Emerging echinocandins for treatment of invasive fungal infections

Emerging Prospects for Combating Fungal Infections by Targeting Phosphatidylinositol Transfer Proteins

The emergence of fungal “superbugs” resistant to the limited cohort of anti-fungal agents available to clinicians is eroding our ability to effectively treat infections by these virulent pathogens. As the threat of fungal infection is escalating worldwide, this dwindling response capacity is fueling concerns of impending global health emergencies. These developments underscore the urgent need for new classes of anti-fungal drugs and, therefore, the identification of new targets. Phosphoinositide signaling does not immediately appear to offer attractive targets due to its evolutionary conservation across the Eukaryota. However, recent evidence argues otherwise. Herein, we discuss the evidence identifying Sec14-like phosphatidylinositol transfer proteins (PITPs) as unexplored portals through which phosphoinositide signaling in virulent fungi can be chemically disrupted with exquisite selectivity. Recent identification of lead compounds that target fungal Sec14 proteins, derived from several distinct chemical scaffolds, reveals exciting inroads into the rational design of next generation Sec14 inhibitors. Development of appropriately refined next generation Sec14-directed inhibitors promises to expand the chemical weaponry available for deployment in the shifting field of engagement between fungal pathogens and their human hosts.

The putative polysaccharide synthase AfCps1 regulates Aspergillus fumigatus morphogenesis and conidia immune response in mouse bone marrow-derived macrophages

Aspergillus fumigatus is a well-known opportunistic pathogen that causes invasive aspergillosis (IA) infections with high mortality in immunosuppressed individuals. Morphogenesis, including hyphal growth, conidiation, and cell wall biosynthesis is crucial in A. fumigatus pathogenesis. Based on a previous random insertional mutagenesis library, we identified the putative polysaccharide synthase gene Afcps1 and its para-log Afcps2. Homologs of the cps gene are commonly found in the genomes of most fungal and some bacterial pathogens. Afcps1/cpsA is important in sporulation, cell wall composition, and virulence. However, the precise regulation patterns of cell wall integrity by Afcps1/cpsA and further effects on the immune response are poorly understood. Specifically, our in-depth study revealed that Afcps1 affects cell-wall stability, showing an increased resistance of ΔAfcps1 to the chitinmicrofibril destabilizing compound calcofluor white (CFW) and susceptibility of ΔAfcps1 to the β-(1,3)-glucan synthase inhibitor echinocandin caspofungin (CS). Additionally, deletion of Afcps2 had a normal sporulation phenotype but caused hypersensitivity to Na⁺ stress, CFW, and Congo red (CR). Specifically, quantitative analysis of cell wall composition using high-performance anion exchange chromatography-pulsed amperometric detector (HPAEC-PAD) analysis revealed that depletion of Afcps1 reduced cell wall glucan and chitin contents, which was consistent with the down-regulation of expression of the corresponding biosynthesis genes. Moreover, an elevated immune response stimulated by conidia of the ΔAfcps1 mutant in marrow-derived macrophages (BMMs) during phagocytosis was observed. Thus, our study provided new insights into the function of polysaccharide synthase Cps1, which is necessary for the maintenance of cell wall stability and the adaptation of conidia to the immune response of macrophages in A. fumigatus.

Opportunistic Invasive Cutaneous Fungal Infections Associated with Administration of Cyclosporine to Dogs with Immune-mediated Disease

Background

Opportunistic invasive fungal infections (OIFIs) occur in dogs administered immunosuppressive medications. However, the epidemiology of OIFIs among dogs undergoing immunosuppressive treatment is poorly understood. The aims of this study were to (1) estimate the incidence of OIFIs among dogs diagnosed with certain immune‐mediated diseases and treated with immunosuppressive drugs, and (2) determine if administration of particular drug(s) was a risk factor for OIFIs.

Hypothesis

Dogs receiving cyclosporine treatment (alone or as part of a multidrug protocol) are at higher risk of developing OIFIs.

