Single- and multiple-dose pharmacokinetics of caspofungin in healthy men

Modeling of intravenous caspofungin administration using an intestine-on-chip reveals altered Candida albicans microcolonies and pathogenicity

Candida albicans is a commensal yeast of the human intestinal microbiota that, under predisposing conditions, can become pathogenic and cause life-threatening systemic infections (candidiasis). Fungal-host interactions during candidiasis are commonly studied using conventional 2D in vitro models, which have provided critical insights into the pathogenicity. However, microphysiological models with a higher biological complexity may be more suitable to mimic in vivo-like infection processes and antifungal drug efficacy. Therefore, a 3D intestine-on-chip model was used to investigate fungal-host interactions during the onset of invasive candidiasis and evaluate antifungal treatment under clinically relevant conditions. By combining microbiological and image-based analyses we quantified infection processes such as invasiveness and fungal translocation across the epithelial barrier. Additionally, we obtained novel insights into fungal microcolony morphology and association with the tissue. Our results demonstrate that C. albicans microcolonies induce injury to the epithelial tissue by disrupting apical cell-cell contacts and causing inflammation. Caspofungin treatment effectively reduced the fungal biomass and induced substantial alterations in microcolony morphology during infection with a wild-type strain. However, caspofungin showed limited effects after infection with an echinocandin-resistant clinical isolate. Collectively, this organ-on-chip model can be leveraged for in-depth characterization of pathogen-host interactions and alterations due to antimicrobial treatment.

Antifungal drug penetration in soft tissue abscesses: a comparative analysis

BACKGROUND

Invasive fungal infections (IFIs) are severe and difficult-to-treat infections affecting immunocompromised patients. Antifungal drug penetration at the site of infection is critical for outcome and may be difficult to achieve. Data about antifungal drug distribution in infected human tissues under real circumstances of IFI are scarce.

METHODS

Multiple samples were obtained from soft tissue abscesses of a lung transplant patient with Candida albicans invasive candidiasis who underwent recurrent procedures of drainage, while receiving different consecutive courses of antifungal therapy [itraconazole (ITC), fluconazole, caspofungin]. Antifungal drug concentrations were measured simultaneously at the site of infection (surrounding inflammatory tissue and fluid content of the abscess) and in plasma for calculation of the tissue/plasma ratio (R). The concentration within the infected tissue was interpreted as appropriate if it was equal or superior to the MIC of the causal pathogen.

RESULTS

A total of 30 tissue samples were collected for measurements of ITC (n = 12), fluconazole (n = 17) and caspofungin (n = 1). Variable concentrations were observed in the surrounding tissue of the lesions with median R of 2.79 (range 0.51-15.9) for ITC and 0.94 (0.21-1.37) for fluconazole. Concentrations ranges within the fluid content of the abscesses were 0.39-1.83 for ITC, 0.66-1.02 for fluconazole and 0.23 (single value) for caspofungin. The pharmacodynamic target (tissue concentration ≥ MIC) was achieved in all samples for all three antifungal drugs.

CONCLUSIONS

This unique dataset of antifungal drug penetration in infected human soft tissue abscesses suggests that ITC, fluconazole and caspofungin could achieve appropriate concentrations in soft tissue abscesses.

The recommended dosage regimen for caspofungin in patients with higher body weight or hypoalbuminaemia will result in low exposure: Five years of data based on a population pharmacokinetic model and Monte-Carlo simulations

Background: To develop a population pharmacokinetic (PPK) model for caspofungin, identify parameters influencing caspofungin pharmacokinetics, and assess the required probability of target attainment (PTA) and cumulative fraction of response (CFR) for various dosing regimens of caspofungin in all patients and intensive care unit (ICU)-subgroup patients. Method: The general PPK model was developed based on data sets from all patients (299 patients). A ICU-subgroup PPK model based on data sets from 136 patients was then analyzed. The effects of demographics, clinical data, laboratory data, and concomitant medications were tested. Monte-Carlo simulations (MCS) were used to evaluate the effectiveness of different caspofungin dosage regimens. Results: One-compartment model best described the data of all patients and ICU patients. Clearances (CL) were 0.32 L/h and 0.40 L/h and volumes of distribution (V) were 13.31 L and 10.20 L for the general and ICU-subgroup PPK models, respectively. In the general model, CL and V were significantly associated with albumin (ALB) concentration and body weight (WT). In the ICU-subgroup model, CL was associated with WT. The simulated exposure in ICU patients was lower than that in all patients (p < 0.05). MCS indicated that higher caspofungin maintenance doses of 70-150 mg may achieve target CFR of >90% for patients with higher WT (>70 kg) or with C. albicans or C. parapsilosis infections, and especially for ICU patients with hypoalbuminaemia. Conclusion: The PPK model and MCS presented in the study demonstrated that the recommended dosage regimen for caspofungin in patients with higher body weight or hypoalbuminaemia will result in low exposure.

Therapeutic Drug Monitoring of Antifungal Agents in Critically Ill Patients: Is There a Need for Dose Optimisation?

Invasive fungal infections are an important cause of morbidity and mortality, especially in critically ill patients. Increasing resistance rates and inadequate antifungal exposure have been documented in these patients, due to clinically relevant pharmacokinetic (PK) and pharmacodynamic (PD) alterations, leading to treatment failure. Physiological changes such as third spacing (movement of fluid from the intravascular compartment to the interstitial space), hypoalbuminemia, renal failure and hepatic failure, as well as common interventions in the intensive care unit, such as renal replacement therapy and extracorporeal membrane oxygenation, can lead to these PK and PD alterations. Consequently, a therapeutic target concentration that may be useful for one patient may not be appropriate for another. Regular doses do not take into account the important PK variations in the critically ill, and the need to select an effective dose while minimising toxicity advocates for the use of therapeutic drug monitoring (TDM). This review aims to describe the current evidence regarding optimal PK/PD indices associated with the clinical efficacy of the most commonly used antifungal agents in critically ill patients (azoles, echinocandins, lipid complexes of amphotericin B, and flucytosine), provide a comprehensive understanding of the factors affecting the PK of each agent, document the PK parameters of critically ill patients compared to healthy volunteers, and, finally, make recommendations for therapeutic drug monitoring (TDM) of antifungals in critically ill patients.

Interaction of Antifungal Drugs with CYP3A- and OATP1B-Mediated Venetoclax Elimination

Venetoclax, a BCL-2 inhibitor used to treat certain hematological cancers, exhibits low oral bioavailability and high interpatient pharmacokinetic variability. Venetoclax is commonly administered with prophylactic antifungal drugs that may result in drug interactions, of which the underlying mechanisms remain poorly understood. We hypothesized that antifungal drugs may increase venetoclax exposure through inhibition of both CYP3A-mediated metabolism and OATP1B-mediated transport. Pharmacokinetic studies were performed in wild-type mice and mice genetically engineered to lack all CYP3A isoforms, or OATP1B2 that received venetoclax alone or in combination with ketoconazole or micafungin. In mice lacking all CYP3A isoforms, venetoclax AUC was increased by 1.8-fold, and pretreatment with the antifungal ketoconazole further increased venetoclax exposure by 1.6-fold, despite the absence of CYP3A. Ensuing experiments demonstrated that the deficiency of OATP1B-type transporters is also associated with increases in venetoclax exposure, and that many antifungal drugs, including micafungin, posaconazole, and isavuconazole, are inhibitors of this transport mechanism both in vitro and in vivo. These studies have identified OATP1B-mediated transport as a previously unrecognized contributor to the elimination of venetoclax that is sensitive to inhibition by various clinically-relevant antifungal drugs. Additional consideration is warranted when venetoclax is administered together with agents that inhibit both CYP3A-mediated metabolism and OATP1B-mediated transport.

Therapeutic Drug Monitoring of the Echinocandin Antifungal Agents: Is There a Role in Clinical Practice? A Position Statement of the Anti-Infective Drugs Committee of the International Association of Therapeutic Drug Monitoring and Clinical Toxicology

PURPOSE

Reduced exposure to echinocandins has been reported in specific patient populations, such as critically ill patients; however, fixed dosing strategies are still used. The present review examines the accumulated evidence supporting echinocandin therapeutic drug monitoring (TDM) and summarizes available assays and sampling strategies.

