Compartmental pharmacokinetics and tissue distribution of the antifungal echinocandin lipopeptide micafungin (FK463) in rabbits

Pharmacokinetics of antifungal agents in children

Invasive fungal infections in immunocompromised children are common and often fatal. The first antifungal agents such as amphotericin B and fluconazole offered effective treatment, but their use was often limited by toxicity and resistance. Numerous new antifungal agents have since been developed and appear to be as effective. Most dosing and safety trials have been done in adults, and extrapolation of this data to children has proven inadequate. We reviewed the literature regarding the pharmacokinetics/pharmacodynamics (PK/PD) and safety of antifungal agents with an emphasis on the newer azoles and echinocandins. From a small but growing number of PK/PD trials, better dosing guidelines have been developed.

Human tissue distribution of voriconazole

Voriconazole concentrations were determined in autopsy samples of eight patients who had been treated for a median of 7 days (interquartile range [IQR], 5 days). Voriconazole penetrates well into various tissues, with median levels of 6.26 μg/g ((interquartile range [IQR], 7.87 μg/g) in the lung, 3.41 μg/g (IQR, 16.72 μg/g) in the brain, 6.89 μg/g (IQR, 24.16 μg/g) in the liver, 6.47 μg/g (IQR, 6.19 μg/g) in the kidneys, 5.60 μg/g (IQR, 11.49 μg/g) in the spleen, and 7.55 μg/g (IQR, 16.91 μg/g) in the myocardium.

Micafungin concentrations from brain tissue and pancreatic pseudocyst fluid

We report the attainment of micafungin concentrations from brain tissue and pancreatic pseudocyst fluid from two patients with invasive candidiasis. Micafungin was present in low levels at both body sites, indicating limited penetration into central nervous system (CNS) tissue and pancreatic fluid. Further studies are needed to fully characterize its pharmacokinetics at these locations, as micafungin may potentially serve as an alternative antifungal therapy for CNS or pancreatic candidal infections for which the currently recommended first-line therapy fails.

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

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

Endogenous ocular candidiasis: Changes in epidemiology and factors associated with poor functional outcome

The evolution of the incidence and the epidemiology of ocular candidiasis in our hospital during the past 12 y, as well as the factors associated with poor functional outcome were analysed. A retrospective study of all cases of ocular candidiasis admitted to a university hospital between 1993 and 2004 was performed. Epidemiological, clinical and final outcome data were recorded. 37 episodes of ocular candidiasis in 36 patients were studied. 28 (75%) episodes occurred between 1993 and 1998 (13.09 episodes/100,000 admissions/y), and all of these patients were intravenous drug users. In contrast, only 9 episodes of ocular candidiasis were recorded between 1999 and 2004 (4.42 episodes/100,000 admissions/y; p<.0001) and 3 (33%) patients were not drug users (p<0.01). 19 (57%) cases had final visual acuity <0.1. Treatment with conventional amphotericin B instead of other newer antifungal drugs was associated with poor visual prognosis in the univariate (p = 0.03) and multivariate (p = 0.03) analysis. In conclusion, the incidence of ocular candidiasis has decreased significantly in recent y and the epidemiology has changed. Currently, one-third of patients are immunocompromised non-drug users. Therapy with conventional amphotericin B instead of newer antifungal drugs appears to be associated with a poorer functional outcome.

[Clinical use of micafungin for the treatment of invasive candidiasis in critical ill patients]

BACKGROUND

Over the last 30 years a significant increase of Candida spp. invasive disease has been observed in non-neutropenic critical ill patients. Both fluconazole and amphotericin B have been considered first line treatment for invasive (proven and probable) Candida spp. disease, although the mortality rate is still high.

OBJECTIVES

To review the current data on the use of micafungin for the treatment of Candida invasive disease in critical ill patients.

METHODS

The pharmacologic, mycological and clinical properties of micafungin are reviewed based on current published data. The use and efficacy of micafungin for the treatment of Candida invasive disease in critical ill patients is discussed.

RESULTS AND CONCLUSIONS

To reduce the rate of mortality more effective antifungals and pre-emptive treatment strategies are currently warranted. Candins achieve better results for the treatment of invasive Candida disease in non-neutropenic critical ill patients. Micafungin has a good safety profile (similar to fluconazole). Micafungin is a first line drug for the treatment of invasive Candida disease and may be used as a pre- emptive approach followed by a de-escalating strategy with azoles.

