Therapeutic drug monitoring in the treatment of invasive aspergillosis with voriconazole in cancer patients--an evidence-based approach

Therapeutic drug monitoring of antifungal therapies: do we really need it and what are the best practices?

INTRODUCTION

Despite advancements, invasive fungal infections (IFI) still carry high mortality rates, often exceeding 30%. The challenges in diagnosis, coupled with limited effective antifungal options, make managing IFIs complex. Antifungal drugs are essential for IFI management, but their efficacy can be diminished by drug-drug interactions and pharmacokinetic variability. Therapeutic Drug Monitoring (TDM), especially in the context of triazole use, has emerged as a valuable strategy to optimize antifungal therapy.

AREAS COVERED

This review provides current evidence regarding the potential benefits of TDM in IFI management. It discusses how TDM can enhance treatment response, safety, and address altered pharmacokinetics in specific patient populations.

EXPERT OPINION

TDM plays a crucial role in achieving optimal therapeutic outcomes in IFI management, particularly for certain antifungal agents. Preclinical studies consistently show a link between therapeutic drug levels and antifungal efficacy. However, clinical research in mycology faces challenges due to patient heterogeneity and the diversity of fungal infections. TDM's potential advantages in guiding Echinocandin therapy for critically ill patients warrant further investigation. Additionally, for drugs like Posaconazole, assessing whether serum levels or alternative markers like saliva offer the best measure of efficacy is an intriguing question.

Utility of triazole antifungal therapeutic drug monitoring: Insights from the Society of Infectious Diseases Pharmacists: Endorsed by the Mycoses Study Group Education and Research Consortium

Triazole antifungals (i.e., fluconazole, itraconazole, voriconazole, posaconazole, and isavuconazole) are commonly used in clinical practice to prevent or treat invasive fungal infections. Most triazole antifungals require therapeutic drug monitoring (TDM) due to highly variable pharmacokinetics, known drug interactions, and established relationships between exposure and response. On behalf of the Society of Infectious Diseases Pharmacists (SIDP), this insight describes the pharmacokinetic principles and pharmacodynamic targets of commonly used triazole antifungals and provides the rationale for utility of TDM within each agent.

The impact of gene polymorphism and hepatic insufficiency on voriconazole dose adjustment in invasive fungal infection individuals

Voriconazole (VRZ) is a broad-spectrum antifungal medication widely used to treat invasive fungal infections (IFI). The administration dosage and blood concentration of VRZ are influenced by various factors, posing challenges for standardization and individualization of dose adjustments. On the one hand, VRZ is primarily metabolized by the liver, predominantly mediated by the cytochrome P450 (CYP) 2C19 enzyme. The genetic polymorphism of CYP2C19 significantly impacts the blood concentration of VRZ, particularly the trough concentration (Ctrough), thereby influencing the drug's efficacy and potentially causing adverse drug reactions (ADRs). Recent research has demonstrated that pharmacogenomics-based VRZ dose adjustments offer more accurate and individualized treatment strategies for individuals with hepatic insufficiency, with the possibility to enhance therapeutic outcomes and reduce ADRs. On the other hand, the security, pharmacokinetics, and dosing of VRZ in individuals with hepatic insufficiency remain unclear, making it challenging to attain optimal Ctrough in individuals with both hepatic insufficiency and IFI, resulting in suboptimal drug efficacy and severe ADRs. Therefore, when using VRZ to treat IFI, drug dosage adjustment based on individuals' genotypes and hepatic function is necessary. This review summarizes the research progress on the impact of genetic polymorphisms and hepatic insufficiency on VRZ dosage in IFI individuals, compares current international guidelines, elucidates the current application status of VRZ in individuals with hepatic insufficiency, and discusses the influence of CYP2C19, CYP3A4, CYP2C9, and ABCB1 genetic polymorphisms on VRZ dose adjustments and Ctrough at the pharmacogenomic level. Additionally, a comprehensive summary and analysis of existing studies' recommendations on VRZ dose adjustments based on CYP2C19 genetic polymorphisms and hepatic insufficiency are provided, offering a more comprehensive reference for dose selection and adjustments of VRZ in this patient population.

