Serum voriconazole level variability in patients with hematological malignancies receiving voriconazole therapy

Pharmacogenetic implementation for CYP2C19 and pharmacokinetics of voriconazole in children with malignancy or inborn errors of immunity

BACKGROUND

Voriconazole pharmacokinetics (PK) are known to be affected by genetic polymorphisms of drug-metabolizing enzymes such as CYP2C19; however, such information is limited for the pediatric population. The primary aim of this study is to establish a voriconazole PK model incorporating CYP2C19 phenotypes in Japanese children with malignancy or inborn errors of immunity.

METHODS

CYP2C19 genotypes were assessed by whole-genome genotyping and defined as follows: *17/*17: ultrarapid metabolizer (URM), *1/*17: rapid metabolizer (RM), *1/*1:normal metabolizer (NM), *1/*2, *1/*3, *2/*17:intermediate metabolizer (IM), and *2/*2, *2/*3, *3/*3: poor metabolizer (PM). Population PK analysis was performed. The voriconazole serum concentration profile was described by a two-compartment model with first-order absorption, mixed linear and nonlinear (Michaelis-Menten) elimination.

RESULTS

Voriconazole concentration data were available from 60 patients with a median age of 5.3 years. The phenotypes predicted from CYP2C19 genotypes were RM in 1 (2 %), NM in 21 (35 %) patients, IM in 27 (45 %) patients, and PM in 11 (18 %) patients. Underlying diseases included 38 (63%) patients with hematological malignancy and 18 (30 %) patients with inborn errors of immunity. Among the CYP2C19 phenotypes, PM was predicted to show complete inhibition (the degree of Vmax inhibition [Vmax, inh] = 100 %; Vmax = 0). The estimated parameters of Vmax,inh were +0.8 higher in patients with gamma-glutamyl transpeptidase (γ-GTP) Grade 2 or higher and +2.7 higher when C-reactive protein (CRP) levels were 2.0 mg/dL or higher.

CONCLUSION

CYP2C19 genetic polymorphisms, γ-GTP, and CRP affect Vmax,inh of voriconazole in children with malignancy or inborn errors of immunity.

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.

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.

Voriconazole-Induced Hepatotoxicity Presenting With Severe Hepatic Encephalopathy After Liver Transplantation

Voriconazole-induced hepatotoxicity is a relatively rare but serious clinicopathologic entity. This drug is frequently used for invasive aspergillosis and other fungal infections. We report a patient with alcoholic cirrhosis who developed hepatic encephalopathy due to voriconazole administered for invasive pulmonary aspergillosis and subsequently showed marked improvement in mental status with dose adjustment of the drug. The patient eventually underwent an uneventful liver transplant. Histopathologic examination of the diseased liver specimen revealed numerous rhomboid-shaped crystals, deemed secondary to liver injury after voriconazole-induced hepatotoxicity. Additionally, this article briefly reviews the available data on voriconazole-induced hepatotoxicity with special emphasis on plasma drug concentration monitoring.

Risk factors associated with insufficient and potentially toxic voriconazole plasma concentrations: an observational study

The aim of this study was to identify potential factors associated with insufficient/toxic voriconazole trough concentrations (VTCs) in patients in order to screen the high-risk population. A total of 119 VTCs were obtained from 67 patients. Multivariate regression analysis suggested that insufficient VTCs (<1.0 mg/L) were significantly associated with younger age and underlying hematological malignancy, and toxic VTCs (>5.5 mg/L) were significantly associated with lower serum albumin (ALB) level. Receiver operating characteristic curve analysis indicated that patients whose age < 47 years were the high-risk population of insufficient VTCs, and patients whose ALB <27 g/L were the high-risk population of toxic VTCs. Younger age and underlying hematological malignancy were significant predictors of insufficient VTCs, and lower ALB level was found to be a significant predictor of toxic VTCs. Therefore, we recommend to increase the monitoring on these high-risk population to avoid treatment failure and to prevent toxic adverse events.

Voriconazole treatment in adults and children with hematological diseases: can it be used without measurement of plasma concentration?

