Population pharmacokinetics of micafungin in pediatric patients and implications for antifungal dosing

Weight drives caspofungin pharmacokinetic variability in overweight and obese people: fractal power signatures beyond two-thirds or three-fourths

Echinocandins, such as caspofungin, are commonly used to treat candidemia and aspergillosis. Success rates for candidemia treatment are approximately 70%. Dose optimization may further help improve these success rates, given that the microbial effect of these agents is concentration dependent. There are conflicting data as regards the effect of weight and/or obesity on caspofungin drug concentrations. We designed a prospective study to evaluate the population pharmacokinetics of caspofungin in adults with a weight difference range of 100 kg. Caspofungin pharmacokinetics were best described using a two-compartment pharmacokinetic model. There were 18 subjects studied, of whom half were women. The central volume was typically 4.2 liters but increased by a factor of (weight/53.6)(3/4). The peripheral compartment volume was typically 2.53 liters but increased by a factor of (weight/53.6)(3/2), an unusual power law signature. Similarly, the 3/4 power law best described the relationship between weight and systemic clearance for persons weighing >66.3 kg, whereas intercompartmental clearance was best described by the 3/2 power signature. There are two implications of our findings. First, lower caspofungin area-under-the-concentration-time curves are achieved in obese persons than thinner ones. This suggests that dose optimization in heavier patients may improve clinical success rates. Second, the 3/2 exponent is unusual in fractal geometry-based scaling and warrants further study. Moreover, this suggests that use of a "floating" instead of a fixed exponent may be more useful in studies where weight is under investigation as a potential cause of pharmacokinetic variability within adult patients. (This study protocol was registered at www.clinicaltrials.gov under registration number NCT01062165.).

The use of antifungal therapy in neonatal intensive care

Invasive fungal infections remain a significant cause of infection-related mortality and morbidity in preterm infants. Central nervous system involvement is the hallmark of neonatal candidiasis, differentiating the disease's impact on young infants from that among all other patient populations. Over the past decade, the number of antifungal agents in development has grown, but most are not labeled for use in newborns. We summarize the findings of several antifungal studies that have been completed to date, emphasizing those including infant populations. We conclude that more studies are required for antifungals to be used safely and effectively in infants.

Ethambutol pharmacokinetic variability is linked to body mass in overweight, obese, and extremely obese people

We conducted a prospective study of 18 adult volunteers (male-to-female ratio of 1) whose body mass index fell into categories of <25, 25 to 40, or >40 kg/m(2), who received a single oral dose of 1,600 mg ethambutol. Only individuals with normal renal function were recruited. The minimum body mass (M) was 45.6 kg, the median was 90.8 kg, and the maximum weight was 160.4 kg. Ethambutol pharmacokinetics were best described by a two-compartment model. Inclusion of weight as a covariate dramatically improved the model, with a relative likelihood approaching infinity. The typical clearance was 42.6 liters/h. Ethambutol systemic clearance was proportional to (M/45.6)(3/4) and thus obeyed fractal geometry-based laws. This means that the area under the concentration-time curve (AUC) actually decreased for obese patients compared to that for leaner patients, reducing chances of concentration-dependent toxicity. On the other hand, such reduced AUCs could lead to therapy failure. Thus, new and individualized ethambutol dosing regimens need to be designed for obese and extremely obese patients.

Anidulafungin for neonatal hematogenous Candida meningoencephalitis: identification of candidate regimens for humans using a translational pharmacological approach

Hematogenous Candida meningoencephalitis (HCME) is a serious infection in premature neonates. Anidulafungin is an echinocandin antifungal agent with potent activity against Candida spp., but its efficacy and optimal regimens for human neonates with HCME are not known. A well-validated rabbit model of HCME was used to define pharmacokinetic-pharmacodynamic (PK-PD) relationships of anidulafungin. A mathematical model was fitted to the entire data set. The experimental data were bridged to humans. A population PK model was fitted to the data from human neonates receiving anidulafungin receiving a loading dose of 3 mg/kg, followed by 1.5 mg/kg/day. Monte Carlo simulations were performed to identify candidate anidulafungin regimens for humans. All untreated rabbits succumbed by ≤96 h postinoculation. The PK of anidulafungin was linear with dose-dependent penetration into the cerebrum. Anidulafungin exerted a rapid antifungal effect that was apparent in the first dosing interval. Near-maximal antifungal activity was observed with dosages of 10 to 20 mg/kg/day. The bridging studies suggested that the current regimen of first 3 mg/kg, followed by 1.5 mg/kg/day, is suboptimal. Higher dosages were associated with progressively greater antifungal effect. Anidulafungin is effective for the treatment of experimental HCME. Higher dosages than those currently used for clinical care are required for maximal antifungal effect.