Primary prophylaxis of invasive fungal diseases in patients with haematological malignancies: 2022 update of the recommendations of the Infectious Diseases Working Party (AGIHO) of the German Society for Haematology and Medical Oncology (DGHO)

Patients with haematological malignancies (HM) are at high risk of developing invasive fungal disease (IFD) with high morbidity and attributable mortality. We reviewed data published until September 2021 to update the 2017 antifungal prophylaxis recommendations of the German Society of Haematology and Medical Oncology (DGHO). The strong recommendation to administer antifungal prophylaxis in patients with HM with long-lasting neutropenia, i.e. <500 cells/μL for >7 days remains unchanged. Posaconazole remains the drug of choice for mould-active prophylaxis in these patients. Novel treatment options in HM, such as CAR-T-cell treatment or novel targeted therapies for acute myeloid leukaemia (AML) were considered, however, data are insufficient to give general recommendations for routine antifungal prophylaxis in these patients. Major changes regarding specific recommendations compared to the 2017 edition are the now moderate instead of mild support for the recommendations of isavuconazole and voriconazole. Furthermore, published evidence on micafungin allows recommending it at moderate strength for its use in HM. For the first time we included recommendations for non-pharmaceutical measures regarding IFD, comprising the use of high-efficiency particulate air (HEPA) filters, smoking, measures during construction work and neutropenic diets. We reviewed the impact of antifungal prophylaxis with triazoles on drug-drug interactions with novel targeted therapies that are metabolized via cytochrome p450 where triazoles inhibit CYP3A4/5. The working group recommends reducing the dose of venetoclax when used concomitantly with strong CYP3A4 inhibiting antifungals. Furthermore, we reviewed data on the prophylactic use of novel antifungal agents. Currently there is no evidence to support their use in a prophylactic setting in clinical practice.

Factors Influencing Blood Concentration of Voriconazole and Therapeutic Drug Monitoring in Patients with Child–Pugh Class C Cirrhosis

What Is Known and Objective. CYP2C19 is an important influencing factor for voriconazole trough plasma concentration (Cmin); however, it is not verified in Child–Pugh C (CP-C) cirrhosis patients, and no voriconazole dosage regimen is recommended for these patients in the package insert. This retrospective study identified CYP2C19 and other factors influencing voriconazole Cmin for CP-C cirrhosis, and obtained an appropriate method of application of voriconazole for them. Methods. A total of 66 patients with CP-C cirrhosis who accepted voriconazole therapy were involved. The voriconazole Cmin, clinical characteristics, CYP2C19 genotype, and adverse effects (AEs) were recorded and analyzed. Results. Unlike other research studies, voriconazole Cmin was not different among normal metabolizers (NMs), intermediate metabolizers (IMs), and poor metabolizers (PMs) of the CYP2C19 enzyme in CP-C cirrhosis ( $P$  > 0.05). The maintenance dose regimen for voriconazole was the only independent influencing factor for Cmin ( $P$  = 0.045; OR = 3.753; 95% CI, 1.029–13.694). At about 1/3 of the recommended maintenance dose, only 16.7% (8/48) had Cmin >5.5 μg/mL, 4.5% (3/48) had Cmin <1 μg/mL, and only one AE happened. There were four voriconazole-related AEs that happened in this study, and three AEs occurred (3/4, 75%) when the maintenance dose was not adjusted with therapeutic drug monitoring (TDM). What Is New and Conclusion. Voriconazole Cmin did not significantly vary according to CYP2C19 enzyme metabolization status (being an NM, IM, or PM) in CP-C cirrhosis. Reducing the maintenance dose of voriconazole to approximately 1/3 the standard maintenance dose and administering in combination with TDM in patients with CP-C cirrhosis are recommended.

Pharmacogenetic Analysis of Voriconazole Treatment in Children

Voriconazole is among the first-line antifungal drugs to treat invasive fungal infections in children and known for its pronounced inter- and intraindividual pharmacokinetic variability. Polymorphisms in genes involved in the metabolism and transport of voriconazole are thought to influence serum concentrations and eventually the therapeutic outcome. To investigate the impact of these genetic variants and other covariates on voriconazole trough concentrations, we performed a retrospective data analysis, where we used medication data from 36 children suffering from invasive fungal infections treated with voriconazole. Data were extracted from clinical information systems with the new infrastructure SwissPK^cdw, and linear mixed effects modelling was performed using R. Samples from 23 children were available for DNA extraction, from which 12 selected polymorphism were genotyped by real-time PCR. 192 (49.1%) of 391 trough serum concentrations measured were outside the recommended range. Voriconazole trough concentrations were influenced by polymorphisms within the metabolizing enzymes CYP2C19 and CYP3A4, and within the drug transporters ABCC2 and ABCG2, as well as by the co-medications ciprofloxacin, levetiracetam, and propranolol. In order to prescribe an optimal drug dosage, pre-emptive pharmacogenetic testing and careful consideration of co-medications in addition to therapeutic drug monitoring might improve voriconazole treatment outcome of children with invasive fungal infections.

