Therapeutic Drug Monitoring Of Immunosuppressants Research Articles

Immunsuppressiva-Medikamentenspiegelmessung – reine Routine? / Immunosuppressant drug monitoring: a routine undertaking?

Zusammenfassung Die Erfassung von Immunsuppressivaspiegel ist eine der anspruchsvollsten Medikamentenspiegelmessungen in der klinischen Routine. Die vergangenen Jahre haben eine Reihe von technologischen Fortschritten gebracht. Neben neuen immunologischen Analysesystemen hat sich die LC-MS/MS zu einem fixen Bestandteil des Geschehens entwickelt. Der vorliegende Beitrag soll helfen, Vor- und Nachteile der unterschiedlichen Assayformate zu erkennen. UKNEQAS-Ringversuchsergebnisse werden zur vergleichenden Assay-beurteilung herangezogen.

Toxicodynamic Therapeutic Drug Monitoring of Immunosuppressants: Promises, Reality, and Challenges

Although current immunosuppressive protocols have dramatically decreased acute rejection episodes, there has been less progress in terms of long-term graft survival after kidney transplantation over the last 2 decades. The key to reducing the damage to a transplanted organ as caused by chronic processes is early detection. Modern screening technologies in the fields of genetics, genomics, protein profiling (proteomics), and biochemical profiling (metabolomics) have opened new opportunities for the development of sensitive and specific diagnostic tools. Metabolic profiling appears to be a promising strategy because changes in the cell biochemistry are ultimately responsible for the histologic and pathophysiologic changes of the transplanted kidney and are most likely already detectable before histologic and pathophysiologic changes occur. Using truly no-targeted screening technologies as clinical diagnostic tools is not yet feasible, mostly because of the complexity of the data generated and the lack of algorithms to convert this information into clinically applicable information. A realistic and powerful targeted approach is the development of combinatorial biomarkers. These are biomarker patterns that typically consist of five or more individual parameters. Combined biomarker patterns confer significantly more information than a single measurement and, thus, can be expected to have better specificity and sensitivity. A series of studies in rats and healthy individuals evaluating the effects of immunosuppressants on urine metabolite patterns showed that immunosuppressant-induced changes of metabolite patterns in urine were associated with a combination of changes in glomerular filtration, changes in secretion/absorption by tubulus cells, and changes in kidney cell metabolism. These studies suggested that a combination of biomarkers that can be used for toxicodynamic therapeutic drug monitoring of immunosuppressants should include urine metabolites that constitute valid surrogate markers of these kidney functions.

Pharmacogenetics in Transplant Patients

Pharmacogenetics holds the potential to allow individualized dosing of immunosuppressive agents to optimize their therapeutic effect while minimizing adverse effects. As more pharmacogenetic information accumulates, the prospect of reducing or discontinuing the intensive therapeutic drug monitoring of immunosuppressants looks attractive. However, the long process of developing useful clinical information from basic information on the genes of interest is at a very early stage, and our present information does not supercede pharmacokinetic or blood concentration monitoring of immunosuppressants. The most extensive blood concentration/dose information available is on tacrolimus and its dosing related to CYP3A5 and ABCB1 gene polymorphisms. Although CYP3A5 genotype is definitely associated with tacrolimus dosing, the only recommendation presently published is for an arbitrary doubling of the starting tacrolimus dose in CYP3A5 expressors. For cyclosporine, sirolimus, and corticosteroids, the presently available pharmacogenetic information does not permit pharmacokinetic predictions. The pharmacodynamics of immunosuppressants, as evidenced by effects on acute rejection or adverse drug effects, have considerably more potential for prediction by pharmacogenetic models. Drug-resistant rejection, nephrotoxicity, steroid resistance and osteonecrosis, and even patient survival may ultimately be predicted by models incorporating multiple gene polymorphisms and other critical patient information. At this point, treatment algorithms can be developed that will allow us to individualize a transplant patient's immunosuppressive therapy.

