antifungal drugs used globally to treat Candida infections. However, resistance to these antifungal drugs has increased in many of the Candida species, and the effects this has in the clinical setting can be seen.
Objectives:
Here, we discuss the mechanisms that Candida albicans, Candida dubliniensis, Candida glabrata, Candida parapsilosis, Candida tropicalis and Candida auris are implementing to increase resistance to azoles and echinocandins, and how they are affecting clinical, or hospital, settings worldwide.
Sources:
Different studies and papers describing the mechanisms of antifungal drugs and Candida species evolution to becoming resistant to these drugs were looked at for this review.
Content:
We discuss the mechanisms that azoles and echinocandins use against Candida species to treat infections, as well as the evolution of these fungi to become resistant to these drugs, and the effect this has in the clinical settings around the globe.
Implications:
Increased resistance to azoles and echinocandins by Candida species is an increasingly serious problem in clinical settings worldwide. Understanding the mechanisms used against antifungal drugs is imperative for patient treatment.
Currently, the available antifungal agents have significant clinical incompetency in terms of their clinical efficacy, antifungal spectrum, unfavorable pharmacokinetic profiles, substantial side effects and drug-drug interactions. Thus, the optimization and improvement of existing drugs and identification of new antifungal agents are urgently needed. Fluconazole is the first triazole alcohol drug with good in vivo efficacy against yeasts and well-known targets in fungal cells. However, the wide use of fluconazole as a first-line antifungal therapy has led to the development of resistance in clinical isolates of Candida species including Candida albicans and the emerging non-albicans Candida spp. In the last years, extensive efforts inflected to design and discovery of triazole alcohols derived from fluconazole by replacing one triazole ring with the proper side chain. In this paper, we have reviewed the structural modification of fluconazole to pursuit potent triazole alcohols with improved anti-Candida activity, and have highlighted their in vitro activities and in silico studies.
A series of carbazole-triazole conjugates were designed, synthesized and characterized by IR, NMR, and HRMS spectra. Biological assay showed that most of the synthesized compounds exhibited moderate and even strong antifungal activities, especially 3,6-dibromocarbazolyl triazole 5d displayed excellent inhibitory efficacy against most of the tested fungal strains (MIC ¼ 2e32 mg/mL) and effectively fungicidal ability towards C. albicans, C. tropicals and C. parapsilosis ATCC 22019 (MFC ¼ 4e8 mg/mL). Its combination use with fluconazole could enhance the antifungal efficacy, and compound 5d also did not obviously trigger the development of resistance in C. albicans even after 10 passages. Preliminary mechanism study revealed that the active molecule 5d could depolarize fungal membrane potential and intercalate into DNA to possibly block DNA replication, thus possibly exhibiting its powerful antifungal abilities. Conjugate 5d could interact with HSA, which was constructive for the further design, modification and screening of drug molecules. Docking investigation demonstrated a non-covalent binding of 5d with CYP51 through hydrogen bond and hydrophobicity. These results strongly suggested that compound 5d could act as a potential template for the development of promising antifungal drugs.
Microorganisms have a remarkable capacity to evolve resistance to antimicrobial agents, threatening the efficacy of the limited arsenal of antimicrobials and becoming a dire public health crisis. This is of particular concern for fungal pathogens, which cause devastating invasive infections with treatment options limited to only three major classes of antifungal drugs. The paucity of antifungals with clinical utility is in part due to close evolutionary relationships between these eukaryotic pathogens and their human hosts, which limits the unique targets to be exploited therapeutically. This review highlights the mechanisms by which fungal pathogens of humans evolve resistance to antifungal drugs, which provide crucial insights to enable development of novel therapeutic strategies to thwart drug resistance and combat fungal infectious disease.