METHODS

A literature search was conducted using PubMed in December 2020, with search terms such as echinocandins, anidulafungin, caspofungin, micafungin, or rezafungin with pharmacology, pharmacokinetics (PKs), pharmacodynamics (PDs), drug-drug interactions, TDM, resistance, drug susceptibility testing, toxicity, adverse drug reactions, bioanalysis, chromatography, and mass spectrometry. Data on PD/PD (PK/PD) outcome markers, drug resistance, PK variability, drug-drug interactions, assays, and TDM sampling strategies were summarized.

RESULTS

Echinocandins demonstrate drug exposure-efficacy relationships, and maximum concentration/minimal inhibitory concentration ratio (Cmax/MIC) and area under the concentration-time curve/MIC ratio (AUC/MIC) are proposed PK/PD markers for clinical response. The relationship between drug exposure and toxicity remains poorly clarified. TDM could be valuable in patients at risk of low drug exposure, such as those with critical illness and/or obesity. TDM of echinocandins may also be useful in patients with moderate liver impairment, drug-drug interactions, hypoalbuminemia, and those undergoing extracorporeal membrane oxygenation, as these conditions are associated with altered exposure to caspofungin and/or micafungin. Assays are available to measure anidulafungin, micafungin, and caspofungin concentrations. A limited-sampling strategy for anidulafungin has been reported.

CONCLUSIONS

Echinocandin TDM should be considered in patients at known risk of suboptimal drug exposure. However, for implementing TDM, clinical validation of PK/PD targets is needed.

Pharmacokinetic Drug-drug Interaction of Antibiotics Used in Sepsis Care in China

BACKGROUND

Many antibiotics have a high potential for interactions with drugs, as a perpetrator and/or victim, in critically ill patients, and particularly in sepsis patients.

METHODS

The aim of this review is to summarize the pharmacokinetic drug-drug interaction (DDI) of 45 antibiotics commonly used in sepsis care in China. Literature search was conducted to obtain human pharmacokinetics/ dispositions of the antibiotics, their interactions with drug-metabolizing enzymes or transporters, and their associated clinical drug interactions. Potential DDI is indicated by a DDI index ≥ 0.1 for inhibition or a treatedcell/ untreated-cell ratio of enzyme activity being ≥ 2 for induction.

RESULTS

The literature-mined information on human pharmacokinetics of the identified antibiotics and their potential drug interactions is summarized.

CONCLUSION

Antibiotic-perpetrated drug interactions, involving P450 enzyme inhibition, have been reported for four lipophilic antibacterials (ciprofloxacin, erythromycin, trimethoprim, and trimethoprim-sulfamethoxazole) and three antifungals (fluconazole, itraconazole, and voriconazole). In addition, seven hydrophilic antibacterials (ceftriaxone, cefamandole, piperacillin, penicillin G, amikacin, metronidazole, and linezolid) inhibit drug transporters in vitro. Despite no clinical PK drug interactions with the transporters, caution is advised in the use of these antibacterials. Eight hydrophilic antibiotics (all β-lactams; meropenem, cefotaxime, cefazolin, piperacillin, ticarcillin, penicillin G, ampicillin, and flucloxacillin), are potential victims of drug interactions due to transporter inhibition. Rifampin is reported to perpetrate drug interactions by inducing CYP3A or inhibiting OATP1B; it is also reported to be a victim of drug interactions, due to the dual inhibition of CYP3A4 and OATP1B by indinavir. In addition, three antifungals (caspofungin, itraconazole, and voriconazole) are reported to be victims of drug interactions because of P450 enzyme induction. Reports for other antibiotics acting as victims in drug interactions are scarce.

Too Much of a Good Thing: Defining Antimicrobial Therapeutic Targets to Minimize Toxicity

Antimicrobials are a common cause of drug toxicity. Understanding the relationship between systemic antimicrobial exposure and toxicity is necessary to enable providers to take a proactive approach to prevent undesired drug effects. When an exposure threshold has been defined that predicts drug toxicity, therapeutic drug monitoring (TDM) can be performed to assure drug exposure does not exceed the defined threshold. Although some antimicrobials have well-defined dose-dependent toxicities, many other exposure-toxicity relationships have either not been well-defined or, in some cases, not been evaluated at all. In this review, we examine the relationship between exposures and toxicities for antibiotic, antifungal, and antiviral agents. Furthermore, we classify these relationships into four categories: known association between drug exposure and toxicity such that clinical implementation of a specific exposure threshold associated with toxicity for TDM is supported (category 1), known association between drug exposure and toxicity but the specific exposure threshold associated with toxicity is undefined (category 2), association between drug exposure and toxicity has been suggested but relationship is poorly defined (category 3), and no known association between drug exposure and toxicity (category 4). Further work to define exposure-toxicity thresholds and integrate effective TDM strategies has the potential to minimize many of the observed antimicrobial toxicities.

Pharmacokinetic/pharmacodynamics variability of echinocandins in critically ill patients: A systematic review and meta-analysis

WHAT IS KNOWN AND OBJECTIVE

Anidulafungin, caspofungin and micafungin are three widely used echinocandin drugs licensed for the treatment of invasive fungal infections, and their clinical use is widespread. To evaluate pharmacokinetic/pharmacodynamics variability of echinocandins in critically ill patients by comparing the differences in pharmacokinetic parameters between critically ill patients and healthy volunteers or general patients.

METHODS

MEDLINE, EMBASE, The Cochrane Library and Pubmed were searched from inception until 6 September 2018. Studies investigating the pharmacokinetic parameters of echinocandins in critically ill patients, healthy volunteers or general patients were included. Our primary outcomes included AUC0-24 h , Cmax and Cmin (24 hours). Two reviewers independently reviewed all titles, abstracts and text, and extracted data. We applied R software (R 2017) to conduct meta-analysis.

RESULTS AND DISCUSSION

Of 3235 articles screened, 17 studies were included in the data synthesis. Descriptive data from single-arm studies show that critically ill patients who received caspofungin had more stable AUC0-24 h than those who received anidulafungin and micafungin. The Cmax of critically ill patients who received caspofungin and micafungin was similar to healthy volunteers. However, the Cmax in critically ill patients who received anidulafungin was lower than in healthy volunteers. The Cmin and T1/2 of critically ill patients who received caspofungin were larger than in healthy volunteers. The Vd and CL of critically ill patients receiving anidulafungin and micafungin were larger than in healthy volunteers.

WHAT IS NEW AND CONCLUSION

This systematic review provides an analysis of the pharmacokinetic/pharmacodynamics variability of echinocandins in critically ill patients. Based on the limited data available, caspofungin has less pharmacokinetic/pharmacodynamics variability than anidulafungin and micafungin.

Impact of Loading Dose of Caspofungin in Pharmacokinetic-Pharmacodynamic Target Attainment for Severe Candidiasis Infections in Patients in Intensive Care Units: the CASPOLOAD Study

This study evaluated the impact of a high loading dose of caspofungin (CAS) on the pharmacokinetics of CAS and the pharmacokinetic-pharmacodynamic (PK-PD) target attainment in patients in intensive care units (ICU). ICU patients requiring CAS treatment were prospectively included to receive a 140-mg loading dose of CAS. Plasma CAS concentrations (0, 2, 3, 5, 7, and 24 h postinfusion) were determined to develop a two-compartmental population PK model. A Monte Carlo simulation was performed and the probabilities of target attainment (PTAs) were computed using previously published MICs. PK-PD targets were ratios of area under the concentration-time curve from 0 to 24 h (AUC_0-24h) divided by the MIC (AUC_0-24h/MIC) of 250, 450, and 865 and maximal concentration (C _max) divided by the MIC (C _max/MIC) of 5, 10, 15, and 20. Among 13 included patients, CAS clearance was 0.98 ± 0.13 liters/h and distribution volumes were V₁ = 9.0 ± 1.2 liters and V₂ = 11.9 ± 2.9 liters. Observed and simulated CAS AUC_0-24h were 79.1 (IQR 55.2; 108.4) and 81.3 (IQR 63.8; 102.3) mg · h/liter during the first 24 h of therapy, which is comparable to values usually observed in ICU patients at day 3 or later. PTAs were >90% for MICs of 0.19 and 0.5 mg/liter, considering AUC/MIC = 250 and C _max/MIC = 10 as PK-PD targets, respectively. Thus, a high loading dose of CAS (140 mg) increased CAS exposure in the first 24 h of therapy, allowing early achievement of PK-PD targets for most Candida strains. Such a strategy seems to improve treatment efficacy, though further studies are needed to assess the impact on clinical outcomes. (This study has been registered at ClinicalTrials.gov under identifier NCT02413892.).

