Exposure-response of posaconazole used for prophylaxis against invasive fungal infections: evaluating the need to adjust doses based on drug concentrations in plasma

Efficacy, safety and feasibility of antifungal prophylaxis with posaconazole tablet in paediatric patients after haematopoietic stem cell transplantation

PURPOSE

Paediatric recipients of haematopoietic stem cell transplantation (HSCT) have a high risk for invasive fungal infections. Posaconazole oral suspension has proven to be effective in antifungal prophylaxis in adult and paediatric patients. A new posaconazole tablet formulation with absorption independent of the gastric conditions was approved by the FDA in 2013. This is the first report on the use of posaconazole tablets in paediatric patients.

METHODS

This single-centre study included 63 paediatric patients with haemato-oncological malignancies who received posaconazole for antifungal prophylaxis after HSCT. They were analysed for efficacy, feasibility and the safety of posaconazole. Out of 63 patients, 31 received posaconazole oral suspension and 32 received posaconazole tablets up to 200 days after transplantation. Analyses of the posaconazole trough levels were determined.

RESULTS

No possible, probable or proven invasive fungal infection was observed in either group. Posaconazole trough levels were significantly higher in the tablet group than in the suspension group at all analysed time points. Drug-related adverse events were similarly low in both groups.

CONCLUSIONS

Posaconazole tablets are effective in preventing invasive fungal infections in paediatric patients. As early as day 3 after starting posaconazole tablets, over 50% of the posaconazole trough levels were >500 ng/mL, while this was observed on day 14 after start with posaconazole suspension. The administration of posaconazole tablets was safe, effective and feasible as antifungal prophylaxis in paediatric patients after HSCT.

Clinical hepatotoxicity associated with antifungal agents

INTRODUCTION

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

Therapeutic drug monitoring of posaconazole oral suspension in paediatric patients younger than 13 years of age: a retrospective analysis and literature review

WHAT IS KNOWN AND OBJECTIVE

Posaconazole is an extended-spectrum triazole antifungal with activity against a variety of clinically significant yeasts and moulds. Posaconazole is not currently approved by the U.S. Food and Drug Administration for use in children younger than 13 years of age. Our primary objective was to describe the dosing and observed trough concentrations with posaconazole oral suspension in paediatric patients at the National Institutes of Health Clinical Center (Bethesda, MD).

METHODS

This retrospective single-centre study reviewed paediatric patients younger than 13 years of age initiated on posaconazole oral suspension. Patients were included if they were initiated on posaconazole for prophylaxis or treatment for fungal infections from September 2006 through March 2013 with at least one trough concentration collected after at least 7 days of therapy.

RESULTS AND DISCUSSION

A total of 20 male patients were included, of whom 15 (75%) had chronic granulomatous disease. The median age of patients was 6·5 years (range: 2·8-10·7). A total of 79 posaconazole trough concentrations were measured in patients receiving posaconazole as prophylaxis (n = 8) or treatment (n = 12). Posaconazole dose referenced to total body weight ranged from 10·0 to 49·2 mg/kg/day. Posaconazole trough concentrations ranged from undetectable (<50 ng/mL) up to 3620 ng/mL and were ≥500, ≥700 and ≥1250 ng/mL in 95%, 60% and 25% of patients, respectively.

WHAT IS NEW AND CONCLUSIONS

Patients younger than 13 years of age had highly variable trough concentrations, and recommendations for the appropriate dosing of posaconazole oral suspension remain challenging. Until studies are conducted to determine the appropriate dosing of posaconazole in this patient population, therapeutic drug monitoring should be considered to ensure adequate posaconazole exposure.

Failure to achieve therapeutic levels with high-dose posaconazole tablets potentially due to enhanced clearance

Aim To describe a case of persistent sub-therapeutic posaconazole levels in setting of salvage chemotherapy for relapsed acute myeloid leukemia. Case details A 57-year-old male was admitted for the management of relapsed acute myeloid leukemia and ongoing pulmonary aspergillosis. While continuing on posaconazole tablet 300 mg daily, he received a course of salvage chemotherapy. The initial steady state posaconazole trough level was therapeutic at 0.84 mg/L (target >0.70 mg/L). However, after five days, the level had dropped to 0.40 mg/L, coinciding with hyperbilirubinemia and hypoalbuminemia. Bilirubin level peaked at 36 µm/L (normal high <20 µm/L), albumin levels were consistently low, averaging at 25 g/L (range 33-46 g/L). The patient had been compliant and there were no underlying gastrointestinal conditions identified which might have potentially affected posaconazole absorption. Outcome An increase in posaconazole dose failed to achieve target levels and treatment was changed to voriconazole. However, levels were surprisingly supra-therapeutic, resulting in side effects and substantial dose reduction was required. Conclusion Failure to achieve target posaconazole levels despite increased dosing may be attributed to factors other than impaired oral absorption. Enhanced metabolism and clearance could be associated with hypoalbuminemia and hyperbilirubinemia. Further case studies, including PK modelling, are required to confirm this effect.

[Standardisation and validation of an HPLC method for determining serum posaconazole levels in Colombia]

BACKGROUND

Colombia currently does not have a specialised service for measuring antifungal levels in serum, which is of prime importance for the proper treatment and correct management of invasive fungal infections.

AIMS

To standardise and validate a simple, sensitive, and specific protocol, based on high performance liquid chromatography, complying with the parameters recommended by the Food and Drug Administration, to detect, identify, and quantify serum concentrations of posaconazole.

METHODS

A high performance liquid chromatography Agilent series-1 200 equipment was used with ultraviolet diode array detector and analytical column-Eclipse XDB-C18. Posaconazole-SCH56592 (batch IRQ-PAZ-10-X-103) was used as the primary control and itraconazole (batch ZR051211PUC921) was used as an internal control. The validation was performed taking into account all criteria recommended by the Food and Drug Administration (selectivity, calibration curves, recovery, accuracy, precision, sensitivity, reproducibility, and stability of the sample).

