An ultra performance liquid chromatography-tandem mass spectrometry method for the therapeutic drug monitoring of isavuconazole and seven other antifungal compounds in plasma samples

Overview of therapeutic drug monitoring and clinical practice

With the rapid development of clinical pharmacy in China, therapeutic drug monitoring (TDM) has become an essential tool for guiding rational clinical drug use and is widely concerned. TDM is a tool that combines pharmacokinetic and pharmacodynamic knowledge to optimize personalized drug therapy, which can improve treatment outcomes, reduce drug-drug toxicity, and avoid the risk of developing drug resistance. To effectively implement TDM, accurate and sophisticated analytical methods are required. By researching the literature published in recent years, we summarize the types of commonly monitored drugs, therapeutic windows, and clinical assays and track the trends and hot spots of therapeutic drug monitoring. The purpose is to provide guidelines for clinical blood drug concentration monitoring, to implement individualized drug delivery programs better, to ensure the rational use of drugs for patients, and to provide a reference for the group to carry out related topics in the future.

Caspofungin sequestration in a polyacrylonitrile-derived filter: Increasing the dose does not mitigate sequestration

OBJECTIVES

Critically ill patients frequently require continuous renal replacement therapy. Echinocandins are recommended as first-line treatment of candidemia. Preliminary results suggested echinocandin sequestration in a polyacrylonitrile filter. The present study aimed to determine whether increasing the dose might balance sequestration.

METHODS

An STX filter (Baxter-Gambro) was used. A liquid chromatography-mass spectrometry method was used for dosage of caspofungin. In vitro drug disposition was evaluated by NeckEpur (Neckepur, Versailles, France) technology using a crystalloid medium instead of diluted/reconstituted blood, focusing on the disposition of the unbound fraction of drugs. Two concentrations were assessed.

RESULTS

At the low dose, the mean measured initial concentration in the central compartment (CC) was 5.1 ± 0.6 mg/L. One hundred percent of the initial amount was eliminated from the CC within the 6-h session. The mean total clearance from the CC was 9.6 ± 2.5 L/h. The mean percentages of elimination resulting from sequestration and diafiltration were 96.0 ± 5.0 and 4.0 ± 5.2%, respectively. At high dose, the mean measured initial concentration in the CC was 13.1 mg/L. One hundred percent of the initial amount was eliminated from the CC within the 6-h session. The mean total clearance from the CC was 9.5 L/h. The mean percentages of elimination resulting from sequestration and filtration were 88.5% and 11.5%, respectively.

CONCLUSION

Increasing the dose does not mitigate caspofungin sequestration in the STX filter. The results raise caution about the simultaneous use of caspofungin and polyacrylonitrile-derived filters. Intermittent modes of renal replacement therapy might be considered. For sensitive species, fluconazole might be an alternative.

Advancing posaconazole quantification analysis with a new reverse-phase HPLC method in its bulk and marketed dosage form

Introduction: Posaconazole is a widely used antifungal drug, and its accurate quantification is essential for quality control and assessment of its pharmaceutical products. This study aimed to develop and validate a reverse-phase high-performance liquid chromatography (HPLC) analytical method for quantifying Posaconazole in bulk and dosage form. Methods: The HPLC method was developed and validated based on International Conference on Harmonisation (ICH) guidelines. The developed method was then applied to quantify Posaconazole in a marketed tablet formulation. The method's specificity, linearity, precision, accuracy, robustness, and stability were evaluated. Results: The developed HPLC method showed good linearity over a 2-20 μg/mL concentration range. The percentage recovery of Posaconazole from the bulk and marketed formulations was found to be 99.01% and 99.05%, respectively. The intra-day and inter-day precisions were less than 1%, and the method was stable under different conditions. The HPLC method was successfully applied to quantify Posaconazole in the marketed formulation. Conclusion: The developed and validated HPLC method is reliable and efficient for analyzing Posaconazole in bulk and dosage forms. The method's accuracy, precision, specificity, linearity, robustness, and stability demonstrate its effectiveness. The method can be used for the quality control and assessment of Posaconazole-containing pharmaceutical products.