Efficacy and mechanism of actions of natural antimicrobial drugs

Microbial infections have significantly increased over the last decades, and the mortality rates remain unacceptably high. The emergence of new resistance patterns and the spread of new viruses challenge the eradication of infectious diseases. The declining efficacy of antimicrobial drugs has become a global public health problem. Natural products derived from natural sources, such as plants, animals, and microorganisms, have significant efficacy for the treatment of infectious diseases accompanied by less adverse effects, synergy, and ability to overcome drug resistance. As the Chinese female scientist Youyou Tu received the Nobel Prize for the antimalarial drug artemisinin, antimicrobial drugs developed from Traditional Chinese Medicine are expected to receive increasing attention again. This review summarizes the antimicrobial agents derived from natural products approved for nearly 20 years and describes their efficacy and mode of action. The aim of this unit is to review the current status of antimicrobial drugs from natural products in order to increase the value of natural products as a source of novel drug candidates for infectious diseases.

Determination of antifungal caspofungin in RPMI-1640 cell culture medium by column-switching HPLC-FLD

The actual scenario in the fight against fungal infections forces researchers to carry through with resistance studies to improve the therapies. These studies, which are performed in cell culture media, need accurate and sensitive analytical methodologies. That is why, in this work, an analytical method for caspofungin (CSF) concentration determination in RPMI-1640 cell culture medium with on-line sample treatment was developed and validated. CSF concentration was determined by HPLC-FLD using a column-switching procedure. The chromatographic analysis was carried out in less than 10 min using a C8 column (4 × 4 mm, 5 μm) as extraction stationary phase and a HSS T3 column (4.6 × 100 mm, 5 μm) as the analytical column. The used mobile phases were mixtures of phase A: pH 2 (adjusted with TFA) aqueous phase and phase B: ACN. For the extraction, the composition was (95:5, A:B v/v) and for the analysis (60:40, A:B v/v), both done in isocratic elution mode. These chromatographic conditions allowed reaching a limit of quantification of 10 μg/L, using 100 μL of sample with an injected volume of 40 μL. The proposed method was successfully validated in terms of selectivity, carryover, linear concentration range, accuracy and precision according to the criteria established by the Food and Drug Administration. Available amount of CSF in RPMI-1640 solution was found critical. CSF concentrations remained stable up to 2 h at room temperature. The developed method was applied for the direct analysis of CSF concentrations from in vitro experiments in presence of C. glabrata (CAGL18). The results highlight the decrease of cell proliferation even if the CSF amount decreases too, which asks question about the real value of the efficient concentration for CSF antifungal activity.

Caspofungin Weight-Based Dosing Supported by a Population Pharmacokinetic Model in Critically Ill Patients

The objective of this study was to develop a population pharmacokinetic model and to determine a dosing regimen for caspofungin in critically ill patients. Nine blood samples were drawn per dosing occasion. Fifteen patients with (suspected) invasive candidiasis had one dosing occasion and five had two dosing occasions, measured on day 3 (±1) of treatment. Pmetrics was used for population pharmacokinetic modeling and probability of target attainment (PTA). A target 24-h area under the concentration-time curve (AUC) value of 98 mg·h/liter was used as an efficacy parameter.

The objective of this study was to develop a population pharmacokinetic model and to determine a dosing regimen for caspofungin in critically ill patients. Nine blood samples were drawn per dosing occasion. Fifteen patients with (suspected) invasive candidiasis had one dosing occasion and five had two dosing occasions, measured on day 3 (±1) of treatment. Pmetrics was used for population pharmacokinetic modeling and probability of target attainment (PTA). A target 24-h area under the concentration-time curve (AUC) value of 98 mg·h/liter was used as an efficacy parameter. Secondarily, the AUC/MIC targets of 450, 865, and 1,185 were used to calculate PTAs for Candida glabrata, C. albicans, and C. parapsilosis, respectively. The final 2-compartment model included weight as a covariate on volume of distribution (V). The mean V of the central compartment was 7.71 (standard deviation [SD], 2.70) liters/kg of body weight, the mean elimination constant (K_e) was 0.09 (SD, 0.04) h⁻¹, the rate constant for the caspofungin distribution from the central to the peripheral compartment was 0.44 (SD, 0.39) h⁻¹, and the rate constant for the caspofungin distribution from the peripheral to the central compartment was 0.46 (SD, 0.35) h⁻¹. A loading dose of 2 mg/kg on the first day, followed by 1.25 mg/kg as a maintenance dose, was chosen. With this dose, 98% of the patients were expected to reach the AUC target on the first day and 100% of the patients on the third day. The registered caspofungin dose might not be suitable for critically ill patients who were all overweight (≥120 kg), over 80% of median weight (78 kg), and around 25% of lower weight (≤50 kg). A weight-based dose regimen might be appropriate for achieving adequate exposure of caspofungin in intensive care unit patients.

Nonstationary Pharmacokinetics of Caspofungin in ICU Patients

Standard dosing of caspofungin in critically ill patients has been reported to result in lower drug exposure, which can lead to subtherapeutic 24-h area under the curve to MIC (AUC_0-24/MIC) ratios. The aim of the study was to investigate the population pharmacokinetics of caspofungin in a cohort of 30 intensive care unit patients with a suspected invasive fungal infection, with a large proportion of patients requiring extracorporeal therapies, including extracorporeal membrane oxygenation (ECMO) and continuous renal replacement therapy (CRRT). Caspofungin was administered as empirical 70 mg antifungal therapy administered intravenously (i.v.) on the first day and at 50 mg i.v. on the consecutive days once daily, and the concentrations were measured after three subsequent doses. Population pharmacokinetic data were analyzed by nonlinear mixed-effects modeling. The pharmacokinetics of caspofungin was described by two-compartment model. A particular drift of the individual clearance (CL) and the volume of distribution of the central compartment (V ₁) with time was discovered and described by including three separate typical values of CL and V ₁ in the final model. The typical CL values at days 1, 2, and 3 were 0.563 liters/h (6.7% relative standard error [6.7%RSE]), 0.737 liters/h (6.1%RSE), and 1.01 liters/h (9.1%RSE), respectively. The change in parameters with time was not explained by any of the recorded covariates. Increasing clearance with subsequent doses was associated with a clinically relevant decrease in caspofungin exposure (>20%). The use of ECMO, CRRT, albumin concentration, and other covariates did not significantly affect caspofungin pharmacokinetics. Additional pharmacokinetic studies are urgently required to assess the possible lack of acquiring steady-state and suboptimal concentrations of the drug in critically ill patients. (This study has been registered at ClinicalTrials.gov under identifier NCT03399032.).

Caspofungin: a review of its characteristics, activity, and use in intensive care units

INTRODUCTION

Candidemia is the fourth frequent reason of healthcare-related bloodstream infections in critically ill patients. For initial management of (suspected) invasive candidiasis in critically ill patients, usage of an echinocandin, e.g. caspofungin, has been recommended.

AREAS COVERED

In this study, characteristics of caspofungin and its use in intensive care unit (ICU) patients are reviewed based on an electronic search using PubMed and Google scholar.

EXPERT OPINION

Caspofungin is a semisynthetic derivative from pneumocandin B and the first member of the echinocandins that was approved by the U.S. Food and Drug Administration (FDA) to fight fungal infection. Caspofungin inhibits the enzyme β(1,3)-D-glucan synthase of the fungal cell wall resulted in inhibition of the synthesis of β(1,3)-D-glucan. For critically ill patients, inter- and intraindividual variations affect the caspofungin concentration. The incidence rates and densities of candidemia in surgical ICUs may be higher than medical ICUs resulting in a higher burden of candidemia in surgical ICUs. However, the mortality rate in surgical ICU patients with candidemia is higher than that medical ICU patients due to differences in their underlying conditions.

