Surface-Enhanced Raman Spectroscopy Combined with Multivariate Analysis for Fingerprinting Clinically Similar Fibromyalgia and Long COVID Syndromes

Fibromyalgia (FM) is a chronic central sensitivity syndrome characterized by augmented pain processing at diffuse body sites and presents as a multimorbid clinical condition. Long COVID (LC) is a heterogenous clinical syndrome that affects 10-20% of individuals following COVID-19 infection. FM and LC share similarities with regard to the pain and other clinical symptoms experienced, thereby posing a challenge for accurate diagnosis. This research explores the feasibility of using surface-enhanced Raman spectroscopy (SERS) combined with soft independent modelling of class analogies (SIMCAs) to develop classification models differentiating LC and FM. Venous blood samples were collected using two supports, dried bloodspot cards (DBS, n = 48 FM and n = 46 LC) and volumetric absorptive micro-sampling tips (VAMS, n = 39 FM and n = 39 LC). A semi-permeable membrane (10 kDa) was used to extract low molecular fraction (LMF) from the blood samples, and Raman spectra were acquired using SERS with gold nanoparticles (AuNPs). Soft independent modelling of class analogy (SIMCA) models developed with spectral data of blood samples collected in VAMS tips showed superior performance with a validation performance of 100% accuracy, sensitivity, and specificity, achieving an excellent classification accuracy of 0.86 area under the curve (AUC). Amide groups, aromatic and acidic amino acids were responsible for the discrimination patterns among FM and LC syndromes, emphasizing the findings from our previous studies. Overall, our results demonstrate the ability of AuNP SERS to identify unique metabolites that can be potentially used as spectral biomarkers to differentiate FM and LC.

Validation of low-volume sampling devices for pharmacokinetic analysis: technical and logistical challenges and solutions

While low-volume sampling technologies offer numerous advantages over venipuncture, implementation in clinical trials poses technical and logistical challenges. Bioanalytical methods were validated for measuring the concentration of crenezumab and etrolizumab in dried blood samples collected using Mitra and Tasso-M20. The data generated demonstrate that the concentrations of crenezumab and etrolizumab in dried blood collected by either device could be determined using calibrators prepared in serum. Drug concentrations from dried blood were converted to serum concentrations using patient hematocrit levels. Contract Research Organization experience in sample handling and analysis allowed us to compare differences between various low-volume sampling technologies. This study evaluated challenges and presented potential solutions for use of different low-volume sampling technologies for pharmacokinetic analysis.

Volumetric Absorptive Microsampling in the Analysis of Endogenous Metabolites

Volumetric absorptive microsampling (VAMS) has arisen as a relevant tool in biological analysis, offering simplified sampling procedures and enhanced stability. Most of the attention VAMS has received in the past decade has been from pharmaceutical research, with most of the published work employing VAMS targeting drugs or other exogenous compounds, such as toxins and pollutants. However, biomarker analysis by employing blood microsampling has high promise. Herein, a comprehensive review on the applicability of VAMS devices for the analysis of endogenous metabolites/biomarkers was performed. The study presents a full overview of the analysis process, incorporating all the steps in sample treatment and validation parameters. Overall, VAMS devices have proven to be reliable tools for the analysis of endogenous analytes with biological importance, often offering improved analyte stability in comparison with blood under ambient conditions as well as a convenient and straightforward sample acquisition model.

Analytical and Clinical Validation of Assays for Volumetric Absorptive Microsampling (VAMS) of Drugs in Different Blood Matrices: A Literature Review

Volumetric absorptive microsampling (VAMS) is the newest and most promising sample-collection technique for quantitatively analyzing drugs, especially for routine therapeutic drug monitoring (TDM) and pharmacokinetic studies. This technique uses an absorbent white tip to absorb a fixed volume of a sample (10-50 µL) within a few seconds (2-4 s), is more flexible, practical, and more straightforward to be applied in the field, and is probably more cost-effective than conventional venous sampling (CVS). After optimization and validation of an analytical method of a drug taken by VAMS, a clinical validation study is needed to show that the results by VAMS can substitute what is gained from CVS and to justify implementation in routine practice. This narrative review aimed to assess and present studies about optimization and analytical validation of assays for drugs taken by VAMS, considering their physicochemical drug properties, extraction conditions, validation results, and studies on clinical validation of VAMS compared to CVS. The review revealed that the bio-analysis of many drugs taken with the VAMS technique was optimized and validated. However, only a few clinical validation studies have been performed so far. All drugs that underwent a clinical validation study demonstrated good agreement between the two techniques (VAMS and CVS), but only by Bland-Altman analysis. Only for tacrolimus and mycophenolic acid were three measurements of agreement evaluated. Therefore, VAMS can be considered an alternative to CVS in routine practice, especially for tacrolimus and mycophenolic acid. Still, more extensive clinical validation studies need to be performed for other drugs.