Innovative clinical trial design for pediatric therapeutics

Until approximately 15 years ago, sponsors rarely included children in the development of therapeutics. US and European legislation has resulted in an increase in the number of pediatric trials and specific label changes and dosing recommendations, although infants remain an understudied group. The lack of clinical trials in children is partly due to specific challenges in conducting trials in this patient population. Therapeutics in special populations, including premature infants, obese children and children receiving extracorporeal life support, are even less studied. National research networks in Europe and the USA are beginning to address some of the gaps in pediatric therapeutics using novel clinical trial designs. Recent innovations in pediatric clinical trial design, including sparse and scavenged sampling, population pharmacokinetic analyses and 'opportunistic' studies, have addressed some of the historical challenges associated with clinical trials in children.

Fractal geometry and the pharmacometrics of micafungin in overweight, obese, and extremely obese people

The majority of Americans are overweight, and the incidence of obesity continues to increase. This trend predisposes people to a number of deleterious consequences, including the metabolic syndrome and other conditions that lead to a greater number of hospital admissions. Invasive candidiasis is an important nosocomial infection that results from these admissions. Echinocandins such as micafungin are indicated for treatment. We have previously demonstrated that overweight patients exhibit higher micafungin systemic clearance (SCL) than leaner patients. We hypothesized that obese and extremely obese people would show even higher SCL than merely overweight patients. To test this, we performed a prospective study of 36 adult volunteers randomized to receive a single dose of either 100 mg or 300 mg of micafungin whose body mass index fell within one of the following categories: <25, 25 to 40, and >40 kg/m(2). The male-to-female ratio was 1:1. The minimum weight was 43 kg, the median 97 kg, and the maximum weight 155 kg. A two-compartment model was examined using the maximum likelihood solution via the expectation-maximization algorithm. Men had a higher median SCL of 1.53 liters/h versus 1.29 liters/h (P = 0.01) in the Mann-Whitney U-test. The typical SCL was 1.04 liters/h but increased by a factor of (weight/66)(0.75) as weight increased above 66 kg. Thus, the relationship between micafungin SCL and weight in adults is best described by fractal-geometry-based laws. Furthermore, micafungin SCL continues to increase as weight increases, with no obvious plateau. This leads to a requirement for strategies to determine individualized dosing levels for obese and extremely obese patients.

Pharmacology and metabolism of anidulafungin, caspofungin and micafungin in the treatment of invasive candidosis: review of the literature

Echinocandins represent the newest class of antifungal agents. Currently, three echinocandins, anidulafungin, caspofungin and micafungin are licensed for clinical use in various indications. They act as inhibitors of β-(1,3)-glucan synthesis in the fungal cell wall and have a favorable pharmacological profile. They have a broad spectrum of activity against all Candida species. Higher MIC's have been observed against C. parapsilosis and C. guilliermondii. Data from clinical trials for invasive Candida infections/candidaemia suggest that the clinical outcome of patients treated with either drug may be very similar. A comparison has been done between caspofungin and micafungin but for anidulafungin a comparative trial with another echinocandin is still lacking. All three drugs are highly effective if not superior to treatment with either fluconazole or Amphotericin B, particularly in well-defined clinical settings such as invasive Candida infections, Candida oesophagitis and candidaemia. Differences between the three echinocandins with regard to the route of metabolism, requirement for a loading dose, dose adjustment in patients with moderate to severe hepatic disease and different dosing schedules for different types of Candida infections have to be considered. Relevant drug-drug interactions of Caspofungin and Micafungin are minimal. Anidulafungin has no significant drug interactions at all. However, echinocandins are available only for intravenous use. All three agents have an excellent safety profile.