Antifungals: From Pharmacokinetics to Clinical Practice

The use of antifungal drugs started in the 1950s with polyenes nystatin, natamycin and amphotericin B-deoxycholate (AmB). Until the present day, AmB has been considered to be a hallmark in the treatment of invasive systemic fungal infections. Nevertheless, the success and the use of AmB were associated with severe adverse effects which stimulated the development of new antifungal drugs such as azoles, pyrimidine antimetabolite, mitotic inhibitors, allylamines and echinochandins. However, all of these drugs presented one or more limitations associated with adverse reactions, administration route and more recently the development of resistance. To worsen this scenario, there has been an increase in fungal infections, especially in invasive systemic fungal infections that are particularly difficult to diagnose and treat. In 2022, the World Health Organization (WHO) published the first fungal priority pathogens list, alerting people to the increased incidence of invasive systemic fungal infections and to the associated risk of mortality/morbidity. The report also emphasized the need to rationally use existing drugs and develop new drugs. In this review, we performed an overview of the history of antifungals and their classification, mechanism of action, pharmacokinetic/pharmacodynamic (PK/PD) characteristics and clinical applications. In parallel, we also addressed the contribution of fungi biology and genetics to the development of resistance to antifungal drugs. Considering that drug effectiveness also depends on the mammalian host, we provide an overview on the roles of therapeutic drug monitoring and pharmacogenomics as means to improve the outcome, prevent/reduce antifungal toxicity and prevent the emergence of antifungal resistance. Finally, we present the new antifungals and their main characteristics.

Progress of triazole antifungal agent posaconazole in individualized therapy

WHAT IS KNOWN AND OBJECTIVE

Posaconazole is the second-generation triazole antifungal agent with widespread clinical application. Posaconazole exposure is influenced by various factors such as drug interactions, disease state and diet, resulting in a high interindividual variability in many patients and failure to ensure therapeutic efficacy. Therefore, it is necessary to conduct individualized therapy on posaconazole to ensure the efficacy and safety of treatment.

METHODS

Articles were identified through PubMed using the keywords such as "posaconazole," "therapeutic drug monitoring" and "Population pharmacokinetics" from 1 January 2001 to 30 April 2022.

RESULTS AND DISCUSSION

In this paper, we review the individualized treatment studies of posaconazole from the three aspects of therapeutic drug monitoring, population pharmacokinetic study and Monte Carlo simulation to provide reference for in-depth individualized posaconazole dosing studies.

WHAT IS NEW AND CONCLUSION

This review suggests that therapeutic drug monitoring should be performed in patients taking posaconazole to adjust the dosage and assess the efficacy and cost-effectiveness of posaconazole under different clinical conditions and different dosing regimens through Monte Carlo simulations. In the future, a more detailed delineation and comprehensive examination of posaconazole PPK for specific populations requires further study.

Therapeutic Drug Monitoring of the Echinocandin Antifungal Agents: Is There a Role in Clinical Practice? A Position Statement of the Anti-Infective Drugs Committee of the International Association of Therapeutic Drug Monitoring and Clinical Toxicology

PURPOSE

Reduced exposure to echinocandins has been reported in specific patient populations, such as critically ill patients; however, fixed dosing strategies are still used. The present review examines the accumulated evidence supporting echinocandin therapeutic drug monitoring (TDM) and summarizes available assays and sampling strategies.

METHODS

A literature search was conducted using PubMed in December 2020, with search terms such as echinocandins, anidulafungin, caspofungin, micafungin, or rezafungin with pharmacology, pharmacokinetics (PKs), pharmacodynamics (PDs), drug-drug interactions, TDM, resistance, drug susceptibility testing, toxicity, adverse drug reactions, bioanalysis, chromatography, and mass spectrometry. Data on PD/PD (PK/PD) outcome markers, drug resistance, PK variability, drug-drug interactions, assays, and TDM sampling strategies were summarized.