RESULTS

The most suitable chromatographic conditions were the following: column temperature 25°C, ultraviolet detection at 261nm, 50μl injection volume, flow volume 0.8ml/min, 10min running time, mobile phase of acetonitrile:water (70:30), and final retention times of 3.4 and 7.2min for posaconazole and itraconazole, respectively, with a wide and reliable quantification range (0.125μg/ml to 16μg/ml). Using these parameters, the method was selective, R² in the calibration curves was≥0.99, and the percentage recovery was 98.7%, with a coefficient of variation less than 10%. The relative error for accuracy and the coefficient of variation for precision were less than 15%, all meeting the acceptance criteria recommended by the Food and Drug Administration.

CONCLUSIONS

The selectivity and chromatographic purity of the obtained signal, as well as the standardised limits of detection and quantification, make this method an excellent tool for therapeutic monitoring of patients treated with posaconazole.

Subtherapeutic Posaconazole Exposure and Treatment Outcome in Patients With Invasive Fungal Disease

BACKGROUND

Posaconazole exposure seems to be subtherapeutic in some patients with invasive fungal disease. Due to the pharmacokinetic variability of posaconazole, therapeutic drug monitoring may help to optimize the efficacy of this antifungal drug.

METHODS

A retrospective study of patients treated with posaconazole from January 2008 to April 2014 and for whom posaconazole serum concentrations were available was conducted. Risk factors for underexposure of posaconazole were detected, and the relationship between posaconazole exposure and treatment outcome according to the European Organization for Research and Treatment of Cancer (EORTC) criteria was assessed.

RESULTS

Seventy patients met the inclusion criteria, 45 patients received posaconazole as treatment, and 25 patients received posaconazole as a prophylactic. Posaconazole serum trough concentrations were <1.25 mg/L in 44.4% of patients receiving treatment and <0.7 mg/L in 40.0% of patients receiving prophylactic posaconazole. Multiple linear regression analysis showed a significant, independent, and negative association of the posaconazole serum trough concentration with a lack of enteral nutrition (P < 0.001), vomiting (P = 0.035), the use of a proton pump inhibitor or H2-receptor antagonist (P < 0.001), a liquid diet (P = 0.002), concomitant chemotherapy (P = 0.004), and a posaconazole dose frequency of 2 times daily (P = 0.015). A higher posaconazole concentration was associated with a better treatment outcome [odds ratio = 22.22 (95% confidence interval, 3.40-145.33); P = 0.001].

CONCLUSIONS

Posaconazole exposure is insufficient in more than 40% of patients at risk of or with invasive fungal disease, and posaconazole exposure is positively correlated with a successful treatment outcome. Therapeutic drug monitoring of posaconazole can detect underexposure and can be helpful in treatment optimization.

Effectiveness of increasing the frequency of posaconazole syrup administration to achieve optimal plasma concentrations in patients with haematological malignancy

Few data are available on whether adjusting the dose of posaconazole syrup is effective in patients receiving anti-cancer chemotherapy. The aim of this prospective study was to analyse the impact of increasing the frequency of posaconazole administration on optimal plasma concentrations in adult patients with haematological malignancy. A total of 133 adult patients receiving chemotherapy for acute myeloid leukaemia or myelodysplastic syndrome who received posaconazole syrup 200 mg three times daily for fungal prophylaxis were enrolled in this study. Drug trough levels were measured by liquid chromatography-tandem mass spectrometry. In 20.2% of patients (23/114) the steady-state concentration of posaconazole was suboptimal (<500 ng/mL) on Day 8. In these patients, the frequency of posaconazole administration was increased to 200 mg four times daily. On Day 15, the median posaconazole concentration was significantly increased from 368 ng/mL [interquartile range (IQR), 247-403 ng/mL] to 548 ng/mL (IQR, 424-887 ng/mL) (P = 0.0003). The median increase in posaconazole concentration was 251 ng/mL (IQR, 93-517 ng/mL). Among the patients with initially suboptimal levels, 79% achieved the optimal level unless the steady-state level was <200 ng/mL. This study shows that increasing the administration frequency of posaconazole syrup is effective for achieving optimal levels in patients with haematological malignancy undergoing chemotherapy.

Therapeutic Drug Monitoring of Posaconazole: an Update

Posaconazole is a second-generation triazole agent with a potent and broad antifungal activity. In addition to the oral suspension, a delayed-release tablet and intravenous formulation with improved pharmacokinetic properties have been introduced recently. Due to the large interindividual and intraindividual variation in bioavailability and drug-drug interactions, therapeutic drug monitoring (TDM) is advised to ensure adequate exposure and improve clinical response for posaconazole. Here, we highlight and discuss the most recent findings on pharmacokinetics and pharmacodynamics of posaconazole in the setting of prophylaxis and treatment of fungal infections and refer to the challenges associated with TDM of posaconazole.

Pharmacokinetic considerations in treating invasive pediatric fungal infections

INTRODUCTION

Despite the increased availability of systemic antifungal agents in recent years, the management of invasive fungal disease is still associated with significant morbidity and mortality. Knowledge of a drug's pharmacokinetic behavior is critical for optimizing existing treatment strategies.

AREAS COVERED

This review examines the pharmacokinetics of the major drug classes used to treat invasive mycoses including the echinocandins, imidazoles, triazoles, nucleoside analogs, and polyenes. It examines the mechanisms behind dose-exposure profiles that differ in children as compared with adults and explores the utility of pharmacogenetic testing and therapeutic drug monitoring.

