Pharmacokinetic optimization of immunosuppressive therapy in thoracic transplantation: part II

Everolimus Personalized Therapy: Second Consensus Report by the International Association of Therapeutic Drug Monitoring and Clinical Toxicology

ABSTRACT

The Immunosuppressive Drugs Scientific Committee of the International Association of Therapeutic Drug Monitoring and Clinical Toxicology established the second consensus report to guide therapeutic drug monitoring (TDM) of everolimus (EVR) and its optimal use in clinical practice 7 years after the first version was published in 2016. This version provides information focused on new developments that have arisen in the last 7 years. For the general aspects of the pharmacology and TDM of EVR that have retained their relevance, readers can refer to the 2016 document. This edition includes new evidence from the literature, focusing on the topics updated during the last 7 years, including indirect pharmacological effects of EVR on the mammalian target of rapamycin complex 2 with the major mechanism of direct inhibition of the mammalian target of rapamycin complex 1. In addition, various concepts and technical options to monitor EVR concentrations, improve analytical performance, and increase the number of options available for immunochemical analytical methods have been included. Only limited new pharmacogenetic information regarding EVR has emerged; however, pharmacometrics and model-informed precision dosing have been constructed using physiological parameters as covariates, including pharmacogenetic information. In clinical settings, EVR is combined with a decreased dose of calcineurin inhibitors, such as tacrolimus and cyclosporine, instead of mycophenolic acid. The literature and recommendations for specific organ transplantations, such as that of the kidneys, liver, heart, and lungs, as well as for oncology and pediatrics have been updated. EVR TDM for pancreatic and islet transplantation has been added to this edition. The pharmacodynamic monitoring of EVR in organ transplantation has also been updated. These updates and additions, along with the previous version of this consensus document, will be helpful to clinicians and researchers treating patients receiving EVR.

Pharmacokinetic-based Dosing Individualization of Mycophenolate Mofetil in Solid Organ Transplanted Patients

Mycophenolate mofetil (MMF) is an immunosuppressant drug approved for prophylaxis of transplant rejection in patients undergoing solid organ transplantation and is further employed in management of various autoimmune disorders. MMF exhibits notable pharmacokinetic inter- and intraindividual variability necessitating tailored therapeutic approaches to achieve optimal therapeutic outcomes while mitigating risks of adverse effects. The objective of this review was to summarize factors that influence the pharmacokinetics of MMF and its active metabolite mycophenolic acid in order to deduce recommendations for personalized treatment strategies. Presumed predictors were analysed in relation to each of the four pharmacokinetic phases, providing tools and targets for MMF dosing optimization amenable to clinical implementation.

Effects of CYP3A5 Genetic Polymorphisms on the Weight-adjusted through Concentration of Sirolimus in Renal Transplant Recipients: A Systematic Review and Meta-analysis

BACKGROUND

Sirolimus, one of the immunosuppressive drugs administered to renal transplant recipients, is metabolized by cytochrome P450 (CYP) 3A5. Accordingly, CYP3A5 polymorphism is a genetic factor affecting sirolimus pharmacokinetics (PK). Therefore, we conducted a systematic review and meta-analysis on the association between sirolimus PK and CYP3A5*3 polymorphism.

METHODS

We searched for studies published up to 13 June 2024 from PubMed, Embase, Cochrane Library, and Web of Science. We reviewed studies on the relationship between CYP3A5*3 polymorphism and weightadjusted trough concentration/dose (C0 /D) ratio and dosage of sirolimus in renal transplant recipients, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We evaluated mean differences (MDs) and 95% confidence intervals (CIs).

RESULTS

A total of seven studies were included. The weight-adjusted C0 /D ratio of sirolimus was significantly higher in patients with the CYP3A5*3/*3 rather than CYP3A5*1/*1 or CYP3A5*1/*3 genotype (MD 95.27 ng/mL per mg/kg; 95% CI: 58.06, 132.47; I2 = 74%; p < 0.00001). Also, the weight-adjusted dosage of sirolimus was significantly lower in patients with the CYP3A5*3/*3 rather than CYP3A5*1/*1 or CYP3A5*1/*3 genotype (MD -2.60 × 10-3 mg/kg; 95% CI: -4.52, -0.69; I2 = 44%; p = 0.008).

CONCLUSION

Our meta-analysis showed a significant effect for the CYP3A5*3 genotype on weight-adjusted C0 /D ratio and dosage of sirolimus in adult renal transplant recipients.