Animals

One hundred and thirteen client‐owned dogs diagnosed with select immune‐mediated diseases: 42 with IMHA, 29 with ITP, 34 with IMPA, and 8 with Evans syndrome.

Methods

Retrospective cohort study. Medical records of dogs presenting to the Texas A&M University, Veterinary Medical Teaching Hospital between January 2008 and December 2015, and treated for 1 or more of IMHA, IMPA, ITP, or Evans syndrome were retrospectively reviewed. Dogs that did not develop an OIFI were excluded if they died, were euthanized, or were lost to follow‐up within 120 days of initiation of immunosuppressive treatment.

Results

Fifteen dogs of 113 (13%) were diagnosed with an OIFI based on 1 or more of cytology, culture, or histopathology. The odds of developing an OIFI were greater among dogs that were treated with cyclosporine (OR = 7.1, P = 0.017; 95% CI, 1.5–34.4) and among male dogs (OR = 5.1, P = 0.018; 95% CI, 1.4–17.9).

Conclusions and Clinical Importance

OIFIs were significantly more likely in male dogs and those receiving cyclosporine. It is important to consider OIFIs as a potential complication of immunosuppressive treatment, particularly cyclosporine.

Differential effects of antifungal agents on expression of genes related to formation of Candida albicans biofilms

The purpose of this study was to analyse specific molecular mechanisms involved in the intrinsic resistance of C. albicans biofilms to antifungals. We investigated the transcriptional profile of three genes (BGL2, SUN41, ECE1) involved in Candida cell wall formation in response to voriconazole or anidulafungin after the production of intermediate and mature biofilms. C. albicans M61, a well-documented biofilm producer strain, was used for the development of intermediate (12 h and 18 h) and completely mature biofilms (48 h). After exposure of cells from each biofilm growth mode to voriconazole (128 and 512 mg l(-1)) or anidulafungin (0.25 and 1 mg l(-1)) for 12-24 h, total RNA samples extracted from biofilm cells were analysed by RT-PCR. The voriconazole and anidulafungin biofilm MIC was 512 and 0.5 mg l(-1) respectively. Anidulafungin caused significant up-regulation of SUN41 (3.7-9.3-fold) and BGL2 (2.2-2.8 fold) in intermediately mature biofilms; whereas, voriconazole increased gene expression in completely mature biofilms (SUN41 2.3-fold, BGL2 2.1-fold). Gene expression was primarily down-regulated by voriconazole in intermediately, but not completely mature biofilms. Both antifungals caused down-regulation of ECE1 in intermediately mature biofilms.

Mechanisms of echinocandin antifungal drug resistance

Fungal infections due to Candida and Aspergillus species cause extensive morbidity and mortality, especially among immunosuppressed patients, and antifungal therapy is critical to patient management. Yet only a few drug classes are available to treat invasive fungal diseases, and this problem is compounded by the emergence of antifungal resistance. Echinocandin drugs are the preferred choice to treat candidiasis. They are the first cell wall-active agents and target the fungal-specific enzyme glucan synthase, which catalyzes the biosynthesis of β-1,3-glucan, a key cell wall polymer. Therapeutic failures occur rarely among common Candida species, with the exception of Candida glabrata, which is frequently multidrug resistant. Echinocandin resistance in susceptible species is always acquired during therapy. The mechanism of resistance involves amino acid changes in hot-spot regions of Fks subunits of glucan synthase, which decrease the sensitivity of the enzyme to drug. Cellular stress response pathways lead to drug adaptation, which promotes the formation of resistant fks strains. Clinical factors promoting echinocandin resistance include empiric therapy, prophylaxis, gastrointestinal reservoirs, and intra-abdominal infections. A better understanding of the echinocandin-resistance mechanism, along with cellular and clinical factors promoting resistance, will facilitate more effective strategies to overcome and prevent echinocandin resistance.

