Micafungin versus fluconazole for prophylaxis against invasive fungal infections during neutropenia in patients undergoing hematopoietic stem cell transplantation

Is combination antifungal therapy for invasive aspergillosis a necessity in hematopoietic stem-cell transplant recipients?

PURPOSE OF REVIEW

The use of combination antifungal therapy in hematopoietic stem-cell transplantation patients is controversial and limited by a paucity of controlled data. The recent literature is reviewed and the relative arguments for and against combination antifungal therapy are outlined with summative recommendations to assist practitioners in decision-making.

RECENT FINDINGS

There is an abundance of in-vitro and murine in-vivo combination antifungal literature, whereas clinical data are less abundant and controlled. Of the published case series there is a suggested benefit to combination therapy over monotherapy, although there are limitations to the available literature. Other issues in the combination debate that are addressed include the following: improved response rates and a survival advantage have been demonstrated in recent monotherapy studies; response rates in most published combination therapy studies do not suggest large gains over monotherapy; the lack of sustained survival advantage to combination therapy studies; and finally the consideration of host defenses in treatment responses.

SUMMARY

Based on available data, combination therapy is not warranted at the initial diagnosis of invasive aspergillosis. Randomized, controlled trials with rigorous study design are needed.

Review of Epidemiology, Diagnosis, and Treatment of Invasive Mould Infections in Allogeneic Hematopoietic Stem Cell Transplant Recipients

Invasive mould infections are a major cause of morbidity and mortality in hematopoietic stem cell transplant recipients (HSCT). Allogeneic HSCT recipients are at substantially higher risk than autologous HSCT recipients. Although neutropenia following the conditioning regimen remains an important risk factor for opportunistic fungal infections, most cases of invasive mould infection in allogeneic HSCT recipients occur after neutrophil recovery in the setting of potent immunosuppressive therapy for graft-versus-host disease. Invasive aspergillosis is the most common mould infection. However, there has been an increased incidence of less common non-Aspergillus moulds that include zygomycetes, Fusarium sp., and Scedosporium sp. Reflecting a key need, important advances have been made in the antifungal armamentarium. Voriconazole has become a new standard of care as primary therapy for invasive aspergillosis based on superiority over amphotericin B. There is significant interest in combination therapy for invasive aspergillosis pairing voriconazole or an amphotericin B formulation with an echinocandin. There have also been advances in novel diagnostic methods that facilitate early detection of invasive fungal infections that include galactomannan and beta-glucan antigen detection and PCR using fungal specific primers. We review the epidemiology, diagnosis, and management of invasive mould infection in HSCT, with a focus on allogeneic recipients. We also discuss options for prevention and early treatment of invasive mould infections.

Infectious Disease Update: New Anti-Microbials

Effective antimicrobials are critical in controlling one of the most common conditions encountered in medicine, namely, skin and skin structure infections. Unfortunately, the identification of appropriate and novel antimicrobials is continually challenged by the emergence of antimicrobial resistance among bacteria, fungi, and parasites. This work will focus on describing novel antibacterials and antifungals approved by the United States Food and Drug Administration in the past 4 years.

Treatment Options for Invasive Fungal Infections

Clinicians face an increasing occurrence of invasive fungal infections. These are due not only to traditional yeast and mould species but also to rare pathogens that can be difficult to treat. The introduction of new agents has expanded the options for treating common and rare mycotic infections with antifungal efficacy at least equal, and safety far superior, to that of a once-limited choice of therapies. Patients with invasive mycoses frequently have concomitant disorders and require multidrug regimens. Clinicians must be aware of the potential for interactions among agents available for treating invasive mycoses in patients with serious underlying conditions.

