Inclusion of MPA and in a rapid multi-drug LC–tandem mass spectrometric method for simultaneous determination of immunosuppressants

Therapeutic drug monitoring of mycophenolic acid (MPA) using volumetric absorptive microsampling (VAMS) in pediatric renal transplant recipients: ultra-high-performance liquid chromatography-tandem mass spectrometry analytical method development, cross-validation, and clinical application

BACKGROUND

Mycophenolic acid (MPA) is widely used in posttransplant pharmacotherapy for pediatric patients after renal transplantation. Volumetric absorptive microsampling (VAMS) is a recent approach for sample collection, particularly during therapeutic drug monitoring (TDM). The recommended matrix for MPA determination is plasma (PL), and conversion between capillary-blood VAMS samples and PL concentrations is required for the appropriate interpretation of the results.

METHODS

This study aimed to validate and develop a UHPLC-MS/MS method for MPA quantification in whole blood (WB), PL, and VAMS samples, with cross and clinical validation based on regression calculations. Methods were validated in the 0.10-15 µg/mL range for trough MPA concentration measurement according to the European Medicines Agency (EMA) guidelines. Fifty pediatric patients treated with MPA after renal transplantation were included in this study. PL and WB samples were obtained via venipuncture, whereas VAMS samples were collected after the fingerstick. The conversion from VAMS_MPA to PL_MPA concentration was performed using formulas based on hematocrit values and a regression model.

RESULTS

LC-MS/MS methods were successfully developed and validated according to EMA guidelines. The cross-correlation between the methods was evaluated using Passing-Bablok regression, Bland-Altman bias plots, and predictive performance calculations. Clinical validation of the developed method was successfully performed, and the formula based on regression was successfully validated for VAMS_MPA to PL_MPA concentration and confirmed on an independent group of samples.

CONCLUSIONS

This study is the first development of a triple matrix-based LC-MS/MS method for MPA determination in the pediatric population after renal transplantation. For the first time, the developed methods were cross-validated with routinely used HPLC-DAD protocol.

Development of UHPLC-MS/MS method for simultaneous determination of tacrolimus and sirolimus in human whole blood and comparisons with two immunoassays

Tacrolimus (TAC) and sirolimus (SIR) antirejection medications are widely used in organ transplantation. We aimed to develop an ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) assay for quantifying TAC and SIR simultaneously and evaluating agreement with chemiluminescence microparticle immunoassay (CMIA) and electrochemiluminescence immunoassay (ECLIA). Whole blood samples collected from 209 TAC and 208 SIR patients were assessed by UHPLC-MS/MS, CMIA and ECLIA. The agreement of the three techniques was assessed using the Bland-Altman plot. The UHPLC-MS/MS assay had a calibration range of 1-100 ng/ml for TAC and SIR. The accuracy and precision were -2.73-4.32% and <4.71% for TAC, respectively, and 0.07-4.84% and <6.5% for SIR, respectively. The three methods had good correlation. In comparison with UHPLC-MS/MS, two immunoassays showed a slight deviation in proportion. An UHPLC-MS/MS method for simultaneously detecting TAC and SIR in human whole blood was developed, validated and comparatively analyzed with CMIA and ECLIA. For determining TAC and SIR, immunoassays displayed acceptable analytical performances in terms of precision and correlation compared with UHPLC-MS/MS. However, further investigation is warranted to examine the novel method.

Validated Simple HPLC-UV Method for Mycophenolic Acid (MPA) Monitoring in Human Plasma. Internal Standardization: Is It Necessary?