Echinocandin resistance, susceptibility testing and prophylaxis: implications for patient management

This article addresses the emergence of echinocandin resistance among Candida species, mechanisms of resistance, factors that promote resistance and confounding issues surrounding standard susceptibility testing. Fungal infections remain a significant cause of global morbidity and mortality, especially among patients with underlying immunosupression. Antifungal therapy is a critical component of patient management for acute and chronic diseases. Yet, therapeutic choices are limited due to only a few drug classes available to treat systemic disease. Moreover, the problem is exacerbated by the emergence of antifungal resistance, which has resulted in difficult to manage multidrug resistant strains. Echinocandin drugs are now the preferred choice to treat a range of candidiasis. These drugs target and inhibit the fungal-specific enzyme glucan synthase, which is responsible for the biosynthesis of a key cell wall polymer. Therapeutic failures involving acquisition of resistance among susceptible organisms like Candida albicans is largely a rare event. However, in recent years, there is an alarming trend of increased resistance among strains of Candida glabrata, which in many cases are also resistant to azole drugs. Echinocandin resistance is always acquired during therapy and the mechanism of resistance is well established to involve amino acid changes in "hot-spot" regions of the Fks subunits carrying the catalytic portion of glucan synthase. These changes significantly decrease the sensitivity of the enzyme to drug resulting in higher MIC values. A range of drug responses, from complete to partial refractory response, is observed depending on the nature of the amino acid substitution, and clinical responses are recapitulated in pharmacodynamic models of infection. The cellular processes promoting the formation of resistant Fks strains involve complex stress response pathways, which yield a variety of adaptive compensatory genetic responses. Stress-adapted cells become drug tolerant and can form stable drug resistant FKS mutations with continued drug exposure. A major concern for resistance detection is that classical broth microdilution techniques show significant variability among clinical microbiology laboratories for certain echinocandin drugs and Candida species. The consequence is that susceptible strains are misclassified according to established clinical breakpoints, and this has led to confusion in the field. Clinical factors that appear to promote echinocandin resistance include the expanding use of antifungal agents for empiric therapy and prophylaxis. Furthermore, host reservoirs such as biofilms in the gastrointestinal tract or intra-abdominal infections can seed development of resistant organisms during therapy. A fundamental understanding of the primary molecular resistance mechanism, along with cellular and clinical factors that promote resistance emergence, is critical to develop better diagnostic tools and therapeutic strategies to overcome and prevent echinocandin resistance.

Antifungal treatment of small animal veterinary patients

Antifungal therapy has progressed significantly with the development of new drugs directed at various processes in fungal cell metabolism. Within veterinary medicine, treatment options for systemic mycoses remain limited to amphotericin B, ketoconazole, fluconazole, and itraconazole. However, newer triazoles, echinocandins, and lipid-based formulations of amphotericin B are now approved for use in humans. This article provides a comprehensive review of the antifungal medications available for veterinary patients, and includes a brief discussion of the newer, presently cost-prohibitive, antifungal therapies used for systemic mycoses in humans.

Conazoles

This review provides a historical overview of the analog based drug discovery of miconazole and its congeners, and is focused on marketed azole antifungals bearing the generic suffix “conazole”. The antifungal activity of miconazole, one of the first broad-spectrum antimycotic agents has been mainly restricted to topical applications. The attractive in vitro antifungal spectrum was a starting point to design more potent and especially orally active antifungal agents such as ketoconazole, itraconazole, posaconazole, fluconazole and voriconazole. The chemistry, in vitro and in vivo antifungal activity, pharmacology, and clinical applications of these marketed conazoles has been described.