A retrospective multi-center study of treatment, outcome, and prognostic factors in 34 dogs with disseminated aspergillosis in Australia

BACKGROUND

Disseminated aspergillosis (DA) in dogs has a guarded prognosis and there is a lack of a gold standard treatment protocol.

OBJECTIVE

To retrospectively assess survival times and factors influencing survival times.

ANIMALS

Dogs diagnosed with DA from January 2007 to June 2017.

METHODS

Disseminated aspergillosis case data were retrieved from 13 Australian veterinary referral centers, with a diagnosis confirmed with culture or PCR. Factors influencing survival time after diagnosis were quantified using a Cox proportional hazards regression model.

RESULTS

Thirty-four dogs met the study inclusion criteria. Twenty-two dogs were treated with antifungal treatment and 12 dogs received no antifungal treatment. Accounting for censoring of dogs that were either still alive on the date of data collection or were loss to follow-up, dogs treated with itraconazole alone (n = 8) had a median survival time (MST) of 63 (95% CI: 20-272) days compared to 830 (95% CI: 267-1259) days for the n = 14 dogs that received multimodal antifungal therapy ( χ 2 test statistic 8.6; df = 1; P < .01). The daily hazard of death (DHOD) for dogs with abnormally high serum creatinine concentration at the time of diagnosis was 7.4 (95% CI: 1.9-29) times that of dogs with serum creatinine within the reference interval.

CONCLUSION AND CLINICAL IMPORTANCE

Serum creatinine concentration at the time of diagnosis is a useful prognostic indicator for survival after a diagnosis of DA. The MST for dogs treated with multimodal antifungal therapy is longer than itraconazole alone and warrant further investigation (P < .01).

How different is invasive fusariosis in pediatric patients than in adults? A systematic review

PURPOSE OF REVIEW

To investigate the peculiarities of invasive fusariosis (IF) in pediatric patients.

METHODS

We conducted a systematic literature review to identify human cases of locally invasive and systemic fusariosis documented in children (up to 18 years) published between 1973 (first case report) and 2021.

RECENT FINDINGS

One hundred and six cases were retrieved, and hematologic malignancy was reported in 64% (68/106) of the cases. The most frequent anatomic sites involved were skin 66% (70/106), blood 47% (50/106), and lungs 35% (37/106), bone and joint (8%, 09/106), and eye/central nervous system involvement (8%, 9/106). Fusarium solani, followed by Fusarium oxysporum, were the most commonly reported species. In disseminated fusariosis, relapsed or refractory baseline disease (P < 0.001, OR=10.555, CI 95% 3.552-31.365) was associated with poor outcome, whereas voriconazole-based therapy was associated with better prognosis (P  = 0.04, OR = 0.273, CI 95% 0.076-0.978).

SUMMARY

Hematologic malignancies and solid tumors requiring intensive immunosuppression are the main conditions related to IF in children where other organs than skin, blood, and lungs were frequently involved. Voriconazole therapy appears to be also effective in children with IF, despite the wide pharmacokinetic variability of this triazole in pediatric patients.

Voriconazole Use in Children: Therapeutic Drug Monitoring and Control of Inflammation as Key Points for Optimal Treatment

Voriconazole plasma concentrations (PC) are highly variable, particularly in children. Dose recommendations in 2-12-year-old patients changed in 2012. Little data on therapeutic drug monitoring (TDM) after these new recommendations are available. We aimed to evaluate voriconazole monitoring in children with invasive fungal infection (IFI) after implementation of new dosages and its relationship with safety and effectiveness. A prospective, observational study, including children aged 2-12 years, was conducted. TDM was performed weekly and doses were changed according to an in-house protocol. Effectiveness, adverse events, and factors influencing PC were analysed. A total of 229 PC from 28 IFI episodes were obtained. New dosing led to a higher rate of adequate PC compared to previous studies; still, 35.8% were outside the therapeutic range. In patients aged < 8 years, doses to achieve therapeutic levels were higher than recommended. Severe hypoalbuminemia and markedly elevated C-reactive protein were related to inadequate PC. Therapeutic PC were associated with drug effectiveness and safety. Higher doses in younger patients and a dose adjustment protocol based on TDM should be considered. Voriconazole PC variability has decreased with current updated recommendations, but it remains high and is influenced by inflammatory status. Additional efforts to control inflammation in children with IFI should be encouraged.

Using Child-Pugh Class to Optimize Voriconazole Dosage Regimens and Improve Safety in Patients with Liver Cirrhosis: Insights from a Population Pharmacokinetic Model-based Analysis

BACKGROUND

Cirrhotic patients are at a high risk of fungal infections. Voriconazole is widely used as prophylaxis and in the treatment of invasive fungal disease. However, the safety, pharmacokinetics, and optimal regimens of voriconazole are currently not well defined in cirrhotic patients.

