Novel insights into the complex pharmacokinetics of voriconazole: a review of its metabolism

Development and validation of a clinical risk score nomogram for predicting voriconazole trough concentration above 5 mg/L: a retrospective cohort study

The therapeutic range of voriconazole (VRC) is narrow, this study aimed to explore factors influencing VRC plasma concentrations > 5 mg/L and to construct a clinical risk score nomogram prediction model. Clinical data from 221 patients with VRC prophylaxis and treatment were retrospectively analyzed. The patients were randomly divided into a training cohort and a validation cohort at a 7:3 ratio. Univariate and binary logistic regression analysis was used to select independent risk factors for VRC plasma concentration above the high limit (5 mg/L). Four indicators including age, weight, CYP2C19 genotype, and albumin were selected to construct the nomogram prediction model. The area under the curve values of the training cohort and the validation cohort were 0.841 and 0.802, respectively. The decision curve analysis suggests that the nomogram model had good clinical applicability. In conclusion, the nomogram provides a reference for early screening and intervention in a high-risk population.

Metamizole induces voriconazole metabolism and results in subtherapeutic voriconazole concentrations

AIMS

Voriconazole is extensively metabolized via cytochrome P450 (CYP) enzymes, predominantly CYP2C19 and CYP3A4. Drugs influencing the activity or expression of CYP enzymes can cause clinically relevant changes in the metabolism and voriconazole exposure. Metamizole is known to induce CYP3A4 and CYP2C19. This study aimed to investigate the pharmacokinetic drug-drug interaction between metamizole and voriconazole.

METHODS

In this single-centre retrospective observational cohort study, we compared voriconazole serum trough concentrations before, during and after metamizole treatment.

RESULTS

In the 9 included patients, the median voriconazole trough concentration decreased by 71% during metamizole treatment (P = .028) compared to before start of metamizole. The concentration/dose ratio similarly decreased by 81% during metamizole treatment (P = .018). Additionally, the metabolic ratio (voriconazole-n-oxide/voriconazole) increased from 0.9 to 2.4 (P = .028) during metamizole treatment. Subtherapeutic voriconazole trough concentrations were more frequent when combined with metamizole (before 14%, during 70%, after 17%).

CONCLUSIONS

Metamizole increases voriconazole metabolism and decreases voriconazole trough concentrations, probably through a CYP3A4 and CYP2C19 inducing effect. It is recommended to avoid concurrent use of metamizole and voriconazole or to closely monitor voriconazole trough concentrations during metamizole treatment and up to 2 weeks after discontinuation of metamizole.

Influence of the ABCB1-rs1045642 gene polymorphism on blood drug concentration in voriconazole-treated patients with severe invasive fungal infection

This study aimed to investigate the impact of the ABCB1-rs1045642 gene polymorphism on the blood drug concentrations of voriconazole in patients with severe invasive fungal infections. A total of 101 patients treated with voriconazole were enrolled in this study. Polymerase chain reaction and Sanger sequencing were used to detect the genotype of ABCB1-rs1045642, and enzyme amplified immunoassay was used to detect the plasma trough concentration of voriconazole. We analyzed the impacts of patient genotype and the minimum concentration of voriconazole as well as investigated the treatment efficacy and rates of adverse reactions in patients with different genotypes. All subjects received standard-dose voriconazole treatment for 1 week, and the mean plasma concentration was found to be 4.5 (3.10, 6.90) mg/L. Three genotypes of ABCB1-rs1045642 were found in the study cohort, namely, wild type (CC type), heterozygous mutant type (CT type), and homozygous mutant type (TT type). There were 18 TT, 48 CT, and 35 CC type cases. Patients with different genotype groups and varying plasma trough concentrations did not differ statistically significantly in terms of the treatment efficacy or incidence of adverse events. Voriconazole plasma concentrations differed significantly among patients of different genders and ABCB1-rs1045642 genotypes. By incorporating gender into the multiple regression model, the regression equations were obtained as C1 = 6.09-1.33×Gender (male = 0, female = 1)-0.47× X1 (X1: T/T = 1, non-T/T = 0) and C2 = 6.09-1.33×Gender (male = 0, female = 1)-0.94×X1 (X1: T/T = 1, non-T/T = 0). The ABCB1-rs1045642 genotype was not found to affect voriconazole plasma trough concentrations in patients with invasive fungal infections admitted to the intensive care unit.

Population pharmacokinetic analysis of intravenous voriconazole in cancer patients

PURPOSE

The pharmacokinetics of voriconazole have been studied across various populations but data specific to the Pakistani cancer population has not yet been reported. The aim of present study was to explore and identify covariates that affect pharmacokinetics of intravenous voriconazole in Pakistani cancer population.

METHODS

The therapeutic drug monitoring data from January1st, 2023 to December 31st, 2023 of cancer patients receiving intravenous voriconazole for systemic fungal infections were taken from electronic medical record of the hospital. The data were used for the development of population pharmacokinetic model using NONMEM. Impact of various covariates such as age, weight, sex, liver function test, serum creatinine, creatinine clearance, type of cancer (primary diagnosis) and type of fungal infection were assessed through stepwise covariate modeling. Bootstrap analysis and goodness of fit plots were used to evaluate robustness and predictive performance of final model.

RESULTS

One compartment model best described the included data with first order elimination. The value of voriconazole clearance was 6.17 L/h with interindividual variability of 83.7% while volume of distribution was 55.9 L. The clearance of voriconazole was significantly influenced by renal status of patients. Creatinine clearance and primary diagnosis were significant covariates affecting clearance of voriconazole in covariate analysis.

CONCLUSION

The findings suggest that this model can be used for dosage adjustment based on creatinine clearance and primary diagnosis as they impact significantly on voriconazole clearance in cancer patients. This approach is especially valuable in resource-limited settings like Pakistan, where individualized therapy can enhance the safety and efficacy of antifungal treatment, addressing the unique clinical and demographic challenges in vulnerable populations.

Drug-drug interaction of phenytoin sodium and methylprednisolone on voriconazole: a population pharmacokinetic model in children with thalassemia undergoing allogeneic hematopoietic stem cell transplantation

PURPOSE

Voriconazole (VRC) is recommended for the prevention and treatment of invasive fungal infections in children undergoing hematopoietic stem cell transplantation (HSCT). It demonstrates nonlinear pharmacokinetics (PK) and exhibits substantial inter- and intraindividual variability. Phenytoin sodium (PHT) and methylprednisolone (MP) are commonly used in the early stages of HSCT to prevent epilepsy and graft-versus-host disease. Drug-drug interactions between VRC and these medications represent a significant concern in HSCT recipients. This study aims to investigate the effects of coadministration with PHT, MP, and other covariates on VRC metabolism in children with thalassemia (TM) undergoing allogeneic HSCT (Allo-HSCT) using population pharmacokinetics (PPK) and to recommend the optimal dosage regimen for this unique group.

METHODS

A total of 237 samples from 57 children with TM undergoing Allo-HSCT were collected. Non-linear mixed effects modeling and Monte Carlo simulation (MCS) were applied for PPK analysis and for optimizing VRC dosing, respectively.

RESULTS

The VRC data were characterized by a two-compartment model with linear elimination and first-order absorption. All parameters were incorporated in allometric scaling form, with PHT and MP significantly influencing VRC clearance. The MCS revealed a negative correlation between the children's body weight (ranging from 10 to 40 kg) and the required dose. When PHT was co-administered, approximately three times the regular dose of VRC was required. In contrast, when MP was administered together, the dose needed to be increased by 12.5-50%.

CONCLUSION

The proposed regimen improved the probability of target attainment for VRC and may serve as a reference for the individualized administration of VRC in clinical practice.

Biowaiver monographs for immediate-release solid oral dosage forms: Voriconazole

According to the ICH M9 Guideline, the triazole antifungal voriconazole is a Biopharmaceutics Classification System (BCS) class II drug, being highly soluble at the highest dose strength but not at the highest single dose. Although the ICH M9 allows for consideration of BCS-based biowaivers in such cases, voriconazole does not meet the additional requirement of dose proportional pharmacokinetics (PK) over the therapeutic dose range. By contrast, if the classification were based on the FDA solubility criteria that were in place prior to ICH M9 (based on the highest dose strength), voriconazole would belong to BCS class I and thus qualify for the BCS-based biowaiver. Since the highest oral dose strength of voriconazole dissolves very rapidly under all BCS conditions, and comparative in vitro dissolution of different tablet formulations aligns with the demonstration of BE in clinical studies, it seems that the ICH Guideline may be unnecessarily restrictive in the case of voriconazole. Therefore, this review discusses potential revisions of eligibility criteria and the extension of biowaiver approvals to encompass a wider range of appropriate drugs. Specifically, a classification system that is more relevant to in vivo conditions, the refined Developability Classification System (rDCS), coupled with biorelevant dissolution testing, may be more applicable to compounds like voriconazole.