The aim of the work was to prepare a simple but reliable HPLC-UV method for the routine monitoring of mycophenolic acid (MPA). Sample preparation was based on plasma protein precipitation with acetonitrile. The isocratic separation of MPA and internal standard (IS) fenbufen was made on Supelcosil LC-CN column (150 × 4.6 mm, 5 µm) using a mobile phase: CH₃CN:H₂O:0.5M KH₂PO₄:H₃PO₄ (260:700:40:0.4, v/v). UV detection was set at 305 nm. The calibration covered the MPA concentration range: 0.1–40 µg/mL. The precision was satisfactory with RSD of 0.97–7.06% for intra-assay and of 1.92–5.15% for inter-assay. The inaccuracy was found between −5.72% and +2.96% (+15.40% at LLOQ) and between −8.82% and +5.31% (+19.00% at LLOQ) for intra- and inter-assay, respectively, fulfilling acceptance criteria. After a two-year period of successful application, the presented method has been retrospectively calibrated using the raw data disregarding the IS in the calculations. The validation and stability parameters were similar for both calculation methods. MPA concentrations were recalculated and compared in 1187 consecutive routine therapeutic drug monitoring (TDM) trough plasma samples from mycophenolate-treated patients. A high agreement (r² = 0.9931, p < 0.0001) of the results was found. A Bland–Altman test revealed a mean bias of −0.011 μg/mL (95% CI: −0.017; −0.005) comprising −0.14% (95% Cl: −0.39; +0.11), whereas the Passing–Bablok regression was y = 0.986x + 0.014. The presented method can be recommended as an attractive analytical tool for medical (hospital) laboratories equipped with solely basic HPLC apparatus. The procedure can be further simplified by disapplying an internal standard while maintaining appropriate precision and accuracy of measurements.

Overview of therapeutic drug monitoring of immunosuppressive drugs: Analytical and clinical practices

Immunosuppressant drugs (ISDs) play a key role in short-term patient survival together with very low acute allograft rejection rates in transplant recipients. Due to the narrow therapeutic index and large inter-patient pharmacokinetic variability of ISDs, therapeutic drug monitoring (TDM) is needed to dose adjustment for each patient (personalized medicine approach) to avoid treatment failure or side effects of the therapy. To achieve this, TDM needs to be done effectively. However, it would not be possible without the proper clinical practice and analytical tools. The purpose of this review is to provide a guide to establish reliable TDM, followed by a critical overview of the current analytical methods and clinical practices for the TDM of ISDs, and to discuss some of the main practical aspects of the TDM.

Chemical Differentiation of Genetically Identified Atractylodes japonica, A. macrocephala, and A. chinensis Rhizomes Using High-Performance Liquid Chromatography with Chemometric Analysis

The rhizome of Atractylodes japonica, which is a herbal medicine used for gastrointestinal therapeutics, has been categorized with A. macrocephala rhizome or A. chinensis rhizome based on different therapeutic criteria in Korea, China, and Japan. In the present study, 61 A. japonica, A. macrocephala, and A. chinensis rhizomes were collected from Korea and China and were genetically identified by internal transcribed spacer sequencing analysis. Chromatographic profiles were obtained from high-performance liquid chromatography analysis of the methanol and hot-water extracts of Atractylodes rhizomes and chemical differentiation of the rhizomes was carried out using chemometric statistical analyses such as principal component analysis, hierarchical clustering analysis, and Pearson's correlation coefficient analysis. The results from chromatographic profiles and chemometric analyses demonstrate that A. japonica rhizomes showed apparent chemical differences from A. macrocephala and A. chinensis rhizomes in the methanol extracts. In contrast, no clear distinction was apparent for the hot-water extracts of Atractylodes rhizomes, especially A. chinensis rhizomes. These results indicate that there is a clear chemical difference between A. japonica and A. macrocephala rhizomes; however, the chemical diversity of A. chinensis rhizome shows different chemical relationships with A. japonica or A. macrocephala rhizome, dependent on the chemical features.