DESIGN

Retrospective pharmacokinetics study.

SETTING

Two large, academic, tertiary-care medical center.

PATIENTS

Two hundred nineteen plasma trough concentrations (C_min ) from 120 cirrhotic patients and 83 plasma concentrations from 11 non-cirrhotic patients were included.

METHODS

Data pertaining to voriconazole were collected retrospectively. A population pharmacokinetics analysis was performed and model-based simulation was used to optimize voriconazole dosage regimens.

RESULTS

Voriconazole-related adverse events (AEs) developed in 29 cirrhotic patients, and the threshold C_min for AE was 5.12 mg/L. A two-compartment model with first-order elimination adequately described the data. The Child-Pugh class and body weight were the significant covariates in the final model. Voriconazole clearance in non-cirrhotic, Child-Pugh class A and B cirrhotic (CP-A/B) and Child-Pugh class C cirrhotic (CP-C) patients was 7.59, 1.86, and 0.93 L/hour, respectively. The central distribution volume and peripheral distribution volume was 100.8 and 55.2 L, respectively. The oral bioavailability was 91.6%. Model-based simulations showed that a loading dose regimen of 200 mg/12 hours intravenously or orally led to 65.0-75.7% of voriconazole C_min in therapeutic range on day 1, and the appropriate maintenance dosage regimens were 75 mg/12 hours and 150 mg/24 hours intravenously or orally for CP-A/B patients, and 50 mg/12 hours and 100 mg/24 hours intravenously or orally for CP-C patients. The predicted probability of achieving the therapeutic target concentration for optimized regimens at steady-state was 66.8-72.3% for CP-A/B patients and 70.3-74.0% for CP-C patients.

CONCLUSIONS

These results recommended that the halved loading dose regimens should be used, and voriconazole maintenance doses in cirrhotic patients should be reduced to one-fourth for CP-C patients and to one-third for CP-A/B patients compared to that for patients with normal liver function.

Determination of voriconazole in human plasma by liquid chromatography-tandem mass spectrometry and its application in therapeutic drug monitoring in Chinese patients

OBJECTIVE

To develop a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantification of voriconazole in human plasma, and to evaluate its application in clinical therapeutic drug monitoring.

METHOD

Plasma samples were obtained from Chinese patients receiving voriconazole, precipitated with methanol (using fluconazole as an internal standard), and then subjected to LC-MS/MS using an SB C18 column with a methanol and water mobile phase at a flow rate of 0.4 mL/minute. Quantification was performed by multiple-reaction monitoring using the precursor and product ion pair m/z 350-280.9 for voriconazole and m/z 307-219.9 for fluconazole.

RESULTS

The calibration curve was linear over a range of 0.1-10.0 µg/mL (R2 = 0.9995). The inter-day and intra-day relative standard deviations were <7.68% and <8.97%, respectively. Extraction recovery, matrix effect, and stability were also validated. Sixty-eight plasma samples from 42 patients were analyzed, and the voriconazole concentrations in 25 samples (36.8%) were outside the optimal range of 1.5-4.5 µg/mL.

CONCLUSIONS

We developed a simple and accurate method of drug monitoring, which could improve the efficacy and prevent adverse reactions of voriconazole.

A consensus document for the clinical management of invasive fungal diseases in pediatric patients with hematologic cancer and/or undergoing hematopoietic stem cell transplantation in Brazilian medical centers

In the present paper we summarize the suggestions of a multidisciplinary group including experts in pediatric oncology and infectious diseases who reviewed the medical literature to elaborate a consensus document (CD) for the diagnosis and clinical management of invasive fungal diseases (IFDs) in children with hematologic cancer and those who underwent hematopoietic stem-cell transplantation. All major multicenter studies designed to characterize the epidemiology of IFDs in children with cancer, as well as all randomized clinical trials addressing empirical and targeted antifungal therapy were reviewed. In the absence of randomized clinical trials, the best evidence available to support the recommendations were selected. Algorithms for early diagnosis and best clinical management of IFDs are also presented. This document summarizes practical recommendations that will certainly help pediatricians to best treat their patients suffering of invasive fungal diseases.

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.

