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.

Influence of C-reactive protein on the pharmacokinetics of voriconazole in relation to the CYP2C19 genotype: a population pharmacokinetics analysis

Voriconazole is a broad-spectrum triazole antifungal agent. A number of studies have revealed that the impact of C-reactive protein (CRP) on voriconazole pharmacokinetics was associated with the CYP2C19 phenotype. However, the combined effects of CYP2C19 genetic polymorphisms and inflammation on voriconazole pharmacokinetics have not been considered in previous population pharmacokinetic (PPK) studies, especially in the Chinese population. This study aimed to analyze the impact of inflammation on the pharmacokinetics of voriconazole in patients with different CYP2C19 genotypes and optimize the dosage of administration. Data were obtained retrospectively from adult patients aged ≥16 years who received voriconazole for invasive fungal infections from October 2020 to June 2023. Plasma voriconazole levels were measured via high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS). CYP2C19 genotyping was performed using the fluorescence in situ hybridization method. A PPK model was developed using the nonlinear mixed-effect model (NONMEM). The final model was validated using bootstrap, visual predictive check (VPC), and normalized prediction distribution error (NPDE). The Monte Carlo simulation was applied to evaluate and optimize the dosing regimens. A total of 232 voriconazole steady-state trough concentrations from 167 patients were included. A one-compartment model with first order and elimination adequately described the data. The typical clearance (CL) and the volume of distribution (V) of voriconazole were 3.83 L/h and 134 L, respectively. The bioavailability was 96.5%. Covariate analysis indicated that the CL of voriconazole was substantially influenced by age, albumin, gender, CRP, and CYP2C19 genetic variations. The V of voriconazole was significantly associated with body weight. An increase in the CRP concentration significantly decreased voriconazole CL in patients with the CYP2C19 normal metabolizer (NM) and intermediate metabolizer (IM), but it had no significant effect on patients with the CYP2C19 poor metabolizer (PM). The Monte Carlo simulation based on CRP levels indicated that patients with high CRP concentrations required a decreased dose to attain the therapeutic trough concentration and avoid adverse drug reactions in NM and IM patients. These results indicate that CRP affects the pharmacokinetics of voriconazole and is associated with the CYP2C19 phenotype. Clinicians dosing voriconazole should consider the patient's CRP level, especially in CYP2C19 NMs and IMs.

Impact of CYP2C19, CYP2C9, CYP3A4, and FMO3 Genetic Polymorphisms and Sex on the Pharmacokinetics of Voriconazole after Single and Multiple Doses in Healthy Chinese Subjects

Voriconazole is the first-line treatment for invasive aspergillosis. Its pharmacokinetics exhibit considerable inter- and intra-individual variability. The purpose of this study was to investigate the effects of CYP2C19, CYP2C9, CYP3A4, and FMO3 genetic polymorphisms and sex on the pharmacokinetics of voriconazole in healthy Chinese adults receiving single-dose and multiple-dose voriconazole, to provide a reference for its clinical individualized treatment. A total of 123 healthy adults were enrolled in the study, with 108 individuals and 15 individuals in the single-dose and multiple-dose doses, respectively. Plasma voriconazole concentrations were measured using a validated LC-MS/MS method, and pharmacokinetics parameters were calculated using the non-compartmental method with WinNonlin 8.2. CYP2C19, CYP2C9, CYP3A4, and FMO3 single-nucleotide polymorphisms were sequenced using the Illumina Hiseq X-Ten platform. The results suggested that CYP2C19 genetic polymorphisms significantly affected the pharmacokinetics of voriconazole at single doses of 4, 6, and 8 mg/kg and multiple doses of voriconazole. CYP3A4 rs2242480 had a significant effect on AUC0-∞ (area under the plasma concentration-time curve from time 0 to infinity) and MRT (mean residence time) of voriconazole at a single dose of 4 mg/kg in CYP2C19 extensive metabolizer. Regardless of the CYP2C19 genotype, CYP2C9 rs1057910 and FMO3 rs2266780 were not associated with the pharmacokinetics of voriconazole at three single-dose levels or multiple doses. No significant differences in most voriconazole pharmacokinetics parameters were noted between male and female participants after single and multiple dosing. For patients receiving voriconazole treatment, CYP2C19 genetic polymorphisms should be genotyped for its precision administration. In contrast, based on our study of healthy Chinese adults, it seems unnecessary to consider the effects of CYP2C9, CYP3A4, and FMO3 genetic polymorphisms on voriconazole pharmacokinetics.

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.

Mechanism Underlying Conflicting Drug-Drug Interaction Between Aprepitant and Voriconazole via Cytochrome P450 3A4-Mediated Metabolism

Background

Voriconazole is an antifungal drug for which therapeutic monitoring is recommended to prevent side effects. Temporary administration of the antiemetic drug fosaprepitant remarkably decreases the plasma concentration of voriconazole from the therapeutic range. The ratio of the major metabolite voriconazole N-oxide to voriconazole exceeded that at any other time for a patient who started chemotherapy during voriconazole therapy. We attributed this unpredictable result to cytochrome P450 3A4 induced by aprepitant that was converted from fosaprepitant in vivo.

Methods

Concentrations of voriconazole and voriconazole N-oxide were measured using liquid chromatography-mass spectrometry/mass spectrometry in primary human hepatocytes after incubation with aprepitant. Aprepitant suppressed voriconazole N-oxide formation within 24 h, followed by a continuous increase. Levels of drug-metabolizing cytochrome P450 mRNA were measured using real-time PCR in primary human hepatocytes incubated with aprepitant.

Results

Cytochrome P450 3A4 and 2C9 mRNA levels increased ~4- and 2-fold, respectively, over time. Cytochrome P450 3A4 induction was confirmed using reporter assays. We also assessed L-755446, a major metabolite of aprepitant that lacks a triazole ring. Both compounds dose-dependently increased reporter activity; however, induction by L-755446 was stronger than that by aprepitant.

Conclusion

These results indicate that aprepitant initially inhibited voriconazole metabolism via its triazole ring and increased cytochrome P450 3A4 induction following L-755446 formation. The decrease in plasma voriconazole concentration 7 days after fosaprepitant administration was mainly attributed to cytochrome P450 3A4 induction by L-755446.

PBPK modeling to predict the pharmacokinetics of pantoprazole in different CYP2C19 genotypes

Pantoprazole is used to treat gastroesophageal reflux disease (GERD), maintain healing of erosive esophagitis (EE), and control symptoms related to Zollinger-Ellison syndrome (ZES). Pantoprazole is mainly metabolized by cytochrome P450 (CYP) 2C19, converting to 4'-demethyl pantoprazole. CYP2C19 is a genetically polymorphic enzyme, and the genetic polymorphism affects the pharmacokinetics and/or pharmacodynamics of pantoprazole. In this study, we aimed to establish the physiologically based pharmacokinetic (PBPK) model to predict the pharmacokinetics of pantoprazole in populations with various CYP2C19 metabolic activities. A comprehensive investigation of previous reports and drug databases was conducted to collect the clinical pharmacogenomic data, physicochemical data, and disposition properties of pantoprazole, and the collected data were used for model establishment. The model was evaluated by comparing the predicted plasma concentration-time profiles and/or pharmacokinetic parameters (AUC and Cmax) with the clinical observation results. The predicted plasma concentration-time profiles in different CYP2C19 phenotypes properly captured the observed profiles. All fold error values for AUC and Cmax were included in the two-fold range. Consequently, the minimal PBPK model for pantoprazole related to CYP2C19 genetic polymorphism was properly established and it can predict the pharmacokinetics of pantoprazole in different CYP2C19 phenotypes. The present model can broaden the insight into the individualized pharmacotherapy for pantoprazole.

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.

Voriconazole-Induced Hepatotoxicity in a Patient with Pulmonary Aspergillosis: A Case Report

Voriconazole is the therapy of choice for aspergillosis. However, hepatotoxicity is the most common reason for the discontinuation of voriconazole. In contrast, posaconazole is well tolerated, with a low incidence of hepatotoxicity. In most cases, hepatotoxicity is associated with high voriconazole trough concentration influenced mainly by cytochrome P450 (CYP) 2C19 gene polymorphism. Compared with normal metabolizers, intermediate and poor metabolizers generally have higher voriconazole trough concentrations with an increased risk of hepatotoxicity. Here, we describe changes in hepatotoxicity throughout azole therapy in a patient with pulmonary aspergillosis (PA). Nevertheless, the patient with the normal metabolism genotype of CYP2C19 developed severe hepatotoxicity caused by voriconazole but tolerated posaconazole well, with a lack of direct cross-hepatotoxicity between the both. Interestingly, the patient had a high risk of hepatotoxicity at a low voriconazole trough concentration. Fortunately, elevated liver enzymes declined to the baselines with posaconazole treatment.