With the increasing morbidity and mortality of invasive fungal infections and the emergence of severe antifungal drug resistance, new drug targets and novel antifungal agents are urgently needed. Recently, better understanding of fungal pathogenesis has contributed to the rapid emergence of potential antifungal drug targets. This perspective aims to provide a comprehensive review of new antifungal targets and of medicinal chemistry efforts toward inhibitor discovery. Particular focus will be placed on the druggability of the targets and their potential to treat resistant fungal infections. Innovative strategies for the next generation of antifungal therapy, such as virulence factors, protein-protein interactions, and immune response-based proteins, will also be highlighted.
The extensive use of fluconazole (FLC) and other azole drugs has caused the emergence and rise of azole-resistant fungi. The fungistatic nature of FLC in combination with toxicity concerns have resulted in an increased demand for new azole antifungal agents. Herein, we report the synthesis and antifungal activity of novel alkylated piperazines and alkylated piperazine-azole hybrids, their time-kill studies, their hemolytic activity against murine erythrocytes, as well as their cytotoxicity against mammalian cells. Many of these molecules exhibited broad-spectrum activity against all tested fungal strains, with excellent minimum inhibitory concentration (MIC) values against non-albicans Candida and Aspergillus strains. The most promising compounds were found to be less hemolytic than the FDA-approved antifungal agent voriconazole (VOR). Finally, we demonstrate that the synthetic alkylated piperazine-azole hybrids do not function by fungal membrane disruption, but instead by disruption of the ergosterol biosynthetic pathway via inhibition of the 14α-demethylase enzyme present in fungal cells.
We report the first Cu(II)-based fluorescent sensors for ratiometric detection of nitric oxide. The two probes operate by energy transfer between hydroxycoumarin and fluorescein chromophores, contain polyproline or piperazine as...
Invasive fungal infections continue to appear in record numbers as the immunocompromised population of the world increases, owing partially to the increased number of individuals who are infected with HIV and partially to the successful treatment of serious underlying diseases. The effectiveness of current antifungal therapies - polyenes, flucytosine, azoles and echinocandins (as monotherapies or in combinations for prophylaxis, or as empiric, pre-emptive or specific therapies) - in the management of these infections has plateaued. Although these drugs are clinically useful, they have several limitations, such as off-target toxicity, and drug-resistant fungi are now emerging. New antifungals are therefore needed. In this Review, I discuss the robust and dynamic antifungal pipeline, including results from preclinical academic efforts through to pharmaceutical industry products, and describe the targets, strategies, compounds and potential outcomes.
Introduction: Superficial infections involving the skin and mucosa are the most common fungal disease in humans. Fungi can also produce invasive infections (IFI), which are increasing in incidence among the growing population of immunocompromised patients, and are characterized by a high mortality rate. Amphotericin B, new triazoles and echinocandins have improved treatment options in IFI. However, the frequency of less common and more resistant fungi, the limited activity of available antifungal drugs and their undesirable side effects reflect the urgent need for the development of new therapeutic strategies.
Areas covered: This review summarizes the patents granted from August 2013 to June 2016 for antifungal compounds, reflecting the advances made by pharmaceutical companies and research groups in the discovery of new natural or synthetic antifungal compounds as well as the improvement of previously patented structures with antifungal activity.
Expert opinion: in the period covered here, progress has been in the development of new antifungal compounds or analogs of existing drugs with broad spectrum of activity, more favorable pharmacokinetic profiles or better bioavailability. However, the development of more promising approaches as antifungal compounds with broader antifungal activity and fungal-specific mechanisms of action are a high priority.