Determination of voriconazole and co-administered drugs in plasma of pediatric cancer patients using UPLC-MS/MS: A key step towards personalized therapeutics

Untreated invasive aspergillosis results in high mortality rate in pediatric cancer patients. Voriconazole (VORI), the first line of treatment, requires strict dose monitoring because of its narrow therapeutic index and individual variation in plasma concentration levels. Commonly co-administered drugs; either Esomeprazole (ESO) or Ondansetron (OND) have reported drug-drug interaction with VORI that should adversely alter therapeutic outcomes of the latter. Although VORI, ESO and OND are co-administered to pediatric cancer patients, the combined effect of ESO and OND on the plasma concentration levels of VORI has not been fully explored. In this study, an accurate, reliable and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay was developed and validated for simultaneous determination of VORI, ESO, and OND in ultra-low sample volumes (25 μL) of plasma of pediatric cancer patients. Based on the physicochemical properties of the studied drugs and internal standard, liquid-liquid extraction was successfully adopted with methyl t-butyl ether. Consistent and reproducible recovery of the three drugs and the internal standard were calculated using plasma and matrix matched samples (RE% > 72.97%, RSD < 8.29%). Chromatographic separation was carried out using UPLC with C18 column and a mobile phase of acetonitrile:water:methanol (70:25:5 V/V/V) at 0.3 mL/min. Mass spectrometric determination at positive electrospray ionization in the MRM mode was employed. The analysis was achieved within 4 min over a linear concentration range of 1.00-200.00 ng/mL for the three drugs. The assay validity was assessed as per the Food and Drug Administration guidelines for bioanalytical method validation, and satisfactory results were obtained. The accuracy and precision were within the acceptable limits for the three drugs in both quality control and incurred plasma samples. Matrix effect and process efficiency were investigated in neat solvent, post-extraction matrix, and plasma. Correlation of the plasma concentration levels of the three drugs revealed differences from the reported drug-drug interactions. This confirmed the need for simultaneous determination of VORI and co-administered drugs in order to achieve optimal therapeutic outcomes. To achieve this, analysis results of this study, genetic polymorphisms in CYP2C19 and clinical data will be used to establish one model incorporating all possible factors that might lead to variation in therapeutic outcomes.

Pharmacodynamic studies of voriconazole: informing the clinical management of invasive fungal infections

INTRODUCTION

Voriconazole is a broad-spectrum antifungal agent commonly used to treat invasive fungal infections (IFI), including aspergillosis, candidiasis, Scedosporium infection, and Fusarium infection. IFI often occur in immunocompromised patients, leading to increased morbidity and mortality.

AREAS COVERED

The objective of this review is to summarize the pharmacodynamic properties of voriconazole and to provide considerations for potential optimal dosing strategies. Studies have demonstrated superior clinical response when an AUC/MIC >25 or Cmin/MIC >1 is attained in adult patients, correlating to a trough concentration range as narrow as 2-4.5 mg/L; however, these targets are poorly established in the pediatric population. Topics in this discussion include voriconazole use in multiple age groups, predisposing patient factors for IFI, and considerations for clinicians managing IFI. Expert commentary: The relationship between voriconazole dosing and exposure is not well defined due to the large inter- and intra-subject variability. Development of comprehensive decision support tools for individualizing dosing, particularly in children who require higher dosing, will help to increase the probability of achieving therapeutic efficacy and decrease sub-therapeutic dosing and adverse events.

New pharmacological opportunities for the treatment of invasive mould diseases

Recently, several randomized studies have been published that will shape treatment decisions in the prevention and management of invasive mould infections. Liposomal amphotericin B is an option for empirical or targeted treatment of invasive aspergillosis or mucormycosis, but for prophylaxis therapy, the triazole class now predominates. The triazole voriconazole is currently regarded as a drug of choice for the treatment of proven or probable invasive aspergillosis, and has shown significantly higher response rates than amphotericin B deoxycholate in this setting, with fewer severe drug-related adverse events. Isavuconazole, the newest triazole agent, offers the advantages of once-daily dosing, a wider spectrum of antifungal activity than voriconazole, predictable pharmacokinetics and fewer CYP enzyme-mediated drug interactions. A recent large randomized clinical trial showed mortality to be similar under isavuconazole or voriconazole in patients with invasive mould disease, with fewer drug-related adverse events in isavuconazole-treated patients. Another study has indicated that isavuconazole is also effective in mucormycosis infections but patient numbers were small and confirmation is awaited. Experimental studies combining different drug classes with antimould activity have been promising, but the clinical database is limited. A large randomized trial of combination therapy compared voriconazole plus the echinocandin anidulafungin versus voriconazole monotherapy in patients with invasive aspergillosis. Results showed the overall response rate to be similar, but combination therapy improved survival for the subpopulation of patients in whom the diagnosis was confirmed by serum and/or bronchoalveolar lavage fluid galactomannan positivity. This active field of research is likely to continue evolving rapidly in the coming years.