A study to determine the safety profile and maximum tolerated dose of micafungin (FK463) in patients undergoing haematopoietic stem cell transplantation

This open-label, dose-escalation study assessed the maximum tolerated dose (MTD) of the new antifungal micafungin in patients undergoing haematopoietic stem cell transplantation (HSCT). Participants received 3, 4, 6 or 8 mg/kg/day micafungin intravenously from 7 days to a maximum of 28 days or until neutropaenia resolved. The MTD was defined as the highest dose not causing the same Grade 3 or 4 adverse event in three or more patients. All 36 participants received >/=8 days treatment for a median of 18 days (range: 8-28); 1 patient withdrew consent and a further 11 discontinued to receive another systemic antifungal agent for a suspected infection. No case of confirmed invasive fungal infection occurred. Adverse events were those expected for patients undergoing HSCT and showed no evidence of dose-related toxicity. Criteria for MTD were not met; no patient had a Grade 3 or 4 adverse event considered causally related to micafungin. Thus, the MTD of micafungin can be inferred to be 8 mg/kg/day or higher.

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.

Breakthrough Trichosporonosis in Patients with Hematologic Malignancies Receiving Micafungin

BACKGROUND

Micafungin is a newly approved antifungal agent in the echinocandin class that is active against Candida species and Aspergillus species. However, this agent has limited activity against a number of fungi, including Trichosporon species. We describe 4 patients who developed disseminated trichosporonosis during the use of micafungin. No cases of trichosporonosis had been seen in the 2 years prior to January 2003, when micafungin became available in our hospital.

METHODS

We reviewed microbiological records of patients at Kameda General Hospital (Kamogawa City, Chiba, Japan) from 1 January 2002 to 31 July 2005, and identified 4 patients whose blood culture results were positive for Trichosporon species.

RESULTS

Since January 2003, four patients--3 with acute myelocytic leukemia and 1 with myelodysplastic syndrome--developed disseminated trichosporonosis while receiving treatment with micafungin with or without amphotericin B. The initial 2 isolates were identified as Trichosporon beigelii, and the later 2 isolates were identified as Trichosporon asahii. All 4 patients received micafungin, and 2 also received amphotericin B concomitantly. Minimal inhibitory concentrations of micafungin were >16 microg/mL for the 2 isolates available for susceptibility testing. One patient with hematologic recovery (neutrophils >500 cells/mm3) showed elimination of the fungus after receiving treatment with voriconazole. However, the 3 other patients without hematologic or immunological recovery died of disseminated infection.

CONCLUSIONS

The rarity of trichosporonosis in our hospital and its emergence after the introduction of micafungin therapy support the idea that micafungin may exert a significant, selective pressure toward resistant fungi, such as Trichosporon species. Therefore, care should be taken regarding the possibility of trichosporonosis in patients receiving micafungin with or without amphotericin B.

Non-comparative evaluation of the safety of aerosolized amphotericin B lipid complex in patients undergoing allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplant (HSCT) recipients are at increased risk for invasive fungal infections (IFIs) over prolonged periods of time. Aerosolized amphotericin B lipid complex (ABLC) has shown promise in lung transplant recipients as a convenient means of delivering protective drug to the upper airways avoiding systemic toxicities. The safety and tolerability of aerosolized ABLC in 40 subjects undergoing allogeneic HSCT was prospectively investigated in an open-labeled, non-comparative study. Subjects received aerosolized ABLC treatment once daily for 4 days, then once weekly for 13 weeks; fluconazole was administered daily as standard of care through post-transplant day 100. Pulmonary mechanics were measured before and after each dose of inhaled ABLC; adverse events (AEs) and the development of IFI were also monitored. Cough, nausea, taste disturbance, or vomiting followed 2.2% of 458 total inhaled ABLC administrations; 5.2% of inhaled ABLC administrations were associated with >or=20% decrease in pulmonary function measurements (forced expiratory volume in 1 second or forced vital capacity) and none required treatment with bronchodilators or withdrawal from study. Four mild AEs were considered possibly or probably related to study treatment; no deaths or withdrawals from treatment were attributed to study drug. Of 3 proven IFIs occurring during the study period, only 1, a catheter-related case of disseminated fusariosis, occurred while the subject was receiving study medication. Aerosolized ABLC was well tolerated in allogeneic HSCT recipients. With only 1 of 40 subjects developing IFI while receiving treatment, the combination of fluconazole and inhaled ABLC warrants further study as antifungal prophylaxis following allogeneic HSCT.