CYP3A5 Genotype Does Not Influence the Blood Concentration of Tacrolimus Measured with the Abbott Immunoassay

Therapeutic drug monitoring of immunosuppressants is well established as an aid to optimizing patient management after allograft transplantation. Most laboratories measure cyclosporin and tacrolimus by immunoassays. However, measured values may be affected by the presence of circulating metabolites because of the limited specificity of the antibodies used in these assays. Cyclosporin is metabolized by the cytochrome P450 3A4 (CYP3A4) and cytochrome P450 3A5 (CYP3A5) enzymes. Studies on the biotransformation of cyclosporin by CYP3A4 and CYP3A5 have demonstrated disparate patterns of metabolite profiles between the 2 enzymes for this substrate. CYP3A4 catalyzes the formation of 3 primary cyclosporin metabolites; 2 are monohydroxylated (AM1 and AM9), and the third is demethylated (AM4N). CYP3A5 produces only the AM9 metabolite (1). This may have important implications for immunoassay measurements of cyclosporin, as polymorphic expression of the CYP3A5 gene leads to some individuals not producing the CYP3A5 …

An Automated High-throughput Lc/lc-ms/ms Platform For The Clinical Therapeutic Drug Monitoring Of Immunosuppressants

s: Ninth International Congress of Therapeutic Drug Monitoring and Clinical Toxicology: Louisville, Kentucky April 23-28, 2005

Rapid simultaneous quantification of immunosuppressants in transplant patients by turbulent flow chromatography combined with tandem mass spectrometry

Background: Immunosuppressant therapeutic drug monitoring (TDM) is an important requirement in the management of post-transplant patients. Our aim was to develop and evaluate a robust high-throughput method using turbulent flow chromatography (TFC) coupled with liquid chromatography–tandem mass spectrometry (LC–MS/MS) for the simultaneous quantification of cyclosporin A (CsA), tacrolimus (FK 506) and sirolimus. Methods: A total of 1483 EDTA-blood pre-dosage samples from 147 kidney, 67 liver, 15 kidney/pancreas, and 48 bone marrow recipients were collected. After hemolysis and protein precipitation of 50 μl blood, fast and efficient on-line matrix elimination was achieved using turbulent flow chromatography. Tandem mass spectrometric detection and quantification was performed using multiple reaction monitoring (MRM). Results: The total analysis time of the column switching method was 3 min. The method was linear from 4.5 to 1500 ng/ml for cyclosporin A, from 0.2 to 100 ng/ml for tacrolimus, and from 0.4 to 100 ng/ml for sirolimus. The accuracy was >95%. Within and between-run assay variation coefficients ranged from 2.4% to 9.3%. Excellent correlation with other standard methods (immunoassay, HPLC) was observed. Conclusions: The presented turbulent flow chromatography–tandem mass spectrometric platform offers a very fast, simple and economical method with an excellent validation profile and is well suited for daily pre- and post-dosage immunosuppressant monitoring.

Supercritical Fluid Chromatography for Therapeutic Drug Monitoring of Immunosuppressants: Selectivity for Cyclosporine A, Fk 506 (Tacrolimus), and Rapamycin

Abstract Clinical monitoring of cyclosporine A (CsA) in whole blood is currently performed by either immunoassays or high-performance liquid chromatography. A new immunosuppressant, FK 506—Tacrolimus, is currently undergoing multi-centers clinical trial for liver transplant, while active research and clinical studies are being performed for another new immunosuppressant, rapamycin. The present study investigated their chromatographic selectivities by supercritical fluid chromatography, in comparison to HPLC. Feasibility studies were performed for the analyses of extracts of whole blood samples, after solid-phase extraction. SFC analyses were performed by using an open tubular SB-biphenyl capillary column, CO2 as the mobile phase, pressure programming from 100 to 300 atmospheres, separation temperature of 70°C, and FID detection. CsA eluted after the internal standard CsD, while FK 506 tautomer eiuted after FK 506. From the “reversal” of elution order as compared to reversed-phase LC, the selectivity of th...