Ten years ago, a consensus report on the optimization of tacrolimus was published in this journal. In 2017, the Immunosuppressive Drugs Scientific Committee of the International Association of ...Therapeutic Drug Monitoring and Clinical Toxicity (IATDMCT) decided to issue an updated consensus report considering the most relevant advances in tacrolimus pharmacokinetics (PK), pharmacogenetics (PG), pharmacodynamics, and immunologic biomarkers, with the aim to provide analytical and drug-exposure recommendations to assist TDM professionals and clinicians to individualize tacrolimus TDM and treatment. The consensus is based on in-depth literature searches regarding each topic that is addressed in this document. Thirty-seven international experts in the field of TDM of tacrolimus as well as its PG and biomarkers contributed to the drafting of sections most relevant for their expertise. Whenever applicable, the quality of evidence and the strength of recommendations were graded according to a published grading guide. After iterated editing, the final version of the complete document was approved by all authors. For each category of solid organ and stem cell transplantation, the current state of PK monitoring is discussed and the specific targets of tacrolimus trough concentrations (predose sample C0) are presented for subgroups of patients along with the grading of these recommendations. In addition, tacrolimus area under the concentration-time curve determination is proposed as the best TDM option early after transplantation, at the time of immunosuppression minimization, for special populations, and specific clinical situations. For indications other than transplantation, the potentially effective tacrolimus concentrations in systemic treatment are discussed without formal grading. The importance of consistency, calibration, proficiency testing, and the requirement for standardization and need for traceability and reference materials is highlighted. The status for alternative approaches for tacrolimus TDM is presented including dried blood spots, volumetric absorptive microsampling, and the development of intracellular measurements of tacrolimus. The association between CYP3A5 genotype and tacrolimus dose requirement is consistent (Grading A I). So far, pharmacodynamic and immunologic biomarkers have not entered routine monitoring, but determination of residual nuclear factor of activated T cells-regulated gene expression supports the identification of renal transplant recipients at risk of rejection, infections, and malignancy (B II). In addition, monitoring intracellular T-cell IFN-g production can help to identify kidney and liver transplant recipients at high risk of acute rejection (B II) and select good candidates for immunosuppression minimization (B II). Although cell-free DNA seems a promising biomarker of acute donor injury and to assess the minimally effective C0 of tacrolimus, multicenter prospective interventional studies are required to better evaluate its clinical utility in solid organ transplantation. Population PK models including CYP3A5 and CYP3A4 genotypes will be considered to guide initial tacrolimus dosing. Future studies should investigate the clinical benefit of time-to-event models to better evaluate biomarkers as predictive of personal response, the risk of rejection, and graft outcome. The Expert Committee concludes that considerable advances in the different fields of tacrolimus monitoring have been achieved during this last decade. Continued efforts should focus on the opportunities to implement in clinical routine the combination of new standardized PK approaches with PG, and valid biomarkers to further personalize tacrolimus therapy and to improve long-term outcomes for treated patients.
When mycophenolic acid (MPA) was originally marketed for immunosuppressive therapy, fixed doses were recommended by the manufacturer. Awareness of the potential for a more personalized dosing has led ...to development of methods to estimate MPA area under the curve based on the measurement of drug concentrations in only a few samples. This approach is feasible in the clinical routine and has proven successful in terms of correlation with outcome. However, the search for superior correlates has continued, and numerous studies in search of biomarkers that could better predict the perfect dosage for the individual patient have been published. As it was considered timely for an updated and comprehensive presentation of consensus on the status for personalized treatment with MPA, this report was prepared following an initiative from members of the International Association of Therapeutic Drug Monitoring and Clinical Toxicology (IATDMCT). Topics included are the criteria for analytics, methods to estimate exposure including pharmacometrics, the potential influence of pharmacogenetics, development of biomarkers, and the practical aspects of implementation of target concentration intervention. For selected topics with sufficient evidence, such as the application of limited sampling strategies for MPA area under the curve, graded recommendations on target ranges are presented. To provide a comprehensive review, this report also includes updates on the status of potential biomarkers including those which may be promising but with a low level of evidence. In view of the fact that there are very few new immunosuppressive drugs under development for the transplant field, it is likely that MPA will continue to be prescribed on a large scale in the upcoming years. Discontinuation of therapy due to adverse effects is relatively common, increasing the risk for late rejections, which may contribute to graft loss. Therefore, the continued search for innovative methods to better personalize MPA dosage is warranted.