Applications of Volumetric Absorptive Microsampling Technique: A Systematic Critical Review

METHODS

A novel microsampling device called Volumetric Absorptive microsampling (VAMS), developed in 2014, appears to have resolved the sample inhomogeneity inherent to dried blood spots, with improved precision in the volume of sample collected for measuring drug concentration. A literature search was conducted to identify several analytical and pharmacokinetic studies that have used VAMS in recent years.

RESULTS

The key factors for proper experimental design and optimization of the extraction of drugs and metabolites of interest from the device were summarized. This review focuses on VAMS and elaborates on bioanalytical factors, method validation steps, and scope of this technique in clinical practice.

CONCLUSIONS

The promising microsampling method VAMS is especially suited for conducting pharmacokinetic studies with very small volumes of blood, especially in special patient populations. Clinical validation of every VAMS assay must be conducted prior to the routine practical implementation of this method.

Volumetric absorptive microsampling-LC-MS/MS assays for quantitation of giredestrant in dried human whole blood

Volumetric absorption microsampling devices offer minimally invasive and user-friendly collection of capillary blood in volumes as low as 10 μl. Herein we describe the assay validation for determination of the selective estrogen receptor degrader giredestrant (GDC-9545) in dried human whole blood collected using the Mitra^® and Tasso-M20 devices. Both LC-MS/MS assays met validation acceptance criteria for the linear range 1-1000 ng/ml giredestrant. Mitra and Tasso-M20 samples were stable for 84 and 28 days at ambient conditions, respectively, and for 7-9 days at 40 and -70°C. Blood hematocrit, hyperlipidemia and anticoagulant did not impact quantitation of giredestrant. These validated assays are suitable for the determination of giredestrant in dried blood samples collected using Mitra and Tasso-M20 microsampling devices.

Rational Alteration of Pharmacokinetics of Chiral Fluorinated and Deuterated Derivatives of Emixustat for Retinal Therapy

Recycling of all-trans-retinal to 11-cis-retinal through the visual cycle is a fundamental metabolic pathway in the eye. A potent retinoid isomerase (RPE65) inhibitor, (R)-emixustat, has been developed and tested in several clinical trials; however, it has not received regulatory approval for use in any specific retinopathy. Rapid clearance of this drug presents challenges to maintaining concentrations in eyes within a therapeutic window. To address this pharmacokinetic inadequacy, we rationally designed and synthesized a series of emixustat derivatives with strategically placed fluorine and deuterium atoms to slow down the key metabolic transformations known for emixustat. Crystal structures and quantum chemical analysis of RPE65 in complex with the most potent emixustat derivatives revealed the structural and electronic bases for how fluoro substituents can be favorably accommodated within the active site pocket of RPE65. We found a close (∼3.0 Å) F-π interaction that is predicted to contribute ∼2.4 kcal/mol to the overall binding energy.

Assessment of low volume sampling technologies: utility in nonclinical and clinical studies

Background: Low volume sampling technologies have come a long way; however, their uptake has been slow due to logistical and perceived implementation challenges. Additional studies are needed to overcome these barriers. Materials & methods/results: Here we present two studies where different sampling technologies were evaluated to determine the feasibility of their implementation. First, we evaluated pharmacokinetic profiles for anti-gD in rats using three tail bleed sampling methods, glass capillary tubes, Shimadzu MSW2^® and the Neoteryx Mitra^® microsampler. Second, we evaluated two low volume-sampling methods to measure drug levels from patients treated with anti-A therapeutic. This evaluation used whole blood finger pricks for Neoteryx Mitra and plasma from capillary blood using TASSO OnDemand technology to compare results to established venipuncture collection method. Conclusion: These studies evaluate the feasibility and considerations for implementation of different low volume sampling technologies.