Fluconazole for the management of invasive candidiasis: where do we stand after 15 years?

Candida spp. are responsible for most of the fungal infections in humans. Available since 1990, fluconazole is well established as a leading drug in the setting of prevention and treatment of mucosal and invasive candidiasis. Fluconazole displays predictable pharmacokinetics and an excellent tolerance profile in all groups, including the elderly and children. Fluconazole is a fungistatic drug against yeasts and lacks activity against moulds. Candida krusei is intrinsically resistant to fluconazole, and other species, notably Candida glabrata, often manifest reduced susceptibility. Emergence of azole-resistant strains as well as discovery of new antifungal drugs (new triazoles and echinocandins) have raised important questions about its use as a first line drug. The aim of this review is to summarize the main available data on the position of fluconazole in the prophylaxis or curative treatment of invasive Candida spp. infections. Fluconazole is still a major drug for antifungal prophylaxis in the setting of transplantation (solid organ and bone marrow), intensive care unit, and in neutropenic patients. Prophylactic fluconazole still has a place in HIV-positive patients in viro-immunological failure with recurrent mucosal candidiasis. Fluconazole can be used in adult neutropenic patients with systemic candidiasis, as long as the species identified is a priori susceptible. Among non-neutropenic patients with candidaemia fluconazole is one of the first line drugs for susceptible species. Cases reports and uncontrolled studies have also reported its efficacy in the setting of osteoarthritis, endophthalmitis, meningitis, endocarditis and peritonitis caused by Candida spp. among immunocompetent adults. In paediatrics, fluconazole is a well tolerated and major prophylactic drug for high-risk neonates, as well as an alternative treatment for neonatal candidiasis. Importantly 15 years after its introduction in the antifungal armamentarium, fluconazole is still a first line treatment option in several cases of invasive candidiasis. Its prophylactic use should however be limited to selected high-risk patients to limit the risk of emergence of azole-resistant strains.

Of Yeasts and Hyphae: A Hematologist’s Approach to Antifungal Therapy

Improvements in anticancer treatments, the ability to modify myelosuppression profiles, greater duration and intensity of immunosuppression, and the variety of available antimicrobial therapies have influenced the spectrum of pathogens associated with invasive fungal infection complicating treatment of hematological malignancies and hematopoietic stem cell transplantation. The approaches to the management of these infections encompass strategies of prevention for all those at risk, pre-emptive therapy based upon surrogates of infection before the onset of clinical disease, empirical therapy for patients with clinical evidence of early disease, and directed or targeted therapy for infected patients with established disease. Chemoprophylaxis is effective if applied to the highest risk patients over the duration of the risk. Pre-emptive strategies, while promising, have yet to be validated and linked to reliably predictive nonmicrobiological diagnostic techniques. Empirical antifungal therapy, as it is currently applied, now seems questionable. Patients with probable or proven invasive fungal infection still have suboptimal outcomes despite the availability of promising anti-fungal agents. Strategies examining the concept of dose-intensity and combination regimens require careful study and cannot yet be regarded as an acceptable standard of practice.