In vitro screening of UGT2B10 in silico prioritized putative ligands from drugs used in the pediatric hematopoietic stem cell transplantation setting

UGT2B10 is a phase II drug metabolizing enzyme with limited information on its role in the metabolism of drugs, especially in the pediatric hematopoietic stem cell transplantation setting. Previously, we investigated UGT2B10's role through in silico analyses and prioritized acetaminophen (APAP), lorazepam (LOR), mycophenolic acid (MPA), and voriconazole N-oxide (VCZ N-oxide) for in vitro investigations. In this report, we present in vitro screening of these candidates and of voriconazole (VCZ) to assess their potential to be substrates and/or inhibitors of UGT2B10. Enzyme kinetics experiments included recombinant UGT2B10 and analytical methods based on ultra high-performance liquid chromatography coupled to mass spectrometry (UHPLC-MS). To determine potential substrates, candidates were incubated at various therapeutically observed concentrations with recombinant UGT2B10 to identify the corresponding glucuronide metabolite. Inhibition capacity was tested using the selective probe cotinine for its glucuronidation to cotinine N-ß-d-glucuronide. IC50 was determined for compounds exhibiting inhibition. Among the tested compounds, LOR (IC50 = 0.01 μM, R2 = 0.9257) and MPA (IC50 = 0.38 mM, R2 = 0.9212) exhibited inhibition potential for UGT2B10. None of the other tested compounds featured inhibition potential and none of the compounds tested exhibited metabolism through UGT2B10. Further exploration on the clinical relevance of this inhibition using modeling strategies, overlapping nature with other UGT isoforms, and screening other molecules for their inhibition potential on UGT2B10 is warranted.

Understanding Voriconazole Metabolism: A Middle-Out Physiologically-Based Pharmacokinetic Modelling Framework Integrating In Vitro and Clinical Insights

BACKGROUND AND OBJECTIVE

Voriconazole (VRC), a broad-spectrum antifungal drug, exhibits nonlinear pharmacokinetics (PK) due to saturable metabolic processes, autoinhibition and metabolite-mediated inhibition on their own formation. VRC PK is also characterised by high inter- and intraindividual variability, primarily associated with cytochrome P450 (CYP) 2C19 genetic polymorphism. Additionally, recent in vitro findings indicate that VRC main metabolites, voriconazole N-oxide (NO) and hydroxyvoriconazole (OHVRC), inhibit CYP enzymes responsible for VRC metabolism, adding to its PK variability. This variability poses a significant risk of therapeutic failure or adverse events, which are major challenges in VRC therapy. Understanding the underlying processes and sources of these variabilities is essential for safe and effective therapy. This work aimed to develop a whole-body physiologically-based pharmacokinetic (PBPK) modelling framework that elucidates the complex metabolism of VRC and the impact of its metabolites, NO and OHVRC, on the PK of the parent, leveraging both in vitro and in vivo clinical data in a middle-out approach.

METHODS

A coupled parent-metabolite PBPK model for VRC, NO and OHVRC was developed in a stepwise manner using PK-Sim® and MoBi®. Based on available in vitro data, NO formation was assumed to be mediated by CYP2C19, CYP3A4, and CYP2C9, while OHVRC formation was attributed solely to CYP3A4. Both metabolites were assumed to be excreted via renal clearance, with hepatic elimination also considered for NO. Inhibition functions were implemented to describe the complex interaction network of VRC autoinhibition and metabolite-mediated inhibition on each CYP enzyme.

RESULTS

Using a combined bottom-up and middle-out approach, incorporating data from multiple clinical studies and existing literature, the model accurately predicted plasma concentration-time profiles across various intravenous dosing regimens in healthy adults, of different CYP2C19 genotype-predicted phenotypes. All (100%) of the predicted area under the concentration-time curve (AUC) and 94% of maximum concentration (Cmax) values of VRC met the 1.25-fold acceptance criterion, with overall absolute average fold errors of 1.12 and 1.14, respectively. Furthermore, all predicted AUC and Cmax values of NO and OHVRC met the twofold acceptance criterion.

CONCLUSION

This comprehensive parent-metabolite PBPK model of VRC quantitatively elucidated the complex metabolism of the drug and emphasised the substantial impact of the primary metabolites on VRC PK. The comprehensive approach combining bottom-up and middle-out modelling, thereby accounting for VRC autoinhibition, metabolite-mediated inhibition, and the impact of CYP2C19 genetic polymorphisms, enhances our understanding of VRC PK. Moreover, the model can be pivotal in designing further in vitro experiments, ultimately allowing for extrapolation to paediatric populations, enhance treatment individualisation and improve clinical outcomes.

A physiologically based pharmacokinetic model of voriconazole in human CNS-Integrating time-dependent inhibition of CYP3A4, genetic polymorphisms of CYP2C19 and possible transporter mechanisms

OBJECTIVES

Voriconazole is a classical antifungal drug that is often used to treat CNS fungal infections due to its permeability through the BBB. However, its clinical use remains challenging because of its narrow therapeutic window and wide inter-individual variability. In this study, we proposed an optimised and validated PBPK model by integrating in vitro, in vivo and clinical data to simulate the distribution and PK process of voriconazole in the CNS, providing guidance for clinical individualised treatment.

METHODS

The model structure was optimised and tissue-to-plasma partition coefficients were obtained through animal experiments. Using the allometric relationships, the distribution of voriconazole in the human CNS was predicted. The model integrated factors affecting inter-individual variation and drug interactions of voriconazole-polymorphisms in the CYP2C19 gene and auto-inhibition and then was validated using real clinical data.

RESULTS

The overall AFE value showing model predicted differences was 1.1420 in the healthy population; and in the first prediction of plasma and CSF in actual clinical patients, 89.5% of the values were within the 2-fold error interval, indicating good predictive performance of the model. The bioavailability of voriconazole varied at different doses (39%-86%), and the optimised model conformed to this pattern (46%-83%).

CONCLUSIONS

Combined with the relevant pharmacodynamic indexes, the PBPK model provides a feasible way for precise medication in patients with CNS infection and improve the treatment effect and prognosis.

Voriconazole as an alternative oral treatment in fluconazole-resistant urinary candidiasis

OBJECTIVES

This study aims to assess the urinary diffusion and clinical effectiveness of voriconazole in patients with fluconazole-resistant urinary candidiasis.

PATIENTS AND METHODS

In this prospective pilot study, we utilized a validated chromatography method to measure voriconazole in urine over a 12-hour period between two administrations of the drug and in plasma at trough.

RESULTS

Thirty-five patients, including five with fluconazole-resistant urinary candidiasis, were included. Urine and plasma voriconazole concentrations, mean 1.7 mg/L (range: 0.3-12.6) and mean 2.0 mg/L (range: 0.1-11.1) respectively, exhibited a strong correlation (R2 = 0.88). None of the five patients treated for candidiasis experienced clinical or microbiological failure following treatment, with urine concentrations ranging from 0.5 to 2.7 mg/L.

CONCLUSIONS

The urinary diffusion of voriconazole resulted in drug exposure above the target minimum inhibitory concentration (MIC) in the five patients treated for voriconazole-susceptible Candida strains in urine. Therapeutic drug monitoring may allow optimize in situ concentrations.

Interaction of age and CYP2C19 genotypes on voriconazole steady-state trough concentration in Chinese patients

OBJECTIVES

Both age and CYP2C19 genotypes affect voriconazole plasma concentration; the interaction of age and CYP2C19 genotypes on voriconazole plasma concentration remains unknown. This study aims to investigate the combined effects of age and CYP2C19 genotypes on voriconazole plasma concentration in Chinese patients.

METHODS

A total of 480 patients who received voriconazole treatment were recruited. CYP2C19*2 (rs4244285) and CYP2C19*3 (rs4986893) polymorphisms were genotyped. Patients were divided into the young and the elderly groups by age of 60 years old. Influence of CYP2C19 genotype on steady-state trough concentration (C ss-min ) in overall patients and in age subgroups was analyzed.

RESULTS

Voriconazole C ss-min correlated positively with age, and mean voriconazole C ss-min was significantly higher in the elderly group ( P  < 0.001). CYP2C19 poor metabolizers showed significantly increased mean voriconazole C ss-min in the young but not the elderly group. The percentage of patients with subtherapeutic voriconazole C ss-min (<1.0 mg/l) was higher in the young group and that of supratherapeutic voriconazole C ss-min (>5.5 mg/l) was higher in the elderly patients. When the average C ss-min in the CYP2C19 normal metabolizer genotype was regarded as a reference, CYP2C19 genotypes showed greater impact on voriconazole C ss-min in the young group, while the influence of age on voriconazole C ss-min exceeded CYP2C19 genotypes in the elderly.

CONCLUSION

CYP2C19 genotypes affects voriconazole exposure is age dependent. Influence of CYP2C19 poor metabolizer genotype on increased voriconazoleexposure is prominent in the young, while age is a more important determinant factor for increased voriconazole exposure in the elderly patients.