Volumetric Absorptive Microsampling as a Sampling Alternative in Clinical Trials and Therapeutic Drug Monitoring During the COVID-19 Pandemic: A Review

An infectious disease, COVID-19, caused by a new type of coronavirus, has been discovered recently. This disease can cause respiratory distress, fever, and fatigue. It still has no drug and vaccine for treatment and prevention. Therefore, WHO recommends that people should stay at home to reduce disease transmission. Due to the quarantine, FDA stated that this could hamper drug development clinical trial protocols. Hence, an alternative sampling method that can be applied at home is needed. Currently, volumetric absorptive microsampling (VAMS) has become attention in its use in clinical and bioanalytical fields. This paper discusses the advantages and challenges that might be found in the use of VAMS as an alternative sampling tool in clinical trials and therapeutic drug monitoring (TDM) during the COVID-19 pandemic. VAMS allows easy sampling, can be done at home, storage and delivery at room temperature, and the volume taken is small and minimally invasive. VAMS is also able to absorb a fixed volume that can increase the accuracy and precision of analytical methods, and reduce the hematocrit effects (HCT). The use of VAMS is expected to be implemented immediately in clinical trials and TDM during this pandemic considering the benefits it has.

Technological advancement in dry blood matrix microsampling and its clinical relevance in quantitative drug analysis

In the past few decades, dried blood matrix biosampling has witnessed a marvelous interest among the researcher due to its user-friendly operation during blood sampling in preclinical and clinical applications. It also complies with the basic 3Rs (reduce, reuse and recycle) philosophy. Because of comparative simplicity, a huge number of researchers are paying attention to its technological advancements for widespread application in the bioanalysis and diagnosis arena. In this review, we have explained different approaches to be considered during dried blood matrix based microsampling including their clinical relevance in therapeutic drug monitoring. We have also discussed various strategies for avoiding and minimizing major unwanted analytical interferences associated with this technique during drug quantification. Further, various recent technological advancement in microsampling devices has been discussed correlating their clinical applications.

Novel LC-MS/MS method for the determination of selumetinib (AZD6244) in whole blood collected with volumetric absorptive microsampling

Aim: A method has been developed and validated for quantitation of selumetinib in human whole blood collected using a Mitra™ volumetric absorptive microsampling device. This device is patient-friendly, affording less-invasive sampling with broad applicability to clinical and diagnostic applications - specifically in pediatric populations. Materials & methods: In this method, drug is extracted from the Mitra device via sonication in methanol: Ammonium hydroxide, then analyzed by LC-MS/MS. The linear range for selumetinib analysis is 2.00-2000 ng/ml. Results: All validation parameters met acceptance criteria established in agreement with current regulatory guidance for bioanalytical method validation. The stability of selumetinib in Mitra tips was established at both ambient and frozen conditions. Conclusion: A simple method has been developed and validated for determination of selumetinib from human whole blood, collected using volumetric absorptive microsampling and analyzed by LC-MS/MS.

Application of a Volumetric Absorptive Microsampling Device to a Pharmacokinetic Study of Tacrolimus in Rats: Comparison with Wet Blood and Plasma

BACKGROUND AND OBJECTIVES

Volumetric absorptive microsampling (VAMS) devices are useful for sampling a smaller volume of blood from rodents in the preclinical setting. In the present study, we evaluated the proof of concept of a VAMS device by comparing the pharmacokinetic data of tacrolimus in rats among dried blood in VAMS, wet blood, and plasma.

METHODS

Tacrolimus was administered orally, to rats, at a dose of 10 mg/kg. Only 10 μL aliquots of blood were absorbed by VAMS devices at designated time points. Tacrolimus was extracted with a methanol-water mixture (1:1, v/v) via sonication. Tacrolimus levels in wet blood (10 μL) and plasma (10 μL) were quantified after protein precipitation.

RESULTS

Tacrolimus in VAMS devices was quantifiable from 0.2 ng/mL using high-performance liquid chromatography with tandem mass spectrometer. Accuracy and precision were within the acceptance criteria. Bland-Altman plots showed that tacrolimus concentrations in VAMS devices were similar to those in wet blood, regardless of tacrolimus levels. On the other hand, tacrolimus levels in plasma were different from those in VAMS devices, especially at lower concentrations, likely due to partition of tacrolimus to blood cells. However, pharmacokinetic parameters were comparable among the three matrices.

CONCLUSIONS

Collectively, these findings suggest that the VAMS device can be a useful device for pharmacokinetic studies in rats.

