Robust, High-Throughput LC-MS/MS Method for Therapeutic Drug Monitoring of Cyclosporine, Tacrolimus, Everolimus, and Sirolimus in Whole Blood

Preparation of a new composite based on multilayer fullerene with mesoporous carbon nitride and its application in the extraction of tacrolimus and everolimus from plasma prior to LC-MS/MS analysis

The development of new and efficient adsorbents for dispersive solid-phase extraction method, particularly prior to chromatography analysis, is increasing. In particular, this method is recommended for use before biological sample analysis. In this work, a new composite was prepared from mesoporous carbon nitrides and carbon nano-onions and was utilized for the extraction of tacrolimus and everolimus from plasma samples prior to high-performance liquid chromatography-tandem mass spectrometry analysis. To achieve this aim, first, mesoporous carbon nitrides and carbon nano-onions were synthesized separately and mixed at optimized proportions. Subsequently, a suitable amount of the prepared composite (5 mg) was added to 2 mL of sample solution containing the analytes under vortexing. Next, the extracted analytes were eluted using acetonitrile. The approach was linear within the ranges of 1.0-500 and 0.51-500 ng mL-1 for tacrolimus and everolimus, respectively. Sensitive limits of detection (0.31 and 0.15 ng mL-1 for tacrolimus and everolimus, respectively), acceptable relative standard deviations (intra- and inter-day precisions of ≤5.6% and high extraction recoveries of 71.0% and 83.0% for tacrolimus and everolimus, respectively) were obtained. The results showed that the method can be successfully applied in the simultaneous extraction of the studied analytes from plasma.

LC-MS/MS and EMIT measure the whole blood concentration of cyclosporine A: The two methods yield concordant results within the dynamic range of the latter, but the former shows broader application scenarios

Cyclosporine A (CsA) is a widely used immunosuppressive drug with a narrow therapeutic index and large individual differences. Its therapeutic and toxic effects are closely related to blood drug concentrations, requiring routine therapeutic drug monitoring (TDM). The current main methods for TDM of CsA are enzyme multiplied immunoassay technique (EMIT) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). However, few study on the method comparison of the EMIT and LC-MS/MS for the measurement of whole blood CsA concentration in children has been reported. In this study, we developed a simple and sensitive LC-MS/MS assay for the determination of CsA, and 657 cases of CsA concentrations were determined from 197 pediatric patients by a routine EMIT assay and by the validated in-house LC-MS/MS method on the same batch of samples, aimed to address the aforementioned concern. Consistency between the two assays was evaluated using linear regression and Bland-Altman analysis. The linear range of LC-MS/MS was 0.500-2000 ng/mL and that of the EMIT was 40-500 ng/mL, respectively. Overall, the correlation between the two methods was significant (r-value ranging from 0.8842 to 0.9441). Unsatisfactory consistency was observed in the concentrations < 40 ng/mL (r = 0.7325) and 200-500 ng/mL (r = 0.6851). Bland-Altman plot showed a mean bias of -18.0 % (±1.96 SD, -73.8 to 37.8 %) between EMIT and LC-MS/MS. For Passing-Bablok regression between EMIT and LC-MS/MS did not differ significantly (p > 0.05). In conclusion, the two methods were closely correlated, but the CsA concentration by LC-MS/MS assay was slightly higher than that by EMIT method. Switching from the EMIT assay to the LC-MS/MS method was acceptable, and the LC-MS/MS method will receive broader application in clinical settings due to its better analytical capabilities, but the results need to be further verified in different laboratories.

Tacrolimus Variability and Clinical Outcomes in the Early Post-lung Transplantation Period: Oral Versus Continuous Intravenous Administration

BACKGROUND AND OBJECTIVE

High variability in tacrolimus pharmacokinetics directly after lung transplantation (LuTx) may increase the risk for acute kidney injury (AKI) and transplant rejection. The primary objective was to compare pharmacokinetic variability in patients receiving tacrolimus orally versus intravenously early after LuTx.

METHODS

Pharmacokinetic and clinical data from 522 LuTx patients transplanted between 2010 and 2020 in two university hospitals were collected to compare orally administered tacrolimus to intravenous tacrolimus early post-transplantation. Tacrolimus blood concentration variability, measured as intrapatient variability (IPV%) and  percentage of time within the therapeutic range (TTR%), was analyzed within the first 14 days after LuTx. Secondary outcomes were AKI, acute rejection, length of stay in the intensive care unit (ICU), and mortality in the ICU and during hospital admission.

RESULTS

We included 224 patients in the oral and 298 in the intravenous group. The mean adjusted IPV% was 10.8% (95% confidence interval [CI] 6.9-14.6; p < 0.001) higher in the oral group (27.2%) than the intravenous group (16.4%). The mean TTR% was 7.3% (95% CI - 11.3 to - 3.4; p < 0.001) lower in the oral group (39.6%) than in the intravenous group (46.9%). The incidence of AKI was 46.0% for oral and 42.6% for intravenous administration (adjusted odds ratio [OR] 1.2; 95% CI 0.8-1.8; p = 0.451). The frequencies of clinically diagnosed acute rejection in the oral and intravenous groups were nonsignificant (24.6% vs 17.8%; OR 1.5 [95% CI 1.0-2.3; p = 0.059]). ICU and hospital mortality rate and ICU length of stay were similar.

CONCLUSIONS

Administering tacrolimus orally directly after LuTx leads to a higher variability in blood concentrations compared to intravenous administration. There was no difference in the occurrence of AKI or transplant rejection.

Everolimus decreases [U-13C]glucose utilization by pyruvate carboxylase in breast cancer cells in vitro and in vivo

Reprogrammed metabolism is a hallmark of cancer, but notoriously difficult to target due to metabolic plasticity, especially in response to single metabolic interventions. Combining mTOR inhibitor everolimus and mitochondrial complex 1 inhibitor metformin results in metabolic synergy in in vitro models of triple-negative breast cancer. Here, we investigated whether the effect of this drug combination on tumor size is reflected in changes in tumor metabolism using [U-13C]glucose labeling in an MDA-MB-231 triple negative breast cancer xenograft model. The in vitro effects of everolimus and metformin treatment on oxidative phosphorylation and glycolysis reflected changes in 13C-labeling of metabolites in MDA-MB-231 cells. Treatment of MDA-MB-231 xenografts in SCID/Beige mice with everolimus resulted in slower tumor growth and reduced tumor size and tumor viability by 35%. Metformin treatment moderately inhibited tumor growth but did not enhance everolimus-induced effects. High serum levels of everolimus were reached, whereas levels of metformin were relatively low. Everolimus decreased TCA cycle metabolite labeling and inhibited pyruvate carboxylase activity. Metformin only caused a mild reduction in glycolytic metabolite labeling and did not affect pyruvate carboxylase activity or TCA cycle metabolite labeling. In conclusion, treatment with everolimus, but not metformin, decreased tumor size and viability. Furthermore, the efficacy of everolimus was reflected in reduced 13C-labeling of TCA cycle intermediates and reduced pyruvate carboxylase activity. By using in-depth analysis of drug-induced changes in glucose metabolism in combination with measurement of drug levels in tumor and plasma, effects of metabolically targeted drugs can be explained, and novel targets can be identified.