Effective Blood Concentration of Micafungin for Pulmonary Aspergillosis

We previously reported that a 150 mg or higher daily dose is necessary for treatment of pulmonary aspergillosis with micafungin (MCFG) alone in patients with blood diseases. Since a delay in the treatment of pulmonary aspergillosis has a major influence on patient survival, clarification of the effective blood concentration of MCFG enables rapid treatment. Establishment of an appropriate dose is also useful for reducing the risk of adverse effects, such as MCFG-induced impairment of liver function. Aiming for the rapid and safe treatment of pulmonary aspergillosis, we established new clinical diagnostic criteria of mycosis and MCFG therapeutic effect judgment criteria, and investigated the effective blood concentration of MCFG for mycosis. The blood trough level of MCFG in patients with blood diseases at each clinical improvement rating of pulmonary aspergillosis was 5.23+/-2.44 microg/ml in markedly improved cases, 4.08+/-2.63 microg/ml in improved cases, and 3.45+/-1.63 microg/ml in successfully prevented cases, showing no significant difference among the 3 groups. Based on this finding, it is advisable to target a 5 microg/ml or higher blood trough level of MCFG in establishing the dose for aspergillosis in patients with blood diseases.

Role of new antifungal agents in prophylaxis of mycoses in high risk patients

PURPOSE OF REVIEW

For pancreas, liver, and hematopoietic stem cell transplant recipients, no antifungal prophylaxis led to a high rate of and high morbidity from fungal infection. With the use of fluconazole as prophylaxis since the early 1990s, there have been shifts in the types of infecting fungal pathogens, documentation of resistance among fungal organisms, and changes in transplant practices. The aim of this article is to review recent clinical trials regarding antifungal chemoprophylaxis among several populations of high risk patients.

RECENT FINDINGS

Itraconazole, micafungin, and posaconazole have been studied as alternatives to fluconazole prophylaxis. Itraconazole showed no dramatic improvement over fluconazole as prophylaxis during liver and hematopoietic stem cell transplantation, primarily due to gastrointestinal side effects. In addition, detrimental changes to cyclophosphamide metabolism were noted for hematopoietic stem cell transplant recipients. Micafungin was superior to fluconazole during the pre-engraftment period of hematopoietic stem cell transplantation, because it was able to prevent mold infections, required less switches to empirical antifungal therapy, and functioned as well as fluconazole in preventing yeast infections. Posaconazole was compared to fluconazole during a 16-week prophylaxis period during graft-versus-host disease, but results of this study are still forthcoming. Aerosolized amphotericin products appear to be safe for lung transplant recipients.

SUMMARY

Fluconazole remains the standard agent for prophylaxis against invasive fungal infections for pancreas, liver, and hematopoietic stem cell transplant recipients. Micafungin is superior to fluconazole with minimal toxicity for use in the pre-engraftment period of hematopoietic stem cell transplantation. The optimal agent for prophylaxis later following transplant, if mold coverage is desired during prolonged immunosuppression, has not been determined.

New antifungal agents under development in children and neonates

PURPOSE OF REVIEW

This review focuses on only the newest antifungal agents recently approved or still under development and the available data in pediatric and neonatal patients. The larger body of data in adult patients is used for comparative purposes only in an attempt to understand pediatric implications.

RECENT FINDINGS

Pharmacokinetic data suggest differences in dosing for many newer agents in children versus adult patients, but each agent has not been fully evaluated. Voriconazole displays non-linear pharmacokinetics in adults but has linear pharmacokinetics in children, necessitating a higher dose in smaller patients and potential treatment failures using the approved adult dosing schedule. Caspofungin likewise requires higher doses relative to adult patients, and dosing in children is best accomplished on a body surface area scheme and not a body weight dosing platform. Preliminary data suggest posaconazole, an investigational triazole, in children may lead to similar levels as in adults, but very limited efficacy data are available at any dose. Micafungin dosing has been explored in neonatal patients and there is a clear trend toward lower levels obtained in the very smallest infants, highlighting the importance of the neonatal period as a separate entity to even the pediatric age group.

SUMMARY

Initial data suggest dosing differences in children with some antifungals, and other newer agents have not been fully tested for the correct dosing. The underlying concern of efficacy in children compared with adult patients has never been answered as there are no randomized, phase III antifungal clinical trials from which pediatric-specific data were obtained.

