Exploratory study of total and free prednisolone plasma exposure and cushingoid appearance, quality of life and biochemical toxicity in adult male kidney transplant recipients

Fingerprick Microsampling Methods Can Replace Venepuncture for Simultaneous Therapeutic Drug Monitoring of Tacrolimus, Mycophenolic Acid, and Prednisolone Concentrations in Adult Kidney Transplant Patients

BACKGROUND

Kidney transplant patients undergo repeated and frequent venepunctures during allograft management. Microsampling methods that use a fingerprick draw of capillary blood, such as dried blood spots (DBS) and volumetric absorptive microsamplers (VAMS), have the potential to reduce the burden and volume of blood loss with venepuncture.

METHODS

This study aimed to examine microsampling approaches for the simultaneous measurement of tacrolimus, mycophenolic acid, mycophenolic acid glucuronide (MPAG), and prednisolone drug concentrations compared with standard venepuncture in adult kidney transplant patients. DBS and VAMS were simultaneously collected with venepuncture samples from 40 adult kidney transplant patients immediately before and 2 hours after immunosuppressant dosing. Method comparison was performed using Passing-Bablok regression, and bias was assessed using Bland-Altman analysis. Drug concentrations measured through microsampling and venepuncture were also compared by estimating the median prediction error (MPE) and median absolute percentage prediction error (MAPE).

RESULTS

Passing-Bablok regression showed a systematic difference between tacrolimus DBS and venepuncture [slope of 1.06 (1.01-1.13)] and between tacrolimus VAMS and venepuncture [slope of 1.08 (1.03-1.13)]. Tacrolimus values were adjusted for this difference, and the corrected values showed no systematic differences. Moreover, no systematic differences were observed when comparing DBS or VAMS with venepuncture for mycophenolic acid and prednisolone. Tacrolimus (corrected), mycophenolic acid, and prednisolone microsampling values met the MPE and MAPE predefined acceptability limits of <15% when compared with the corresponding venepuncture values. DBS and VAMS, collected in a controlled environment, simultaneously measured multiple immunosuppressants.

CONCLUSIONS

This study demonstrates that accurate results of multiple immunosuppressant concentrations can be generated through the microsampling approach, with a preference for VAMS over DBS.

Sensitive quantification of free pazopanib using ultra-high performance liquid chromatography coupled to tandem mass spectrometry and assessment of clinical application

Pazopanib is widely used to treat renal cell carcinomas and soft tissue tumors in Japan. Although several reports demonstrated the usefulness of therapeutic drug monitoring (TDM) of pazopanib, those studies measured only total pazopanib concentration. For drugs with high protein binding rates such as pazopanib, measuring free concentrations may be clinically more useful than measuring total concentrations. In this study, we aimed to develop a high-throughput method for quantification of free pazopanib in human plasma using ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). Free pazopanib was separated by ultrafiltration. After a simple solid-phase extraction step using a 96-well plate, pazopanib was analyzed by UHPLC-MS/MS in positive electrospray ionization mode. The novel method fulfilled the requirements of the US Food and Drug Administration guidelines for assay validation, and the lower limit of quantification was 0.05 ng/mL. The calibration curve was linear over the concentration range of 0.05-50 ng/mL. The average recovery rate was 66.9 ± 2.1% (mean ± SD). The precision was below 7.02%, and accuracy was within 10.60% across all quality control levels. Matrix effect varied between 44.4% and 60.4%. This assay was successfully applied to measure trough free pazopanib concentrations in three patients treated with pazopanib for soft tissue tumors. We succeeded to develop a novel high-throughput UHPLC-MS/MS method for quantification of free pazopanib in human plasma. This method can be applied to TDM for patients receiving pazopanib in the clinical setting.

A randomised controlled unblinded multicentre non-inferiority trial with activated vitamin D and prednisolone treatment in patients with minimal change nephropathy (ADAPTinMCN)

BACKGROUND

Minimal change nephropathy (MCN) is a common cause of nephrotic syndrome in both adults and children. International guidelines recommend treatment with prednisolone 1 mg/kg/day to adults. This dose is derived from an empirically established dose in children, although children generally attain remission faster and relapse more rapidly than adults. Prednisolone is associated with multiple and serious adverse events. Activated vitamin D has been shown to reduce albuminuria in other glomerular renal diseases with a minimum of adverse events. This study tests the hypothesis that a new treatment regimen in MCN combining reduced dose prednisolone and active vitamin D is as efficient in inducing remission and has fewer and less severe adverse events than standard prednisolone. Furthermore, we aim to establish models allowing for more personalized medicine based on assessment of the individual's prednisolone metabolism.