Mass spectrometric methods for evaluation of voriconazole avian pharmacokinetics and the inhibition of its cytochrome P450-induced metabolism

Invasive fungal aspergillosis is a leading cause of morbidity and mortality in many species including avian species such as common ravens (Corvus corax). Methods were developed for mass spectral determination of voriconazole in raven plasma as a means of determining pharmacokinetics of this antifungal agent. Without further development, GC/MS/MS (gas chromatography-tandem quadrupole mass spectrometry) proved to be inferior to LC/MS/MS (liquid chromatography-tandem quadrupole mass spectrometry) for measurement of voriconazole levels in treated raven plasma owing to numerous heat-induced breakdown products despite protection of voriconazole functional groups with trimethylsilyl moieties. LC/MS/MS measurement revealed in multi-dosing experiments that the ravens were capable of rapid or ultrarapid metabolism of voriconazole. This accounted for the animals' inability to raise the drug into the therapeutic range regardless of dosing regimen unless cytochrome P450 (CYP) inhibitors were included. Strategic selection of CYP inhibitors showed that of four selected compounds including cimetidine, enrofloxacin and omeprazole, only ciprofloxacin (Cipro) was able to maintain voriconazole levels in the therapeutic range until the end of the dosing period. The optimal method of administration involved maintenance doses of voriconazole at 6 mg/kg and ciprofloxacin at 20 mg/kg. Higher doses of voriconazole such as 18 mg/kg were also tenable without apparent induction of toxicity. Although most species employ CYP2C19 to metabolize voriconazole, it was necessary to speculate that voriconazole might be subject to metabolism by CYP1A2 in the ravens to explain the utility of ciprofloxacin, a previously unknown enzymatic route. Finally, despite its widespread catalog of CYP inhibitions including CYP1A2 and CYP2C19, cimetidine may be inadequate at enhancing voriconazole levels owing to its known effects on raising gastric pH, a result that may limit voriconazole solubility.

Pharmacological management of invasive mold infections in solid organ transplant recipients

INTRODUCTION

Solid organ transplant (SOT) recipients face an increased susceptibility to invasive fungal infection (IFI) due to filamentous fungi. Post-transplant invasive aspergillosis (IA) and mucormycosis are related to exceedingly high mortality rates and graft loss risk, and its management involve a unique range of clinical challenges.

AREAS COVERED

First, the current treatment recommendations for IA and mucormycosis among SOT recipients are critically reviewed, including the supporting evidence. Next, we discussed particular concerns in this patient population, such as drug-drug interactions (DDIs) between triazoles and post-transplant immunosuppression or treatment-related toxicity. The role for immunomodulatory and host-targeted therapies is also considered, as well as the theoretical impact of the intrinsic antifungal activity of calcineurin inhibitors. Finally, a personal opinion is made on future directions in the pharmacological approach to post-transplant IFI.

EXPERT OPINION

Despite relevant advances in the treatment of mold IFIs in the SOT setting, such as the incorporation of isavuconazole (with lower incidence of DDIs and better tolerability than voriconazole), there remains a large room for improvement in areas such as the position of combination therapy or the optimal strategy for the reduction of baseline immunosuppression. Importantly, future studies should define the specific contribution of newer antifungal agents and classes.

Can we predict the influence of inflammation on voriconazole exposure? An overview

Voriconazole is a triazole antifungal indicated for invasive fungal infections that exhibits a high degree of inter-individual and intra-individual pharmacokinetic variability. Voriconazole pharmacokinetics is non-linear, making dosage adjustments more difficult. Therapeutic drug monitoring is recommended by measurement of minimum plasma concentrations. Several factors are responsible for the high pharmacokinetic variability of voriconazole: age, feeding (which decreases absorption), liver function, genetic polymorphism of the CYP2C19 gene, drug interactions and inflammation. Invasive fungal infections are indeed very frequently associated with inflammation, which engenders a risk of voriconazole overexposure. Many studies have reviewed this topic in both the adult and paediatric populations, but few studies have focused on the specific point of the prediction, to evaluate the influence of inflammation on voriconazole pharmacokinetics. Predicting the impact of inflammation on voriconazole pharmacokinetics could help optimize antifungal therapy and improve patient management. This review summarizes the existing data on the influence of inflammation on voriconazole pharmacokinetics in adult populations. We also evaluate the role of C-reactive protein, the impact of inflammation on patient metabolic phenotypes, and the tools that can be used to predict the effect of inflammation on voriconazole pharmacokinetics.

Electrochemical Simulation of Phase I Hepatic Metabolism of Voriconazole Using a Screen-Printed Iron(II) Phthalocyanine Electrode

Understanding the metabolism of pharmaceutical compounds is a fundamental prerequisite for ensuring their safety and efficacy in clinical use. However, conventional methods for monitoring drug metabolism often come with the drawbacks of being time-consuming and costly. In an ongoing quest for innovative approaches, the application of electrochemistry in metabolism studies has gained prominence as a promising approach for the synthesis and analysis of drug transformation products. In this study, we investigated the hepatic metabolism of voriconazole, an antifungal medication, by utilizing human liver microsomes (HLM) assay coupled with LC-MS. Based on the obtained results, the electrochemical parameters were optimized to simulate the biotransformation reactions. Among the various electrodes tested, the chemometric analysis revealed that the iron(II) phthalocyanine electrode was the most effective in catalyzing the formation of all hepatic voriconazole metabolites. These findings exemplify the potential of phthalocyanine electrodes as an efficient and cost-effective tool for simulating the intricate metabolic processes involved in drug biotransformation, offering new possibilities in the field of pharmaceutical research. Additionally, in silico analysis showed that two detected metabolites may exhibit significantly higher acute toxicity and mutagenic potential than the parent compound.

Towards Model-Informed Precision Dosing of Voriconazole: Challenging Published Voriconazole Nonlinear Mixed-Effects Models with Real-World Clinical Data

BACKGROUND AND OBJECTIVES

Model-informed precision dosing (MIPD) frequently uses nonlinear mixed-effects (NLME) models to predict and optimize therapy outcomes based on patient characteristics and therapeutic drug monitoring data. MIPD is indicated for compounds with narrow therapeutic range and complex pharmacokinetics (PK), such as voriconazole, a broad-spectrum antifungal drug for prevention and treatment of invasive fungal infections. To provide guidance and recommendations for evidence-based application of MIPD for voriconazole, this work aimed to (i) externally evaluate and compare the predictive performance of a published so-called 'hybrid' model for MIPD (an aggregate model comprising features and prior information from six previously published NLME models) versus two 'standard' NLME models of voriconazole, and (ii) investigate strategies and illustrate the clinical impact of Bayesian forecasting for voriconazole.

METHODS

A workflow for external evaluation and application of MIPD for voriconazole was implemented. Published voriconazole NLME models were externally evaluated using a comprehensive in-house clinical database comprising nine voriconazole studies and prediction-/simulation-based diagnostics. The NLME models were applied using different Bayesian forecasting strategies to assess the influence of prior observations on model predictivity.

RESULTS

The overall best predictive performance was obtained using the aggregate model. However, all NLME models showed only modest predictive performance, suggesting that (i) important PK processes were not sufficiently implemented in the structural submodels, (ii) sources of interindividual variability were not entirely captured, and (iii) interoccasion variability was not adequately accounted for. Predictive performance substantially improved by including the most recent voriconazole observations in MIPD.

CONCLUSION

Our results highlight the potential clinical impact of MIPD for voriconazole and indicate the need for a comprehensive (pre-)clinical database as basis for model development and careful external model evaluation for compounds with complex PK before their successful use in MIPD.

CYP3A and CYP2C19 Activity Determined by Microdosed Probe Drugs Accurately Predict Voriconazole Clearance in Healthy Adults

BACKGROUND AND OBJECTIVE

Voriconazole is an important broad-spectrum anti-fungal drug with nonlinear pharmacokinetics. The aim of this single centre fixed-sequence open-label drug-drug interaction trial in healthy participants (N = 17) was to determine whether microdosed probe drugs for CYP3A and CYP2C19 reliably predict voriconazole clearance (CLVRZ).

METHODS

At baseline, a single oral microdose of the paradigm substrates midazolam (CYP3A) and omeprazole (CYP2C19) were given to estimate their clearances (CL). Thereafter, a single oral dose of voriconazole was administered (50, 100, 200 or 400 mg), followed by the microdosed probe drugs.

RESULTS

The clearances of midazolam (CLMDZ 790-2790 mL/min at baseline; 248-1316 mL/min during voriconazole) and omeprazole (CLOMZ 66.4-2710 mL/min at baseline; 30.1-1420 mL/min during voriconazole) were highly variable. CLMDZ [geometric mean ratio (GMR) 0.586 at 50 mg voriconazole decreasing to GMR 0.196 at 400 mg voriconazole] and CLOMZ (GMR 0.590 at 50 mg decreasing to GMR 0.166 at 400 mg) were reduced with higher voriconazole doses. CLMDZ was linearly correlated with CLVRZ (slope 1.458; adjusted R2 0.528) as was CLOMZ (slope 0.807; adjusted R2 0.898). Multiple linear regression resulted in an adjusted R2 of 0.997 for the relationship CLVRZ ~ log CLOMZ + log CLMDZ using data during voriconazole treatment and an adjusted R2 of 0.997 for the relationship CLVRZ ~ log CLOMZ + log CLMDZ + voriconazole dose, using baseline data for CLMDZ and CLOMZ.

CONCLUSION

Microdosed midazolam and omeprazole accurately described and predicted total CLVRZ TRIAL REGISTRATION: EudraCT No: 2020-001017-20, registered on March 5th, 2020. DRKS: DRKS00022547, registered on August 6th, 2020.