Cerebral aspergillosis: tissue penetration is the key

Cerebral aspergillosis is increasingly recognized in severely immunocompromised patients and, until recently, this type of fungal infection was associated with a mortality approaching 100%. The central nervous system is a protected environment and penetration of drugs across the blood-brain barrier is mainly limited by their molecular size and physicochemical properties, as well as drug interaction with transporter systems (e.g., P-glycoprotein) at the blood-brain barrier. Most antifungal agents are large molecules (>700 Da), which makes sufficient penetration into the central nervous system unlikely. In fact, the available data indicate low levels of most antifungal agents in cerebrospinal fluid and brain tissue, except for fluconazole and voriconazole. Concentrations of voriconazole exceeding inhibitory concentrations for Aspergillus species were found repeatedly in cerebrospinal fluid and brain tissue, including brain abscess material. A recent retrospective study confirmed that voriconazole treatment resulted in improved response and survival rates in patients with cerebral aspergillosis. Data from animal models, which explored escalated doses or combinations of antifungal agents in experimental neuroaspergillosis, suggest that selected combination or dose-escalated therapies might further improve the still unsatisfactory prognosis in this particular type of Aspergillus infection.

Initial characterization of micafungin pulmonary delivery via two different nebulizers and multivariate data analysis of aerosol mass distribution profiles

Pharmaceutical aerosols have been targeted to the lungs for the treatment of asthma and pulmonary infectious diseases successfully. Micafungin (Astellas Pharma US, Deerfield, IL, USA) has been shown to be an effective antifungal agent when administrated intravenously. Pulmonary delivery of micafungin has not previously been reported. In the present pilot study, we characterize the performance of two nebulizers and their potential for delivering micafungin to the lungs as well as the use of multivariate data analysis for mass distribution profile comparison. The concentration of micafungin sodium increased by 21% when delivered by the Acorn II nebulizer and by 20% when delivered by the LC Plus nebulizer, respectively, from the first to the second sampling period. The Acorn II nebulizer delivered a fine particle fraction FPF(5.8) (%<5.8 microm) of 92.5 +/- 0.8 and FPF(3.3) (%<3.3 microm) of 82.3 +/- 2.1 during the first sampling period. For the LC Plus nebulizer, FPF(5.8) was 92.3 +/- 0.1 and FPF(3.3) was 67.0 +/- 0.7 during the first sampling period. The mass median aerodynamic diameter (MMAD) increased from 1.67 +/- 0.05 to 1.77 +/- 0.04 mum (Acorn II nebulizer) and from 2.09 +/- 0.01 to 2.20 +/- 0.01 microm (Pari LC Plus nebulizer) from the first to the second sampling periods. These changes in MMAD were statistically significant by paired t test. Multivariate data analysis showed that this could be explained systematically by greater drug deposition on stages with larger cutoff sizes and reduced drug deposition on stages with smaller cutoff sizes rather than multimodal deposition or other anomalies in size distribution.

Bronchopulmonary disposition of micafungin in healthy adult volunteers

By way of bronchoscopy and bronchoalveolar lavage, intrapulmonary steady-state concentrations of micafungin administered at 150 mg daily to 15 healthy volunteers were determined at 4, 12, and 24 h after the third dose. The micafungin disposition was predominantly intracellular, with approximately 106% penetration into alveolar macrophages and 5% penetration into epithelial lining fluid.

Cerebrospinal fluid and plasma (1-->3)-beta-D-glucan as surrogate markers for detection and monitoring of therapeutic response in experimental hematogenous Candida meningoencephalitis