[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.

[Differential pharmacokinetic characteristics of micafungin. Experience in special populations]

Currently, three echinocandins are available for the treatment of fungal infections. Micafungin is the latest drug to be incorporated into this group of antifungal agents. Although the mechanism of action of micafungin is similar to that of other echinocandins, this molecule has certain pharmacokinetic characteristics that distinguish it from other drugs in this group. Nowadays, there is wide information on the pharmacokinetic behavior of micafungin, mainly from patients included in clinical trials. However, there is far less knowledge of the pharmacokinetics of this echinocandin in special populations. The aim of the current review was to analyze the available information on the pharmacokinetics of micafungin in pediatric patients, the elderly, patients with renal insufficiency or liver failure, and transplant recipient.

Antifungal prophylaxis and therapy in patients with hematological malignancies and hematopoietic stem cell transplant recipients

Patients with acute leukemia and hematopoietic stem cell transplant recipients are at risk of a spectrum of invasive fungal diseases corresponding to the type and intensity of immunosuppression. The development of newer antifungal agents has broadened therapeutic options. In the 1990s, lipid formulations of amphotericin B became widely used as safer alternatives to amphotericin B deoxycholate. In addition, fluconazole was shown to be beneficial as a yeast-active prophylaxis in hematopoietic stem cell transplant recipients. In the past decade, the antifungal armamentarium was further enhanced with the availability of extended-spectrum azoles and echinocandins. The development of effective broad-spectrum antifungal agents has led to their use as prophylaxis rather than delaying treatment until clinical signs of infection manifest. Antigen-based and PCR-based diagnostic adjuncts facilitate earlier detection of invasive fungal diseases compared with conventional culture, and have been incorporated into strategies in which initiation or modification of an antifungal regimen is targeted to patients with the highest likelihood of having fungal disease. Here, we review the pharmacological data and major clinical trials that guide the use of antifungals, as well as areas of uncertainty and future perspectives.

Efficacy and safety of antifungals in pediatric patients

Invasive fungal infections (IFIs) constitute an important cause for morbidity and mortality in immunocompromised pediatric patients [1]. Despite substantial achievements, the prevention and treatment of IFIs are still limited by the facts that not all antifungal agents are approved in the pediatric population, the appropriate dosage of these drugs has not been established for all age groups, and postmarketing data providing information on the safety and efficacy of approved agents under real-life circumstances are scant. In this article, we 1) briefly review the principles of drug development, 2) discuss safety and approved indications of antifungal agents, and 3) provide a summary of current options for treatment of invasive fungal infections in pediatric patient populations.

Population pharmacokinetics and pharmacodynamics of caspofungin in pediatric patients

We describe the pharmacokinetics (PKs) of caspofungin, an echinocandin antifungal, administered once daily as a 1-hour intravenous infusion in children and adolescents (ages, 3 months to 17 years), based on pooled data from four prospective pediatric studies. Caspofungin dosing was body-surface-area (BSA) based (50 mg/m2 daily after 70 mg/m2 on day 1). The area under the concentration-time curve from time zero to 24 h (AUC0-24), the concentration at the end of infusion (1 h after the start of infusion; C1), and the trough concentration (24 h after the start of infusion; C24) were obtained for 32 pediatric patients with invasive candidiasis, 10 with invasive aspergillosis, and 82 in the setting of empirical therapy with fever and neutropenia. Exposures were modestly higher (93 to 134% for C1, 45 to 78% for C24, ∼40% for AUC0-24) in pediatric patients than in adults receiving the standard 50-mg daily dose. The potential for covariates (age, gender, weight, race, renal status, serum albumin level, and disease state) to alter PKs was evaluated with a multiple-linear-regression model. Weight and disease state had statistically significant (P<0.05) yet small effects on caspofungin PKs in pediatric patients. Concomitant use of dexamethasone (a cytochrome p450 inducer) was associated with a statistically significant reduction (44%) in C24 in a limited number of patients (n=4). Odds ratios were estimated for the association between log-transformed PKs and treatment outcome or adverse events. No PK parameter or hybrid parameter (AUC/MIC, C1/MIC, and C24/MIC) was significantly correlated with treatment outcome or adverse events in the setting of similar response levels as adults, which suggests that the concentrations examined fall within the therapeutic window for caspofungin in pediatric patients. These results support a 50-mg/m2 daily dosing regimen (after a 70-mg/m2 loading dose) in children ages 3 months to 17 years.