Efficacy of anidulafungin, caspofungin and fluconazole in the early phase of infection in a neutropenic murine invasive candidiasis model

In this study, we investigated the in vivo efficacy of anidulafungin during the early phase of disseminated candidiasis in a neutropenic murine model and compared the results with those obtained for fluconazole. Antifungal efficacy was evaluated by reduction of fungal burden in the tissues of infected animals at periodic intervals during the first day of treatment. The fungal burden in tissues of drug-treated mice was reduced compared with controls in a time-dependent manner. At 24h after drug treatment, a >2 log(10) reduction of fungal burden in the kidney was obtained in the anidulafungin- and caspofungin-treated mice compared with a ca. 1.2 log(10) reduction in fluconazole-treated mice (P<0.003). There was no significant difference in the splenic fungal burden at 24h. Thus, echinocandins have excellent antifungal activity in the early phase of disseminated Candida albicans infection and may contribute to an improved outcome in critically ill immunocompromised/neutropenic patients.

Antifungal agents, WO2009025733

BACKGROUND

The incidence and prevalence of serious mycoses continues to be a public health problem. These infections are an important cause of morbidity and mortality, especially in immunocompromised patients. The present patent deals with isolation and characterization of a 'pure' mixture of two novel isoxazolidinone-containing natural products from two new fungal strains. They have the partial structure of secalonic acid and show very good antifungal activity in mammals and plants and also synergism with other active ingredients.

OBJECTIVE

To analyze the activity of the isoxazolidinone-containing compounds in the present patent.

METHODS

To review the discovery and development of antifungal compounds in general and secalonic acid related compounds in particular.

CONCLUSION

The research of Parish and collaborators at Merck and Co. has isolated novel antifungal compounds with a new mode of action. These molecules may be considered potential antifungal leads for further clinical study.

Human fungal pathogen Candida albicans in the postgenomic era: an overview

Candida albicans is an opportunistic human fungal pathogen and is responsible for candidiasis. Owing to the improvement in healthcare, the number of immunocompromised patients in hospitals has increased worldwide and these individuals are susceptible to infections caused by many pathogenic microbes, among which C. albicans is one of the major players. Currently, the complete genome sequence of this pathogen is available and the size of this was estimated to be of 16 Mb. Annotation of C. albicans genome revealed that there are 6114 open reading frames (ORFs), of which 774 are specific to C. albicans. This poses a challenge as well as an opportunity to the Candida community to understand the functions of the unknown genes, especially those specific to C. albicans. Efforts have been made by the Candida community to systematically delete the ORFs and assign the functions. This will, in turn, help in understanding the biology of C. albicans and its interactions with animals as well as humans, and better drugs can be developed to treat Candida infections. In this article, we review updates on the Candida biology in the context of the availability of the genome sequence, its functional analysis and anti-Candida therapy. Finally, in the light of present trends in Candida research and current challenges, various opportunities are identified and suggestions are made.

Msb2 signaling mucin controls activation of Cek1 mitogen-activated protein kinase in Candida albicans

We have characterized the role that the Msb2 protein plays in the fungal pathogen Candida albicans by the use of mutants defective in the putative upstream components of the HOG pathway. Msb2, in cooperation with Sho1, controls the activation of the Cek1 mitogen-activated protein kinase under conditions that damage the cell wall, thus defining Msb2 as a signaling element of this pathway in the fungus. msb2 mutants display altered sensitivity to Congo red, caspofungin, zymolyase, or tunicamycin, indicating that this protein is involved in cell wall biogenesis. Msb2 (as well as Sho1 and Hst7) is involved in the transmission of the signal toward Cek1 mediated by the Cdc42 GTPase, as revealed by the use of activated alleles (Cdc42(G12V)) of this protein. msb2 mutants have a stronger defective invasion phenotype than sho1 mutants when tested on certain solid media that use mannitol or sucrose as a carbon source or under hypoxia. Interestingly, Msb2 contributes to growth under conditions of high osmolarity when both branches of the HOG pathway are altered, as triple ssk1 msb2 sho1 mutants (but not any single or double mutant) are osmosensitive. However, this phenomenon is independent of the presence of Hog1, as Hog1 phosphorylation, Hog1 translocation to the nucleus, and glycerol accumulation are not affected in this mutant following an osmotic shock. These results reveal essential functions in morphogenesis, invasion, cell wall biogenesis, and growth under conditions of high osmolarity for Msb2 in C. albicans and suggest the divergence and specialization of this signaling pathway in filamentous fungi.