Current methods of the analysis of immunosuppressive agents in clinical materials: A review

More than 100000 solid organ transplantations are performed every year worldwide. Calcineurin (cyclosporine A, tacrolimus), serine/threonine kinase (sirolimus, everolimus) and inosine monophosphate dehydrogenase inhibitor (mycophenolate mofetil), are the most common drugs used as immunosuppressive agents after solid organ transplantation. Immunosuppressive therapy, although necessary after transplantation, is associated with many adverse consequences, including the formation of secondary metabolites of drugs and the induction of their side effects. Calcineurin inhibitors are associated with nephrotoxicity, cardiotoxicity and neurotoxicity; moreover, they increase the risk of many diseases after transplantation. The review presents a study of the movement of drugs in the body, including the processes of absorption, distribution, localisation in tissues, biotransformation and excretion, and also their accompanying side effects. Therefore, there is a necessity to monitor immunosuppressants, especially because these drugs are characterised by narrow therapeutic ranges. Their incorrect concentrations in a patient's blood could result in transplant rejection or in the accumulation of toxic effects. Immunosuppressive pharmaceuticals are macrolide lactones, peptides, and high molecular weight molecules that can be metabolised to several metabolites. Therefore the two main analytical methods used for their determination are high performance liquid chromatography with various detection methods and immunoassay methods. Despite the rapid development of new analytical methods of analysing immunosuppressive agents, the application of the latest generation of detectors and increasing sensitivity of such methods, there is still a great demand for the development of highly selective, sensitive, specific, rapid and relatively simple methods of immunosuppressive drugs analysis.

Quality Assessment of Ojeok-San, a Traditional Herbal Formula, Using High-Performance Liquid Chromatography Combined with Chemometric Analysis

Ojeok-san (OJS) is a traditional herbal formula consisting of 17 herbal medicines that has been used to treat various disorders. In this study, quantitative analytical methods were developed using high-performance liquid chromatography equipped with a photodiode array detector to determine 19 marker compounds in OJS preparations, which was then combined with chemometric analysis. The method developed was validated in terms of its precision and accuracy. The intra- and interday precision of the marker compounds were <3.0% of the relative standard deviation (RSD) and the recovery of the marker compounds was 92.74%-104.16% with RSD values <3.0%. The results of our quantitative analysis show that the quantities of the 19 marker compounds varied between a laboratory water extract and commercial OJS granules. The chemometric analysis used, principal component analysis (PCA) and hierarchical clustering analysis (HCA), also showed that the OJS water extract produced using a laboratory method clearly differed from the commercial OJS granules; therefore, an equalized production process is required for quality control of OJS preparations. Our results suggest that the HPLC analytical methods developed are suitable for the quantification and quality assessment of OJS preparations when combined with chemometric analysis involving PCA and HCA.

Liquid chromatography tandem mass spectrometry in the clinical laboratory

Clinical laboratory medicine has seen the introduction and evolution of liquid chromatography tandem mass spectrometry in routine clinical laboratories over the last 10–15 years. There still exists a wide diversity of assays from very esoteric and highly specialist manual assays to more simplified kit-based assays. The technology is not static as manufacturers are continually making improvements. Mass spectrometry is now commonly used in several areas of diagnostics including therapeutic drug monitoring, toxicology, endocrinology, paediatrics and microbiology. Some of the most high throughput analyses or common analytes include vitamin D, immunosuppressant monitoring, androgen measurement and newborn screening. It also offers flexibility for the measurement of analytes in a variety of different matrices which would prove difficult with immunoassays. Unlike immunoassays or high-pressure liquid chromatography assays using ultraviolet or fluorescence detection, mass spectrometry offers better specificity and reduced interferences if attention is paid to potential isobaric compounds. Furthermore, multiplexing, which enables multiple analytes to be measured with the same volume of serum is advantageous, and the requirement for large sample volumes is decreasing as instrument sensitivity increases. There are many emerging applications in the literature. Using mass spectrometry to identify novel isoforms or modified peptides is possible as is quantification of proteins and peptides, with or without protein digests. Future developments by the manufacturers may also include mechanisms to improve the throughput of samples and strategies to decrease the level of skill required by the operators.