Pharmacokinetics of Tacrolimus in Pregnant Solid-Organ Transplant Recipients: A Retrospective Study

Data on the pharmacokinetics of tacrolimus during pregnancy are limited. Therefore, the aim of this retrospective study was to characterize the whole-blood pharmacokinetics of tacrolimus throughout pregnancy. In this single-center retrospective cohort study, whole-blood tacrolimus trough concentrations corrected for the dose (concentration-to-dose [C/D] ratios) were compared before, monthly during, and after pregnancy in kidney, liver, and lung transplant recipients who became pregnant and gave birth between 2000 and 2022. Descriptive statistics and linear mixed models were used to characterize changes in tacrolimus C/D ratios before, during, and after pregnancy. The total study population included 46 pregnancies (31 pregnant women). Nineteen, 21, and 6 pregnancies were following kidney, liver, and lung transplantation, respectively. Immediate-release or extended-release formulations were used in 54.5% and 45.5% of the women, respectively. Tacrolimus C/D ratios significantly (P < .001) decreased (-48%) compared to the prepregnancy state at 7 months of pregnancy. These ratios recovered within 3 months postpartum (P = .002). C/D ratios tended to be lower during treatment with an extended-release formulation than with an immediate-release formulation (P = .071). Transplantation type did not significantly affect C/D ratios during pregnancy (P = .873). In conclusion, we found that tacrolimus whole-blood pharmacokinetics change throughout pregnancy, with the lowest C/D ratios (48% decrease) in the 7th month of pregnancy. In general, the decrease in C/D ratios seems to stabilize from month 4 onward compared to prepregnancy.

Multiplex Immunosuppressant (ISD) Method for the Measurement of Cyclosporine A, Tacrolimus, Sirolimus/Rapamycin, and Everolimus in Whole Blood Using MassTrak™ Kit

Cyclosporine A, everolimus, sirolimus, and tacrolimus are the most commonly used immunosuppressant drugs in organ transplant and auto-immune patients. The narrow therapeutic window of these immunosuppressant drugs requires close monitoring of drug blood levels to ensure proper therapeutic response. A quick, robust high-throughput liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was introduced for monitoring whole blood levels of these immunosuppressant drugs with the use of the MassTrak™ Immunosuppressant kit. The assay was carried out in 96-well plate format and requires a simple precipitation step; after which, the supernatant is subjected to liquid chromatography separation (2 min total run time) using a C18 Cartridge column. Identification and quantitation of cyclosporine A, everolimus, sirolimus, and tacrolimus was achieved by employing multiple reaction monitoring (MRM) in positive mode electrospray ionization (ESI). The method exhibits a linear measuring range from 10 to 1500 ng/mL (Cyclosporine A), 1.0-30.0 ng/mL (Everolimus), 1.0-26.0 ng/mL (Sirolimus), and 1.0-30.0 ng/mL (Tacrolimus) and has a within-run and between-run imprecision of <10%.

A Joint Pharmacokinetic Model for the Simultaneous Description of Plasma and Whole Blood Tacrolimus Concentrations in Kidney and Lung Transplant Recipients

BACKGROUND AND OBJECTIVE

Historically, dosing of tacrolimus is guided by therapeutic drug monitoring (TDM) of the whole blood concentration, which is strongly influenced by haematocrit. The therapeutic and adverse effects are however expected to be driven by the unbound exposure, which could be better represented by measuring plasma concentrations.

OBJECTIVE

We aimed to establish plasma concentration ranges reflecting whole blood concentrations within currently used target ranges.

METHODS

Plasma and whole blood tacrolimus concentrations were determined in samples of transplant recipients included in the TransplantLines Biobank and Cohort Study. Targeted whole blood trough concentrations are 4-6 ng/mL and 7-10 ng/mL for kidney and lung transplant recipients, respectively. A population pharmacokinetic model was developed using non-linear mixed-effects modelling. Simulations were performed to infer plasma concentration ranges corresponding to whole blood target ranges.

RESULTS

Plasma (n = 1973) and whole blood (n = 1961) tacrolimus concentrations were determined in 1060 transplant recipients. A one-compartment model with fixed first-order absorption and estimated first-order elimination characterised observed plasma concentrations. Plasma was linked to whole blood using a saturable binding equation (maximum binding 35.7 ng/mL, 95% confidence interval (CI) 31.0-40.4 ng/mL; dissociation constant 0.24 ng/mL, 95% CI 0.19-0.29 ng/mL). Model simulations indicate that patients within the whole blood target range are expected to have plasma concentrations (95% prediction interval) of 0.06-0.26 ng/mL and 0.10-0.93 ng/mL for kidney and lung transplant recipients, respectively.

CONCLUSION

Whole blood tacrolimus target ranges, currently used to guide TDM, were translated to plasma concentration ranges of 0.06-0.26 ng/mL and 0.10-0.93 ng/mL for kidney and lung transplant recipients, respectively.

A simple and accurate LC‑MS/MS method for monitoring cyclosporin A that is suitable for high throughput analysis

With time, the number of samples in clinical laboratories from therapeutic drug monitoring has increased. Existing analytical methods for blood cyclosporin A (CSA) monitoring, such as high-performance liquid chromatography (HPLC) and immunoassays, have limitations including cross-reactivity, time consumption, and the complicated procedures involved. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) has long been considered the reference standard owing to its high accuracy, specificity, and sensitivity. However, large numbers of blood samples, multi-step preparation procedures, and longer analytical times (2.5-20 min) are required as a consequence of the different technical strategies, to ensure good analytical performance and routine quality assurance. A stable, reliable, and high throughput detection method will save personnel time and reduce laboratory costs. Therefore, a high throughput and simple LC-MS/MS method was developed and validated for the detection of whole-blood CSA with CSA-d12 as the internal standard in the present study. Whole blood samples were prepared through a modified one-step protein precipitation method. A C18 column (50x2.1 mm, 2.7 µm) with a mobile phase flow rate of 0.5 ml/min was used for chromatographic separation with a total running time of 4.3 min to avoid the matrix effect. To protect the mass spectrometer, only part of the sample after LC separation was allowed to enter the mass spectrum, using two HPLC systems coupled to one mass spectrometry. In this way, throughput was improved with detection of two samples possible within 4.3 min using a shorter analytical time for each sample of 2.15 min. This modified LC-MS/MS method showed excellent analytical performance and demonstrated less matrix effect and a wide linear range. The design of multi-LC systems coupled with one mass spectrometry may play a notable role in the improvement of daily detection throughput, speeding up LC-MS/MS, and allowing it to be an integral part of continuous diagnostics in the near future.