Validation and reproducibility of an LC-MS/MS method for emixustat and its three deaminated metabolites in human plasma

Aim: A sensitive method to quantify emixustat and its rapidly formed three major deaminated metabolites in human plasma was necessary to determine exposure in clinical trials. Methods: An LC-MS/MS method was validated for accuracy and precision, linearity, carry over, selectivity, recovery, matrix effects, hematocrit effects and stability. Results: A quantitative procedure for the determination of emixustat, ACU-5116, ACU-5124 and ACU-5149 in human plasma over the concentration range of 0.0500/1.00/1.00/1.00-10.0/1000/1000/1000 ng/ml, was successfully validated and has been used to successfully analyze samples in three clinical trials. Incurred sample reanalysis was performed for all four analytes in each study with >92% of the repeat results and original results within 20% of the mean of the two values.

Tutorial: Volumetric absorptive microsampling (VAMS)

Volumetric absorptive microsampling (VAMS) is a recent microsampling technique used to obtain dried specimens of blood and other biological matrices for application to a plethora of bioanalytical purposes. As such, it can be likened to dried blood spot (DBS) technique that has been in wide use for the last 40 years. However, VAMS promises to bring some significant advantages over DBS, related to sampling volume accuracy, haematocrit (HCT) dependence, pre-treatment and automation. Although some aspects still need to be investigated in depth, VAMS is increasingly recognised as a viable alternative to DBS and other dried microsampling techniques. In this tutorial, different aspects of VAMS approach are described and discussed, presenting the procedures adopted and the results obtained by those authors who have developed this kind of analytical workflow in the last few years. Hopefully, this will help other scientists to find new solutions to old and recent problems related to microsampling and to produce new, sound and interesting science in this field.

Extractability-mediated stability bias and hematocrit impact: High extraction recovery is critical to feasibility of volumetric adsorptive microsampling (VAMS) in regulated bioanalysis

Volumetric absorptive microsampling (VAMS), a new microsampling technique, was evaluated for its potential in supporting regulated bioanalysis. Our initial assessment with MK-0518 (raltegravir) using a direct extraction method resulted in 45-52% extraction recovery, significant hematocrit (Ht) related bias, and more importantly, unacceptable stability (>15% bias from nominal concentration) after 7-day storage. Our investigation suggested that the observed biases were not due to VAMS absorption, sampling techniques, lot-to-lot variability, matrix effect, and/or chemical stability of the compound, but rather the low extraction recovery. An effort to improve assay recovery led to a modified liquid-liquid extraction (LLE) method that demonstrated more consistent performance, minimal Ht impact (Ht ranged from 20 to 65%), and acceptable sample stability. The same strategy was successfully applied to another more hydrophilic model compound, MK-0431 (sitagliptin). These results suggest that the previously observed Ht effect and "instability" were in fact due to inconsistent extractability, and optimizing the extraction recovery to greater than 80% was critical to ensure VAMS performance. We recommend adding Ht-independent recovery as part of feasibility assessment to de-risk the long-term extractability-mediated stability bias before implementing VAMS in regulated bioanalysis.

Drug monitoring by volumetric absorptive microsampling: method development considerations to mitigate hematocrit effects

Aim: GSKA is a compound that was in development in clinical trials. A bioanalysis method to quantify GSKA using volumetric absorptive microsampling (VAMS) was developed and hematocrit (HCT) related assay bias was investigated. Methodology: After accurate sampling of 10 μl blood, VAMS tips were air dried approximately 18 h and desorbed by an aqueous solution containing internal standard. The recovered blood underwent liquid–liquid extraction in ethyl acetate to minimize matrix suppression. Assay accuracy, precision, linearity, carryover, selectivity, recovery, matrix effects, HCT effects and long-term quality control stability were evaluated. Conclusion: HCT-related assay bias was minimized in 30–60% blood HCT range, and all validation parameters met acceptance criteria. The method is suitable for quantitative analysis of GSKA in human blood.

Application of volumetric absorptive microsampling for robust, high-throughput mass spectrometric quantification of circulating protein biomarkers

