Comparison of echinocandin antifungals

[Persistent candidemia in a renal-pancreatic transplant patient]

BACKGROUND

In recent decades, there has been an increase in the survival of recipients of solid organ transplants related to the improvement of the surgical technique, the introduction of protocols for immunosuppressive therapy, and the use of antimicrobial prophylaxis. Nonetheless, invasive fungal infection (IFI) is currently the major cause of morbidity and mortality in this group of patients. Invasive candidiasis is the most common IFI found after renal transplantation and is usually associated with total parenteral nutrition, broad-spectrum antibiotic therapy and abdominal surgery.

CLINICAL CASE

We report the case of a recent kidney-pancreas transplant recipient who developed a persistent catheter-related candidemia caused by Candida glabrata. The patient was treated with anidulafungin and had a good clinical course with no significant drug interactions. We discuss the possible causes and diagnostic and therapeutic alternatives of this kind of infection.

Chemosensitization as a means to augment commercial antifungal agents

Antimycotic chemosensitization and its mode of action are of growing interest. Currently, use of antifungal agents in agriculture and medicine has a number of obstacles. Foremost of these is development of resistance or cross-resistance to one or more antifungal agents. The generally high expense and negative impact, or side effects, associated with antifungal agents are two further issues of concern. Collectively, these problems are exacerbated by efforts to control resistant strains, which can evolve into a treadmill of higher dosages for longer periods. This cycle in turn, inflates cost of treatment, dramatically. A further problem is stagnation in development of new and effective antifungal agents, especially for treatment of human mycoses. Efforts to overcome some of these issues have involved using combinations of available antimycotics (e.g., combination therapy for invasive mycoses). However, this approach has had inconsistent success and is often associated with a marked increase in negative side effects. Chemosensitization by natural compounds to increase effectiveness of commercial antimycotics is a somewhat new approach to dealing with the aforementioned problems. The potential for safe natural products to improve antifungal activity has been observed for over three decades. Chemosensitizing agents possess antifungal activity, but at insufficient levels to serve as antimycotics, alone. Their main function is to disrupt fungal stress response, destabilize the structural integrity of cellular and vacuolar membranes or stimulate production of reactive oxygen species, augmenting oxidative stress and apoptosis. Use of safe chemosensitizing agents has potential benefit to both agriculture and medicine. When co-applied with a commercial antifungal agent, an additive or synergistic interaction may occur, augmenting antifungal efficacy. This augmentation, in turn, lowers effective dosages, costs, negative side effects and, in some cases, countermands resistance.

Fungal infections: their diagnosis and treatment in transplant recipients

Systemic fungal infections typically occur in individuals who are seriously ill with recognized risk factors such as those frequently found in transplant recipients. Unfortunately, they are often diagnosed late, when the efficacy of the available treatments is low, often less than 50%, and the cost in terms of lives lost, hospital length of stay, and total hospital costs is substantially increased. The application of antifungal therapies associated with reported efficacy rates greater than 50% are those used prophylactically. When used prophylactically, these infections are reduced in greater than 95% of the expected cases. The choice of a prophylactic agent should be based upon its ease of administration, lack of adverse effects, reduced likelihood of potential drug interactions, and its efficacy in patients with established risk factors and comorbid disease processes that include renal, hepatic, and chronic pulmonary disease. The indications for the use of currently available antifungal agents, their adverse effects, drug interactions, ease of dosing, and applicability in patients with preexisting disease states, and especially in liver transplant recipients, are presented in this paper.

An on-line solid phase extraction procedure for the routine quantification of caspofungin by liquid chromatography-tandem mass spectrometry

BACKGROUND

Extensive sets of data are required to investigate the potential use of a therapeutic drug monitoring with individualization of dosage of the antimycotic compound caspofungin. The goal was to develop an improved liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for this aim.

METHODS

Following protein precipitation, on-line solid phase extraction was performed for sample preparation. As the internal standard compound the veterinary drug tylosin was used. A standard validation protocol was applied.

RESULTS

Good reproducibility and accuracy of the method were observed. On-line solid phase extraction resulted in a convenient work-flow and good robustness of the method.

CONCLUSIONS

This improved LC-MS/MS method was found reliable and convenient. It can be suggested for further work on the clinical pharmacology of caspofungin in the setting of clinical research laboratories.

