Standardization and validation of a high-efficiency liquid chromatography with a diode-array detector (HPLC-DAD) for voriconazole blood level determination. / Estandarización y validación de un método de cromatografía líquida de alta eficiencia con detector de arreglo de diodos (HPLC-DAD) para la determinación de niveles sanguíneos de voriconazol

INTRODUCTION: A specialized service for antifungal blood level determination is not available in Colombia. This service is essential for the proper follow-up of antifungal therapies. OBJECTIVE: To standardize and validate a simple, sensitive, and specific protocol based on high-performance liquid chromatography with a diode array detector for voriconazole blood level quantification. MATERIALS AND METHODS: We used an Agilent HPLC™ series-1200 equipment with a UVdiode array detector with an analytical column Eclipse XDB-C18 and pre-column Eclipse- XDB-C18 (Agilent). We used voriconazole as the primary control and posaconazole as an internal control. We performed the validation following the Food and Drug Administration (FDA) recommendations. RESULTS: The best chromatographic conditions were: Column temperature of 25°C, UV variable wavelength detection at 256 nm for voriconazole and 261 nm for posaconazole (internal standard); 50 µl of injection volume, 0,8 ml/min volume flow, 10 minutes of run time, and mobile phase of acetonitrile:water (60:40). Finally, retention times were 3.13 for voriconazole and 5.16 minutes for posaconazole. Quantification range varied from 0.125 µg/ml to 16 µg/ml. CONCLUSION: The selectivity and chromatographic purity of the obtained signal, the detection limits, and the standardized quantification make this method an excellent tool for the therapeutic monitoring of patients treated with voriconazole.

Introducción. Hasta la fecha, Colombia no cuenta con un servicio especializado de medición de niveles séricos de antifúngicos, procedimiento esencial para el adecuado seguimiento del tratamiento de infecciones fúngicas invasoras. Objetivo. Estandarizar y validar un protocolo ­simple, sensible y específico­ basado en la aplicación de cromatografía líquida de alta eficiencia acoplada con un detector de arreglo de diodos para la cuantificación de los niveles séricos de voriconazol. Materiales y métodos. Se usó un equipo HPLC-Agilent™, serie-1200, con un detector UVDAD, una columna analítica Eclipse-XDB-C18 y una pre-columna Eclipse-XDB-C18, ambas de la marca Agilent. Como control primario se utilizó voriconazol y como control interno, posaconazol. La validación se hizo cumpliendo todos los criterios de aceptación recomendados por la Food and Drug Administration (FDA). Resultados. Las mejores condiciones cromatográficas se obtuvieron con los siguientes parámetros: temperatura de la columna de 25 °C, detección UV-VWD de 261 nm, volumen de inyección de 50 µl, flujo de 0,8 ml/minuto y un tiempo de corrido de 10 minutos. La fase móvil usada fue acetonitrilo:agua (60:40) y los tiempos finales de retención fueron de 3,13 para voriconazol y de 5,16 minutos para posaconazol. El rango de cuantificación fue desde 0,125 µg/ml hasta 16 µg/ml. Conclusiones. La selectividad y la pureza de la señal cromatográfica, así como los límites de detección y cuantificación estandarizados hacen de esta metodología una excelente herramienta para el seguimiento terapéutico de pacientes tratados con voriconazol o en profilaxis con este fármaco.

Quantification of the aromatase inhibitor letrozole and its carbinol metabolite in mouse plasma by UHPLC-MS/MS.

A liquid chromatography - electrospray ionization-mass spectrometry (LC-ESI-MS) method was developed for the quantification of letrozole, a third-generation aromatase inhibitor, and its main carbinol metabolite (CM) in support of murine pharmacokinetic studies. Using polarity switching, simultaneous ESI-MS measurement of letrozole and CM was achieved in positive and negative mode, respectively. The assay procedure involved a one-step protein precipitation and extraction of all analytes from mouse plasma requiring only 5 µL of sample. Separation was optimized on an Accucore aQ column with gradient elution at a flow rate of 0.4 mL/min in 5 min. Two calibration curves per day over four consecutive measurement days showed satisfactory linear responses (r2 > 0.99) over concentration ranges of 5-1000 ng/mL and 20-2000 ng/mL for letrozole and CM, respectively. No matrix effect was found, and the mean extraction recoveries were 103-108 % for letrozole and 99.8-107 % for CM. Precision and accuracy within a single run and over four consecutive measurement days were verified to be within acceptable limits. Application of the developed method to preclinical pharmacokinetic studies in mice receiving oral letrozole at a dose 1 or 10 mg/kg revealed that the systemic exposure to letrozole was dose-, formulation-, and strain-dependent. These findings may inform the future design of preclinical studies aimed at refining the pharmacological profile of this clinically important drug.