Anidulafungin: a novel echinocandin for candida infections

A third echinocandin, anidulafungin, has recently been approved for Candida infections in the non-neutropenic patient. In the EU it is indicated for invasive candidiasis; in 2006 it was approved in the USA for candida esophagitis, candidemia, and two types of invasive infections, peritonitis and intra-abdominal abscesses. It is fungicidal against Candida species and fungistatic against Aspergillus species. In addition to its favorable tolerability in studies to date, it does not need adjustment for renal or hepatic insufficiency and has no known drug interactions. A steady state concentration can be achieved on day 2 following a loading dose of twice the maintenance concentration on day 1, and the drug is administered intravenously once daily. Cross resistance with other classes of antifungals is not a concern as it possesses a unique mechanism of action.

Utilization and dosage pattern of echinocandins for treatment of fungal infections in US hospital practice

OBJECTIVE

With the availability of multiple echinocandins in the US, recommended dosages and dosing schedules vary by agent but actual utilization practices are unknown. The purpose of this study was to describe the utilization and dosage pattern of intravenous echinocandins for treatment of fungal infections in US hospitals.

METHODS

The Premier Perspective Database was used to describe echinocandin use in 332 US hospitals. Adult patients hospitalized from January, 2006 through June, 2007 with at least one billing record for anidulafungin (Eraxis ** ), caspofungin (Cancidas dagger ), or micafungin (Mycamine double dagger ) were included. Hospitalizations with > 1 echinocandin or >or= 1 dosage with an FDA approved indication for fungal prophylaxis were excluded. Mixed multivariable models were developed to identify factors associated with mean daily dose. ** Eraxis, a registered trade name owned by Pfizer, Inc., New York, NY, USA dagger Cancidas, a registered trade name owned by Merck & Co., Inc., Whitehouse Station, NJ, USA double dagger Mycamine, a registered trade name owned by Astellas Pharma US, Inc., Deerfield, IL, USA.

RESULTS

The number of unique patient hospitalizations was 708 for anidulafungin, 15 739 for caspofungin, and 1199 for micafungin. A single echinocandin was utilized at 88.6% of hospitals. Micafungin patients had the highest prevalence of cancer, bone marrow transplant, solid organ transplant, HIV/AIDS, fungal infection, and neutropenia. Mean day 1 dose of echinocandin therapy was 171.2 +/- 85.4 mg, 79.7 +/- 25.6 mg, and 154.3 +/- 67.3 mg; and mean day 2 onwards dose was 98.7 +/- 39.4 mg, 53.1 +/- 12.5 mg, 122.6 +/- 39.4 mg for anidulafungin, caspofungin and micafungin, respectively. Commonly used loading doses were 200 mg (55.6%) for anidulafungin, 70 mg (57.2%) for caspofungin, and 200 mg (21.2%) for micafungin. The first-day dose of echinocandin therapy (vs. subsequent days) was most strongly associated with mean daily dose.

CONCLUSIONS

In hospital practice, the mean dosages were consistent with the recommended loading and maintenance dosages for caspofungin and anidulafungin. Patients frequently received a loading dose of > 150 mg on day 1 of micafungin which was inconsistent with recommended dosing schedules. Micafungin maintenance dosages > 100 mg were also commonly used. Lack of information on reason for initiating echinocandin therapy was an important study limitation.