Ultra-high throughput dual channel liquid chromatography with tandem mass spectrometry for quantification of four immunosuppressants in whole blood for therapeutic drug monitoring

Liquid chromatography with tandem mass spectrometry (LC-MS/MS) is the golden standard for immunosuppressants analyses, where optimising throughput by parallel chromatography can reduce costs and turnaround time. We aimed to double our system throughput using a dual LC-MS/MS setup. Therefore, two independent UPLC systems were hyphenated to one triple quadrupole MS, with staggered injections from one autosampler on alternating columns. The method simultaneously measured the analytes tacrolimus, sirolimus, everolimus, and cyclosporin A in whole blood using isotope dilution, with a run time of 1.5 min. Using the dual LC-MS/MS system, net run-to-run time improved from 2.3 to 0.98 min per injection, where throughput increased from 26 to 61 injections per hour. For Performance Qualification, 1101 clinical samples were measured on the dual LC-MS/MS system in addition to the standard system, during a period of one month, and the results were compared using Passing Bablok regression and Bland Altman analysis. There was excellent agreement for all four analytes, with regression slopes of 0.98-1.02x and intercepts of -0.11-0.88 µg/L. Minor bias was demonstrated between the systems with mean differences from -0.93 to 1.43%. In conclusion, the throughput was doubled and idle MS time was reduced with good agreement to the standard system. Currently, the method is applied for clinical routine with frequent peak intensities of >180 injections per day.

Expeditious quantification of plasma tacrolimus with liquid chromatography tandem mass spectrometry in solid organ transplantation

Traditionally, tacrolimus is assessed in whole blood samples, but this is suboptimal from the perspective that erythrocyte-bound tacrolimus is not a good representative of the active fraction. In this work, a straightforward and rapid method was developed for determination of plasma tacrolimus in solid organ transplant recipients, using liquid chromatography tandem mass spectrometry (LC-MS/MS) with heated electrospray ionisation. Sample preparation was performed through protein precipitation of 200 µl plasma with 500 µl stable isotopically labelled tacrolimus I.S. in methanol, where 20 µl was injected on the LC-MS/MS system. Separation was done using a chromatographic gradient on a C18 column (50 × 2.1 mm, 2.6 µm). The method was linear in the concentration range 0.05-5.00 µg/L, with within-run and between-run precision in the range 2-6 % and a run time of 1.5 min. Furthermore, the method was validated for selectivity, sensitivity, carry-over, accuracy and precision, process efficiency, recovery, matrix effect, and stability following EMA and FDA guidelines. Clinical validation was performed in 2333 samples from 1325 solid organ transplant recipients using tacrolimus (liver n = 312, kidney n = 1714, and lung n = 307), which had median plasma tacrolimus trough concentrations of 0.10 µg/L, 0.15 µg/L and 0.23 µg/L, respectively. This method is suitable for measurement of tacrolimus in plasma and will facilitate ongoing observational and prospective studies on the relationship of plasma tacrolimus concentrations with clinical outcomes.

Results From a Proficiency Testing Pilot for Immunosuppressant Microsampling Assays

BACKGROUND

Therapeutic drug monitoring (TDM) of immunosuppressive drugs is important for the prevention of allograft rejection in transplant patients. Several hospitals offer a microsampling service that provides patients the opportunity to sample a drop of blood from a fingerprick at home that can then be sent to the laboratory by mail. The aim of this study was to pilot an external quality control program.

METHODS

Fourteen laboratories from 7 countries participated (fully or partly) in 3 rounds of proficiency testing for the immunosuppressants tacrolimus, ciclosporin, everolimus, sirolimus, and mycophenolic acid. The microsampling devices included the following: Whatman 903 and DMPK-C, HemaXis, Mitra, and Capitainer-B. All assays were based on liquid chromatography with tandem mass spectrometry. In round 2, microsamples as well as liquid whole blood samples were sent, and 1 of these samples was a patient sample.

RESULTS

Imprecision CV% values for the tacrolimus microsamples reported by individual laboratories ranged from 13.2% to 18.2%, 11.7%-16.3%, and 12.2%-18.6% for rounds 1, 2, and 3, respectively. For liquid whole blood (round 2), the imprecision CV% values ranged from 3.9%-4.9%. For the other immunosuppressants, the results were similar. A great variety in analytical procedures was observed, especially the extraction method. For the patient sample, the microsample results led to different clinical decisions compared with that of the whole blood sample.

CONCLUSIONS

Immunosuppressant microsampling methods show great interlaboratory variation compared with whole blood methods. This variation can influence clinical decision-making. Thus, harmonization and standardization are needed. Proficiency testing should be performed regularly for laboratories that use immunosuppressant microsampling techniques in patient care.

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.

Tremor, Daily Functioning, and Health-Related Quality of Life in Solid Organ Transplant Recipients

Solid organ transplant recipients (SOTR) frequently report tremor. Data concerning tremor-related impairment and its potential impact on health-related quality of life (HRQoL) are lacking. This cross-sectional study assesses impact of tremor on activities of daily living and HRQoL using validated questionnaires among SOTR enrolled in the TransplantLines Biobank and Cohort Study. We included 689 SOTR (38.5% female, mean [±SD] age 58 [±14] years) at median [interquartile range] 3 [1-9] years after transplantation, of which 287 (41.7%) reported mild or severe tremor. In multinomial logistic regression analyses, whole blood tacrolimus trough concentration was an independent determinant of mild tremor (OR per µg/L increase: 1.11, 95% CI: 1.02 to 1.21, p = 0.019). Furthermore, in linear regression analyses, severe tremor was strongly and independently associated with lower physical and mental HRQoL (β = -16.10, 95% CI: -22.23 to -9.98, p < 0.001 and β = -12.68, 95% CI: -18.23 to -7.14, p < 0.001 resp.). SOTR frequently report tremor-related impairment of activities of daily living. Tacrolimus trough concentrations appeared as a main determinant of tremor among SOTR. The strong and independent association of tremor-related impairment with lower HRQoL warrants further studies into the effects of tacrolimus on tremor. Clinical Trial Registration: ClinicalTrials.gov, Identifier NCT03272841.