Micafungin: a brief review of pharmacology, safety, and antifungal efficacy in pediatric patients

Invasive fungal infections are a major cause of morbidity and mortality in children with hematological malignancies and those undergoing allogeneic hematopoietic stem-cell transplantation (HSCT). Although several new antifungal compounds recently became available, some are not yet approved for the use in the pediatric population. Among the new class of echinocandins, micafungin has been licensed in Europe and Japan for children including neonates. Because micafungin is well tolerated and exhibits few clinical relevant drug-drug interactions, the compound is of particular interest for prophylaxis and treatment of invasive mycoses in pediatric patients with cancer or following allogeneic HSCT. This review will focus on the currently available pediatric data of micafungin with emphasis on pharmacokinetics, efficacy, and safety.

Population pharmacokinetics of micafungin in neonates and young infants

Micafungin is an echinocandin with potent activity against Candida spp. Hematogenous Candida meningoencephalitis (HCME) is a frequent complication of disseminated Candida infection in premature infants. A preclinical model of HCME suggests that micafungin may be an effective agent for this syndrome, but relatively high weight-based dosages are required. This prompted the further study of the safety and pharmacokinetics (PK) of micafungin in infants. Here, we describe the population pharmacokinetics of micafungin in 47 infants with a proven or presumptive diagnosis of disseminated candidiasis, who received 0.75, 1.5, 3, 7, 10, and 15 mg/kg of micafungin. The drug was infused daily, and samples were taken in the first dosing interval and at steady state. Serum concentrations were measured using high-performance liquid chromatography (HPLC). Data were modeled using an allometric pharmacokinetic model using a three-fourths scaling exponent for clearance and parameters normalized to a 70-kg adult. Drug exposures were estimated using Monte Carlo simulation. Optimal sampling times were determined using D-optimal design theory. The fit of the allometric model to the data was highly acceptable. The pharmacokinetics of micafungin were linear. The weight-normalized estimates of clearance and volume of distribution approximated those previously described for adults. The original population parameter values could be recapitulated in the Monte Carlo simulations. A dosage of 10 mg/kg/day resulted in 82.6% of patients with areas under the concentration-time curve (AUCs) that are associated with near-maximal decline in fungal burden within the central nervous system (CNS).

Pediatric antifungal agents

PURPOSE OF REVIEW

In immunocompromised hosts, invasive fungal infections are common and fatal. In the past decade, the antifungal armamentarium against invasive mycoses has expanded greatly. The purpose of the present report is to review the most recent literature addressing the use of antifungal agents in children.

RECENT FINDINGS

Most studies evaluating the safety and efficacy of antifungal agents are limited to adults. However, important progress has been made in describing the pharmacokinetics and safety of newer antifungal agents in children, including the echinocandins.

SUMMARY

Dosage guidelines for newer antifungal agents are currently based on adult and limited pediatric data. Because important developmental pharmacology changes occur throughout childhood impacting the pharmacokinetics of these agents, antifungal studies specifically designed for children are necessary.

A Clinical Review of Echinocandins in Pediatric Patients

OBJECTIVE

To identify and evaluate available data on pediatric echinocandin use.

DATA SOURCES

A PubMed search, limited to English-language articles, was conducted (1990-August 2009) using the search terms echinocandin, pediatric, child, pharmacokinetics, caspofungin, micafungin, and anidulafungin. Additional articles were retrieved from citations of selected references.

STUDY SELECTION AND DATA EXTRACTION

Relevant information on the pharmacology, pharmacokinetics, efficacy, and safety of echinocandins in children was selected. Clinical trials, retrospective reviews, and case series were identified and evaluated. Data from these sources were included in this review.