Observed isavuconazole exposure: 5-year experience of azole TDM from a Spanish reference laboratory

We aimed to assess patient exposure to isavuconazole (ISZ) from samples received in our laboratory for therapeutic antifungal monitoring. We used liquid chromatography coupled with ultraviolet (UV) absorbance detection adapted from a multiplex-validated method with photodiode array (PDA) detection to monitor the analytes. The latter device allows the characterization of the azoles UV spectra. The method was validated according to international guidelines for efficient ISZ monitoring. The assay exhibited linearity between 0.25 and 16 mg/l for ISZ. Accuracy and intra- and inter-day precision were within acceptable ranges, and the method was successfully applied to quantify azoles and major metabolites from clinical samples collected from treated patients. We focus on ISZ blood concentrations and compared them to those of voriconazole, posaconazole, and itraconazole for a period of 5 years (2017-2021). Median ISZ concentration was 2.92 mg/l (interquartile range 1.82-5.33 mg/l) with 89% of measurements classified as adequate exposure (> 1 mg/l). Additionally, 71% of samples reach concentration values > 2 mg/l. Different ISZ exposure between adults to children were found. In conclusion, ISZ achieves excellent blood concentrations compared to other azole drugs, they are almost identical to those previously described, they exceed the MICs of most fungi for which its use was recommended and they differ depending on the patient's age. The method we describe for antifungal monitoring is simple, robust, and efficient. It simultaneously analyzes azoles and metabolites, and can be used for tailored interventions, achieve exposures associated with therapeutic success, decrease treatment-related toxicity, and help prevent resistance emergence due to continuous azole sub-optimal concentrations.

Establishment of a mathematical prediction model for voriconazole stable maintenance dose: a prospective study

Background

In patients with invasive fungal infection (IFI), the steady-state serum trough concentration (C min) of voriconazole (VCZ) is highly variable and can lead to treatment failure (C min < 0.5 mg/L) and toxicity (C min ≥ 5.0 mg/L). However, It remains challenging to determine the ideal maintenance dose to achieve the desired C min level quickly.

Aims

This randomized, prospective observational single-center study aimed to identify factors affecting VCZ-C min and maintenance dose and create an algorithmic model to predict the necessary maintenance dose. MeThe study enrolled 306 adult IFI patients, split into two groups: non-gene-directed (A) (where CYP2C19 phenotype is not involved in determining VCZ dose) and gene-directed (B) (where CYP2C19 phenotype is involved in determining VCZ dose).

Results

Results indicated that CYP2C19 genetic polymorphisms might significantly impact VCZ loading and maintenance dose selection. CYP2C19 phenotype, C-reaction protein (CRP), and average daily dose/body weight were significant influencers on VCZ-C min, while CYP2C19 phenotype, CRP, and body weight significantly impacted VCZ maintenance dose. A feasible predictive formula for VCZ stable maintenance dose was derived from the regression equation as a maintenance dose (mg) =282.774-0.735×age (year)+2.946×body weight(Kg)-19.402×CYP2C19 phenotype (UM/RM/NM:0, IM:1, PM:2)-0.316×CRP (mg/L) (p < 0.001).

Discussion

DiThis formula may serve as a valuable supplement to the Clinical Pharmacogenetics Implementation Consortium (CPIC®) guideline for CYP2C19 and VCZ therapy, especially for IFI patients with highly variable inflammatory cytokines during VCZ therapy.

The Investigation and Prediction of Voriconazole-Associated Hepatotoxicity under Therapeutic Drug Monitoring. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2023;2023:1-4. [PMID: 38082975 DOI: 10.1109/embc40787.2023.10340343] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Voriconazole is commonly used as the first-line agent to treat invasive fungal infections (IFIs), but the induction of hepatotoxicity limits its use. To improve the treatment outcomes and minimize toxicity, doctors often administer Therapeutic Drug Monitoring (TDM) to patients receiving voriconazole treatment. Here, we conducted a real-world clinical investigation of voriconazole-treated patients and found significant differences between the TDM (n=318) and non-TDM cohort (n=6,379), and such incidence of hepatotoxicity showed 10.6% in the non-TDM cohort, compared with 21.5% in the TDM cohort. Based on our previous investigation, we presented and compared several machine learning models (including AdaBoost, decision tree, GBDT, logistic regression, neural networks, and random forest) for the early warning of voriconazole-associated hepatoxicity. Through the five-fold cross validation, the logistic model outperformed other models with a mean AUC of 0.7933±0.0934. Our findings offer important insights into the safe and effective application of voriconazole.

Pharmacokinetics and safety of two Voriconazole formulations after intravenous infusion in two doses in healthy Chinese subjects

BACKGROUND

Voriconazole is a second-generation triazole that is used to prevent and treat invasive fungal infections. The purpose of this study was to evaluate the pharmacokinetic equivalency of a test formulation and reference formulation (Vfend®) of Voriconazole.

MATERIALS AND METHODS

This was a randomized, open-label, single-dose, two-treatment, two-sequence, two-cycle, crossover phase I trial. The 48 subjects were equally divided into 4 mg/kg and 6 mg/kg groups. Within each group, the subjects were randomized 1:1 to the test or reference formulation.. After a 7-day washout period, crossover formulations were administered. The blood samples were collected at 0.5, 1.0, 1.33,1.42,1.5, 1.75, 2.0, 2.5, 3.0, 4.0, 6.0, 8.0, 12.0, 24.0, 36.0, 48.0 h later in the 4 mg/kg group, while at 0.5, 1.0, 1.5, 1.75, 2.0, 2.08, 2.17, 2.33, 2.5, 3.0, 4.0, 6.0, 8.0, 12.0, 24.0, 36.0, 48.0 h later in the 6 mg/kg group. The plasma concentrations of Voriconazole were determined by Liquid chromatography-tandem mass spectrometry (LC-MS/MS). The safety of the drug was evaluated.

RESULTS

The 90% confidence intervals (CIs) of the ratio of geometric means (GMRs) of C_max, AUC_0-t, and AUC_0-∞ in both 4 mg/kg and 6 mg/kg groups were within the prespecified bioequivalence limits between 80 ~ 125%. In the 4 mg/kg groups, 24 subjects were enrolled and completed the study. The mean C_max was (2.552 ± 0.448) μg/mL, AUC_0-t was (11.875 ± 7.157) h*μg/mL and AUC_0-∞ was (12.835 ± 9.813) h*μg/mL after a single dose of 4 mg/kg test formulation. The mean C_max was (2.615 ± 0.464) μg/mL, AUC_0-t was (12.500 ± 7.257) h*μg/mL and AUC_0-∞ was (13.416 ± 9.485) h*μg/mL after a single dose of 4 mg/kg reference formulation. In the 6 mg/kg groups, 24 subjects were enrolled and completed the study. The mean C_max was (3.538 ± 0.691) μg/mL, AUC_0-t was (24.976 ± 12.364) h*μg/mL and AUC_0-∞ was (26.212 ± 14.057) h*μg/mL after a single dose of 6 mg/kg test formulation. The mean C_max was (3.504 ± 0.667) μg/mL AUC_0-t was (24.990 ± 12.455) h*μg/mL and AUC_0-∞ was (26.160 ± 13.996) h*μg/mL after a single dose of 6 mg/kg reference formulation. Serious adverse event (SAE) was not observed.

CONCLUSION

In both 4 mg/kg group and 6 mg/kg group, equivalent pharmacokinetic characteristics that satisfied the criteria of bioequivalence for both test and reference formulations of Voriconazole.

TRIAL REGISTRATION

NCT05330000 (15/04/2022).

Nanocarriers for the Delivery of Neuroprotective Agents in the Treatment of Ocular Neurodegenerative Diseases

Retinal neurodegeneration is considered an early event in the pathogenesis of several ocular diseases, such as diabetic retinopathy, age-related macular degeneration, and glaucoma. At present, there is no definitive treatment to prevent the progression or reversal of vision loss caused by photoreceptor degeneration and the death of retinal ganglion cells. Neuroprotective approaches are being developed to increase the life expectancy of neurons by maintaining their shape/function and thus prevent the loss of vision and blindness. A successful neuroprotective approach could prolong patients' vision functioning and quality of life. Conventional pharmaceutical technologies have been investigated for delivering ocular medications; however, the distinctive structural characteristics of the eye and the physiological ocular barriers restrict the efficient delivery of drugs. Recent developments in bio-adhesive in situ gelling systems and nanotechnology-based targeted/sustained drug delivery systems are receiving a lot of attention. This review summarizes the putative mechanism, pharmacokinetics, and mode of administration of neuroprotective drugs used to treat ocular disorders. Additionally, this review focuses on cutting-edge nanocarriers that demonstrated promising results in treating ocular neurodegenerative diseases.

Contribution of voriconazole N-oxide plasma concentration measurements to voriconazole therapeutic drug monitoring in patients with invasive fungal infection

BACKGROUND

Voriconazole (VRC), a widely used triazole antifungal, exhibits significant inter- and intra-individual pharmacokinetic variability. The main metabolite voriconazole N-oxide (NOX) can provide information on the patient's drug metabolism capacity.

OBJECTIVES

Our objectives were to implement routine measurement of NOX concentrations and to describe the metabolic ratio (MR), and the contribution of the MR to VRC therapeutic drug monitoring (TDM) by proposing a suggested dosage-adjustment algorithm.

PATIENTS AND METHODS

Sixty-one patients treated with VRC were prospectively included in the study, and VRC and NOX levels were assayed by LC-MS/MS. A mixed logistic model on repeated measures was implemented to analyse risk factors for the patient's concentration to be outside the therapeutic range.

RESULTS

Based on 225 measurements, the median and interquartile range were 2.4 μg/ml (1.2; 4.2), 2.1 μg/ml (1.5; 3.0) and 1.0 (0.6; 1.9) for VRC, NOX and the MR, respectively. VRC C_min <2 μg/ml were associated with a higher MR during the previous visit. MR values >1.15 and <0.48 were determined to be the best predictors for having a VRC C_min lower than 2 μg/ml and above 5.5 μg/ml, respectively, at the next visit.

