New perspectives for the therapeutic drug monitoring of tacrolimus: Quantification in volumetric DBS based on an automated extraction and LC-MS/MS analysis

Review: the role of automation in improving the performance and throughput of microsample bioanalysis

BACKGROUND

Microsampling is one of the most dynamic and rapidly evolving topics in bioanalysis. It can provide numerous advantages in comparison to traditional biological fluid sampling (safety and analyte stability, feasible shipping, lower storage expenses and increased environmental friendliness). All these advantages can be put to ideal use if microsampling is coupled to advanced automation. Most modern microsampling techniques are designed for optimal automatability of the sampling procedure, or of any of the subsequent analytical workflow steps, so that the usual advantages of the former can be enhanced by increased throughput, better safety and lower per-analysis expenses. However, finding relevant information on recent advances in automation for the bioanalysis of microsamples is still a challenging task.

RESULTS

In this review paper with 91 references, the most recent and relevant applications of full automation and semi-automation in biological microsample analysis are presented, with notes on the advantages and limitations of each approach. Some less recent examples are also presented, providing context or insight into the evolution of subsequent developments. This unique approach allows a better understanding of the close intertwining and complementarity of microsampling, automation and miniaturised sample preparation, an integration that is essential to ensure optimal and reliable results. Differences between classical and advanced microsampling techniques regarding their performance related to overall process automation are clearly laid out. Ample space is reserved for discussion on the most recent trends and what the authors believe will be the most important future developments.

SIGNIFICANCE

This review paper shows for the first time how coupling microsampling to analytical workflow automation could be the tipping point that will help microsampling become fully established in routine bioanalysis. Most disadvantages of microsampling can be either alleviated, outright solved or made irrelevant by automation, and this unprecedented development has the potential to revolutionise an entire research and application field. This is true in most use cases, including therapeutic drug monitoring, forensics, anti-doping and preclinical, clinical and toxicological studies.

An Offline SPE-LC-MS/MS Method for Simultaneous Quantification of Tacrolimus, Cyclosporine A, Kynurenine, Tryptophan, and Creatinine Using Volumetric Absorptive Microsampling Device Mitra

BACKGROUND

Therapeutic drug monitoring of immunosuppressants is critical in balancing insufficient immunosuppression due to underdosing, and severe adverse effects due to overdosage. For a more comprehensive therapeutic drug monitoring and follow-up of transplant patients, the aim was to develop a liquid chromatography-tandem mass spectrometry method for the simultaneous quantification of tacrolimus, cyclosporine A, tryptophan, kynurenine, and creatinine using a volumetric absorptive microsampling device.

METHODS

Venous and capillary blood samples were simultaneously collected using a volumetric absorptive microsampling device called Mitra. The method involved protein precipitation followed by offline solid-phase extraction using a positive pressure manifold. Chromatographic separation was achieved by a formic acid-ammonium formate-methanol gradient on a Synergi Polar reversed-phase column. Multiple reaction monitoring in the positive ion mode and stable isotope-labeled internal standards were used for quantification. Validation was performed according to the European Medicines Agency and US Food and Drug Administration (FDA) guidelines.

RESULTS

Validation was successful, meeting European Medicines Agency and FDA guidelines. Investigation of selectivity, accuracy, and precision met the required criteria of a deviation <15%. Internal standards successfully compensated potential matrix effects. A comparison of 26 anonymized samples from transplant patients on Mitra with venous blood controls demonstrated the method's suitability.

CONCLUSIONS

For the first time, we herein describe a liquid chromatography-tandem mass spectrometry method for the simultaneous quantification of tacrolimus, cyclosporine A, tryptophan, kynurenine, and creatinine on Mitra. Self-collection of samples may facilitate therapeutic monitoring. Simultaneous determination of creatinine may help monitor kidney function, while tryptophan and kynurenine may serve as a biomarker for early detection of transplant rejection.

Rapid determination of phenylalanine and tyrosine in volumetrically collected dried blood spots using fully automated processing and analysis by capillary electrophoresis

An off-the-shelf Agilent 7100 capillary electrophoresis (CE) instrument was employed for the automated processing and analysis of dried blood spots (DBSs) collected by Capitainer®B volumetric devices. Solutions for DBS elutions were transferred directly into CE vials through a separation capillary by the application of an auxiliary nitrogen gas connected to the external pressure line of the CE instrument. This allowed for liquid handling at pressures up to 15 bar and enabled the use of a single capillary for rapid DBS processing and efficient CE separations. The resulting DBS eluates were at-line injected into a short capillary end, which served for improved instrumental simplicity and short CE analysis times. The current set-up necessitated neither hardware nor software adjustments of the CE instrument, except for the connection of a gas cylinder to an in-built connector. The novel features presented in this study (DBSs with exact blood volumes, high external pressures, and short-end injections) were used for the automated determination of clinically relevant markers, phenylalanine (Phe) and tyrosine (Tyr), in DBS samples. Sensitive and selective Phe and Tyr quantification was achieved by CE-UV in 375 mM formic acid and 0.01 % (v/v) Tween 20 (pH 2.09) as a background electrolyte. The total processing and analysis times per one DBS were <1.5 and 4.5 min, respectively, in a sequence of 36 DBSs, and resulted in a sample throughput of >10 DBSs per hour. The intra- and inter-day repeatability values were better than 5.9 and 1.1 % RSD for peak areas and migration times, respectively, and calibration curves were linear in the 20-3000 μM (Phe) and 20-250 μM (Tyr) range (R2 ≥ 0.9973). The limits of detection were ≤2 μM and enabled the determination of endogenous Phe and Tyr concentrations as well as elevated Phe concentrations and Phe/Tyr ratios, which are the typical markers for neonatal phenylketonuria screening.

