Host nutrition-based approach for biotechnological production of the antifungal cyclic lipopeptide jagaricin

In today's, society multi-resistant pathogens have become an emerging threat, which makes the search for novel anti-infectives more urgent than ever. A promising class of substances are cyclic lipopeptides like the antifungal jagaricin. Jagaricin is formed by the bacterial mushroom pathogen Janthinobacterium agaricidamnosum. It has shown antifungal activity against human pathogenic fungi like Candida albicans and Aspergillus fumigatus. In addition, jagaricin is nearly non-toxic for plants, which makes it a promising agent for agricultural applications. Cyclic lipopeptides formed by microorganisms originate from their secondary metabolism. This makes it very challenging to determine the inducing factor for product formation, especially for unknown microbial systems like J. agaricidamnosum. In the presented study, a biotechnological process for jagaricin formation was developed, investigating impact factors like the medium, oxygen availability, and phosphate. For this reason, experiments were conducted on microtiter plate, shake flask, and stirred tank bioreactor level. Ultimately, a final maximum jagaricin concentration of 251 mg L^-1 (15.5 mg_Jagaricin∙g_CDW^-1) could be achieved, which is an increase of approximately 458 % in comparison to previous results in standard glucose medium. This concentration allows the production of significantly higher amounts of jagaricin and enables further experiments to investigate the potential of this substance.

Micafungin Inhibits Dengue Virus Infection through the Disruption of Virus Binding, Entry, and Stability

Dengue fever is an arbovirus disease caused by infection with the dengue virus (DENV). Half of the world's population lives under the threat of dengue fever, however, researchers have yet to develop any drugs that are clinically applicable to this infection. Micafungin is a member of the echinocandins family of anti-fungal drugs, capable of blocking the synthesis of β-1,3-D-glucan in the walls of fungal cells. Previous studies have demonstrated the effectiveness of Micafungin against infections of enterovirus 71 (EV71) and chikungunya virus (CHIKV). This is the first study demonstrating the effectiveness of micafungin in inhibiting the cytopathic effects of dengue virus serotype 2 (DENV-2) in a dose-dependent manner. Time-of-addition assays verified the inhibitory effects of micafungin in pre-treated, co-treated, and full-treatment groups. Binding and entry assays also demonstrated the effectiveness of micafungin in the early stage of DENV-2 infection. The virucidal efficacy of micafungin appears to lie in its ability to destroy the virion. Molecular docking assays revealed the binding of micafungin to the envelope protein of DENV-2, thereby revealing the mechanism by which micafungin affects the early stage of DENV infection and the stability of DENV. Two other micafungin analogs, caspofungin and anidulafungin, were also shown to have the antiviral effects on DENV-2. Finally, immunofluorescence assay (IFA) and reverse-transcription quantitative polymerase chain reaction (RT-qPCR) confirmed the broad anti-DENV ability of micafungin against dengue virus serotypes 1, 3, and 4 (DENV-1, DENV-3, and DENV-4). Taken together, these results demonstrate the potential of micafungin and its analogs as candidates for the development of broad-spectrum treatments for DENV infection.

Use of micafungin as antifungal prophylaxis in patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT) in Spain (GETH-MIC)

Introduction

The fungal infections remain an important problem in the allogeneic stem cell trasnsplantation (allo-SCT) setting and thus, anti-fungal prophylaxis is commonly used. The antifungal drug should offer activity, at least against Candida and Aspergillus spp., a good safety profile and low probability interactions. Micafungin could theoretically fulfill these requisites. The aim of the study was to describe the experience with micafungin as primary prophylaxis in patients undergoing allo-SCT in a cohort of Spanish centres, and to evaluate its efficacy and tolerability in this population.

Material and methods

Retrospective multicentre observational study including all consecutive adult patients admitted for allo-SCT in participating centres of the Grupo Español de Trasplante Hematopoyético (GETH), from January 2010 to December 2013, who received micafungin as primary prophylaxis during the neutropenic period.