Comparison of LC-MS/MS and EMIT methods for the precise determination of blood sirolimus in children with vascular anomalies

Sirolimus (SRL) is a mammalian target of rapamycin (mTOR) inhibitor. The whole blood concentration of SRL is routinely monitored to tailor dosage and prevent toxicity. Currently, the enzyme multiplied immunoassay technique (EMIT) is often applied to perform therapeutic drug monitoring (TDM) of SRL, but the cross-reactivity with various metabolites is of great concern. A more specific method is required, such as liquid chromatography–tandem mass spectrometry (LC-MS/MS). However, no study on the method comparison of the EMIT and LC-MS/MS for the measurement of whole blood SRL concentration in children with vascular anomalies has been reported. This study developed a simple and sensitive LC-MS/MS assay for the determination of SRL. Meanwhile, consistency between LC-MS/MS and the EMIT was evaluated by linear regression and Bland–Altman analysis. Whole blood samples were deproteinized with methanol for erythrocyte lysis, and the resulting solution was injected into the LC-MS/MS system using the positive electrospray ionization mode. The multiple reaction monitoring transitions of m/z 931.7 → 864.6 and m/z 934.7 → 864.6 were used for SRL and SRL-d3 as the internal standards, respectively. The analytes were separated on a C18 column with a gradient mobile phase (0.1 mM formic acid and 0.05 mM ammonium acetate in methanol/ultrapure water). Blood samples collected from children with vascular anomalies undergoing SRL therapy were tested by EMIT and by LC-MS/MS. The linear range of LC-MS/MS was 0.500–50.0 ng/ml and that of the EMIT was 3.50–30.0 ng/ml. A significant positive correlation between the two assays was established with a regression equation described as [EMIT] = 1.281 × [LC−MS/MS] + 2.450 (r = 0.8361). Bland–Altman plots showed a mean concentration overestimation of 4.7 ng/ml [95% CI: (−3.1, 12.6)] and a positive bias of 63.1% [95% CI: (−36.1, 162.3)] generated by the EMIT more than that of by LC-MS/MS. In conclusion, the two methods were closely correlated, indicating that switching between the two methods is feasible. Considering the overestimation nature of the EMIT assay, switching from the EMIT to the LC-MS/MS method deserves close attention and necessary re-evaluation for the target therapeutic reference range, may be required when methods are switched within the same clinical laboratory or results are compared between different laboratories.

Simultaneous Determination of Six Immunosuppressants in Human Whole Blood by HPLC-MS/MS Using a Modified QuEChERS Method

A high-performance liquid chromatography-tandem mass spectrometry method was established for the simultaneous determination of mycophenolic acid, mycophenolate mofetil, tacrolimus, rapamycin, everolimus and pimecrolimus in human whole blood by optimizing the QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) preparation method. Whole blood was extracted into ethyl acetate, salted out with anhydrous magnesium sulfate, and purified with ethylenediamine-N-propyl silane adsorbent. The supernatant was evaporated under nitrogen until dry and finally reconstituted in methanol. Chromatographic separation was performed on an Agilent Poroshell 120 EC-C18 column in methanol (mobile phase A)-water (optimized for 0.1% acetic acid and 10 mM ammonium acetate, mobile phase B) at a 0.3 mL·min−1 flow rate. Electrospray ionization and positive ion multiple reaction monitoring were used for detection. The time for of analysis was 13 min. The calibration curves range of tacrolimus, rapamycin, everolimus and pimecrolimus were in the range of 1−100 ng·mL−1, mycophenolate mofetil in the range of 0.1−10 ng·mL−1 and mycophenolic acid at 10−1000 ng·mL−1. All correlation coefficients were >0.993. The coefficients of variation (CV, %) for inter-day and intra-day precision were less than 10%, while the spiked recoveries were in the range of 92.1% to 116%. Our method was rapid, sensitive, specific, and reproducible for the simultaneous determination of six immunosuppressants in human whole blood. Importantly, our approach can be used to monitor drug concentrations in the blood to facilitate disease treatment.

Review of the Use of Liquid Chromatography-Tandem Mass Spectrometry in Clinical Laboratories: Part I-Development

The process of method development for a diagnostic assay based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) involves several disparate technologies and specialties. Additionally, method development details are typically not disclosed in journal publications. Method developers may need to search widely for pertinent information on their assay(s). This review summarizes the current practices and procedures in method development. Additionally, it probes aspects of method development that are generally not discussed, such as how exactly to calibrate an assay or where to place quality controls, using examples from the literature. This review intends to provide a comprehensive resource and induce critical thinking around the experiments for and execution of developing a clinically meaningful LC-MS/MS assay.

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.

Simultaneous quantification of cyclosporin, tacrolimus, sirolimus and everolimus in whole blood by UHPLC-MS/MS for therapeutic drug monitoring

The aim of this study was to develop and validate a UHPLC-MS/MS assay to quantify cyclosporin (CYC), tacrolimus (TAC), sirolimus (SIR) and everolimus (EVE) in human whole blood for therapeutic drug monitoring. Analytes were extracted from 50 μL human whole blood by protein precipitation. The separation of the drugs was performed on an Acquity UPLC BEH C18 column. Analytes were eluted with a mobile phase consisting of 2 mM ammonium acetate with 0.1% formic acid (v/v) in deionised water and 2 mM ammonium acetate with 0.1% formic acid (v/v) in methanol at a flow rate of 300 μL/min in gradient elution. The method performance was evaluated by analysing patient blood samples and/or external quality control samples [proficiency testing (PT) scheme]. The method was linear from 23.75 to 1094.0, 1.3 to 42.4, 1.3 to 47.0 and 1.2-41.6 μg/mL for CYC, TAC, SIR and EVE, respectively. The within- and between-assay reproducibility results were ˂ 11%. Results from PT and patient sample quantification were comparable to those obtained previously by an in-house validated method using protein precipitation and liquid-liquid extraction. This method showed good analytical performance for quantifying CYC, TAC, SIR and EVE in whole blood over their respective calibration ranges.