International, open-label, noncomparative, clinical trial of micafungin alone and in combination for treatment of newly diagnosed and refractory candidemia

Candida spp. are the fourth leading cause of bloodstream infections, and non-albicans species are increasing in importance. Micafungin is a new echinocandin antifungal agent with excellent in vitro activity against Candida spp. Pediatric, neonatal, and adult patients with new or refractory candidemia were enrolled into this open-label, noncomparative, international study. The initial dose of micafungin was 50 mg/d (1 mg/kg for patients <40 kg) for infections due to C. albicans and 100 mg/d (2 mg/kg for patients <40 kg) for infections due to other species. Dose escalation was allowed. Maximum length of therapy was 42 days. A total of 126 patients were evaluable (received at least five doses of micafungin). Success (complete or partial response) was seen in 83.3% patients overall. Success rates for treatment of infections caused by the most common Candida spp. were as follows: C. albicans 85.1%, C. glabrata 93.8%, C. parapsilosis 86.4%, and C. tropicalis 83.3%. Serious adverse events related to micafungin were uncommon. Micafungin shows promise as a safe and effective agent for the treatment of newly diagnosed and refractory cases of candidemia. Large-scale, randomized, controlled trials are warranted.

Advances and challenges in management of invasive mycoses

Invasive mycoses pose a major diagnostic and therapeutic challenge. Advances in antifungal agents and diagnostic methods offer the potential for improved outcomes in patients with these infections, which are often lethal. Many fungal pathogens occur almost exclusively in opportunistic settings--in the immunocompromised host--and these infections are the focus of this review. Several areas of ongoing challenge remain, including the emergence of resistant organisms and the absence of reliable markers for early identification of patients at risk of developing invasive fungal disease. This Seminar reviews the changing epidemiology of invasive mycoses, new diagnostic methods, and recent therapeutic options and current management strategies for these opportunistic pathogens.

Echinocandins: role in antifungal therapy, 2005

Novel therapies to treat invasive fungal infections have revolutionised the care of patients with candidiasis, aspergillosis and other less common fungal infections. Physicians in the twenty first century have access to safer versions of conventional drugs (i.e., lipid amphotericin B products), extended-spectrum versions of established drugs (i.e., voriconazole), as well as a new class of antifungal agents; the echinocandins. The increased number of options in the antifungal armamentarium is well timed, as the incidence of both invasive candidiasis and invasive aspergillosis, and the financial burden associated with these infections, have increased significantly in the past several decades. The increasing incidence of fungal infections has risen in parallel with the increase in critically ill and immunocompromised patients. Candida is the fourth most common bloodstream isolate, approximately 50% of which are non-albicans species. Estimates suggest there to be 9.8 episodes of invasive candidiasis per 1000 admissions to surgical intensive care units, with attributable mortality at 30% and cost per episode of US44,000 dollars. The burden of candidiasis is even higher in the paediatric population, with Candida being the second most common bloodstream infection. The increase in non-albicans candidiasis mandates the introduction of new antifungal agents capable of treating these often azole-resistant isolates. In addition, there has been a rise in the incidence of invasive aspergillosis, the most common invasive mould infection following haematopoietic stem cell transplantation, with an estimated incidence of 10 - 20%. The mortality associated with invasive aspergillosis has increased by 357% since 1980. Unfortunately, the overall survival rate among patients treated with amphotericin B, and even voriconazole, remains suboptimal, as evidenced by the failure of treatment in 47% of patients in the landmark voriconazole versus amphotericin B trial. Given the increasing incidence and suboptimal outcomes of these serious fungal infections, novel therapies represent an opportunity for significant advancement in clinical care. The current challenge is to discover the optimal place for the echinocandins in the treatment of invasive fungal infections.