Caspofungin induces the release of Ca2+ ions from internal stores by activating ryanodine receptor-dependent pathways in human tracheal epithelial cells

The antimycotic drug caspofungin is known to alter the cell function of cardiomyocytes and the cilia-bearing cells of the tracheal epithelium. The objective of this study was to investigate the homeostasis of intracellular Ca²⁺ concentration ([Ca²⁺]_i) after exposure to caspofungin in isolated human tracheal epithelial cells. The [Ca²⁺]_i was measured using the ratiometric fluoroprobe FURA-2 AM. We recorded two groups of epithelial cells with distinct responses to caspofungin exposure, which demonstrated either a rapid transient rise in [Ca²⁺]_i or a sustained elevation of [Ca²⁺]_i. Both patterns of Ca²⁺ kinetics were still observed when an influx of transmembraneous Ca²⁺ ions was pharmacologically inhibited. Furthermore, in extracellular buffer solutions without Ca²⁺ ions, caspofungin exposure still evoked this characteristic rise in [Ca²⁺]_i. To shed light on the origin of the Ca²⁺ ions responsible for the elevation in [Ca²⁺]_i we investigated the possible intracellular storage of Ca²⁺ ions. The depletion of mitochondrial Ca²⁺ stores using 25 µM 2,4-dinitrophenol (DNP) did not prevent the caspofungin-induced rise in [Ca²⁺]_i, which was rapid and transient. However, the application of caffeine (30 mM) to discharge Ca²⁺ ions that were presumably stored in the endoplasmic reticulum (ER) prior to caspofungin exposure completely inhibited the caspofungin-induced changes in [Ca²⁺]_i levels. When the ER-bound IP₃ receptors were blocked by 2-APB (40 µM), we observed a delayed transient rise in [Ca²⁺]_i as a response to the caspofungin. Inhibition of the ryanodine receptors (RyR) using 40 µM ryanodine completely prevented the caspofungin-induced elevation of [Ca²⁺]_i. In summary, caspofungin has been shown to trigger an increase in [Ca²⁺]_i independent from extracellular Ca²⁺ ions by liberating the Ca²⁺ ions stored in the ER, mainly via a RyR pathway.

Caspofungin PK in critically ill patients after the first and fourth doses: suggestions for therapeutic drug monitoring?

We describe caspofungin pharmacokinetics (PK) after the first and fourth doses in 20 critically ill septic patients. Monte Carlo simulation was used to analyze the probability of target attainment (PTA) (AUC/MIC > 865) for Candida spp. Caspofungin concentrations were analyzed by HPLC in plasma and urine. A great variability in PK parameters was observed after both doses. Patients were divided in two groups according to their AUC values (AUC ≤ 75 mg h/L cut-off). In the low-AUC group Cmax, Cmin and AUC were lower, while Vd and Cl were higher than in the high-AUC group (p < 0.05, both at day 1 and 4). The mean 24-h urinary recovery of the drug was 8 ± 6.3% (day1) and 9.8 ± 6.3 (day4). Monte Carlo simulation analysis (0.03-1 mg/L MIC-range) showed that PTA was guaranteed only for MICs ≤ 0.03 mg/L in the low-AUC group, and for MICs ≤ 0.06 mg/L in the high-AUC group. No group had a PTA ≥ 90% for 0.125 mg/L MIC (the epidemiological cut-off). Mortality was higher in low-AUC group (p < 0.01). In our 'real-world' population, no clinical data can predict which patient will have lower, suboptimal caspofungin exposure, therefore we suggest TDM to optimize caspofungin therapy and reduce the risk of selecting resistances (CEAVC, 32366/2015; OSS.15.114, NCT03798600).

Therapeutic Drug Monitoring of Antifungal Drugs: Another Tool to Improve Patient Outcome?

Introduction

This study aimed to examine the relationship among adequate dose, serum concentration and clinical outcome in a non-selected group of hospitalized patients receiving antifungals.

Methods

Prospective cross-sectional study performed between March 2015 and June 2015. Dosage of antifungals was considered adequate according to the IDSA guidelines, whereas trough serum concentrations (determined with HPLC) were considered adequate as follows: fluconazole > 11 µg/ml, echinocandins > 1 µg/ml, voriconazole 1–5.5 µg/ml and posaconazole > 0.7 µg/ml.

Results

During the study period, 84 patients (65.4% male, 59.6 years) received antifungals for prophylaxis (40.4%), targeted (31.0%) and empirical therapy (28.6%). The most frequent drug was micafungin (28/84; 33.3%) followed by fluconazole (23/84; 27.4%), voriconazole (15/84; 17.9%), anidulafungin (8/84; 9.5%), posaconazole (7/84; 8.3%) and caspofungin (3/84; 3.6%). Considerable interindividual variability was observed for all antifungals with a large proportion of the patients (64.3%) not attaining adequate trough serum concentrations, despite receiving an adequate antifungal dose. Attaining the on-target serum antifungal level was significantly associated with a favorable clinical outcome (OR = 0.02; 95% CI 0.01–0.64; p = 0.03), whereas the administration of an adequate antifungal dosage was not.

Conclusions

With the standard antifungal dosage, a considerable proportion of patients have low drug concentrations, which are associated with poor clinical outcome.

Therapeutic drug monitoring of systemic antifungal agents: a pragmatic approach for adult and pediatric patients

Introduction: Therapeutic drug monitoring (TDM) has been shown to optimize the management of invasive fungal infections (IFIs), particularly for select antifungal agents with a well-defined exposure-response relationship and an unpredictable pharmacokinetic profile or a narrow therapeutic index. Select triazoles (itraconazole, voriconazole, and posaconazole) and flucytosine fulfill these criteria, while the echinocandins, fluconazole, isavuconazole, and amphotericin B generally do not do so. Given the morbidity and mortality associated with IFIs and the challenges surrounding the use of currently available antifungal agents, TDM plays an important role in therapy.Areas covered: This review seeks to describe the rationale for TDM of antifungal agents, summarize their pharmacokinetic and pharmacodynamic properties, identify treatment goals for efficacy and safety, and provide recommendations for optimal dosing and therapeutic monitoring strategies.Expert opinion: Several new antifungal agents are currently in development, including compounds from existing antifungal classes with enhanced pharmacokinetic or safety profiles as well as agents with novel targets for the treatment of IFIs. Given the predictable pharmacokinetics of these newly developed agents, use of routine TDM is not anticipated. However, expanded knowledge of exposure-response relationships of these compounds may yield a role for TDM to improve outcomes for adult and pediatric patients.

Efficacy of Delayed Therapy with Fosmanogepix (APX001) in a Murine Model of Candida auris Invasive Candidiasis

The emerging pathogenic yeast Candida auris is associated with antifungal resistance and high mortality. The novel antifungal agent manogepix (APX001A) inhibits glycosylphosphatidylinositol-anchored protein maturation and has demonstrated activity against numerous pathogenic fungi, including C. auris.

The emerging pathogenic yeast Candida auris is associated with antifungal resistance and high mortality. The novel antifungal agent manogepix (APX001A) inhibits glycosylphosphatidylinositol-anchored protein maturation and has demonstrated activity against numerous pathogenic fungi, including C. auris. Our objective was to evaluate the in vivo efficacy of fosmanogepix, the N-phosphonooxymethyl prodrug (APX001), following delayed initiation of therapy in a murine model of C. auris invasive candidiasis. Neutropenic mice were intravenously infected with a fluconazole-resistant clinical isolate of C. auris. Twenty-four hours postinoculation, treatment began with vehicle control, fosmanogepix (104 and 130 mg/kg of body weight by intraperitoneal injection three times daily, or intraperitoneal 260 mg/kg twice daily), fluconazole (20 mg/kg by oral gavage once daily), or caspofungin (intraperitoneal 10 mg/kg once daily) and continued for 7 days. Fungal burden was assessed via colony count in the kidneys and brains on day 8 in the fungal burden arm and on day 21 as the mice became moribund in the survival arm. Significant improvements in survival were observed in each group administered fosmanogepix and caspofungin. Similarly, reductions in fungal burden were also observed in both the kidneys and brains of mice treated with the highest dose of fosmanogepix in the fungal burden arm and in each fosmanogepix group and with caspofungin in the survival arm. In contrast, no improvements in survival or reductions in fungal burden were observed in mice treated with fluconazole. These results demonstrate that fosmanogepix is effective in vivo against fluconazole-resistant C. auris even when therapy is delayed.