Invasive fungal infections (IFI) are an emerging problem worldwide with invasive candidiasis and candidemia responsible for the majority of cases. This is predominantly driven by the widespread adoption of aggressive immunosuppressive therapy among certain patient populations (e.g., chemotherapy, transplants) and the increasing use of invasive devices such as central venous catheters (CVCs). The use of new immune modifying drugs has also opened up an entirely new spectrum of patients at risk of IFIs. While the epidemiology of candida infections has changed in the last decade, with a gradual shift from C. albicans to non-albicans candida (NAC) strains which may be less susceptible to azoles, these changes vary between hospitals and regions depending on the type of population risk factors and antifungal use. In certain parts of the world, the incidence of IFI is strongly linked to the prevalence of other disease conditions and the ecological niche for the organism; for instance cryptococcal and pneumocystis infections are particularly common in areas with a high prevalence of HIV disease. Poorly controlled diabetes is a major risk factor for invasive mould infections. Environmental factors and trauma also play a unique role in the epidemiology of mould infections, with well-described hospital outbreaks linked to the use of contaminated instruments and devices. Blastomycosis is associated with occupational exposure (e.g., forest rangers) and recreational activities (e.g., camping and fishing).
The complexity of Alzheimer's disease (AD) calls for search of multifunctional compounds as potential candidates for effective therapy. A series of phthalimide and saccharin derivatives linked by different alicyclic fragments (piperazine, hexahydropyrimidine, 3-aminopyrrolidine or 3-aminopiperidine) with phenylalkyl moieties attached have been designed, synthesized, and evaluated as multifunctional anti-AD agents with cholinesterase, β-secretase and β-amyloid inhibitory activities. In vitro studies showed that the majority of saccharin derivatives with piperazine moiety and one phthalimide derivative with 3-aminopiperidine fragment exhibited inhibitory potency toward acetylcholinesterase (AChE) with EeAChE IC50 values ranging from 0.83 μM to 19.18 μM. The target compounds displayed inhibition of human β-secretase-1 (hBACE1) ranging from 26.71% to 61.42% at 50 μM concentration. Among these compounds, two multifunctional agents (26, [2-(2-(4-benzylpiperazin-1-yl)ethyl)benzo[d]isothiazol-3(2H)-one 1,1-dioxide] and 52, 2-(2-(3-(3,5-difluorobenzylamino)piperidin-1-yl)ethyl)isoindoline-1,3-dione) have been identified. Compound 26 exhibited the highest inhibitory potency against EeAChE (IC50 = 0.83 μM) and inhibitory activity against hBACE1 (33.61% at 50 μM). Compound 52 is a selective AChE inhibitor (IC50 AChE = 6.47 μM) with BACE1 inhibitory activity (26.3% at 50 μM) and it displays the most significant Aβ anti-aggregating properties among all the obtained compounds (39% at 10 μM). Kinetic and molecular modeling studies indicate that 26 may act as non-competitive AChE inhibitor able to interact with both catalytic and peripheral active site of the enzyme.
Dimorphic fungi cause several endemic mycoses which range from subclinical respiratory infections to life-threatening systemic disease. Pathogenic-phase cells of Histoplasma, Blastomyces, Paracoccidioides and Coccidioides escape elimination by the innate immune response with control ultimately requiring activation of cell-mediated immunity. Clinical management of disease relies primarily on antifungal compounds; however, dimorphic fungal pathogens create a number of challenges for antifungal drug therapy. In addition to the drug toxicity issues known for current antifungals, barriers to efficient drug treatment of dimorphic fungal infections include natural resistance to the echinocandins, residence of fungal cells within immune cells, the requirement for systemic delivery of drugs, prolonged treatment times, potential for latent infections, and lack of optimized standardized methodology for in vitro testing of drug susceptibilities. This review will highlight recent advances, current therapeutic options, and new compounds on the horizon for treating infections by dimorphic fungal pathogens.
Triazoles with fused-heterocycle nuclei were synthesized and evaluated for their in vitro antifungal activity. Effects of position and electronic properties of substituents were investigated. Tetrahydro-[1,2,4]triazole[1,5-a]pyrazine and tetrahydro-[1,2,4]triazole[1,5-a]pyrazine nuclei were preferable to the other four fused-heterocycle nuclei investigated. Potent in vitro antifungal activity, broad spectrum and better water solubility were attained when triazoles containing nitrogen aromatic heterocycles were attached to these two nuclei. The most potent compounds 27aa and 45x exhibited two- to four fold potency against Candida, Cryptococcus, and Aspergillus spp., compared with those of voriconazole and ravuconazole. They also showed moderate activity against fluconazole-resistant strains of Candida albicans and low activity in hERG inhibition. The disulfate salt of 45x (compound 58) exhibited high aqueous solubility (>100.0 mg/ml) at near-neutral pH. Mice infected with C. albicans SC5314 and C. albicans 103 (fluconazole-resistant strain) and administered with 27aa displayed significantly improved survival rates. 27aa also showed favorable pharmacokinetic profiles.