Results

A total of 240 patients from 13 centres were identified and 159 patients were included for the analysis. Most patients (95.6%) received 50 mg/day of micafungin. During the follow-up, 7 (4.4%) patients developed breakthrough invasive fungal disease, 1 proven and 6 probable; one patient discontinued the drug because of serious drug interactions. Prophylaxis with micafungin was considered effective in 151 (94.9%) patients.

Conclusions

According to our experience, micafungin is an appropriate alternative for antifungal prophylaxis in patients undergoing an allo-HSCT, because its efficacy, its low profile of drug interactions and side-effects.

Biguanides enhance antifungal activity against Candida glabrata

Candida spp. are the fourth leading cause of nosocomial blood stream infections in North America. Candida glabrata is the second most frequently isolated species, and rapid development of antifungal resistance has made treatment a challenge. In this study, we investigate the therapeutic potential of metformin, a biguanide with well-established action for diabetes, as an antifungal agent against C. glabrata. Both wild type and antifungal-resistant isolates of C. glabrata were subjected to biguanide and biguanide-antifungal combination treatment. Metformin, as well as other members of the biguanide family, were found to have antifungal activity against C. glabrata, with MIC₅₀ of 9.34 ± 0.16 mg/mL, 2.09 ± 0.04 mg/mL and 1.87 ± 0.05 mg/mL for metformin, phenformin and buformin, respectively. We demonstrate that biguanides enhance the activity of several antifungal drugs, including voriconazole, fluconazole, and amphotericin, but not micafungin. The biguanide-antifungal combinations allowed for additional antifungal effects, with fraction inhibition concentration indexes ranging from 0.5 to 1. Furthermore, metformin was able to lower antifungal MIC₅₀ in voriconazole and fluconazole-resistant clinical isolates of C. glabrata. We also observed growth reduction of C. glabrata with rapamycin and an FIC of 0.84 ± 0.09 when combined with metformin, suggesting biguanide action in C. glabrata may be related to inhibition of the mTOR complex. We conclude that the biguanide class has direct antifungal therapeutic potential and enhances the activity of select antifungals in the treatment of resistant C. glabrata isolates. These data support the further investigation of biguanides in the combination treatment of serious fungal infections.

Efficacy of micafungin for the treatment of invasive candidiasis and candidaemia in patients with neutropenia

Neutropenia is linked to the development of invasive candidiasis/candidaemia, for which micafungin has demonstrated efficacy, but evidence in patients with neutropenia is limited. The aim of this study was to evaluate the efficacy of micafungin for the treatment of invasive candidiasis/candidaemia in patients with neutropenia (<500 neutrophils/μL) and without neutropenia. This pooled, post hoc analysis of 2 Phase 3 trials compared micafungin 100 mg/d (adults) and 2 mg/kg/d (paediatrics) with L-AmB 3 mg/kg/d (NCT00106288) and micafungin 100 mg/d and 150 mg/d with caspofungin 70 mg/d followed by 50 mg/d (adults) (NCT00105144); treatment duration 2-4 weeks (≤8 weeks for chronic disseminated candidiasis). Effects of neutropenia duration and Candida spp. on efficacy outcomes (treatment success, clinical and mycological response) were examined. Of 685 patients, 77 had neutropenia. The most common infection in patients with/without neutropenia was due to C. tropicalis (31/77) and C. albicans (295/608) respectively. Overall success was numerically lower in patients with vs without neutropenia (63.6% vs 72.9%). Clinical and mycological response was similar between groups. Neutropenia duration or Candida spp. did not impact micafungin's overall success rate. This analysis supports evidence that micafungin is effective against invasive candidiasis/candidaemia in patients with neutropenia, irrespective of neutropenia duration or Candida spp., although overall success may be lower than in patients without neutropenia.