Factors influencing caspofungin plasma concentrations in kidney transplant patients with high incidence of invasive fungal infections

WHAT IS KNOWN AND OBJECTIVE

Caspofungin is commonly used in kidney transplant patients for prophylaxis or treatment of invasive fungal infections (IFIs) caused by Candida spp. and Aspergillus spp. Factors such as concomitant medications, co-morbidity and rejection often cause caspofungin pharmacokinetic parameters alterations in kidney transplant patients. Here, we aimed to investigate factors influencing caspofungin plasma concentrations and evaluate its prophylaxis and treatment efficiency for IFIs in kidney transplant patients.

METHODS

The prophylaxis and treatment efficiency of caspofungin for IFIs were assessed in 164 kidney transplant patients in the study. Six hundred and fifty-two caspofungin trough concentrations (C_min ) from the 164 patients were monitored by the liquid chromatography-tandem mass spectrometry method. Basic demographic variables, baseline disease, surgery, rejection, indwelling catheter, coinfection, concomitant medication and other caspofungin-related factors were collected. Univariate and multivariate analyses were used to assess factors influencing caspofungin plasma concentrations.

RESULTS AND DISCUSSION

The success rates were 94.96% (132/139) for caspofungin prevention and 80% (20/25) for caspofungin for IFIs. Caspofungin C_min in the kidney recipients varied largely compared with healthy volunteers (0.10-12.25 mg/L vs. 1.12-1.78 mg/L). Caspofungin C_min significantly increased in patients with continuous renal replacement therapy before transplantation (P = .001), concomitant medication of cyclosporine A (CsA, P = .009), ALB concentration of > 30 g/L (P = .019).

WHAT IS NEW AND CONCLUSION

This is an uncontrolled observational study of caspofungin as prophylaxis or treatment for IFIs in kidney transplant patients. Caspofungin could be an effective and well-tolerated option for antifungal prophylaxis and treatment in kidney transplant patients, and a number of factors could influence caspofungin C_min in these patients.

Defining breakthrough invasive fungal infection-Position paper of the mycoses study group education and research consortium and the European Confederation of Medical Mycology

Breakthrough invasive fungal infections (IFIs) have emerged as a significant problem in patients receiving systemic antifungals; however, consensus criteria for defining breakthrough IFI are missing. This position paper establishes broadly applicable definitions of breakthrough IFI for clinical research. Representatives of the Mycoses Study Group Education and Research Consortium (MSG-ERC) and the European Confederation of Medical Mycology (ECMM) reviewed the relevant English literature for definitions applied and published through 2018. A draft proposal for definitions was developed and circulated to all members of the two organisations for comment and suggestions. The authors addressed comments received and circulated the updated document for approval. Breakthrough IFI was defined as any IFI occurring during exposure to an antifungal drug, including fungi outside the spectrum of activity of an antifungal. The time of breakthrough IFI was defined as the first attributable clinical sign or symptom, mycological finding or radiological feature. The period defining breakthrough IFI depends on pharmacokinetic properties and extends at least until one dosing interval after drug discontinuation. Persistent IFI describes IFI that is unchanged/stable since treatment initiation with ongoing need for antifungal therapy. It is distinct from refractory IFI, defined as progression of disease and therefore similar to non-response to treatment. Relapsed IFI occurs after treatment and is caused by the same pathogen at the same site, although dissemination can occur. These proposed definitions are intended to support the design of future clinical trials and epidemiological research in clinical mycology, with the ultimate goal of increasing the comparability of clinical trial results.

Efficacy of humanized single large doses of caspofungin on the lethality and fungal tissue burden in a deeply neutropenic murine model against Candida albicans and Candida dubliniensis

Background

Echinocandins are the first-line therapy for treatment of invasive Candida infections, but the mortality rate remains high, calling for novel strategies. Giving single larger echinocandin doses infrequently is an alternative regimen. Our aim was to test this novel approach in a neutropenic murine model.

Materials and methods

We compared the in vivo efficacy of single 10 and 40 mg/kg of caspofungin (2.5× and 10× the normal humanized dose) to that of the same cumulative doses of daily 2 and 8 mg/kg doses for 5 days against 2 each of wild-type C. albicans and C. dubliniensis as well as echinocandin resistant C. albicans. As a comparator, we tested daily 1 mg/kg amphotericin B.

Results

In lethality experiments, all caspofungin and amphotericin B regimens improved survival against wild-type C. albicans and C. dubliniensis clinical isolates (P<0.0001) and decreased the mean fungal kidney burdens of both species compared to controls. However, fungal kidney burden decreases were not always statistically significant, especially with single 10 or 40 mg/kg caspofungin doses. Amphotericin B was the least active drug against wild-type C. albicans. Against echinocandin-resistant strains, monodose 40 mg/kg caspofungin and 1 mg/kg of daily amphotericin B were effective in lethality experiments. Although, significant kidney CFU decreases were never found, except for amphotericin B against one of the isolates (p<0.05 at day 3 and p<0.001 at day 6).

Conclusion

Single 40 mg/kg caspofungin and 1 mg/kg amphotericin B proved to be effective in the lethality experiments against wild-type and echinocandin-resistant C. albicans and wild-type C. dubliniensis. This was not always shown regarding fungal tissue burdens. Single caspofungin doses used in mice in this study are attainable in humans as well, suggesting a potential place of this dosing strategy not only in prevention but also in curative treatment of evolved invasive Candida infections.

Antifungal Drugs Influence Neutrophil Effector Functions

There is a growing body of evidence for immunomodulatory side effects of antifungal agents on different immune cells, e.g., T cells. Therefore, the aim of our study was to clarify these interactions with regard to the effector functions of polymorphonuclear neutrophils (PMN). Human PMN were preincubated with fluconazole (FLC), voriconazole (VRC), posaconazole (POS), isavuconazole (ISA), caspofungin (CAS), micafungin (MFG), conventional amphotericin B (AMB), and liposomal amphotericin B (LAMB). PMN then were analyzed by flow cytometry for activation, degranulation, and phagocytosis and by dichlorofluorescein assay to detect reactive oxygen species (ROS). Additionally, interleukin-8 (IL-8) release was measured by enzyme-linked immunosorbent assay. POS led to enhanced activation, degranulation, and generation of ROS, whereas IL-8 release was reduced. In contrast, ISA-pretreated PMN showed decreased activation signaling, impaired degranulation, and lower generation of ROS. MFG caused enhanced expression of activation markers but impaired degranulation, phagocytosis, generation of ROS, and IL-8 release. CAS showed increased phagocytosis, whereas degranulation and generation of ROS were reduced. AMB led to activation of almost all effector functions besides impaired phagocytosis, whereas LAMB did not alter any effector functions. Independent from class, antifungal agents show variable influence on neutrophil effector functions in vitro Whether this is clinically relevant needs to be clarified.

Evaluation of the effectiveness of caspofungin against febrile neutropenia and the factors related to the alteration in its plasma concentration

Caspofungin (CPFG) is an echinocandin antifungal agent that inhibits the synthesis of β-1, 3-D-glucan, a critical component of the cell wall of target fungi. Several clinical studies have confirmed the efficacy and safety of CPFG in patients with febrile neutropenia (FN); however, there are no reports available in Japanese patients with FN. Therefore, we investigated the therapeutic efficacy and pharmacokinetics of CPFG as an empirical therapy in a Japanese hospital. Twenty-four Japanese patients, who were diagnosed with FN at Gifu University Hospital from February 2014 to August 2017, were enrolled. Blood samples were collected at the end of CPFG dosing (0.5 h after the infusion) on day 1 and immediately prior to the next infusion on days 2, 3, and 4. The concentration of CPFG in plasma was measured by high-performance liquid chromatography. The efficacy was assessed by five of the component endpoints, and safety was monitored according to the Common Terminology Criteria for Adverse Events. CPFG showed an excellent effect against FN (75%, 18/24), without any serious hepatic or renal toxicity. Regarding the pharmacokinetics, the plasma concentration of CPFG was significantly correlated with body weight; although, no correlation was observed between the plasma concentration of CPFG and the other factors investigated, such as gender or laboratory results. These results suggest the high efficacy, safety, and tolerability of CPFG as an empirical antifungal therapy for Japanese patients with FN.

