Successful treatment of oesophageal candidiasis by micafungin: a novel systemic antifungal agent

Echinocandins in antifungal pharmacotherapy

Objectives

Echinocandins are the newest addition of the last decade to the antifungal armamentarium, which, owing to their unique mechanism of action, selectively target the fungal cells without affecting mammalian cells. Since the time of their introduction, they have come to occupy an important niche in the antifungal pharmacotherapy, due to their efficacy, safety, tolerability and favourable pharmacokinetic profiles. This review deals with the varying facets of echinocandins such as their chemistry, in-vitro and in-vivo evaluations, clinical utility and indications, pharmacokinetic and pharmacodynamic profiles, and pharmacoeconomic considerations.

Key findings

Clinical studies have demonstrated that the echinocandins – caspofungin, micafungin and anidulafungin – are equivalent, if not superior, to the mainstay antifungal therapies involving amphotericin B and fluconazole. Moreover, echinocandin regimen has been shown to be more cost-effective and economical. Hence, the echinocandins have found favour in the management of invasive systemic fungal infections.

Conclusions

The subtle differences in echinocandins with respect to their pharmacology, clinical therapy and the mechanisms of resistance are emerging at a rapid pace from the current pool of research which could potentially aid in extending their utility in the fungal infections of the eye, heart and nervous system.

Clinical hepatotoxicity associated with antifungal agents

INTRODUCTION

Invasive fungal diseases (IFDs) are a leading cause of morbidity and mortality among immunocompromised patients with bone marrow failure syndromes, hematological malignancies, hematopoietic stem cell transplantation (HSCT), those admitted in intensive care units (ICUs) and those with prolonged febrile neutropenia. IFDs occur in a setting of multiple morbidities and are associated with case fatality rates between 30 and 70%. Along with the development of classes and compounds, the last two decades have seen substantial improvements in the prevention and management of these infections and an overall increased use of antifungal agents. Areas covered: All antifungal agents, including amphotericin B formulations, echinocandins and the triazoles, may cause hepatic toxicity that ranges from mild and asymptomatic abnormalities in liver function tests to substantial liver injury and fulminant hepatic failure. Expert opinion: The present article reviews incidence and severity of hepatotoxicity associated with different classes and agents to provide a better understanding of this specific end organ toxicity and safer use of antifungal agents A thorough understanding of the distribution, metabolism, elimination and drug-drug interactions of antifungal agents used for management of IFDs in combination with safety data from clinical trials, pharmacokinetic and pharmacodynamic studies may guide the use of antifungal treatment in patients at high risk for the development of hepatic dysfunction and in those with underlying liver damage due to cytotoxic therapy.

Role of Echinocandins in Fungal Biofilm-Related Disease: Vascular Catheter-Related Infections, Immunomodulation, and Mucosal Surfaces

Biofilm-related infections have become an increasingly important clinical problem. Many of these infections occur in patients with multiple comorbidities or with impaired immunity. Echinocandins (caspofungin, micafungin, and anidulafungin) exert their fungicidal activity by inhibition of the synthesis of the (1→3)-β-d-glucan. They are active among in vitro and in vivo model systems against a number of Candida species and filamentous fungi in their planktonic and biofilm phenotype. Their superior activity against biofilms poses them in an advantageous position among the antifungal armamentarium. However, additional studies are warranted to expand our knowledge on the role of echinocandins against biofilm-related infections.

Efficacy and safety of micafungin versus intravenous itraconazole as empirical antifungal therapy for febrile neutropenic patients with hematological malignancies: a randomized, controlled, prospective, multicenter study

Micafungin, a clinically important echinocandin antifungal drug, needs to be investigated as empirical therapy in febrile neutropenia in comparison with azole compounds. A prospective randomized study was conducted to compare clinical outcomes between micafungin and intravenous itraconazole as an empirical therapy for febrile neutropenia in hematological malignancies. The antifungal drug (micafungin 100 mg or itraconazole 200 mg IV once daily) was given for high fever that was sustained despite the administration of appropriate antibiotics. Treatment success was determined by composite end points based on breakthrough invasive fungal infection (IFI), survival, premature discontinuation, defervescence, and treatment of baseline fungal infection. Duration of fever, hospital stay, and overall survival (OS) were studied. A total of 153 patients were randomized to receive micafungin or itraconazole. The overall success rate was 7.1 % point higher in the micafungin group (64.4 vs. 57.3 %, p = 0.404), satisfying the statistical criteria for the non-inferiority of micafungin. The duration of fever and hospital stay were significantly shorter in the micafungin group (6 vs. 7 days, p = 0.014; 22 vs. 27 days, p = 0.033, respectively). Grade 3 adverse events including hyperbilirubinemia (2 vs. 7), elevation of transaminase levels (2 vs. 4), electrolyte imbalance (1 vs. 2), atrial fibrillation (1 vs. 0), and anaphylaxis (1 vs. 0) occurred in 7 and 13 patients in the micafungin (10.4 %) and itraconazole (18.8 %) groups, respectively. Micafungin, when compared with itraconazole, had favorably comparable success rate and toxicity profiles on febrile neutropenia in patients with hematological malignancies. In addition, it showed superior effect on shortening the hospital stay.