Efficacy and safety of isavuconazole against deep-seated mycoses: A phase 3, randomized, open-label study in Japan

OBJECTIVES

Isavuconazole is a convenient triazole antifungal agent with a broad antifungal spectrum. A randomized, open-label study (ClinicalTrials.gov, NCT03471988) was conducted to evaluate the efficacy and safety of isavuconazole in Japanese patients with deep-seated mycoses.

PATIENTS AND METHODS

In Cohort A, patients with aspergillosis (chronic pulmonary aspergillosis and invasive aspergillosis) were randomized in a 2:1 ratio to isavuconazole or voriconazole, and in Cohort B, patients with cryptococcosis and mucormycosis were assigned to isavuconazole for up to 84 days of treatment. The overall outcome was evaluated according to the clinical, radiological, and mycological responses at Days 42 and 84 and at the end of treatment (EOT).

RESULTS

A total of 103 participants were enrolled and received the study drug. The overall response rate of patients with chronic pulmonary aspergillosis in the isavuconazole (52 patients) and voriconazole (27 patients) groups was 82.7% and 77.8% at EOT, respectively. The response rate in patients with cryptococcosis (10 patients, isavuconazole group only) was 90.0%. One of three participants with invasive aspergillosis and one of three participants with mucormycosis responded in the isavuconazole group. In the safety evaluation, the incidence of adverse events in participants with chronic pulmonary aspergillosis was similar in both groups. Adverse drug reactions were reported in 32 (61.5%) patients receiving isavuconazole and 23 (85.2%) patients receiving voriconazole.

CONCLUSIONS

Isavuconazole showed efficacy and safety in Japanese patients with chronic pulmonary aspergillosis and cryptococcosis, for which the drug is not currently indicated.

Impact of cytochrome P450 2C19 polymorphisms on the clinical efficacy and safety of voriconazole: an update systematic review and meta-analysis

OBJECTIVE

To assess the impact of cytochrome P450 (CYP) 2C19 polymorphisms on the clinical efficacy and safety of voriconazole.

METHODS

We systematically searched PubMed, EMBASE, CENTRAL, ClinicalTrials.gov, and three Chinese databases from their inception to 18 March 2021 using a predefined search algorithm to identify relevant studies. Studies that reported voriconazole-treated patients and information on CYP2C19 polymorphisms were included. The efficacy outcome was success rate. The safety outcomes included overall adverse events, hepatotoxicity, and neurotoxicity.

RESULTS

A total of 20 studies were included. Intermediate metabolizers (IMs) and poor metabolizers (PMs) were associated with increased success rates compared with normal metabolizers (NMs) [risk ratio (RR), 1.18; 95% confidence interval (CI), 1.03-1.34; I2 = 0%; P = 0.02; RR, 1.28; 95% CI, 1.06-1.54; I2 = 0%; P = 0.01]. PMs were at increased risk of overall adverse events in comparison with NMs and IMs (RR, 2.18; 95% CI, 1.35-3.53; I2 = 0%; P = 0.001; RR, 1.80; 95% CI, 1.23-2.64; I2 = 0%; P = 0.003). PMs demonstrated a trend towards an increased incidence of hepatotoxicity when compared with NMs (RR, 1.60; 95% CI, 0.94-2.74; I2 = 27%; P = 0.08), although there was no statistically significant difference. In addition, there was no significant association between CYP2C19 polymorphisms and neurotoxicity.

CONCLUSION

IMs and PMs were at a significant higher success rate in comparison with NMs. PMs were significantly associated with an increased incidence of all adverse events compared with NMs and IMs. Researches are expected to further confirm these findings. Additionally, the relationship between hepatotoxicity and CYP2C19 polymorphisms deserves clinical attention.

Physiologically based pharmacokinetic modeling of ponatinib to describe drug-drug interactions in patients with cancer

PURPOSE

This study aimed to investigate the drug-drug interactions of ponatinib with strong, moderate, or weak CYP3A4 inhibitors/inducers by developing physiologically based pharmacokinetic (PBPK) models.

METHODS

Simcyp^® Ver 20.1 (Certara Inc., Sheffield, UK) was used to construct a PBPK model for ponatinib and to predict its interaction with strong, moderate, or weak CYP3A4 inhibitors/inducers. The constructed model was validated by comparing predicted values with actual observed values. Inhibitors or inducers that increased or decreased the area under the plasma concentration curve of ponatinib by more than two-fold when used in combination were considered significant.

RESULTS

The PBPK model of ponatinib accurately represented its oral pharmacokinetics. It also reasonably predicted its pharmacokinetics when combined with ketoconazole and rifampicin. No weak to strong CYP3A4 inhibitor combinations significantly increased the AUC of ponatinib. However, the strong CYP3A4 inducers rifampicin (oral, 600 mg QD) and phenytoin (oral, 100 mg TID) decreased AUC by 60-70% and 50%, respectively.

CONCLUSIONS

The PBPK model predicted a significant drug interaction when ponatinib was combined with a strong CYP3A4 inducer. Conversely, the combination with weak-to-strong CYP3A4 inhibitors did not suggest a drug interaction with ponatinib.

Development of Physiology Based Pharmacokinetic Model to Predict the Drug Interactions of Voriconazole and Venetoclax

PURPOSE

Venetoclax (VEN), an anti-tumor drug that is a substrate of cytochrome P450 3A enzyme (CYP3A4), is used to treat leukemia. Voriconazole (VCZ) is an antifungal medication that inhibits CYP3A4. The goal of this study is to predict the effect of VCZ on VEN exposure.

METHOD

Two physiological based pharmacokinetics (PBPK) models were developed for VCZ and VEN using the bottom-up and top-down method. VCZ model was also developed to describe the effect of CYP2C19 polymorphism on its pharmacokinetics (PK). The reversible inhibition constant (Ki) of VCZ for CYP3A4 was calibrated using drug-drug interaction (DDI) data of midazolam and VCZ. The clinical verified VCZ and VEN model were used to predict the DDI of VCZ and VEN at clinical dosing scenario.

RESULT

VCZ model predicted VCZ exposure in the subjects of different CYP2C19 genotype and DDI related fold changes of sensitive CYP3A substrate with acceptable prediction error. VEN model can capture PK of VEN with acceptable prediction error. The DDI PBPK model predicted that VCZ increased the exposure of VEN by 4.5-9.6 fold. The increase in VEN exposure by VCZ was influenced by subject's CYP2C19 genotype. According to the therapeutic window, VEN dose should be reduced to 100 mg when co-administered with VCZ.

CONCLUSION

The PBPK model developed here could support individual dose adjustment of VEN and DDI risk assessment. Predictions using the robust PBPK model confirmed that the 100 mg dose adjustment is still applicable in the presence of VCZ with high inter-individual viability.

The frequency of major CYP2C19 genetic polymorphisms in women of Asian, Native Hawaiian and Pacific Islander subgroups

Aim: Prevalence of clinically actionable genetic variants of CYP2C19 is lacking in specific population subgroups. This study aims to assess the frequencies of CYP2C19*2, *3, and *17 in Asian, Native Hawaiian and Pacific Islander (NHPI) population subgroups compared with Europeans. Patients & methods: The study included repository DNA samples of 1064 women, 18 years or older, who self-reported as Filipino, Korean, Japanese, Native Hawaiian, Marshallese and Samoan. Results: The overall frequencies of CYP2C19*2 (25-36%) and CYP2C19*3 (2.5-10%) were significantly higher in all our subgroups than in Europeans (15 and 0.02%, respectively). The overall frequency of CYP2C19*17 was significantly lower in all our subgroups (1-6%) than in Europeans (21.7%). Conclusion: This is the first report on the frequencies of CYP2C19*2, *3, and *17 in women of Asian and NHPI descent with distinct population subgroup differences. Differential allele frequencies of CYP2C19 among population subgroups underscore the importance of increasing racial and ethnic diversity in pharmacogenetic research.