Simultaneous determination of cyclosporine A, tacrolimus, sirolimus, and everolimus in whole-blood samples by LC-MS/MS

Objectives. Cyclosporine A (CyA), tacrolimus (TRL), sirolimus (SIR), and everolimus (RAD) are immunosuppressive drugs frequently used in organ transplantation. Our aim was to confirm a robust sensitive and selective liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for determination of CyA, TRL, SIR, and RAD in whole-blood samples. Materials and Methods. We used an integrated online solid-phase extraction-LC-MS/MS system and atmospheric pressure ionization tandem mass spectrometry (API-MS/MS) in the multiple reaction monitoring (MRM) detection mode. CyA, TRL, SIR, and RAD were simultaneously analyzed in whole blood treated with precipitation reagent taken from transplant patients. Results. System performance parameters were suitable for using this method as a high-throughput technique in clinical practice. The high concentration of one analyte in the sample did not affect the concentration of other analytes. Total analytical time was 2.5 min, and retention times of all analytes were shorter than 2 minutes. Conclusion. This LC-MS/MS method can be preferable for therapeutic drug monitoring of these immunosuppressive drugs (CyA, TRL, SRL, and RAD) in whole blood. Sample preparation was too short and simple in this method, and it permits robust, rapid, sensitive, selective, and simultaneous determination of these drugs.

Validation of an LC-MS/MS method to determine five immunosuppressants with deuterated internal standards including MPA

Background

Therapeutic drug monitoring of immunosuppressive drugs in organ-transplanted patients is crucial to prevent intoxication or transplant rejection due to inadequate dosage. The commonly used immunoassays have been gradually undergoing replacement by mass spectrometry, since this physical method offers both a higher sensitivity and specificity. However, a switch should be carefully considered because it is a challenging procedure and needs to be thoroughly validated.

From an economic perspective it is reasonable to include mycophenolic acid into the assay, because this saves the necessity for an additional measurement. However, to date very few validation protocols for the measurement of immunosuppressants, including mycophenolic acid, are available. In order to adequately compensate for matrix effects, the use of stable isotope labeled internal standards is advisable. Here, the authors describe a single method suitable for the quantification of cyclosporine A, tacrolimus, sirolimus, everolimus and mycophenolic acid, based on deuterated internal standards.

Methods

Plasma proteins were precipitated with zinc-sulfate, followed by an online solid phase extraction in the flow-through direction. Chromatographic separation was performed by a c18-phenyl-hexyl column. For subsequent mass spectrometric analysis stable-isotope-labeled internal standards were used. Results were available after 3.5 minutes.

Results

Low quantification limits (accuracy: 104 - 118%) and linearity resulted in 2 -1250 ng/ml for cyclosporine A; 0.5 - 42.2 ng/ml for tacrolimus; 0.6 - 49.2 ng/ml for sirolimus; 0.5 - 40.8 ng/ml for everolimus and 0.01 - 7.5 μg/ml for mycophenolic acid. Intra-assay precision revealed a coefficient of variation (CV) of 0.9 - 14.7%, with an accuracy of 89 - 138%. The CV of inter-assay precision was 2.5 - 12.5%, with an accuracy of 90 - 113%. Recovery ranged from 76.6 to 84%. Matrix effects were well compensated by deuterated internal standards.

Conclusions

The authors present a fast, economical and robust method for routine therapeutic drug monitoring comprising five immunosuppressants including mycophenolic acid.

LC-MS/MS for immunosuppressant therapeutic drug monitoring

Due to their narrow therapeutic indices and highly variable pharmacokinetics, therapeutic drug monitoring is necessary to individualize immunosuppressant dosage following organ transplantation. Until recently, monitoring was performed primarily using immunoassays, however, there is an increasing shift to HPLC coupled with MS/MS, due to its greater sensitivity and specificity. Online sample clean-up with either a single analytical column or with 2D chromatography significantly reduces manual handling and is essential to minimize matrix effects and maximize specificity and, coupled with rapid chromatography, allows the simultaneous analysis of the major immunosuppressants, with rapid sample throughput. Thus, LC-MS/MS is an attractive and versatile technique that facilitates rapid development of analytical methods, including new immunosuppressants as they become approved for clinical use.

A review of clinical diagnostic applications of liquid chromatography-tandem mass spectrometry

Liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS) technology is emerging as a complementary method to traditional methodology used for clinical applications. Enhanced specificity and high-throughput capabilities are providing significant benefits to clinical diagnostic laboratories conducting routine analyses. This technology is expected to expand rapidly as scientists focus on more complicated challenges that can be solved efficiently by adding LC/MS/MS to their arsenal of techniques.