The treatment, diagnosis and therapeutic monitoring of hematogenous Candida meningoencephalitis (HCME) are not well understood. We therefore studied the expression of (1-->3)-beta-D-glucan (beta-glucan) in cerebrospinal fluid (CSF) and plasma in a nonneutropenic rabbit model of experimental HCME treated with micafungin and amphotericin B. Groups studied consisted of micafungin (0.5 to 32 mg/kg) and amphotericin B (1 mg/kg) treatment groups and the untreated controls (UC). Despite well-established infection in the cerebrum, cerebellum, choroid, vitreous humor (10(2) to 10(3) CFU/ml), spinal cord, and meninges (10 to 10(2) CFU/g), only 8.1% of UC CSF cultures were positive. By comparison, all 25 UC CSF samples tested for beta-glucan were positive (755 to 7,750 pg/ml) (P < 0.001). The therapeutic response in CNS tissue was site dependent, with significant decreases of the fungal burden in the cerebrum and cerebellum starting at 8 mg/kg, in the meninges at 2 mg/kg, and in the vitreous humor at 4 mg/kg. A dosage of 24 mg/kg was required to achieve a significant effect in the spinal cord and choroid. Clearance of Candida albicans from blood cultures was not predictive of eradication of organisms from the CNS; conversely, beta-glucan levels in CSF were predictive of the therapeutic response. A significant decrease of beta-glucan concentrations in CSF, in comparison to that for UC, started at 0.5 mg/kg (P < 0.001). Levels of plasma beta-glucan were lower than levels in simultaneously obtained CSF (P < 0.05). CSF beta-glucan levels correlated in a dose-dependent pattern with therapeutic responses and with Candida infection in cerebral tissue (r = 0.842). Micafungin demonstrated dose-dependent and site-dependent activity against HCME. CSF beta-glucan may be a useful biomarker for detection and monitoring of therapeutic response in HCME.

Ocular distribution of intravenously administered micafungin in rabbits

The ocular distribution of micafungin (MCFG), which has antifungal activity against Candida and Aspergillus species, was followed after the systemic administration of MCFG in rabbits. After MCFG (10 mg/kg) plus fluconazole (FLCZ; 10 mg/kg) was administered intravenously, the rabbits were killed, and MCFG and FLCZ concentrations in retina-choroid, vitreous humor, and plasma were determined by high performance liquid chromatography or liquid chromatography/mass spectrometry. The mean concentrations of MCFG in the retina-choroid at 0.25, 0.75, 4, 8, and 24 h after administration were 20.18, 15.97, 13.19, 6.27, and 0.75 microg/g, respectively, and were comparable with the MCFG plasma concentrations. The MCFG concentrations in retina-choroid and plasma exceeded the minimal antifungal inhibitory concentrations for endophthalmitis, although MCFG was not detected in the vitreous humor. These results suggest that the intravenous administration of MCFG is an effective treatment for endogenous fungal endophthalmitis when the causative fungus is localized in the retina and choroid.

A case of invasive central nervous system aspergillosis treated with micafungin with monitoring of micafungin concentrations in the cerebrospinal fluid

Invasive aspergillosis has an extremely high mortality rate. In Japan, micafungin, an echinocandin drug that has a new mechanism of action as an antifungal agent and has a clinical effect against Aspergillus species, became available in 2002. However, little is known about its penetration into the central nervous system (CNS), or its efficacy for the treatment of invasive CNS aspergillosis. We report a 65-y-old female with diabetes mellitus and CNS aspergillosis who was treated with micafungin. During treatment, micafungin concentrations were measured in the cerebrospinal fluid and plasma. On a dose of 300 mg/d, the ratio of the micafungin concentration in the cerebrospinal fluid to that in plasma was extremely low (0.2%-0.05%); nevertheless, the patient did not have a relapse of invasive CNS aspergillosis after micafungin treatment.

Micafungin: A New Echinocandin Antifungal

The echinocandins represent the newest class of antifungals to combat infections caused by Candida sp. Micafungin is an echinocandin recently approved by the United States Food and Drug Administration. It is indicated in adults for esophageal candidiasis and prophylaxis against candidal infections in hematopoietic stem cell transplant recipients. Micafungin exhibits in vitro fungicidal activity against Candida sp, including fluconazole-resistant isolates. Its in vivo efficacy is comparable to that of fluconazole in the treatment of esophageal candidiasis and superior to that of fluconazole for prophylaxis of invasive candidal infections. Because it is not significantly metabolized by the cytochrome P450 3A system, micafungin is associated with few drug interactions. Micafungin does not require adjustment in patients with renal and/or hepatic impairment, and it has been shown to be well tolerated in both adult and pediatric patients. Its efficacy against Candida sp, coupled with its overall safety and drug interaction profiles, makes it an attractive option in the treatment against esophageal candidiasis and prophylaxis against invasive candidal infections.