RESULTS

Echinocandins demonstrate drug exposure-efficacy relationships, and maximum concentration/minimal inhibitory concentration ratio (Cmax/MIC) and area under the concentration-time curve/MIC ratio (AUC/MIC) are proposed PK/PD markers for clinical response. The relationship between drug exposure and toxicity remains poorly clarified. TDM could be valuable in patients at risk of low drug exposure, such as those with critical illness and/or obesity. TDM of echinocandins may also be useful in patients with moderate liver impairment, drug-drug interactions, hypoalbuminemia, and those undergoing extracorporeal membrane oxygenation, as these conditions are associated with altered exposure to caspofungin and/or micafungin. Assays are available to measure anidulafungin, micafungin, and caspofungin concentrations. A limited-sampling strategy for anidulafungin has been reported.

CONCLUSIONS

Echinocandin TDM should be considered in patients at known risk of suboptimal drug exposure. However, for implementing TDM, clinical validation of PK/PD targets is needed.

In Vivo Efficacy of Voriconazole in a Galleria mellonella Model of Invasive Infection Due to Azole-Susceptible or Resistant Aspergillus fumigatus Isolates

Aspergillus fumigatus is an environmental filamentous fungus responsible for life-threatening infections in humans and animals. Azoles are the first-line treatment for aspergillosis, but in recent years, the emergence of azole resistance in A. fumigatus has changed treatment recommendations. The objective of this study was to evaluate the efficacy of voriconazole (VRZ) in a Galleria mellonella model of invasive infection due to azole-susceptible or azole-resistant A. fumigatus isolates. We also sought to describe the pharmacokinetics of VRZ in the G. mellonella model. G. mellonella larvae were infected with conidial suspensions of azole-susceptible and azole-resistant isolates of A. fumigatus. Mortality curves were used to calculate the lethal dose. Assessment of the efficacy of VRZ or amphotericin B (AMB) treatment was based on mortality in the lethal model and histopathologic lesions. The pharmacokinetics of VRZ were determined in larval hemolymph. Invasive fungal infection was obtained after conidial inoculation. A dose-dependent reduction in mortality was observed after antifungal treatment with AMB and VRZ. VRZ was more effective at treating larvae inoculated with azole-susceptible A. fumigatus isolates than larvae inoculated with azole-resistant isolates. The concentration of VRZ was maximal at the beginning of treatment and gradually decreased in the hemolymph to reach a C_min (24 h) between 0.11 and 11.30 mg/L, depending on the dose. In conclusion, G. mellonella is a suitable model for testing the efficacy of antifungal agents against A. fumigatus.

High-throughput simultaneousquantification offive azole anti-fungal agents and one active metabolite in human plasma using ultra-high-performance liquid chromatography coupled to tandem mass spectrometry

OBJECTIVES

For patients with hematological malignancy, triazole antifungal agents such as fluconazole (FLCZ), itraconazole (ITCZ), voriconazole (VRCZ), posaconazole (PSCZ) and isavuconazole (ISCZ) are often used for prophylaxis of deep mycosis. Since these azoles exhibit large pharmacokinetic variability, dose adjustment by therapeutic drug monitoring is recommended for some azoles. This study aimed to develop and validate a novel method for simultaneous determination of plasma concentrations of FLCZ, ITCZ, VRCZ, PSCZ, ISCZ and ITCZ-OH, an active metabolite of ITCZ, using ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS).

DESIGN & METHODS

A high-throughput solid-phase extraction method using 96-well MCX µElution Plate was selected as the pretreatment procedure.

RESULTS

The calibration curves for FLCZ, ITCZ, ITCZ-OH, VRCZ, PSCZ and ISCZ showed good linearity (back-calculation of calibrators: relative error ≤ 15% [LLOQ: ≤ 20%]) over wide ranges of 100-100000, 20-20000, 40-40000, 20-20000, 5-5000 and 50-50000 ng/mL, respectively. The validation results of all six drugs fulfilled the criteria of the guidance for bioanalytical method validation of the US Food and Drug Administration for within-batch and batch-to-batch precision and accuracy. The extraction recovery rates were good at ≥ 74.9%, and almost no matrix effects were found for all the drugs. The trough (10 h post-dose in 1 patient on PSCZ) drug concentrations in patients with hematologic malignancy who received oral FLCZ, ITCZ, VRCZ or PSCZ were quantified using the method developed. The measurements for all samples were within the ranges of the calibration curves, demonstrating the feasibility of clinical application of the novel method.