CONCLUSIONS

Measurement of NOX resulted useful for TDM of patients treated with VRC. The MR using NOX informed interpretation and clinical decision-making and is very interesting for complex patients. VRC phenotyping based on the MR is now performed routinely in our institution. A dosing algorithm has been suggested from these results.

Microdialysis of Voriconazole and its N-Oxide Metabolite: Amalgamating Knowledge of Distribution and Metabolism Processes in Humans

PURPOSE

Voriconazole is an essential antifungal drug whose complex pharmacokinetics with high interindividual variability impedes effective and safe therapy. By application of the minimally-invasive sampling technique microdialysis, interstitial space fluid (ISF) concentrations of VRC and its potentially toxic N-oxide metabolite (NO) were assessed to evaluate target-site exposure for further elucidating VRC pharmacokinetics.

METHODS

Plasma and ISF samples of a clinical trial with an approved VRC dosing regimen were analyzed for VRC and NO concentrations. Concentration-time profiles, exposure assessed as area-under-the-curve (AUC) and metabolic ratios of four healthy adults in plasma and ISF were evaluated regarding the impact of multiple dosing and CYP2C19 genotype.

RESULTS

VRC and NO revealed distribution into ISF with AUC values being ≤2.82- and 17.7-fold lower compared to plasma, respectively. Intraindividual variability of metabolic ratios was largest after the first VRC dose administration while interindividual variability increased with multiple dosing. The CYP2C19 genotype influenced interindividual differences with a maximum 6- and 24-fold larger AUCNO/AUCVRC ratio between the intermediate and rapid metabolizer in plasma and ISF, respectively. VRC metabolism was saturated/auto-inhibited indicated by substantially decreasing metabolic concentration ratios with increasing VRC concentrations and after multiple dosing.

CONCLUSION

The feasibility of the simultaneous microdialysis of VRC and NO in vivo was demonstrated and provided new quantitative insights by leveraging distribution and metabolism processes of VRC in humans. The exploratory analysis suggested substantial dissimilarities of VRC and NO pharmacokinetics in plasma and ISF. Ultimately, a thorough understanding of target-site pharmacokinetics might contribute to the optimization of personalized VRC dosing regimens.

Voriconazole therapeutic drug monitoring and hepatotoxicity in critically ill patients: A nationwide multi-centre retrospective study

OBJECTIVES

To characterize trough concentrations (C_min) of voriconazole and associated hepatotoxicity, and to determine predictors of hepatotoxicity and identify high-risk groups in critically ill patients.

METHODS

This was a nationwide, multi-centre, retrospective study. C_min and hepatotoxicity were studied from 2015 to 2020 in 363 critically ill patients who received voriconazole treatment. Logistic regression and classification and regression tree (CART) models were used to identify high-risk patients.

RESULTS

Large interindividual variability was observed in initial voriconazole C_min and concentrations ranged from 0.1 mg/L to 18.72 mg/L. Voriconazole-related grade ≥2 hepatotoxicity developed in 101 patients, including 48 patients with grade ≥3 hepatotoxicity. The median time to hepatotoxicity was 3 days (range 1-24 days), and 83.2% of cases of hepatotoxicity occurred within 7 days of voriconazole initiation. Voriconazole C_min was significantly associated with hepatotoxicity. The CART model showed that significant predictors of grade ≥2 hepatotoxicity were C_min >3.42 mg/L, concomitant use of trimethoprim-sulfamethoxazole or tigecycline, and septic shock. The model predicted that the incidence of grade ≥2 hepatotoxicity among these high-risk patients was 48.3-63.4%. Significant predictors of grade ≥3 hepatotoxicity were C_min >6.87 mg/L, concomitant use of at least three hepatotoxic drugs, and septic shock; the predictive incidence among these high-risk patients was 22.7-36.8%.

CONCLUSION

Higher voriconazole C_min, septic shock and concomitant use of hepatotoxic drugs were the strongest predictors of hepatotoxicity. Plasma concentrations of voriconazole should be monitored early (as soon as steady state is achieved) to avoid hepatotoxicity.

Microdialysis of Drug and Drug Metabolite: a Comprehensive In Vitro Analysis for Voriconazole and Voriconazole N-oxide

PURPOSE

Voriconazole is a therapeutically challenging antifungal drug associated with high interindividual pharmacokinetic variability. As a prerequisite to performing clinical trials using the minimally-invasive sampling technique microdialysis, a comprehensive in vitro microdialysis characterization of voriconazole (VRC) and its potentially toxic N-oxide metabolite (NO) was performed.

METHODS

The feasibility of simultaneous microdialysis of VRC and NO was explored in vitro by investigating the relative recovery (RR) of both compounds in the absence and presence of the other. The dependency of RR on compound combination, concentration, microdialysis catheter and study day was evaluated and quantified by linear mixed-effects modeling.

RESULTS

Median RR of VRC and NO during individual microdialysis were high (87.6% and 91.1%). During simultaneous microdialysis of VRC and NO, median RR did not change (87.9% and 91.1%). The linear mixed-effects model confirmed the absence of significant differences between RR of VRC and NO during individual and simultaneous microdialysis as well as between the two compounds (p > 0.05). No concentration dependency of RR was found (p = 0.284). The study day was the main source of variability (46.3%) while the microdialysis catheter only had a minor effect (4.33%). VRC retrodialysis proved feasible as catheter calibration for both compounds.

CONCLUSION

These in vitro microdialysis results encourage the application of microdialysis in clinical trials to assess target-site concentrations of VRC and NO. This can support the generation of a coherent understanding of VRC pharmacokinetics and its sources of variability. Ultimately, a better understanding of human VRC pharmacokinetics might contribute to the development of personalized dosing strategies.

Challenges in the Treatment of Invasive Aspergillosis in Immunocompromised Children

Invasive aspergillosis (IA) is associated with significant morbidity and mortality. Voriconazole remains the drug of choice for the treatment of IA in children; however, the complex kinetics of voriconazole in children make dosing challenging and therapeutic drug monitoring (TDM) essential for treatment success. The overarching goal of this review is to discuss the role of voriconazole, posaconazole, isavuconazole, liposomal amphotericin B, echinocandins, and combination antifungal therapy for the treatment of IA in children. We also provide a detailed discussion of antifungal TDM in children.

Towards the Elucidation of the Pharmacokinetics of Voriconazole: A Quantitative Characterization of Its Metabolism

The small-molecule drug voriconazole (VRC) shows a complex and not yet fully understood metabolism. Consequently, its in vivo pharmacokinetics are challenging to predict, leading to therapy failures or adverse events. Thus, a quantitative in vitro characterization of the metabolism and inhibition properties of VRC for human CYP enzymes was aimed for. The Michaelis-Menten kinetics of voriconazole N-oxide (NO) formation, the major circulating metabolite, by CYP2C19, CYP2C9 and CYP3A4, was determined in incubations of human recombinant CYP enzymes and liver and intestine microsomes. The contribution of the individual enzymes to NO formation was 63.1% CYP2C19, 13.4% CYP2C9 and 29.5% CYP3A4 as determined by specific CYP inhibition in microsomes and intersystem extrapolation factors. The type of inhibition and inhibitory potential of VRC, NO and hydroxyvoriconazole (OH-VRC), emerging to be formed independently of CYP enzymes, were evaluated by their effects on CYP marker reactions. Time-independent inhibition by VRC, NO and OH-VRC was observed on all three enzymes with NO being the weakest and VRC and OH-VRC being comparably strong inhibitors of CYP2C9 and CYP3A4. CYP2C19 was significantly inhibited by VRC only. Overall, the quantitative in vitro evaluations of the metabolism contributed to the elucidation of the pharmacokinetics of VRC and provided a basis for physiologically-based pharmacokinetic modeling and thus VRC treatment optimization.

Antifungal Drugs TDM: Trends and Update

PURPOSE

The increasing burden of invasive fungal infections results in growing challenges to antifungal (AF) therapeutic drug monitoring (TDM). This review aims to provide an overview of recent advances in AF TDM.

METHODS

We conducted a PubMed search for articles during 2016-2020 using "TDM" or "pharmacokinetics" or "drug-drug-interaction" with "antifungal," consolidated for each AF. Selection was limited to English language articles with human data on drug exposure.

RESULTS

More than 1000 articles matched the search terms. We selected 566 publications. The latest findings tend to confirm previous observations in real-life clinical settings. The pharmacokinetic variability related to special populations is not specific but must be considered. AF benefit-to-risk ratio, drug-drug interaction (DDI) profiles, and minimal inhibitory concentrations for pathogens must be known to manage at-risk situations and patients. Itraconazole has replaced ketoconazole in healthy volunteers DDI studies. Physiologically based pharmacokinetic modeling is widely used to assess metabolic azole DDI. AF prophylactic use was studied more for Aspergillus spp. and Mucorales in oncohematology and solid organ transplantation than for Candida (already studied). Emergence of central nervous system infection and severe infections in immunocompetent individuals both merit special attention. TDM is more challenging for azoles than amphotericin B and echinocandins. Fewer TDM requirements exist for fluconazole and isavuconazole (ISZ); however, ISZ is frequently used in clinical situations in which TDM is recommended. Voriconazole remains the most challenging of the AF, with toxicity limiting high-dose treatments. Moreover, alternative treatments (posaconazole tablets, ISZ) are now available.