Personalized Antifungal Therapy Through Model-Informed Precision Dosing of Posaconazole.

BACKGROUND AND OBJECTIVE: Posaconazole is a pharmacotherapeutic pillar for prophylaxis and treatment of invasive fungal diseases. Dose individualization is of utmost importance as achieving adequate antifungal exposure is associated with improved outcome. This study aimed to select and evaluate a model-informed precision dosing strategy for posaconazole. METHODS: Available population pharmacokinetic models for posaconazole administered as a solid oral tablet were extracted from the literature and evaluated using data from a previously published prospective study combined with data collected during routine clinical practice. External evaluation and selection of the most accurate and precise model was based on graphical goodness-of-fit and predictive performance. Measures for bias and imprecision included mean percentage error (MPE) and normalized relative root mean squared error (NRMSE), respectively. Subsequently, the best-performing model was evaluated for its a posteriori fit-for-purpose and its suitability in a limited sampling strategy. RESULTS: Seven posaconazole models were evaluated using 764 posaconazole plasma concentrations from 143 patients. Multiple models showed adequate predictive performance illustrated by acceptable goodness-of-fit and MPE and NRMSE below ± 10% and ± 25%, respectively. In the fit-for-purpose analysis, the selected model showed adequate a posteriori predictive performance. Bias and imprecision were lowest in the presence of two prior measurements. Additionally, this model showed to be useful in a limited sampling strategy as it adequately predicted total posaconazole exposure from one (non-)trough concentration. CONCLUSION: We validated an MIPD strategy for posaconazole for its fit-for-purpose. Thereby, this study is an important first step towards MIPD-supported posaconazole dosage optimization with the goal to improve antifungal treatment in clinical practice.

In Silico Pharmacokinetics Evaluation of Forgiveness for Doravirine and Rilpivirine.

BACKGROUND: This study aimed to evaluate the concentrations of rilpivirine (RLP) and doravirine (DOR) after 3 days-off using simulations from population pharmacokinetics models. METHODS: The authors conducted a series of 500 sets of 10,000 Monte Carlo simulations to examine the steady-state conditions for 2 common dosage levels: 25 mg/d for RLP and 100 mg/d for DOR. These simulations were conducted under 2 scenarios: 1 without drug cessation and another after a 3-day break. The validity of the implementation was established through a comparison of median trough concentrations (C24h) with previously reported data. Subsequently, the proportion of simulated patients with C24h and C72h after 3 days-off (C72h/3do) that exceeded the inhibitory concentration 50 (IC50), 5.2 mcg/L for DOR and 20.5 mcg/L for RLP respectively, was calculated. The inhibitory quotient (IQ) was also computed, which was 6 times IC50 for DOR and 4.5 times IC50 for RLP. Finally, nomograms were constructed to estimate the probability of having C72h/3do > IC50 or > IQ for different ranges of C24h. RESULTS: Simulated C24h median ± SD for RLP were 61.8 ± 0.4 mcg/L and for DOR 397 ± 0 mcg/L. For RLP, 99.3 ± 0.1% exceeded IC50 at C24h, 16.4 ± 0.4% at C72h/3do, and none surpassed the IQ threshold. In contrast, DOR had 100% ± 0% above IC50 at C24h, 93.6 ± 0.2% at C72h/3do, and 58.6 ± 0.5% exceeded the IQ. CONCLUSIONS: These findings suggest that treatment with DOR may offer a more forgiving therapeutic profile than RLP, given the larger proportion of patients achieving effective drug exposure with DOR. However, it is important to acknowledge a significant limitation of this study, namely, the assumption that drug concentration is a perfect surrogate for drug effectiveness.

A Phase 1 Study to Evaluate the Drug Interaction Between Islatravir (MK-8591) and Doravirine in Adults Without HIV.