Synthesis of new 1-[2-Azido-2-(2,4-dichlorophenyl)ethyl]-1H/-imidazoles and in vitro evaluation of their antifungal activity

New 1-[2-azido-2-(2,4-dichlorophenyl)ethyl]-1H/-imidazole were synthesized by nucleophilic substitution of various tertiary alcohols with azide anion in presence of boron trifluoride-diethyl etherate. Their antifungal activity was evaluated against Candida albicans, Candida glabrata, Aspergillus fumigatus and an azole-resistant petite mutant of C. glabrata. Preliminary SAR results are discussed.

Two GDP-mannose transporters contribute to hyphal form and cell wall integrity in Aspergillus nidulans

In order to identify novel genes affecting cell wall integrity, we have generated mutant strains of the filamentous fungus Aspergillus nidulans that show hypersensitivity to the chitin-binding agent Calcofluor White (CFW). Affected loci are designated cal loci. The phenotype of one of these alleles, calI11, also includes shortened hyphal compartments and increased density of branching in the absence of CFW, as well as reduced staining of cell walls by the lectin FITC-Concanavalin A (ConA), which has strong binding affinity for mannosyl residues. We have identified two A. nidulans genes (AN8848.3 and AN9298.3, designated gmtA and gmtB, respectively) that complement all aspects of the phenotype. Both genes show strong sequence similarity to GDP-mannose transporters (GMTs) of Saccharomyces and other yeasts. Sequencing of gmtA from the calI11 mutant strain reveals a G to C mutation at position 943, resulting in a predicted alanine to proline substitution at amino acid position 315 within a region that is highly conserved among other fungi. No mutations were observed in the mutant strain's allele of gmtB. Meiotic mapping demonstrated a recombination frequency of under 1 % between the calI locus and the phenA locus (located approximately 9.5 kb from AN8848.3), confirming that gmtA and calI are identical. A GmtA-GFP chimera exhibits a punctate distribution pattern, consistent with that shown by putative Golgi markers in A. nidulans. However, this distribution did not overlap with that of the putative Golgi equivalent marker CopA-monomeric red fluorescent protein (mRFP), which may indicate that the physically separated Golgi-equivalent organelles of A. nidulans represent physiologically distinct counterparts of the stacked cisternae of plants and animals. These findings demonstrate that gmtA and gmtB play roles in cell wall metabolism in A. nidulans similar to those previously reported for GMTs in yeasts.

Natural products to drugs: natural product-derived compounds in clinical trials

Natural product and natural product-derived compounds that are being evaluated in clinical trials or are in registration (as at 31st December 2007) have been reviewed, as well as natural product-derived compounds for which clinical trials have been halted or discontinued since 2005. Also discussed are natural product-derived drugs launched since 2005, new natural product templates and late-stage development candidates.

The evolution of fungal drug resistance: modulating the trajectory from genotype to phenotype

The emergence of drug resistance in pathogenic microorganisms provides an excellent example of microbial evolution that has had profound consequences for human health. The widespread use of antimicrobial agents in medicine and agriculture exerts strong selection for the evolution of drug resistance. Selection acts on the phenotypic consequences of resistance mutations, which are influenced by the genetic variation in particular genomes. Recent studies have revealed a mechanism by which the molecular chaperone heat shock protein 90 (Hsp90) can alter the relationship between genotype and phenotype in an environmentally contingent manner, thereby 'sculpting' the course of evolution. Harnessing Hsp90 holds great promise for treating life-threatening infectious diseases.

Antifungal canthin-6-one series accumulate in lipid droplets and affect fatty acid metabolism in Saccharomyces cerevisiae

The mechanism of action of antifungal canthin-6-one series was investigated in Saccharomyces cerevisiae. After a rapid uptake, a preferential accumulation of the drug within lipid droplets was observed. The antifungal action of canthin-6-one was found as reversible. Canthin-6-one did not exhibit affinity for sterols, and membrane ergosterol was not necessary for the antifungal activity since the MICs were similar on an ergosterol-deleted and the wild-type S. cerevisiae clones. Relative amount of unsaturated alkyl chain fatty acids was significantly enhanced suggesting a stimulation of desaturase enzyme systems. No synergistic effect was observed between canthin-6-one and amphotericin B, ketoconazole and caspofungine. Canthin-6-one should now be evaluated in vivo against fungal pathogens.