Antifungal Resistance in Dermatology

Cutaneous fungal infections affect more than one-fourth of world's population. The pathogenesis and severity of fungal infection depend on various immunological and nonimmunological factors. The rampant use of antifungal therapy in immunocompromised individuals marked the onset of antifungal drug resistance. Fungal resistance can be microbiological or clinical. Microbiological resistance depends on various fungal factors which have established due to genetic alteration in the fungi. Clinical resistance is due to host- or drug-related factors. All these factors may cause fungal resistance individually or in tandem. In addition to standardized susceptibility testing and appropriate drug dosing, one of the ways to avoid resistance is the use of combinational antifungal therapy. Combination therapy also offers advantages in increased synergistic action with enhanced spectrum activity. Newer insights into mechanisms of drug resistance will help in the development of appropriate antifungal therapy.

Micafungin: A Review in the Prophylaxis and Treatment of Invasive Candida Infections in Paediatric Patients

Intravenous micafungin (Mycamine^®; Funguard^®), an echinocandin, is approved in the EU for the treatment of invasive candidiasis in children (including neonates) and adolescents (<16 years of age) and as prophylaxis against Candida infections in patients undergoing haematopoietic stem cell transplantation (HSCT) or who are expected to have neutropenia for ≥10 days. This narrative review focuses on the use of micafungin in paediatric indications approved in the EU, which may vary from those approved elsewhere in the world. Micafungin has a broad spectrum of in vitro activity against clinically relevant isolates of Candida spp. (including fluconazole-resistant Candida glabrata isolates), a low propensity for emergence of resistant isolates and a convenient once-daily regimen. In paediatric substudies and a small multinational, phase 3 trial in neonates with proven invasive candidiasis, intravenous micafungin was effective and generally well tolerated in the treatment of candidaemia and other types of invasive candidiasis and as prophylaxis against fungal infections in patients undergoing HSCT. Hence, micafungin remains an important option for the prophylaxis and treatment of invasive Candida infections in paediatric and adult patients.

Structure-Activity Relationships of a Series of Echinocandins and the Discovery of CD101, a Highly Stable and Soluble Echinocandin with Distinctive Pharmacokinetic Properties

Echinocandins are a first-line therapy for candidemia and invasive candidiasis. They are generally safe with few drug interactions, but the stability and pharmacokinetic properties of currently approved echinocandins are such that each was developed for daily intravenous infusion. We sought to discover a novel echinocandin with properties that would enable more flexible dosing regimens, alternate routes of delivery, and expanded utility. Derivatives of known echinocandin scaffolds were generated, and an iterative process of design and screening led to the discovery of CD101, a novel echinocandin that has since demonstrated improved chemical stability and pharmacokinetics. Here, we report the structure-activity relationships (including preclinical efficacy and pharmacokinetic data) for the series of echinocandin analogs from which CD101 was selected. In a mouse model of disseminated candidiasis, the test compounds displayed clear dose responses and were generally associated with lower fungal burdens than that of anidulafungin. Single-dose pharmacokinetic studies in beagle dogs revealed a wide disparity in the half-lives and volumes of distribution, with one compound (now known as CD101) displaying a half-life that is nearly 5-fold longer than that of anidulafungin (53.1 h versus 11.6 h, respectively). In vitro activity data against panels of Candida spp. and Aspergillus spp. demonstrated that CD101 behaved similarly to approved echinocandins in terms of potency and spectrum of activity, suggesting that the improved efficacy observed in vivo for CD101 is a result of features beyond the antifungal potency inherent to the molecule. Factors that potentially contribute to the improved in vivo efficacy of CD101 are discussed.

CD101, a novel echinocandin with exceptional stability properties and enhanced aqueous solubility

The echinocandins are an important class of antifungal agents. However, instability and, in some cases, lack of solubility have restricted their use to situations in which daily infusions are acceptable. CD101 is a novel echinocandin in development for topical and weekly i.v. administration that exhibits prolonged stability in plasma and aqueous solutions up to 40 °C. After incubation for 44 h in rat, dog, monkey and human plasma at 37 °C, the percent of CD101 remaining (91%, 79%, 94% and 93%, respectively) was consistently greater than that of anidulafungin (7%, 15%, 14% and 7%, respectively). Similarly, after incubation in phosphate-buffered saline at 37 °C, the CD101 remaining (96%) was greater than that of anidulafungin (42%). CD101 exhibited <2% degradation after long-term storage at 40 °C as a lyophilized powder (9 months) and at room temperature in 5% dextrose (15 months), 0.9% saline (12 months) and sterile water (18 months). Degradation was <7% at 40 °C in acetate and lactate buffers (6 to 9 months at pH 4.5-5.5). The chemical stability and solubility of CD101 contribute to dosing, pharmacokinetic, formulation and safety advantages over other echinocandins and should expand utility beyond daily i.v.