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.

Human pharmacogenomic variations and their implications for antifungal efficacy

Pharmacogenomics is defined as the study of the impacts of heritable traits on pharmacology and toxicology. Candidate genes with potential pharmacogenomic importance include drug transporters involved in absorption and excretion, phase I enzymes (e.g., cytochrome P450-dependent mixed-function oxidases) and phase II enzymes (e.g., glucuronosyltransferases) contributing to metabolism, and those molecules (e.g., albumin, A1-acid glycoprotein, and lipoproteins) involved in the distribution of antifungal compounds. By using the tools of population genetics to define interindividual differences in drug absorption, distribution, metabolism, and excretion, pharmacogenomic models for genetic variations in antifungal pharmacokinetics can be derived. Pharmacogenomic factors may become especially important in the treatment of immunocompromised patients or those with persistent or refractory mycoses that cannot be explained by elevated MICs and where rational dosage optimization of the antifungal agent may be particularly critical. Pharmacogenomics has the potential to shift the paradigm of therapy and to improve the selection of antifungal compounds and adjustment of dosage based upon individual variations in drug absorption, metabolism, and excretion.

Effects of Hepatic CYP3A4 Activity on Disposition of Micafungin in Liver Transplant Recipients With Markedly Small-for-Size Grafts

Micafungin, the first candin antifungal drug developed in Japan, has a significant therapeutic effect against deep-seated mycoses caused by Candida or Aspergillus. Little is known, however, about the optimal dosage or disposition of micafungin in patients with severe hepatic impairment. Nine liver transplant recipients (5 males and 4 females) were enrolled in this study. In 1 recipient with a markedly small-for-size graft (ratio of graft volume to standard liver volume at the time of transplantation: 25.9%), the areas under the plasma concentration-time curves up to 12 hours postdose (AUC(0-12 h)) at doses of 50 and 100 mg/d were 79.38 and 601.17 mug.h/mL, respectively. The corresponding elimination half-life (T(1/2)) values were 16.01 and 75.75 hours, and saturated elimination was observed only at the dose of 100 mg/d. The mean urinary ratio of 6beta-hydroxycortisol to cortisol (6beta-OHF/F) in the small-for-size graft recipient was significantly (P < .05) lower than that in the other recipients. In conclusion, graft size was an important factor affecting disposition of micafungin. For liver transplant recipients with markedly small-for-size grafts, the optimal dosage of micafungin to reach and maintain therapeutic plasma levels is estimated to be 50 mg/d.

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.

[Fungal infection following reduced-intensity stem cell transplantation (RIST)]

Hematopoietic stem cell transplantation has been established as a curative treatment for advanced hematologic malignancies. Transplantation with a reduced-intensity conditioning regimen has been developed, and the minimal toxicity of reduced-intensity stem cell transplantation (RIST) has made this procedure available for patients of advanced age or with organ dysfunction. The response of malignant lymphoma and some solid tumors to RIST has been observed. RIST with unrelated donors and umbilical cord blood has been studied. Fungal infection is an important complication of RIST. Since the prognosis of fungal infection is poor, the management has been focused on its prophylaxis. Given recent progression in RIST management, the strategy of infectious prophylaxis has also changed. Equipment in the hospital is important for fungal infection; however, the median day of the development of fungal infection is day 100, when most patients are followed as outpatients. The focus of fungal management after RIST is oral antifungal agents rather than in-hospital equipment. Various antifungal agents have recently been developed and applied for clinical use, and many of these have been developed simultaneously for the first time. A major change in antifungal management will probably occur in the next several years.

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.

Neonatal candidiasis

In neonates born weighing less than 750 g, invasive candidates is common and often fatal. This situation provides an opportunity to study antifungal prophylaxis and treatment in this patient population, in which the pharmacokinetics, safety, and efficacy of antifungal products are unknown. The disease is less prevalent in larger, more mature, infants. Although some pharmacokinetic data for some products are available for term and near-term infants, optimal product choice, closing, and other treatment strategies also are unknown in this older age group.

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.

Actividad in vitro de las equinocandinas ¿Cómo debe evaluarse?