Three Layers of Personalized Medicine in the Use of Sirolimus and Its Derivatives for the Treatment of Cancer

Rapamycin and its derivatives are mTOR inhibitors which are FDA-approved for use as immunosuppressants and chemotherapeutic agents. These agents are currently approved to treat renal cell carcinomas, soft tissue sarcomas, and other rare tumors. As tumor treatment paradigms are moving away from organ-based drug selection and moving towards tumor characteristics for individualized treatment it is important to identify as many properties as possible that impact the efficacy of the rapalogues. A review of the current literature was conducted to identify enzymes involved in the metabolism of Sirolimus, Everolimus, Ridaforolimus, and Temsirolimus along with characteristics of tumors that predict the efficacy of these agents. This review also sought to establish whether the genetic characteristics of the patient might influence the activity of the rapalogues or lead to side effects from these agents. Current evidence suggests that tumors with mutations in the mTOR signal transduction pathway are sensitive to rapalogue treatment; the rapalogues are metabolized by cytochromes such as CYP3A4, CYP3A5, and CYP2C8 and transported by ABC transporters that are known to vary in activity in individuals; and that tumors can express these transporters and detoxifying enzymes. This results in three levels of genetic analysis that could impact the effectiveness of the mTOR inhibitors.

Precision sirolimus dosing in children: The potential for model-informed dosing and novel drug monitoring

The mTOR inhibitor sirolimus is prescribed to treat children with varying diseases, ranging from vascular anomalies to sporadic lymphangioleiomyomatosis to transplantation (solid organ or hematopoietic cell). Precision dosing of sirolimus using therapeutic drug monitoring (TDM) of sirolimus concentrations in whole blood drawn at the trough (before the next dose) time-point is the current standard of care. For sirolimus, trough concentrations are only modestly correlated with the area under the curve, with R 2 values ranging from 0.52 to 0.84. Thus, it should not be surprising, even with the use of sirolimus TDM, that patients treated with sirolimus have variable pharmacokinetics, toxicity, and effectiveness. Model-informed precision dosing (MIPD) will be beneficial and should be implemented. The data do not suggest dried blood spots point-of-care sampling of sirolimus concentrations for precision dosing of sirolimus. Future research on precision dosing of sirolimus should focus on pharmacogenomic and pharmacometabolomic tools to predict sirolimus pharmacokinetics and wearables for point-of-care quantitation and MIPD.

Pharmacokinetic principles of dose adjustment of mTOR inhibitors in solid organ transplanted patients

WHAT IS KNOWN AND OBJECTIVES

mTOR inhibitors possess narrow therapeutic range and substantial pharmacokinetic variability and the consequences from suboptimal dosing are serious. The aim of this review is to summarize the current knowledge about the factors influencing mTOR inhibitors pharmacokinetics and the possibility of using these relationships in order to improve its therapy individualization in solid organ transplanted patients.

METHODS

Literature search from Pubmed and Web of Science databases were performed using Boolean search operators in order to identify relevant studies.

RESULTS AND DISCUSSION

A total of 701 reports were identified from the initial literature search. Out of which 40 studies dealt with relationships between various factors and pharmacokinetics of mTOR inhibitors and with relevance of these associations for dosage optimization.

WHAT IS NEW AND CONCLUSION

The overview of the current covariates for pharmacokinetic variability of mTOR inhibitors has been provided on the level of absorption, distribution and elimination, and consequences of these relationships for dosing optimization has been summarized.

Critical Care Management Following Lung Transplantation

Postoperative critical care management for lung transplant recipients in the intensive care unit (ICU) has expanded in recent years due to its complexity and impact on clinical outcomes. The practical aspects of post-transplant critical care management, especially regarding ventilation and hemodynamic management during the early postoperative period in the ICU, are discussed in this brief review. Monitoring in the ICU provides information on the patient’s clinical status, diagnostic assessment of complications, and future management plans since lung transplantation involves unique pathophysiological conditions and risk factors for complications. After lung transplantation, the grafts should be appropriately ventilated with lung protective strategies to prevent ventilator-induced lung injury, as well as to promote graft function and maintain adequate gas exchange. Hypotension and varying degrees of pulmonary edema are common in the immediate postoperative lung transplantation setting. Ventricular dysfunction in lung transplant recipients should also be considered. Therefore, adequate volume and hemodynamic management with vasoactive agents based on their physiological effects and patient response are critical in the early postoperative lung transplantation period. Integrated management provided by a professional multidisciplinary team is essential for the critical care management of lung transplant recipients in the ICU.