New agents for the prevention of opportunistic infections in haematopoietic stem cell transplant recipients

Over the past three decades, autologous and allogeneic haematopoietic stem cell transplants (HSCTs) have become effective treatments for a variety of malignant and nonmalignant conditions. Patients who undergo HSCT receive high doses of chemotherapy and/or radiation that induce a prolonged period of profound immunodeficiency, placing them at high risk for infection from a panoply of opportunistic organisms. Although supportive treatment for these patients has markedly improved, 10-20% of allogeneic HSCT recipients will ultimately succumb to infection. Joint guidelines to prevent opportunistic infection were released in 2000 by the Centers for Disease Control, the Infectious Diseases Society of America, and the American Society of Blood and Marrow Transplantation; however, treatment decisions for these patients are often based on limited studies or depend on institution-specific transplant protocols and antibiotic resistance patterns. This paper will discuss new agents for preventing bacterial, fungal and viral infections in HSCT recipients.

Micafungin Sodium

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Safety, tolerability, and pharmacokinetics of Micafungin (FK463) in febrile neutropenic pediatric patients

Micafungin (FK463) is a new parenteral echinocandin. A multicenter, phase I, open-label, sequential-group dose escalation study was conducted to assess the safety, tolerability, and pharmacokinetics of micafungin in neutropenic pediatric patients. A total of 77 patients stratified by age (2 to 12 and 13 to 17 years) received micafungin. Therapy was initiated at 0.5 mg/kg per day and escalated to higher dose levels of 1.0, 1.5, 2.0, 3.0, and 4.0 mg/kg per day. Micafungin was administered within 24 h of initiating broad-spectrum antibacterial antibiotics for the new onset of fever and neutropenia. The most common overall adverse events in the study population were diarrhea (19.5%), epistaxis (18.2%), abdominal pain (16.9%), and headache (16.9%). Nine patients (12%) experienced adverse events considered by the investigator to be possibly related to the study drug. The most common related events were diarrhea, vomiting, and headache, all occurring in two patients each. There was no evidence of a dose-limiting toxicity as defined within the prespecified criteria of this clinical protocol. There was one death during the study due to septic shock. The pharmacokinetic profiles for micafungin over the 0.5- to 4.0-mg/kg dose range demonstrated dose linearity. Clearance, volume of distribution, and half-life remained relatively constant over the dose range and did not change with repeated administration. The overall plasma pharmacokinetic profile was similar to that observed in adults. However, there was an inverse relation between age and clearance. For patients 2 to 8 years old, clearance was approximately 1.35 times that of patients >/=9 years of age. In summary, micafungin over a dosage range between 0.5 and 4.0 mg/kg/day in 77 febrile neutropenic pediatric patients displayed linear pharmacokinetics and increased clearance as a function of decreasing age.

Changing face of health-care associated fungal infections

PURPOSE OF REVIEW

The purpose of this review was to evaluate recent publications on the epidemiology, diagnosis and management of invasive fungal infections.

RECENT FINDINGS

Epidemiological surveys have highlighted significant differences between Europe and the United States regarding the incidence and etiology of Candida bloodstream infections. Today, invasive aspergillosis is occurring in a much broader patient population than the classical immunocompromised hosts and includes mechanically ventilated intensive care unit patients and patients receiving corticosteroids for treatment of chronic lung diseases. Diagnosis is often delayed in these patients and prognosis is dismal. Measurement of galactomannan, mannan and antimannan antibodies, and beta-(1-3)-D-glucan may help to speed up diagnosis. The epidemiology of invasive mold infections is changing. The frequency of non-fumigatus Aspergillus species is increasing, uncommon hyalo-or phaeo-hyphomycoses are emerging and breakthrough mold infections intrinsically resistant to azoles have been reported. Clinical trials have shown that new azoles and echinocandins are as efficacious as amphotericin B or fluconazole for the treatment of eosophageal or invasive candidiasis, for prophylaxis of invasive fungal infections in transplant patients, or for empirical antifungal therapy in patients with persistent fever and neutropenia.