CONCLUSIONS

TDM seems to be crucial for curative and/or long-term maintenance treatment in highly variable patients. TDM poses fewer cost issues than the drugs themselves or subsequent treatment issues. The integration of clinical pharmacology into multidisciplinary management is now increasingly seen as a part of patient care.

Application of Population Pharmacokinetic Analysis to Characterize CYP2C19 Mediated Metabolic Mechanism of Voriconazole and Support Dose Optimization

Purpose: The aims of this study were to establish a joint population pharmacokinetic model for voriconazole and its N-oxide metabolite in immunocompromised patients, to determine the extent to which the CYP2C19 genetic polymorphisms influenced the pharmacokinetic parameters, and to evaluate and optimize the dosing regimens using a simulating approach.

Methods: A population pharmacokinetic analysis was conducted using the Phoenix NLME software based on 427 plasma concentrations from 78 patients receiving multiple oral doses of voriconazole (200 mg twice daily). The final model was assessed by goodness of fit plots, non-parametric bootstrap method, and visual predictive check. Monte Carlo simulations were carried out to evaluate and optimize the dosing regimens.

Results: A one-compartment model with first-order absorption and mixed linear and concentration-dependent-nonlinear elimination fitted well to concentration-time profile of voriconazole, while one-compartment model with first-order elimination well described the disposition of voriconazole N-oxide. Covariate analysis indicated that voriconazole pharmacokinetics was substantially influenced by the CYP2C19 genetic variations. Simulations showed that the recommended maintenance dose regimen would lead to subtherapeutic levels in patients with different CYP2C19 genotypes, and elevated daily doses of voriconazole might be required to attain the therapeutic range.

Conclusions: The joint population pharmacokinetic model successfully characterized the pharmacokinetics of voriconazole and its N-oxide metabolite in immunocompromised patients. The proposed maintenance dose regimens could provide a rationale for dosage individualization to improve clinical outcomes and minimize drug-related toxicities.

Quantification of the Time Course of CYP3A Inhibition, Activation, and Induction Using a Population Pharmacokinetic Model of Microdosed Midazolam Continuous Infusion

BACKGROUND

Cytochrome P450 (CYP) 3A contributes to the metabolism of many approved drugs. CYP3A perpetrator drugs can profoundly alter the exposure of CYP3A substrates. However, effects of such drug-drug interactions are usually reported as maximum effects rather than studied as time-dependent processes. Identification of the time course of CYP3A modulation can provide insight into when significant changes to CYP3A activity occurs, help better design drug-drug interaction studies, and manage drug-drug interactions in clinical practice.

OBJECTIVE

We aimed to quantify the time course and extent of the in vivo modulation of different CYP3A perpetrator drugs on hepatic CYP3A activity and distinguish different modulatory mechanisms by their time of onset, using pharmacologically inactive intravenous microgram doses of the CYP3A-specific substrate midazolam, as a marker of CYP3A activity.

METHODS

Twenty-four healthy individuals received an intravenous midazolam bolus followed by a continuous infusion for 10 or 36 h. Individuals were randomized into four arms: within each arm, two individuals served as a placebo control and, 2 h after start of the midazolam infusion, four individuals received the CYP3A perpetrator drug: voriconazole (inhibitor, orally or intravenously), rifampicin (inducer, orally), or efavirenz (activator, orally). After midazolam bolus administration, blood samples were taken every hour (rifampicin arm) or every 15 min (remaining study arms) until the end of midazolam infusion. A total of 1858 concentrations were equally divided between midazolam and its metabolite, 1'-hydroxymidazolam. A nonlinear mixed-effects population pharmacokinetic model of both compounds was developed using NONMEM^®. CYP3A activity modulation was quantified over time, as the relative change of midazolam clearance encountered by the perpetrator drug, compared to the corresponding clearance value in the placebo arm.

RESULTS

Time course of CYP3A modulation and magnitude of maximum effect were identified for each perpetrator drug. While efavirenz CYP3A activation was relatively fast and short, reaching a maximum after approximately 2-3 h, the induction effect of rifampicin could only be observed after 22 h, with a maximum after approximately 28-30 h followed by a steep drop to almost baseline within 1-2 h. In contrast, the inhibitory impact of both oral and intravenous voriconazole was prolonged with a steady inhibition of CYP3A activity followed by a gradual increase in the inhibitory effect until the end of sampling at 8 h. Relative maximum clearance changes were +59.1%, +46.7%, -70.6%, and -61.1% for efavirenz, rifampicin, oral voriconazole, and intravenous voriconazole, respectively.

CONCLUSIONS

We could distinguish between different mechanisms of CYP3A modulation by the time of onset. Identification of the time at which clearance significantly changes, per perpetrator drug, can guide the design of an optimal sampling schedule for future drug-drug interaction studies. The impact of a short-term combination of different perpetrator drugs on the paradigm CYP3A substrate midazolam was characterized and can define combination intervals in which no relevant interaction is to be expected.

CLINICAL TRIAL REGISTRATION

The trial was registered at the European Union Drug Regulating Authorities for Clinical Trials (EudraCT-No. 2013-004869-14).

A versatile high-performance LC-MS/MS assay for the quantification of voriconazole and its N-oxide metabolite in small sample volumes of multiple human matrices for biomedical applications

Voriconazole (VRC) pharmacokinetics, in particular its complex metabolism, is still not fully understood which challenges its optimal therapeutic use. To increase knowledge on the pharmacokinetics of this antifungal drug, it is essential to broaden the perspective and expand in vitro and clinical in vivo investigations in particular to aspects such as unbound plasma, target-site and metabolite concentrations. Innovative sampling approaches such as microdialysis, a minimally-invasive technique for the analysis of compound concentrations in target-site human tissue fluids, are associated with bioanalytical challenges, i.e. small sample volumes and low concentrations. Thus, a bioanalytical LC-MS/MS assay for the simultaneous quantification of VRC and its main N-oxide (NO) metabolite in human plasma, ultrafiltrate and microdialysate was developed and validated according to the European Medicines Agency guideline. Quantification was rapid, simple and feasible for clinically relevant concentrations from 5 to 5000 ng/mL in plasma and ultrafiltrate as well as from 4 to 4000 ng/mL in microdialysate. Due to the high sensitivity of the assay, only 20 µL of plasma or ultrafiltrate and 5 µL of microdialysate were required. For VRC and NO in all matrices, between-run accuracy was high with a maximum mean deviation of 7.0% from the nominal value and between-run precision was demonstrated by ≤ 11.8% coefficient of variation. Both compounds proved stable under various conditions. The assay suitability was demonstrated by the application to a clinical study quantifying simultaneously VRC and NO concentrations in plasma, ultrafiltrate and microdialysate. Additionally, the assay was successfully adapted for pharmacokinetic analyses in human tissue-derived in vitro experiments. Overall, by reducing the required sample volume, the bioanalytical method allows for an increased number of plasma samples in vulnerable populations, e.g. infants, and enables the generation of concentration-time profiles with a higher temporal resolution in microdialysis studies. Consequently, the developed assay is apt to elucidate the complex pharmacokinetics of VRC in clinical settings as prerequisite for therapy optimisation.

Influence of Inflammation on Cytochromes P450 Activity in Adults: A Systematic Review of the Literature

Background: Available in-vitro and animal studies indicate that inflammation impacts cytochromes P450 (CYP) activity via multiple and complex transcriptional and post-transcriptional mechanisms, depending on the specific CYP isoforms and the nature of inflammation mediators. It is essential to review the current published data on the impact of inflammation on CYP activities in adults to support drug individualization based on comorbidities and diseases in clinical practice. Methods: This systematic review was conducted in PubMed through 7th January 2021 looking for articles that investigated the consequences of inflammation on CYP activities in adults. Information on the source of inflammation, victim drugs (and CYPs involved), effect of disease-drug interaction, number of subjects, and study design were extracted. Results: The search strategy identified 218 studies and case reports that met our inclusion criteria. These articles were divided into fourteen different sources of inflammation (such as infection, autoimmune diseases, cancer, therapies with immunomodulator…). The impact of inflammation on CYP activities appeared to be isoform-specific and dependent on the nature and severity of the underlying disease causing the inflammation. Some of these drug-disease interactions had a significant influence on drug pharmacokinetic parameters and on clinical management. For example, clozapine levels doubled with signs of toxicity during infections and the concentration ratio between clopidogrel's active metabolite and clopidogrel is 48-fold lower in critically ill patients. Infection and CYP3A were the most cited perpetrator of inflammation and the most studied CYP, respectively. Moreover, some data suggest that resolution of inflammation results in a return to baseline CYP activities. Conclusion: Convincing evidence shows that inflammation is a major factor to be taken into account in drug development and in clinical practice to avoid any efficacy or safety issues because inflammation modulates CYP activities and thus drug pharmacokinetics. The impact is different depending on the CYP isoform and the inflammatory disease considered. Moreover, resolution of inflammation appears to result in a normalization of CYP activity. However, some results are still equivocal and further investigations are thus needed.

Effects of Letermovir and/or Methylprednisolone Coadministration on Voriconazole Pharmacokinetics in Hematopoietic Stem Cell Transplantation: A Population Pharmacokinetic Study

Objective

The aim of this study was to identify factors affecting blood concentrations of voriconazole following letermovir coadministration using population pharmacokinetic (PPK) analysis in allogeneic hematopoietic stem cell transplant (allo-HSCT) recipients.