Development and Validation of a Bioanalytical LC-MS/MS Method for Simultaneous Determination of Sirolimus in Porcine Whole Blood and Lung Tissue and Pharmacokinetic Application with Coronary Stents

Sirolimus is a hydrophobic macrolide compound that has been used for long-term immunosuppressive therapy, prevention of restenosis, and treatment of lymphangioleiomyomatosis. In this study, a simple and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed and validated for the simultaneous determination of sirolimus in both porcine whole blood and lung tissue. Blood and lung tissue homogenates were deproteinized with acetonitrile and injected into the LC-MS/MS system for analysis using the positive electrospray ionization mode. The drug was separated on a C18 reversed phase column with a gradient mobile phase (ammonium formate buffer (5 mM) with 0.1% formic acid and acetonitrile) at 0.2 mL/min. The selected reaction monitoring transitions of m/z 931.5 → 864.4 and m/z 809.5 → 756.5 were applied for sirolimus and ascomycin (the internal standard, IS), respectively. The method was selective and linear over a concentration range of 0.5–50 ng/mL. The method was validated for sensitivity, accuracy, precision, extraction recovery, matrix effect, and stability in porcine whole blood and lung tissue homogenates, and all values were within acceptable ranges. The method was applied to a pharmacokinetic study to quantitate sirolimus levels in porcine blood and its distribution in lung tissue following the application of stents in the porcine coronary arteries. It enabled the quantification of sirolimus concentration until 2 and 14 days in blood and in lung tissue, respectively. This method would be appropriate for both routine porcine pharmacokinetic and bio-distribution studies of sirolimus formulations.

Direct and Precise Measurement of Bevacizumab Levels in Human Plasma Based on Controlled Methionine Oxidation and Multiple Reaction Monitoring

Bevacizumab is a monoclonal antibody which targets vascular endothelial growth factor A (VEGF-A) and is used to treat various cancers and recently COVID-19. The dosage recommendations for bevacizumab are determined on the basis of body weight, and the drug is administered after defined time intervals, when it is presumed to still be above its minimum effective serum concentration. Interindividual and disease-stage-related variations in bevacizumab catabolism, however, can affect the proper dosing of patients, resulting in plasma concentrations which may not be within the optimal therapeutic window for the drug. Therapeutic drug monitoring (TDM) enables the assessment of patients' serum concentrations and allows personalized dosing which has the potential to improve efficacy and reduce side effects. While TMD is often performed using ligand-based assays, mass spectrometry (MS)-based TDM offers improved specificity. Here, we present a robust multiple reaction monitoring (MRM)-MS-based TDM method for the precise quantification of bevacizumab plasma concentrations, based on the controlled oxidation of the methionine-containing peptide, STAYLQMNSLR. The assay shows good linearity (r ² = 0.9951), robustness, and precision (CVs < 20%) for the quantification of bevacizumab, with a lower limit of quantification (S/N > 10) of 1.8 μg/mL of plasma, without the need for enrichment and requiring less than 1 μL of plasma and less than 6 h from sampling to result.

Impact of transiting from fluorescent polarisation immunoassay to high-performance liquid chromatography–tandem mass spectrometry for immunosuppressant levels analysis in kidney transplant patients

Background:

High-performance liquid chromatography–tandem mass spectrometry (HPLC-TMS) is preferred to fluorescent polarisation immunoassay (FPIA) in therapeutic drug monitoring (TDM), as it only measures active drug. Our hospital replaced FPIA with HPLC-TMS for analysis of calcineurin inhibitor (CNI) levels. Preliminary studies demonstrated significantly lower CNI levels with HPLC-TMS versus FPIA in kidney transplant recipients (KTRs). Most studies evaluating CNI exposure in KTRs used FPIA, posing challenges in interpreting HPLC-TMS levels. This study aimed to compare the effectiveness and safety outcomes in the one-year period before (FPIA period) and after (HPLC-TMS period) the switch.

Methods:

A retrospective cohort study was conducted on KTRs receiving ciclosporin (CsA) or tacrolimus (FK). Primary effectiveness end points were biopsy-proven acute rejection (BPAR) rate and estimated glomerular filtration rate (eGFR); safety end points were viral infections and hospitalisation for infection. The secondary end point was change in CNI levels during the FPIA versus HPLC-TMS periods.

Results:

A total of 307 patients were analysed (CsA n=182, FK n=125). BPAR only occurred in two patients in the HPLC-TMS period among the CsA cohort ( p=0.50), but it occurred in six patients in the FPIA period and one patient in the HPLC-TMS period ( p=0.13) among the FK cohort. Median eGFR were similar in both periods (CsA: 52.2 mL/min/1.73 m2 (interquartile range (IQR) 39.8–67.6) vs. 52.5 mL/min/1.73 m2 (IQR 37.1–68.0), p=0.65; FK: 57.7 mL/min/1.73 m2 (IQR 39.1–80.0) vs. 56.4 mL/min/1.73 m2 (IQR 33.5–76.7), p=0.08). There were no significant differences in safety outcomes. The median change in CNI levels from the FPIA period to the HPLC-TMS period was –20.5% (IQR –32.5 to –3.9) and –6.9% (IQR –17.7 to 8.0) among CsA and FK cohorts, respectively ( p<0.01).

Conclusion:

The switch from FPIA to HPLC-TMS for CNI TDM in KTRs did not yield significant changes in clinical end points.

Fluorocarbon Plasma Gas Passivation Enhances Performance of Porous Silicon for Desorption/Ionization Mass Spectrometry

Desorption/ionization on porous silicon mass spectrometry (DIOS-MS) is shown to be a powerful technique for the sensing of low-molecular-weight compounds, including drugs and their metabolites. Surface modification of DIOS surfaces is required to increase analytical performance and ensure stability. However, common wet chemical modification techniques use fluorosilanes, which are less suitable for high-throughput manufacturing and analytical repeatability. Here, we report an alternative, rapid functionalization technique for DIOS surfaces using plasma polymerization (ppDIOS). We demonstrate the detection of drugs, metabolites, pesticides, and doping agents, directly from biological matrices, with molecular confirmation performed using the fragmentation capabilities of a tandem MS instrument. Furthermore, the ppDIOS surfaces were found to be stable over a 162 day period with no loss of reproducibility and sensitivity. This alternative functionalization technique is cost-effective and amenable to upscaling, ensuring avenues for the high-throughput manufacture and detection of hundreds of analytes across various applications while still maintaining the gold-standard clinical technique using mass spectrometry.

Flucloxacillin decreases tacrolimus blood trough levels: a single-center retrospective cohort study

Purpose

Tacrolimus and everolimus are widely used to prevent allograft rejection. Both are metabolized by the hepatic cytochrome P450 (CYP) enzyme CYP3A4 and are substrate for P-glycoprotein (P-gp). Drugs influencing the activity or expression of CYP enzymes and P-gp can cause clinically relevant changes in the metabolism of immunosuppressants. Several case reports have reported that flucloxacillin appeared to decrease levels of drugs metabolized by CYP3A4 and P-gp. The magnitude of this decrease has not been reported yet.