Micafungin: an evidence-based review of its place in therapy

Invasive fungal infections have increased throughout the world. Many of these infections occur in patients with multiple comorbidities who are receiving medications with the potential for interactions with antifungal therapy that could lead to renal and hepatic dysfunction. The second marketed echinocandin, micafungin, was approved in 2005 for the treatment of esophageal candidiasis and prophylaxis of invasive Candida infections in patients undergoing hematopoietic stem cell transplantation. The indication for use was later expanded to include candidemia, acute disseminated candidiasis, Candida abscesses, and peritonitis. Like other echinocandins it is fungicidal against Candida species, including those that are polyene- and azole-resistant and fungistatic against Aspergillus species. Its formulation is by the intravenous route only and it is dosed once daily without a loading dose as 85% of the steady state concentration is achieved after three daily doses. It has a favorable tolerability profile with no significant drug interactions and does not need adjustment for renal or hepatic insufficiency.

Echinocandin antifungals: review and update

The echinocandins are a new and unique class of antifungal agents that act on the fungal cell wall by way of noncompetitive inhibition of the synthesis of 1,3-beta-glucans. All agents of this class are of parenteral formulation, with no oral preparations available. Caspofungin (Cancidas) was the first approved echinocandin, followed recently by micafungin (Mycamine) and anidulafungin (Eraxis). The precise role of the echinocandins in the antifungal armamentarium is still unfolding. Caspofungin is approved for the treatment of candidal esophagitis and candidemia, salvage therapy of Aspergillus infections and for empirical therapy of febrile neutropenia. Micafungin is likewise approved for candidal esophagitis, in addition to antifungal prophylaxis for hematopoietic stem cell transplant recipients. Anidulafungin is also approved for treatment of candidal esophagitis, as well as therapy of candidemia. There has been anecdotal use of these agents to treat less common fungal pathogens, as well as limited use as a component of combination antifungal therapy. The echinocandins are an important addition to the antifungal armamentarium in the treatment of fungal infections in both immunocompromised patients and those with normal immunity.

Micafungin: the US perspective

Invasive fungal infections cause considerable morbidity and mortality in nosocomial settings and amongst immunocompromised hosts. Invasive candidiasis and aspergillosis remain the most common invasive fungal infections, with Candida spp. constituting the fourth most common bloodstream infection in the USA. Currently available antifungal therapies include the polyene, antimetabolite, allylamine, azole and echinocandin drug classes. Micafungin, approved in March 2005 by the Food and Drug Administration for use in the USA, has shown safety and efficacy for the treatment of candidiasis and aspergillosis in clinical trials in Japan, Europe and South Africa. Micafungin holds promise as a first-line treatment option for candidiasis, as well as prophylaxis against invasive fungal infections during periods of neutropenia in high-risk patients.

Invasive candidiasis: update on current pharmacotherapy options and future perspectives

INTRODUCTION

Invasive candidiasis (IC), mainly candidemia, is a leading cause of morbidity and mortality among immunocompromised patients and those admitted to intensive care units. Despite the recognition of risk factors and advances in disease prevention, Candida-related hospitalizations and mortality continue to rise. For treatment, four classes of older and newer antifungal agents are currently available. Adjunctive immunotherapies and a monoclonal antibody against heat shock protein 90 (efungumab) are promising novel therapeutic approaches.

AREAS COVERED

In this article, approaches and therapeutic agents for candidemia and other forms of IC are reviewed.

EXPERT OPINION

The thorough understanding of the available antifungal agents in combination with the increasing knowledge of the mechanisms that underlie the pathogenesis of Candida infections and the development of newer approaches such as efungumab and immunotherapy with adjunctive cytokines may improve the prognosis of patients with life-threatening invasive Candida infections.

New β-glucan inhibitors as antifungal drugs

INTRODUCTION

New classes of synthetic and semi-synthetic β-glucan inhibitors have recently emerged, providing analogs that, in some cases, have been proven to have a high degree of activity against fungi, offering the prospect of alternatives to the commercially available lipopeptide/echinocandin agents caspofungin, micafungin and anidulafungin.

AREA COVERED

This review covers applications disclosing compound classes that include synthetic pyridazinone analogs, bicyclic heteroaryl ring compounds, aniline derivates, and semi-synthetic echinocandin and enfumafungin derivatives. MK-3118 is an analog of the natural product enfumafungin that, in particular, shows promise as it has a spectrum of activity comparable with caspofungin but has the advantageous property of oral bioavailability.

EXPERT OPINION

The diversity of chemical classes in the present review, which have demonstrable activity against β-glucan and the prospect of oral bioavailability, offers hope that safe and effective antifungal drugs will emerge and be commercialized. Of particular note, the Merck compound MK-3118, with solid evidence of efficacy based on preclinical data, has moved into clinical trials.

[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.

Comparison of echinocandin antifungals

The incidence of invasive fungal infections, especially those due to Aspergillus spp. and Candida spp., continues to increase. Despite advances in medical practice, the associated mortality from these infections continues to be substantial. The echinocandin antifungals provide clinicians with another treatment option for serious fungal infections. These agents possess a completely novel mechanism of action, are relatively well-tolerated, and have a low potential for serious drug-drug interactions. At the present time, the echinocandins are an option for the treatment of infections due Candida spp (such as esophageal candidiasis, invasive candidiasis, and candidemia). In addition, caspofungin is a viable option for the treatment of refractory aspergillosis. Although micafungin is not Food and Drug Administration-approved for this indication, recent data suggests that it may also be effective. Finally, caspofungin- or micafungin-containing combination therapy should be a consideration for the treatment of severe infections due to Aspergillus spp. Although the echinocandins share many common properties, data regarding their differences are emerging at a rapid pace. Anidulafungin exhibits a unique pharmacokinetic profile, and limited cases have shown a potential far activity in isolates with increased minimum inhibitory concentrations to caspofungin and micafungin. Caspofungin appears to have a slightly higher incidence of side effects and potential for drug-drug interactions. This, combined with some evidence of decreasing susceptibility among some strains of Candida, may lessen its future utility. However, one must take these findings in the context of substantially more data and use with caspofungin compared with the other agents. Micafungin appears to be very similar to caspofungin, with very few obvious differences between the two agents.