EXPERT OPINION

Lifesaving medical advances for oncologic and autoimmune conditions have resulted in a significant increase in the frequency of opportunistic fungal infections. Owing to the high rate of treatment failures observed when managing invasive fungal infections, strategies to optimize antifungal therapy are critical when caring for these complex patients. Opportunities to maximize positive outcomes include dose refinement based on age or genetic status, formulation selection, co-administration of interacting medications, and administration with regard to food. The application of therapeutic drug monitoring for dose individualization is a valuable strategy to achieve pharmacodynamic targets.

Voriconazole pharmacokinetics following HSCT: results from the BMT CTN 0101 trial

BACKGROUND

Voriconazole is a first-line agent for the prevention and treatment of a number of invasive fungal diseases. Relatively little is known about the relationship between drug exposure and the prevention of invasive fungal infections.

PATIENTS AND METHODS

A pharmacokinetic-pharmacodynamic substudy was performed as part of the BMT CTN 0101 trial, which was a randomized clinical trial comparing voriconazole with fluconazole for the prevention of invasive fungal infections in HSCT recipients. A previously described population pharmacokinetic model was used to calculate the maximum a posteriori Bayesian estimates for 187 patients. Drug exposure in each patient was quantified in terms of the average AUC and average trough concentrations. The relationship between drug exposure and the probability of breakthrough infection was investigated using logistic regression. AUC and trough concentrations in patients with and without breakthrough infection were compared.

RESULTS

Pharmacokinetic data from each patient were readily described using the maximum a posteriori Bayesian estimates. There were only five patients that had a breakthrough infection while receiving voriconazole in the first 100 days post-HSCT. For these patients, there was no statistically significant relationship between the average AUC or average trough concentration and the probability of breakthrough infection [OR (95% CI) 1.026 (0.956-1.102) and 1.108 (0.475-2.581), respectively]. P value for these estimates was 0.474 and 0.813, respectively.

CONCLUSIONS

Given the very small number of proven/probable infections, it was difficult to identify any differences in drug exposure in HSCT recipients with and without breakthrough fungal infections.

Therapeutic drug monitoring of anti-infective agents in critically ill patients

Initial adequate anti-infective therapy is associated with significantly improved clinical outcomes for patients with severe infections. However, in critically ill patients, several pathophysiological and/or iatrogenic factors may affect the pharmacokinetics of anti-infective agents leading to suboptimal drug exposure, in particular during the early phase of therapy. Therapeutic drug monitoring (TDM) may assist to overcome this problem. We discuss the available evidence on the use of TDM in critically ill patient populations for a number of anti-infective agents, including aminoglycosides, β-lactams, glycopeptides, antifungals and antivirals. Also, we present the available evidence on the practices of anti-infective TDM and describe the potential utility of TDM to improve treatment outcome in critically ill patients with severe infections. For aminoglycosides, glycopeptides and voriconazole, beneficial effects of TDM have been established on both drug effectiveness and potential side effects. However, for other drugs, therapeutic ranges need to be further defined to optimize treatment prescription in this setting.

Pharmacokinetics of Posaconazole Oral Suspension in Children Dosed According to Body Surface Area

BACKGROUND

Antifungal prophylaxis remains challenging in immunocompromised children as no clear consensus has yet been reached about which drug to be used. Posaconazole has a broad spectrum of activity, a favorable safety profile and excellent prophylactic activity in adults. However, a lack of pharmacokinetic studies in pediatric patients hampers routine implementation. This study investigates the pharmacokinetics of a newly introduced posaconazole dosing regimen based on the body surface area in pediatric hematologic patients.

METHODS

In this prospective pharmacokinetic study, 8 blood samples were taken during 1 dosing interval at steady state in children aged 13 years or younger with hematologic malignancy, who were treated prophylactically with posaconazole oral suspension at a dose of 120 mg/m 3 times daily. Posaconazole plasma concentrations were determined using high-performance liquid chromatography fluorescence detection.

RESULTS

One hundred twelve samples were taken from 14 patients with a mean age of 6.7 ± 2.8 years. A median posaconazole daily dose of 100.0 mg (77.3-100.0) 3 times daily (tid), corresponding to a median of 117.9 mg/m (112.2-120.4) tid, resulted in mean trough posaconazole plasma concentrations of 0.85 ± 0.56 mg/L. Pharmacokinetic analysis revealed a clearance of 0.8 L/(h kg) (0.5-1.4). No invasive fungal infections or adverse events were encountered during treatment.

CONCLUSIONS

Posaconazole is a promising antifungal agent to be used prophylactically in hematologic patients aged 13 years or younger. Administering posaconazole oral suspension in a dosage of 120 mg/m tid results in adequate posaconazole plasma exposure, without significant adverse events.

Posaconazole pharmacokinetics after administration of an intravenous solution, oral suspension, and delayed-release tablet to dogs

OBJECTIVE

To determine pharmacokinetics of posaconazole in dogs given an IV solution, oral suspension, and delayed-release tablet.

ANIMALS

6 healthy dogs.

PROCEDURES

Posaconazole was administered IV (3 mg/kg) and as an oral suspension (6 mg/kg) to dogs in a randomized crossover study. Blood samples were collected before (time 0) and for 48 hours after each dose. In an additional experiment, 5 of the dogs received posaconazole delayed-release tablets (mean dose, 6.9 mg/kg); blood samples were collected for 96 hours. Plasma concentrations were analyzed with high-performance liquid chromatography.

RESULTS

IV solution terminal half-life (t1/2) was 29 hours (coefficient of variation [CV], 23%). Clearance and volume of distribution were 78 mL/h/kg (CV, 59%) and 3.3 L/kg (CV, 38%), respectively. Oral suspension t1/2 was 24 hours (CV, 42%). Maximum plasma concentration (Cmax) of 0.42 μg/mL (CV, 56%) was obtained at 7.7 hours (CV, 92%). Mean bioavailability was 26% (range, 7.8% to 160%). Delayed-release tablet t1/2 was 42 hours (CV, 25%), with a Cmax of 1.8 μg/mL (CV, 44%) at 9.5 hours (CV, 85%). Mean bioavailability of tablets was 159% (range, 85% to 500%). Bioavailability of delayed-release tablets was 497% (range, 140% to 1,800%) relative to that of the oral suspension.