Invasive fungal disease continues to be a problem associated with significant morbidity and high mortality in immunocompromised and, to a lesser extent, immunocompetent individuals. Triazole antifungals have emerged as front-line drugs for the treatment and prophylaxis of many systemic mycoses. Fluconazole plays an excellent role in prophylaxis, empirical therapy, and the treatment of both superficial and invasive yeast fungal infections. Voriconazole is strongly recommended for pulmonary invasive aspergillosis. Posaconazole shows a very wide spectrum of activity and its primary clinical indications are as salvage therapy for patients with invasive aspergillosis and prophylaxis for patients with neutropenia and haematopoietic stem-cell transplant recipients. Itraconazole also has a role in the treatment of fungal skin and nail infections as well as dematiaceous fungi and endemic mycoses. Fluconazole and voriconazole are well absorbed and exhibit high oral bioavailability, whereas the oral bioavailability of itraconazole and posaconazole is lower and more variable. Posaconazole absorption depends on administration with a high-fat meal or nutritional supplements. Itraconazole and voriconazole undergo extensive hepatic metabolism involving the cytochrome P450 system. The therapeutic window for triazoles is narrow, and inattention to their pharmacokinetic properties can lead to drug levels too low for efficacy or too high for good tolerability or safety. This makes these agents prime candidates for therapeutic drug monitoring (TDM). Target drug concentrations for voriconazole and itraconazole should be >1 μg/mL and for posaconazole >1.5 μg/mL for treatment. Blood should be drawn once the patient reaches steady state, which occurs after 5 and 7 days of triazole therapy. Routine TDM of fluconazole is not required given its highly favourable pharmacokinetic profile and wide therapeutic index. The aim of this review is to provide a brief update on the pharmacology, activity, clinical efficacy, safety and cost of triazole agents (itraconazole, fluconazole, voriconazole and posaconazole) and highlight the clinical implications of similarities and differences.
In order to meet the urgent need for novel antifungal agents with improved activity and broader spectrum, a series of 1-(1H-1,2,4-triazol-1-yl)-2-(2,4-difluorophenyl)-3-[(4-substituted trifluoromethyl phenyl)-piperazin-1-yl]-propan-2-ols were designed, synthesized and evaluated as antifungal agents. The MIC(80) values indicate that the compounds 7a-7q, 8a-8d showed higher antifungal activities against Candida albicans than 5a-5i, 6a-6j. Moreover, the molecular model for the binding between compound 5a, 7a and the active site of CACYP51 was provided based on the computational docking results, and the structure-activity relationship was analyzed.
Based on the structure of the active site of cytochrome P450 14α-demethylase (CYP51) and the conclusions of the structure-activity relationships of azole antifungals, a series of 1-(2-(2,4-difluoro-phenyl)-2-hydroxy-3-(1H-1,2,4-triazol-1-yl)propyl)-1H-1,2,4-triazol-5(4H)-one of fluconazole analogs was synthesized. All compounds were characterized by IR, HRMS, (1)HNMR and (13)C NMR spectroscopic analysis. Results of preliminary antifungal in vitro test using eight human pathogenic species showed that some compounds displayed comparable or even better antifungal activities than reference drug fluconazole and that compound 3i exhibited significant activity against Candida albicans being worthy of further optimization.