Evaluation of the safety and efficacy of micafungin in Japanese patients with deep mycosis: a post-marketing survey report

The safety and efficacy of micafungin were evaluated in a Japanese post-marketing survey involving 1,142 patients with deep mycosis caused by Candida or Aspergillus. The overall clinical response was 83.0%, and the respective responses for patients with candidiasis or aspergillosis were 86.3 and 70.8%. With regard to drug reactions, 562 adverse reactions were observed in 28.5% of patients. Among the 83 serious adverse drug reactions reported by 53 patients, a causal relationship with micafungin was assessed as definite or probable for 6 reactions in 5 patients. Age and baseline hepatic and renal function status did not affect the incidence of adverse reactions, although incidence increased significantly in proportion to the severity of mycosis and daily dose (p < 0.01). In multiple logistic regression analysis, neither baseline hepatic impairment nor increased daily dose of micafungin affected the incidence of hepatobiliary disorders, however, the severity of mycosis was found to correlate significantly with hepatobiliary disorders (p = 0.031). Taken together, our post-marketing findings show that micafungin is effective against deep mycosis caused by Candida or Aspergillus in patients across a range of backgrounds.

Overview of treatment options for invasive fungal infections

The introduction of several new antifungals has significantly expanded both prophylaxis and treatment options for invasive fungal infections (IFIs). Relative to amphotericin B deoxycholate, lipid-based formulations of amphotericin B have significantly reduced the incidence of nephrotoxicity, but at a significant increase in drug acquisition cost. Newer, broad-spectrum triazoles (notably voriconazole and posaconazole) have added significantly to both the prevention and treatment of IFIs, most notably Aspergillus spp. (with voriconazole) and the treatment of some emerging fungal pathogens. Finally, a new class of parenteral antifungals, the echinocandins, is employed most frequently against invasive candidal infections. While the role of these newer agents continues to evolve, this review summarizes the activity, safety and clinical applications of agents most commonly employed in the treatment of IFIs.

Clinical efficacy and safety of micafungin in Japanese patients with chronic pulmonary aspergillosis: a prospective observational study

Aspergillosis has been the prevailing deep-seated mycosis in Japan since the 1990s. Although micafungin (MCFG) has been approved in Japan for the management of patients with such infections caused by Candida and Aspergillus species, there are relatively few reports on its use in patients with chronic pulmonary aspergillosis (CPA). Therefore, we conducted a prospective observational study to evaluate the efficacy and safety of the use of MCFG in Japanese patients with CPA. The efficacy of the antifungal was assessed on the basis of improvements in clinical symptoms and radiological findings. In addition, adverse events, including abnormal laboratory findings were determined. The overall clinical efficacy rate was 68.4% (26/38 patients), which is comparable to the results obtained in clinical trials for marketing approval conducted in Japan. Although adverse drug reactions were observed in six patients (15.8%), they were not serious. The most common of these reactions was abnormal liver functions. No relationship between the incidence of adverse drug reactions and age of the patients, MCFG dose, or duration of treatment was observed. Consequently, MCFG has favorable efficacy and safety profiles in Japanese CPA patients with various backgrounds.

Echinocandin pharmacodynamics: review and clinical implications

Echinocandins have made a significant impact in the treatment of select invasive fungal infections, most notably invasive candidiasis and aspergillosis. However, treatment outcomes for such infections are still less than optimal, prompting an examination of dosing and administration techniques in an attempt to exploit known pharmacodynamic properties and improve outcomes. Echinocandins generally exhibit concentration-dependent, fungicidal activity against Candida spp. and fungistatic activity against Aspergillus spp. However, increasing drug concentrations of echinocandins above the organism's MIC may result in a paradoxical increase in fungal growth as demonstrated in some in vitro and in vivo models (known most commonly as the 'Eagle effect'). Therefore, the potential impact of dose escalations on improving the clinical efficacy of echinocandins based on in vitro and animal models are uncertain and are still being evaluated. In addition, such strategies have to consider the potential for increased treatment-related toxicities and costs. To date, published clinical studies (both superiority and non-inferiority) demonstrating the potential for dose-related improvements in treatment outcomes have been limited to mucocutaneous and oesophageal candidiasis. Further research is needed to determine if a role exists for optimizing echinocandin pharmacodynamics in various clinical settings.

Review of the pharmacology and clinical studies of micafungin

Micafungin, like other members of the echinocandin class, has a unique mechanism of action that inhibits the synthesis of 1,3-β-D glucans in the fungal cell wall. It has been approved for treatment of esophageal candidiasis, invasive candidiasis including candidemia, and for prophylaxis of Candida infections in patients undergoing hematopoietic stem cell transplantation. Although efficacy and safety have also been demonstrated in pediatric populations, micafungin is approved for this indication in Europe and Japan, but not in the United States. It has demonstrated activity against Candida spp. including those that are azole-resistant as well as Aspergillus and a few other clinically important molds. It is administered intravenously as a once daily infusion and does not require dose adjustments for renal or moderate hepatic dysfunction. Its safety record, favorable tolerability profile, and few drug interactions make it an important agent for the treatment of invasive fungal infections.

Echinocandins: The Newest Class of Antifungals

Objective:

To review the mechanism of action, antifungal spectrum of activity, pharmacodynamics, pharmacokinetics, clinical efficacy, and safety of the echinocandins.

Data Sources:

A MEDLINE search (1982–May 2009) was conducted for articles published in the English language using the key words caspofungin, micafungin, anidulafungin, and echinocandins.