CONCLUSIONS AND CLINICAL RELEVANCE

Absorption of posaconazole oral suspension in dogs was variable. Absorption of the delayed-release tablets was greater than absorption of the oral suspension, with a longer t1/2 that may favor its clinical use in dogs. Administration of delayed-release tablets at a dosage of 5 mg/kg every other day can be considered for future studies.

Comparison of posaconazole serum concentrations from haematological cancer patients on posaconazole tablet and oral suspension for treatment and prevention of invasive fungal infections

Posaconazole tablet formulation (PTF) was developed to optimise bioavailability. This study compared posaconazole levels between patients on the PTF and oral suspension formulation (OSF). We also examined factors that may impact posaconazole levels. The primary and secondary objectives were analysed by comparing trough levels and attainment of target level between the formulation groups. For the 86 patients on PTF and 176 on OSF, the mean first levels was 1.32 μg ml^-1 (SD = 0.69) and 0.81 μg ml^-1 (SD = 0.59), P < 0.0001 respectively. PTF group was more likely to achieve levels ≥0.7 μg ml^-1 than OSF group (OR 7.97 [95 CI; 3.75-16.93], P < 0.0001). Levels from patients on PTF and with presence of acid suppression, GI GVHD, mucositis or diarrhoea were not statistically different from those without these factors. For PTF, no correlation was found between patient's weight (kg) and levels (R² = 0.0536, P = 0.035). The incidences of elevation in ALT/AST or Tbili were similar between the formulation groups. In conclusion, PTF should be considered the preferred formulation because it demonstrated better absorption than the OSF. Patients on PTF for prophylaxis are more likely to attain target level and may not routinely require therapeutic drug monitoring during prophylaxis.

Pharmacologic and clinical evaluation of posaconazole

Posaconazole, a broad-spectrum triazole antifungal agent, is approved for the prevention of invasive aspergillosis and candidiasis in addition to the treatment of oropharyngeal candidiasis. There is evidence of efficacy in the treatment and prevention of rarer, more difficult-to-treat fungal infections. Posaconazole oral suspension solution has shown limitations with respect to fasting state absorption, elevated gastrointestinal pH and increased motility. The newly approved delayed-release oral tablet and intravenous solution formulations provide an attractive treatment option by reducing interpatient variability and providing flexibility in critically ill patients. On the basis of clinical experience and further clinical studies, posaconazole was found to be a valuable pharmaceutical agent for the treatment of life-threatening fungal infections. This review will examine the development history of posaconazole and highlight the most recent advances.

Pharmacokinetics and safety of posaconazole delayed-release tablets for invasive fungal infections

Posaconazole is a broad-spectrum triazole antifungal agent with potent activity against various pathogenic fungi, including yeast and moulds. Clinical studies have demonstrated that this agent is efficacious as prophylaxis against invasive fungal infections in patients at high risk, and may also be useful as salvage therapy against invasive aspergillosis and mucormycosis. However, the bioavailability of posaconazole following administration by oral suspension, which was the only formulation clinically available for many years, is highly variable and negatively influenced by several factors. Because of this, many patients had subtherapeutic or undetectable posaconazole levels when the oral suspension was used. To overcome this limitation, a delayed-release tablet was developed and is now available for clinical use. Hot-melt extrusion technology is used to combine a pH-sensitive polymer with posaconazole to produce a formulation that releases the drug in the elevated pH of the intestine where absorption occurs rather than in the low-pH environment of the stomach. This results in enhanced bioavailability and increased posaconazole exposure. Studies in healthy volunteers have demonstrated significantly higher and more consistent exposures with the tablet formulation compared to the oral suspension. In addition, pharmacokinetic parameters following administration of the tablets were not significantly affected by medications that raise gastric pH or increase gastric motility, and the tablets could also be administered without regard to food. Similar results have also been found in patients at high risk for invasive fungal infections who have received posaconazole tablets. The tablet formulation also appears to be well tolerated to date, although data regarding clinical efficacy are needed.

Phase 3 pharmacokinetics and safety study of a posaconazole tablet formulation in patients at risk for invasive fungal disease

BACKGROUND

Antifungal prophylaxis with a new oral tablet formulation of posaconazole may be beneficial to patients at high risk for invasive fungal disease. A two-part (Phase 1B/3) study evaluated posaconazole tablet pharmacokinetics (PK) and safety.

METHODS

Patients with neutropenia following chemotherapy for haematological malignancy or recipients of allogeneic HSCT receiving prophylaxis or treatment for graft-versus-host disease received 300 mg posaconazole (as tablets) once daily (twice daily on day 1) for up to 28 days without regard to food intake. Weekly trough PK sampling was performed during therapy, and a subset of patients had sampling on days 1 and 8. Cmin-evaluable subjects received ≥6 days of dosing, and were compliant with specified sampling timepoints. Steady-state PK parameters, safety, clinical failure and survival to day 65 were assessed. ClinicalTrials.gov, NCT01777763; EU Clinical Trials Register, EUDRA-CT 2008-006684-36.

RESULTS

Two hundred and ten patients received 300 mg posaconazole (as tablets) once daily. Among Cmin-evaluable subjects (n = 186), steady-state mean Cmin was 1720 ng/mL (range = 210-9140). Steady-state Cmin was ≥700 ng/mL in 90% of subjects with 5% (10 of 186) <500 ng/mL and 5% (10 of 186) 500-700 ng/mL. Six (3%) patients had steady-state Cmin ≥3750 ng/mL. One patient (<1%) had an invasive fungal infection. The most common treatment-related adverse events were nausea (11%) and diarrhoea (8%). There was no increase in adverse event frequency with higher posaconazole exposure.