Anidulafungin: is it a promising option in the treatment of pediatric invasive fungal infections?

Cases of invasive fungal infections are increasing globally due to an increase in the immunosuppressed population, the use of broad-spectrum antibiotics and the invasive instrumentation of patients in intensive care units. Ongoing emergence of resistance and problems with toxicity have resulted in the need for the development of new antifungal agents. Anidulafungin, the most recently developed echinocandin, is approved by the US FDA for treatment of candidemia, other forms of Candida infection and esophageal candidiasis in non-neutropenic adult patients, but it is not currently licensed for pediatric usage. The drug is projected to be distinctive owing to its unique pharmacokinetics and is already listed in adult antifungal treatment guidelines. In this article, anidulafungin will be reviewed with a focus on pediatric patients.

Anidulafungin: Review of its Role in the Treatment of Invasive Candidiasis

In 2006 a third echinocandin, anidulafungin, was approved in the USA for the treatment of candida esophagitis, candidemia, and invasive candida infections such as intra-abdominal abscesses and peritonitis in the non-neutropenic patient. Two years later it was approved in the EU for invasive candidiasis in non-neutropenic patients. Like other echinocandins, it is fungicidal against Candida species and fungistatic against Aspergillus species. It does not need adjustment for renal or hepatic insufficiency, and has no known drug interactions. Its administration is by the intravenous route only, and it is well tolerated. A steady state concentration can be achieved on day two by giving twice the maintenance dose on day one.

Treatment and prophylaxis of invasive candidiasis with anidulafungin, caspofungin and micafungin:review of the literature

Working by a distinct cell wall-specific mechanism of action, the echinocandin class of antifungals has substantially expanded the range of available treatments for invasive Candida infections. Anidulafungin, caspofungin and micafungin were investigated versus drugs from earlier antifungal classes in large clinical trials that demonstrated their excellent clinical and microbiological efficacy in the primary treatment of invasive candidiasis. Therefore, and supported by a number of favourable pharmacological characteristics, the echinocandins rapidly became established in guidelines and clinical practice as primary treatment options for moderately to severely ill patients with invasive candidiasis. This article reviews the relevant clinical evidence that forms the basis for the use of echinocandins in the management of invasive candidiasis, and discusses their current role in the context of recent guideline recommendations and treatment optimization strategies.

Comparative in vitro susceptibility of clinical isolates of Candida paparsilosis complex and other Candida species to caspofungin and anidulafungin by Etest

In vitro susceptibility of 141 clinical isolates of Candida species to caspofungin and anidulafungin is reported. the Etest was performed according to recommended procedure and minimum inhibitory concentrations (MICs) were read after 24 h of incubation at 35 °C. Applying a breakpoint of <2 mg/ml, all Candida spp. isolates, except those belonging to C. parapsilosis complex, were susceptible. The geometric mean for caspofungin and anidulafungin for different Candida spp. were as follows: Candida parapsilosis, 0.438 and 3.355 μg/ml; Candida orthopsilosis, 0.210 and 1.456 μg/ml; Candida albicans, 0.049 and 0.007 μg/ml; Candida dubliniensis, 0.077 and 0.009 μg/ml; Candida tropicalis, 0.061 and 0.027 μg/ml; Candida glabrata, 0.120 and 0.032 μg/ml; and Candida krusei, 0.288 and 0.052 μg/ml, respectively. Anidulafungin was significantly more active than caspofungin (p <0.001) except for C. parapsilosis complex spp. isolates. In conclusion, our Etest MICs compared well with epidemiological cutoff values derived from a large number of Candida spp. isolates tested by CLSI method in previous studies. However, considering the differences in MICs of the two echinocandins for C. parapsilosis complex isolates, the Etest needs further evaluation for its suitability.