BACKGROUND AND OBJECTIVES: Islatravir (MK-8591) is a novel nucleoside analogue in development for the treatment and prevention of HIV-1 infection. Doravirine is a non-nucleoside reverse transcriptase inhibitor indicated for the treatment of HIV-1 infection. This study evaluated the pharmacokinetics, safety, and tolerability of islatravir and doravirine coadministration in a double-blind, placebo-controlled, randomized, fixed-sequence study. METHODS: Adult participants without HIV infection were administered oral doravirine 100 mg (n = 10) or placebo (n = 4) once daily (QD) for 5 days, immediately followed by oral islatravir 2.25 mg (n = 10) or placebo QD (n = 4) for 14 days; islatravir 2.25 mg and doravirine 100 mg QD, or placebo QD, were then coadministered for 5 days. Pharmacokinetic and safety data were collected. RESULTS: Doravirine geometric least-squares mean ratios (90% confidence intervals (CIs)) of (doravirine + islatravir)/doravirine for the area under the plasma drug concentration-time curve over 24 h (AUC0-24h), maximum plasma concentration (Cmax), and plasma concentration at 24 h post-dose (C24h) were not meaningfully impacted. Islatravir geometric least-squares mean ratios (90% CI) of (islatravir + doravirine)/islatravir for AUC0-24h and Cmax were both close to unity, 1.06 (1.01, 1.12) and 1.08 (0.91, 1.27), respectively. All study regimens were generally well tolerated. CONCLUSION: These results indicate that coadministration of islatravir and doravirine had no clinically meaningful effect on the pharmacokinetics of either drug, and support further clinical investigation of islatravir in combination with doravirine for the treatment of HIV-1 infection.

Isavuconazole for treatment of refractory coccidioidal meningitis with concomitant cerebrospinal fluid and plasma therapeutic drug monitoring.

Coccidioidal meningitis (CM) is a life-threatening infection with limited treatment options. Small series have reported success with isavuconazole; however, limited data exist on cerebrospinal fluid (CSF) penetration. Paired plasma and CSF isavuconazole concentrations were measured. Eleven CSF levels were tested, (7 ventricular, 4 lumbar) in three CM patients. Ventricular CSF levels were undetectable despite detectable plasma levels. All lumbar CSF levels were detectable (mean 1.00 µg/ml). Three pairs of lumbar CSF/plasma concentrations taken within 1 h of each other yielded a mean CSF/plasma ratio of 0.31. Isavuconazole was detectable in lumbar but not ventricular CSF in three patients treated for refractory CM. LAY SUMMARY: Isavuconazole is a triazole antifungal that has been used as salvage therapy in the treatment of coccidioidal meningitis (CM). Few data exist characterizing its concentration in the cerebrospinal fluid (CSF). We report tandem plasma and CSF concentrations of isavuconazole in three patients with CM.

Bioanalysis of selinexor in mouse plasma micro-samples utilizing UPLC-MS/MS.

Selinexor, a first-in-class inhibitor of the nuclear export protein Exportin-1 (XPO1), was recently approved for the treatment of multiple myeloma in combination with dexamethasone, and as monotherapy for diffuse large B-cell lymphoma. To enable investigations of selinexor in mice, we established and validated an ultrahigh-performance liquid chromatography - tandem mass spectrometry (UPLC-MS/MS) assay in the plasma concentration range of 1-1000 ng/mL using plasma microsamples of 5 µL. Protein depletion with acetonitrile was used for efficient isolation of selinexor which was followed by a dilution step, resulting in a scalable sample processing. Quantification was performed with positive electrospray ionization tandem mass spectrometry in the selected reaction monitoring mode. Due to the high sensitivity of the quantification and the scalable sample processing procedure, the assay can be used for different concentration ranges to either further decrease the achievable lower limit of quantification or to reduce the amount of plasma used. The assay showed interday and intraday accuracy of 89.0-109.0% with a corresponding precision ≤ 14.1%. Suitability for investigations of selinexor in small animal experiments was demonstrated by determination of plasma selinexor in mice after oral administration.

A highly sensitive and selective UPLC-MS/MS assay for the determination of enarodustat (JTZ-951) in human plasma.