CONCLUSIONS

In patients at high risk for invasive fungal disease, 300 mg posaconazole (as tablets) once daily was well tolerated and demonstrated a safety profile similar to that reported for posaconazole oral suspension: most patients (99%) achieved steady-state pCavg exposures >500 ng/mL and only one patient (<1%) had a pCavg <500 ng/mL.

Clinical utility of panfungal polymerase chain reaction for the diagnosis of invasive fungal disease: a single center experience

The role of panfungal polymerase chain reaction (PCR) assays for diagnosis of invasive fungal disease (IFD) is inadequately defined. We describe the use of an internal transcribed spacer 1 (ITS-1) region-directed panfungal PCR in this context at a tertiary referral transplant center. A retrospective review of patients at Alfred Health, Melbourne, Australia (2009-2014) who had clinical samples referred for panfungal PCR testing was conducted. Baseline patient characteristics, antifungal drug history, fungal culture/histopathology, and radiology results were recorded. For bronchoalveolar lavage (BAL) fluid samples, identification of a fungus other than a Candida spp. was defined as a potential pathogen.Of 138 panfungal PCR tests (108 patients), 41 (30%) were positive for a fungal product. Ninety-seven percent (134/138) of specimens were from immunocompromised hosts. Thirteen percent (19/138) of panfungal PCR positive results were for potential pathogens and potential pathogens were detected more frequently in tissue as compared with BAL (12/13 vs. 6/26; P = .0001). No positive panfungal PCR results were obtained from CSF specimens. If histopathology examination was negative, panfungal PCR identified a potential pathogen in only 12% (11/94) of specimens. For the 20 culture negative/histopathology positive specimens, diagnosis of IFD to causative species level by panfungal PCR occurred in 35% (6/20).Sterile site specimens, in particular tissue, were more frequently panfungal PCR positive for potential pathogens than BAL. The utility of panfungal PCR appears greatest in tissue specimens, as an adjunct to histopathology to improve diagnostic sensitivity and specificity. Based on the results of this study we are now only testing tissue specimens by panfungal PCR.

Role of New Antifungal Agents in the Treatment of Invasive Fungal Infections in Transplant Recipients: Isavuconazole and New Posaconazole Formulations

Invasive fungal infections are a major cause of morbidity and mortality among solid organ transplant (SOT) and hematopoietic stem cell transplant (HSCT) recipients. Transplant patients are at risk for such invasive fungal infections. The most common invasive fungal infections are invasive candidiasis in the SOT and invasive aspergillosis in the HSCT. In this article, we will discuss the epidemiology of invasive fungal infections in the transplant recipients and susceptibility patterns of the fungi associated with these infections. Additionally, the pharmacology and clinical efficacy of the new antifungal, isavuconazole, and the new posaconazole formulations will be reviewed. Isavuconazole is a new extended-spectrum triazole that was recently approved for the treatment of invasive aspergillosis and mucormycosis. Advantages of this triazole include the availability of a water-soluble intravenous formulation, excellent bioavailability of the oral formulation, and predictable pharmacokinetics in adults. Posaconazole, a broad-spectrum triazole antifungal agent, is approved for the prevention of invasive aspergillosis and candidiasis in addition to the treatment of oropharyngeal candidiasis. Posaconazole oral suspension solution has shown some limitations in the setting of fasting state absorption, elevated gastrointestinal pH, and increased motility. The newly approved delayed-release oral tablet and intravenous solution formulations provide additional treatment options by reducing interpatient variability and providing flexibility in these set of critically ill patients. This review will detail these most recent studies.

Determination of posaconazole concentration with LC-MS/MS in adult patients with hematologic malignancy

BACKGROUND

Posaconazole has an important role in the prophylaxis of invasive fungal infections (IFIs), however oral suspension formulation is associated with variable bioavailability. The relationship between posaconazole concentrations achieved with the oral suspension and the IFI occurrence were analyzed along with demographic and clinical covariates (mucositis, diarrhea, liver enzymes, co-medications, and food intake).

METHODS

One hundred twenty-two adult patients with AML/MDS undergoing remission induction chemotherapy were enrolled. They received posaconazole as prophylaxis and 557 posaconazole measurements were performed with a validated LC-MS/MS method.

RESULTS

The median (range) posaconazole concentration (ng/ml) on days 2, 3, 7, 14, and 21 was 271 (43-493), 564 (101-1461), 713 (85-2186), 663 (85-1994), and 497 (43-1872), respectively. Thirteen patients (11%) developed proven (1/13), probable (2/13), and possible IFIs (10/13). A significant relationship existed between lower steady-state posaconazole concentrations and a higher breakthrough IFI incidence by binary logistic regression (P=0.0108). Posaconazole value of ≥ 338 ng/ml on day 3 predicted the achievement of ≥ 500 ng/ml at day 7 (sensitivity: 78.5%, specificity: 66.7%, AUC: 0.747). Food intake (P=0.0014) and proton pump inhibitor (P=0.0063) were significantly associated with higher and lower posaconazole concentrations, respectively.

CONCLUSIONS

TDM of posaconazole oral suspension formulation is recommended based on the exposure-response relationship of the present study.