Tacrolimus (TAC) is an immunosuppressive drug used after organ transplantation. Dosing is adjusted using whole blood (WB-TAC) measurements. Patients within the therapeutic WB-TAC window still ...experience rejections and adverse effects. Alternative monitoring methods are therefore warranted. The authors developed a method for measuring TAC in peripheral blood mononuclear cell (PBMC) isolates (PBMC-TAC) and performed a pharmacokinetic study in a cohort of kidney transplant patients during the first year after transplantation.
PBMCs were isolated from whole blood by gradient centrifugation. After methanol-based extraction, liquid chromatography with tandem mass spectrometry was used to determine TAC in the extract. PBMC-TAC was normalized to the number of cells and alternatively to the protein amount in cells. Predose and postdose (1.5 hours) samples from kidney transplant patients were collected at 1 week, 6 weeks, and 1 year after transplantation. WB-TAC was measured using immunoassay.
The PBMC-TAC assay fulfilled the validation criteria of the European Medicines Agency guidelines. Twenty-nine patients completed the study. Predose PBMC-TAC was (median) 23 (1 week), 33 (6 weeks), and 27 pg/10 cells (1 year). Postdose PBMC-TAC was 44, 30, and 27 pg/10 cells at 1 week, 6 weeks, and 1 year after transplantation, respectively. Predose WB-TAC (median) was 5.0, 6.0, and 5.4 mcg/L, and postdose WB-TAC was 10.5, 8.3, and 9.1 mcg/L, respectively, at 1 week, 6 weeks, and 1 year after transplantation. Whole blood and PBMC-TAC correlated at all timepoints (rho 0.40-0.82, P < 0.05) except before dosage at 6 weeks. PBMC-TAC normalized to the number of cells, and the amount of protein was modestly correlated (rho 0.36-0.81, P < 0.056).
The correlation between WB-TAC and PBMC-TAC is modest during the first-year posttransplantation. Normalization of PBMC-TAC to cells or protein may yield different results. PBMC-TAC is increased 1.5 hours after dose at 1 week after transplantation, but not after 6 weeks or 1 year, indicating altered distribution kinetics.
Adoptive transfer of autologous polyclonal regulatory T cells (Tregs) is a promising option for reducing graft rejection in allogeneic transplantation. To gain therapeutic levels of Tregs there is a ...need to expand obtained cells ex vivo, usually in the presence of the mTOR inhibitor Rapamycin due to its ability to suppress proliferation of non-Treg T cells, thus promoting a purer Treg yield. Azithromycin is a bacteriostatic macrolide with mTOR inhibitory activity that has been shown to exert immunomodulatory effects on several types of immune cells. In this study we investigated the effects of Azithromycin, compared with Rapamycin, on Treg phenotype, growth, and function when expanding bulk, naïve, and memory Tregs. Furthermore, the intracellular concentration of Rapamycin in CD4+ T cells as well as in the culture medium was measured for up to 48 h after supplemented. Treg phenotype was assessed by flow cytometry and Treg function was measured as inhibition of responder T-cell expansion in a suppression assay. The concentration of Rapamycin was quantified with liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Azithromycin and Rapamycin both promoted a FoxP3-positive Treg phenotype in bulk Tregs, while Rapamycin also increased FoxP3 and FoxP3+Helios positivity in naïve and memory Tregs. Furthermore, Rapamycin inhibited the expansion of naïve Tregs, but also increased their suppressive effect. Rapamycin was quickly degraded in 37°C medium, yet was retained intracellularly. While both compounds may benefit expansion of FoxP3+ Tregs in vitro, further studies elucidating the effects of Azithromycin treatment on Tregs are needed to determine its potential use.
Aims
To explore the pharmacodynamics of mycophenolic acid (MPA) through inosine monophosphate dehydrogenase (IMPDH) capacity measurement and purine levels in peripheral blood mononuclear cells (PBMC) ...longitudinally during the first year after renal transplantation (TX).