Determination of mycophenolic acid and its phenyl glucuronide in human plasma, ultrafiltrate, blood, DBS and dried plasma spots

Background: Analysis of mycophenolic acid (MPA), the active form of the immunosuppressive drug mycophenolate mofetil, and its glucuronide metabolite MPAG is required for therapeutic monitoring and postmarketing clinical studies. Dried blood spots (DBS) and dried plasma spots (DPS) could be alternatives to conventional assays for small-volume sampling and easy shipment. Results: A LC–MS/MS method with online SPE was established using stable isotope labeled analytes as internal standards. The quantitation limits were set at 0.1 and 1 µg/ml, for total MPA and MPAG, respectively, in plasma, blood, DBS and DPS, but 100-fold lower for free MPA in ultrafiltrate. Ahlstrom 226 or Whatman FTA® DMPK-B cards were well suited for DBS and DPS analyses. Conclusion: MPA and MPAG were analyzed in human plasma and blood either as liquid or dried on cards with similar assay quality. Care should be taken to avoid back-conversion of an instable acyl glucuronide metabolite to MPA.

Steroid measurement with LC-MS/MS. Application examples in pediatrics

The correct measurement of steroids is vital for the diagnosis of congenital adrenal hyperplasia (CAH), apparent mineralocorticoid excess, familial hyperaldosteronism type I, primary aldosteronism, Cushing's disease, adrenal insufficiency, etc. Steroid diagnostics also plays an important role in disorders of sexual differentiation and gonadal function. Steroid metabolism is involved in evaluations for precocious puberty, premature thelarche, and polycystic-ovary disease. Finally, the hypothalamo-pituitary-adrenal (HPA) axis is considered to be one of the major systems involved in fetal programming or in stress regulation. Most methods for the determination of steroid hormones are based on immunoassays, which are rapid and easy to perform. However, the reliability of several steroid immunoassays has been shown to be questionable because of the lack of specificity and of matrix effects. Immunological methods, especially direct assays, often overestimate true steroid values. Patient follow-up over time or between laboratories, as well as longitudinal studies, are therefore extremely difficult. This is of particular importance in pediatrics. Liquid chromatography triple quadrupole mass spectrometry (LC-MS/MS) is an increasingly common tool in the clinical laboratory and has the potential to overcome the limitations of immunoassays. LC-MS/MS affords the specificity, imprecision, and limits of quantification necessary for the reliable measurement of steroids, expanding diagnostic capabilities. In addition to the high throughput, the method requires minimal sample preparation and a small sample volume. All these features make it an attractive method to use in a clinical setting. Moreover, LC-MS/MS has the advantage that a spectrum of steroid hormones can be measured simultaneously. Steroid profiling is a very effective method for distinguishing almost all steroid-related disorders. It allows accurate diagnosis and is very useful in many clinical situations. Steroid profiles open up new vistas. The applicability for clinical samples and questions in pediatric endocrinology will be discussed.

The current role of liquid chromatography-tandem mass spectrometry in therapeutic drug monitoring of immunosuppressant and antiretroviral drugs

Therapeutic drug monitoring of critical dose immunosuppressant drugs is established clinical practice and there are similar good reasons to monitor antiretrovirals. The aim of this article is to review the recent literature (last five years), with particular reference to the use of liquid chromatography-tandem mass spectrometry (LC-MS/MS). LC-MS/MS offers many potential advantages. The superior selectivity of LC-MS/MS over immunoassays for immunosuppressant drugs has been widely reported. Simultaneous measurement of a number of drugs can be performed. It is currently routine practice for the four major immunosuppressants (cyclosporin, tacrolimus, sirolimus and everolimus) to be simultaneously measured in whole blood. While up to 17 antiretroviral drugs have been simultaneously measured in plasma. The exquisite sensitivity of LC-MS/MS also provides the opportunity to measure these drugs in alternative matrices, such as dried blood spots, saliva, peripheral blood mononuclear cells and tissue. However, the clinical utility of measuring these classes of drugs in alternative matrices is still to be determined.