Indication and timing of trough plasma-voriconazole (VCZ)-concentration (t-PVC) measurement during VCZ treatment is a debated issue. Patterns of t-PVC were prospectively evaluated in pediatric (50 courses) and adult (95 courses) hematologic patients. Efficacy patterns were defined: adequate, t-PVC always ≥1 mcg/ml; borderline, at least one t-PVC measurement <1 mcg/ml but median value of the measurements ≥1 mcg/ml; inadequate, median value of the measurements <1 mcg/ml. Toxicity patterns were defined: favorable, t-PVC always ≤5 mcg/ml; borderline, one or more t-PVC measurements >5 mcg/ml but median value of the measurements ≤5 mcg/ml; unfavorable, median value of the measurements >5 mcg/ml. In children and adults the mean t-PVCs were higher during intravenous treatments. The t-PVC efficacy pattern was adequate, borderline and inadequate in 48%, 12%, and 40% of courses, respectively, in children, and in 66.3%, 16.8%, and 16.8% of courses, respectively, in adults. Adequate efficacy pattern was more frequent in children with body weight above the median (≥25 kg) (OR 4.8; P = .011) and in adults with active hematological disease receiving intravenous therapy (OR 3.93; P = .006). Favorable toxicity pattern was more frequent in children receiving VCZ daily dosage below the median (<14 mg/kg) (OR 4.18; P = .027) and in adults with body weight below the median (<68 kg) (OR 0.22; P = .004). T-PVC measurement is generally needed, however, a non t-PVC guided approach may be considered in heavier adults receiving intravenous VCZ. The risk of supratherapeutic levels does not seem an absolute indication for t-PVC monitoring.

Voriconazole Dosing in Children Younger Than 3 Years Undergoing Cancer Chemotherapy or Hematopoietic Stem Cell Transplantation

There are limited pediatric population pharmacokinetic data for voriconazole dosing, particularly in younger children. In a cohort of 34 patients younger than 3 years receiving voriconazole, the majority (n = 23, 68%) had a low initial serum concentration <1 mg/L. Among 23 children <2 years old, 19 (83%) had an initial trough <1 mg/L. There was large intra- and interindividual variability in trough levels. Dosing also varied from 3.3 to 19.6 mg/kg per dose. Only 2 of 34 patients had a documented adverse drug reaction attributable to voriconazole. More data are needed to establish optimal dosing in very young children.

Medication Complications in Extracorporeal Membrane Oxygenation

The need for extracorporeal membrane oxygenation (ECMO) therapy is a marker of disease severity for which multiple medications are required. The therapy causes physiologic changes that impact drug pharmacokinetics. These changes can lead to exposure-driven decreases in efficacy or increased incidence of side effects. The pharmacokinetic changes are drug specific and largely undefined for most drugs. We review available drug dosing data and provide guidance for use in the ECMO patient population.

Significance of monitoring plasma concentration of voriconazole in a patient with liver failure: A case report

RATIONALE

Invasive pulmonary aspergillosis is associated with significant morbidity and mortality in patients with liver failure. Voriconazole (VRCZ) is recommended as a primary therapeutic agent for the treatment of invasive aspergillosis and metabolized in the liver. Now, data are still lacking on the safety and appropriate dosage of VRCZ in patients with liver failure. Here, we report a representative case of invasive pulmonary fungal infection in a patient with liver failure who was treated with low-dose VRCZ.

PATIENT CONCERNS

A 21-year-old man, presented with subacute liver failure caused suspected by viral infection, was admitted on June 22, 2014. Liver function was not improved by the treatment of gancicolovir and methylprednisolone. The patient presented with fever, cough, and hyperpyrexia on July 14. Laboratory tests revealed raised neutrophil percentage (82.1%, normal range [NR] 50-70), international normalized ratio (INR) (2.32, NR 0.8-1.2) and levels of serum lactic acid (4.308 mmol/L, NR 0.6-2.2), alanine transaminase (165 U/L,NR 0-40), aspartate transaminase (99 U/L, NR 8-40), and total bilirubin (654 mmol/L, NR 3.4-20.5). Furthermore, CD4+ T cell, CD8+T cell, and B cell count were low (169, 221, and l8/mL, respectively). Sputum smear microscopy for bacteria was negative, but the direct observation for fungal elements was positive. Thoracic CT scan revealed bilateral pulmonary high-density shadow. Sputum cultures were positive 2 days later with the presence of Aspergillus fumigatus.

DIAGNOSES

Therefore, this patient diagnosed with suspected pulmonary a spergillosis.

INTERVENTIONS

VRCZ was used on July 15th and its dosage was 400 mg twice on day 1 followed by a maintenance dose of 100 mg twice daily according to drug usage instruction. However, some side effects, such as tremors, lips twitching, and hair loss, occurred. Plasma VRCZ trough concentration was 8.1 mg/mL which was much higher than the recommend level. Therefore, VRCZ dosage was adjusted according to its plasma concentration. VRCZ plasma concentration fluctuated between 2.5 to 4.7 mg/mL when its dosage was 100 mg once daily and side effects disappeared.

OUTCOMES

VRCZ was administered for 2 months. This patient's symptoms and liver function were improved. A follow-up CT scan performed at the end of VRCZ therapy indicated that the high-density shadow had diminished.

LESSONS

This case demonstrated that low-dose VRCZ (maintenance dose, 100 mg/day) can achieve effective plasma concentration and reduce side effects without liver damage. We believe that VRCZ is safe to be administered in patients with liver failure, but its plasma concentration should be carefully monitored.