THERAPY

Genomics-driven discovery of the pneumocandin biosynthetic gene cluster in the fungus Glarea lozoyensis

Background

The antifungal therapy caspofungin is a semi-synthetic derivative of pneumocandin B₀, a lipohexapeptide produced by the fungus Glarea lozoyensis, and was the first member of the echinocandin class approved for human therapy. The nonribosomal peptide synthetase (NRPS)-polyketide synthases (PKS) gene cluster responsible for pneumocandin biosynthesis from G. lozoyensis has not been elucidated to date. In this study, we report the elucidation of the pneumocandin biosynthetic gene cluster by whole genome sequencing of the G. lozoyensis wild-type strain ATCC 20868.

Results

The pneumocandin biosynthetic gene cluster contains a NRPS (GLNRPS4) and a PKS (GLPKS4) arranged in tandem, two cytochrome P450 monooxygenases, seven other modifying enzymes, and genes for L-homotyrosine biosynthesis, a component of the peptide core. Thus, the pneumocandin biosynthetic gene cluster is significantly more autonomous and organized than that of the recently characterized echinocandin B gene cluster. Disruption mutants of GLNRPS4 and GLPKS4 no longer produced the pneumocandins (A₀ and B₀), and the Δglnrps4 and Δglpks4 mutants lost antifungal activity against the human pathogenic fungus Candida albicans. In addition to pneumocandins, the G. lozoyensis genome encodes a rich repertoire of natural product-encoding genes including 24 PKSs, six NRPSs, five PKS-NRPS hybrids, two dimethylallyl tryptophan synthases, and 14 terpene synthases.

Conclusions

Characterization of the gene cluster provides a blueprint for engineering new pneumocandin derivatives with improved pharmacological properties. Whole genome estimation of the secondary metabolite-encoding genes from G. lozoyensis provides yet another example of the huge potential for drug discovery from natural products from the fungal kingdom.

[A liquid chromatographic method for quantifying unbound micafungin in human plasma and the relationship between the concentrations of unbound and total micafungin in plasma]

This report describes a modified method for the quantitative determination of unbound micafungin (MCFG) in human plasma that is unrelated to chemical methods currently in use, and the relationship between the concentration of unbound and total MCFG in plasma of the patients. The mobile phase consisted of 50 mM phosphate buffer:tetrahydrofuran (65:35, v/v). Samples were fractionated on a C-18 column. The fluorescence detection wavelengths of excitation and emission were set at 273 nm and 464 nm, respectively. The retention times of MCFG and 1-hydroxy-2-naphtoeic acid (internal standard: IS) were 10.5 min and 7.3 min, respectively. For each concentration of MCFG/IS, the peak height ratio on a 5-point calibration curve was linear from 0.004 to 0.08 μg/mL (r=0.999, p<0.001). In addition, the concentrations of unbound and total MCFG were measured in the plasma of 11 patients treated with MCFG for fungal infection. In total, 99 samples were collected. The concentration of unbound and total MCFG in plasma correlated with one another (r=0.896, p<0.001). These concentrations were not affected by serum albumin, total bilirubin, blood urea nitrogen, or creatinine clearance. There were small differences of [fu (unbound MCFG/total MCFG)×100%] in the every term after start of treatment of MCFG. Further, there was no difference in the unbound and total concentration of MCFG in plasma between the effective group and the ascertained effectiveness group. The concentration of MCFG in plasma could be used as an indicator of clinical effect as a substitute for the concentration of unbound MCFG in plasma.