Methods

In this single-center retrospective cohort study, we compared the tacrolimus and everolimus blood trough levels (corrected for the dose) before, during, and after flucloxacillin treatment in eleven transplant patients (tacrolimus n = 11 patients, everolimus n = 1 patient, flucloxacillin n = 11 patients).

Results

The median tacrolimus blood trough level decreased by 37.5% (interquartile range, IQR 26.4–49.7%) during flucloxacillin treatment. After discontinuation of flucloxacillin, the tacrolimus blood trough levels increased by a median of 33.7% (IQR 22.5–51.4%). A Wilcoxon signed-rank test showed statistically significantly lower tacrolimus trough levels during treatment with flucloxacillin compared with before (p = 0.009) and after flucloxacillin treatment (p = 0.010). In the only available case with concomitant everolimus and flucloxacillin treatment, the same pattern was observed.

Conclusions

Flucloxacillin decreases tacrolimus trough levels, possibly through a CYP3A4 and/or P-gp-inducing effect. It is strongly recommended to closely monitor tacrolimus and everolimus trough levels during flucloxacillin treatment and up to 2 weeks after discontinuation of flucloxacillin.

Electronic supplementary material

The online version of this article (10.1007/s00228-020-02968-z) contains supplementary material, which is available to authorized users.

Volumetric absorptive microsampling and dried blood spot microsampling vs. conventional venous sampling for tacrolimus trough concentration monitoring

Objectives

Monitoring tacrolimus blood concentrations is important for preventing allograft rejection in transplant patients. Our hospital offers dried blood spot (DBS) sampling, giving patients the opportunity to sample a drop of blood from a fingerprick at home, which can be sent to the laboratory by mail. In this study, both a volumetric absorptive microsampling (VAMS) device and DBS sampling were compared to venous whole blood (WB) sampling.

Methods

A total of 130 matched fingerprick VAMS, fingerprick DBS and venous WB samples were obtained from 107 different kidney transplant patients by trained phlebotomists for method comparison using Passing-Bablok regression. Bias was assessed using Bland-Altman. A multidisciplinary team pre-defined an acceptance limit requiring >80% of all matched samples within 15% of the mean of both samples. Sampling quality was evaluated for both VAMS and DBS samples.

Results

32.3% of the VAMS samples and 6.2% of the DBS samples were of insufficient quality, leading to 88 matched samples fit for analysis. Passing-Bablok regression showed a significant difference between VAMS and WB, with a slope of 0.88 (95% CI 0.81–0.97) but not for DBS (slope 1.00; 95% CI 0.95–1.04). Both VAMS (after correction for the slope) and DBS showed no significant bias in Bland-Altman analysis. For VAMS and DBS, the acceptance limit was met for 83.0% and 96.6% of the samples, respectively.

Conclusions

VAMS sampling can replace WB sampling for tacrolimus trough concentration monitoring, but VAMS sampling is currently inferior to DBS sampling, both regarding sample quality and agreement with WB tacrolimus concentrations.

Optimization of chromatography to overcome matrix effect for reliable estimation of four small molecular drugs from biological fluids using LC-MS/MS

The article describes a systematic study to overcome the matrix effect during chromatographic analysis of gemfibrozil, rivastigmine, telmisartan and tacrolimus from biological fluids using LC-ESI-MS/MS. All four methods were thoroughly developed by the appropriate choice of analytical column, elution mode and pH of mobile phase for improved chromatography and overall method performance. Matrix effect was assessed by post-column analyte infusion, slope of calibration line approach and post-extraction spiking. The best chromatographic conditions established were: Acquity BEH C₁₈ (50 × 2.1 mm, 1.7 μm) column with 5.0 mm ammonium acetate, pH 6.0-methanol as the mobile phase under gradient program for gemfibrozil; Luna CN (50 × 2.0 mm, 3 μm) column with a mobile phase consisting of acetonitrile-10 mm ammonium acetate, pH 7.0 (90:10, v/v) for rivastigmine; Inertsustain C₁₈ (100 × 2.0 mm, 5 μm) column using methanol-2.0 mm ammonium formate, pH 5.5 (80: 20, v/v) as the mobile phase for isocratic elution of telmisartan; and Acquity BEH C₁₈ (50 × 2.1 mm, 1.7 μm) with methanol-10 mm ammonium acetate, pH 6.0 (95:5, v/v) as mobile phase for tacrolimus. The methods were thoroughly validated as per European Medicines Agency and US Food and Drug Administration guidance and were successfully applied for pharmacokinetic studies in healthy subjects.

A 6 Second Analytical Method for Quantitation of Tacrolimus in Whole Blood by Use of Laser Diode Thermal Desorption Tandem Mass Spectrometry

BACKGROUND

Therapeutic drug monitoring of immunosuppressive drugs is imperative for organ transplant recipients. High-performance LC-MS/MS is considered gold standard; however, immunoassays provide rapid turnaround time. New technology was developed to reduce mass spectrometry analytical run-time. The laser diode thermal desorption source coupled with tandem mass spectrometry (LDTD-MS/MS) eliminates chromatographic separation to increase analytical throughput.

METHODS

A rapid, 6 second, LDTD-MS/MS analytical method was developed for the quantification tacrolimus in whole blood. Whole blood samples were lysed, followed by protein precipitation and solid-phase extraction. Extracted samples with desorption solution were spotted onto a LazWell plate then dried and loaded into the LDTD source for analysis with an AB SCIEX 5500 mass spectrometer in positive multiple reaction monitoring mode. The LDTD laser profile ramps from 0% to 65% of full power over 3 s and is held at 65% for 1 s before returning to initial conditions for 2 s.

RESULTS

Data presented include tacrolimus by LDTD-MS/MS comparison to LC-MS/MS, sensitivity, imprecision, interference, linearity, and stability. Method comparison between LDTD-MS/MS and a validated in-house LC-MS/MS assay yielded the following: (LDTD-MS/MS) = 1.119 (LC-MS/MS) + 0.23 ng/mL, S_y/x = 1.26, r = 0.9871 (n = 122). The limit of quantification by LDTD-MS/MS for tacrolimus was <0.3 ng/mL and total imprecision was <10%.

CONCLUSIONS

Laser diode thermal desorption tandem mass spectrometry technology can provide rapid turnaround time to result for tacrolimus. The analytical time for LDTD-MS/MS was 6 s compared to 135 s by LC-MS/MS, a >95% decrease in analytical time.