CONCLUSIONS

We have succeeded in developing a novel high-throughput method using UHPLC-MS/MS for simultaneous quantification of plasma concentrations of FLCZ, ITCZ, ITCZ-OH, VRCZ, PSCZ and ISCZ.

Interspecies comparison of plasma metabolism and sample stabilization for quantitative bioanalyses: Application to (R)-CE3F4 in preclinical development, including metabolite identification by high-resolution mass spectrometry

The CE3F4 is an inhibitor of the type 1 exchange protein directly activated by cAMP (EPAC1), which is involved in numerous signaling pathways. The inhibition of EPAC1 shows promising results in vitro and in vivo in different cardiac pathological situations like hypertrophic signaling, contributing to heart failure, or arrhythmia. An HPLC-UV method with a simple and fast sample treatment allowed the quantification of (R)-CE3F4. Sample treatment consisted of simple protein precipitation with 50 µL of ethanol and 150 µL of acetonitrile for a 50 µL biological sample. Two wavelengths were used according to the origin of plasma (220 or 250 nm for human samples and 250 nm for murine samples). Accuracy profile was evaluated for both wavelengths, and the method was in agreement with the criteria given by the EMA in the guideline for bioanalytical method validation for human and mouse plasma samples. The run time was 12 min allowing the detection of the (R)-CE3F4 and a metabolite. This study further permitted understanding the behavior of CE3F4 in plasma by highlighting an important difference between humans and rodents on plasma metabolism and may impact future in vivo studies related to this molecule and translation of results between animal models and humans. Using paraoxon as a metabolism inhibitor was crucial for the stabilization of (R)-CE3F4 in murine samples. HPLC-UV and HPLC-MS/MS studies were conducted to confirm metabolite structure and consequently, the main metabolic pathway in murine plasma.

Review of Chromatographic Methods Coupled with Modern Detection Techniques Applied in the Therapeutic Drugs Monitoring (TDM)

Therapeutic drug monitoring (TDM) is a tool used to integrate pharmacokinetic and pharmacodynamics knowledge to optimize and personalize various drug therapies. The optimization of drug dosing may improve treatment outcomes, reduce toxicity, and reduce the risk of developing drug resistance. To adequately implement TDM, accurate and precise analytical procedures are required. In clinical practice, blood is the most commonly used matrix for TDM; however, less invasive samples, such as dried blood spots or non-invasive saliva samples, are increasingly being used. The choice of sample preparation method, type of column packing, mobile phase composition, and detection method is important to ensure accurate drug measurement and to avoid interference from matrix effects and drug metabolites. Most of the reported procedures used liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) techniques due to its high selectivity and sensitivity. High-performance chromatography with ultraviolet detection (HPLC-UV) methods are also used when a simpler and more cost-effective methodology is desired for clinical monitoring. The application of high-performance chromatography with fluorescence detection (HPLC-FLD) with and without derivatization processes and high-performance chromatography with electrochemical detection (HPLC-ED) techniques for the analysis of various drugs in biological samples for TDM have been described less often. Before chromatographic analysis, samples were pretreated by various procedures-most often by protein precipitation, liquid-liquid extraction, and solid-phase extraction, rarely by microextraction by packed sorbent, dispersive liquid-liquid microextraction. The aim of this article is to review the recent literature (2010-2020) regarding the use of liquid chromatography with various detection techniques for TDM.