Echinocandins are a novel class of antifungal drugs. They have good activity against Candida spp and Aspergillus spp. Their low selective toxicity allows their administration at high doses with few secondary side effects. We have reviewed the available data on the endpoints for these drugs in their in vitro susceptibility testing on yeasts and moulds. The microdilution broth method is the most commonly used technique and MIC-1 (80% of growth inhibition) seems to be the most reliable endpoint when yeasts are tested. This endpoint also seems to be the most appropriate for the different drugs when they are combined with echinocandins using the checkerboard method for testing yeasts. By contrast, in the case of moulds, the minimum effective concentration (MEC) correlates better with the in vivo activity than the MIC when echinocandins are tested, and when these drugs are combined with other antifungals, MIC-2 (50% of growth inhibition) seems the most appropriate endpoint. Criteria based on drug pharmacodynamics is the most useful to define the echinocandin endpoints that best correlate with their in vivo efficacy.

In vitro interactions of micafungin with other antifungal drugs against clinical isolates of four species of Cryptococcus

The combination of micafungin (MFG) with amphotericin B (AMB), fluconazole, itraconazole, voriconazole, or ravuconazole was evaluated against 37 strains of four species of Cryptococcus by the checkerboard method. Antagonism was never seen. Synergy was observed for some isolates for each combination and was most frequent with MFG-AMB.

Subtherapeutic Ocular Penetration of Caspofungin and Associated Treatment Failure in Candida albicans Endophthalmitis

Candida endophthalmitis represents the most serious ocular complication of candidemia. The pharmacokinetics and pharmacodynamics of fluconazole, amphotericin B, and flucytosine are fairly well established in endophthalmitis therapy. There remains a paucity of clinical data regarding the utility of new antimycotic agents in the treatment of fungal chorioretinitis and endophthalmitis. We report a case of clinical failure of caspofungin in the management of Candida albicans endophthalmitis associated with poor vitreous penetration.

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.

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.

Candida glabrata Endophthalmitis Treated Successfully with Caspofungin

A 39-year-old man with Candida glabrata endophthalmitis was successfully treated with a 28-day course of intravenous caspofungin. Presence of underlying renal insufficiency and infection with a drug-resistant strain precluded use of amphotericin B or fluconazole. Intravitreal administration of antifungals and vitrectomy were not required. The role of caspofungin in Candida endophthalmitis is discussed.

New agents for invasive mycoses in children

PURPOSE OF REVIEW

Invasive fungal infections are an important cause of morbidity and mortality in immunocompromised children of all ages. This review summarizes information on new antifungal agents, including current data on their clinical use in children, as well as alternative strategies such as antifungal combination and immunomodulation therapy.

RECENT FINDINGS

Novel antifungal agents, such as the echinocandins and the second-generation triazoles, were recently introduced that exhibit promising efficacy against Candida spp., Aspergillus spp., and other opportunistic fungal pathogens. These compounds are generally well tolerated and show substantial efficacy as salvage treatment and equal or even superior efficacy compared with older azoles or amphotericin B as first-line or empiric therapy for fungal infections. Clinical studies of pharmacokinetics and efficacy of the new agents in the pediatric population are, however, limited.

SUMMARY

The response rates observed with the recently introduced drugs, although superior in some cases compared with older antifungal agents, are still far from satisfactory. The development of new antifungal compounds as well as the use of alternative approaches of combination therapy and immunomodulation should be pursued through well-designed laboratory and clinical studies in pediatric patients.

Retinal Function Assessed by ERG Before and After Induction of Ocular Aspergillosis and Treatment by the Anti-fungal, Micafungin, in Rabbits

This study was conducted to evaluate the effectiveness of a new antifungal drug, micafungin, and standard antifungal drugs against endophthalmitis induced in a rabbit by intravitreal injection of Aspergillus fumigatus, an important fungal pathogen. Effectiveness was evaluated by the preservation of b-wave amplitude at 72 h after injection of the fungus relative to the b-wave amplitude at baseline before any intravitreal injections. A 0.06 ml inoculum of 10(6) conidia of A. fumigatus was injected into the vitreous of the right eye of all rabbits; and, 12 h later, a 0.06 ml solution containing one of 3 antifungal drugs or saline was injected into the vitreous of both eyes. All three antifungal drugs produced significant b-wave preservation at 72 h in infected eyes compared to that in infected eyes receiving saline injections. There was no statistically significant difference between the effects of micafungin and amphotericin B in the right eyes with fungal endophthalmitis, and both produced significantly more preservation of b-wave amplitude than voriconazole. Amphotericin B, but neither micafungin nor voriconazole produced significant reduction of the b-wave amplitude in the left eyes.