Consensus guidelines for optimising antifungal drug delivery and monitoring to avoid toxicity and improve outcomes in patients with haematological malignancy, 2014

Antifungal agents may be associated with significant toxicity or drug interactions leading to sub-therapeutic antifungal drug concentrations and poorer clinical outcomes for patients with haematological malignancy. These risks may be minimised by clinical assessment, laboratory monitoring, avoidance of particular drug combinations and dose modification. Specific measures, such as the optimal timing of oral drug administration in relation to meals, use of pre-hydration and electrolyte supplementation may also be required. Therapeutic drug monitoring (TDM) of antifungal agents is warranted, especially where non-compliance, non-linear pharmacokinetics, inadequate absorption, a narrow therapeutic window, suspected drug interaction or unexpected toxicity are encountered. Recommended indications for voriconazole and posaconazole TDM in the clinical management of haematology patients are provided. With emerging knowledge regarding the impact of pharmacogenomics upon metabolism of azole agents (particularly voriconazole), potential applications of pharmacogenomic evaluation to clinical practice are proposed.

Optimizing azole antifungal therapy in the prophylaxis and treatment of fungal infections

PURPOSE OF REVIEW

Azole antifungals are widely used in the prophylaxis and treatment of fungal infections, but are associated with a range of pharmacokinetic challenges and safety issues that necessitate individualized therapy to achieve optimal clinical outcomes. Recent advances in our knowledge of azole exposure-response relationships, therapeutic drug monitoring and individualized dosing strategies are reviewed as follows.

RECENT FINDINGS

Recent studies have significantly improved the understanding of exposure-response relationships for efficacy and toxicity, increasing confidence in target exposure ranges for azole antifungal agents. Population pharmacokinetic modelling of voriconazole has led to studies demonstrating the feasibility of model-guided dose individualization strategies with the drug, which holds significant promise for optimizing therapy. The recent approval of a solid oral tablet formulation of posaconazole with improved bioavailability and once-daily dosing has significantly improved the clinical utility of this agent. Further clinical experience with the investigational azole isavuconazole is needed to determine the role of individualized therapy.

SUMMARY

The coordination of CYP2C19 pharmacogenomic testing with model-guided dose individualization holds significant promise for optimizing therapy with voriconazole. Pharmacokinetic challenges with itraconazole, voriconazole and posaconazole oral suspension continue to require therapeutic drug monitoring to individualize therapy and optimize treatment outcomes.

Posaconazole: promising but problematic in practice in pediatric patients

Posaconazole is a broad-spectrum antifungal agent used for the prevention and treatment of invasive fungal infections. It is currently only licensed for use in children greater than 12 years of age. Absorption of the oral formulation is unpredictable and affected by mucositis and concomitant medications. We reviewed studies of posaconazole use in children younger than 12 years in relation to attainment of target serum concentrations.

Fundament and Prerequisites for the Application of an Antifungal TDM Service

Therapeutic drug monitoring (TDM) involves the measurement of plasma or serum drug concentration to adapt dosages to achieve predefined target concentrations that are associated with optimal clinical response while minimizing the chance of encountering toxicity. Many papers in the field of antifungal drugs have focused on the evidence that supports the use of TDM thereby emphasizing the breakpoints or target concentrations in general literature. This review focuses on the process of TDM to inform health care workers on the fundaments and prerequisites that safeguard the good application of TDM. Knowledge on the complete process of TDM including pharmacokinetics (and relevant covariates), pharmacodynamic aspects, trials that are necessary to provide us with evidence, translation of knowledge to other populations and pathogens, and implications for the pre-analytical, analytical, and post-analytical phases (the process of TDM) are discussed in relevant detail. For each individual step, recommendations are made for the readers. We believe this will be a valuable resource and to be of added value to the many papers that focus on relations between exposure and efficacy or toxicity. It will help to achieve greater benefit of TDM.

Effect of a high-fat meal on the pharmacokinetics of 300-milligram posaconazole in a solid oral tablet formulation

Posaconazole in oral suspension must be taken multiple times a day with food (preferably a high-fat meal) to ensure adequate exposure among patients. We evaluated the effect of food on the bioavailability of a new delayed-release tablet formulation of posaconazole at the proposed clinical dose of 300 mg once daily in a randomized, open-label, single-dose, two-period crossover study with 18 healthy volunteers. When a single 300-mg dose of posaconazole in tablet form (3 tablets × 100 mg) was administered with a high-fat meal, the posaconazole area under the concentration-time curve from 0 to 72 h (AUC0-72) and maximum concentration in plasma (Cmax) increased 51% and 16%, respectively, compared to those after administration in the fasted state. The median time to Cmax (Tmax) shifted from 5 h in the fasted state to 6 h under fed conditions. No serious adverse events were reported, and no subject discontinued the study due to an adverse event. Six of the 18 subjects reported at least one clinical adverse event; all of these events were mild and short lasting. The results of this study demonstrate that a high-fat meal only modestly increases the mean posaconazole exposure (AUC), ∼1.5-fold, after administration of posaconazole tablets, in contrast to the 4-fold increase in AUC observed previously for a posaconazole oral suspension given with a high-fat meal.

Therapeutic drug monitoring for triazoles: A needs assessment review and recommendations from a Canadian perspective

Invasive fungal infections cause significant morbidity and mortality in patients with concomitant underlying immunosuppressive diseases. The recent addition of new triazoles to the antifungal armamentarium has allowed for extended-spectrum activity and flexibility of administration. Over the years, clinical use has raised concerns about the degree of drug exposure following standard approved drug dosing, questioning the need for therapeutic drug monitoring (TDM). Accordingly, the present guidelines focus on TDM of triazole antifungal agents. A review of the rationale for triazole TDM, the targeted patient populations and available laboratory methods, as well as practical recommendations based on current evidence from an extended literature review are provided in the present document.

Posaconazole prophylaxis in experimental azole-resistant invasive pulmonary aspergillosis

We investigated the efficacy of posaconazole prophylaxis in preventing invasive aspergillosis due to azole-resistant Aspergillus fumigatus isolates. Using a neutropenic murine model of pulmonary infection, posaconazole prophylaxis was evaluated using three isogenic clinical isolates, with posaconazole MICs of 0.063 mg/liter (wild type), 0.5 mg/liter (F219I mutation), and 16 mg/liter. A fourth isolate harboring TR34/L98H (MIC of 0.5 mg/liter) was also tested. Posaconazole prophylaxis was effective in A. fumigatus with posaconazole MICs of ≤0.5 mg/liter, where 100% survival was reached. However, breakthrough infection was observed in mice infected with the isolate for which the posaconazole MIC was >16 mg/liter.