Effects of CYP2C19, CYP2C9 and CYP3A4 gene polymorphisms on plasma voriconazole levels in Chinese pediatric patients

OBJECTIVES

Voriconazole is the most commonly used antifungal agent in clinical application. Previous studies suggested that voriconazole was extensively metabolized by CYP450 enzyme system, including CYP2C19, CYP2C9 and CYP3A4, which contributed to the individual variability of the pharmacokinetic process of voriconazole. This study aimed to investigate the effects of CYP2C19, CYP2C9 and CYP3A4 gene polymorphisms on plasma voriconazole concentrations in Chinese pediatric patients.

METHODS

This study prospectively evaluated pediatric patients administrating voriconazole for the treatment or prophylaxis of invasive fungal infections from October 2018 to July 2020. Seven single-nucleotide polymorphisms in CYP2C19 (CYP2C19*2, CYP2C19*3, and CYP2C19*17), CYP2C9 (CYP2C9*3, CYP2C9*13) and CYP3A4 (CYP3A4*22, rs4646437) were detected by real-time fluorescent PCR with TaqMan probes. The voriconazole trough plasma concentration was determined by UPLC-MS/MS.

RESULTS

A total of 68 pediatric patients were enrolled in this study. Our results showed that voriconazole plasma concentrations of patients with CYP2C19*2 or CYP2C19*3 allele were significantly higher than that with wild-type carriers (P < 0.0001, P = 0.004, respectively). However, CYP2C9*3 and CYP3A4 rs4646437 were not significantly associated with voriconazole plasma levels. The CYP2C19*17, CYP2C9*13 and CYP3A4*22 alleles were not observed in our study. Additionally, multiple linear regression analysis indicated that CYP2C19*2 and CYP2C19*3 alleles remained predictors of voriconazole plasma concentration (r2 = 0.428; P < 0.0001). For CYP2C19 metabolizer phenotype, trough concentration of voriconazole was significantly lower in NM group compared with IM (P < 0.0001) and PM (P = 0.004) groups.

CONCLUSION

Voriconazole plasma levels in pediatric patients are mainly affected by CYP2C19 gene polymorphisms.

A Large Sample Retrospective Study on the Distinction of Voriconazole Concentration in Asian Patients from Different Clinical Departments

Voriconazole (VRZ) is widely used to prevent and treat invasive fungal infections; however, there are a few studies examining the variability and influencing the factors of VRZ plasma concentrations across different clinical departments. This study aimed to evaluate distinction of VRZ concentrations in different clinical departments and provide a reference for its reasonable use. From 1 May 2014 to 31 December 2020, VRZ standard rates and factors affecting the VRZ trough concentration were analyzed, and a multiple linear regression model was constructed. The standard rates of VRZ in most departments were above 60%. A total of 676 patients with 1212 VRZ trough concentrations using a dosing regimen of 200 mg q12h from seven departments were enrolled in the correlation analysis. The concentration distribution varied significantly among different departments (p < 0.001). Fifteen factors, including department, CYP2C19 phenotype, and gender, correlated with VRZ concentration. A multiple linear regression model was established as follows: VRZ trough concentration = 5.195 + 0.049 × age + 0.007 × alanine aminotransferase + 0.010 × total bilirubin − 0.100 × albumin − 0.004 × gamma-glutamyl transferase. According to these indexes, we can predict possible changes in VRZ trough concentration and adjust its dosage precisely and individually.

Experience of a Strategy Including CYP2C19 Preemptive Genotyping Followed by Therapeutic Drug Monitoring of Voriconazole in Patients Undergoing Allogenic Hematopoietic Stem Cell Transplantation

Many factors have been described to contribute to voriconazole (VCZ) interpatient variability in plasma concentrations, especially CYP2C19 genetic variability. In 2014, Hicks et al. presented data describing the correlation between VCZ plasma concentrations and CYP2C19 diplotypes in immunocompromised pediatric patients and utilized pharmacokinetic modeling to extrapolate a more suitable VCZ dose for each CYP2C19 diplotype. In 2017, in our hospital, a clinical protocol was developed for individualization of VCZ in immunocompromised patients based on preemptive genotyping of CYP2C19 and dosing proposed by Hicks et al., Clinical Pharmacogenetics Implementation Consortium (CPIC) clinical guidelines, and routine therapeutic drug monitoring (TDM). We made a retrospective review of a cohort of 28 immunocompromised pediatric patients receiving VCZ according to our protocol. CYP2C19 gene molecular analysis was preemptively performed using PharmArray^®. Plasma trough concentrations were measured by immunoassay analysis until target concentrations (1–5.5 μg/ml) were reached. Sixteen patients (57.14%) achieved VCZ trough target concentrations in the first measure after the initial dose based on PGx. This figure is similar to estimations made by Hicks et al. in their simulation (60%). Subdividing by phenotype, our genotyping and TDM-combined strategy allow us to achieve target concentrations during treatment/prophylaxis in 90% of the CYP2C19 Normal Metabolizers (NM)/Intermediate Metabolizers (IM) and 100% of the Rapid Metabolizers (RM) and Ultrarapid Metabolizers (UM) of our cohort. We recommended modifications of the initial dose in 29% (n = 8) of the patients. In RM ≥12 years old, an increase of the initial dose resulted in 50% of these patients achieving target concentrations in the first measure after initial dose adjustment based only on PGx information. Our experience highlights the need to improve VCZ dose predictions in children and the potential of preemptive genotyping and TDM to this aim. We are conducting a multicenter, randomized clinical trial in patients with risk of aspergillosis in order to evaluate the effectiveness and efficiency of VCZ individualization: VORIGENIPHARM (EudraCT: 2019-000376-41).

The necessary conduct: Exploratory multiregional clinical trials in East Asia

Various studies have highlighted the importance of ethnic differences. The consideration of ethnic differences in the field of individualized pharmacotherapy is imperative. Therefore, various organizations and networks across countries should aim to conduct multicountry and multiregional clinical trials (MRCTs). If there is solid evidence available to evaluate the existence of ethnic differences between the same regional areas, it will lead to an increase in the efficiency of drug development. The purpose of this paper was to compare the approval dosing regimen among four Asian countries (Korea, Japan, China, and Taiwan) and elucidate the readiness and current status of the implementation of the International Conference on Harmonization (ICH) E17 guidelines on MRCTs. Reducing unnecessary clinical trials via multinational clinical trials in East Asian countries is also suggested. The approved dosing regimens for some drugs in the four Asian countries were similar; however, some differences might be caused by differences in legislation, even though there were no ethnic differences. This indicates that there are several roles to be expected of the Asia Clinical Pharmacology study network for exploratory MRCTs, which would lead to the accumulation of evidence for MRCTs, ultimately accelerating the efficiency of drug development in East Asian countries. The exposure of the new treatment to the necessary patients through collaborative research coordination and simultaneous multinational subject recruitment would serve its role in providing East Asia with specific personalized medicine with a high treatment success rate.

Population pharmacokinetic model-guided optimization of intravenous voriconazole dosing regimens in critically ill patients with liver dysfunction

STUDY OBJECTIVES

This study aimed to establish a population pharmacokinetic (PPK) model of intravenous voriconazole (VRC) in critically ill patients with liver dysfunction and to explore the optimal dosing strategies in specific clinical scenarios for invasive fungal infections (IFIs) caused by common Aspergillus and Candida species.

DESIGN

Prospective pharmacokinetics study.

SETTING

The intensive care unit in a tertiary-care medical center.

PATIENTS

A total of 297 plasma VRC concentrations from 26 critically ill patients with liver dysfunction were included in the PPK analysis.

METHODS

Model-based simulations with therapeutic range of 2-6 mg/L as the plasma trough concentration (C_min ) target and the free area under the concentration-time curve from 0 to 24 h (ƒAUC₂₄ ) divided by the minimum inhibitory concentration (MIC) (ie, ƒAUC₂₄ /MIC) ≥25 as the effective target were performed to optimize VRC dosing regimens for Child-Pugh class A and B (CP-A/B) and Child-Pugh class C (CP-C) patients.

RESULTS

A two-compartment model with first-order elimination adequately described the data. Significant covariates in the final model were body weight on both central and peripheral distribution volume and Child-Pugh class on clearance. Intravenous VRC loading dose of 5 mg/kg every 12 h (q12h) for the first day was adequate for CP-A/B and CP-C patients to attain the C_min target at 24 h. The maintenance dose regimens of 100 mg q12h or 200 mg q24h for CP-A/B patients and 50 mg q12h or 100 mg q24h for CP-C patients could obtain the probability of effective target attainment of >90% at an MIC ≤0.5 mg/L and achieve the cumulative fraction of response of >90% against C. albicans, C. parapsilosis, C. glabrata, C. krusei, A. fumigatus, and A. flavus. Additionally, the daily VRC doses could be increased by 50 mg for CP-A/B and CP-C patients at an MIC of 1 mg/L, with plasma C_min monitored closely to avoid serious adverse events. It is recommended that an appropriate alternative antifungal agent or a combination therapy could be adopted when an MIC ≥2 mg/L is reported, or when the infection is caused by C. tropicalis but the MIC value is not available.