Twenty-eight novel triazole derivatives (compounds 1a-v, 2a-f) have been synthesized for structure-activity relationship studies as antifungal agents. The compounds were designed on the basis of the structure of fluconazole and molecular modeling of the active site of the cytochrome P450 14α-demethylase (CYP51). All of them are reported for the first time. Their chemical structures are characterized by (1) H NMR, (13) C NMR, LC-MS, and elemental analysis. The antifungal activities have been evaluated in vitro by measuring the minimal inhibitory concentrations (MICs). Compounds 1a-v exhibited higher activity against nearly all fungi tested except Aspergillus fumigatus (A. fum) than fluconazole (FCZ). The computational molecular docking experiments indicated that the inhibition of CYP51 involves a coordination bond with iron of the heme group, a hydrophilic H-bonding region, a hydrophobic region, and a narrow hydrophobic binding cleft.
The enzyme isoprenylcysteine carboxyl methyltransferase (Icmt) plays an important role in the post-translational modification of proteins that are involved in the regulation of cell growth. The indole acetamide cysmethynil is by far the most potent and widely investigated Icmt inhibitor, but it has modest antiproliferative activity and may have pharmacokinetic limitations due to its lipophilic character. We report here that cysmethynil can be structurally modified to give analogues that are as potent in inhibiting Icmt but with significantly greater antiproliferative activity. Key modifications were the replacement of the acetamide side chain by tertiary amino groups, the n-octyl side chain by isoprenyl and the 5-m-tolyl ring by fluorine. Moreover, these analogues have lower lipophilicities that could lead to improved pharmacokinetic profiles.
Major developments in research into the azole class of antifungal agents during the 1990s have provided expanded options for the treatment of many opportunistic and endemic fungal infections. Fluconazole and itraconazole have proved to be safer than both amphotericin B and ketoconazole. Despite these advances, serious fungal infections remain difficult to treat, and resistance to the available drugs is emerging. This review describes present and future uses of the currently available azole antifungal agents in the treatment of systemic and superficial fungal infections and provides a brief overview of the current status of in vitro susceptibility testing and the growing problem of clinical resistance to the azoles. Use of the currently available azoles in combination with other antifungal agents with different mechanisms of action is likely to provide enhanced efficacy. Detailed information on some of the second-generation triazoles being developed to provide extended coverage of opportunistic, endemic, and emerging fungal pathogens, as well as those in which resistance to older agents is becoming problematic, is provided.
Incidence of systemic candidiasis is increasing with improvement in the survival of high risk neonates who undergo multiple interventions. Therapies available to treat systemic fungal infection are few and have several drawbacks. Fluconazole, a new triazole derivative may be a useful anti-fungal agent in view of its excellent oral absorption, easy administration, low plasma protein affinity, long half-life, high concentrations in urine and CSF, minimal adverse reactions, wide spectrum of anti-fungal activity and high specificity for fungal cytochrome P450 system. Its utility in neonates and children with candidiasis has already been documented by few case reports and studies.
The three-dimensional structure of lanosterol 14alpha-demethylase (P450(14DM), CYP51) of Candida albicans was modeled on the basis of crystallographic coordinates of four prokaryotic P450s: P450BM3, P450cam, P450terp, and P450eryF. The P450(14DM) sequence was aligned to those of known proteins using a knowledge-based alignment method. The main chain coordinates of the core regions were transferred directly from the corresponding coordinates of P450BM3. The side chain conformations of the core regions were determined by the conformations of the equivalent residues with the highest homologous scores in four crystal structures. The model was then refined using molecular mechanics and molecular dynamics. The reliability of the resulting model was assessed by Ramachandran plots, Profile-3D, hydropathy plot analysis, and by analyzing the consistency of the model with the experimental data. The structurally and functionally important residues such as the heme binding residues, the residues interacting with redox-partner protein and/or involved in electron transfer, the residues lining substrate access channel, and the substrate binding residues were identified from the model. These residues are candidates for further site-directed mutagenesis and site-specific antipeptide antibody binding experiments. The active analogue approach was employed to search the pharmacophoric conformations for 14 azole antifungals. The resulting bioactive conformations were docked into the active site of lanosterol 14alpha-demethylase of Candida albicans. All 14 azole antifungals are shown to have a similar docking mode in the active site. The halogenated phenyl group of azole inhibitors is deep in the same hydrophobic binding cleft as the 17-alkyl chain of substrate. The pi-pi stacking interaction might exist between halogenated phenyl ring of inhibitors and the aromatic ring of residue Y132. The long side chains of some inhibitors such as itraconazole and ketoconazole surpass the active site and interact with the residues in the substrate access channel. To compare with mammalian enzymes, structurally selective residues of the active site of fungal lanosterol 14alpha-demethylase are distributed in the C terminus of F helix, beta6-1 sheet and beta6-2 sheet.