Study Selection and Data Extraction:

Medicinal chemistry, in vitro, and animal studies, as well as human trials were reviewed for information on the pharmacodynamics, pharmacokinetics, efficacy, and safety of each echinocandin. Clinical trials were reviewed and included to compare and contrast the available echinocandins.

Data Synthesis:

Three echinocandin antifungal agents are currently approved for use in the US: caspofungin, micafungin, and anidulafungin. The echinocandins have a unique mechanism of action, inhibiting β-(1,3)-d-glucan synthase, an enzyme that is necessary for the synthesis of an essential component of the cell wall of several fungi. The echinocandins display fungistatic activity against Aspergillus spp. and fungicidal activity against most Candida spp., including strains that are fluconazole-resistant. The echinocandins have been shown to be efficacious for the treatment of esophageal candidiasis, candidemia, and invasive candidiasis. In addition, caspofungin has demonstrated efficacy as empiric treatment of febrile neutropenia and salvage therapy for the treatment of invasive aspergillosis, and it is the only echinocandin approved for use in pediatric patients. Micafungin is the only echinocandin approved for use as prophylaxis against Candida infections in patients undergoing hematopoietic stem cell transplantation. Overall, resistance to echinocandins is still rare, and all agents are well tolerated, with similar adverse effect profiles and few drug–drug interactions.

Conclusions:

Echinocandins, the newest addition to the arsenal of antifungals, offer potential advantages over other classes of agents. Clinicians should assess their distinguishing characteristics, including route of metabolism, drug interaction profile, and approved indications for use, when determining which agent to include on a formulary.

[Micafungin in invasive candidiasis among oncohematological patients]

BACKGROUND

Invasive candidiasis is a severe infection among onco-hematological patients, with an attributable mortality around 40%. Micafungin has shown efficacy in antifungal prophylaxis among hematopoietic stem cell transplant recipients and in the treatment of esophageal candidiasis.

AIMS

To assess the role of micafungin in the treatment of invasive candidiasis among onco-hematological patients.

METHODS

Literature review.

RESULTS

In a study on 126 patients with candidemia treated with micafungin, an overall response rate of 83% was reported. A double-blind study of 531 patients with invasive candidiasis comparing micafungin (100mg/day) versus liposomal amphotericin B (3mg/kg/day) reported success in 90% of patients in both arms, with a more favorable safety profile with micafungin. Other double blind randomized, phase III study compared two doses of micafungin (100mg/day and 150mg/day) with standard doses of caspofungin (70mg loading dose, then 50mg/day) in adults with invasive candidiasis. Overall success rate was 74% for micafungin 100mg/day, 70% for micafungin 150mg/day, and 71% for caspofungin. A double blind randomized study compared micafungin (2mg/kg/day) to liposomal amphotericin B (3mg/kg/day) in the treatment of invasive candidiasis in children with a predominance of infections with non-albicans Candida spp. Overall success rate was similar (73% for micafungin and 76% for liposomal amphotericin B).

CONCLUSIONS

Comparative phase III studies have demonstrated non-inferiority of micafungin compared to standard antifungal agents for invasive candidiasis. Micafungin is safe and effective in the treatment of children and adults with invasive candidiasis. Effectivity in invasive infections caused by non-albicans Candida spp is especially relevant in onco-hematological patients receiving fluconazole prophylaxis.

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.

Micafungin: a sulfated echinocandin

Micafungin is the second approved antifungal agent in the echinocandin series and is now used worldwide in chemotherapy for life-threatening fungal infections. It is water-soluble and is semi-synthesized from the acylated cyclic hexapeptide FR901379, a natural product from the fungus Coleophoma empetri F-11899, through enzymatic deacylation of FR901379, followed by chemical reacylation with the optimized N-acyl side chain. The water solubility of micafungin is ascribed to a sulfate moiety in the molecule. This feature differentiates micafungin from other echinocandin members. Micafungin is a potent inhibitor of 1,3-beta-glucan synthase, an enzyme necessary for cell-wall synthesis of several fungal pathogens.

Micafungin for the prophylaxis and treatment of Candida infections

Invasive fungal infection is a significant cause of morbidity and mortality worldwide. The incidence of these infections is steadily increasing. In addition, strains resistant to many commonly used antifungal agents are becoming more prevalent. Many new antifungals have become commercially available in recent years, which have vastly improved the ability to treat these infections effectively. Micafungin is one of three commercially available echinocandins available for use in the USA. This class of agents possess a unique mechanism of action that helps to reduce toxicity while maintaining potent antifungal activity. Micafungin is currently approved for the treatment of esophageal candidiasis in adults and is the only in its class approved for the prophylaxis of Candida infection in patients who have undergone hematopoietic stem cell transplantation. It was also recently approved in the USA for the treatment of candidemia and other forms of invasive candiaisis (acute disseminated candiaisis, Candida peritonitis and abscess). In general, micafungin is well tolerated and has favorable safety and drug-interaction profiles.

Early clinical experience with anidulafungin at a large tertiary care medical center

STUDY OBJECTIVE

To evaluate early clinical experience with anidulafungin.

DESIGN

Retrospective cohort study.

SETTING

Large, university-affiliated, tertiary care medical center.

PATIENTS

All patients receiving anidulafungin between July 15, 2006, and January 15, 2007.