Therapeutic Drug Monitoring of Mycophenolic Acid as a Precision Medicine Tool for Heart Transplant Patients: Results of an Observational Pharmacokinetic Pilot Study

In the clinical practice management of heart transplant (HTx), the impact of calcineurin inhibitors co-administration on pharmacokinetics (PKs) of mycophenolic acid (MPA), mycophenolate mofetil (MMF) active drug, is not adequately considered. This retrospective study investigated full MPA-PK profiles by therapeutic drug monitoring (TDM) in 21 HTx recipients treated with MMF combined with cyclosporine (CsA) or tacrolimus (TAC) at a median time of 2.6 months post-transplant. The two treatment groups were compared. We described the main MPA-PK parameters in patients developing acute cellular rejection (ACR) and those who did not. Median dose-adjusted MPA-trough levels and MPA-AUC_0-12h were higher in patients co-treated with TAC than with CsA (p = 0.0001 and p = 0.006, respectively). MPA-C_max and T_max were similar between the two groups, whereas the enterohepatic recirculation biomarker of MPA (MPA-AUC_4-12h) was higher in the MMF and TAC group (p = 0.004). Consistently, MPA clearance was higher in the MMF and CsA group (p = 0.006). In total, 87.5% of ACR patients were treated with MMF and CsA, presenting a lower MPA-AUC_0-12h (p = 0.02). This real-world study suggested the CsA interference on MPA-PK in HTx, evidencing the pivotal role of MPA TDM as a precision medicine tool in the early phase after HTx. A prospective study is mandatory to investigate this approach to HTx clinical outcomes.

Personalized Therapy for Mycophenolate: Consensus Report by the International Association of Therapeutic Drug Monitoring and Clinical Toxicology

ABSTRACT

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.

Clinical evaluation of pharmacists' interventions on multidisciplinary lung transplant outpatients' management: results of a 7-year observational study

OBJECTIVES

Lung transplant (LT) recipients require multidisciplinary care because of the complexity of therapeutic management. Pharmacists are able to detect drug-related problems and provide recommendations to physicians through pharmacists' interventions (PIs). We aimed at assessing the clinical impact of PIs on therapeutic management in LT outpatients.

DESIGN

Data were collected prospectively from an LT recipients cohort during 7 years. A multidisciplinary committee assessed retrospectively the clinical impact of accepted PIs.

SETTING

French University Hospital.

PARTICIPANTS

LT outpatients followed from 2009 to 2015.

PRIMARY OUTCOME MEASURES

Clinical impact of PIs performed by pharmacists using the CLEO tool and the Pareto chart.

RESULTS

1449 PIs led to a change in patient therapeutic management and were mainly related to wrong dosage (39.6%) and untreated indication (19.6%). The clinical impact of PIs was 'avoids fatality', 'major' and 'moderate', in 0.1%, 7.0% and 57.9%, respectively. Immunosuppressants, antimycotics for systemic use and antithrombotic agents had the greatest clinical impact according to the Pareto chart. PIs related to drug-drug interactions (10%) mainly had a moderate and major clinical impact (82.3%, p<0.0001).

CONCLUSION

Clinical pharmacists play a key role for detecting drug-related problems mostly leading to a change in therapeutic management among LT outpatients. Our study provides a new insight to analyse the clinical impact of PIs in order to target PIs which have most value and contribute to patient care through interdisciplinary approach.

The hurdles of nanotoxicity in transplant nanomedicine

Nanomedicine has matured significantly in the past 20 years and a number of nanoformulated therapies are cleared by regulatory agencies for use across the globe. Transplant medicine is one area that has significantly benefited from the advancement of nanomedicine in recent times. However, while nanoparticle-based therapies have improved toxicological profiles of some drugs, there are still a number of aspects regarding the biocompatibility and toxicity of nanotherapies that require further research. The goal of this article is to review toxicological profiles of immunosuppressant therapies and their conversion into nanomedicine formulations as well as introduce future challenges associated with current in vitro and in vivo toxicological models.

