Development and Validation of A Liquid Chromatography-Tandem Mass Spectrometry Method to Simultaneously Measure Tacrolimus and Everolimus Concentrations in Kidney Allograft Biopsies After Kidney Transplantation

Overview of therapeutic drug monitoring and clinical practice

With the rapid development of clinical pharmacy in China, therapeutic drug monitoring (TDM) has become an essential tool for guiding rational clinical drug use and is widely concerned. TDM is a tool that combines pharmacokinetic and pharmacodynamic knowledge to optimize personalized drug therapy, which can improve treatment outcomes, reduce drug-drug toxicity, and avoid the risk of developing drug resistance. To effectively implement TDM, accurate and sophisticated analytical methods are required. By researching the literature published in recent years, we summarize the types of commonly monitored drugs, therapeutic windows, and clinical assays and track the trends and hot spots of therapeutic drug monitoring. The purpose is to provide guidelines for clinical blood drug concentration monitoring, to implement individualized drug delivery programs better, to ensure the rational use of drugs for patients, and to provide a reference for the group to carry out related topics in the future.

Blood, Cellular, and Tissular Calcineurin Inhibitors Pharmacokinetic-Pharmacodynamic Relationship in Heart Transplant Recipients: The INTRACAR Study

BACKGROUND

After heart transplantation, calcineurin inhibitors (CNI) (cyclosporin A and tacrolimus) are key immunosuppressive drugs to prevent graft rejection. Whole-blood concentration (C blood )-guided therapeutic drug monitoring (TDM) is systematically performed to improve graft outcomes. However, some patients will still experience graft rejection and/or adverse events despite CNI C blood within the therapeutic range. Other pharmacokinetic parameters, such as the intragraft, or intracellular concentration at the CNI site of action could refine their TDM. Nonetheless, these remain to be explored. The objective of the INTRACAR study was to describe the relationship between whole blood, intragraft, and intracellular CNI concentrations as well as their efficacy in heart transplant recipients (HTR).

METHODS

In a cohort of HTR, protocol endomyocardial biopsies (EMB) were collected to assess rejection by anatomopathological analysis. Part of the EMB was used to measure the intragraft concentrations of CNI (C EMB ). C blood and the concentration inside peripheral blood mononuclear cells, (C PBMC ), a cellular fraction enriched with lymphocytes, were also monitored. Concentrations in the 3 matrices were compared between patients with and without biopsy-proven acute rejection (BPAR).

RESULTS

Thirty-four HTR were included, representing nearly 100 pharmacokinetic (PK) samples for each CNI. C blood , C EMB , and C PBMC correlated for both CNI. BPAR was observed in 74 biopsies (39.6%) from 26 patients (76.5%), all except one was of low grade. None of the PK parameters (C blood , C EMB , C PBMC , C EMB/blood , and C PBMC/blood ) was associated with BPAR.

CONCLUSIONS

In this cohort of well-immunosuppressed patients, no association was observed for any of the PK parameters, including C blood , with the occurrence of BPAR. However, a trend was noticed for the C EMB and C EMB/blood of cyclosporin A. Further studies in higher-risk patients may help optimize the use of C EMB and C PBMC for CNI TDM in HTR.

Evaluation of a batched-extraction method for measurement of sirolimus, tacrolimus, and cyclosporine on the Architect i2000SR

BACKGROUND

Manual extraction of immunosuppressants is required before measurement on the Architect immunoassay analyzer. The individual extraction of samples places clinical laboratory staff at risk for ergonomic injury. We evaluated the analytical performance of a batched extraction method for measuring sirolimus, tacrolimus, and cyclosporine using the Architect i2000SR.

METHODS

Residual whole blood samples from patients receiving immunosuppressant therapy were used for evaluation. The analytical evaluation included imprecision, linearity, and method comparison. Technologist-to-technologist variation was also assessed.

RESULTS

Total imprecision ranged from 2.58-3.13% for sirolimus, 2.70-3.77% for tacrolimus, and 7.82-12.41% for cyclosporine. Linearity was verified from 0.44 - 19.49 μg/l for sirolimus, 0.05-26.15 μg/l for tacrolimus, and 0.15-991.55 μg/l for cyclosporine. Deming regression analysis showed slope and intercept were not significant for either technologist-to-technologist comparison or for batched vs. individual processing comparison. Bland-Altman analysis of individual vs. batched processing revealed a mean bias of 1.29% (LLOA: -14.63%, ULOA: 17.21%) for sirolimus, 2.07% (LLOA: -10.87%, ULOA: 15%) for tacrolimus, and -1.56% (LLOA: -20.05%, ULOA: 16.94%) for cyclosporine. The values were not significantly different from the bias and LLOAs observed for technologist-to-technologist comparison.

CONCLUSIONS

The imprecision and linearity of batched methods met analytical goals. The batched method also correlated well with the individual extraction methods. The ULOA and LLOA for all drugs tested exceeded a TAE or ± 15%. However, similar range of differences was observed between technologists, suggesting that batch processing did not increase or reduce variability due to manual preparation steps.