MEASUREMENTS AND MAIN RESULTS

Thirty-five patients received at least one dose of anidulafungin. Safety and tolerability were evaluated in all patients; efficacy outcomes were assessed in 13 patients who had a documented fungal infection and received anidulafungin for a minimum of 5 days. Common conditions at baseline were hepatic dysfunction (25 patients [71%]), severe sepsis (17 patients [49%]), and solid organ or hematopoietic stem cell transplantation (10 patients [29%]). Eight patients (23%) were receiving drugs with the potential to interact with echinocandins other than anidulafungin. Seventeen (49%) of the 35 patients received anidulafungin as empiric antifungal therapy. Anidulafungin was used to treat invasive candidiasis in seven patients (20%) and candidemia in 10 patients (29%); Candida albicans or Candida glabrata was isolated most frequently in these two infections combined (7 isolates each [41%]/17 infections). A favorable efficacy outcome was noted in 10 (77%) of 13 evaluable patients. One patient developed breakthrough Candida parapsilosis fungemia while receiving anidulafungin. Overall, anidulafungin was well tolerated, with only one patient having an infusion- related reaction. Anidulafungin was also well tolerated among patients receiving concomitant metronidazole.

CONCLUSION

Anidulafungin was well tolerated and produced favorable outcomes in the majority of the patients evaluated. The availability of anidulafungin makes it a feasible option for antifungal therapy, particularly in patients who have hepatic dysfunction and in those who are receiving drugs than can interact with other echinocandins.

Micafungin sodium, the second of the echinocandin class of antifungals: theory and practice

Micafungin is a new drug in the echinocandin class and is currently being investigated in Phase III clinical trials. Like other echinocandins, it inhibits 1,3-beta-D-glucan synthesis, thus achieving fungicidal activity against virtually all Candida spp., including those resistant to fluconazole, and fungistatic activity against Aspergillus spp. Micafungin sodium is available for intravenous administration only. It has a favorable safety and drug-drug interaction profile. Micafungin has been approved by the US FDA for treatment of esophageal candidiasis and for antifungal prophylaxis during the pre-engraftment phase in patients undergoing hematopoietic stem cell transplantation. Considering the competitive pricing as well as the good tolerability and efficacy, at present micafungin seems to be another choice for both of these indications. Current research has proven micafungin sodium to add a rational and effective option to the antifungal armamentarium, especially in esophageal candidiasis refractory to fluconazole treatment, in those intolerant to triazoles or in patients needing concomitant therapy interacting with triazoles. In addition to the current indications, recent uncontrolled clinical trials have demonstrated a marked success in the treatment of candidemia and invasive candidiasis. Results from in vitro studies, animal models, small clinical trials, as well as the obvious comparison with the more established caspofungin, hint at possible future indications such as invasive aspergillosis and empirical antifungal therapy. However, preclinical data on micafungin is inconsistent and published well-designed clinical studies are scarce. More controlled and sufficiently scaled trials are imperative in order to establish micafungin as a reliable and safe option in clinical practice.

Recent advances in antifungal chemotherapy

For over 50 years, amphotericin B deoxycholate (AmBD) has been the 'gold standard' in antifungal chemotherapy, despite its frequent toxicities. However, improved treatment options for invasive fungal infections (IFIs) have been developed during the last 15 years. Newer antifungal agents, including less toxic lipid preparations of AmBD, triazoles and the echinocandins, have been added to our armamentarium against IFIs. Some of these newer drugs can now replace AmBD as primary therapy (e.g. caspofungin for candidiasis, voriconazole for aspergillosis), whilst others offer new therapeutic options for difficult-to-treat IFIs (e.g. posaconazole for zygomycosis, fusariosis and chromoblastomycosis). It is interesting that extended use of newer antifungals such as fluconazole, despite decreasing the mortality attributed to candidiasis, resulted in selection of species resistant to several antifungals (Candida krusei, Candida glabrata); whilst several publications suggest that prolonged use of voriconazole may expose severely immunocompromised patients to the risk of zygomycosis (breakthrough). On the other hand, the differences in the mode of action of newer antifungals such as echinocandins raise the question whether combination antifungal therapy is more effective than monotherapy. Finally, the availability of an oral formulation with excellent biosafety of several newer antifungals (e.g. posaconazole) makes them candidates for prophylactic or prolonged maintenance therapy.

A comparative evaluation of properties and clinical efficacy of the echinocandins

With the increase in prevalence of fungal infections, newer antifungal agents are needed to effectively treat invasive disease, and at the same time minimize adverse effects from therapy. The echinocandins comprise a novel class of antifungals; their mechanism of action involves inhibiting 1,3-beta-D-glucan synthase, which is essential in cell wall synthesis for certain fungi. All three echinocandins are US FDA-approved for the treatment of esophageal candidiasis. Caspofungin and anidulafungin are licensed for the treatment of candidemia, and other select forms of invasive candidiasis. Micafungin is at present the only echinocandin approved for prophylaxis of fungal infections in hematopoietic stem cell transplants; whereas caspofungin is approved for empiric therapy of febrile neutropenia. Although all three echinocandins are active against Aspergillus, only caspofungin is presently approved for salvage therapy in invasive aspergillosis. Combination therapy with echinocandins plus other licensed antifungal therapy shows promise in treating invasive aspergillosis. This article will explore the similarities and differences among the echinocandins.