A new HPLC-MS/MS method for simultaneous determination of Cyclosporine A, Tacrolimus, Sirolimus and Everolimus for routine therapeutic drug monitoring

A rapid, simple and robust HPLC-MS/MS method for simultaneous determination of immunosuppressants Cyclosporine A, Tacrolimus, Sirolimus and Everolimus has been developed and validated. Sample of whole blood with volume of 50 μL was prepared by a protein precipitation with methanol and 0.5 mol. L^-1 ZnSO₄. Chromatographic separation was achieved on a Phenyl-Hexyl column by a gradient elution using 20 mmol.L^-1 ammonium formate/0.1% (v/v) formic acid in water (mobile phase A) and 20 mmol.L^-1 ammonium formate/0.1% (v/v) formic acid in methanol (mobile phase B) with flow rate 1 mL.min^-1. The run time was 3.5 min. Electrospray ionization and multiple reaction monitoring was used. The lower limit of quantification (LLOQ) was set at 0.5 μg.L^-1 for Tacrolimus, Sirolimus and Everolimus and 5 μg.L^-1 for Cyclosporine A. The method demonstrated adequate accuracy and precision with sufficient linearity range.

A multidrug LC–MS/MS method for the determination of five immunosuppressants in oral fluid

Aim: This study aimed: to develop and validate an LC–MS/MS method for mycophenolic acid, tacrolimus, sirolimus, everolimus and cyclosporin A in oral fluid (OF), as an essential tool to study the usefulness of OF as an alternative matrix for immunossuppressants’ therapeutic drug monitoring; and to find the best OF collector for these analytes. Materials & Methods: Chromatographic separation was achieved using an XBridge® Shield RP18 analytical column maintained at 65ºC, using 2 mM ammonium formate and 0.1% formic acid in water (A) and acetonitrile (B) as mobile phase. OF sample was extracted with solid phase extraction after sonication and protein precipitation. Results & Conclusions: Method validation met all the acceptance criteria. LODs were 0.05–1 ng/ml, and LOQs 0.1–5 ng/ml. Silanized tubes offered the best recoveries. The method was successfully applied to 31 OF specimens, describing everolimus detection in OF for the first time. Conclusion: The proposed method is sensitive enough for the detection of OF trough concentrations in patients receiving immunosuppressants when using an appropriate OF collector.

A high-throughput LC-MS/MS method for the quantification of four immunosu- ppressants drugs in whole blood

BACKGROUND

Immunoassays and liquid chromatography tandem mass spectrometry (LC-MS/MS) are two major methods for therapeutic drug monitoring (TDM) of immunosuppressant drugs. Compared to the relatively limited analytical performance and cross reactivities of immunoassays, the LC-MS/MS method is considered as a gold standard; however, the lack of systematic evaluation and standardization needs to be addressed.

METHODS

A LC-MS/MS method for the determination of cyclosporine A, sirolimus, tacrolimus, and everolimus was developed. One-step protein precipitation was used to prepare blood samples. The newly developed method was systematically evaluated and validated according to the standard guidelines.

RESULTS

The quantitative method for four immunosuppressant drugs in human whole blood was validated according to the guidelines. The lower limits of the measuring interval (LLMI) for cyclosporine A, sirolimus, tacrolimus, and everolimus were 5, 0.5, 0.5, and 0.5 ng/mL, respectively. Linear correlation coefficients were all >0.999. Internal standard-normalized (IS-normalized) matrix correction factor was within the range 0.88-1.17. The average spiked recoveries of five replicates for the four immunosuppressant drugs were in the range 87.4-109.6%.

CONCLUSION

An LC-MS/MS method combined with one-step protein precipitation was developed, providing short sample preparation and chromatographic run time, thus allowing easy clinical diagnosis.

Recent Trends in Fast Liquid Chromatography for Pharmaceutical Analysis

Background:

Liquid chromatography is the workhorse of analytical laboratories of pharmaceutical companies for analysis of bulk drug materials, intermediates, drug products, impurities and degradation products. This efficient technique is impeded by its long and tedious analysis procedures. Continuous efforts of scientists to reduce the analysis time resulted in the development of three different approaches namely, HTLC, chromatography using monolithic columns and UHPLC.

Methods:

Modern column technology and advances in chromatographic stationary phase including silica-based monolithic columns and reduction in particle and column size (UHPLC) have not only revolutionized the separation power of chromatographic analysis but also have remarkably reduced the analysis time. Automated ultra high-performance chromatographic systems equipped with state-ofthe- art software and detection systems have now spawned a new field of analysis, termed as Fast Liquid Chromatography (FLC). The chromatographic approaches that can be included in FLC are hightemperature liquid chromatography, chromatography using monolithic column, and ultrahigh performance liquid chromatography.

Results:

This review summarizes the progress of FLC in pharmaceutical analysis during the period from year 2008 to 2017 focusing on detecting pharmaceutical drugs in various matrices, characterizing active compounds of natural products, and drug metabolites. High temperature, change in the mobile phase, use of monolithic columns, new non-porous, semi-porous and fully porous reduced particle size of/less than 3μm packed columns technology with high-pressure pumps have been extensively studied and successively applied to real samples. These factors revolutionized the fast high-performance separations.

Conclusion:

Taking into account the recent development in fast liquid chromatography approaches, future trends can be clearly predicated. UHPLC must be the most popular approach followed by the use of monolithic columns. Use of high temperatures during analysis is not a feasible approach especially for pharmaceutical analysis due to thermosensitive nature of analytes.

Clinical application of a dried blood spot assay for sirolimus and everolimus in transplant patients

Background

Monitoring of immunosuppressive drugs such as everolimus and sirolimus is important in allograft rejection prevention in transplant patients. Dried blood spots (DBS) sampling gives patients the opportunity to sample a drop of blood from a fingerprick at home, which can be sent to the laboratory by mail.

Methods

A total of 39 sirolimus and 44 everolimus paired fingerprick DBS and whole blood (WB) samples were obtained from 60 adult transplant patients for method comparison using Passing-Bablok regression. Bias was assessed using Bland-Altman. Two validation limits were pre-defined: limits of analytical acceptance were set at >67% of all paired samples within 20% of the mean of both samples and limits of clinical relevance were set in a multidisciplinary team at >80% of all paired samples within 15% of the mean of both samples.

Results

For both sirolimus and everolimus, Passing-Bablok regression showed no differences between WB and DBS with slopes of 0.86 (95% CI slope, 0.72–1.02) and 0.96 (95% CI 0.84–1.06), respectively. Only everolimus showed a significant constant bias of 4%. For both sirolimus and everolimus, limits of analytical acceptance were met (76.9% and 81.8%, respectively), but limits or clinical relevance were not met (77.3% and 61.5%, respectively).

Conclusions

Because pre-defined limits of clinical relevance were not met, this DBS sampling method for sirolimus and everolimus cannot replace WB sampling in our center at this time. However, if the clinical setting is compatible with less strict limits for clinical relevance, this DBS method is suitable for clinical application.