Potential of dried blood self-sampling for cyclosporine c(2) monitoring in transplant outpatients

Background. Close therapeutic drug monitoring of Cyclosporine (CsA) in transplant outpatients is a favourable procedure to maintain the long-term blood drug levels within their respective narrow therapeutic ranges. Compared to basal levels (C₀), CsA peak levels (C₂) are more predictive for transplant rejection. However, the application of C₂ levels is hampered by the precise time of blood sampling and the need of qualified personnel. Therefore, we evaluated a new C₂ self-obtained blood sampling in transplant outpatients using dried capillary and venous blood samples and compared the CsA levels, stability, and clinical practicability of the different procedures. Methods. 55 solid organ transplant recipients were instructed to use single-handed sampling of each 50 μL capillary blood and dried blood spots by finger prick using standard finger prick devices. We used standardized EDTA-coated capillary blood collection systems and standardized filter paper WS 903. CsA was determined by LC-MS/MS. The patients and technicians also answered a questionnaire on the procedure and sample quality. Results. The C₀ and C₂ levels from capillary blood collection systems (C₀ [ng/mL]: 114.5 ± 44.5; C₂: 578.2 ± 222.2) and capillary dried blood (C₀ [ng/mL]: 175.4 ± 137.7; C₂: 743.1 ± 368.1) significantly (P < .01) correlated with the drug levels of the venous blood samples (C₀ [ng/mL]: 97.8 ± 37.4; C₂: 511.2 ± 201.5). The correlation at C₀ was ρ_cap.-ven. = 0.749, and ρ_{dried blood-ven} = 0.432; at C₂: ρ_cap.-ven. = 0.861 and ρ_{dried blood-ven} = 0.711. The patients preferred the dried blood sampling because of the more simple and less painful procedure. Additionally, the sample quality of self-obtained dried blood spots for LC-MS/MS analytics was superior to the respective capillary blood samples. Conclusions. C₂ self-obtained dried blood sampling can easily be performed by transplant outpatients and is therefore suitable and cost-effective for close therapeutic drug monitoring.

Steroid measurement with LC-MS/MS in pediatric endocrinology

The liquid chromatography-tandem mass spectrometry (LC-MS/MS) is an increasingly common tool in the clinical laboratory. Established applications include routine assays for detecting inborn errors of metabolism and for monitoring therapeutic drugs and steroids. Steroid profiling is a very effective method for distinguishing almost all steroid related disorders. It allows accurate diagnosis and is very useful in many clinical situations. Most methods for the determination of steroid hormones are based on immunoassays, which are rapid and easy to perform. However, the reliability of steroid immunoassays has been shown to be doubtful because of the lack of specificity and of matrix effects. Immunological methods, especially direct assays, often overestimate true steroid values. This is of particular importance in the newborn period and in early infancy. Problems with steroid immunoassays have further been reported for female patients or when analysing different media, e.g. saliva. Patient follow-up over time or between laboratories, as well as longitudinal studies are extremely difficult. In contrast to immunoassays, which allow the measurement of only a single steroid at a time, LC-MS/MS has the advantage that a wide spectrum of steroid hormones can be measured simultaneously. The applicability for clinical samples and problems in pediatric endocrinology will be discussed.

Setting up a 2D-LC/MS/MS method for the rapid quantitation of the prostanoid metabolites 6-oxo-PGF(1alpha) and TXB2 as markers for hemostasis assessment