Enarodustat, a potent, orally bioavailable, selective inhibitor of hypoxia inducible factor-Prolyl hydroxylase (HIF-PH), has been approved recently in Japan for the treatment of anemia in patients with chronic kidney disease (CKD). To evaluate the pharmacokinetics of enarodustat, a bioanalytical assay in human plasma was needed for the quantitation of enarodustat for both healthy subjects and patients with CKD. The UPLC-MS/MS method for the quantitation of enarodustat was initially validated in a bioanalytical laboratory in Japan to support clinical studies conducted in Japan, and then was transferred and validated in a bioanalytical laboratory in United States to support clinical studies conducted here. A cross-validation was successfully performed between the two bioanalytical laboratories using both quality control (QC) samples and incurred study samples. Enarodustat was fortified with its isotopically labeled internal standard in a 25 µL plasma aliquot and extracted with protein precipitation. The chromatographic separation was achieved on an Acquity UPLC BEH C18 (1.7 µm, 2.1 × 50 mm) column with gradient elution. The calibration curve range for the assay was 1.00-500 ng/mL. Assay precision, accuracy, linearity, selectivity, sensitivity and analyte stability covering sample storage and analysis were established. No interferences were observed from medications that may be co-administered along with enarodustat. The validated UPLC-MS-MS method at the US bioanalytical laboratory has been successfully applied to eight clinical studies for the determination of enarodustat concentrations in human plasma for both healthy subjects and patients with CKD.

Establishment and Verification of UPLC-MS/MS Technique for Pharmacokinetic Drug-Drug Interactions of Selinexor with Posaconazole in Rats.

BACKGROUND: A method for the determination of selinexor by UPLC-MS/MS was established to study the effect of posaconazole on the pharmacokinetics of selinexor in rats. METHODS: The experiment rats were divided into group A (0.5% CMC-Na) and group B (posaconazole, 20 mg/kg), 6 rats in each group. 30 minutes after administration of 0.5% CMC-Na or posaconazole, all the rats were given selinexor (8 mg/kg), and plasma samples were collected. The plasma samples underwent acetonitrile protein precipitation, and were separated by UPLC on an Acquity UPLC BEH C18 column with gradient elution. Acetonitrile and 0.1% formic acid were used as the mobile phases. The analyte detection was used a Xevo TQ-S triple quadrupole tandem mass spectrometer and multiple reaction monitoring (MRM) for analyte monitoring. We use acetonitrile for protein precipitation. RESULTS: Selinexor had good linearity (1.0-1000 ng/mL, r2 =0.996 2), and the accuracy and precision, recovery rate and matrix effects(ME) were also met the FDA approval guidelines. Compared with group A, the Cmax, AUC(0-t) and AUC(0-∞) of selinexor in group B increased by 60.33%, 48.28% and 48.27%, and Tmax increased by 53.92%, CLz/F reduced by 32.08%. CONCLUSION: This bioanalysis method had been applied to the study of drug interactions in rats. It was found that posaconazole significantly increased the concentration of selinexor in rats. Therefore, when selinexor and posaconazole are combined, we should pay attention to the possible drug-drug interactions to reduce adverse reactions.

A novel quality by design approach for development and validation of a green reversed-phase HPLC method with fluorescence detection for the simultaneous determination of lesinurad, febuxostat, and diflunisal: Application to human plasma.

A novel and eco-friendly reversed-phase HPLC method with fluorescence detection was developed for simultaneous estimation of two co-administered antigout drugs (lesinurad and febuxostat) with diflunisal as a nonsteroidal anti-inflammatory drug. Unlike routine methodology, the developed method was optimized using analytical quality by design approach. A full factorial design was applied to optimize the effect of variable factors on chromatographic responses. The chromatographic separation was performed using isocratic elution on the Hypersil BDS C18 column at 40°C. The mobile phase consisted of acetonitrile:potassium phosphate buffer (30.0 mM; pH 5.5, 32.2:67.8% v/v) pumped at a flow rate of 1.0 mL/min and injection volume of 20.0 µL was employed. The proposed method was able to separate the ternary mixture in <10 min. The calibration curves of diflunisal, lesinurad, and febuxostat were linear over concentration ranges of 50.0-500.0, 50.0-700.0, and 20.0-700.0 ng/mL, respectively. Recovery percentages ranging from 98.1 to 101.3% with % relative standard deviation of <2% were obtained upon spiking to human plasma samples, indicating high bioanalytical applicability. Furthermore, the method was found to be excellent green when it was assessed according to Green Analytical Procedure Index and analytical Eco-Scale guidelines.

Development and Bio-Analytical Validation of Chromatographic Determination Method of Rufinamide in Presence of its Metabolite in Human Plasma.