Methods

The following data were retrospectively collected: voriconazole trough levels, patient characteristics, concomitant drugs, and laboratory information. PPK analysis was performed with NONMEM^® version 7.4.3, using the first-order conditional estimation method with interaction. We collected data on plasma voriconazole steady-state trough concentrations at 216 timepoints for 47 patients. A nonlinear pharmacokinetic model with the Michaelis–Menten equation was applied to describe the relationship between steady-state trough concentration and daily maintenance dose of voriconazole. After stepwise covariate modeling, the final model was evaluated using a goodness-of-fit plot, case deletion diagnostics, and bootstrap methods.

Results

The maximum elimination rate (V_max) of voriconazole in patients coadministered letermovir and methylprednisolone was 1.72 and 1.30 times larger than that in patients not coadministered these drugs, respectively, resulting in decreased voriconazole trough concentrations. The developed PPK model adequately described the voriconazole trough concentration profiles in allo-HSCT recipients. Simulations clearly showed that increased daily doses of voriconazole were required to achieve an optimal trough voriconazole concentration (1–5 mg/L) when patients received voriconazole with letermovir and/or methylprednisolone.

Conclusions

The development of individualized dose adjustment is critical to achieve optimal voriconazole concentration, especially among allo-HSCT recipients receiving concomitant letermovir and/or methylprednisolone.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40268-021-00365-0.

Development and validation of a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantification of voriconazole in human cerebrospinal fluid

Background: A liquid chromatography-tandem mass spectrometry (LC-MS/MS). Method: For the quantification of voriconazole in human cerebrospinal fluid (CSF) was developed and validated, to guide the clinical use of voriconazole in the treatment of central nervous system infections. CSF samples were treated by protein precipitation with methanol containing fluconazole as the internal standard (IS). The supernatant was analyzed by LC-MS/MS using an Agilent EclipsePlus C18 column eluted with a methanol and water mobile phase at a flow rate of 0.4 mL min^-1. Quantification was performed by multiple-reaction monitoring using the precursor and product ion pair 350/280.9 for voriconazole and 307/219.9 for fluconazole. Results: The calibration curve was linear over the range of 0.1-10.0 μg mL^-1 (R² = 0.9991). The inter-day and intra-day precisions were <4.20% and <9.97%, respectively. The recoveries for the three concentrations (0.2, 1.0, and 8.0 μg mL^-1) were 99.96%, 107.00%, and 99.85%, and the matrix effects were 99.35%, 103.41%, and 99.64%, respectively. The stability under various conditions was also acceptable. The study also demonstrated that the CSF matrix could be replaced by plasma and artificial CSF. Conclusion: A simple and accurate method for the determination of voriconazole concentrations in human CSF was developed and validated, which can be used for drug monitoring in the treatment of central nervous system infections.

Voriconazole‐Associated Periostitis: New Insights into Pathophysiology and Management

Voriconazole‐associated periostitis (VAP) is an underrecognized and unpredictable side effect of long‐term voriconazole therapy. We report two cases of VAP occurring in the post‐transplant setting: a 68‐year‐old lung transplant recipient who required ongoing voriconazole therapy, in whom urinary alkalinization was used to promote fluoride excretion and minimize voriconazole‐related skeletal toxicity, and a 68‐year‐old stem‐cell transplant recipient with a high voriconazole dose requirement, identified on pharmacogenomic testing to be a CYP2C19 ultrarapid metabolizer, the dominant enzyme in voriconazole metabolism. This is the first reported case of pharmacogenomic profiling in VAP and may explain the variability in individual susceptibility to this uncommon adverse effect. Our findings provide new insights into both the management and underlying pathophysiology of VAP. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Voriconazole Pharmacokinetics Are Not Altered in Critically Ill Patients with Acute-on-Chronic Liver Failure and Continuous Renal Replacement Therapy: An Observational Study

Infection and sepsis are a main cause of acute-on-chronic liver failure (ACLF). Besides bacteria, molds play a role. Voriconazole (VRC) is recommended but its pharmacokinetics (PK) may be altered by ACLF. Because ACLF patients often suffer from concomitant acute renal failure, we studied the PK of VRC in patients receiving continuous renal replacement therapy (RRT) with ACLF and compared it to PK of VRC in critically ill patients with RRT without concomitant liver failure (NLF). In this prospective cohort study, patients received weight-based VRC. Pre- and post-dialysis membrane, and dialysate samples obtained at different time points were analyzed by high-performance liquid chromatography. An integrated dialysis pharmacometric model was used to model the available PK data. The recommended, 50% lower, and 50% higher doses were analyzed by Monte-Carlo simulation (MCS) for day 1 and at steady-state with a target trough concentration (TC) of 0.5–3mg/L. Fifteen patients were included in this study. Of these, 6 patients suffered from ACLF. A two-compartment model with linear clearance described VRC PK. No difference for central (V1) or peripheral (V2) volumes of distribution or clearance could be demonstrated between the groups. V1 was 80.6L (95% confidence interval: 62.6–104) and V2 106L (65–166) with a body clearance of 4.7L/h (2.87–7.81) and RRT clearance of 1.46L/h (1.29–1.64). MCS showed TC below/within/above target of 10/74/16% on day 1 and 9/39/52% at steady-state for the recommended dose. A 50% lower dose resulted in 26/72/1% (day 1) and 17/64/19% at steady-state and 7/57/37% and 7/27/67% for a 50% higher dose. VRC pharmacokinetics are not significantly influenced by ACLF in critically ill patients who receive RRT. Maintenance dose should be adjusted in both groups. Due to the high interindividual variability, therapeutic drug monitoring seems inevitable.

Concomitant Treatment with Voriconazole and Flucloxacillin: A Combination to Avoid

Background: Voriconazole is an antifungal drug used as one of the first-line treatments for invasive aspergillosis. This drug is extensively metabolized, predominantly via cytochrome P450 enzymes. An interaction between flucloxacillin and voriconazole, leading to subtherapeutic voriconazole concentrations, has previously been reported. We aimed to demonstrate that flucloxacillin independently influences voriconazole exposure. Methods: Patients from three Belgian hospitals, treated with a combination of voriconazole and flucloxacillin, were included in this retrospective study. Voriconazole concentrations were collected both in a timeframe with and without flucloxacillin co-treatment. Multivariate analyses were performed to study the independent effect of flucloxacillin treatment on voriconazole exposure and the possible influence of the flucloxacillin dose. Results: Thirty-three patients were included in this study and 145 trough concentrations (51 with, and 94 without concomitant flucloxacillin treatment) were analyzed. The median (IQR) voriconazole trough concentration sampled during flucloxacillin co-treatment was 0.5 (0–1.8) mg/L, whereas samples without flucloxacillin co-treatment had a median (IQR) voriconazole trough concentration of 3.5 (1.7–5.1) mg/L (p = 0.002), while receiving similar voriconazole doses. Subtherapeutic concentrations (<1 mg/L) were observed in 69% and 7% of the samples with flucloxacillin co-treatment versus samples without flucloxacillin co-treatment, respectively. Conclusion: This study shows that flucloxacillin co-treatment independently decreases voriconazole exposure. Caution is needed when these two drugs are administered simultaneously.

Impact of Inflammation on Cytochromes P450 Activity in Pediatrics: A Systematic Review

Background and Objective

Cytochromes P450 (CYP) are the major enzymes involved in hepatic metabolism of drugs. Personalization of treatment in pediatrics is a major challenge, as it must not only take into account genetic, environmental, and physiological factors but also ontogeny. Published data in adults show that inflammation had an isoform-specific impact on CYP activities and we aimed to evaluate this impact in the pediatric population.

Methods

Articles listed in PubMed through 7 January, 2021 that studied the impact of inflammation on CYP activities in pediatrics were included in this systematic review. Sources of inflammation, victim drugs (CYP involved), effect of drug–disease interactions, number and age of subjects, and study design were extracted.

Results

Twenty-seven studies and case reports were included. The impact of inflammation on CYP activities appeared to be age dependent and isoform-specific, with some drug–disease interactions having significant pharmacokinetic and clinical impact. For example, midazolam clearance decreases by 70%, while immunosuppressant and theophylline concentrations increase three-fold and two-fold with intensive care unit admission and infection. Cytochrome P450 activity appears to return to baseline level when the disease is resolved.

Conclusions

Studies that have assessed the impact of inflammation on CYP activity are lacking in pediatrics, yet it is a major factor to consider to improve drug efficacy or safety. The scarce current data show that the impact of inflammation is isoform and age dependent. An effort must be made to improve the understanding of the impact of inflammation on CYP activities in children to better individualize treatment.