Preparation of magnetic metal organic framework and development of solid phase extraction method for simultaneous determination of fluconazole and voriconazole in rat plasma samples by HPLC

Fluconazole and voriconazole are the two broad-spectrum triazole antifungals. The present work described the fabrication method for the synthesis of the amino-modified magnetic metal-organic framework. This material was applied as a pre-sample treatment sorbent for the selective extraction of fluconazole and voriconazole in rat plasma samples. The material was fabricated by the chemical bonding approach method and was characterized by different parameters. The factors which affect the extraction efficiency of the sorbent material were also optimized in this study. Due to the optimization of solid-phase extraction conditions, the nonspecific interaction was reduced and the extraction recoveries of target drugs were increased in plasma samples. The extraction method was combined with the HPLC-UV method for the analysis. Excellent linearity (0.1-25 µg/mL), detections (0.02, 0.03 µg/mL) and quantification limits (0.04, 0.05 µg/mL) were resulted for fluconazole and voriconazole respectively. The maximum recoveries from spiked plasma samples of fluconazole and voriconazole were 86.8% and 78.6% and relative standard deviation were 0.9-2.8% and 2.2-3.6% respectively. Moreover, this sorbent material was used multiple times which was an improvement over single-use commercial sorbent materials. This validated method has practical potential for the simultaneous determination of these drugs in therapeutic drug monitoring studies as well as for routine pharmacokinetic evaluations.

Interlaboratory Analysis of Isavuconazole Plasma Concentration Assays Among European Laboratories

BACKGROUND

Under certain circumstances, clinicians treating patients with isavuconazole for invasive aspergillosis or mucormycosis may use therapeutic drug monitoring. However, the accuracy and reproducibility of the various assays used by different laboratories for the quantification of isavuconazole plasma concentrations have yet to be determined.

METHODS

Human plasma samples spiked with known concentrations of isavuconazole were provided to 27 European laboratories that took part in a "round-robin" test (an interlaboratory test performed independently at least 2 times; 2 rounds performed in the current study). Assay methods included liquid chromatography-tandem mass spectrometry (LC-MS/MS), LC with ultraviolet detection (LC-UV), LC with fluorescence detection (LC-FL), and bioassay. The accuracy and reproducibility compared with the known concentrations for each sample in each round were compared overall, between assays, and between laboratories.

RESULTS

Twenty-seven laboratories participated in the study (LC-MS/MS, n = 15; LC-UV; n = 9; LC-FL, n = 1; bioassay, n = 2). In round 1, for nominal concentrations of 1000, 1700, 2500, and 4000 ng/mL, the mean (SD) determined concentrations were 1007 (183), 1710 (323), 2528 (540), and 3898 (842) ng/mL, respectively. In round 2, for nominal concentrations of 1200, 1800, 2400, and 4000 ng/mL, the mean (SD) determined concentrations were 1411 (303), 2111 (409), 2789 (511), and 4723 (798) ng/mL, respectively. Over both rounds, determined concentrations were consistently within 15% of the nominal concentrations for 10 laboratories (LC-MS/MS, n = 4; LC-UV, n = 5; bioassay, n = 1) and consistently exceeded the upper 15% margin for 7 laboratories (LC-MS/MS and LC-UV, n = 3 each; LC-FL, n = 1).

CONCLUSIONS

Alignment of methodologies among laboratories may be warranted to improve the accuracy and reproducibility of therapeutic drug measurements.

Isavuconazole Diffusion in Infected Human Brain

We report the cases of a 39-year-old woman with chronic lymphocytic leukemia and a 21-year-old man with chronic granulomatous disease treated for cerebral aspergillosis. The patients required radical surgery for infection progression despite adequate isavuconazole plasma concentration or neurological complication. We thus decided to measure the brain isavuconazole concentration. These results suggest that the concentrations of isavuconazole obtained in the infected brain tissue clearly differ from those obtained in the normal brain tissue and the cerebrospinal fluid.