Paradoxical effect of caspofungin against Candida bloodstream isolates is mediated by multiple pathways but eliminated in human serum

Paradoxical growth of Candida in vitro at echinocandin concentrations exceeding the MIC is well described, but the clinical relevance is unknown. We assessed echinocandin paradoxical effects against Candida bloodstream isolates (BSI) in the presence or absence of human serum and investigated regulatory mechanisms. As determined by broth microdilution, a paradoxical effect was evident for 60% (18/30), 23% (7/30), and 13% (4/30) of Candida albicans BSI exposed to caspofungin, anidulafungin, and micafungin, respectively, at achievable human serum concentrations (≤8 μg/ml). A paradoxical effect was not evident among 34 C. glabrata BSI and was observed only for caspofungin against C. parapsilosis (4%, 1/23). As determined in time-kill studies, a caspofungin paradoxical effect was demonstrated by C. albicans (2/3), C. glabrata (1/3), and C. parapsilosis (1/3), including BSI that were determined to be negative by microdilution. In 50% human serum, a paradoxical effect was eliminated at caspofungin concentrations up to 64 μg/ml for 100% (8/8) of the C. albicans BSI. A caspofungin paradoxical effect was also eliminated by chitin synthase inhibitor nikkomycin Z and at achievable concentrations of calcineurin pathway inhibitors, tacrolimus and cyclosporine. Moreover, these agents were synergistic with caspofungin against 100, 100, and 88% (7/8) of C. albicans, respectively, and exerted their own paradoxical effects. Finally, paradoxical growth was eliminated in C. albicans irs4- and inp51-null mutants, which lack phosphatidylinositol-(4,5)-bisphosphate 5'-phosphatase. Our findings suggest that the paradoxical effect is unlikely to be important in vivo but remains an important tool to study cell wall stress responses. We implicate the Irs4-Inp51 phosphatidylinositol-(4,5)-bisphosphate 5'-phosphatase as a novel regulator of paradoxical growth.

Pharmacokinetics, antifungal activity and clinical efficacy of anidulafungin in the treatment of fungal infections

IMPORTANCE OF THE FIELD

Anidulafungin is one of three available intravenous echinocandins that plays an important role in the treatment of serious fungal infections. Currently, anidulafungin is approved for the treatment of esophageal candidiasis, candidemia and other invasive Candida infections including intra-abdominal abscesses and peritonitis.

AREAS COVERED IN THIS REVIEW

This paper covers a comprehensive review of anidulafungin.

WHAT THE READER WILL GAIN

The reader will be provided the most recent data available regarding the pharmacology, pharmacokinetics, in vitro activity and clinical utility of anidulafungin for the treatment of serious fungal infections.

TAKE HOME MESSAGE

Echinocandin antifungals, such as anidulafungin, are now considered first line for the treatment of candidemia and invasive candidiasis, particularly in critically ill patients or those who have previously received azole therapy. Anidulafungin has potent in vitro activity against Candida and Aspergillus species, predictable pharmacokinetics that does not require dosage adjustment, few drug interactions and is well tolerated. Because of these favorable characteristics, anidulafungin is an important addition to our antifungal armamentarium.

Differential activities of three families of specific beta(1,3)glucan synthase inhibitors in wild-type and resistant strains of fission yeast

Three specific β(1,3)glucan synthase (GS) inhibitor families, papulacandins, acidic terpenoids, and echinocandins, have been analyzed in Schizosaccharomyces pombe wild-type and papulacandin-resistant cells and GS activities. Papulacandin and enfumafungin produced similar in vivo effects, different from that of echinocandins. Also, papulacandin was the strongest in vitro GS inhibitor (IC(50) 10(3)-10(4)-fold lower than with enfumafungin or pneumocandin), but caspofungin was by far the most efficient antifungal because of the following. 1) It was the only drug that affected resistant cells (minimal inhibitory concentration close to that of the wild type). 2) It was a strong inhibitor of wild-type GS (IC(50) close to that of papulacandin). 3) It was the best inhibitor of mutant GS. Moreover, caspofungin showed a special effect for two GS inhibition activities, of high and low affinity, separated by 2 log orders, with no increase in inhibition. pbr1-8 and pbr1-6 resistances are due to single substitutions in the essential Bgs4 GS, located close to the resistance hot spot 1 region described in Saccharomyces and Candida Fks mutants. Bgs4(pbr)(1-8) contains the E700V change, four residues N-terminal from hot spot 1 defining a larger resistance hot spot 1-1 of 13 amino acids. Bgs4(pbr)(1-6) contains the W760S substitution, defining a new resistance hot spot 1-2. We observed spontaneous revertants of the spherical pbr1-6 phenotype and found that an additional A914V change is involved in the recovery of the wild-type cell shape, but it maintains the resistance phenotype. A better understanding of the mechanism of action of the antifungals available should help to improve their activity and to identify new antifungal targets.