Impact of CYP2C19 genotype on voriconazole exposure and effect of voriconazole on the activity of CYP3A in patients with haematological malignancies

Voriconazole (VRC) is a first-line drug for the treatment of invasive fungal infections (IFIs) and an inhibitor of CYP3A activity. The aims of this study are to investigate the influence of related factors on the plasma concentration of voriconazole and the effect of voriconazole on the activity of CYP3A in patients with haematological malignancies.A total of 89 patients received an initial dose of 6 mg/kg followed by 4 mg/kg every 12 h were included in the study. Blood samples were collected before and 2 h after administration for subsequent testing and for the extraction of DNA samples. Voriconazole and voriconazole N-oxide in the plasma were detected by LC-MS/MS. The effect of voriconazole on CYP3A activity was evaluated by the ratio of the endogenous biomarkers 6β-hydroxycortisol and cortisol.During the study period, the overall incidence of adverse reactions was 33.6% (with no deaths). The metabolite type of CYP2C19 and combined use of CYP2C19 enzyme inhibitors both had a significant impact on voriconazole exposure. Voriconazole has a long-lasting and potent inhibitory effect on CYP3A activity. The exposure of CYP3A substrate in combination with metabolic enzyme inhibitors voriconazole could increase. Therefore, the combination uses with voriconazole need to be considered carefully and assessed adequately.

A Large Retrospective Assessment of Voriconazole Exposure in Patients Treated with Extracorporeal Membrane Oxygenation

BACKGROUND

Voriconazole is one of the first-line therapies for invasive pulmonary aspergillosis. Drug concentrations might be significantly influenced by the use of extracorporeal membrane oxygenation (ECMO). We aimed to assess the effect of ECMO on voriconazole exposure in a large patient population.

METHODS

Critically ill patients from eight centers in four countries treated with voriconazole during ECMO support were included in this retrospective study. Voriconazole concentrations were collected in a period on ECMO and before/after ECMO treatment. Multivariate analyses were performed to evaluate the effect of ECMO on voriconazole exposure and to assess the impact of possible saturation of the circuit's binding sites over time.

RESULTS

Sixty-nine patients and 337 samples (190 during and 147 before/after ECMO) were analyzed. Subtherapeutic concentrations (<2 mg/L) were observed in 56% of the samples during ECMO and 39% without ECMO (p = 0.80). The median trough concentration, for a similar daily dose, was 2.4 (1.2-4.7) mg/L under ECMO and 2.5 (1.4-3.9) mg/L without ECMO (p = 0.58). Extensive inter-and intrasubject variability were observed. Neither ECMO nor squared day of ECMO (saturation) were retained as significant covariates on voriconazole exposure.

CONCLUSIONS

No significant ECMO-effect was observed on voriconazole exposure. A large proportion of patients had voriconazole subtherapeutic concentrations.

Safety, Tolerability, and Population Pharmacokinetics of Intravenous and Oral Isavuconazonium Sulfate in Pediatric Patients

Isavuconazole, administered as the water-soluble prodrug isavuconazonium sulfate, is a new triazole agent used to treat invasive fungal infections. This phase 1 study evaluated the pharmacokinetics (PK), safety, and tolerability of isavuconazole in 46 immunocompromised pediatric patients, stratified by age (1 to <6 [intravenous (i.v.) only], 6 to <12, and 12 to <18 years), receiving 10 mg/kg body weight (maximum, 372 mg) isavuconazonium sulfate either i.v. or orally. A population PK model using weight-based allometric scaling was constructed with the pediatric i.v. and oral data plus i.v. data from a phase 1 study in adults. The best model was a 3-compartment model with combined zero-order and first-order input, with linear elimination. Stepwise covariate modeling was performed in Perl-speaks-NONMEM version 4.7.0. None of the covariates examined, including age, sex, race, and body mass index, were statistically significant for any of the PK parameters. The area under the concentration-time curve at steady state (AUC_SS) was predicted for pediatric patients using 1,000 Monte Carlo simulations per age cohort for each administration route. The probability of target attainment (AUC_SS range, 60 to 233 μg · h/ml) was estimated; this target range was derived from plasma drug exposures in adults receiving the recommended clinical dose. Predicted plasma drug exposures were within the target range for >80% and >76% of simulated pediatric patients following i.v. or oral administration, respectively. Intravenous and oral administration of isavuconazonium sulfate at the studied dosage of 10 mg/kg was well tolerated and resulted in exposure in pediatric patients similar to that in adults. (This study has been registered at ClinicalTrials.gov under identifier NCT03241550).

Clinical and Pharmacological Considerations for Concomitant Administration of Posaconazole and Isavuconazole with Letermovir

We sought in this case-control retrospective study to compare posaconazole and isavuconazole (PCZ and IVC, respectively) plasma trough concentration (C _trough) levels in high-risk allogeneic hematopoietic cell transplant (HCT) recipients who received letermovir (LET) or not. PCZ/IVC C _trough levels were not found to be significantly different between cases and controls, as they were 1.31 mg/liter (median) (interquartile range [IQR], 0.90) versus 1.36 mg/liter (IQR, 1.16) (P = 0.31) and 3.20 mg/liter (IQR, 2.40) versus 2.35 mg/liter (IQR, 1.50) (P = 0.17), respectively. In conclusion, we observed PCZ/IVC C _trough levels within the expected range and no significant effect of LET coadministration.

Application of a Physiologically Based Pharmacokinetic Model to Characterize Time-dependent Metabolism of Voriconazole in Children and Support Dose Optimization

Background: Voriconazole is a potent antifungal drug with complex pharmacokinetics caused by time-dependent inhibition and polymorphisms of metabolizing enzymes. It also exhibits different pharmacokinetic characteristics between adults and children. An understanding of these alterations in pharmacokinetics is essential for pediatric dose optimization. Objective: To determine voriconazole plasma exposure in the pediatric population and further investigate optimal dosage regimens. Methods: An adult and pediatric physiologically based pharmacokinetic (PBPK) model of voriconazole, integrating auto-inhibition of cytochrome P450 3A4 (CYP3A4) and CYP2C19 gene polymorphisms, was developed. The model was evaluated with visual predictive checks and quantitative measures of the predicted/observed ratio of the area under the plasma concentration-time curve (AUC) and maximum concentration (Cmax). The validated pediatric PBPK model was used in simulations to optimize pediatric dosage regimens. The probability of reaching a ratio of free drug (unbound drug concentration) AUC during a 24-h period to minimum inhibitory concentration greater than or equal to 25 (fAUC24h/MIC ≥ 25) was assessed as the pharmacokinetic/pharmacodynamic index. Results: The developed PBPK model well represented voriconazole's pharmacokinetic characteristics in adults; 78% of predicted/observed AUC ratios and 85% of Cmax ratios were within the 1.25-fold range. The model maintained satisfactory prediction performance for intravenous administration in pediatric populations after incorporating developmental changes in anatomy/physiology and metabolic enzymes, with all predicted AUC values within 2-fold and 73% of the predicted Cmax within 1.25-fold of the observed values. The simulation results of the PBPK model suggested that different dosage regimens should be administered to children according to their age, CYP2C19 genotype, and infectious fungal genera. Conclusion: The PBPK model integrating CYP3A4 auto-inhibition and CYP2C19 gene polymorphisms successfully predicted voriconazole pharmacokinetics during intravenous administration in children and could further be used to optimize dose strategies. The infectious fungal genera should be considered in clinical settings, and further research with large sample sizes is required to confirm the current findings.

Metabolic and Pharmaceutical Aspects of Fluorinated Compounds

The applications of fluorine in drug design continue to expand, facilitated by an improved understanding of its effects on physicochemical properties and the development of synthetic methodologies that are providing access to new fluorinated motifs. In turn, studies of fluorinated molecules are providing deeper insights into the effects of fluorine on metabolic pathways, distribution, and disposition. Despite the high strength of the C-F bond, the departure of fluoride from metabolic intermediates can be facile. This reactivity has been leveraged in the design of mechanism-based enzyme inhibitors and has influenced the metabolic fate of fluorinated compounds. In this Perspective, we summarize the literature associated with the metabolism of fluorinated molecules, focusing on examples where the presence of fluorine influences the metabolic profile. These studies have revealed potentially problematic outcomes with some fluorinated motifs and are enhancing our understanding of how fluorine should be deployed.

Effect of proton pump inhibitors on voriconazole concentrations in Chinese patients with malignant hematological diseases

PURPOSE

To evaluate the influence of three proton pump inhibitors (PPIs) on plasma voriconazole (VOR) concentrations and characterize potential drug-drug interactions (DDIs) between VOR and three PPIs (omeprazole, lansoprazole, and pantoprazole) in Chinese patients with malignant hematological diseases.

METHODS

A simple and reliable 2D-HPLC with internal quality control method was used to ensure accurate concentration measurements. A total of 194 patients in this retrospective study were divided into control (N = 59), omeprazole (OME, N = 57), lansoprazole (LAN, N = 26), and pantoprazole (PAN, N = 52) groups for comparison of plasma VOR trough concentrations. To further validate our retrospective analysis of clinical data, we used molecular docking simulation to analyze the binding affinity of PPIs to the cytochrome P450 2C19 (CYP2C19) and cytochrome P450 3A4 (CYP3A4) enzymes that are integral to the metabolism of PPIs and VOR.

RESULTS

Our findings indicated that VOR trough concentrations were significantly higher in patient on PPIs compared with those who were not (P = 0.012). Patients on LAN (P < 0.01) or OME (P < 0.05) had significantly elevated VOR concentrations compared with the control group, whereas those on PAN did not. Although VOR trough concentrations were not significantly elevated with PAN, more patients in the PAN group reached therapeutic VOR concentrations than in any other group.

CONCLUSION

In conclusion, our retrospective data analysis and molecular docking simulations results indicate that LAN and OME interact with VOR via CYP2C19 and CYP3A4 to increase VOR plasma concentrations. This study helps with selection of PPIs in Chinese patients with malignant hematological cancer administered VOR.