The Echinocandins

The changing pattern in fungal infections has driven the need to expand the targets of antifungal activity. The echinocandins are the newest addition to the arsenal against fungal infections. Three echinocandins have been approved by the United States Food and Drug Administration: caspofungin, micafungin, and anidulafungin. These agents have a broad spectrum of activity and are similar to each other with respect to in vitro activity against Candida sp, with micafungin and anidulafungin having similar minimum inhibitory concentrations (MICs) that are generally lower than the MIC of capsofungin. The MICs of the echinocandins are highest against Candida parapsilosis; however, whether this will affect clinical outcomes is unknown. Several case reports have identified clinical failure due to elevated MICs with caspofungin or micafungin against Candida albicans, Candida krusei, and C. parapsilosis. Resistance to the echinocandin class was present in some but not all of the isolates. Empiric therapy with one of the echinocandins for candidemia or invasive candidiasis in patients with neutropenia and those without neutropenia appears to be appropriate when one factors in mortality rate, the increasing frequency of non-albicans Candida infections, and the broad spectrum, safety, and fungicidal effect of the echinocandins. After speciation of the organism, continued therapy with an echinocandin can and should be reevaluated. The echinocandins demonstrate similar in vitro and in vivo activity against Aspergillus sp, but only caspofungin is approved for treatment in patients who are intolerant of or refractory to other therapies. Voriconazole and amphotericin B have demonstrated synergy with the echinocandins. The clinical response to combination therapy has been variable; however, the mortality rate appears to be lower with combination therapy than monotherapy. Large controlled trials are needed to determine the role of combination therapy for invasive aspergillosis. Micafungin and anidulafungin generally have a lower frequency of adverse reactions compared with caspofungin. Phlebitis (3.5-25% of patients) and elevated liver enzyme levels (1-15%) occur more often with caspofungin compared with micafungin and anidulafungin (< 8%). Overall, the three echinocandins are relatively safe and effective agents for the treatment of Candida infections.

Systemic antifungal agents: an update of established and new therapies

Terbinafine is the drug of choice for dermatophyte onychomycosis. Adjunct therapies, such as topical agents or surgical approaches, may improve outcomes in patients who have risk factors for incomplete response or recurrence. Despite many studies of newer antifungal agents for tinea capitis, griseofulvin (20 mg/kg/d) remains the gold standard. Terbinafine (> or = 6 mg/kg/d) and fluconazole (8 mg/kg once weekly) have yet to demonstrate comparable efficacy in large-scale RCTs. The current role of second-generation triazoles and echinocandins is for treatment of invasive candidiasis and invasive aspergillosis in patients who are critically ill and immunocompromised. Strengths of the newer triazoles include increased activity against resistant and emerging pathogens, convenience of oral formulations, and in vivo activity against subcutaneous mycoses, in particular eumycotic mycetoma. Their metabolism via cytochrome P450 isoenzymes increases the risk for significant drug interactions, and their established mechanism of action may lead to development of resistant pathogens. The echinocandins inhibit fungal cell wall synthesis, a novel therapeutic target; thus, they are effective against azole-resistant species. Their metabolism is independent of hepatic cytochrome P450 enzymes, minimizing drug interactions. They are available only as i.v. formulations.

Relationship between the initial dose of micafungin and its efficacy in patients with candidemia

Micafungin, the first licensed echinocandin in Japan, has shown excellent in vitro and in vivo activity against all Candida species. However, the appropriate dose for the initial treatment of candidemia remains to be determined. In this study, we retrospectively examined the relationship between the clinical outcome of candidemia and the initial dose of micafungin. Patients were divided into two groups according to the initial dose of micafungin administered: group I (<2.25 mg/kg/day) and group II (>or=2.25 mg/kg/day). Micafungin produced an excellent 30-day clinical response in patients with candidemia, including Candida parapsilosis; the overall 30-day clinical response was 86%. The administration of higher doses of micafungin accelerated the clinical response and duration until the clinical response in group II was significantly shorter than that in group I (P = 0.021). However, no significant differences were observed in the 30-day mortality attributable to the fungal infection between the two groups. Considering these results, we recommend the administration of 2.25 mg/kg/day or more of micafungin in the initial treatment of patients with candidemia.

Efficacy and safety of micafungin in febrile neutropenic patients treated for hematological malignancies

OBJECTIVE

The purpose of this study was to prospectively evaluate the efficacy and safety of micafungin (MCFG) in empirical therapy for febrile neutropenic patients for whom antibiotic therapy was not effective for hematological malignancies.

PATIENTS AND METHODS

Twenty-three hematological patients aged 27-82 years with febrile neutropenia for whom antibiotic therapy was not effective were enrolled in this study and responses to treatment were evaluated.

RESULTS

Treatment success rate was 73.9%. Treatment success rates by primary diagnosis were 77.8% in patients with AML, 50.0% in patients with NHL and 87.5% in patients with other diseases. Moreover, MCFG at a dose of 100 mg or more have a tendency to be effective. One or more adverse events occurred in five (27.7%) of the patients during the study. All of these adverse events were below grade 2 toxicity.

CONCLUSIONS

Although the number of patients studied was limited, MCFG as a monotherapy seems to be effective and safe as an empirical therapy in patients with febrile neutropenia. However, further investigation using large-scale studies is needed. This study demonstrated the clinical efficacy and safety of MCFG in patients with febrile neutropenia and with hematological malignancies.

The echinocandins: comparison of their pharmacokinetics, pharmacodynamics and clinical applications

Caspofungin, micafungin and anidulafungin are three drugs of the echinocandin class of antifungals available for intravenous treatment of invasive candidiasis and aspergillosis. They exhibit high in vitro and in vivo activities against Candida spp. and Aspergillus spp. In various clinical studies investigating candidemia and invasive candidiasis, Candida esophagitis, and fever in neutropenia, the clinical efficacy of the echinocandin tested was similar to that of established antifungals. Antifungal activity against strains no longer susceptible to conventional antifungal agents, such as fluconazole and amphotericin B suggests that echinocandins can be used as salvage therapy in life-threatening fungal infections. There is no cross-resistance to other antifungals. Excellent safety and tolerability of treatment with caspofungin has been documented over a total of 4.3 million patient days. Echinocandins are poor substrates of the cytochrome P450 enzyme family and can be safely co-administered with most drugs without the need for dosage adaptation. No dose reduction is required in renal impairment. A reduction in the daily maintenance dose has been recommended for caspofungin, but not for micafungin and anidulafungin in patients presenting with mild to moderate hepatic failure.