Antifungal pharmacokinetics and pharmacodynamics

Successful treatment of infectious diseases requires choice of the most suitable antimicrobial agent, comprising consideration of drug pharmacokinetics (PK), including penetration into infection site, pathogen susceptibility, optimal route of drug administration, drug dose, frequency of administration, duration of therapy, and drug toxicity. Antimicrobial pharmacokinetic/pharmacodynamic (PK/PD) studies consider these variables and have been useful in drug development, optimizing dosing regimens, determining susceptibility breakpoints, and limiting toxicity of antifungal therapy. Here the concepts of antifungal PK/PD studies are reviewed, with emphasis on methodology and application. The initial sections of this review focus on principles and methodology. Then the pharmacodynamics of each major antifungal drug class (polyenes, flucytosine, azoles, and echinocandins) is discussed. Finally, the review discusses novel areas of pharmacodynamic investigation in the study and application of combination therapy.

Fourth European Conference on Infections in Leukaemia (ECIL-4): guidelines for diagnosis, prevention, and treatment of invasive fungal diseases in paediatric patients with cancer or allogeneic haemopoietic stem-cell transplantation

Invasive opportunistic fungal diseases (IFDs) are important causes of morbidity and mortality in paediatric patients with cancer and those who have had an allogeneic haemopoietic stem-cell transplantation (HSCT). Apart from differences in underlying disorders and comorbidities relative to those of adults, IFDs in infants, children, and adolescents are unique with respect to their epidemiology, the usefulness of diagnostic methods, the pharmacology and dosing of antifungal agents, and the absence of interventional phase 3 clinical trials for guidance of evidence-based decisions. To better define the state of knowledge on IFDs in paediatric patients with cancer and allogeneic HSCT and to improve IFD diagnosis, prevention, and management, the Fourth European Conference on Infections in Leukaemia (ECIL-4) in 2011 convened a group that reviewed the scientific literature on IFDs and graded the available quality of evidence according to the Infectious Diseases Society of America grading system. The final considerations and recommendations of the group are summarised in this manuscript.

Understanding variability in posaconazole exposure using an integrated population pharmacokinetic analysis

Posaconazole oral suspension is widely used for antifungal prophylaxis and treatment in immunocompromised patients, with highly variable pharmacokinetics reported in patients due to inconsistent oral absorption. This study aimed to characterize the pharmacokinetics of posaconazole in adults and investigate factors that influence posaconazole pharmacokinetics byusing a population pharmacokinetic approach. Nonlinear mixed-effects modeling was undertaken for two posaconazole studies in patients and healthy volunteers. The influences of demographic and clinical characteristics, such as mucositis, diarrhea, and drug-drug interactions, on posaconazole pharmacokinetics were investigated using a stepwise forward inclusion/backwards deletion procedure. A total of 905 posaconazole concentration measurements from 102 participants were analyzed. A one-compartment pharmacokinetic model with first-order oral absorption with lag time and first-order elimination best described posaconazole pharmacokinetics. Posaconazole relative bioavailability was 55% lower in patients who received posaconazole than in healthy volunteers. Coadministration of proton pump inhibitors (PPIs) or metoclopramide, as well as the occurrence of mucositis or diarrhea, reduced posaconazole relative bioavailability by 45%, 35%, 58%, and 45%, respectively, whereas concomitant ingestion of a nutritional supplement significantly increased bioavailability (129% relative increase). Coadministration of rifampin or phenytoin increased apparent posaconazole clearance by more than 600%, with a smaller increase observed with fosamprenavir (34%). Participant age, weight, or sex did not significantly affect posaconazole pharmacokinetics. Posaconazole absorption was reduced by a range of commonly coadministered medicines and clinical complications, such as mucositis and diarrhea. Avoidance of PPIs and metoclopramide and administration with food or a nutritional supplement are effective strategies to increase posaconazole absorption.

Phase 1b study of new posaconazole tablet for prevention of invasive fungal infections in high-risk patients with neutropenia

Posaconazole tablets, a new oral formulation of posaconazole, can be effective when given as antifungal prophylaxis to neutropenic patients at high risk for invasive fungal infection (e.g., those with acute myelogenous leukemia or myelodysplastic syndrome). Such effectiveness might be specifically important to patients with poor oral intake because of nausea, vomiting, or chemotherapy-associated mucositis. This was a prospective, global study in high-risk patients to characterize the pharmacokinetics and safety profile of posaconazole tablets and to identify the dose of posaconazole tablets that would provide exposure within a predefined range of exposures (steady-state average concentration [area under the concentration-time curve/24 h] of ≥500 ng/ml and ≤2,500 ng/ml in >90% of patients). The study evaluated two sequential dosing cohorts: 200 mg posaconazole once daily (n = 20) and 300 mg posaconazole once daily (n = 34) (both cohorts had a twice-daily loading dose on day 1) taken without regard to food intake during the neutropenic period for ≤28 days. The exposure target was reached (day 8) in 15 of 19 (79%) pharmacokinetic-evaluable patients taking 200 mg posaconazole once daily and in 31 of 32 (97%) patients taking 300 mg posaconazole once daily; 300 mg posaconazole once daily achieved the desired exposure target. Posaconazole tablets were generally well tolerated in high-risk neutropenic patients. (This study has been registered at ClinicalTrials.gov under registration no. NCT01777763.).