Antifungal agents in neonates: issues and recommendations

Fungal infections are responsible for considerable morbidity and mortality in the neonatal period, particularly among premature neonates. Four classes of antifungal agents are commonly used in the treatment of fungal infections in pediatric patients: polyene macrolides, fluorinated pyrimidines, triazoles, and echinocandins. Due to the paucity of pediatric data, many recommendations for the use of antifungal agents in this population are derived from the experience in adults. The purpose of this article was to review the published data on fungal infections and antifungal agents, with a focus on neonatal patients, and to provide an overview of the differences in antifungal pharmacology in neonates compared with adults. Pharmacokinetic data suggest dosing differences in children versus adult patients with some antifungals, but not all agents have been fully evaluated. The available pharmacokinetic data on the amphotericin B deoxycholate formulation in neonates exhibit considerable variability; nevertheless, the dosage regimen suggested in the neonatal population is similar to that used in adults. More pharmacokinetic information is available on the liposomal and lipid complex preparations of amphotericin B and fluconazole, and it supports their use in neonates; however, the optimal dosage and duration of therapy is difficult to establish. All amphotericin-B formulations, frequently used in combination with flucytosine, are useful for treating disseminated fungal infections and Candida meningitis in neonates. Fluconazole, with potent in vitro activity against Cryptococcus neoformans and almost all Candida spp., has been used in neonates with invasive candidiasis at dosages of 6 mg/kg/day, and for antifungal prophylaxis in high-risk neonates. There are limited data on itraconazole, voriconazole, and posaconazole use in neonates. Caspofungin, which is active against Candida spp. and Aspergillus spp., requires higher doses in children relative to adults, and dosing is best accomplished based on body surface area. Micafungin shows a clear trend toward lower levels in the smallest patients. There are no data on the use of other new antifungal drugs (ravuconazole and anidulafungin) in neonates. In summary, the initial data suggest dosage differences in neonates for some antifungal agents, although the newer agents have not been fully tested for optimal administration in these patients.

Mother Nature's gifts to diseases of man: the impact of natural products on anti-infective, anticholestemics and anticancer drug discovery

This chapter is designed to demonstrate that compounds derived from nature are still in the forefront of drug discovery in diseases such as microbial and parasitic infections, carcinomas of many types and control of cholesterol/lipids in man. In each disease area we have provided short discussions of past, present and future agents, in general only considering compounds currently in clinical Phase II or later, that were/are derived from nature's chemical skeletons. Finishing with a discussion of the current and evolving role(s) of microbes (bacteria and fungi) in the production of old and new agents ostensibly produced by higher organisms.

Micafungin versus Caspofungin for Treatment of Candidemia and Other Forms of Invasive Candidiasis

BACKGROUND

Invasive candidiasis is an important cause of morbidity and mortality among patients with health care-associated infection. The echinocandins have potent fungicidal activity against most Candida species, but there are few data comparing the safety and efficacy of echinocandins in the treatment of invasive candidiasis.

METHODS

This was an international, randomized, double-blind trial comparing micafungin (100 mg daily) and micafungin (150 mg daily) with a standard dosage of caspofungin (70 mg followed by 50 mg daily) in adults with candidemia and other forms of invasive candidiasis. The primary end point was treatment success, defined as clinical and mycological success at the end of blinded intravenous therapy.