An Introduction to Drug Testing: The Expanding Role of Mass Spectrometry

Measurement of drugs and their metabolites in biological fluids is the foundation of both therapeutic drug monitoring (TDM) and toxicology. The introduction of methods based on mass spectrometry (MS), coupled with gas or liquid chromatography, has revolutionized these areas. This chapter will introduce the reader to the application of MS to TDM and toxicology, the steps that should be considered during implementation and the processes that should be implemented to assure continued quality. Points of emphasis include advances and recent trends since the publication of the first edition of this book, such as high-resolution mass spectrometry and increased interest in alternate matrices.

Ultra-High Performance Liquid Chromatography Tandem Mass Spectrometry for Cyclosporine Analysis in Human Whole Blood and Comparison With an Antibody-Conjugated Magnetic Immunoassay

BACKGROUND

Various immunoassays have been used for cyclosporine A (CsA) analysis in human whole blood; however, they could not fully satisfy the requirements of criteria for accuracy and specificity in CsA measurement. The liquid chromatography tandem mass spectrometry is a gold method for CsA analysis. The aim of the study was to develop and validate an ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method for CsA analysis and establish its agreement with an antibody-conjugated magnetic immunoassay (ACMIA) in clinical sample analysis.

METHODS

An UHPLC-MS/MS method for CsA analysis in human whole blood was developed, validated, and applied in 85 samples, which were also tested by ACMIA. The agreement between UHPLC-MS/MS and ACMIA was evaluated by Bland-Altman plot.

RESULTS

The calibration range was 5-2000 ng/mL. The inaccuracy and imprecision were -4.60% to 5.56% and less than 8.57%, respectively. The internal standard-normalized recovery and matrix factor were 100.4%-110.5% and 93.5%-107.6%, respectively. The measurements of ACMIA and UHPLC-MS/MS were strongly correlated (r > 0.98). Evaluated by Bland-Altman plot, the 95% limit of agreement of the ACMIA:UHPLC-MS/MS ratio was 88.7%-165.6%, and the mean bias of the ratio was 21.1%.

CONCLUSIONS

A rapid, simple, accurate, and reliable UHPLC-MS/MS method for CsA analysis in human whole blood was developed, validated, and applied in 85 samples. On average, 21.1% overestimation was observed in ACMIA compared with that in the UHPLC-MS/MS. Further and larger studies are required to identify whether this degree of variance could be accepted by clinicians.

The Impact of Total Gastrectomy on Pharmacokinetics in Kidney Transplant Immunosuppressive Drug Regimes: A Case Study

BACKGROUND

Ensuring reliable gastrointestinal drug absorption of orally administered immunosuppressive medications posttransplant is critical to ensuring graft survival.

METHODS

A 66-year-old man of East Asian origin with a previous total gastrectomy was evaluated for living donor kidney transplantation. Pretransplant pharmacokinetic testing was performed to determine the most appropriate posttransplant medication strategy. The Gastrointestinal Quality of Life Index and Gastrointestinal Rating Scale questionnaires were administered to gauge immunosuppressive medication-related side effects in the absence of a stomach.

RESULTS

The patient's ability to absorb cyclosporin, tacrolimus (Tac), enteric-coated mycophenolate sodium (EC-MPS) and sirolimus (SRL) in oral dosage forms was well-preserved. Compared to nongastrectomy reference populations, the rate and extent of absorption of SRL and mycophenolic acid from EC-MPS were similar. The absorption of Tac and cyclosporin was greater than expected. Mycophenolate mofetil did not provide mycophenolic acid absorption as well as EC-MPS. The patient had worsened gastrointestinal symptoms with mycophenolate mofetil or EC-MPS in combination with Tac and cyclosporin, but this was not seen with isolated SRL.

CONCLUSIONS

This case demonstrates that commonly used postkidney transplantation immunosuppressive regimes may be prescribed after total gastrectomy as long as their limitations are noted.

Dried blood spot validation of five immunosuppressants, without hematocrit correction, on two LC–MS/MS systems

Aim: Hematocrit (Ht) effects remain a challenge in dried blood spot (DBS) sampling. The aim was to develop an immunosuppressant DBS assay on two LC–MS/MS systems covering a clinically relevant Ht range without Ht correction. Results: The method was partially validated for tacrolimus, sirolimus, everolimus, cyclosporin A and fully validated for mycophenolic acid on an Agilent and Thermo LC–MS/MS system. Bias caused by Ht effects were within 15% for all immunosuppressants between Ht levels of 0.23 and 0.48 l/l. Clinical validation of DBS versus whole blood samples for tacrolimus and cyclosporin A showed no differences between the two matrices. Conclusion: A multiple immunosuppressant DBS method without Ht correction, has been validated, including a clinical validation for tacrolimus and cyclosporin A, making this procedure suitable for home sampling.

Quantitative determination of four immunosuppressants by high resolution mass spectrometry (HRMS)

BACKGROUND

Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) utilizing triple-quadrupole instruments has been widely used for quantification of endogenous compounds, drugs or metabolites in clinical laboratories. In contrast, high-resolution mass spectrometry (HRMS) is typically used for compound identification due to its limited dynamic range. Recently HRMS instruments with enhanced linear dynamic range have become available. The aim of this study was to evaluate HRMS for fast quantitative applications in a clinical laboratory.

METHODS

A high throughput UPLC-TOF-MS assay for simultaneous quantification of cyclosporin A, tacrolimus, sirolimus and everolimus was developed. All immunosuppressants were analyzed as sodium adducts in TOF-only mode using an Agilent 6540 Q-TOF system. Extracted ion chromatograms of analytes and internal standards were created from full-scan data. The assay was evaluated and compared to an established LC-MS/MS assay according to CLSI recommendations.

RESULTS

The novel HRMS assay has a total run time of 3 min. The assay is linear in a clinical relevant concentration range for all four immunosupressants. Method correlations vs. established LC-MS/MS assay were between R2=0.99 and R2=0.97. Total coefficients of variation (CVT) ranges were 4.5%-6.4% (tacrolimus), 7.4%-8.0% (sirolimus), 8.0%-8.8% (everolimus) and 6.1%-7.4% (cyclosporine A) for three relevant concentration levels each.

CONCLUSIONS

High resolution TOF-MS and LC-MS/MS show equivalent quantitative performance for monitoring of cyclosporin A, tacrolimus, sirolimus and everolimus. HRMS has the potential to replace conventional LC-MS/MS in clinical laboratories because it simplifies assay development (no optimization of fragmentations and product ions necessary) and its full-scan data can provide additional information.