Differential Aspergillus lentulus echinocandin susceptibilities are Fksp independent

The recently described species Aspergillus lentulus exhibits differential and reduced susceptibilities to echinocandins and other antifungal drugs in vitro. A. lentulus isolates overall are less susceptible to caspofungin, although they maintain susceptibility to anidulafungin and micafungin. Mutations or polymorphisms in fks, the gene encoding the catalytic subunit of β-1,3-glucan synthase, are known to confer decreased susceptibility to echinocandins in Candida spp. and Aspergillus fumigatus. The analysis of the A. lentulus fks sequence did not reveal a polymorphism at any of the known hot-spot regions of the gene. Caspofungin and micafungin kinetic inhibition profiles of the A. lentulus glucan synthase were comparable to those from susceptible A. fumigatus enzymes. Although the basal cell wall chitin levels in A. lentulus averaged 60% of those in A. fumigatus, echinocandin treatment promoted the increase of cell wall chitin in both organisms, indicating that A. lentulus displays a compensatory chitin response similar to that of A. fumigatus. The data suggest that differential echinocandin susceptibilities in A. lentulus are independent of the echinocandin target, Fksp, and they emphasize the potential that the drugs' capacity to inhibit the target enzyme is unequal at the cellular level.

New triazoles and echinocandins: mode of action, in vitro activity and mechanisms of resistance

Different types of mycoses, especially invasive mycoses caused by yeasts and molds, are a growing problem in healthcare. The most notable explanation for this increase is a rise in the number of immunocompromised patients owing to advances in transplantation, the emergence of AIDS and a rise in the number of invasive surgical procedures. Despite advances in medical practice, some therapeutic problems remain. In addition, intrinsic or acquired antifungal resistance may pose a serious problem to antifungal therapy. A new generation of triazole agents (voriconazole, posaconazole, isavuconazole, ravuconazole and albaconazole) and the recent class of the echinocandins (caspofungin, micafungin and anidulafungin) have become available, and represent an alternative to conventional antifungals for serious fungal infection management. Currently, only two of the recent triazole generation (voriconazole and posaconazole) and all three echinocandins are available for clinical use. More precisely, voriconazole and posaconazole are indicated for the treatment of invasive fungal infections and the echinocandins for the treatment of specific candidiasis. Voriconazole and posaconazole have a very broad spectrum of antifungal activity that includes Candida species, and filamentous and dimorphic fungi. Their activity extends to both fluconazole- and itraconazole-resistant strains of Candida. A major difference between posaconazole and voriconazole is that posaconazole has activity against Zygomycetes including Mucor spp., Rhizopus spp. and Cunninghamella spp., and voriconazole has no activity against this class of fungi. Ravuconazole, isavuconazole and albaconazole have shown very potent in vitro activity against species of Candida, Cryptococcus and Aspergillus, and they are currently in various stages of development. All three echinocandin agents, caspofungin, micafungin and anidulafungin, are similar in their spectrum of activity. Echinocandins do not possess in vitro activity against important basidiomycetes, including Cryptococcus, Rhodotorula and Trichosporon. This review attempts to deliver the most up-to-date knowledge on the mode of action and mechanisms of resistance to triazoles and echinocandins in fungal pathogens. In addition, the in vitro activity data available on triazoles and echinocandins are reported.

Overview of the changing epidemiology of candidemia

Candida spp. are currently the fourth most common cause of bloodstream infections in US hospitals, and the third most common cause of bloodstream infections in the intensive care unit. Over the last 2 decades there has been a shift towards a greater involvement of non-Candida albicans spp. as the cause of candidemia. Several of these non-albicans spp. (e.g., C. glabrata and C. krusei ) exhibit resistance to traditional triazole antifungals like fluconazole, and cross-resistance with newer triazoles, focusing attention on the first-line use of antifungals such as the echinocandins, which possess improved activity against fluconazole-resistant strains. Recent treatment guidelines from the Infectious Diseases Society of America (IDSA) recommend an echinocandin as primary therapy for nonneutropenic or neutropenic patients with moderately severe to severe candidiasis and for patients at risk for infection with a triazole-resistant strain. However, further improvement in candidemia-associated mortality will only be attainable with the development and validation of new diagnostic tools that will allow earlier detection, discrimination, and treatment of invasive candidiasis. Clinicians should remain vigilant to wider emergence of Candida spp. with echinocandin resistance.

[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.

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.