Overview of antifungal dosing in invasive candidiasis

In the past, most antifungal therapy dosing recommendations for invasive candidiasis followed a 'one-size fits all' approach with recommendations for lowering maintenance dosages for some antifungals in the setting of renal or hepatic impairment. A growing body of pharmacokinetic/pharmacodynamic research, however now points to a widespread 'silent epidemic' of antifungal underdosing for invasive candidiasis, especially among critically ill patients or special populations who have altered volume of distribution, protein binding and drug clearance. In this review, we explore how current adult dosing recommendations for antifungal therapy in invasive candidiasis have evolved, and special populations where new approaches to dose optimization or therapeutic drug monitoring may be needed, especially in light of increasing antifungal resistance among Candida spp.

Caspofungin Modulates Ryanodine Receptor-Mediated Calcium Release in Human Cardiac Myocytes

Recent studies showed that critically ill patients might be at risk for hemodynamic impairment during caspofungin (CAS) therapy. The aim of our present study was to examine the mechanisms behind CAS-induced cardiac alterations. We revealed a dose-dependent increase in intracellular Ca²⁺ concentration ([Ca²⁺]_i) after CAS treatment. Ca²⁺ ions were found to be released from intracellular caffeine-sensitive stores, most probably via the activation of ryanodine receptors.

Whole-body physiology-based pharmacokinetics of caspofungin for general patients, intensive care unit patients and hepatic insufficiency patients

Caspofungin is an echinocandin antifungal agent licensed as a first-line therapy for invasive candidiasis in patients with moderate to severe illness or recent exposure to azoles. In this study we developed a whole-body physiology-based pharmacokinetics (WB-PBPK) model to predict the pharmacokinetics (PK) of caspofungin, and combined with Monte Carlo simulation (MCS) to optimize clinical dosage regimens of caspofungin in different kinds of patients. A WB-PBPK model of caspofungin was built and validated with raw data from 4 previous trials of general patients, intensive care unit (ICU) patients with Child-Pugh B, ICU patients on continuous renal replacement therapy, mild and moderate hepatic insuffciency (HI) patients. MCS was used to optimize clinical dosage regimens of caspofungin in these patients. A cumulative fraction of response (CFR) value of ≥90% was considered to be the minimum for achieving optimal empirical therapy. The simulated results of the WB-PBPK model were in good agreement with observed values of all trials. For general and ICU patients with caspofungin 70/50 mg, AUC and Cmax were decreased with the increase of body weight (BW) and showed great variation. MCS showed all general patients achieved CFR≥90% regardless of BW. But not all ICU patients with higher BW (≥70 kg) could achieve CFR≥90%. Compared with standard dosage regimens in general patients, caspofungin 70/35 mg in ICU patients with Child-Pugh B achieved significantly decreased AUC and Cmax, but obtained similar AUC and Cmax in moderate HI patients with Child-Pugh B. The WB-PBPK model of caspofungin is able to predict PK of all populations correctly. The combined WB-PBPK model with MCS can successfully optimize clinical dosage regimens of caspofungin in all patient populations.

Development and validation of a liquid chromatography/tandem mass spectrometry method for determination of caspofungin in dried blood spots

RATIONALE

A liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for quantification of caspofungin in dried blood spots (DBS) was developed and validated.

METHODS

The DBS samples were prepared by spotting whole blood onto Whatman 903 filter paper, drying at room temperature and extracting with 50% methanol and further cleaned by protein precipitation with acetonitrile. Roxithromycin was selected as internal standard, and the separation of the analytes with endogenous ingredients was accomplished on a Hypersil GOLD aQ column with a mobile phase composed of 0.1% formic acid (v/v) and methanol in gradient mode. The detection of the analytes was performed on a triple quadrupole mass spectrometer in positive electrospray ionization mode, and the following selective reaction monitoring (SRM) transitions were monitored: m/z 547.6 → 538.7 and 837.4→ 679.4 for quantification of caspofungin and the internal standard, respectively.

RESULTS

The total analytical time was 8 min for each run. The calibration curve exhibited a good linearity over the range from 0.2 to 20 μg/mL and the lower limit of quantification (LLOQ) was 0.2 μg/mL for caspofungin in DBS. The recoveries of caspofungin ranged from 62.64% to 76.69%, and no obvious matrix effect was observed. The intra- and inter-day precision and accuracy were within acceptable limits, and caspofungin in DBS was stable after storage at room temperature for 24 h and at -80°C for 30 days. There was no evident effect of the hematocrit value on the analysis of caspofungin.

CONCLUSIONS

The proposed method presents an alternative to the conventional venous sampling method, and was successfully utilized for pharmacokinetics study of caspofungin in ICU patients.

Antifungal Drugs in Newborns and Children

Invasive fungal infections are a significant cause of morbidity and mortality in infants and children. Early diagnosis is critical, and treatment with the appropriate drug and dose should be initiated promptly. Although an increasing number of studies have examined dosing of antifungals in this population, pediatric safety and efficacy data are lacking.

Pharmacokinetics of antifungal drugs: practical implications for optimized treatment of patients

Introduction

Because of the high mortality of invasive fungal infections (IFIs), appropriate exposure to antifungals appears to be crucial for therapeutic efficacy and safety.

Materials and methods

This review summarises published pharmacokinetic data on systemically administered antifungals focusing on co-morbidities, target-site penetration, and combination antifungal therapy.

Conclusions and discussion

Amphotericin B is eliminated unchanged via urine and faeces. Flucytosine and fluconazole display low protein binding and are eliminated by the kidney. Itraconazole, voriconazole, posaconazole and isavuconazole are metabolised in the liver. Azoles are substrates and inhibitors of cytochrome P450 (CYP) isoenzymes and are therefore involved in numerous drug–drug interactions. Anidulafungin is spontaneously degraded in the plasma. Caspofungin and micafungin undergo enzymatic metabolism in the liver, which is independent of CYP. Although several drug–drug interactions occur during caspofungin and micafungin treatment, echinocandins display a lower potential for drug–drug interactions. Flucytosine and azoles penetrate into most of relevant tissues. Amphotericin B accumulates in the liver and in the spleen. Its concentrations in lung and kidney are intermediate and relatively low myocardium and brain. Tissue distribution of echinocandins is similar to that of amphotericin. Combination antifungal therapy is established for cryptococcosis but controversial in other IFIs such as invasive aspergillosis and mucormycosis.

Pharmacokinetics of caspofungin acetate to guide optimal dosing in cats

Cats are the most common mammal to develop invasive fungal rhinosinusitis caused by cryptic species in Aspergillus section Fumigati that are resistant to azoles but susceptible to caspofungin. In this study nonlinear mixed-effects pharmacokinetic modeling and simulation was used to investigate caspofungin pharmacokinetics and explore dosing regimens in cats using caspofungin minimum effective concentrations (MECs). Plasma concentrations in healthy cats were determined using HPLC-MS/MS after administration of a single and seven consecutive daily intravenous doses of 1 mg/kg caspofungin. In the final pharmacokinetic model an optimum maximum concentration (C_max): MEC ratio of 10–20 was used to guide caspofungin efficacy. Simulations were performed for dosing regimens (doses 0.25–2 mg/kg and 6–72 h dosing intervals) with and without inclusion of a loading dose. Using a 1 mg/kg dose C_max first dose was 14.8 μg/mL, C_max at steady state was 19.8 μg/mL, C_min was 5 μg/mL and C_max: MEC was >20 in 42.6% of cats after multiple doses. An optimal C_max: MEC ratio was achieved in caspofungin simulations using 0.75 mg/kg q 24 h or 1 mg/kg q 72h. However, at 1 mg/kg q 72h, C_min was < MEC (<1 μg/mL) in over 95% of the population. Using a loading dose of 1 mg/kg and a daily dose of 0.75 mg/kg thereafter, the Cmax: MEC was optimal and C_min was > 2.5 μg/mL for 98% of the population. Based on the modeling data this dosing regimen is likely to achieve target therapeutic concentrations, meet the proposed C_max: MEC window and provide consistent exposure between doses.