Microsampling techniques and patient-centric therapeutic drug monitoring of immunosuppressants

Immunosuppressive pharmacotherapy after solid organ transplantation (SOT) requires therapeutic drug monitoring (TDM) for therapy individualization. The venous whole blood is still considered as routine matrix for monitoring immunosuppressive drug concentration. On the other hand, as an alternative, capillary blood collected using noninvasive sampling is convergent with a patient-centric approach. Despite their disadvantages regarding sample homogeneity and the hematocrit effect, well-known dried blood spot techniques have shown promising results. Volumetric absorptive microsampling (VAMS) and quantitative dried blood spot (qDBS) have successfully eliminated these unfavorable biased elements. Microsampling can be used in transplant recipients' care, mainly due to long-term therapy under control drug concentrations and the long distance between the place of the patient's residence and the diagnostic laboratory in the transplant center. The study aimed to discuss the clinical consequences of implementing microsampling techniques for TDM of immunosuppressants. Additionally, we have discussed the 'hot topics' in microsampling: home-based self-sampling, adherence to therapy monitoring, and drug concentration conversion to estimated traditional matrices. Finally, based on our experience and current practice, we propose best practices for microsampling implementation from bench to bedside. Microsampling techniques can potentially revolutionise immunosuppressive pharmacotherapy by enabling patient-centric individualisation in various subpopulations, significantly improving post-transplant care.

Getting Tacrolimus Dosing Right

ABSTRACT

Tacrolimus (TAC) dosing is typically guided by the trough concentration (C0). Yet, significant relationships between TAC C0 and clinical outcomes have seldom been reported or only with adverse events. Large retrospective studies found a moderate correlation between TAC C0 and the area under the curve (AUC), where, for any given C0 value, the AUC varied 3- to 4-fold between patients (and vice versa). However, no randomized controlled trial evaluating the dose adjustment based on TAC AUC has been conducted yet. A few observational studies have shown that the AUC is associated with efficacy and, to a lesser extent, adverse effects. Other studies showed the feasibility of reaching predefined target ranges and reducing underexposure and overexposure. TAC AUC 0-12 h is now most often assessed using Bayesian estimation, but machine learning is a promising approach. Microsampling devices are well accepted by patients and represent a valuable alternative to venous blood sample collection during hospital visits, especially when a limited sampling strategy is required. As AUC monitoring cannot be proposed very frequently, C0 monitoring has to be used in the interim, which has led to fluctuating doses in patients with an AUC/C0 ratio far from the population mean, because of different dose recommendations between the 2 biomarkers. We proposed estimating the individual AUC/C0 ratio and derived individual C0 targets to be used in between or as a replacement for AUC monitoring. Existing technology and evidence are now sufficient to propose AUC monitoring interspersed with individualized-C0 monitoring for all patients with kidney transplants while collecting real-world data to strengthen the evidence.

A Validated Assay to Quantify Osimertinib and Its Metabolites, AZ5104 and AZ7550, from Microsampled Dried Blood Spots and Plasma

BACKGROUND

Osimertinib is an oral small-molecule tyrosine kinase receptor inhibitor used to treat non-small cell lung cancer (NSCLC) with a sensitizing epidermal growth factor receptor mutation. Patients may experience drug toxicity and require dose deescalation. The study aimed to quantitate osimertinib and its 2 active metabolites, AZ5104 and AZ7550, in microsampled dried blood spots (DBS) collected from patients with NSCLC using a hemaPEN device and compare them with plasma drug levels.

METHODS

A 6-min ultrahigh-performance liquid chromatography-tandem mass spectrometry method was developed and validated using plasma and DBS. The accuracy, selectivity, matrix effect, recovery, and stability were assessed using bioanalytical validation criteria. The hematocrit effect was investigated in DBS. Drug levels were measured in 15 patients with NSCLC, and the Bland-Altman method was used to compare measurements between plasma and DBS.

RESULTS

The validated assay determined accurate and precise quantities, respectively, for osimertinib in both plasma (93.2%-99.3%; 0.2%-2.3%) and DBS (96.7%-99.6%; 0.5%-10.3%) over a concentration of 1-729 ng/mL. The osimertinib metabolites, AZ5104 and AZ7550, were similarly validated in accordance with bioanalytical guidelines. For 30%-60% patient hematocrit, no hematocrit bias was observed with DBS for all analytes. The Bland-Altman method showed high concordance between plasma and DBS analyte levels. Stability experiments revealed that osimertinib and its metabolites were poorly stable in plasma at room temperature, whereas all analytes were stable in DBS for 10 days at room temperature.

CONCLUSIONS

The measurement of osimertinib, AZ5104, and AZ7550 from hemaPEN microsampled DBS is a convenient and reliable approach for therapeutic drug monitoring that produces measurements consistent with plasma drug levels.

Targeted and untargeted metabolomics and lipidomics in dried blood microsampling: Recent applications and perspectives

Blood microsampling (BµS) offers an alternative to conventional methods that use plasma or serum for profiling human health, being minimally invasive and cost effective, especially beneficial for vulnerable populations. We present a non-systematic review that offers a synopsis of the analytical methods, applications and perspectives related to dry blood microsampling in targeted and untargeted metabolomics and lipidomics research in the years 2022 and 2023. BµS shows potential in neonatal and paediatric studies, therapeutic drug monitoring, metabolite screening, biomarker research, sports supervision, clinical disorders studies and forensic toxicology. Notably, dried blood spots and volumetric absorptive microsampling options have been more extensively studied than other volumetric technologies. Therefore, we suggest that a further investigation and application of the volumetric technologies will contribute to the use of BµS as an alternative to conventional methods. Conversely, we support the idea that harmonisation of the analytical methods when using BµS would have a positive impact on its implementation.