RESULTS

A total of 595 patients were randomized to one the treatment groups and received at least 1 dose of study drug. In the modified intent-to-treat population, 191 patients were assigned to the micafungin 100 mg group, 199 to the micafungin 150 mg group, and 188 to the caspofungin group. Demographic characteristics and underlying disorders were comparable across the groups. Approximately 85% of patients had candidemia; the remainder had noncandidemic invasive candidiasis. At the end of blinded intravenous therapy, treatment was considered successful for 76.4% of patients in the micafungin 100 mg group, 71.4% in the micafungin 150 mg group, and 72.3% in the caspofungin group. The median time to culture negativity was 2 days in the micafungin 100 mg group and the caspofungin group, compared with 3 days in the micafungin 150 mg groups. There were no significant differences in mortality, relapsing and emergent infections, or adverse events between the study arms.

CONCLUSIONS

Dosages of micafungin 100 mg daily and 150 mg daily were noninferior to a standard dosage of caspofungin for the treatment of candidemia and other forms of invasive candidiasis.

Anidulafungin: a new echinocandin for candidal infections

Anidulafungin, a new echinocandin, has recently been approved for the treatment of esophageal candidiasis, candidemia and other forms of invasive candidiasis, such as peritonitis and intra-abdominal abscesses in non-neutropenic patients. It is fungicidal against Candida spp. including those that are azole- and polyene-resistant and fungistatic against Aspergillus spp. Owing to its poor oral bioavailability it can only be administered intravenously. Its pharmacokinetics allow for once-daily dosing and a steady state concentration is easily achieved on day 2 following a loading dose of double the maintenance dose on day 1. It does not need adjustment for hepatic or renal insufficiency; there are no known drug interactions and it has a favorable tolerability profile. Its mechanism of action, which differs from other classes of antifungals, should prevent cross-resistance with azoles and polyenes.

Efficacy of aminocandin in the treatment of immunocompetent mice with haematogenously disseminated fluconazole-resistant candidiasis

OBJECTIVES

The objective of this study was to compare the activity of aminocandin, a new echinocandin with broad-spectrum activity against Candida spp., with that of amphotericin B, caspofungin and fluconazole, in an immunocompetent murine model of haematogenously disseminated candidiasis caused by a fluconazole-resistant Candida albicans.

METHODS

Mice were infected with a fluconazole-resistant strain of C. albicans and treated with aminocandin 5 and 10 mg/kg intravenously (iv) once and twice weekly, amphotericin B 0.5 mg/kg iv every other day for 5 days, fluconazole 20 mg/kg orally (po) once a day for 5 days and caspofungin 0.5 mg/kg intraperitoneally (ip) once daily for 5 days.

RESULTS

Treatment with aminocandin, given iv twice a week, resulted in 100% survival. Further, the tissue fungal burden of the aminocandin group was equivalent to that of amphotericin B (administered every other day) and caspofungin (administered daily).

CONCLUSIONS

Aminocandin may be an effective addition to the arsenal of antifungal compounds for the treatment of candidiasis caused by fluconazole-resistant C. albicans.

Nonribosomal cyclic peptides: specific markers of fungal infections

Some cyclic peptides and depsipeptides are synthesized in microorganisms by large multienzymes called nonribosomal peptide synthetases. The structures of peptide products originating in this way are complex and diverse and are microorganism-specific. This work proposes the use of fungal cyclic peptides and depsipeptides as extremely specific markers of fungal infections. Since a reliable molecular tool for diagnosing fungal infections at an early stage is still missing, we present mass spectrometry as a new, modern, broadband (with respect to fungal strain) and specific tool for clinical mycologists. More than 40 different fungal species can be rapidly characterized according to specific families of cyclic peptides, and in some cases, a particular fungal strain can be identified on the basis of its cyclopeptide profile. This paper is also aimed at initiating discussion on the biological role of these secondary metabolites, especially of those synthesized by medically important strains. Proven cytotoxic, anti-inflammatory or immunosuppressive activities of some cyclic peptides indicate that these molecules may contribute to the synergistic array of fungal virulence factors and support microbial invasion during fungal infection. In addition to an overview on recent mass spectrometric protocols for cyclic peptide sequencing, the structures of new peptides from Paecilomyces and Pseudallescheria are presented.