CONCLUSIONS

For critically ill patients with liver dysfunction, the loading dose of intravenous VRC should be reduced to 5 mg/kg q12h. Additionally, based on the types of fungal pathogens and their susceptibility to VRC, the adjusted maintenance dose regimens with lower doses or longer dosing intervals should be considered for CP-A/B and CP-C patients.

Model-Oriented Dose Optimization of Voriconazole in Critically Ill Children

This study aimed to employ a population pharmacokinetic (PK) model to optimize the dosing regimen of voriconazole (VRC) in children with a critical illness. A total of 99 children aged from 0.44 to 13.58 years were included in this study. The stability and predictive performance of the final model were evaluated by statistical and graphical methods. The optimal dosing regimen was proposed for children with different body weights, CYP2C19 phenotypes, and coadministrations with omeprazole. The PK of VRC was described by a two-compartment model with nonlinear Michaelis-Menten elimination. Body weight, CYP2C19 phenotype, and omeprazole were significant covariates on the maximum velocity of elimination (V_max), which had an estimated typical value of 18.13 mg · h^-1. Bayesian estimation suggested that the dose-normalized concentration and total exposure (peak concentration [C_max]/D, trough concentration [C_min]/D, and area under the concentration-time curve over 24 h [AUC₂₄]/D) were significantly different between extensive metabolizer (EM) patients and poor metabolizer (PM) patients. To achieve the target concentration early, two loading doses of 9 mg · kg^-1 of body weight every 12 h (q12h) were reliable for most children, whereas three loading doses of 6 to 7.5 mg · kg^-1 q8h were warranted for young children weighing ≤18 kg (except for PM patients). The maintenance doses decreased about 30 to 40% in PM patients compared to that in EM patients. For children aged <2 years, in EM patients, the maintenance dose could be as high as 9 mg · kg^-1. The maintenance dose of VRC was supposed to decrease slightly when coadministered with omeprazole. A population PK model of intravenous VRC for critically ill children has been successfully developed. It is necessary to adjust dosing regimens according to the CYP2C19 genotype. Optimal dosing regimens have been recommended based on the final model.

CYP2C19 Phenotype and Body Weight-Guided Voriconazole Initial Dose in Infants and Children after Hematopoietic Cell Transplantation

Prophylactic voriconazole use is recommended for children undergoing hematopoietic cell transplantation (HCT). Dosing considerations are essential, due to the narrow therapeutic window of voriconazole. Known covariates do not sufficiently explain the large interindividual pharmacokinetic (PK) variability of voriconazole. Moreover, knowledge of voriconazole PK for age <2 years is limited. We investigated genetic and clinical covariate associations with voriconazole interindividual PK variability and subsequently simulated dosing regimens in children. This study was conducted as part of a single-institution, phase I study of intravenous voriconazole therapy for children undergoing HCT. We conducted a population PK analysis and tested covariate effects on voriconazole PK, including 67 genetic variants and clinical variables. We analyzed plasma voriconazole and N-oxide metabolite concentrations from 58 children <21 years of age (including 12 children <2 years of age). A two-compartment parent mixed linear/nonlinear model best described our data. The CYP2C19 phenotype and body weight were significant covariates (P < 0.05 for both). Our model performance for age <2 years was comparable to that for other age groups. Simulation of the final model suggested the following doses to attain target steady-state trough concentrations of 1.5 to 5.0 mg/liter for the CYP2C19 normal phenotype: 16 mg/kg (weight of <15 kg), 12 mg/kg (weight of 15 to 30 kg), or 10 mg/kg (weight of >30 kg); doses were 33 to 50% lower for CYP2C19 poor/intermediate phenotypes and 25 to 50% higher for CYP2C19 rapid/ultrarapid phenotypes. We propose a new starting-dose regimen, combined with therapeutic drug monitoring, for intravenous voriconazole therapy in children of all ages. Future studies should validate this dosing regimen.

The influence of CYP2C19 polymorphisms on voriconazole trough concentrations: Systematic review and meta-analysis

BACKGROUND

Voriconazole primary metabolism is catalysed by CYP2C19. A large variability of trough concentrations in patients with invasive fungal infection treated with voriconazole has been observed in clinical practice. It remains controversial whether the CYP2C19 polymorphisms are responsible for voriconazole metabolism in the individual variation.

OBJECTIVES

The primary aim of this study was to assess the effect of CYP2C19 polymorphisms on voriconazole trough concentrations.

METHODS

Following a systematic literature review, we performed a meta-analysis for mean differences (MD) of voriconazole trough concentrations (C_min ), voriconazole dosage adjusted trough concentrations (C_min /D) and for risk ratio (RR) of the proportion of patients in the target therapeutic range between pairwise comparisons of CYP2C19 phenotypes.

RESULTS

Compared with normal metabolisers (NMs), intermediate metabolisers (IMs) (MD: 0.82, 95% CI: 0.57 to 1.07, I²  = 44%, p < .00001) or poor metabolisers (PMs) (MD: 1.59, 95% CI: 1.14 to 2.05, I²  = 46%, p < .00001) had significantly higher voriconazole C_min (μg·ml^-1 ), while rapid metabolisers (RMs) had significantly lower voriconazole C_min (MD: -0,87, 95% CI: -1.35 to -0.38, I²  = 0%, p = .0004). In addition, IMs had significantly lower C_min than PMs (MD: -0.59, 95% CI: -0.97 to -0.20, I²  = 22%, p = .003). Similarly, the C_min /D (μg·kg·ml^-1 ·mg^-1 ) was significantly higher in IMs (MD: 0.13, 95% CI: 0.05 to 0.22, I²  = 0%, p = .002) and PMs (MD: 0.20, 95% CI: 0.07 to 0.34, I²  = 0%, p = .003) than that in NMs, and also, IMs had significantly lower C_min /D than PMs (MD: -0.11, 95% CI: -0.14 to -0.08, I²  = 0%, p < .00001). Furthermore, PMs had a significantly higher proportion of the target therapeutic range than NMs (RR: 1.34, 95% CI: 1.09 to 1.64, I²  = 50%, p = .005).

CONCLUSIONS

Compared to NMs, IMs and PMs had higher voriconazole trough concentrations, especially in Asians, while RMs had lower voriconazole trough concentrations. In addition, PMs had a higher proportion of the target therapeutic range than NMs, especially in Asians. CYP2C19 genotyping is expected to be used to preemptively guide the individualisation of voriconazole in clinical practice.

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.

Review of Pharmacologic Considerations in the Use of Azole Antifungals in Lung Transplant Recipients

Mold-active azole antifungals are commonly prescribed for the prevention of invasive fungal infections in lung transplant recipients. Each agent exhibits a unique pharmacologic profile, an understanding of which is crucial for therapy selection and optimization. This article reviews pharmacologic considerations for three frequently-used azole antifungals in lung transplant recipients: voriconazole, posaconazole, and isavuconazole. Focus is drawn to analysis of drug-interactions, adverse drug reactions, pharmacokinetic considerations, and the role of therapeutic drug monitoring with special emphasis on data from the post-lung transplant population.

Predictors of Adverse Events and Determinants of the Voriconazole Trough Concentration in Kidney Transplantation Recipients

Voriconazole is the mainstay for the treatment of invasive fungal infections in patients who underwent a kidney transplant. Variant CYP2C19 alleles, hepatic function, and concomitant medications are directly involved in the metabolism of voriconazole. However, the drug is also associated with numerous adverse events. The purpose of this study was to identify predictors of adverse events using binary logistic regression and to measure its trough concentration using multiple linear modeling. We conducted a prospective analysis of 93 kidney recipients cotreated with voriconazole and recorded 213 trough concentrations of it. Predictors of the adverse events were voriconazole trough concentration with the odds ratios (OR) of 2.614 (P = 0.016), cytochrome P450 2C19 (CYP2C19), and hemoglobin (OR 0.181, P = 0.005). The predictive power of these three factors was 91.30%. We also found that CYP2C19 phenotypes, hemoglobin, platelet count, and concomitant use of ilaprazole had quantitative relationships with voriconazole trough concentration. The fit coefficient of this regression equation was R²  = 0.336, demonstrating that the model explained 33.60% of interindividual variability in the disposition of voriconazole. In conclusion, predictors of adverse events are CYP2C19 phenotypes, hemoglobin, and voriconazole trough concentration. Determinants of the voriconazole trough concentration were CYP2C19 phenotypes, platelet count, hemoglobin, concomitant use of ilaprazole. If we consider these factors during voriconazole use, we are likely to maximize the treatment effect and minimize adverse events.