6-oxo-PGF(1alpha) and TXB(2) are the metabolites of the prostanglandin PGI(2) and of the thromboxane TXA(2), respectively. PGI(2) and TXA(2) are arachidonic acid-derived compounds which regulate the blood hemostasis. Their quick metabolism leads to the 6-oxo-PGF(1alpha) and TXB(2) metabolites in plasma. In order to study on a large base the external factors influencing the hemostatic conditions, there is a need for a fast and reliable assay for quantitating these metabolites. Some methods have been published for the analysis of the arachidonic acid-derived compounds and some are dealing with mass spectrometry but nonspecifically centered on these specific compounds with a fast and cheap protocol, amenable for large-scale studies. Here we describe an analytical strategy that incorporates a two-dimensional chromatography running coupled to tandem mass spectrometry that minimizes the sample preparation and addresses the presence of the TXB(2) anomers for a robust quantitation measurement. After a protein precipitation, 100 microl of the supernatant (corresponding to 50 microl of the original plasma) was injected in a two-dimensional chromatographic system which operates an on-line clean-up and a subsequent chromatographic separation of the targeted analytes with a limit of quantitation (LOQ) of 22 pg/ml for 6-oxo-PGF(1alpha), and and a LOQ of 25 pg/ml for TXB(2).

Prevention of atherosclerosis by the mTOR inhibitor everolimus in LDLR-/- mice despite severe hypercholesterolemia

Everolimus inhibits the mammalian target of rapamycin (mTOR) in proliferating cells. It is widely used in transplant patients and has also been exploited by drug-eluting stents for the treatment of cardiovascular disease. However, there is only limited data on the pathophysiological effects of mTOR-inhibitors on the vascular wall. We aimed to unravel the effects of everolimus on cholesterol-induced atherosclerosis and on circulating cell mediators in LDL-receptor-deficient (LDLR(-/-)) mice. Male hypercholesterolemic LDLR(-/-) mice received either solvent (group A; n=28) or everolimus at 0.05 mg/kg (group B, n=22) and 1.5 mg/kg (group C, n=29) per body weight per day by subcutaneously implanted osmotic minipumps for the study period of 12 weeks. Group B showed 44% reduction of atherosclerotic lesions at the brachiocephalic artery (BCA). In group C atherosclerotic lesions were reduced by 85% in the BCA and by 60% at the aortic root. This was associated with a significantly lower complexity of lesions in both treated groups (p<0.001) and despite a 40% increase of plasma cholesterol. Everolimus caused a significant reduction of circulating cell mediators such as interleukin-1alpha, interleukin-5, GM-CSF and interleukin-12p40. Everolimus increased the plasma levels of KC but had no effect on eighteen other circulating cell mediators studied. Everolimus strongly inhibits atherosclerosis development in LDL-receptor(-/-) mice despite severe hypercholesterolemia. Everolimus application had only small effects on circulating cell mediators. The significant reduction of atherosclerotic lesions was associated with a delayed transition from early macrophages enriched lesions to advanced atherosclerotic plaques.

Methanol-Associated Matrix Effects in Electrospray Ionization Tandem Mass Spectrometry

Background: Matrix effects can profoundly reduce the performance of electrospray ionization mass spectrometry. Preliminary observations indicated that the methanol used in the mobile phase could be a source of differential ionization or ion suppression.

Methods: Drug stability studies, analysis of biological extracts, mixing experiments, and postcolumn infusions were used to test 9 commercial methanols for ionization differences in liquid chromatography-tandem mass spectrometry assays for immunosuppressants. Area responses for the drugs and internal standards were compared for mobile phases prepared with each selected methanol. Postcolumn infusion experiments were performed to confirm the degree of ionization differences occurring at the ion source, and to evaluate the proportions of ammonium, sodium, and potassium adducts.

Results: The decrease in signal for the immunosuppressant drugs was shown to result from differential ionization associated with the selected methanols. Product ion intensity varied by 10-fold among the methanols tested. For sirolimus, tacrolimus, and mycophenolic acid, the percentage change in ionization was the same for the drug and its corresponding internal standard. Postcolumn sirolimus infusion evaluation revealed that a 1000-fold analyte concentration difference did not affect ionization. The proportions of ammonium, sodium, and potassium adducts of sirolimus precursor ions differed in relation to the source of methanol.

Conclusions: Organic solvents used in mobile phases and extract preparation of biological samples may be associated with ion suppression, affecting adduct formation and assay sensitivity.