Developments in the treatment of candidiasis: more choices and new challenges

The incidence of oesophageal candidiasis, candidaemia and disseminated candidiasis has increased dramatically. In addition to the amphotericin B formulations and fluconazole, the echinocandins anidulafungin, caspofungin and micafungin and the newer triazoles posaconazole and voriconazole are in the last stages of development and are becoming available for the management of candidiasis. This review presents these new agents and addresses their role in the treatment of candidiasis. All new antifungal agents exhibit potent activity against Candida spp. and echinocandins are fungicidal against most Candida spp. but appear to be less potent against certain species, such as Candida parapsilosis and C. guilliermondii. Systemic antifungal therapy can now be individualised based on the severity of the infection, comorbid conditions and the Candida spp. causing the infection. Studies are needed to investigate the possible development of resistance and the efficacy of these antifungal agents against the more resistant Candida spp.

Echinocandins in the management of invasive fungal infections, part 1

PURPOSE

The chemistry, pharmacology, spectrum of activity, resistance, pharmacokinetics, pharmacodynamics, clinical efficacy, adverse effiects, drug interactions, dosage and administration, cost, and place in therapy of echinocandins are reviewed.

SUMMARY

Three echinocandins are currently available: caspofungin, micafungin, and anidulafungin. The principal mechanism of action of the echinocandins is the noncompetitive inhibition of beta-(1,3)-dglucan synthase, an essential component of the cell wall of many fungi that is not present in mammalian cells. Echinocandins exhibit fungicidal activity against Candida species, including triazole-resistant isolates, and fungistatic activity against Aspergillus species. While fungistatic against mold, echinocandins may hold promise for the treatment of these pathogens when given in combination with amphotericin B or broad-spectrum triazoles, such as voriconazole. To date, resistance to echinocandins has been reported in only two patients. Echinocandins exhibit concentration- dependent activity against Candida species. In clinical trials, caspofungin has demonstrated efficacy in treating candidemia, esophageal candidiasis, and febrile neutropenia. Micafungin has demonstrated efficacy as antifungal prophylaxis in hematopoietic stem cell transplant recipients and in the treatment of esophageal candidiasis. Anidulafungin received approved labeling from the Food and Drug Administration in February 2006. Clinical efficacy data will be forthcoming.

CONCLUSION

Echinocandins are fungicidal against yeast and fungistatic against mold. Their limited toxicity profile and minimal drug-drug interactions make them an attractive new option for the treatment of invasive fungal infections. Their cost may limit their use as initial therapy for patients with fungemia in medical centers or intensive care units with a high rate of triazoleresistant Candida infections.

New agents for the treatment of fungal infections: clinical efficacy and gaps in coverage

The incidence of fungal infections has increased globally, and the introduction of the newer triazoles and echinocandin antifungals is a more-than-welcome and long overdue development. In this report, we review the clinical trials evaluating the therapeutic efficacy of these new antifungal agents and examine possible gaps in coverage. Voriconazole has become the primary treatment for most forms of invasive aspergillosis in a number of centers, posaconazole offers a broad antifungal spectrum, and echinocandins are fungicidal against most Candida species. Moreover, the new agents are active against some fungi that are resistant to amphotericin B, may have a role in the management of fever and neutropenia, and provide exciting options for combination antifungal therapy. However, significant questions remain, including the management of breakthrough infections and treatment failures and the efficacy of the new antifungal agents against less common fungi.

Emerging echinocandins for treatment of invasive fungal infections

The echinocandins are a new class of antifungals, developed in response to the need for safe and effective antifungals for the treatment of invasive fungal infections. These agents work by inhibiting 1,3-beta-d-glucan synthase, an enzyme essential for production of cell walls in select fungi. Echinocandins appear to demonstrate favourable activity in vitro against a variety of yeasts (including both Candida albicans and non-albicans Candida) as well as select moulds (including Aspergillus spp.) In general, all echninocandins demonstrate a favourable safety profile and require once-daily parenteral administration. Caspofungin is the first of these agents to be available in the US, and is approved for empirical antifungal therapy in febrile neutropenic patients, candidaemia and select forms of invasive candidiasis, and for management of invasive aspergillosis in patients refractory to or intolerant of other therapies. Micafungin was recently approved by the FDA for treatment of oesophageal candidiasis, and for the prophylaxis of fungal infections in haematopoietic stem cell transplant recipients. Emerging data indicate micafungin may have an important role in the treatment of invasive forms of candidiasis. Anidulafungin is an echinocandin approved in the US for treatment of candidaemia and oesophageal candidiasis. Aminocandin (HMR-3702, IP-960) is an investigational agent, with published experience limited to in vitro studies and animal models of infection.

Micafungin (FK463), alone or in combination with other systemic antifungal agents, for the treatment of acute invasive aspergillosis

BACKGROUND

Micafungin (FK463) is a new lipopeptide compound (echinocandin) with activity against Aspergillus and Candida species. This study evaluated the safety and efficacy of micafungin in patients with proven or probable invasive aspergillosis (IA).

METHODS

A multinational, non-comparative study was conducted to examine proven or probable (pulmonary only) Aspergillus species infection in a wide variety of patient populations. The study employed an open-label design utilizing micafungin alone or in combination with another systemic antifungal agent. Criteria for IA and therapeutic responses were judged by an independent panel.