Population pharmacokinetics, safety and dosing optimization of voriconazole in patients with liver dysfunction: A prospective observational study

AIMS

Voriconazole is a broad-spectrum antifungal agent for the treatment of invasive fungal infections. There is limited information about the pharmacokinetics and appropriate dosage of voriconazole in patients with liver dysfunction. This study aimed to explore the relationship between voriconazole trough concentration (C_trough ) and toxicity, identify the factors significantly associated with voriconazole pharmacokinetic parameters and propose an optimised voriconazole dosing regimen for patients with liver dysfunction.

METHODS

The study prospectively enrolled 51 patients with 272 voriconazole concentrations. Receiver operating characteristic curves were used to explore the relationship between voriconazole C_trough and toxicity. The pharmacokinetic data was analysed with nonlinear mixed-effects method. Dosing simulations stratified by total bilirubin (TBIL, TBIL-1: TBIL < 51 μmol/L; TBIL-2: 51 μmol/L ≤ TBIL < 171 μmol/L; TBIL-3: TBIL ≥ 171 μmol/L) were performed.

RESULTS

Receiver operating characteristic curve analysis revealed that voriconazole C_trough of ≤ 5.1 mg/L were associated with significantly lower the incidence of adverse events. A 1-compartment pharmacokinetic model with first-order absorption and elimination was used to describe the data. Population pharmacokinetic parameters of clearance, volume of distribution and oral bioavailability were 0.88 L/h, 148.8 L and 88.4%, respectively. Voriconazole clearance was significantly associated with TBIL and platelet count. The volume of distribution increased with body weight. Patients with TBIL-1 could be treated with a loading dose of 400 mg every 12 hours (q12h) for first day, followed by a maintenance dose of 100 mg q12h administered orally or intravenously. TBIL-2 and TBIL-3 patients could be treated with a loading dose of 200 mg q12h and maintenance doses of 50 mg q12h or 100 mg once daily and 50 mg once daily orally or intravenously, respectively.

CONCLUSIONS

Lower doses and longer dosing intervals should be considered for patients with liver dysfunction. TBIL-based dosing regimens provide a practical strategy for achieving voriconazole therapeutic range and therefore maximizing treatment outcomes.

Effect of CYP2C19 polymorphism on the plasma voriconazole concentration and voriconazole-to-voriconazole-N-oxide concentration ratio in elderly patients

BACKGROUND

Effects of CYP2C19 polymorphism on voriconazole concentration (C0 ), dose-adjusted trough concentrations (C0 /dose) and voriconazole-to-voriconazole-N-oxide concentration ratio (C0 /CN ) have not been fully investigated.

OBJECTIVES

To investigate correlations of CYP2C19 polymorphisms with plasma concentrations of voriconazole and the major metabolite voriconazole-N-oxide in elderly patients.

METHODS

A prospective, multi-centre, non-intervention, open clinical study was conducted within Southwestern Chinese patients clinically diagnosed with invasive fungal infections, to investigate the associations of CYP2C19∗2 (681G > A), CYP2C19∗3 (636G > A) and CYP2C19∗17 (-806C > T) genetic polymorphisms with voriconazole C0 , C0 /dose and C0 /CN .

RESULTS

The study included 131 adult patients, of which 72 were elderly (≥60 years) and 59 were adults (<60 years). The allele frequencies of CYP2C19∗2, ∗3 and ∗17 in the elderly cohort were 61.1%, 29.9% and 7.6%, respectively, which were similar to those in the adult cohort (66.9%, 29.7% and 2.5%, respectively; P > .05). The median voriconazole C0 (C0 ), C0 /dose and C0 /CN ratio in patients with the CYP2C19∗1/∗2 and CYP2C19∗2/∗2 genotypes were significantly higher than those in patients with the CYP2C19∗1/∗1 genotype in the adult cohort (P < .05). The C0 and C0 /dose in patients with the CYP2C19∗1/∗3 and CYP2C19∗2/∗2 genotypes, and the C0 /CN ratio for patients with the CYP2C19∗1/∗2 genotype were numerically higher than those in patients with the CYP2C19∗1/∗1 genotype in the elderly cohort, but this difference was not statistically significant (P > 0.05). The C0 , C0 /dose and C0 /CN in patients with poor metaboliser phenotypes were higher than in those with normal metaboliser phenotypes and C0 in patients with intermediate metaboliser phenotypes were significantly higher than in those with normal metaboliser phenotypes in the adult cohort (P < .05). However, there were no significant differences in the C0 , C0 /dose and C0 /CN among different CYP2C19-predicted metabolic phenotypes in the elderly cohort.

CONCLUSIONS

Voriconazole C0 , C0 /dose and C0 /CN ratio are not significantly affected by the CYP2C19∗2/∗3 polymorphisms in the elderly patients.

Effect of Therapeutic Drug Monitoring and Cytochrome P450 2C19 Genotyping on Clinical Outcomes of Voriconazole: A Systematic Review

Objectives

To examine current knowledge on the clinical utility of therapeutic drug monitoring (TDM) in voriconazole therapy, the impact of CYP2C19 genotype on voriconazole plasma concentrations, and the role of CYP2C19 genotyping in voriconazole therapy.

Data Sources

Three literature searches were conducted for original reports on (1) TDM and voriconazole outcomes and (2) voriconazole and CYP2C19 polymorphisms. Searches were conducted through EMBASE, MEDLINE/PubMed, Scopus, and Cochrane Central Register of Controlled Trials from inception to June 2020.

Study Selection and Data Extraction

Randomized controlled trials, cohort studies, and case series with ≥10 patients were included. Only full-text references in English were eligible.

Data Synthesis

A total of 63 studies were reviewed. TDM was recommended because of established concentration and efficacy/toxicity relationships. Voriconazole trough concentrations ≥1.0 mg/L were associated with treatment success; supratherapeutic concentrations were associated with increased neurotoxicity; and hepatotoxicity associations were more prevalent in Asian populations. CYP2C19 polymorphisms significantly affect voriconazole metabolism, but no relationship with efficacy/safety were found. Genotype-guided dosing with TDM was reported to increase chances of achieving therapeutic range.

Relevance to Patient Care and Clinical Practice

Genotype-guided dosing with TDM is a potential solution to optimizing voriconazole efficacy while avoiding treatment failures and common toxicities.

Conclusions

Voriconazole plasma concentrations and TDM are treatment outcome predictors, but research is needed to form a consensus target therapeutic range and dosage adjustment guidelines based on plasma concentrations. CYP2C19 polymorphisms are a predictor of voriconazole concentrations and metabolism, but clinical implications are not established. Large-scale, high-methodological-quality trials are required to investigate the role for prospective genotyping and establish CYP2C19-guided voriconazole dosing recommendations.

Saliva for Precision Dosing of Antifungal Drugs: Saliva Population PK Model for Voriconazole Based on a Systematic Review

Precision dosing for many antifungal drugs is now recommended. Saliva sampling is considered as a non-invasive alternative to plasma sampling for therapeutic drug monitoring (TDM). However, there are currently no clinically validated saliva models available. The aim of this study is firstly, to conduct a systematic review to evaluate the evidence supporting saliva-based TDM for azoles, echinocandins, amphotericin B, and flucytosine. The second aim is to develop a saliva population pharmacokinetic (PK) model for eligible drugs, based on the evidence. Databases were searched up to July 2019 on PubMed® and Embase®, and 14 studies were included in the systematic review for fluconazole, voriconazole, itraconazole, and ketoconazole. No studies were identified for isavuconazole, posaconazole, flucytosine, amphotericin B, caspofungin, micafungin, or anidulafungin. Fluconazole and voriconazole demonstrated a good saliva penetration with an average S/P ratio of 1.21 (± 0.31) for fluconazole and 0.56 (± 0.18) for voriconazole, both with strong correlation (r = 0.89-0.98). Based on the evidence for TDM and available data, population PK analysis was performed on voriconazole using Nonlinear Mixed Effects Modeling (NONMEM 7.4). 137 voriconazole plasma and saliva concentrations from 11 patients (10 adults, 1 child) were obtained from the authors of the included study. Voriconazole pharmacokinetics was best described by one-compartment PK model with first-order absorption, parameterized by clearance of 4.56 L/h (36.9% CV), volume of distribution of 60.7 L, absorption rate constant of 0.858 (fixed), and bioavailability of 0.849. Kinetics of the voriconazole distribution from plasma to saliva was identical to the plasma kinetics, but the extent of distribution was lower, modeled by a scale factor of 0.5 (4% CV). A proportional error model best accounted for the residual variability. The visual and simulation-based model diagnostics confirmed a good predictive performance of the saliva model. The developed saliva model provides a promising framework to facilitate saliva-based precision dosing of voriconazole.