Rufinamide (RF), antiepileptic drug, is biotransformed to inactive metabolite. Frequent plasma monitoring is required for dose adjustment. This work is concerned with the development and validation of a sensitive and selective RP-HPLC method for the quantitative determination of RF in spiked human plasma in the presence of its main metabolite. Lacosamide was selected as internal standard. Preparation of plasma samples involved precipitation of plasma proteins using methanol. Isocratic elution mode was applied and the chromatographic separation was performed on Prontosil CN column (5 µm, 250 × 4.6 mm). Good resolution was achieved using acetonitrile: water (10:90, v/v, adjusted with 0.01 N aqueous solution of o-phosphoric acid to pH = 3) as a mobile phase at a flow rate of 1 mL/min, and UV detection was carried out at 210 nm. Linearity was observed over the concentration range of 0.5-50 µg/mL of RF in plasma. Bio-analytical validation of the developed method was carried out in accordance to the European Medicines Agency guidelines. The accuracy ranged from 95.97 to 114.13%, and the coefficient of variation of the assay intra-day and inter-day precision did not exceed 10%. The samples were stable under the employed experimental conditions. In conclusion, the findings of the present study revealed its usefulness for therapeutic drug monitoring, assessment of drug pharmacokinetics and application for bioequivalence study.

Characterization of Isavuconazole serum concentrations after enteral feeding tube administration in a hospitalized cohort: A case series.

WHAT IS KNOWN AND OBJECTIVE: Invasive fungal infections often occur in patients with comorbidities that complicate oral administration. Serum concentrations of isavuconazole were characterized after enteral tube administration. CASE DESCRIPTION: Thirteen of 14 isavuconazole concentrations were >1 mg/dl (median 1.6 mg/dl) among those receiving enteral tube administration, which was comparable to intravenous (median 1.9 mg/dl). Higher concentrations were observed during oral administration (median 3 mg/dl). WHAT IS NEW AND CONCLUSION: Administration of isavuconazole via tube resulted in concentrations comparable to FDA-approved routes of administration. This route may be feasible and appropriate for select patients.

Safety and nonclinical and clinical pharmacokinetics of PC945, a novel inhaled triazole antifungal agent.

PC945 is a novel antifungal triazole formulated for nebulized delivery to treat lung Aspergillus infections. Pharmacokinetic and safety profiles from nonclinical studies and clinical trials in healthy subjects, and subjects with mild asthma were characterized. Toxicokinetics were assessed following daily 2-hour inhalation for 14 days. Potential for drug-drug interactions was evaluated using pooled human liver microsomes. Clinical safety and pharmacokinetics were assessed following (a) single inhaled doses (0.5-10 mg), (b) 7-day repeat doses (5 mg daily) in healthy subjects; (c) a single dose (5 mg) in subjects with mild asthma. Cmax occurred 4 hours (rats) or immediately (dogs) after a single dose. PC945 lung concentrations were substantially higher (>2000-fold) than those in plasma. PC945 only inhibited CYP3A4/5 substrate metabolism (IC50 : 1.33 µM [testosterone] and 0.085 µM [midazolam]). Geometric mean Cmax was 322 pg/mL (healthy subjects) and 335 pg/mL (subjects with mild asthma) 4-5 hours (median tmax ) after a single inhalation (5 mg). Following repeat, once daily inhalation (5 mg), Day 7 Cmax was 951 pg/mL (0.0016 µM) 45 minutes after dosing. Increases in Cmax and AUC0-24h were approximately dose-proportional (0.5-10 mg). PC945 administration was well tolerated in both healthy subjects and subjects with mild asthma. Treatment-emergent adverse events were mild/moderate and resolved before the study ended. No clinically significant lung function changes were observed. PC945 pharmacokinetics translated from nonclinical species to humans showed slow absorption from lungs and low systemic exposure, thereby limiting the potential for adverse side effects and drug interactions commonly seen with systemically delivered azoles.

Comparison of the Pharmacokinetics of RIPK1 Inhibitor GSK2982772 in Healthy Western and Japanese Subjects.