Combination Antifungal Therapy: A Review of Current Data

The incidence of invasive fungal infections has been on the rise, particularly in transplant recipients and in patients with hematological malignancies and other forms of immunosuppression. There is a mismatch between the rate of antifungal resistance and the development of new antifungal agents. Based on this, the idea of combining antifungals in the treatment of invasive fungal infections appears tempting for many clinicians, particularly after many in vitro studies showed synergism between many antifungal agents. Several randomized controlled trials have been published regarding the efficacy and safety of combination of antifungals, but the high cost, the limited number of cases and the multitude of confounding factors lead in some instances to weak and sometimes contradictory results. The lack of consensus in many clinical scenarios raises the importance of the need for more studies about combination antifungal therapies and should incite infectious disease societies to develop specific recommendations for the clinicians to follow while approaching patients with invasive fungal infections.

New facets of antifungal therapy

Invasive fungal infections remain a major cause of morbidity and mortality in immunocompromised patients, and such infections are a substantial burden to healthcare systems around the world. However, the clinically available armamentarium for invasive fungal diseases is limited to 3 main classes (i.e., polyenes, triazoles, and echinocandins), and each has defined limitations related to spectrum of activity, development of resistance, and toxicity. Further, current antifungal therapies are hampered by limited clinical efficacy, high rates of toxicity, and significant variability in pharmacokinetic properties. New antifungal agents, new formulations, and novel combination regimens may improve the care of patients in the future by providing improved strategies to combat challenges associated with currently available antifungal agents. Likewise, therapeutic drug monitoring may be helpful, but its present use remains controversial due to the lack of available data. This article discusses new facets of antifungal therapy with a focus on new antifungal formulations and the synergistic effects between drugs used in combination therapy.

Experiment design for nonparametric models based on minimizing Bayes Risk: application to voriconazole¹

An experimental design approach is presented for individualized therapy in the special case where the prior information is specified by a nonparametric (NP) population model. Here, a NP model refers to a discrete probability model characterized by a finite set of support points and their associated weights. An important question arises as to how to best design experiments for this type of model. Many experimental design methods are based on Fisher information or other approaches originally developed for parametric models. While such approaches have been used with some success across various applications, it is interesting to note that they largely fail to address the fundamentally discrete nature of the NP model. Specifically, the problem of identifying an individual from a NP prior is more naturally treated as a problem of classification, i.e., to find a support point that best matches the patient's behavior. This paper studies the discrete nature of the NP experiment design problem from a classification point of view. Several new insights are provided including the use of Bayes Risk as an information measure, and new alternative methods for experiment design. One particular method, denoted as MMopt (multiple-model optimal), will be examined in detail and shown to require minimal computation while having distinct advantages compared to existing approaches. Several simulated examples, including a case study involving oral voriconazole in children, are given to demonstrate the usefulness of MMopt in pharmacokinetics applications.

Different effects of lansoprazole and rabeprazole on the plasma voriconazole trough levels in allogeneic hematopoietic cell transplant recipients

Voriconazole (VRC) is widely used as prophylaxis and in the treatment of invasive fungal disease (IFD) after allogeneic hematopoietic cell transplantation (HCT). We retrospectively examined the results of VRC therapeutic drug monitoring (TDM) in allogeneic HCT recipients. A total of 474 samples were obtained from 59 adult patients who received VRC during the first 100 days following HCT between 2009 and 2014 in our institute. Seventeen patients received VRC for prophylaxis of IFD, and 42 received VRC for the empirical or preemptive therapy for IFD. A total of 299 samples (63 %) were obtained during the administration of the intravenous form of VRC. The median VRC daily dose based on the actual body weight was 6.68 mg/kg/day (range, 1.92-10.41 mg/kg/day). The median VRC trough level was 0.99 mg/l (range, <0.09-5.45 mg/l). The multivariate analysis using a logistic regression model demonstrated significantly higher VRC trough levels (≥1.0 mg/l) in males (P < 0.001), empirical or preemptive therapy (P = 0.002), VRC daily dose based on the actual body weight ≥7 mg/kg/day (P < 0.001), and concomitant use of lansoprazole as compared to rabeprazole (P < 0.001). The concomitant use of calcineurin inhibitors and corticosteroids had no effects on VRC trough levels in multivariate analysis. These data suggest that lansoprazole and rabeprazole have different effects on the plasma VRC trough levels in the allogeneic HCT recipients.