Pharmacokinetics and Safety of Two Voriconazole Formulations after Intravenous Infusion in Healthy Korean Volunteers

Background

Voriconazole, a triazole antifungal agent exhibits broad-spectrum antifungal activity. It is used to treat severe, invasive fungal infections, including invasive aspergillosis and candidemia. The aim of this study was to assess the pharmacokinetic equivalence of a test formulation (Vorico^® Injection) and reference formulation (Vfend^® IV) of voriconazole.

Materials and Methods

This was a randomized, open-label, single-dose, three-group, two-treatment, two-sequence, two-period, crossover phase I trial with 7-day washout periods (ClinicalTrials.gov identifier NCT02631954). Twenty-four healthy Korean male subjects were recruited. In each group, eight subjects were randomized in a 1:1 manner to receive a single dose of 200 mg test or reference formulation intravenously over 1.5 h. Blood samples were collected over 24 h post-dose, and plasma drug concentrations were determined by liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters were determined using a non-compartmental analysis, and safety was evaluated.

Results

Twenty-three subjects completed the study. The geometric mean ratio (90% confidence interval) of the test formulation to reference formulation was 0.9570 (0.8178 – 1.1199) for the maximum plasma concentration (C_max) and 1.0720 (1.0262 – 1.1198) for the area under the concentration–time curve from dosing to the last quantifiable concentration (AUC_last). The mean plasma concentration–time profiles, pharmacokinetic parameters, and safety were comparable between the two formulations.

Conclusion

Equivalent pharmacokinetic characteristics that satisfied the criteria of bioequivalence and similar safety profiles were observed for both test and reference formulations of voriconazole.

Oral absorption of voriconazole is affected by SLCO2B1 c.*396T>C genetic polymorphism in CYP2C19 poor metabolizers

High pharmacokinetic variability of voriconazole is mainly explained by CYP2C19 phenotype, but there are still unknown factors affecting the variability. In this study, the effect of solute carrier organic anion transporter family member 2B1 (SLCO2B1) genotype on the pharmacokinetics (PKs) of voriconazole was evaluated in 12 healthy CYP2C19 poor metabolizers after a single administration of voriconazole 200 mg intravenously and orally. In addition, the influence of CYP3A4 enzyme activity was also explored. The oral absorption of voriconazole was decreased and delayed in the subjects with the SLCO2B1 c.*396T>C variant compared to the subjects with wild type. However, the CYP3A activity markers measured in this study did not show significant association with metabolism of voriconazole. The results suggest that the SLCO2B1 c.*396T>C may be associated with the decreased function of intestinal OATP2B1, and it could contribute to interindividual PK variability of voriconazole.

Pharmacokinetics of intravenous voriconazole in patients with liver dysfunction: A prospective study in the intensive care unit

OBJECTIVES

To characterize the pharmacokinetics (PK) of intravenous voriconazole (VRC) in critically ill patients with liver dysfunction.

METHODS

Patients with liver dysfunction in the intensive care unit (ICU) were included prospectively. The Child-Pugh score was used to categorize the degree of liver dysfunction. The initial intravenous VRC dosing regimen comprised a loading dose of 300 mg every 12 h for the first 24 h, followed by 200 mg every 12 h. The first PK curves (PK curve 1) were drawn within one dosing interval of the first dose for 17 patients; the second PK curves (PK curve 2) were drawn within one dosing interval after a minimum of seven doses for 12 patients. PK parameters were estimated by non-compartmental analysis.

RESULTS

There were good correlations between the area under the curve (AUC_0-12) of PK curve 2 and the corresponding trough concentration (C₀) and peak concentration (C_max) (r² = 0.951 and 0.963, respectively; both p < 0.001). The median half-life (t_1/2) and clearance (CL) of patients in Child-Pugh class A (n = 3), B (n = 5), and C (n = 4) of PK curve 2 were 24.4 h and 3.31 l/h, 29.1 h and 2.54 l/h, and 60.7 h and 2.04 l/h, respectively. In the different Child-Pugh classes, the CL (median) of PK curve 2 were all lower than those of PK curve 1. The apparent steady-state volume of distribution (V_ss) of PK curve 1 was positively correlated with actual body weight (r² = 0.450, p = 0.004). The median first C₀ of 17 patients determined on day 5 was 5.27 (2.61) μg/ml, and 29.4% of C₀ exceeded the upper limit of the therapeutic window (2-6 μg/ml).

CONCLUSIONS

The CL of VRC decreased with increasing severity of liver dysfunction according to the Child-Pugh classification, along with an increased t_1/2, which resulted in high plasma exposure of VRC. Adjusted dosing regimens of intravenous VRC should be established based on Child-Pugh classes for these ICU patients, and plasma concentrations should be monitored closely to avoid serious adverse events.

A phase I dose finding study of intravenous voriconazole in pediatric patients undergoing hematopoietic cell transplantation

To optimize voriconazole dosing in pediatric hematopoietic cell transplantation (HCT), we conducted a phase I study with a modified 3 + 3 dose-escalation followed by an expansion cohort at the maximum tolerated, minimum efficacious dose (MTD/MED). Patients ≤21 years who required voriconazole for prevention or treatment of an invasive fungal infection were assigned to three age groups. Of the 59 evaluable patients, 13 were <2 years, 23 were 2-11, and 23 were 12-21. Therapeutic serum voriconazole troughs (1.5-5 µg/mL) drawn at 7 days after initiation determined efficacy. The MTD/MED was 12 mg/kg/dose q12 h × 2 loading doses, then 10 mg/kg/dose q12 h in patients <2, and was 10 mg/kg/dose q12 h in patients 2-11. The 12-21 age group had no dose-limiting toxicity at 8 mg/kg/dose q12 h; however, the MED was not reached. Drug-related AEs ≥grade 3 included increased bilirubin, transaminases, and creatinine, all occurring in <10%. There was no significant association between supra-therapeutic troughs and AEs. Five of 17 patients who had supra-therapeutic troughs (29%) had an AE, compared to 8 of 42 who did not (19%, p = 0.38). Observational population pharmacokinetic analysis demonstrated that inter-individual variability on voriconazole clearance was >100% CV, and clearance increased with age.

Population Pharmacokinetics of Voriconazole and Optimization of Dosage Regimens Based on Monte Carlo Simulation in Patients With Liver Cirrhosis

Because voriconazole metabolism is highly influenced by liver function, the dose regimen of voriconazole should be carefully assessed in patients with liver cirrhosis. We aimed to identify significant factors associated with plasma concentrations. Blood samples were collected from patients with liver cirrhosis who received voriconazole, and voriconazole concentrations were determined. One-compartment model with first-order absorption and elimination appropriately characterized the in vivo process of voriconazole. The typical population value of voriconazole clearance (CL) was 1.45 L/h and the volume of distribution (V) was 132.12 L. The covariate analysis identified that CYP2C19 gene phenotype and Child-Pugh classification were strongly associated with CL and body weight had a significant influence on V. The results of the Monte Carlo simulation suggested that CYP2C19 gene phenotype was a critical factor for determining voriconazole dosage in patients with liver cirrhosis. The extensive metabolizer patients with Aspergillus fumigatus infections could be treated effectively with a recommended dose of 75 mg twice daily in mild to moderate liver cirrhosis and 100 mg once daily in moderate severe liver cirrhosis. However, the recommended dosage for Candida albicans infections patients was not achieved in present study.

Model-based Voriconazole Dose Optimization in Chinese Adult Patients With Hematologic Malignancies

PURPOSE

The objective of this study was to characterize the population pharmacokinetics of voriconazole and to identify factors that significantly affect pharmacokinetic parameters and to further investigate optimal dosage regimens in Chinese adult patients with hematologic malignancies.