DATA SYNTHESIS

Caspofungin is the only echinocandin approved by the Food and Drug Administration for use in children. Pediatric pharmacokinetics has been evaluated with all 3 echinocandins but is limited with anidulafungin. Micafungin is the most well-studied agent in prospective clinical trials for antifungal prophylaxis in stem cell transplantation and treatment of invasive fungal infections. Caspofungin has been studied prospectively for febrile neutropenia and treatment of invasive fungal infections, but most published data are from retrospective reviews or case reports. One case report of anidulafungin for neonatal candidiasis has been published. The role of echinocandins in the management of invasive pediatric fungal infections has expanded. Micafungin and caspofungin are recommended as primary or alternative treatment of candidemia and esophageal or invasive candidiasis, and as salvage therapy for invasive aspergillosis. Micafungin is recommended for neutropenic prophylaxis in stem cell transplantation, while caspofungin may be used in febrile neutropenia as an alternative to azoles. Dosing has been well established for caspofungin only in children 3 months of age and above. Anidulafungin should be avoided in children until more pharmacokinetic and clinical data become available.

CONCLUSIONS

Further comparative trials are needed to more clearly define the role of echinocandins, either as monotherapy or in combination for difficult-to-treat infections, in the pediatric population.

Antifungal pharmacokinetics and pharmacodynamics: bridging from the bench to bedside

This review considers a way in which experimental data can be used to identify safe and effective antifungal regimens for humans. The process begins with experimental models of invasive fungal infections that enable definition of optimal dosages and schedules of antifungal drug administration to be defined. These preclinical models also enable the identification of drug exposure targets that are associated with therapeutic outcomes of interest. Human pharmacokinetic variability results in a considerable range of drug exposures following the use of fixed antifungal drug regimens. This variability can be quantified using population pharmacokinetic modeling techniques. Monte Carlo simulation can then be used to simulate pharmacokinetic variability and thereby estimate the proportion of patients with a therapeutic outcome of interest. Effective and safe regimens can thus be studied appropriately in clinical settings. This approach can, and should, be used to optimize antifungal therapy for a large number of clinical scenarios.

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.

Pharmacotherapy of Candida Infections with Echinocandins

The classic recommended antifungal agents for the treatment of invasive Candida infections were amphotericin B, a lipid formulation of amphotericin B and fluconazole in both neutropenic or nonneutropenic patients as either primary or alternative therapies. Voriconazole has been recommended when additional coverage for filamentous fungi is needed (e.g. neutropenic patients). More recently and based on well designed comparative clinical trials, the three echinocandins, caspofungin, anidulafungin and micafungin have been added as primary or alternative therapies especially for critically ill or neutropenic patients. In general, the echinocandins are most useful when patients have previously been exposed to an azole or are unstable.

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

BACKGROUND

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

AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Hepatitis associated with micafungin use in a preterm infant

Micafungin is an echinocandin-class antifungal agent licensed for treatment of invasive disease in adults. The optimal dosing regimens have not been established for infants. We describe a premature infant who developed hepatitis and cholestasis during micafungin therapy initiated for protracted candidemia. Practitioners should be aware of this potential adverse effect if using micafungin in young patients.

Newer antifungal agents for invasive fungal infections in patients with haematological malignancy

Since 2001 five new systemically administered antifungal agents have been approved for clinical use. This represents a major advance for antifungal therapy in haematological malignancy patients undergoing chemotherapy or haematopoietic stem cell transplant (HSCT). The echinocandins are a new class of antifungals with a novel mode of action. Capsofungin has already established itself as a valuable therapy for candidaemia and salvage therapy of invasive aspergillosis. Although both anidulafungin and micafungin are approved for treatment of candidiasis, their role in invasive aspergillosis requires more clinical trial evaluation. Of the two newer triazoles, voriconazole has been recommended in international guidelines as primary therapy for acute invasive aspergillosis. Posaconazole has a broad spectrum of activity in vitro and a potentially key role in antifungal prophylaxis in high-risk HSCT recipients and during prolonged neutropenia. Although some of these drugs have important interactions with other medications, and potential toxicities, they are safer to use and more efficacious than amphotericin B deoxycholate. Their arrival gives more choices to treat rarer mycoses and will facilitate clinical trial assessment of combination therapy of aspergillosis where single agent therapy gives less than 50% success rates.

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.