SUMMARY

Recent data suggest that the epidemiology of invasive fungal infections may be changing with the emergence of uncommon molds and the occurrence of invasive aspergillosis in 'nonclassical' immunocompromised hosts. New diagnostic tools and improved antifungal agents are available to facilitate early diagnosis and offer new treatment options.

Antifungal agents in children

Fungal pathogens are an increasingly recognized complication of organ transplantation and the ever more potent chemotherapeutic regimens for childhood malignancies. This article provides a brief overview of the current state of systemic antifungal therapy. Currently licensed drugs, including amphotericin B and its lipid derivates; 5-fluorocytosine; the azoles, including fluconazole, itraconazole, and voriconazole; and a representative of the new class of echinocandin agents, caspofungin, are discussed. Newer second-generation azoles (posaconazole and ravuconazole) and echinocandins (micafungin and anidulafungin) that are likely to be licensed in the United States in the next few years also are addressed.

Pharmacokinetic and maximum tolerated dose study of micafungin in combination with fluconazole versus fluconazole alone for prophylaxis of fungal infections in adult patients undergoing a bone marrow or peripheral stem cell transplant

In this dose escalation study, 74 adult cancer patients undergoing bone marrow or peripheral blood stem cell transplantation received fluconazole (400 mg/day) and either normal saline (control) (12 subjects) or micafungin (12.5 to 200 mg/day) (62 subjects) for up to 4 weeks. The maximum tolerated dose (MTD) of micafungin was not reached, based on the development of Southwest Oncology Group criteria for grade 3 toxicity; drug-related toxicities were rare. Commonly occurring adverse events considered related to micafungin were headache (6.8%), arthralgia (6.8%), hypophosphatemia (4.1%), insomnia (4.1%), maculopapular rash (4.1%), and rash (4.1%). Pharmacokinetic profiles for micafungin on days 1 and 7 were similar. The mean half-life was approximately 13 h, with little variance after repeated or increasing doses. Mean maximum concentrations of the drug in serum and areas under the concentration-time curve from 0 to 24 h were approximately proportional to dose. There was no clinical or kinetic evidence of interaction between micafungin and fluconazole. Five of 12 patients (42%) in the control group and 14 of 62 (23%) in the micafungin-plus-fluconazole groups had a suspected fungal infection during treatment which resulted in empirical treatment with amphotericin B. The combination of micafungin and fluconazole was found to be safe in this high-risk patient population. The MTD of micafungin was not reached even at doses up to 200 mg/day for 4 weeks. The pharmacokinetic profile of micafungin in adult cancer patients with blood or marrow transplants is consistent with the profile in healthy volunteers, and the area under the curve is proportional to dose.

Micafungin: pharmacology, experimental therapeutics and clinical applications

Invasive fungal infections are important causes of morbidity and mortality in hospitalised patients. Current therapy with amphotericin B and antifungal triazoles has overlapping targets and is limited by toxicity and resistance. Echinocandins are a new class of antifungal drugs, which inhibit the synthesis of 1,3-beta-D-glucan. This homopolysaccharide is an important component of the cell wall of many pathogenic fungi, providing osmotic stability and functioning in cell growth and cell division. Micafungin, which is a member of the echinocandin class, exhibits in vitro fungicidal or fungistatic activity against a variety of fungal pathogens which include Candida and Aspergillus species but not Cryptococcus, Fusarium or Zygomycetes. Micafungin demonstrates linear pharmacokinetics, which are not altered by drugs metabolised through the P450 enzyme system. The preclinical and clinical data strongly support the development of micafungin for treatment of proven or suspected mucosal and invasive Candida infections in immunocompetent and immunocompromised patients. This paper reviews the preclinical and clinical pharmacology of micafungin and its potential role for treatment of fungal invasive infections in patients.