Methods
PBMC were isolated from renal recipients 0–4 days prior to and 6–9 days, 5–7 weeks and 1 year after TX (before and 1.5 hours after dose). IMPDH capacity and purine (guanine and adenine) levels were measured in stimulated and nonstimulated PBMC.
Results
Twenty‐nine patients completed the follow‐up period, of whom 24 received MPA. In stimulated PBMC, the IMPDH capacity (pmol 10−6 cells min−1) was median (interquartile range) 127 (95.8–147) before TX and thereafter 44.9 (19.2–93.2) predose and 12.1 (4.64–23.6) 1.5 hours postdose across study days after TX. The corresponding IMPDH capacity in nonstimulated PBMC was 5.71 (3.79–6.93), 3.35 (2.31–5.62) and 2.71 (1.38–4.08), respectively. Predose IMPDH capacity in nonstimulated PBMC increased with time, reaching pre‐TX values at 1 year. In stimulated PBMC, both purines were reduced before (median 39% reduction across days after TX) and after (69% reduction) dose compared to before TX. No alteration in the purine levels was observed in nonstimulated PBMC. Patients needing dose reductions during the first year had lower pre‐dose IMPDH capacity in nonstimulated PBMC (1.87 vs 3.00 pmol 10−6 cells min−1, P = .049) at 6–9 days.
Conclusion
The inhibitory effect of MPA was stronger in stimulated PBMC. Nonstimulated PBMC became less sensitive to MPA during the first year after TX. Early IMPDH capacity appeared to be predictive of dose reductions.
To compare clinical and psychological factors among patients with self-perceived statin-associated muscle symptoms (SAMS), confirmed SAMS, and refuted SAMS in coronary heart disease patients (CHD).
...Data were obtained from a cross-sectional study of 1100 CHD outpatients and a study of 71 CHD outpatients attending a randomized, double-blinded, placebo-controlled, crossover study to test effects of atorvastatin 40 mg/day on muscle symptom intensity. Clinical and psychosocial factors were compared between patients with and without SAMS in the cross-sectional study, and between patients with confirmed SAMS and refuted SAMS in the randomized study.
Bilateral, symmetric muscle symptoms in the lower extremities during statin treatment were more prevalent in patients with confirmed SAMS compared to patients with refuted SAMS (75% vs. 41%, p = 0.01) in the randomized study. No significant differences in psychological factors (anxiety, depression, worry, insomnia, type D personality characteristics) were detected between patients with and without self-perceived SAMS in the cross-sectional study, or between patients with confirmed SAMS and refuted SAMS, in the randomized study.
Patients with confirmed SAMS more often present with bilateral lower muscle symptoms compared to those with refuted SAMS. Psychological factors were not associated with self-perceived SAMS or confirmed SAMS. A careful pain history and a search for alternative causes of muscle symptoms are likely to promote communication in patients with SAMS, and may reduce the risk for statin discontinuation.
Gemcitabine resistance in pancreatic ductal adenocarcinoma (PDAC) is attributed to cancer cell-intrinsic drug processing and the impact of the tumor microenvironment, especially pancreatic stellate ...cells (PSCs). This study uses human PDAC-derived paired primary cancer cells (PCCs) and PSCs from four different tumors, and the PDAC cell lines BxPC-3, Mia PaCa-2, and Panc-1, to assess the fate of gemcitabine by measuring its cellular uptake, cytotoxicity, and LC-MS/MS-based metabolite analysis. Expression analysis and siRNA-mediated knockdown of key regulators of gemcitabine (hENT1, CDA, DCK, NT5C1A) was performed. Compared to PSCs, both the paired primary PCCs and cancer cell lines showed gemcitabine-induced dose-dependent cytotoxicity, high uptake, as well as high and variable intracellular levels of gemcitabine metabolites. PSCs were gemcitabine-resistant and demonstrated significantly lower drug uptake, which was not influenced by co-culturing with their paired PCCs. Expression of key gemcitabine regulators was variable, but overall strong in the cancer cells and significantly lower or undetectable in PSCs. In cancer cells, hENT1 inhibition significantly downregulated gemcitabine uptake and cytotoxicity, whereas DCK knockdown reduced cytotoxicity. In conclusion, heterogeneity in gemcitabine processing among different pancreatic cancer cells and stellate cells results from the differential expression of molecular regulators which determines the effect of gemcitabine.