Chromatographic methods for echinocandin antifungal drugs determination in bioanalysis

The increase of fungal resistance to drugs, such as azole family, gave rise to the development of new antifungals. In this context, echinocandins emerged as a promising alternative for antifungal therapies. Following the commercialization of caspofungin in 2001, echinocandins became the first-line therapy for invasive candidiasis in different patient populations. The quantification of these drugs has gained importance since pharmacokinetic/pharmacodynamic and resistance studies are a paramount concern. This fact has led us to exhaustively examine the methodologies used for the analysis of echinocandins in biological fluids, which are mainly based on LC coupled to different detection techniques. In this review, we summarize the analytical methods for the quantification of echinocandins focusing on sample treatment, chromatographic separation and detection methods.

Validation of an Isavuconazole High-Performance Liquid Chromatography Assay in Plasma for Routine Therapeutic Drug Monitoring Applications

BACKGROUND

Isavuconazole is a triazole antifungal agent for treatment of invasive aspergillosis and mucormycosis. At present, it is unclear whether a therapeutic drug monitoring (TDM) of isavuconazole would be necessary. The aim of the investigation was to validate a high-performance liquid chromatography (HPLC) assay for routine applications.

METHODS

An HPLC assay for routine determination of isavuconazole in plasma has been adapted and validated. The assay used the reagents and HPLC column provided by the ChromSystems HPLC Kit for TDM of itraconazole, posaconazole, and voriconazole. Isocratic flow rate was set at 1.0 mL/min. Detection was performed using a fluorescence detector with excitation wavelength set at 261 nm and emission wavelength set at 366 nm.

RESULTS

The assay was linear between 0.15 and 10 mg/L with intraday and interday imprecision and accuracy <10% (<20% at lower limit of quantification). The method was applied to routine TDM of 7 patients after hematopoietic stem cell transplantation (n = 31 samples). In these patients, trough levels ranged from 0.45 to 3.06 mg/L (median 1.44 mg/L).

CONCLUSIONS

A robust and simple HPLC assay of isavuconazole in plasma for routine TDM applications is presented.

Development and validation of a volumetric absorptive microsampling assay for analysis of voriconazole and voriconazole N-oxide in human whole blood

Voriconazole is a broad-spectrum antifungal triazole drug for the treatment of invasive fungal infections. It is extensively metabolized by hepatic drug metabolizing enzymes cytochrome (CYP) 2C19 and CYP3A4. Selective inhibition of intestinal CYP3A4 by grapefruit juice may increase the oral bioavailability of voriconazole in children. To test this hypothesis it is necessary to develop a sensitive assay for measuring voriconazole and its major metabolites in a small volume of blood. Mitra® devices from Neoteryx were employed to develop and validate the assay for the quantitation of voriconazole and voriconazole N-oxide. Mitra® devices utilize volumetric absorptive microsampling (VAMS™) technology that enables accurate and precise collection of a fixed volume (10 μL of blood), reducing or eliminating the volumetric blood hematocrit assay-bias associated with the dried blood spotting technique. We developed an ultra-performance liquid chromatographic method with tandem mass spectrometry detection for quantification of voriconazole and voriconazole N-oxide. Sample extraction of Mitra® devices, followed by reversed-phase chromatographic separation and selective detection using tandem mass spectrometry with a 4.00 minute runtime per sample was employed. Standard curves were linear between 10.0 to 10,000 ng/mL for both voriconazole and voriconazole N-oxide. Intra- and inter-day accuracy were within 87-102% and precision (CV) was <12% based on a 3-day validation study. Recoveries were ≥94 % for voriconazole and ≥87 % for voriconazole N-oxide. Voriconazole and voriconazole N-oxide were stable in human whole blood under assay conditions (19 h at room temperature and 24 h in autosampler). Voriconazole was stable for 1-month in dried microsamples under different conditions (4, -20 and -78 °C). This assay provides an efficient quantitation of voriconazole and voriconazole N-oxide and is ready to be implemented for the analysis of whole blood microsamples in a pediatric clinical trial investigating the impact of intestinal inhibition of CYP3A4 on voriconazole pharmacokinetics.