Volumetric absorptive micro sampling (VAMS™) allows accurate sampling of 10 µL of blood from a minimally invasive finger prick and could enable remote personalized health monitoring. Moreover, VAMS overcomes effects from hematocrit and sample heterogeneity associated with dried blood spots (DBS). We describe the first application of VAMS with the Mitra® microsampling device for the quantification of protein biomarkers using an automated, high-throughput sample preparation method coupled with mass spectrometric (MS) detection. The analytical performance of the developed workflow was evaluated for 10 peptides from six clinically relevant proteins: apolipoproteins A-I, B, C-I, C-III, E, and human serum albumin (HSA). Extraction recovery from blood with three different levels of hematocrit varied between 100% and 111% for all proteins. Within-day and total assay reproducibility (i.e., 5 replicates on 5 days) ranged between 3.2-10.4% and 3.4-12.6%, respectively. In addition, after 22 weeks of storage of the Mitra microsampling devices at -80 °C, all peptide responses were within ±15% deviation from the initial response. Application to data-independent acquisition (DIA) MS further demonstrated the potential for broad applicability and the general robustness of the automated workflow by reproducible detection of 1661 peptides from 423 proteins (average 15.7%CV (n = 3) in peptide abundance), correlating to peptide abundances in corresponding plasma (R = 0.8383). In conclusion, we have developed an automated workflow for efficient extraction, digestion, and MS analysis of a variety of proteins in a fixed small volume of dried blood (i.e., 10 µL). This robust and high-throughput workflow will create manifold opportunities for the application of remote, personalized disease biomarker monitoring.

Capillary blood collected on volumetric absorptive microsampling (VAMS) device for monitoring hydroxychloroquine in rheumatoid arthritis patients

A novel technique for collection of capillary blood, termed volumetric absorptive microsampling (VAMS), has been recently cleared by the FDA for collection of human blood. VAMS absorbs a fixed volume of blood (10μl) and overcomes area bias and homogeneity issues associated with dried blood spot (DBS). This study is the application of VAMS for therapeutic drug monitoring (TDM) in human capillary blood. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) workflow for analysis of VAMS sample was developed and validated. Concentration of hydroxychloroquine (HCQ) and its metabolites, desethylhydroxychloroquine (DHCQ), desethylchloroquine (DCQ), and bisdesethylchloroquine (BDCQ), in capillary blood on VAMS sampler were compared to those in venous blood in rheumatoid arthritis patients. Feasibility of capillary blood collected on both VAMS and DBS card were evaluated on patients. Stability of dried capillary blood on VAMS was also examined. Our results established that VAMS is a simple and accurate sampling technique that delivers the benefits of DBS sampling while overcoming the issues associated with hematocrit and homogeneity. It requires a small blood volume, simplifies sample logistics management, and may allow sample collection in the patient's home setting.

Evaluation of sample extraction methods for minimizing hematocrit effect on whole blood analysis with volumetric absorptive microsampling

Aim: Volumetric absorptive microsampler (VAMS) was designed to sample a fixed volume of blood regardless of the hematocrit (HCT) levels. Model compounds with a wide range of hydrophobicity were evaluated for their extraction recoveries from VAMS dried blood samples. Results: For the highly hydrophobic compounds, recoveries with methanol or methanol/acetonitrile extraction were higher compared with using the aqueous mixture of methanol or acetonitrile. Extraction with methanol/acetonitrile (1:1) yielded more consistent recovery across the HCT range of 20–70% than using methanol alone, with good linearity, accuracy and precision achieved from 1 to 2000 ng/ml. Conclusion: An organic solvent sample preparation approach was developed to optimize extraction recovery and minimize the HCT effect on the analysis of VAMS dried blood samples.

Is there a role for microsampling in antibiotic pharmacokinetic studies?

INTRODUCTION

Clinical pharmacokinetic studies of antibiotics can establish evidence-based dosing regimens that improve the likelihood of eradicating the pathogen at the site of infection, reduce the potential for selection of resistant pathogens, and minimize harm to the patient. Innovations in small volume sampling (< 50 μL) or 'microsampling' may result in less-invasive sample collection, self-sampling and dried storage. Microsampling may open up opportunities in patient groups where sampling is challenging.

AREAS COVERED

The challenges for implementation of microsampling to assure suitability of the results, include: acceptable study design, regulatory agency acceptance, and meeting bioanalytical validation requirements. This manuscript covers various microsampling methods, including dried blood/plasma spots, volumetric absorptive microsampling, capillary microsampling, plasma preparation technologies and solid-phase microextraction.

EXPERT OPINION

The available analytical technology is being underutilized due to a lack of bridging studies and validated bioanalytical methods. These deficiencies represent major impediments to the application of microsampling to antibiotic pharmacokinetic studies. A conceptual framework for the assessment of the suitability of microsampling in clinical pharmacokinetic studies of antibiotics is provided. This model establishes a 'contingency approach' with consideration of the antibiotic and the type and location of the patient, as well as the more prescriptive bioanalytical validation protocols.