Background. New-onset diabetes after transplantation may be associated with the use of tacrolimus (Tac) causing impaired insulin release or reduced insulin sensitivity. Such effects have not been ...studied in renal transplant recipients receiving traditional twice-daily tacrolimus (TacBID) and then compared to the new once-daily prolonged release formulation of tacrolimus (TacOD).
Methods. We performed a prospective crossover study of 20 stable non-diabetic renal transplant recipients. All patients underwent one hyperglycaemic clamp on TacBID (3.8 ±2.2 mg/day) and a new clamp 4-6 weeks after a 1:1 mg/day switch to TacOD (4.0 ±2.8 mg/day).
Results. Tac trough concentrations decreased from 6.6 ± 2.9 to 5.4 ± 1.4 μg/mL (P = 0.037) and Tac max from 21.3 ± 8.4 to 15.2 ± 3.5 μg/L (P = 0.001). Tac AUC0-24 was reduced from 265 ± 112 to 218 ± 47 μg × h/L (P = 0.12). The hyperglycaemic clamp did not detect any change in insulin sensitivity index after conversion 0.26 ± 0.21 versus 0.26 ± 0.25 μmol/min/kg/(pmol/L insulin), P = 0.99 nor any change in first (334 ± 274 versus 353 ± 248 μIU × min/mL, P = 0.41) or second phase insulin secretion (224 ± 155 versus 263 ± 210 μIU × min/mL/mmol glucose, P = 0.60) on TacBID versus TacOD.
Conclusions. Conversion from standard TacBID to TacOD on a 1:1 mg basis is safe. In spite of a reduced Tac exposure, there was no change in insulin release or sensitivity in renal transplant recipients.
High daily doses of marine omega-3 fatty acids (FAs) from fish and seafood may have beneficial cardiovascular effects in renal transplant recipients (RTRs) (1, 2). A recent randomized clinical trial ...demonstrated that daily supplementation with high-dose marine omega-3 FAs lowered plasma triglyceride and C-reactive protein levels (1). In some parts of the world, high intake of marine omega-3 FAs is recommended for the general population and it is likely that RTRs use omega-3 FA supplements without consulting a transplant physician (2). Previous reports indicate increased systemic exposures of cyclosporine and sirolimus in patients receiving high-dose marine omega-3 FA supplements (3, 4) which could be related to reduced drug metabolism supported by the in vitro experimental observation of an inhibitory effect of omega-3 FAs on cytochrome P450 (CYP) 3A enzymes (5) expressed in the intestine and liver. The present study aimed to examine the effect of marine omega-3 FAs on the pharmacokinetics of tacrolimus.
Statin-associated muscle symptoms (SAMS) is a prevalent cause of statin discontinuation. It is challenging and time-consuming for clinicians to assess whether symptoms are caused by the statin or ...not, and diagnostic biomarkers are requested. Atorvastatin metabolites have been associated with SAMS. We aimed to compare atorvastatin pharmacokinetics between coronary heart disease (CHD) patients with and without clinically statin intolerance and statin-dependent histopathological alterations in muscle tissue. Secondarily we aimed to assess genetic variants relevant for the observed pharmacokinetic variables.
Twenty-eight patients with CHD and subjective SAMS were included in the exploratory MUSE biomarker study in 2020. Participants received atorvastatin 40 mg/day for seven weeks followed by no statins for eight weeks. Muscle biopsies and blood were collected at the end of each period. Four patients were categorized as clinically intolerant to ≥3 statins prior to study start whereas four patients had signs of muscle cell damage during treatment.
We found significantly lower levels of atorvastatin acids, and higher lactone/acid ratios in the statin intolerant, both in muscle and plasma. With optimal cut-off, the combination of 2-OH-atorvastatin acid and the 2-OH-atorvastatin lactone/acid ratio provided sensitivity, specificity, and predictive values of 100 %. Patients with variants in UGT1A1 and UGT1A3 had higher lactone metabolite levels than those with wild type, both in muscle and plasma.
Atorvastatin metabolites appear promising as biomarkers for the identification of clinical statin intolerance in patients with self-perceived SAMS, but the findings have to be confirmed in larger studies.
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