A randomized, double blind, comparative trial of micafungin (FK463) vs. fluconazole for the treatment of oesophageal candidiasis

AIM

To determine efficacy and safety of intravenous micafungin vs. intravenous fluconazole in the treatment of oesophageal candidiasis.

METHODS

A total of 523 patients > or =16 years with documented oesophageal candidiasis were randomized (1:1) in this controlled, non-inferiority study to receive either micafungin (150 mg/day) or fluconazole (200 mg/day). Response was evaluated clinically and endoscopically. Post-treatment assessments were performed at 2 and 4 weeks after discontinuation of therapy.

RESULTS

Median duration of therapy was 14 days. For the primary end-point of endoscopic cure, treatment difference was -0.3% (micafungin 87.7%, fluconazole 88.0%). Documented persistent invasive disease at the end of therapy was reported in 2.7% and 3.9% of patients, respectively. Both 84.8% of micafungin and 88.7% of fluconazole patients remained recurrence free at 4-weeks post-treatment. The overall therapeutic response rate was 87.3% for micafungin and 87.2% for fluconazole. The incidence of drug-related adverse events was 27.7% for micafungin and 21.3% for fluconazole. Six (2.3%) micafungin- and two (0.8%) fluconazole-treated patients discontinued therapy; rash was the most common event leading to discontinuation.

CONCLUSION

Intravenous micafungin (150 mg daily) is well tolerated and as efficacious as intravenous fluconazole (200 mg daily) in the primary treatment of oesophageal candidiasis, achieving high rates of clinical and endoscopic cure.

Aspergillus infections in transplant recipients

Aspergillus infections are occurring with an increasing frequency in transplant recipients. Notable changes in the epidemiologic characteristics of this infection have occurred; these include a change in risk factors and later onset of infection. Management of invasive aspergillosis continues to be challenging, and the mortality rate, despite the use of newer antifungal agents, remains unacceptably high. Performing molecular studies to discern new targets for antifungal activity, identifying signaling pathways that may be amenable to immunologic interventions, assessing combination regimens of antifungal agents or combining antifungal agents with modulation of the host defense mechanisms, and devising diagnostic assays that can rapidly and reliably diagnose infections represent areas for future investigations that may lead to further improvement in outcomes.

Long-term antifungal prophylaxis in high-risk hematopoietic stem cell transplant recipients

The risks for invasive fungal infections, particularly mould infections such as invasive aspergillosis, among hematopoietic stem cell transplant (HSCT) recipients are linked to the duration and severity of myelosuppression and immunosuppression. Strategies to prevent invasive fungal infections have focused primarily on the use of orally administered azole antifungal agents during the neutropenic period rather than on the more prolonged post-engraftment period. The major limitations of these studies included the heterogeneity among the subjects studied for fungal infection risk factors, the agents administered, the dosing, and duration of prophylaxis. More recent studies have attempted to examine the efficacy of antifungal prophylaxis strategies among allogeneic HSCT recipients to day 100 and beyond. It is clear that a variety of products have efficacy in preventing invasive candidiasis, including imidazole and triazole antifungals, low-dose amphotericin B, and the echinocandin, micafungin; however, only the extended spectrum azole, itraconazole, has been shown to impact the incidence of proven invasive aspergillosis. Other extended spectrum azole antifungal agents, voriconazole and posaconazole, are being studied as long-term prophylaxis in high-risk HSCT recipients. While clinical trials have suggested that a duration of prophylaxis against moulds of six months or more may be required, it remains unclear if this is required in all cases. The prophylactic efficacy over time may be linked to the degree of immunosuppression as measured by markers such as the numbers of circulating CD4 T lymphocytes. Concerns about selection for resistant moulds among long-term recipients of these drugs are emerging. The cumulative experience to date suggests that long-term antifungal chemoprophylaxis is feasible and effective when applied in defined circumstances. The concerns about treatment-related toxicities, resistance, and costs are valid.