Optimal prophylactic dosage and disposition of micafungin in living donor liver recipients

Micafungin, a new candin antifungal drug, has a good safety profile and a significant therapeutic effect against Candida and Aspergillus. Little is known, however, about the optimal prophylactic dosage and the disposition of micafungin in liver transplant recipients, or about the effect of continuous venovenous hemodialysis (CVVH) on the pharmacokinetics of micafungin. Six living donor liver transplant patients were enrolled in this study. The mean C(max) and C(min) (trough) values of micafungin in plasma were 6.31 +/- 1.08 and 1.65 +/- 0.54 microg/mL, respectively. The mean elimination half-life (t(1/2)) and mean area under the curve up to 12 h post-dosing (AUC 0-12 h) were 13.63 +/- 2.77 h and 50.04 +/- 6.48 microg.h/mL, respectively. The concentrations of micafungin at the inlet and outlet of the dialyzer were very similar. The mean (+/-SD) ratio of micafungin concentrations at the inlet and outlet of the dialyzer (coutlet/cinlet) and the clearance of micafungin were 0.96 +/- 0.04 and 0.054 +/- 0.04 mL/min/kg, respectively. The amount in the ultrafiltrate was 1.0 mg. Micafungin effectively prevents systemic fungal infection in patients who have undergone liver transplantation. No significant differences were observed in the disposition of micafungin in recipients, and the therapeutic drug level can be achieved by administration of micafungin at a dosage of 40-50 mg/d. The CVVH had little effect on micafungin kinetics, and no dose adjustment or modification of dosing interval was needed during CVVH.

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

We hypothesized that chemoprophylaxis with the echinocandin micafungin would be an effective agent for antifungal prophylaxis during neutropenia in patients undergoing hematopoietic stem cell transplantation (HSCT). We therefore conducted a randomized, double-blind, multi-institutional, comparative phase III trial, involving 882 adult and pediatric patients, of 50 mg of micafungin (1 mg/kg for patients weighing <50 kg) and 400 mg of fluconazole (8 mg/kg for patients weighing <50 kg) administered once per day. Success was defined as the absence of suspected, proven, or probable invasive fungal infection (IFI) through the end of therapy and as the absence of proven or probable IFI through the end of the 4-week period after treatment. The overall efficacy of micafungin was superior to that of fluconazole as antifungal prophylaxis during the neutropenic phase after HSCT (80.0% in the micafungin arm vs. 73.5% in the fluconazole arm [difference, 6.5%]; 95% confidence interval, 0.9%-12%; P=.03). This randomized trial demonstrates the efficacy of an echinocandin for antifungal prophylaxis in neutropenic patients.

Micafungin

Micafungin, an echinocandin antifungal agent with a novel mechanism of action, inhibits beta-(1,3)-D-glucan synthase interfering with fungal cell wall synthesis. It shows excellent antifungal activity against a broad range of Candida spp., including azole-resistant strains, and Aspergillus spp. in in vitro and animal studies. In HIV-positive patients, intravenous micafungin 50-150 mg/day dose-dependently eradicated endoscopically confirmed oesophageal candidiasis, with micafungin 100 and 150 mg/day being more effective than micafungin 50 mg/day and as effective as fluconazole 200 mg/day in a double-blind trial. In nonblind trials, micafungin (monotherapy or combination therapy) was effective against invasive aspergillosis, candidiasis and candidaemia in paediatric and adult patients with newly diagnosed or refractory infections. Micafungin 50 mg/day provided significantly better antifungal prophylaxis than fluconazole 400 mg/day in 882 haematopoietic stem cell transplant recipients in a randomised, double-blind trial. Respective overall success rates were 80% and 73.5%. Micafungin is generally well tolerated. Adverse events were not dose- or infusion-related with micafungin 12.5-900 mg/day; no histamine-like reactions occurred. Micafungin was as well tolerated as fluconazole, with numerically fewer micafungin recipients discontinuing treatment (4.2% vs 7.2%).