Dose optimization of voriconazole/anidulafungin combination against Aspergillus fumigatus using an in vitro pharmacokinetic/pharmacodynamic model and response surface analysis: clinical implications for azole-resistant aspergillosis

BACKGROUND

Combination therapy of voriconazole with an echinocandin is often employed in order to increase the efficacy of voriconazole monotherapy.

METHODS

Four clinical Aspergillus fumigatus isolates with different in vitro susceptibilities to voriconazole (MIC 0.125-2 mg/L) and anidulafungin (MEC 0.008-0.016 mg/L) were tested in an in vitro pharmacokinetic/pharmacodynamic model simulating human serum concentrations of standard dosages of voriconazole and anidulafungin. Fungal growth was assessed using galactomannan production and quantitative PCR. Drug concentrations were determined with bioassays. Pharmacodynamic interactions were assessed using Bliss independence analysis (BI) and Loewe additivity-based canonical mixture response-surface non-linear regression analysis (LA). Probability of target attainment (PTA) was estimated with Monte Carlo analysis for different doses of anidulafungin (25, 50 and 100 mg) and azole resistance rates (5%-25%).

RESULTS

Synergy [BI 51% (8%-80%), LA 0.63 (0.38-0.79)] was found at low anidulafungin (fC_max/MEC <10) and voriconazole (fAUC/MIC <10) exposures, whereas antagonism [BI 12% (5%-18%, LA 1.12 (1.04-4.6)] was found at higher drug exposures. The largest increase in PTA was found with 25 mg of anidulafungin and voriconazole MIC distributions with high (>10%) resistance rates. PTAs for isolates with voriconazole MICs of 1, 2 and 4 mg/L was 78%, 12% and 0% with voriconazole monotherapy and 96%-100%, 68%-82% and 9%-20% with combination therapy, respectively. Optimal activity was associated with a voriconazole tC_min/MIC ratio of 1.5 for monotherapy and 0.75 for combination therapy.

CONCLUSIONS

The present study indicated that the combination of voriconazole with low-dose anidulafungin may increase the efficacy and reduce the cost and potential toxicity of antifungal therapy, particularly against azole-resistant A. fumigatus isolates and in patients with subtherapeutic serum levels. This hypothesis warrants further in vivo verification.

Effect of cytochrome P450 2C19 polymorphisms on the clinical outcomes of voriconazole: a systematic review and meta-analysis

BACKGROUND

Genetic polymorphisms of cytochrome P450 enzymes, especially CYP2C19, could influence voriconazole pharmacokinetics. The association between CYP2C19 polymorphisms and voriconazole clinical outcomes is not well established. The aim of this meta-analysis was to evaluate the effect of CYP2C19 polymorphisms on clinical outcomes in patients treated with voriconazole.

METHODS

PubMed, EMBASE, CENTRAL, ClinicalTrials.gov, and three Chinese databases were searched from their inception to January 2016 to identify eligible trials that reported voriconazole exposure and clinical outcomes of voriconazole according to CYP2C19 polymorphisms. Two reviewers independently reviewed the citations, extracted the data, and assessed the quality of the trials. The meta-analysis was performed using RevMan5.3.

RESULTS

A total of ten studies involving 598 patients were included. Compared with patients with extensive metabolizer (EM) phenotype, patients with poor metabolizer (PM) phenotype had significantly higher trough concentrations (MD, 1.22 mg/L; 95 % confidence interval (CI), 0.72-1.71; P < 0.0001). PM phenotype was also associated with a higher treatment success rate compared with EM phenotype (risk ratio (RR), 1.31; 95 % CI, 1.04-1.67; P = 0.02). However, there was no significant association between CYP2C19 polymorphisms and daily maintenance dose, overall adverse events, hepatotoxicity, and neurotoxicity.

CONCLUSIONS

Patients with CYP2C19 PM phenotype were associated with increased treatment success rate and trough concentrations as compared with those with EM phenotype. There was no significant association between CYP2C19 polymorphisms and either daily maintenance dose or adverse outcomes of voriconazole. However, large-scale, high-quality trials are still needed to confirm these findings.