A liquid chromatography/tandem mass spectrometric multi-mycotoxin method for the quantification of 87 analytes and its application to semi-quantitative screening of moldy food samples

This paper describes the extension of a previously published method based on liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC/ESI-MS/MS) from 39 to currently 87 analytes. Besides the mycotoxins for which regulated concentrations exist, the method now comprises not only almost all mycotoxins for which standards are commercially available, but also a number of other important metabolites produced by fungi involved in food spoilage. The method is based on a single extraction step using an acidified acetonitrile/water mixture followed by analysis of the diluted crude extract. Method performance characteristics were determined after spiking breadcrumbs as model matrix at multiple concentration levels. With very few exceptions, coefficients of variation of the whole procedure of <5% and repeatabilities at the highest spiking level of <7% were obtained. Limits of detection ranged between 0.02 and 225 microg kg(-1). The quantitative determination of ergopeptides was disturbed by epimerization due to the acidic conditions. From the remaining 77 analytes, the apparent recoveries of nine substances deviated significantly from the CEN target range of 70-110% due to incomplete extraction and/or matrix effects. In principle, the latter can be compensated for by the application of matrix-matched calibration. The developed method was applied to 18 moldy samples (including bread, fruits, vegetables, jam, cheese, chestnuts and red wine) from private households. This study revealed the great value of the described method: 37 different fungal metabolites were identified at concentrations of up to 33 mg kg(-1), and some of these have never been reported before in the context of moldy food products.

Recent advances in high-throughput quantitative bioanalysis by LC–MS/MS

Liquid chromatography linked to tandem mass spectrometry (LC-MS/MS) has played an important role in pharmacokinetics and metabolism studies at various drug development stages since its introduction to the pharmaceutical industry. This article reviews the most recent advances in sample preparation, separation, and the mass spectrometric aspects of high-throughput quantitative bioanalysis of drug and metabolites in biological matrices. Newly introduced techniques such as ultra-performance liquid chromatography with small particles (sub-2 microm) and monolithic chromatography offer improvements in speed, resolution and sensitivity compared to conventional chromatographic techniques. Hydrophilic interaction chromatography (HILIC) on silica columns with low aqueous/high organic mobile phase is emerging as a valuable supplement to the reversed-phase LC-MS/MS. Sample preparation formatted to 96-well plates has allowed for semi-automation of off-line sample preparation techniques, significantly impacting throughput. On-line solid-phase extraction (SPE) utilizing column-switching techniques is rapidly gaining acceptance in bioanalytical applications to reduce both time and labor required to produce bioanalytical results. Extraction sorbents for on-line SPE extend to an array of media including large particles for turbulent flow chromatography, restricted access materials (RAM), monolithic materials, and disposable cartridges utilizing traditional packings such as those used in Spark Holland systems. In the end, this paper also discusses recent studies of matrix effect in LC-MS/MS analysis and how to reduce/eliminate matrix effect in method development and validation.

Current role of LC-MS in therapeutic drug monitoring

The role of liquid chromatography coupled with mass spectrometry (LC-MS) techniques in routine therapeutic drug monitoring activity is becoming increasingly important. This paper reviews LC-MS methods published in the last few years for certain classes of drugs subject to therapeutic drug monitoring: immunosuppressants, antifungal drugs, antiretroviral drugs, antidepressants and antipsychotics. For each class of compounds, we focussed on the most interesting methods and evaluated the current role of LC-MS in therapeutic drug monitoring.

Recent developments in extraction procedures relevant to analytical toxicology

Sample preparation is an important step in the development of an analytical method but is often regarded as time-consuming, laborious work. Optimum sample preparation leads to enhanced selectivity and sensitivity, however, and reduces amounts of interfering matrix compounds, resulting in less signal suppression or enhancement. Recent developments in extraction techniques that could be of interest in clinical and forensic toxicology, for example liquid-liquid, solid-phase, and headspace extraction, are summarized in this review. The advantages and disadvantages of several extraction techniques are discussed, to enable the reader to choose an appropriate method of extraction for his or her application. Attention is paid to current trends in analytical toxicology, for example miniaturization, high throughput, and automation.