BACKGROUND AND OBJECTIVES: GSK2982772 is an oral small-molecule RIPK1 inhibitor with potential therapeutic efficacy in immune-mediated inflammatory diseases (IMIDs). An inter-ethnic comparison of GSK2982772 pharmacokinetics was conducted based on data from Western (Study 1) and Japanese subjects (Study 2). METHODS: Both studies were single-centre, randomised, double-blind, placebo-controlled studies with objectives to assess the safety and characterise the pharmacokinetics of GSK2982772. Western subjects in Study 1 (NCT03305419), Part A (N = 15), were randomly assigned to receive 120 mg three times daily (TID), 240 mg TID, or 360 mg twice daily (BID) doses of GSK2982772, or placebo (TID or BID) for 1 day. Part B subjects (N = 47) received GSK2982772 120 mg TID, 240 mg TID, or placebo TID for 14 days. Japanese subjects in Study 2 (N = 13) (NCT03590613) were randomly assigned to receive TID doses of GSK2982772 60, 120, 240 mg TID or placebo TID for 1 day. RESULTS: GSK2982772 was well tolerated and adverse events were generally mild. Maximum observed plasma drug concentration (Cmax), time to reach Cmax (Tmax), area under the plasma drug concentration versus time curve after the first GSK2982772 dose (AUC(0-7)) of 120 and 240 mg, and (AUC(0-24)) values for the 120 and 240 mg TID doses over a single day were similar in Japanese and Western subjects. CONCLUSIONS: The pharmacokinetics and tolerability of GSK2982772 were similar between Western and Japanese subjects, justifying inclusion of Japanese subjects in future global clinical studies to assess the therapeutic potential of RIPK1 inhibition for the treatment of IMIDs. Clinical Trials: NCT03305419 and NCT03590613 available from http://www.clinicaltrials.gov .

Novel methodology to perform incurred sample reanalysis on dried blood spot cards: Experimental data using darolutamide and filgotinib.

Different options on performing incurred sample reanalysis (ISR) on dried blood spot (DBS) cards were investigated using drugs belonging to various therapeutic areas: (a) darolutamide (to treat prostate cancer) and (b) filgotinib (to treat rheumatoid arthritis). The proposed novel methodology included the generation of half-DBS and quarter-DBS discs after initial blood collection using the full-DBS discs. Accordingly, blood collection via DBS was performed in male BALB/c mice following intravenous and oral dosing of darolutamide; in male Sprague Dawley rats following intravenous and oral dosing of filgotinib. The ISR data generated from the full-DBS disc, half-DBS disc and quarter-DBS disc were compared for the assessment of the proposed methodology. Quantification of darolutamide and filgotinib was accomplished using liquid chromatography-electrospray ionization/tandem mass spectrometry methods. Darolutamide and filgotinib ISR samples, which were collected and prepared using full-, half- and quarter-DBS discs, met the acceptance criteria for ISR analysis. In conclusion, this is the first report showing a viable tool for the performance of ISR on DBS cards. The use of quarter- or half-DBS discs would aid in not only ISR but also in long-term storage experiments of analytes because it would avoid the need for additional blood sampling in patients.

Initial posaconazole dosing to achieve therapeutic serum posaconazole concentrations among children, adolescents, and young adults receiving delayed-release tablet and intravenous posaconazole.

Posaconazole is a broad-spectrum antifungal used for prophylaxis and treatment of invasive fungal diseases. There are limited data on the optimal dosing, safety, and efficacy of the DRT and IV formulations in immunocompromised pediatric and adolescent patients. We describe our experience including dosing, plasma trough concentrations, safety, and tolerability. Plasma concentrations ≥.7 µg/mL were considered therapeutic for prophylaxis and ≥1.0 µg/mL for treatment. Fifty-four patients (median age of 16 years) received DRT or IV formulations of posaconazole. Thirty-one (57%) patients received posaconazole for treatment and 23 (43%) for prophylaxis. Overall, 36 (67%) patients achieved targeted initial plasma trough concentrations (median 1.3 µg/mL) (Figure 1). The median daily dose among patients <13 years of age who achieved the targeted initial concentrations was 7.3 mg/kg/day for the DRT formulation and 9.8 mg/kg/day for the IV formulation. The median daily dose among patients ≥13 years of age who achieved the targeted initial concentrations was 4.9 mg/kg/day for the DRT formulation and 5.6 mg/kg/day for the IV formulation. Thirty-six patients (67%) developed transaminitis, mostly grade 1. Our observations show that DRT and IV formulations are safe and effective in immunocompromised children, adolescents, and young adults. Higher dosing per body weight of DRT and IV posaconazole may be required in patients <13 years of age compared with patients 13 years of age and older to achieve therapeutic plasma concentrations. [Figure: see text].

Relationship between saliva and plasma rufinamide concentrations in patients with epilepsy.