Itraconazole is a broad spectrum triazole antifungal agent. It has favourable pharmacodynamic and pharmacokinetic profiles and is available as both oral and i.v. formulations. Over the last two decades, clinical and animal infection studies have demonstrated the efficacy of itraconazole in a wide range of superficial fungal infections including difficult-to-treat dermatophytoses and onychomycoses. Furthermore, shortened treatment regimens have proven to be effective, ranging from 1-day treatment for vaginal candidosis to 1-week pulse therapy per month, for 2-4 months, in onychomycosis and follicular dermatophytosis. Clinical experience with itraconazole in the treatment of deep mycoses is less comprehensive. However, results in systemic candidosis, sporotrichosis, blastomycosis, paracoccidioiodomycosis, certain types of histoplasmosis and aspergillosis are extremely encouraging. Itraconazole is less effective in the treatment of chromomycosis and coccidioidomycosis. Nevertheless, considering the refractory nature of these diseases, itraconazole has proven to be a valuable addition to the antifungal drugs currently available for treatment. Itraconazole has been well-tolerated with doses of up to 400 mg/day being generally free of serious adverse effects. However, a potential for drug interactions exists, mediated through the cytochrome P450 enzyme 3A4 system, which should be considered when itraconazole is used as part of a multi-drug regimen.
There is an increased awareness of the morbidity and mortality associated with fungal infections caused by resistant fungi in various groups of patients. Epidemiological studies have identified risk factors associated with antifungal drug resistance. Selection pressure due to the continuous exposure to azoles seems to have an essential role in developing resistance to fluconazole in Candida species. Haematological malignancies, especially acute leukaemia with severe and prolonged neutropenia, seem to be the main risk factors for acquiring deep-seated mycosis caused by resistant filamentous fungi, such us Fusarium species, Scedosporium prolificans, and Aspergillus terreus. The still unacceptably high mortality rate associated with some resistant mycosis indicates that alternatives to existing therapeutic options are needed. Potential measures to overcome antifungal resistance ranges from the development of new drugs with better antifungal activity to improving current therapeutic strategies with the present antifungal agents. Among the new antifungal drugs, inhibitors of beta glucan synthesis and second-generation azole and triazole derivatives have characteristics that render them potentially suitable agents against some resistant fungi. Other strategies including the use of high doses of lipid formulations of amphotericin B, combination therapy, and adjunctive immune therapy with cytokines are under investigation. In addition, antifungal control programmes to prevent extensive and inappropriate use of antifungals may be needed.
To review the pharmacology, in vitro susceptibility, pharmacokinetics, clinical efficacy, and adverse effects of voriconazole, a triazole antifungal agent.
A MEDLINE search, restricted to English language, was conducted from 1990 to June 2002. Supplementary sources included program abstracts from the Interscience Conference on Antimicrobial Agents and Chemotherapy and the Infectious Diseases Society of America from 1996 to 2001 and manufacturer information available through the Food and Drug Administration's Web site.
All published and unpublished trials and abstracts citing voriconazole were selected.