METHODS

A prospective population pharmacokinetic analysis was performed on 186 concentration measurements obtained from 41 adult patients with hematologic malignancies. All enrolled patients were treated with voriconazole for diagnosed or suspected invasive fungal diseases. Oral voriconazole was routinely administered at a maintenance dose of 200 mg q12h. Serial blood samples were collected after steady-state of each patient. Monte Carlo simulation was applied to optimize dosage strategies.

FINDINGS

A one-compartment model with first-order absorption and elimination adequately described the data. The typical voriconazole clearance was 4.18 L/h, the volume of distribution was 88.9 L, and the absorption rate constant was 0.729 h^-1. Clearance and steady-state exposure (AUC_0-12) were found to be significantly associated with age and CYP2C19 phenotype. The average AUC_0-12 of elderly patients (aged 60-90 years) was 2.1 times higher than that of relative younger patients (aged 18-59 years). The average AUC_0-12 of poor metabolizers (PMs) was approximately 2.5 and 1.8 times higher than that of extensive and intermediate metabolizers (IMs), respectively. Considering both efficacy and tolerability, dosage regimens of 100 and 50 mg orally administered every 12 hours were recommended for elderly IMs and PMs, respectively.

IMPLICATIONS

A population pharmacokinetic model for voriconazole in Chinese adult patients with hematologic malignancies was successfully developed and could well capture voriconazole's pharmacokinetic characteristics. Age and CYP2C19 phenotype were found to significantly influence voriconazole clearance and should be taken into consideration clinically for dose optimization. The optimal dosage strategies in specific clinical scenarios were proposed in this study based on model simulation. Because of the high incidence of mutant CYP2C19*2 and *3 alleles, genetic testing seems to be necessary for Asian elderly patients when voriconazole treatment is initiated.

Interpersonal Factors in the Pharmacokinetics and Pharmacodynamics of Voriconazole: Are CYP2C19 Genotypes Enough for Us to Make a Clinical Decision?

Background:

Invasive mycoses are serious infections with high mortality and increasing inci-dence. Voriconazole, an important drug to treat invasive mycosis, is metabolized mainly by the cytochrome P450 family 2 subfamily C member 19 enzyme (CYP2C19) and is affected by the genotypes of CYP2C19.

Objective:

We reviewed studies on how genotypes affect the pharmacokinetics and pharmacodynamics of voriconazole, and attempted to determine a method to decide on dosage adjustments based on genotypes, after which, the main characteristic of voriconazole was clarified in details. The pharmacokinetics of voriconazole are influenced by various inter and intrapersonal factors, and for certain populations, such as geriatric patients and pediatric patients, these influences must be considered. CYP2C19 genotype represents the main part of the interpersonal variability related to voriconazole blood concentrations. Thus monitoring the concentration of voriconazole is needed in clinical scenarios to minimize the negative influences of inter and intrapersonal factors. Several studies provided evidence on the stable trough concentration range from 1-2 to 4-6 mg/L, which was combined to consider the efficacy and toxicity. However, the therapeutic drug concentration needs to be narrowed down and evaluated by large-scale clinical trials.

Conclusion:

Though there is insufficient evidence on the relationship between CYP2C19 genotypes and clinical outcomes, there is a great potential for the initial voriconazole dose selection to be guided by the CYP2C19 genotype. Finally, voriconazole therapeutic drug monitoring is essential to provide patient-specific dosing recommendations, leading to more effective anti-fungal regimens to increase clinical effica-cy and reduce adverse drug reactions.

A Personalized CYP2C19 Phenotype-Guided Dosing Regimen of Voriconazole Using a Population Pharmacokinetic Analysis

Highly variable and non-linear pharmacokinetics of voriconazole are mainly caused by CYP2C19 polymorphisms. This study aimed to develop a mechanistic population pharmacokinetic model including the CYP2C19 phenotype, and to assess the appropriateness of various dosing regimens based on the therapeutic target. A total of 1,828 concentrations from 193 subjects were included in the population pharmacokinetic analysis. A three-compartment model with an inhibition compartment appropriately described the voriconazole pharmacokinetics reflecting auto-inhibition. Voriconazole clearance in the CYP2C19 intermediate metabolizers (IMs) and poor metabolizers (PMs) decreased by 17% and 53% compared to that in the extensive metabolizers (EMs). There was a time-dependent inhibition of clearance to 16.2% of its original value in the CYP2C19 EMs, and the extent of inhibition differed according to the CYP2C19 phenotypes. The proposed CYP2C19 phenotype-guided initial dosing regimens are 400 mg twice daily (bid) for EMs, 200 mg bid for IMs, and 100 mg bid for PMs. This CYP2C19 phenotype-guided initial dosing regimen will provide a rationale for individualizing the optimal voriconazole therapy.

Correlation of CYP2C19 genotype with plasma voriconazole exposure in South-western Chinese Han patients with invasive fungal infections

The aim of this study was to investigate the correlation between CYP2C19 genotype and dose-adjusted voriconazole (VCZ) trough concentrations (C0/dose).We analyzed the correlation between CYP2C192(681G>A), CYP2C193(636G>A), and CYP2C1917(-806C>T) genetic polymorphisms and the dose-corrected pre-dose concentration (C0/dose) in 106 South-western Chinese Han patients.The frequencies of variant alleles of CYP2C192, 3, and 17 were 29.7%, 4.25%, and 0.92%. For 49.3% of the VCZ samples, the therapeutic window between 1.5 and 5.5 μg/ml was reached. Following the first dose VCZ measurement, in subsequent samples the proportion of VCZ C0 within the therapeutic window increased, suggesting effective therapeutic drug monitoring (TDM) (P = .001). The VCZ C0 was significantly different (P = .010) between patients with normal metabolism (NMs), intermediate metabolism (IMs), and poor metabolism (PMs). The VZC C0/dose was 12.2 (interquartile range (IQR), 8.33-18.2 μg·ml/kg·day), and 7.68 (IQR, 4.07-16.3 μg·ml/kg·day) in PMs and IMs patients, respectively, which was significantly higher than in NMs phenotype patients (4.68; IQR, 2.51-8.87 μg·ml/kg·day, P = .008 and P = .014).This study demonstrated that the VCZ C0/dose was significantly influenced by the CYP2C19 genotype in South-western Chinese Han patients. In this patient population, more over-exposure was observed in patients with a CYP2C19 genotype associated with poor or intermediate metabolism. CYP2C19 genotype-based dosing combined with TDM will support individualization of VCZ dosing, and potentially will minimize toxicity and maximize therapeutic efficacy.

The effects of cytochrome P450 2C19 polymorphism on the metabolism of voriconazole in vitro

Background

CYP/CYP450 2C19 (CYP2C19) is a highly polymorphic enzyme and exhibits individual differences in metabolic activity. The purpose of this research was mainly to explore the catalytic activities of 30 CYP2C19 variants on the substrate voriconazole in vitro, including 24 novel CYP2C19 variants (2C19.2E-.2H, .2J, .3C, .29-.33, L16F, 35FS, R124Q, R125G, T130M, N231T, M255T, R261W, N277K, S303N, I327T, N403I, and A430V) found in Chinese Han population for the first time.

Methods

These CYP2C19 variants were expressed in Spodoptera frugiperda (Sf) 21 insect cells using the baculovirus-mediated expression system. The substrate voriconazole was incubated with the abovementioned proteins at 37°C for 30 minutes in an appropriate designed system. Then through detecting its major metabolite voriconazole N-oxide by ultra-performance liquid chromatography tandem mass spectrometry, available data were obtained to explain the influence of CYP2C19 polymorphisms on voriconazole.

Results

From the results, when compared to CYP2C19.1, most variants exhibited either reduced V_max and/or increased K_m value, indicating that the intrinsic clearance (V_max/K_m) values of most variants were significantly altered. The catalytic activities of 20 novel variants exhibited decreases in different degrees compared to CYP2C19.1, with relative clearance values ranging from 1.11% to 83.78%. However, L16F exhibited the increased catalytic activity for 135.68%. In addition, the kinetic parameters of four variants (2C19.2H, .3, 35FS, and R124Q) could not be detected, due to the defective gene.

Conclusion

This is the first study to report the effects of CYP2C19 polymorphisms on vori-conazole metabolism in vitro, and we hope these data could lay the foundation for the early clinical research and individualized treatment.

Population pharmacokinetics of voriconazole and CYP2C19 polymorphisms for optimizing dosing regimens in renal transplant recipients

AIMS

The aims of the present study were to characterize the pharmacokinetics of voriconazole in renal transplant recipients and to identify factors significantly affecting pharmacokinetic parameters. We also aimed to explore the optimal dosing regimens for patients who developed invasive fungal infections.