Current perspectives on echinocandin class drugs

It has been nearly a decade since caspofungin was approved for clinical use as the first echinocandin class antifungal agent, followed by micafungin and anidulafungin. The echinocandin drugs target the fungal cell wall by inhibiting the synthesis of β-1,3-D-glucan, a critical cell wall component of many pathogenic fungi. They are fungicidal for Candida spp. and fungistatic for moulds, such as Aspergillus fumigatus, where they induce abnormal morphology and growth properties. The echinocandins have a limited antifungal spectrum but are highly active against most Candida spp., including azole-resistant strains and biofilms. As they target glucan synthase, an enzyme absent in mammalian cells, the echinocandins have a favorable safety profile. They show potent MIC and epidemiological cutoff values against susceptible Candida and Aspergillus isolates, and the frequency of resistance is low. When clinical breakthrough occurs, it is associated with high MIC values and mutations in Fks subunits of glucan synthase, which can reduce the sensitivity of the enzyme to the drug by several thousand-fold. Such strains were not adequately captured by an early clinical breakpoint for susceptibility prompting a revised lower value, which addresses the FKS resistance mechanism and new pharmacokinetic/pharmacodynamic studies. Elevated MIC values unlinked to therapeutic failure can occur and result from adaptive cell behavior, which is FKS-independent and involves the molecular chaperone Hsp90 and the calcineurin pathway. Mutations in FKS1 and/or FKS2 alter the kinetic properties of glucan synthase, which reduces the relative fitness of mutant strains causing them to be less pathogenic. The echinocandin drugs also modify the cell wall architecture exposing buried glucans, which in turn induce a variety of important host immune responses. Finally, the future for glucan synthase inhibitors looks bright with the development of new orally active compounds.

[Liver toxicity of micafungin. Is this drug safe?]

Micafungin was commercialized in Japan in 2002 and has been used in more than 750,000 patients. As a member of the candin family, the drug's clinical and analytical tolerability is very good, both in adults and in children, including neonates. In this latter population, micafungin is the most frequently used candin. The most common adverse effects are nausea and elevated transaminase levels. Preclinical studies showed the development of benign liver tumors in rats treated with extremely high doses of the drug for prolonged periods. These data were not reproduced in other species and no cases have been reported in humans.

[Scientific evidence supporting the use of micafungin in the treatment of invasive candidiasis]

Micafungin is a semisynthetic lipopeptide developed from Coleophoma empetri, which blocks the synthesis of β-1,3-D-glucan, an essential component of the fungal wall, though non-competitive inhibition of β-1,3-D-glucan synthetase. Micafungin is a dose-dependent candidacidal agent with excellent in vitro efficacy against most Candida spp. including species resistant to amphotericin B, such as Candida lusitaniae, several azoles, such as C. glabrata or C. krusei, and isolates not susceptible to other echinocandins. Moreover, this drug is active against Candida biofilms. Micafungin is a first-line drug for the treatment of candidemias and invasive candidiasis in adults and children (including neonates). This drug is approved for use in the treatment of invasive candidiasis and Candida esophagitis, as well as in the prophylaxis of Candida infections in hematopoietic stem cell transplant recipients or those at risk of prolonged neutropenia. Micafungin can be used both in the treatment and prevention of candidiasis in neonates, children, adolescents, adults, and the elderly, making it highly useful in patient groups in which the use of other antifungal drugs has not been authorized.

Distribution of micafungin in the tissue fluids of patients with invasive fungal infections

The distribution of micafungin (MCFG) in tissue fluids, such as cerebrospinal fluid (CSF), pleural effusions, ascites, and wound tissue fluids, was examined in seven patients with invasive fungal infections. MCFG (100-300 mg) was administered once daily over a 1-h intravenous infusion. Blood and tissue fluid samples were collected from 1 to 24 h after infusion. Although two patients had similar MCFG concentrations in their plasma, the concentrations in the CSF differed between these two patients. The concentration in the CSF of one patient was much higher than the MIC(90) for Candida albicans, Candida glabrata, and Aspergillus fumigatus, whereas the MCFG concentration in the CSF of the other patient was comparable to the MIC(90). By contrast, MCFG concentrations in pleural effusions, ascites, and wound tissue fluids were above the MIC(90). These results suggest that intravenous MCFG may be effective to treat invasive fungal infections that invade the organs and tissues.