Voriconazole has shown in vitro activity against many yeasts and a variety of mold and dermatophyte isolates. Voriconazole can be administered either orally or parenterally. It exhibits good oral bioavailability, wide tissue distribution including distribution into the central nervous system, and hepatic metabolism. Drug interactions occur through inhibition of the CYP2C9, CYP2C19, and CYP3A4 isoenzymes, resulting in alterations in kinetic parameters of either voriconazole or the interacting agent. Efficacy has been illustrated in open, noncomparative studies of aspergillosis in immunocompromised patients. Human case reports describe successful treatment of rare fungal pathogens. The most commonly reported adverse events include visual disturbances and elevations in liver function tests.
Voriconazole is at least as effective as amphotericin B in the treatment of acute invasive aspergillosis in immunocompromised patients. It has similar efficacy as fluconazole in treatment of esophageal candidiasis. Voriconazole did not achieve statistical non-inferiority to liposomal amphotericin B for empirical therapy in patients with neutropenia and persistent fever, diminishing enthusiasm for use in this indication until additional trials are completed. Based on case reports and in vitro efficacy, voriconazole may prove to be a clinically useful agent in the treatment of other fungal disease.
Invasive fungal infections are occurring with increasing frequency secondary to medical advances in the areas of transplantation, cancer management and autoimmune diseases. Unfortunately, the currently available antifungal armamentarium does not meet the increasing needs of managing infection in these complex patient populations. Posaconazole, a new triazole antifungal agent, is being investigated for its role in treating serious infections due to yeasts and molds. This new drug offers an expanded spectrum of activity over other members of its class. In addition to potent activity against fluconazole-resistant Candida and refractory cases of aspergillosis, posaconazole demonstrates activity against Zygomycetes. Posaconazole is a well-tolerated agent that offers a diminished toxicity profile compared with other currently marketed systemic antifungal agents. Clinical success rates thus far have been promising, although the exact role of this agent in treating and preventing invasive fungal infections is yet to be determined.
Blood platelets store sphingosine 1-phosphate (S1P) abundantly and release this bioactive lipid extracellularly. S1P acts as an intercellular mediator through interaction with the endothelial differentiation gene (EDG)/S1P family of G protein-coupled receptors. Of the EDG family S1P receptors, EDG-5 (S1P2) is inhibited in migration induced by S1P. Diabetes impairs numerous aspects of tissue repair. Failure of wound angiogenesis is known to delay diabetic wound healing.
We examined whether S1P subcutaneous injection could improve the healing of full-thickness skin wounds in healthy and diabetic mice. We further determine if the combined S1P and EDG-5 (S1P2) antagonist injection in diabetic mice could affect wound healing. Finally, we examined the histopathological findings of the wound following S1P injection in diabetic mice.
Eight- to 10-week-old BALA/c mice, diabetic db/db mice and Wister rats were used for the studies. A full-thickness wound was made on the dorsal skin of the healthy and diabetic mice. Either 10 microM or 100 microM of S1P or vehicle control (BSA/PBS) was injected into the wound bed every day. We calculated the wound area after each injection. EDG-5 (S1P2) antagonist (JTE-013) or vehicle (DMSO) was then injected in addition to the S1P around the dorsal wound of diabetic mice and the wound diameter was measured. Wound tissue samples were excised following injection for histopathological examination.
Wound area in normal BALA/c mice did not significantly decrease upon S1P injection compared to S1P-untreated controls. S1P injection alone showed significant promotion of wound healing in diabetic mice compared to no S1P treatment. The combination of S1P and EDG-5 (S1P2) receptor antagonist administration induced maximal wound healing in diabetic mice. Histopathological examination revealed that S1P induces neo-vascularization potential in rats and diabetic mice wound.
S1P injection in diabetic mice significantly accelerated cutaneous wound healing in the neo-vascularization process. The results demonstrate that S1P affects and sustains all key cellular processes responsible for wound repair and point to a unique potential for this molecule in the therapy of diabetic wounds, particularly as an angiogenic agent in treatment of diabetic wounds.