Low Caspofungin Exposure in Patients in Intensive Care Units

In critically ill patients, drug exposure may be influenced by altered drug distribution and clearance. Earlier studies showed that the variability in caspofungin exposure was high in intensive care unit (ICU) patients. The primary objective of this study was to determine if the standard dose of caspofungin resulted in adequate exposure in critically ill patients. A multicenter prospective study in ICU patients with (suspected) invasive candidiasis was conducted in the Netherlands from November 2013 to October 2015. Patients received standard caspofungin treatment, and the exposure was determined on day 3 of treatment. An area under the concentration-time curve from 0 to 24 h (AUC_0-24) of 98 mg · h/liter was considered adequate exposure. In case of low exposure (i.e., <79 mg · h/liter, a ≥20% lower AUC_0-24), the caspofungin dose was increased and the exposure reevaluated. Twenty patients were included in the study, of whom 5 had a positive blood culture. The median caspofungin AUC_0-24 at day 3 was 78 mg · h/liter (interquartile range [IQR], 69 to 97 mg · h/liter). A low AUC_0-24 (<79 mg · h/liter) was seen in 10 patients. The AUC_0-24 was significantly and positively correlated with the caspofungin dose in mg/kg/day (P = 0.011). The median AUC_0-24 with a caspofungin dose of 1 mg/kg was estimated using a pharmacokinetic model and was 114.9 mg · h/liter (IQR, 103.2 to 143.5 mg · h/liter). In conclusion, the caspofungin exposure in ICU patients in this study was low compared with that in healthy volunteers and other (non)critically ill patients, most likely due to a larger volume of distribution. A weight-based dose regimen is probably more suitable for patients with substantially altered drug distribution. (This study has been registered at ClinicalTrials.gov under registration no. NCT01994096.).

Echinocandins: The Expanding Antifungal Armamentarium

The echinocandins are large lipopeptide molecules that, since their discovery approximately 41 years ago, have emerged as important additions to the expanding armamentarium against invasive fungal diseases. Echinocandins exert in vitro and in vivo fungicidal action against most Candida species and fungistatic action against Aspergillus species. However, the population of patients at risk for developing invasive fungal infections continues to increase. New therapeutic strategies using echinocandins are needed to improve clinical outcomes in patients with invasive fungal disease.

[Echinocandins: Applied pharmacology]

The echinocandins share pharmacodynamic properties, although there are some interesting differences in their pharmacokinetic behaviour in the clinical practice. They are not absorbed by the oral route. They have a somewhat special distribution in the organism, as some of them can reach high intracellular concentrations while, with some others, the concentration is reduced. They are highly bound to plasma proteins, thus it is recommended to administer a loading dose for anidulafungin and caspofungin, although this procedure is not yet clear with micafungin. Echinocandins are excreted via a non-microsomal metabolism, so the urinary concentration is very low. Some carrier proteins that take part in the biliary clearance process are probably involved in the interactions described with caspofungin and micafungin. These two drugs must be used with caution in patients with severely impaired hepatic function, while all of them can be used without special precautions when there is renal impairment or the patient requires renal replacement therapy.

Pharmacokinetic/pharmacodynamic adequacy of echinocandins against Candida spp. in intensive care unit patients and general patient populations

This study evaluated whether contemporary echinocandin regimens achieved pharmacokinetic/pharmacodynamic targets in ICU patients and general patient populations (GPPs) and assessed caspofungin (CAS) regimens in hepatic impairment (HI) patients. A Monte Carlo simulation was performed using previously published data. Recommended dosing regimens of echinocandins in ICU patients, GPPs and healthy volunteers were evaluated: 70mg loading dose then 50mg maintenance dose (70/50mg) for CAS; 100mg q24h for micafungin (MCF); and 200/100mg for anidulafungin (ANF). Moreover, CAS 70mg and 100mg q24h in GPPs, and CAS 70/50mg and 70/35mg in mild and moderate HI patients, respectively, were evaluated. Cumulative fraction of response (CFR) was calculated for each dosing regimen. For Candida albicans, CFRs for the recommended doses of CAS, MCF and ANF were 95.8%, 13.5% and 50.5% in ICU patients and 96.3%, 42.4% and 61.6% in GPPs, respectively; for Candida glabrata, CFRs were 99.4%, 90.6% and 44.6% in ICU patients and 99.5%, 97.1% and 59.8% in GPPs. For Candida parapsilosis, CFRs of echinocandins for standard regimens were <70%; only CAS 100mg q24h achieved the target CFR. CAS 70/50mg and 70/35mg in mild and moderate HI patients were appropriate. Considerable interindividual variability was observed. For C. albicans and C. glabrata, CAS is good choice both for ICU and other patient populations, but for C. parapsilosis an increased dose should be considered. For MCF and ANF, administering higher doses with longer dosing intervals achieves better target attainment and should be investigated in clinical trials.

Albumin Enhances Caspofungin Activity against Aspergillus Species by Facilitating Drug Delivery to Germinating Hyphae

The modest in vitro activity of echinocandins against Aspergillus implies that host-related factors augment the action of these antifungal agents in vivo. We found that, in contrast to the other antifungal agents (voriconazole, amphotericin B) tested, caspofungin exhibited a profound increase in activity against various Aspergillus species under conditions of cell culture growth, as evidenced by a ≥4-fold decrease in minimum effective concentrations (MECs) (P = 0. 0005). Importantly, the enhanced activity of caspofungin against Aspergillus spp. under cell culture conditions was strictly dependent on serum albumin and was not observed with the other two echinocandins, micafungin and anidulafungin. Of interest, fluorescently labeled albumin bound preferentially on the surface of germinating Aspergillus hyphae, and this interaction was further enhanced upon treatment with caspofungin. In addition, supplementation of cell culture medium with albumin resulted in a significant, 5-fold increase in association of fluorescently labeled caspofungin with Aspergillus hyphae (P < 0.0001). Collectively, we found a novel synergistic interaction between albumin and caspofungin, with albumin acting as a potential carrier molecule to facilitate antifungal drug delivery to Aspergillus hyphae.

Caspofungin: Pharmacodynamics, pharmacokinetics, clinical uses and treatment outcomes

Over the past decade, echinocandins have emerged as first-line antifungal agents for many Candida infections. The echinocandins have a unique mechanism of action, inhibiting the synthesis of β-1,3-d-glucan polymers, key components of the cell wall in pathogenic fungi. Caspofungin was the first echinocandin antifungal agent to become licensed for use. The objectives of this review are to summarize the existing published data on caspofungin, under the subject headings of chemistry and mechanism of action, spectrum of activity, pharmacodynamics, pharmacokinetics, clinical studies, safety, drug interactions, dosing, and an overview of the drug's current place in therapy.

Influence of echinocandin administration on hemodynamic parameters in medical intensive care unit patients: a single center prospective study

PURPOSE

Fungal infections present a constant risk to critically ill and immunocompromised patients. Therefore, treatment guidelines recommend echinocandins as first-line antifungals in critically ill patients to improve patient outcomes. Echinocandins are usually well tolerated; nevertheless, rare adverse events can occur. There are reports of temporary deterioration of hemodynamic parameters during loading doses, especially in critically ill patients. The objective of this study is to analyze the hemodynamic changes during administration of the echinocandin antifungals, caspofungin and anidulafungin, in medical intensive care unit patients.

METHODS

A prospective study in medical ICU patients receiving echinocandins was monitored using single-indicator transpulmonary thermodilution (TPTD). TPTD measurements were performed immediately before, directly after, and 4 h after echinocandins on two following days.

RESULTS

Mean arterial pressure and also diastolic blood pressure showed significant changes (p < 0.042 and p < 0.007) after echinocandin application in the measurement immediately after application, but not after 4 h. Basic hemodynamic parameters as well as the TPTD-derived cardiac function parameters did not significantly change after echinocandin application at all. In patients with the need for norepinephrine therapy, the vasopressor dose was not statistically significantly altered.

CONCLUSION

To conclude, administration of echinocandins in this observed study population is safe, even in severely critically ill patients if application rules of these agents are followed. However, adverse effects could be observed and practitioners should be cognizant of these effects. These observations can be optimized by high-level assessments, such as the pulse contour cardiac output monitoring, and clinicians should continue to be vigilant with cardiac monitoring of patients receiving echinocandin antifungals.