Interactions between antifungal and antiretroviral agents

IMPORTANCE OF THE FIELD

Since the advent of combination antiretroviral therapy, the incidence of opportunistic infections has declined and the life expectancy of HIV-infected people has significantly increased. However, opportunistic infections, including fungal diseases, remain a leading cause of hospitalizations and mortality in HIV-infected people. With the availability of several new antiretroviral and antifungal agents, drug-drug interactions emerge as a potential safety concern.

AREAS COVERED IN THIS REVIEW

Relevant literature was identified using a Medline search of articles published up to March 2010 and a review of conference abstracts. Search terms included HIV, antifungal agents and drug interactions. Original papers and relevant citations were considered for this review.

WHAT THE READER WILL GAIN

Readers will gain an understanding of the pharmacokinetic properties of antiretroviral and antifungal agents, and insight into significant drug-drug interactions which may require dosage adjustments or a change in therapy.

TAKE HOME MESSAGE

Azole antifungal drugs, with the exception of fluconazole, pose the greatest risk of two-way interactions with antiretroviral drugs through CYP450 enzymes effects. Limited studies suggest the risk of interactions between antiretroviral drugs and echinocandins is much lower. The combination of tenofovir and amphotericin B should be used with caution and close monitoring of renal function is required.

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.

Micafungin: a review of its use in the prophylaxis and treatment of invasive Candida infections in pediatric patients

Intravenous micafungin (Mycamine; Funguard) is an echinocandin indicated in Japan and the EU for the treatment of pediatric patients (including neonates) with invasive candidiasis and as prophylaxis against Candida infection in pediatric patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT). In the EU, micafungin is also indicated in pediatric patients who are expected to have neutropenia for >/=10 days. In Japan, children may also receive micafungin for the treatment of, or as prophylaxis against, invasive Aspergillus infection. Micafungin is not currently approved for use in pediatric patients in the US. Micafungin has very good antifungal activity against a wide range of Candida spp. in vitro. It has a favorable pharmacokinetic profile allowing for once-daily administration, has few drug-drug interactions, and reports of resistance are rare. The results of pediatric substudies indicate that intravenous micafungin is effective in a majority of patients for the treatment of candidemia and other types of invasive candidiasis, and provides effective prophylaxis against invasive fungal infections in pediatric patients undergoing HSCT. The tolerability profile of micafungin in pediatric patients was generally acceptable. In the EU, micafungin is indicated for use when other antifungal medications are not appropriate. Therefore, micafungin provides an alternative to other antifungal agents used in the management of candidemia and invasive candidiasis in pediatric patients, or as prophylaxis against fungal infections in pediatric patients undergoing HSCT.

Liposomal amphotericin B: a review of its use as empirical therapy in febrile neutropenia and in the treatment of invasive fungal infections