Newer Systemic Antifungal Agents

The past few years have seen the advent of several new antifungal agents, including those of a new class and a new generation of an existing class. Caspofungin, the first available echinocandin, has greatly expanded the antifungal armamentarium by providing a cell wall-active agent with candidacidal activity as well as demonstrated clinical efficacy in the therapy of aspergillosis refractory to available therapy. In addition, in clinical trials, caspofungin had comparable efficacy to amphotericin B for candidaemia and invasive Candida infections. Caspofungin and two more recently introduced echinocandins, micafungin and anidulafungin, are available as intravenous formulations only and characterised by potent anti-candidal activity, as well as few adverse events and drug interactions. Voriconazole, the first available second-generation triazole, available in both intravenous and oral formulations, has added a new and improved therapeutic option for primary therapy of invasive aspergillosis and salvage therapy for yeasts and other moulds. In a randomised trial, voriconazole demonstrated superior efficacy and a survival benefit compared with amphotericin B followed by other licensed antifungal therapy. This and data from a noncomparative study led to voriconazole becoming a new standard of therapy for invasive aspergillosis. Voriconazole has several important safety issues, including visual adverse events, hepatic enzyme elevation and skin reactions, as well as a number of drug interactions. Posaconazole, only available orally and requiring dose administration four times daily, shows encouraging efficacy in difficult to treat infections due to zygomycetes. Ravuconazole, available in both intravenous and oral formulations, has broad-spectrum in vitro potency and in vivo efficacy against a wide range of fungal pathogens. Clinical studies are underway. Despite the advances offered with each of these drugs, the morbidity and mortality associated with invasive fungal infections remains unacceptable, especially for the most at-risk patients. For individuals with severe immunosuppression as a result of chemotherapy, graft-versus-host disease and its therapy, or transplantation, new drugs and strategies are greatly needed.

Tissue Distribution after Intravenous Dosing of Micafungin, an Antifungal Drug, to Rats

The tissue distribution after an intravenous dose of micafungin (1 mg/kg), a new echinocandin-like lipopeptide antifungal agent, to male rats was investigated. Micafungin in plasma disappeared biexponentially with a terminal half-life of 5.03 h. Micafungin concentrations in liver, kidney, and lung at the first sampling time (5 min) after dosing were 1.15, 1.64, and 2.58-fold higher than the plasma concentration, and the AUC(0- infinity ) were 1.61, 3.42, and 2.89-fold higher than that for plasma. The terminal half-lives for these tissues were 5.14, 4.87, and 5.31 h, respectively, which were comparable to those for plasma. These results suggest that micafungin distributes rapidly and moderately into tissues such as the liver, kidney, and lungs, and that the concentrations in tissues decreased in parallel with the unchanged drug in plasma.

Breakthrough Scedosporium apiospermum (Pseudallescheria boydii) brain abscess during therapy for invasive pulmonary aspergillosis following high-risk allogeneic hematopoietic stem cell transplantation. Scedosporiasis and recent advances in antifungal therapy

Systemic scedosporiasis due to the anamorph or asexual form Scedosporium apiospermum (Pseudallescheria boydii) has become an important cause of opportunistic mycosis, especially in patients undergoing high-risk hematopoietic stem cell transplantation. We report a case of rapidly progressive cerebellar hyalohyphomycosis due to Scedosporium apiospermum in an allogeneic marrow graft recipient receiving treatment for severe graft-versus-host disease. This fatal breakthrough intracranial abscess, due to amphotericin B-resistant (minimum inhibitory concentration > 16 micro g/ml) mold, developed during the course of systemic antifungal therapy given for multicentric pulmonary aspergillosis. Despite treatment with high-dose Abelcet (10 mg/kg daily), free amphotericin B was not detected in postmortem cerebellar tissue. A broad-spectrum triazole-based agent (voriconazole/UK-109, 496--Vfend), and a novel fungal cell wall inhibitor, an echinocandin/pneumocandin analog (caspofungin/MK-0991--Cancidas), which exhibit excellent in vitro activity against most clinical Pseudallescheria boydii-Scedosporium apiospermum isolates, have recently become available in the United States and may provide much needed treatment options for patients at risk.