RESULTS

Of the 331 patients enrolled, only 225 met diagnostic criteria for IA as determined by the independent panel and received at least one dose of micafungin. Patients included 98/225 who had undergone hematopoietic stem cell transplantation (HSCT) (88/98 allogeneic), 48 with graft versus host disease (GVHD), and 83/225 who had received chemotherapy for hematologic malignancy. A favorable response rate at the end of therapy was seen in 35.6% (80/225) of patients. Of those only treated with micafungin, favorable responses were seen in 6/12 (50%) of the primary and 9/22 (40.9%) of the salvage therapy group, with corresponding numbers in the combination treatment groups of 5/17 (29.4%) and 60/174 (34.5%) of the primary and salvage treatment groups, respectively. Of the 326 micafungin-treated patients, 183 (56.1%) died during therapy or in the 6-week follow-up phase; 107 (58.5%) deaths were attributable to IA.

CONCLUSIONS

Micafungin as primary or salvage therapy proved efficacious and safe in high-risk patients with IA, although patient numbers are small in the micafungin-only groups.

Micafungin: a new echinocandin

Micafungin, a potent inhibitor of 1,3-beta-D-glucan synthase, has become the second available agent in the echinocandins class that is approved for use in clinical practice. This agent shares with caspofungin an identical spectrum of in vitro activity against Candida albicans, non-albicans species of Candida, and Aspergillus species, as well as several but not all pathogenic molds. If anything, its in vitro activity appears to be superior to that of caspofungin, although the clinical relevance of this observation is unclear. The clinical role of micafungin appears to be similar to that of caspofungin, although clinical data are still lacking at this stage, with initial approval only for treatment of esophageal candidiasis and prophylaxis in subjects with neutropenia. Pharmacokinetic and pharmacodynamic studies and reports of adverse effects and safety have reported similar but not identical results to those of other agents in the echinocandin class. Factors such as acquisition costs and the potential for resistance development may be more relevant to its widespread use than in vitro and in vivo data comparisons with caspofungin.

A Multicenter Randomized Trial Evaluating Posaconazole versus Fluconazole for the Treatment of Oropharyngeal Candidiasis in Subjects with HIV/AIDS

BACKGROUND

Oropharyngeal candidiasis is the most common opportunistic infection among persons infected with human immunodeficiency virus (HIV). Use of some agents is hampered by lack of efficacy, emergence of resistance, adverse events, and need for intravenous administration. Posaconazole is an extended-spectrum triazole with potent in vitro activity against Candida species, including Candida albicans, Candida glabrata, and Candida krusei (including fluconazole-resistant strains).

METHODS

This multicenter, randomized, evaluator-blinded study of subjects with HIV infection and oropharyngeal candidiasis compared efficacy of posaconazole with that of fluconazole. Subjects received either 200 mg of posaconazole or fluconazole oral suspension on day 1, followed by 100 mg/day for 13 days. The primary study end point--clinical success (cure or improvement) on day 14--was evaluated for 329 subjects. Durability of clinical success was evaluated on day 42.

RESULTS

Three hundred fifty subjects received posaconazole (n = 178) or fluconazole (n = 172). Clinical success occurred in 155 (91.7%) of 169 posaconazole recipients and in 148 (92.5%) of 160 fluconazole recipients (95% confidence interval, -6.61% to 5.04%), indicating that posaconazole was not inferior to fluconazole. On day 14, mycological success was 68% in both arms, but by day 42, significantly more posaconazole recipients than fluconazole recipients continued to have mycological success (40.6% vs. 26.4%; P=.038). Fewer posaconazole recipients than fluconazole recipients experienced clinical relapse (31.5% vs. 38.2%). Adverse events were similar between treatment arms.

CONCLUSIONS

Results demonstrate that posaconazole was as effective as fluconazole in producing a successful clinical outcome. However, posaconazole was more effective in sustaining clinical success after treatment was stopped.

Gastrointestinal infections in immunocompromised hosts

PURPOSE OF REVIEW

Gastrointestinal infections in the immunocompromised host continue to have significant morbidity and mortality throughout the world. They all have similar exposures to viruses, bacteria and parasites and respond to these infections in a similar way. This review will summarize the latest reports on the epidemiology, diagnosis and treatment of known and emerging infections over the last 12 months.

RECENT FINDINGS

Highly active antiretroviral therapy has reduced esophageal opportunistic infections in HIV patients compared to patients who are not taking this therapy. Esophageal candidiasis responds to escalating doses of micafungin as effectively as fluconazole. HIV-infected patients with untreated Mycobacterium avium-complex diarrhea are associated with a wasting syndrome that disrupts the somatostatin axis. Polymerase chain reaction testing has improved diagnosis of microsporidial infections. Cytomegalovirus polymerase chain reaction of tissue may improve the diagnosis of cytomegalovirus disease of the gastrointestinal tract in organ-transplant recipients. The treatment of hypogammaglobulinemia in transplant recipients with recurrent cytomegalovirus gastrointestinal disease may resolve their symptoms. Community viruses are an emerging threat to transplant recipients and may affect drug levels. Lastly, anti-tumor necrosis factor alpha therapy in the treatment of inflammatory conditions may cause Listeria monocytogenes to disseminate.

SUMMARY

Immunocompromised hosts remain at risk for severe gastrointestinal and even disseminated infections. Management includes an early rapid diagnosis with rapid restoration of the immune system and appropriate anti-infective therapy. With the immunocompromised population rapidly increasing, prevention of these infections remains the greatest challenge.