The assay of saliva samples provides a valuable alternative to the use of blood samples for therapeutic drug monitoring (TDM), at least for certain categories of patients. To determine the feasibility of using saliva sampling for the TDM of rufinamide, we compared rufinamide concentrations in paired samples of saliva and plasma collected from 26 patients with epilepsy at steady state. Within-patient relationships between plasma rufinamide concentrations and dose, and the influence of comedication were also investigated. Assay results in the two tested fluids showed a good correlation (r2  = .78, P < .0001), but concentrations in saliva were moderately lower than those in plasma (mean saliva to plasma ratio = 0.7 ± 0.2). In eight patients evaluated at three different dose levels, plasma rufinamide concentrations increased linearly with increasing dose. Patients receiving valproic acid comedication had higher dose-normalized plasma rufinamide levels than patients comedicated with drugs devoid of strong enzyme-inducing or enzyme-inhibiting activity. Overall, these findings indicate that use of saliva represents a feasible option for the application of TDM in patients treated with rufinamide. Because rufinamide concentrations are lower in saliva than in plasma, a correction factor is needed if measurements made in saliva are used as a surrogate for plasma concentrations.

Lessons from isavuconazole therapeutic drug monitoring at a United Kingdom Reference Center.

We determined isavuconazole serum concentrations for 150 UK patients receiving standard isavuconazole dosing regimens, including serial therapeutic drug monitoring for several patients on prolonged therapy. Mean trough isavuconazole concentrations in these patients were virtually identical to those reported previously from clinical trials, although greater variability was seen in patients below 18 years of age. Serial monitoring in patients receiving prolonged therapy suggested gradual, near-linear accumulation of the drug over many weeks.

Development and Validation of an HPLC Method for Quantification of Filgotinib, a Novel JAK-1 Inhibitor in Mice Plasma: Application to a Pharmacokinetic Study.

Filgotinib is a selective JAK1 (Janus kinase) inhibitor, filed in Japan for the treatment of rheumatoid arthritis. In this paper, we present the data of development and validation of a high-performance liquid chromatography (HPLC) method for the quantitation of filgotinib in mice plasma as per the FDA regulatory guideline. The method involves the extraction of filgotinib along with internal standard (IS, tofacitinib) from mice plasma (100 µL) using ethyl acetate as an extraction solvent. The chromatographic analysis was performed using an isocratic mobile phase comprising 10 mM ammonium acetate (pH 4.5) and acetonitrile (70:30, v/v) at a flow-rate of 0.8 mL/min on a Hypersil Gold C18 column. The UV detection wavelength was set at λmax 300 nm. Filgotinib and the IS eluted at 5.56 and 4.28 min, respectively with a total run time of 10 min. The calibration curve was linear over a concentration range of 0.05 to 5.00 µg/mL (r 2+=≥0.992). The intra- and inter-day precision and accuracy results were within the acceptable limits. Results of stability studies indicated that filgotinib was stable on bench-top, in auto-sampler, up to three freeze/thaw cycles and long-term storage at -80°C. The validated HPLC method was successfully applied to a pharmacokinetic study in mice.

Absorption, distribution, metabolism and excretion of molidustat in healthy participants.

The absorption, distribution, metabolism and excretion of molidustat were investigated in healthy male participants. In study 1, a mass balance study, radiolabelled molidustat 25 mg (3.57 MBq) was administered as an oral solution (n = 4). Following rapid absorption, molidustat-related radioactivity was predominantly distributed in plasma rather than in red blood cells. The total recovery of the administered radioactivity was 97.0%, which was mainly excreted renally (90.7%). Metabolite M-1, produced by N-glucuronidation, was the dominant component in plasma (80.2% of the area under the concentration-time curve for total radioactivity) and was primarily excreted via urine (~85% of dose). Only minor amounts of unchanged molidustat were excreted in urine (~4%) and faeces (~6%). Study 2 investigated the absolute bioavailability and pharmacodynamics of molidustat (part 1, n = 12; part 2, n = 16). Orally administered molidustat immediate release tablets had an absolute bioavailability of 59%. Following intravenous administration (1, 5 and 25 mg), total body clearance of molidustat was 28.7-34.5 L/h and volume of distribution at steady state was 39.3-50.0 L. All doses of molidustat transiently elevated endogenous erythropoietin levels, irrespective of the route of administration. Molidustat was considered safe and well tolerated at the administered doses.