Liposomal amphotericin B (AmBisome) is a lipid-associated formulation of the broad-spectrum polyene antifungal agent amphotericin B. It is active against clinically relevant yeasts and moulds, including Candida spp., Aspergillus spp. and filamentous moulds such as Zygomycetes, and is approved for the treatment of invasive fungal infections in many countries worldwide. It was developed to improve the tolerability profile of amphotericin B deoxycholate, which was for many decades considered the gold standard of antifungal treatment, despite being associated with infusion-related events and nephrotoxicity. In well controlled trials, liposomal amphotericin B had similar efficacy to amphotericin B deoxycholate and amphotericin B lipid complex as empirical therapy in adult and paediatric patients with febrile neutropenia. In addition, caspofungin was noninferior to liposomal amphotericin B as empirical therapy in adult patients with febrile neutropenia. For the treatment of confirmed invasive fungal infections, liposomal amphotericin B was more effective than amphotericin B deoxycholate treatment in patients with disseminated histoplasmosis and AIDS, and was noninferior to amphotericin B deoxycholate in patients with acute cryptococcal meningitis and AIDS. In adults, micafungin was shown to be noninferior to liposomal amphotericin B for the treatment of candidaemia and invasive candidiasis. Data from animal studies suggested that higher dosages of liposomal amphotericin B might improve efficacy; however, in the AmBiLoad trial in patients with invasive mould infection, there was no statistical difference in efficacy between the standard dosage of liposomal amphotericin B 3 mg/kg/day and a higher 10 mg/kg/day dosage, although the standard dosage was better tolerated. Despite being associated with fewer infusion-related adverse events and less nephrotoxicity than amphotericin B deoxycholate and amphotericin B lipid complex, liposomal amphotericin B use is still limited to some extent by these adverse events. Both echinocandins were better tolerated than liposomal amphotericin B. The cost of liposomal amphotericin B therapy may also restrict its use, but further pharmacoeconomic studies are required to fully define its cost effectiveness compared with other antifungal agents. Based on comparative data from well controlled trials, extensive clinical experience and its broad spectrum of activity, liposomal amphotericin B remains a first-line option for empirical therapy in patients with febrile neutropenia and in those with disseminated histoplasmosis, and is an option for the treatment of AIDS-associated cryptococcal meningitis, and for invasive Candida spp. or Aspergillus spp. infections. Amphotericin B, a macrocyclic, polyene antifungal agent, is thought to act by binding to ergosterol, the principal sterol in fungal cell membranes and Leishmania cells. This results in a change in membrane permeability, causing metabolic disturbance, leakage of small molecules and, as a consequence, cell death. In vitro and in vivo studies have shown that liposomal amphotericin B remains closely associated with the liposomes in the circulation, thereby reducing the potential for nephrotoxicity and infusion-related toxicity associated with conventional amphotericin B. Amphotericin B shows very good in vitro activity against a broad spectrum of clinically relevant fungal isolates, including most strains of Candida spp. and Aspergillus spp., and other filamentous fungi such as Zygomycetes. Liposomal amphotericin B has proven effective in various animal models of fungal infections, including those for candidiasis, aspergillosis, fusariosis and zygomycosis. Liposomal amphotericin B also shows immunomodulatory effects, although the mechanisms involved are not fully understood, and differ from those of amphotericin B deoxycholate and amphotericin B colloidal dispersion. In adult patients with febrile neutropenia, intravenous liposomal amphotericin B has nonlinear pharmacokinetics, with higher than dose-proportional increases in exposure being consistent with reticuloendothelial saturation and redistribution of amphotericin B in the plasma compartment. Liposomal amphotericin B is rapidly and extensively distributed after single and multiple doses, with steady-state concentrations of amphotericin B attained within 4 days and no clinically relevant accumulation of the drug following multiple doses of 1-7.5 mg/kg/day. In autopsy tissue, the highest concentrations of the drug were found in the liver and spleen, followed by the kidney, lung, myocardium and brain tissue. Elimination of liposomal amphotericin B, like that of amphotericin B deoxycholate, is poorly understood; its route of metabolism is not known and its excretion has not been studied. The terminal elimination half-life is about 7 hours. No dosage adjustment is required based on age or renal impairment. In several randomized, double-blind trials (n = 73-1095) in adult and/or paediatric patients, liposomal amphotericin B was effective as empirical therapy or as treatment for confirmed invasive fungal infections, including invasive candidiasis, candidaemia, invasive mould infection (mainly aspergillosis), histoplasmosis and cryptococcal meningitis. All agents were administered as an intravenous infusion; the typical dosage for liposomal amphotericin B was 3 mg/kg/day. Treatment was generally given for 1-2 weeks. Participants in trials evaluating empirical therapy had neutropenia and a persistent fever despite antibacterial treatment and had received chemotherapy or undergone haematopoietic stem cell transplantation. As empirical therapy in adult and paediatric patients, liposomal amphotericin B appeared to be as effective as amphotericin B deoxycholate (approximately 50% of patients in each group achieved treatment success) or amphotericin B lipid complex (approximately 40% of liposomal amphotericin B recipients experienced treatment success). Of note, in the first trial, results of the statistical test to determine equivalence between treatments were not reported. In the second trial, efficacy was assessed as an 'other' endpoint. In another trial, caspofungin was shown to be noninferior to liposomal amphotericin B, with approximately one-third of patients in each group experiencing treatment success. Liposomal amphotericin B was significantly more effective than amphotericin B deoxycholate for the treatment of moderate to severe disseminated histoplasmosis in patients with AIDS, with 88% and 64% of patients, respectively, having a successful response. Liposomal amphotericin B was noninferior to amphotericin B deoxycholate for the treatment of cryptococcal meningitis in terms of mycological success. Micafungin therapy was shown to be noninferior to liposomal amphotericin B for the treatment of adult patients with candidaemia or invasive candidiasis. In a substudy in paediatric patients, which was not powered to determine noninferiority, liposomal amphotericin B was as effective as micafungin for the treatment of candidaemia or invasive candidiasis. In this patient population, within each trial, 90% of adult patients and approximately three-quarters of paediatric patients in both treatment groups experienced a successful response. In patients with invasive mould infection (mainly aspergillosis), there was no difference in efficacy between a higher dosage of liposomal amphotericin B (10 mg/kg/day) and the standard dosage (3 mg/kg/day), with 46% and 50% of patients experiencing a favourable overall response. In well designed clinical trials, liposomal amphotericin B was generally at least as well tolerated as other lipid-associated formulations of amphotericin B and better tolerated than amphotericin B deoxycholate in adult and paediatric patients. Compared with other amphotericin B formulations, liposomal amphotericin B treatment was associated with a lower incidence of infusion-related adverse events and nephrotoxicity. A higher than recommended dosage of liposomal amphotericin B (10 mg/kg/day) was associated with an increased incidence of nephrotoxicity compared with the standard dosage (3 mg/kg/day), although the incidence of infusion-related reactions did not differ between treatment groups. In general, liposomal amphotericin B treatment was not as well tolerated as echinocandin therapy in well designed clinical trials. As empirical therapy or for the treatment of confirmed invasive fungal infections in adult patients, liposomal amphotericin B recipients experienced more infusion-related events and nephrotoxicity than caspofungin or micafungin recipients. There was no difference in the incidence of these adverse events between the liposomal amphotericin B and micafungin groups in a study in paediatric patients.