Low early posttransplant serum tacrolimus levels are associated with poor patient survival in lung transplant patients

BACKGROUND:

Low-dose tacrolimus-based immunosuppression is a standard therapy in kidney and liver transplantation; however, the optimal therapeutic level of tacrolimus has not been established in lung transplantation. We aimed to identify the tacrolimus level associated with better outcomes in lung transplant patients.

METHODS:

This retrospective study included patients who underwent lung transplantation at Seoul National University Hospital between 2006 and 2016. Kaplan–Meier survival analysis and Cox regression were performed according to tacrolimus levels at several time-points within 1-year posttransplantation.

RESULTS:

A total of 43 patients received bilateral lung transplantation. The median age was 53 years and the median follow-up was 20.5 months. Overall and 1-year patient survival rates were 55.8% and 74.4%, respectively. Infection was the most common cause of death (78.9%). Chronic lung allograft dysfunction was observed in 16.3%. A tacrolimus level <9 ng/ml at 1 month was associated with lower rejection-free survival (P = 0.009). A time-averaged tacrolimus level <10 ng/ml within 1 month posttransplantation was an independent risk factor for poor patient survival (hazard ratio: 4.904; 95% confidence interval: 1.930–12.459; P= 0.001). Furthermore, higher tacrolimus levels did not increase infectious complications.

CONCLUSIONS:

These finding suggest that tacrolimus levels ≥10 ng/ml within 1 month after lung transplantation appear to be associated with better patient survival.

Intracellular Delivery of Rapamycin From FKBP Elastin-Like Polypeptides Is Consistent With Macropinocytosis

Rapamycin (Rapa) is a highly potent drug; however, its clinical potential is limited by poor solubility, bioavailability, and cytotoxicity. To improve Rapa delivery, our team has fused the cognate protein receptor for Rapa, FKBP12, to high molecular weight elastin-like polypeptides (ELPs). One construct, FAF, includes an FKBP domain at each termini of an ELP. In a recent report, FAF/Rapa outperformed a family of related carriers with higher tumor accumulation and efficacy. Despite apparent efficacy, an explanation for how FAF carries Rapa into cells has not been elucidated. This manuscript explores the intracellular fate of FAF in MDA-MB-468, a triple negative (ER-/PR-/HER2-) breast cancer line. Based on a lack of displacement by excess unlabeled FAF, no evidence was found for the involvement of a receptor in cell-surface binding. Cellular association showed no dose-dependent saturation at concentrations up to 100 μM, which is consistent with uptake through fluid phase endocytosis. FAF does colocalize with dextran, a marker of fluid phase endocytosis. Upon internalization, both FAF and dextran target low pH intracellular compartments similarly. Despite likely exposure to lysosomal pH and proteolytic activity, intracellular FAF is eliminated from cells with a relatively long half-life of 17.7 and 19.0 h by confocal microscopy and SDS-PAGE respectively. A split luciferase reporter assay demonstrated that FAF delays the cytosolic access of Rapa in comparison to free drug by 30 min. A specific macropinocytosis inhibitor, amiloride, completely inhibits the cytosolic delivery of Rapa from FAF. Each of these results are consistent with macropinocytosis as the mechanism of cellular uptake necessary for the hand-off of Rapa from FKBP-based drug carriers like FAF to endogenous FKBP12 in the cytosol.

Genotypes associated with tacrolimus pharmacokinetics impact clinical outcomes in lung transplant recipients

Most lung transplantation immunosuppression regimens include tacrolimus. Single nucleotide polymorphisms (SNPs) in genes important to tacrolimus bioavailability and clearance (ABCB1, CYP3A4, and CYP3A5) are associated with differences in tacrolimus pharmacokinetics. We hypothesized that polymorphisms in these genes would impact immunosuppression-related outcomes. We categorized ABCB1, CYP3A4, and CYP3A5 SNPs for 321 lung allograft recipients. Genotype effects on time to therapeutic tacrolimus level, interactions with antifungal medications, concentration to dose (C₀ /D), acute kidney injury, and rejection were assessed using linear models adjusted for subject characteristics and repeat measures. Compared with CYP3A poor metabolizers (PM), time to therapeutic tacrolimus trough was increased by 5.1 ± 1.6 days for CYP3A extensive metabolizers (EM, P < 0.001). In the post-operative period, CYP3A intermediate metabolizers spent 1.2 ± 0.5 days less (P = 0.01) and EM spent 2.1 ± 0.5 days less (P < 0.001) in goal tacrolimus range than CYP3A PM. Azole antifungals interacted with CYP3A genotype in predicting C₀ /D (P < 0.001). Increased acute kidney injury rates were observed in subjects with high ABCB1 function (OR 3.0, 95% CI 1.1-8.6, P = 0.01). Lower rates of acute cellular rejection were observed in subjects with low ABCB1 function (OR 0.36, 95% CI 0.07-0.94, P = 0.02). Recipient genotyping may help inform tacrolimus dosing decisions and risk of adverse clinical outcomes.