Dose escalation studies with caspofungin against Candida glabrata

Echinocandins are recommended as first-line agents against invasive fungal infections caused by Candida glabrata, which still carry a high mortality rate. Dose escalation of echinocandins has been suggested to improve the clinical outcome against C. glabrata. To address this possibility, we performed in vitro and in vivo experiments with caspofungin against four WT C. glabrata clinical isolates, a drug-susceptible ATCC 90030 reference strain and two echinocandin-resistant strains with known FKS mutations. MIC values for the clinical isolates in RPMI 1640 were ≤ 0.03 mg l(-1 ) but increased to 0.125-0.25 mg l(-1 )in RPMI 1640+50% serum. In RPMI 1640+50% serum, the replication of C. glabrata was weaker than in RPMI 1640.Caspofungin in RPMI 1640 at 1 and 4 mg l(-1) showed a fungicidal effect within 7 h against three of the four clinical isolates but was only fungistatic at 16 and 32 mg l(-1) (paradoxically decreased killing activity). In RPMI 1640+50% serum, caspofungin at ≥ 1 mg l(-1) was rapidly fungicidal (within 3.31 h) against three of the four isolates. In a profoundly neutropenic murine model, all caspofungin doses (1, 2, 3, 5 and 20 mg kg(-1) daily) decreased the fungal tissue burdens significantly (P < 0.05-0.001) without statistical differences between doses, but the mean fungal tissue burdens never fell below 105 cells (g tissue)(-1). The echinocandin-resistant strains were highly virulent in animal models and all doses were ineffective. These results confirm the clinical experience that caspofungin dose escalation does not improve efficacy.

Impact of special patient populations on the pharmacokinetics of echinocandins

Echinocandins belong to the class of antifungal agents. Currently, three echinocandin drugs are licensed for intravenous treatment of invasive fungal infections: anidulafungin, caspofungin and micafungin. While their antifungal activity overlaps, there are substantial differences in pharmacokinetics (PK). Numerous factors may account for variability in PK of echinocandins including age (pediatrics vs adults), body surface area and body composition (normal weight vs obesity), disease status (e.g., critically ill and burn patients) and organ dysfunction (kidney and liver impairment). Subsequent effects of altered exposure might impact efficacy and safety. Knowledge of PK behavior is crucial in optimal clinical utilization of echinocandin in a specific patient or patient population. This review provides up-to-date information on PK data of anidulafungin, caspofungin and micafungin in special patient populations. Patient populations addressed are neonates, children and adolescents, obese patients, patients with hepatic or renal impairment, critically ill patients (including burn patients) and patients with hematological diseases.

Advances in the treatment of invasive neonatal candidiasis

INTRODUCTION

Invasive candidiasis is responsible for ∼ 10% of nosocomial sepsis in very-low-birth-weight infants and is associated with substantial morbidity and mortality. Over the last two decades, the antifungal armamentarium against Candida spp. has increased; however, efficacy and safety studies in this population are lacking.

AREAS COVERED

We reviewed the medical literature and extracted information on clinical and observational studies evaluating the use of antifungal agents in neonates with invasive candidiasis.

EXPERT OPINION

Efficacy and safety data for antifungals in neonates are lacking, and the majority of studies conducted to date have concentrated on pharmacokinetic/pharmacodynamic evaluations. Unlike other anti-infective agents, efficacy data in the setting of neonatal candidiasis cannot be extrapolated from adult studies due to differences in the pathophysiology of the disease in this population relative to older children and adults. Data for amphotericin B deoxycholate, fluconazole, and micafungin suggest that these are the current agents of choice for this disease in neonates until data for newer antifungal agents become available. For prophylaxis, data from fluconazole randomized controlled trials will be submitted to the regulatory agencies for labeling. Ultimately, the field of therapeutics for neonatal candidiasis will require multidisciplinary collaboration given the numerous challenges associated with conducting clinical trials in neonates.

Role of therapeutic drug monitoring in pulmonary infections: use and potential for expanded use of dried blood spot samples

Respiratory tract infections are among the most common infections in men. We reviewed literature to document their pharmacological treatments, and the extent to which therapeutic drug monitoring (TDM) is needed during treatment. We subsequently examined potential use of dried blood spots as sample procedure for TDM. TDM was found to be an important component of clinical care for many (but not all) pulmonary infections. For gentamicin, linezolid, voriconazole and posaconazole dried blood spot methods and their use in TDM were already evident in literature. For glycopeptides, β-lactam antibiotics and fluoroquinolones it was determined that development of a dried blood spot (DBS) method could be useful. This review identifies specific antibiotics for which development of DBS methods could support the optimization of treatment of pulmonary infections.

Pharmacokinetic variability and exposures of fluconazole, anidulafungin, and caspofungin in intensive care unit patients: Data from multinational Defining Antibiotic Levels in Intensive care unit (DALI) patients Study

Introduction

The objective of the study was to describe the pharmacokinetics (PK) of fluconazole, anidulafungin, and caspofungin in critically ill patients and to compare with previously published data. We also sought to determine whether contemporary fluconazole doses achieved PK/pharmacodynamic (PD; PK/PD) targets in this cohort of intensive care unit patients.

Methods

The Defining Antibiotic Levels in Intensive care unit patients (DALI) study was a prospective, multicenter point-prevalence PK study. Sixty-eight intensive care units across Europe participated. Inclusion criteria were met by critically ill patients administered fluconazole (n = 15), anidulafungin (n = 9), and caspofungin (n = 7). Three blood samples (peak, mid-dose, and trough) were collected for PK/PD analysis. PK analysis was performed by using a noncompartmental approach.

Results

The mean age, weight, and Acute Physiology and Chronic Health Evaluation (APACHE) II scores of the included patients were 58 years, 84 kg, and 22, respectively. Fluconazole, caspofungin, and anidulafungin showed large interindividual variability in this study. In patients receiving fluconazole, 33% did not attain the PK/PD target, ratio of free drug area under the concentration-time curve from 0 to 24 hours to minimum inhibitory concentration (fAUC_0–24/MIC) ≥100. The fluconazole dose, described in milligrams per kilogram, was found to be significantly associated with achievement of fAUC_0–24/MIC ≥100 (P = 0.0003).

Conclusions

Considerable interindividual variability was observed for fluconazole, anidulafungin, and caspofungin. A large proportion of the patients (33%) receiving fluconazole did not attain the PK/PD target, which might be related to inadequate dosing. For anidulafungin and caspofungin, dose optimization also appears necessary to minimize variability.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-0758-3) contains supplementary material, which is available to authorized users.

A sensitive liquid chromatography-tandem mass spectrometry method for monitoring the caspofungin trough plasma concentration and its association with caspofungin efficacy in intensive-care-unit patients

LC-MS/MS method for monitoring the caspofungin trough plasma concentration and its association efficacy in intensive-care-unit patients.

Cardiac effects of echinocandins after central venous administration in adult rats

Echinocandins have become the agents of choice for early and specific antifungal treatment in critically ill patients. In vitro studies and clinical case reports revealed a possible impact of echinocandin treatment on cardiac function. The aim of our study was to evaluate echinocandin-induced cardiac failure. Using an in vivo rat model, we assessed hemodynamic parameters and time to hemodynamic failure after central venous application (vena jugularis interna) of anidulafungin (low-dose group, 2.5 mg/kg body weight [BW]; high-dose group, 25 mg/kg BW), caspofungin (low-dose group, 0.875 mg/kg BW; high-dose group, 8.75 mg/kg BW), micafungin (low-dose group, 3 mg/kg BW; high-dose group, 30 mg/kg BW), and placebo (0.9% sodium chloride). Left ventricular heart tissue was collected to determine mitochondrial enzyme activity via spectrophotometric measurements. mRNA expression of transcriptional regulators and primary mitochondrial transcripts, mitochondrial DNA (mtDNA) content, and citrate synthase activity were also explored. Animals receiving high-dose anidulafungin or caspofungin showed an immediate decrease in hemodynamic function. All of the subjects in these groups died during the observation period. Every animal in the untreated control group survived (P < 0.001). Hemodynamic failure was not noticed in the anidulafungin and caspofungin low-dose groups. Micafungin had no impact on cardiac function. In analyzing mitochondrial enzyme activity and mitochondrial transcripts, we found no association between echinocandin administration and the risk for hemodynamic failure. Further experimental studies are needed to elucidate the underlying mechanisms involved in cardiotoxic echinocandin effects. In addition, randomized controlled clinical trials are needed to explore the clinical impact of echinocandin treatment in critically ill patients.