[Future role of micafungin in the treatment of invasive mycoses caused by filamentous fungi]

BACKGROUND

Micafungin is a echinocandin. It inhibits beta-1,3-D-glucan synthesis, thus achieving fungicidal activity against virtually all Candida spp., including those resistant to fluconazole, and fungistatic activity against Aspergillus spp., as well as several but not all pathogenic molds. Results from in vitro studies, animal models, small clinical trials, hint at possible future indications such as invasive aspergillosis and empirical viantifungal therapy, although currently there is little information published.

AIMS

To describe published data of micafungin as treatment against invasive mold infections, specially analysing its role in the inmunodepressed host and critical care setting.

METHODS

A systematic review of literature using the principal medical search engines was performed. Terms such as micafungin, aspergillosis, zygomycosis, invasive fungal infections, emerging fungal infections, antifungal treatment or therapy, antifungal prophylaxis, empiric or pre-emptive therapy were crossed. Febrile neutropenia patients were excluded.

RESULTS

Several studies in these setting were identified and were described in this review. Although there were no blinded randomized clinical trials published, treatment or prophylaxis of invasive aspergillosis and other invasive mould infections with micafungin described in open clinical studies were analyzed.

CONCLUSIONS

Micafungin could play a future important role as a primary or rescue therapy, alone or in combination, in the treatment or prophylaxis of invasive fungal infections caused by moulds. New randomized clinical trials are needed to confirm their efficacy.