METHODS

A randomised controlled multicentre non-inferior unblinded trial including 96 adult, incident patients with biopsy-proven MCN, albuminuria > 3 g/day, and an estimated glomerular filtration rate (eGFR) > 30 ml/min from renal departments in Denmark. Patients are randomised to standard prednisolone (1 mg/kg/day) or reduced prednisolone (0.5 mg/kg/day) and alfacalcidol (0.5 μg/day). The primary outcome is the rate of remissions after 16 weeks and the time from diagnosis to remission. The study will include a saliva test to characterise prednisolone pharmacokinetics and compare them to genetic variations in specific liver enzymes responsible for prednisolone metabolism.

DISCUSSION

Reducing the prednisolone dose is expected to reduce the number of severe adverse events. This study will examine if reduced prednisolone dose with active vitamin D but without additional immunosuppression is feasible in the treatment of MCN and will reduce the number of adverse events. The findings can potentially change current guidelines for treatment of MCN in adults. Additional outcomes on inter-individual pharmacokinetic and metabolic variations may allow for a more personalised treatment strategy.

TRIAL REGISTRATION

EudraCT 2017-001206-16, ClinicalTrials.gov NCT03210688 . Registered on June 3, 2017.

Development and validation of sensitive and selective quantification of total and free daptomycin in human plasma using ultra-performance liquid chromatography coupled to tandem mass spectrometry

Recently, several studies on pharmacokinetics parameters of daptomycin reported that plasma trough concentration was linked to efficacy and adverse effects, suggesting the usefulness of therapeutic drug monitoring. Although some methods for determining total daptomycin concentration using liquid chromatography coupled to tandem mass spectrometry were established previously, no sensitive quantification method for free drug concentration was established. In this study, we aimed to develop a quantitative method of measuring both total and free daptomycin concentrations using ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS), by which both trough and maximum concentrations can be measured. Plasma samples were prepared by solid phase extraction. Free fractions were obtained by ultrafiltration. The assay fulfilled the requirements of US Food and Drug Administration and the European Medicines Agency for assay validation. The methods for total and free drug showed good fit over wide ranges of 0.5-200 and 0.04-40 μg/mL, with lower limits of quantitation of 0.5 and 0.04 μg/mL, respectively. Recovery rate of free daptomycin from ultrafiltration was approximately 100%. Extraction recovery rates of total and free drug measurements ranged from 57.1 to 67.4% and 54.6 to 62.3%, while matrix effect varied between 111.9 and 118.7% and 104.0 and 127.1%, respectively. The maximum and trough concentrations of total and free daptomycin in plasma from two patients in intensive care unit were successfully determined, demonstrating the feasibility of clinical application of the novel methods for determining plasma total and free daptomycin concentrations. In conclusion, we succeeded to develop a sensitive and selective method using UPLC-MS/MS for quantitative measurement of total and free daptomycin concentrations in plasma.

Sensitive and selective quantification of total and free itraconazole and hydroxyitraconazole in human plasma using ultra-performance liquid chromatography coupled to tandem mass spectrometry

OBJECTIVES

Protein-free (unbound) drug concentrations have been reported to be better biomarker of pharmacodynamics compared with total drug concentrations. In this study, we developed and validated an assay for the quantification of total and free itraconazole and hydroxyitraconazole, a main metabolite with antifungal activity, in human plasma using ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS).

DESIGN & METHODS

Plasma sample was ultra-filtrated for the measurement of free itraconazole and hydroxyitraconazole concentrations. The samples were prepared by solid phase extraction, and then subject to UPLC-MS/MS quantification.

RESULTS

The assay fulfilled the requirements of the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) guidelines for assay validation, with a lower limit of quantification of 10ng/mL for total itraconazole and hydroxyitraconazole, and 0.1 and 0.5ng/mL for free itraconazole and hydroxyitraconazole, respectively. Recovery rates of total itraconazole and hydroxyitraconazole from whole plasma ranged from 53.3% to 64.0%, and recovery rates of free itraconazole and hydroxyitraconazole from ultrafiltrated plasma ranged from 81.6% to 98.7%. Matrix effect varied between 79.1% and 109.4% for total itraconazole and hydroxyitraconazole, and between 81.3% and 99.7% for free itraconazole and hydroxyitraconazole. The assay was successfully applied to therapeutic drug monitoring of itraconazole in three patients with chronic progressive pulmonary aspergillosis or invasive pulmonary aspergillosis. Plasma free hydroxyitraconazole concentrations were 8.1-, 23.3-, and 51.1-fold higher than plasma free itraconazole concentrations in the three patients.

CONCLUSIONS

A method for sensitive and selective quantification of plasma total and free itraconazole and hydroxyitraconazole concentrations was developed using UPLC-MS/MS. Free hydroxyitraconazole concentration may be most important in therapeutic drug monitoring of itraconazole.