METHODS

A total of 105 patients (342 concentrations) were included prospectively in a population pharmacokinetic analysis. Nonlinear mixed-effects models were developed using Phoenix NLME software. Dosing simulations were performed based on the final model.

RESULTS

A one-compartment model with first-order absorption and elimination was used to characterize voriconazole pharmacokinetics. Population estimates of clearance, volume of distribution and oral bioavailability were 2.88 l·h-1 , 169.3 l and 58%, respectively. The allele frequencies of cytochrome P450 gene (CYP) 2C19*2, *3 and *17 variants were 29.2%, 5.2% and 0.5%, respectively. CYP2C19 genotype had a significant effect on the clearance. Voriconazole trough concentrations in poor metabolizers were significantly higher than in intermediate metabolizers and extensive metabolizers alike. The volume of distribution increased with increased body weight. The oral bioavailability was substantially lower within 1 month after transplantation but increased with postoperative time. Dosing simulations indicated that during the early postoperative period, poor metabolizers could be treated with 150 mg intravenously or 250 mg orally twice daily; intermediate metabolizers with 200 mg intravenously or 350 mg orally twice daily; and extensive metabolizers with 300 mg intravenously twice daily.

CONCLUSIONS

Using a combination of CYP2C19 genotype and postoperative time to determine the initial voriconazole dosing regimens followed by therapeutic drug monitoring could help to advance individualized treatment in renal transplantation patients with invasive fungal infections.

Pharmacogenetic of voriconazole antifungal agent in pediatric patients

AIM

We explored the role of SNPs within the SLCO1B3, SLCO1B1, SLC22A6, ABCB1, ABCG2, SLCO3A1, CYP2C19, ABCC2, SLC22A1, ABCB11 and NR1I2 genes on voriconazole pharmacokinetics.

PATIENTS & METHODS

233 pediatric patients were enrolled. Drug plasma C_trough was measured by a HPLC-MS method. Allelic discrimination was performed by qualitative real-time PCR.

RESULTS

SLCO1B3 rs4149117 c.334 GT/TT (p = 0.046), ABCG2 rs13120400 c.1194 + 928 CC (p = 0.029) and ABCC2 rs717620 c.-24 GA/AA (p = 0.025) genotype groups significantly influenced C_trough. ethnicity (p = 0.042), sex (p = 0.033), SLCO1B3 rs4149117 c.334 GT/TT (p = 0.041) and ABCB1 rs1045642 c.3435 TT (p = 0.016) have been retained in linear regression model as voriconazole predictor factors.

CONCLUSION

Understanding how some gene polymorphisms affect the voriconazole pharmacokinetic is essential to optimally dose this agent.

Impact of CYP2C19 Genotype and Liver Function on Voriconazole Pharmacokinetics in Renal Transplant Recipients

BACKGROUND

Invasive fungal infection (IFI) is one of the leading causes of early death after renal transplantation. Voriconazole (VRC) is the first-line drug of IFI. Because of the large inter- and intraindividual variability in VRC plasma concentrations and the narrow therapeutic window for treating patients with IFIs, it is crucial to study the factors which could influence pharmacokinetic variability. We performed a population pharmacokinetics (PPK) study of VRC for personalized medicine.

METHODS

A total of 125 trough concentrations (Cmin) from 56 patients were evaluated, retrospectively. Nonlinear mixed effect model was used to describe a PPK model that was internally validated by bootstrap method. Potential covariates included demographic characteristics, physiological and pathological data, concomitant medications, and CYP2C19 genotype.

RESULTS

A 1-compartment model with first-order absorption and elimination was fit to characterize the VRC pharmacokinetics in renal transplant recipients (RTRs). Aspartate aminotransferase (AST) had a significant influence on clearance (CL) while CYP2C19 genotype had a major impact on the volume of distribution (V). The parameters of CL and V were 4.76 L/h and 22.47 L, respectively. The final model was V (L) = 22.47 × [1 + 2.21 × (EM = 1)] × [1 + 4.67 × (IM = 1)] × [1 + 3.30 × (PM = 1)] × exp (0.96); CL (L/h) = 4.76 × (AST/33)^(-0.23) × exp (0.14). VRC Cmin in intermediate metabolizers was significantly higher than in extensive metabolizers.

CONCLUSIONS

Liver function and CYP2C19 polymorphism are major determinants of VRC pharmacokinetic variability in RTRs. Genotypes and clinical biomarkers can determine the initial scheme. Subsequently, therapeutic drug monitoring can optimize clinical efficacy and minimize toxicity. Hence, this is a feasible way to facilitate personalized medicine in RTRs. In addition, it is the first report about PPK of VRC in RTRs.

Determinants of the Magnitude of Interaction Between Tacrolimus and Voriconazole/Posaconazole in Solid Organ Recipients

Administration of azole antifungals to tacrolimus-treated solid organ recipients results in a major drug-drug interaction characterized by increased exposure to tacrolimus. The magnitude of this interaction is highly variable but cannot currently be predicted. We performed a retrospective analysis of 126 solid organ recipients (95 lung, 31 kidney) co-treated with tacrolimus and voriconazole (n = 100) or posaconazole (n = 26). Predictors of the change in tacrolimus dose-corrected trough concentrations (C/D) between baseline and tacrolimus-azole co-therapy were assessed using linear mixed modeling. Patients were genotyped for relevant polymorphisms in CYP3A4, CYP3A5, MDR1, CYP2C19, POR, and UGT1A4. Tacrolimus C/D increased by a factor 5.0 ± 2.7 (range 1.0-20.2) for voriconazole and 4.4 ± 2.6 (range 0.9-18.0) for posaconazole, suggesting that a 66% dose reduction is insufficient for the majority of patients. Change in C/D was blunted in CYP3A5 expressors (estimated effect: -43%, p = 0.017) and affected by hematocrit (+8% per %, p = 0.004), baseline C/D (-14% per 100% increase, p < 0.001), and age (+1%, p = 0.008). However, the final model explained only 22% of interindividual variability in C/D change. In conclusion, CYP3A5 genotype and several clinical variables were identified as modulators of the tacrolimus-azole interaction, but these did not permit accurate predictions in individual patients.

Clinical Pharmacogenetics Implementation Consortium (CPIC) Guidelines for CYP2C19 and Voriconazole Therapy

Voriconazole, a triazole antifungal agent, demonstrates wide interpatient variability in serum concentrations, due in part to variant CYP2C19 alleles. Individuals who are CYP2C19 ultrarapid metabolizers have decreased trough voriconazole concentrations, delaying achievement of target blood concentrations; whereas poor metabolizers have increased trough concentrations and are at increased risk of adverse drug events. We summarize evidence from the literature supporting this association and provide therapeutic recommendations for the use of voriconazole for treatment based on CYP2C19 genotype (updates at https://cpicpgx.org/guidelines/ and www.pharmgkb.org).

Effects of cytochrome P450 3A4 and non-genetic factors on initial voriconazole serum trough concentrations in hematological patients with different cytochrome P450 2C19 genotypes

1. Polymorphisms of cytochrome P450 2C19 (CYP2C19) is an important factor contributing to variability of voriconazole pharmacokinetics. Polymorphisms of CYP3A4, CYP3A5, CYP2C9 and non-genetic factors such as age, gender, body mass index (BMI), transaminase levels, concomitant medications might also affect voriconazole initial steady serum trough concentration (VIC_min) in haematological patients, but the effects were not clear. 2. Eighteen single-nucleotide polymorphisms in CYP2C19, CYP3A4, CYP3A5, CYP2C9 were genotyped. Patients were stratified into two groups according to CYP2C19 genotype. Group 1 were patients with CYP2C19*2 or CYP2C19*3, and Group 2 were homozygous extensive metabolizers. The effects were studied in different groups. VIC_min was adjusted on daily dose (VIC_min/D) for overcoming effect of dose. 3. A total of 106 blood samples from 86 patients were included. In final optimal scaling regression models, polymorphisms of rs4646437 (CYP3A4), age, BMI was identified to be factors of VIC_min/D in Group 1 (R²=.255, p < .001). Only age was confirmed as a factor of VIC_min/D in Group 2 (R²=0.144, p = .021). 4. Besides polymorphisms of CYP2C19, in individualized medication of voriconazole in haematological patients, polymorphisms of CYP3A4, and non-genetic factors as BMI, age should also be taken into account, especially for individuals with CYP2C19*2 or CYP2C19*3.