Comparative antifungal activities and plasma pharmacokinetics of micafungin (FK463) against disseminated candidiasis and invasive pulmonary aspergillosis in persistently neutropenic rabbits

Micafungin (FK463) is an echinocandin that demonstrates potent in vitro antifungal activities against Candida and Aspergillus species. However, little is known about its comparative antifungal activities in persistently neutropenic hosts. We therefore investigated the plasma micafungin pharmacokinetics and antifungal activities of micafungin against experimental disseminated candidiasis and invasive pulmonary aspergillosis in persistently neutropenic rabbits. The groups with disseminated candidiasis studied consisted of untreated controls (UCs); rabbits treated with desoxycholate amphotericin B (DAMB) at 1 mg/kg of body weight/day; or rabbits treated with micafungin at 0.25, 0.5, 1, and 2 mg/kg/day intravenously. Compared with the UCs, rabbits treated with micafungin or DAMB showed significant dosage-dependent clearance of Candida albicans from the liver, spleen, kidney, brain, eye, lung, and vena cava. These in vivo findings correlated with the results of in vitro time-kill assays that demonstrated that micafungin has concentration-dependent fungicidal activity. The groups with invasive pulmonary aspergillosis studied consisted of UCs; rabbits treated with DAMB; rabbits treated with liposomal amphotericin B (LAMB) at 5 mg/kg/day; and rabbits treated with micafungin at 0.5, 1, and 2 mg/kg/day. In comparison to the significant micafungin dosage-dependent reduction of the residual burden (in log CFU per gram) of C. albicans in tissue, micafungin-treated rabbits with invasive pulmonary aspergillosis had no reduction in the concentration of Aspergillus fumigatus in tissue. DAMB and LAMB significantly reduced the burdens of C. albicans and A. fumigatus in tissues (P < 0.01). Persistent galactomannan antigenemia in micafungin-treated rabbits correlated with the presence of an elevated burden of A. fumigatus in pulmonary tissue. By comparison, DAMB- and LAMB-treated animals had significantly reduced circulating galactomannan antigen levels. Despite a lack of clearance of A. fumigatus from the lungs, there was a significant improvement in the rate of survival (P < 0.001) and a reduction in the level of pulmonary infarction (P < 0.05) in micafungin-treated rabbits. In summary, micafungin demonstrated concentration-dependent and dosage-dependent clearance of C. albicans from persistently neutropenic rabbits with disseminated candidiasis but not of A. fumigatus from persistently neutropenic rabbits with invasive pulmonary aspergillosis.

Management of neonatal candidiasis. Neonatal Candidiasis Study Group

OBJECTIVE

To identify areas of consensus and controversy in the management of neonatal candidiasis.

METHODS

A questionnaire was distributed to US-based members of the Pediatric Infectious Diseases Society and a sampling of US neonatologists.

RESULTS

Three hundred eighty evaluable questionnaires were returned (42% of those mailed). Ninety-five percent of respondents have cared for an infant with systemic candidiasis in the past 2 years. Fluconazole and liposomal amphotericin are used to some extent by 90 and 69% of respondents, respectively. A single blood culture positive for Candida led to a recommendation for immediate treatment by 99%; amphotericin B was the preferred therapy for candidemia (88%). More than 80% of respondents would request cerebrospinal fluid, urine and repeat blood cultures and ophthalmologic examination in the evaluation of candidemia. If a cerebrospinal fluid culture is positive, 25% would use amphotericin B alone whereas 62% would add flucytosine. For candiduria Society members chose fluconazole therapy more often than did neonatologists, 23% vs. 3.4% (P<0.001). There was no consensus concerning duration of therapy, use of an amphotericin B test dose or management of a central catheter in place during candidemia.

CONCLUSIONS

Systemic candidiasis in neonates is a frequently encountered clinical problem. There is agreement that prompt therapy with amphotericin B is required if a blood culture is positive for Candida and that such infants require additional evaluations. Other antifungals (fluconazole, liposomal amphotericin B) are used to some extent in this population. Many issues in management have no clear consensus and warrant further research.