Posaconazole concentrations in human tissues after allogeneic stem cell transplantation

Few data have been published regarding posaconazole tissue concentrations in humans. We analyzed tissue concentrations in biopsy specimens taken at autopsy from seven patients who received posaconazole prophylaxis because of graft-versus-host disease. The results were compared to plasma concentrations collected before death. Tissue concentrations suggestive of an accumulation of posaconazole were found in the heart, lung, liver, and kidney but not in the brain.

Pharmacokinetics and pharmacodynamics of antifungals in children: clinical implications

Invasive fungal disease (IFD) remains life threatening in premature infants and immunocompromised children despite the recent development of new antifungal agents. Optimal dosing of antifungals is one of the few factors clinicians can control to improve outcomes of IFD. However, dosing in children cannot be extrapolated from adult data because IFD pathophysiology, immune response, and drug disposition differ from adults. We critically examined the literature on pharmacokinetics (PK) and pharmacodynamics (PD) of antifungal agents and highlight recent developments in treating pediatric IFD. To match adult exposure in pediatric patients, dosing adjustment is necessary for almost all antifungals. In young infants, the maturation of renal and metabolic functions occurs rapidly and can significantly influence drug exposure. Fluconazole clearance doubles from birth to 28 days of life and, beyond the neonatal period, agents such as fluconazole, voriconazole, and micafungin require higher dosing than in adults because of faster clearance in children. As a result, dosing recommendations are specific to bracketed ranges of age. PD principles of antifungals mostly rely on in vitro and in vivo models but very few PD studies specifically address IFD in children. The exposure-response relationship may differ in younger children compared with adults, especially in infants with invasive candidiasis who are at higher risk of disseminated disease and meningoencephalitis, and by extension severe neurodevelopmental impairment. Micafungin is the only antifungal agent for which a specific target of exposure was proposed based on a neonatal hematogenous Candida meningoencephalitis animal model. In this review, we found that pediatric data on drug disposition of newer triazoles and echinocandins are lacking, dosing of older antifungals such as fluconazole and amphotericin B products still need optimization in young infants, and that target PK/PD indices need to be clinically validated for almost all antifungals in children. A better understanding of age-specific PK and PD of new antifungals in infants and children will help improve clinical outcomes of IFD by informing dosing and identifying future research areas.

Phase 1B study of the pharmacokinetics and safety of posaconazole intravenous solution in patients at risk for invasive fungal disease

This was a phase 1B, dose-ranging, multicenter, pharmacokinetics, and safety study of cyclodextrin-based posaconazole intravenous (i.v.) solution administered through a central line to subjects at high risk for invasive fungal disease (part 1 of a 2-part study [phase 1B/3]). Initially, the safety and tolerability of single-dose posaconazole i.v. 200 mg (n = 10) were compared with those of a placebo (n = 11). Subsequently, 2 doses were evaluated, posaconazole i.v. 200 mg once daily (q.d.) (n = 21) and 300 mg q.d. (n = 24). The subjects received twice-daily (b.i.d.) posaconazole i.v. on day 1, followed by 13 days of posaconazole i.v. q.d., then 14 days of posaconazole oral suspension 400 mg b.i.d. The steady-state (day 14) exposure target (average concentration [areas under concentration-time curve {AUCs}/24 h, average concentrations at steady state {Cavgs}], of ≥ 500 to ≤ 2,500 ng/ml in ≥ 90% of the subjects) was achieved by 94% of the subjects for 200 mg posaconazole q.d. and by 95% of subjects for 300 mg posaconazole q.d. The desired exposure target (mean steady-state Cavg, ∼ 1,200 ng/ml) was 1,180 ng/ml in the 200-mg dosing cohort and was exceeded in the 300-mg dosing cohort (1,430 ng/ml). Posaconazole i.v. was well tolerated. Posaconazole i.v. 300 mg q.d. was selected for the phase 3 study segment. (This study has been registered at ClinicalTrials.gov under registration no. NCT01075984.).

Breakpoints for antifungal agents: an update from EUCAST focussing on echinocandins against Candida spp. and triazoles against Aspergillus spp

Candida and Aspergillus infections have emerged as significant pathogens in recent decades. During this same time, broad spectrum triazole and echinocandin antifungal agents have been developed and increasingly used. One consequence of widespread use is leading to the emergence of mutants with acquired resistance mutations. Therefore, accurate susceptibility testing and appropriate clinical breakpoints for the interpretation of susceptibility results have become increasingly important. Here we review the underlying methodology by which breakpoints have been selected by EUCAST (European Committee on Antimicrobial Susceptibility Testing). Five parameters are evaluated: dosing regimens used; EUCAST MIC distributions from multiple laboratories, species and compound specific epidemiological cut off values (upper MIC limits of wild type isolates or ECOFFs), pharmacokinetic/pharmacodynamic relationships and targets associated with outcome and finally clinical data by species and MIC when available. The general principles are reviewed followed by a detailed review of the individual aspects for Candida species and the three echinocandins and for Aspergillus and the three mould-active azoles. This review provides an update of the subcommittee on antifungal susceptibility testing (AFST) of the EUCAST methodology and summarises the current EUCAST breakpoints for Candida and Aspergillus. Recommendations about applicability of antifungal susceptibility testing in the routine setting are also included.

Therapeutic drug monitoring (TDM) of antifungal agents: guidelines from the British Society for Medical Mycology

The burden of human disease related to medically important fungal pathogens is substantial. An improved understanding of antifungal pharmacology and antifungal pharmacokinetics-pharmacodynamics has resulted in therapeutic drug monitoring (TDM) becoming a valuable adjunct to the routine administration of some antifungal agents. TDM may increase the probability of a successful outcome, prevent drug-related toxicity and potentially prevent the emergence of antifungal drug resistance. Much of the evidence that supports TDM is circumstantial. This document reviews the available literature and provides a series of recommendations for TDM of antifungal agents.