Adverse Drug Reactions in Patients Receiving Systemic Antifungal Therapy at a High-Complexity Hospital

The aim of the present study was to determine the frequency of adverse drug reactions (ADRs) associated with the use of systemic antifungal drugs in patients hospitalized at a high-complexity hospital. In addition, factors associated with ADRs were investigated. This cross-sectional retrospective study involved the investigation of 183 medical records of patients receiving systemic antifungal therapy. Antifungal drugs were classified using the fourth level of the Anatomical Therapeutic Chemical System. ADR causality was classified using the Naranjo algorithm. Drug interactions were assessed using DRUG-REAX software. Data were analyzed with descriptive statistics and univariate and multivariate logistic regression. A total of 53 patients (29.0%) had at least 1 ADR involving antifungals. Ninety-six ADRs were detected. The main ADRs observed were an infusion reaction in 24 patients (25.0%), hypokalemia in 22 (22.9%), nephrotoxicity in 18 (18.7%), and hepatotoxicity in 15 (15.6%). Amphotericin B and voriconazole were associated with ADRs of major clinical impact. Eleven of the ADRs (11.4%) were related to drug interactions. The following 3 factors were contributors to the multivariate model for the occurrence of ADRs caused by antifungal drug use: neoplasm diagnosis (odds ratio [OR], 3.9; 1.9-7.9), length of hospital stay (OR, 2.2; 1.1-4.5), and the use of ≥13 drugs (OR, 3.4; 1.6-7.2). Our study revealed positive associations between the occurrence of ADRs and diagnosis of a neoplasm, the length of stay, and the use of multiple drugs concomitant with antifungals. These risk factors should be considered in antifungal stewardship, among other actions, to promote the rational use of antifungal agents.

Longitudinal Analysis of the Effect of Inflammation on Voriconazole Trough Concentrations

Voriconazole (VCZ) exhibits great inter- and intrapatient variability. The latter variation cannot exclusively be explained by concomitant medications, liver disease or dysfunction, and genetic polymorphisms in cytochrome P450 2C19 (CYP2C19). We hypothesized that inflammatory response in patients under VCZ medication might also influence this fluctuation in concentrations. In this study, we explored the association between inflammation, reflected by the C-reactive protein (CRP) concentration, and VCZ trough concentrations over time. A retrospective analysis of data was performed for patients with more than one steady-state VCZ trough concentration and a CRP concentration measured on the same day. A longitudinal analysis was used for series of observations obtained from many study participants over time. The approach involved inclusion of random effects and autocorrelation in linear models to reflect within-person cross-time correlation. A total of 50 patients were eligible for the study, resulting in 139 observations (paired VCZ and CRP concentrations) for the analysis, ranging from 2 to 6 observations per study participant. Inflammation, marked by the CRP concentration, had a significant association with VCZ trough concentrations (P < 0.001). Covariates such as age and interacting comedication ([es]omeprazole), also showed a significant correlation between VCZ and CRP concentrations (P < 0.05). The intrapatient variation of trough concentrations of VCZ was 1.401 (confidence interval [CI], 0.881 to 2.567), and the interpatient variation was 1.756 (CI, 0.934 to 4.440). The autocorrelation between VCZ trough concentrations at two sequential time points was calculated at 0.71 (CI, 0.51 to 0.92). The inflammatory response appears to play a significant role in the largely unpredictable pharmacokinetics of VCZ, especially in patients with high inflammatory response, as reflected by high CRP concentrations.

CNS infections in patients with hematological disorders (including allogeneic stem-cell transplantation)-Guidelines of the Infectious Diseases Working Party (AGIHO) of the German Society of Hematology and Medical Oncology (DGHO)

Diagnosis of CNS infections remains a great challenge in patients with hematological disorders since symptoms might both be masked and be mimicked by other conditions such as metabolic disturbances or consequences from antineoplastic treatment. Thus, awareness of this complication is crucial and any suspicion of a CNS infection should lead to timely and adequate diagnostics and treatment to improve the outcome in this population.

Infections of the central nervous system (CNS) are infrequently diagnosed in immunocompetent patients, but they do occur in a significant proportion of patients with hematological disorders. In particular, patients undergoing allogeneic hematopoietic stem-cell transplantation carry a high risk for CNS infections of up to 15%. Fungi and Toxoplasma gondii are the predominant causative agents. The diagnosis of CNS infections is based on neuroimaging, cerebrospinal fluid examination and biopsy of suspicious lesions in selected patients. However, identification of CNS infections in immunocompromised patients could represent a major challenge since metabolic disturbances, side-effects of antineoplastic or immunosuppressive drugs and CNS involvement of the underlying hematological disorder may mimic symptoms of a CNS infection. The prognosis of CNS infections is generally poor in these patients, albeit the introduction of novel substances (e.g. voriconazole) has improved the outcome in distinct patient subgroups. This guideline has been developed by the Infectious Diseases Working Party (AGIHO) of the German Society of Hematology and Medical Oncology (DGHO) with the contribution of a panel of 14 experts certified in internal medicine, hematology/oncology, infectious diseases, intensive care, neurology and neuroradiology. Grades of recommendation and levels of evidence were categorized by using novel criteria, as recently published by the European Society of Clinical Microbiology and Infectious Diseases.