Validation of a Reversed-Phase Ultra-High-Performance Liquid Chromatographic Method With Photodiode Array Detection for the Determination of Voriconazole in Human Serum and Its Application to Therapeutic Drug Monitoring

BACKGROUND

Voriconazole is a broad-spectrum triazole antifungal agent. It is widely used in the treatment of invasive fungal infections in immunocompromised patients. Because the pharmacokinetics of voriconazole demonstrates considerable variability, monitoring its serum levels plays an important role in optimizing therapies against many clinically relevant fungal pathogens. The aim of this study was to validate a simple and rapid U-HPLC-PDA method with minimal sample preparation for routine therapeutic drug monitoring (TDM) of voriconazole.

METHODS

After protein precipitation with the internal standard solution (posaconazole 5.0 mg/L in acetonitrile), chromatographic separation was performed in 4 minutes using water and acetonitrile as mobile phases and an Acquity UPLC BEH HSS C18 column (2.1 × 100 mm, 1.7 µm). The temperature was set at 45°C and the flow rate was 0.4 mL/min. Photodiode array detection at 256 nm was used as detection system. The method was validated according international guidelines for linearity, accuracy, precision, selectivity, lower limit of quantitation, carry over, and stability under different conditions.

RESULTS

All performance parameters were within acceptance criteria, demonstrating that the validated method is fit for purpose. After assay validation, 115 serum samples collected from 41 patients were analyzed to report the experience of the laboratory in TDM of voriconazole. Results showed a large variability in voriconazole trough levels, suggesting that this drug should be frequently measured in patients under treatment to enhance therapies efficacy and improve safety.

CONCLUSIONS

In this study, a reproducible U-HPLC-PDA assay with a short analysis time, requiring only a small amount of serum, good accuracy and reproducibility was validated, which is suitable for routine TDM of voriconazole in serum.

A sensitive and validated HPLC-UV method for the quantitative determination of the new antifungal drug isavuconazole in human plasma

Isavuconazole is a broad-spectrum triazole antifungal drug recently approved for the therapy of both invasive aspergillosis and mucormycosis. To support a widespread therapeutic drug monitoring of isavuconazole, a simple, sensitive, and precise high-performance liquid chromatography method with UV detection was developed and fully validated for the quantification of this drug in human plasma. The method involved a combined protein precipitation-solid-phase extraction and a chromatographic separation on a Waters XTerra RP₁₈ (150 × 4.6 mm, 3.5 μm) column using an isocratic mobile phase of ammonium acetate buffer (pH 8.0, 10 mm) and acetonitrile (45:55, v/v). The UV detection was performed at 285 nm. This method was linear (correlation coefficients ≥0.998), specific (no interference with plasma components or various potentially co-administrated drugs), sensitive (lower limit of quantification of 0.025 μg/mL), reproducible (coefficients of variation were ≤7.9%) and accurate (deviations ranged from -5.0 to 8.0%) over the range of 0.025-10 μg/mL. The method fulfilled all of the US Food and Drug Administration guidelines validation criteria and performed well in an international proficiency testing program. The assay was also successfully applied to routine therapeutic drug monitoring of patients and to drug stability investigations under various conditions.

Reliable and Easy-To-Use Liquid Chromatography-Tandem Mass Spectrometry Method for Simultaneous Analysis of Fluconazole, Isavuconazole, Itraconazole, Hydroxy-Itraconazole, Posaconazole, and Voriconazole in Human Plasma and Serum

BACKGROUND

A fast and easy-to-use liquid chromatography-tandem mass spectrometry method for the determination and quantification of 6 triazoles [fluconazole (FLZ), isavuconazole (ISZ), itraconazole (ITZ), hydroxy-itraconazole (OH-ITZ), posaconazole (PSZ), and voriconazole (VRZ)] in human plasma and serum was developed and validated for therapeutic drug monitoring.

METHODS

Sample preparation was based on protein precipitation with acetonitrile and subsequent centrifugation. Isotope-labeled analogues for each analyte were used as internal standards. Chromatographic separation was achieved using a 50 × 2.1 mm, 1.9 μm polar Hypersil Gold C18 column and mobile phase consisting of 0.1% formic acid/acetonitrile (45%/55%, vol/vol) at a flow rate of 340 μL/min. The triazoles were simultaneously detected using a triple-stage quadrupole mass spectrometer operated in selected reaction monitoring mode with positive heated electrospray ionization within a single runtime of t = 3.00 minutes.

RESULTS

Linearity of all azole concentration ranges was verified by the Mandel test and demonstrated for all azoles. All calibration curves were linear and fitted using least squares regression with a weighting factor of the reciprocal concentration. Limits of detection (μg/L/L) were FLZ, 9.3; ISZ, 0.3; ITZ, 0.6; OH-ITZ, 8.6; PSZ, 3.4; and VRZ, 2.1. The lower limits of quantitation (μg/L/liter) were FLZ, 28.3; ISZ, 1.0; ITZ, 1.7; OH-ITZ, 26.2; PSZ, 10.3; and VRZ, 6.3. Intraday and interday precisions ranged from 0.6% to 6.6% for all azoles. Intraday and interday accuracies (%bias) of all analytes were within 10.5%. In addition, we report on a 29-year-old white woman (94 kg body weight) with a history of acute myeloid leukemia who underwent stem cell transplantation. Because of diagnosis of aspergillus pneumonia, antifungal pharmacotherapy was initiated with different application modes and dosages of ISZ, and plasma concentrations were monitored over a time period of 6 months.

CONCLUSIONS

A precise and highly sensitive liquid chromatography-tandem mass spectrometry method was developed that enables quantification of triazoles in plasma and serum matrix across therapeutically relevant concentration ranges. It was successfully implemented in our therapeutic drug monitoring routine service and is suitable for routine monitoring of antifungal therapy and in severely ill patients.

Implementation of Isavuconazole in a Fluorescence-Based High-Performance Liquid Chromatography Kit Allowing Simultaneous Detection of All Four Currently Licensed Mold-Active Triazoles

Isavuconazole (ISZ) is a newly available broad-spectrum triazole agent recently approved for the treatment of both invasive aspergillosis and mucormycosis. The aim of this study was to develop a simple and reliable method for therapeutic drug monitoring (TDM) of ISZ in human plasma samples. The method involves using a kit from ChromSystems intended for TDM of itraconazole (ITZ), posaconazole (PSZ), and voriconazole (VRZ) in serum/plasma for sample preparation and high-performance liquid chromatography, using fluorescence detection with emission and excitation wavelengths set to 261 and 366 nm, respectively. The assay was linear over the ISZ concentration range of 0.2 to 20.0 mg/liter, using a 0.1-ml sample volume. The inter- and intraday coefficients of variation were all below 3.7%, whereas the accuracies ranged from 95.0 to 106.2% and the mean extraction recovery was 91.9%. In addition, the method worked well using four different Vacutainer types, with six different healthy volunteers and under a number of relevant storage conditions. Finally, the ISZ detection could be seamlessly implemented in the TDM kit for VRZ, PSZ, and ITZ, enabling simultaneous detection of all four triazoles. This method proved to be simple, accurate, precise, and well suited for routine analysis work. It has been implemented in our laboratory for the simultaneous quantitative analysis of ISZ, VRZ, PSZ, and ITZ for TDM and pharmacokinetic research. IMPORTANCE Isavuconazole is a new broad-spectrum triazole agent recently approved for the treatment of both invasive aspergillosis and mucormycosis. Currently, there is no consensus regarding the potential need for TDM of isavuconazole, and no therapeutic window has been defined. However, at the ECIL-6 meeting in 2015, it was advised that TDM is indicated in a number of different settings. In this study, we describe a rapid and validated isocratic HPLC method for fluorescence-based detection and quantification of isavuconazole in human plasma/serum samples. The method is simple and efficient with good accuracy and precision and importantly only requires a small volume of patient plasma/serum. Furthermore, this method is highly sensitive and selective and can be detected simultaneously with the three other triazoles, itraconazole, voriconazole, and posaconazole, without the need for expensive mass spectrometry equipment.