Immunosuppression Drug Therapy in Lung Transplantation for Cystic Fibrosis

Cystic fibrosis (CF) is a common indication for lung transplantation (LTx) in children and adults with severe and irreversible lung disease. In the setting of LTx in the CF population, immunosuppressive medications are used to prevent allograft rejection despite the majority of these patients being chronically infected with numerous, and often antibiotic-resistant, pathogens. There is limited evidence for the optimal post-LTx immunosuppression regimen in patients with CF, particularly in children. This article provides a review of immunosuppression regimens in the pediatric and adult CF post-LTx population, investigating drug dosing and monitoring, and medication combinations. Currently used immunosuppressive medications and related systemic adverse effects are reviewed. With limitations of data in the pediatric population, future research should address immunosuppression in these children to help guide pediatric drug management as a means to optimize clinical outcomes after LTx.

Pharmacokinetics, Pharmacodynamics, and Pharmacogenomics of Immunosuppressants in Allogeneic Hematopoietic Cell Transplantation: Part II

Part I of this article included a pertinent review of allogeneic hematopoietic cell transplantation (alloHCT), the role of postgraft immunosuppression in alloHCT, and the pharmacokinetics, pharmacodynamics, and pharmacogenomics of the calcineurin inhibitors and methotrexate. In this article (Part II), we review the pharmacokinetics, pharmacodynamics, and pharmacogenomics of mycophenolic acid (MPA), sirolimus, and the antithymocyte globulins (ATG). We then discuss target concentration intervention (TCI) of these postgraft immunosuppressants in alloHCT patients, with a focus on current evidence for TCI and on how TCI may improve clinical management in these patients. Currently, TCI using trough concentrations is conducted for sirolimus in alloHCT patients. Several studies demonstrate that MPA plasma exposure is associated with clinical outcomes, with an increasing number of alloHCT patients needing TCI of MPA. Compared with MPA, there are fewer pharmacokinetic/dynamic studies of rabbit ATG and horse ATG in alloHCT patients. Future pharmacokinetic/dynamic research of postgraft immunosuppressants should include '-omics'-based tools: pharmacogenomics may be used to gain an improved understanding of the covariates influencing pharmacokinetics as well as proteomics and metabolomics as novel methods to elucidate pharmacodynamic responses.

Pharmacokinetics, Pharmacodynamics and Pharmacogenomics of Immunosuppressants in Allogeneic Haematopoietic Cell Transplantation: Part I

Although immunosuppressive treatments and target concentration intervention (TCI) have significantly contributed to the success of allogeneic haematopoietic cell transplantation (alloHCT), there is currently no consensus on the best immunosuppressive strategies. Compared with solid organ transplantation, alloHCT is unique because of the potential for bidirectional reactions (i.e. host-versus-graft and graft-versus-host). Postgraft immunosuppression typically includes a calcineurin inhibitor (cyclosporine or tacrolimus) and a short course of methotrexate after high-dose myeloablative conditioning, or a calcineurin inhibitor and mycophenolate mofetil after reduced-intensity conditioning. There are evolving roles for the antithymyocyte globulins (ATGs) and sirolimus as postgraft immunosuppression. A review of the pharmacokinetics and TCI of the main postgraft immunosuppressants is presented in this two-part review. All immunosuppressants are characterized by large intra- and interindividual pharmacokinetic variability and by narrow therapeutic indices. It is essential to understand immunosuppressants' pharmacokinetic properties and how to use them for individualized treatment incorporating TCI to improve outcomes. TCI, which is mandatory for the calcineurin inhibitors and sirolimus, has become an integral part of postgraft immunosuppression. TCI is usually based on trough concentration monitoring, but other approaches include measurement of the area under the concentration-time curve (AUC) over the dosing interval or limited sampling schedules with maximum a posteriori Bayesian personalization approaches. Interpretation of pharmacodynamic results is hindered by the prevalence of studies enrolling only a small number of patients, variability in the allogeneic graft source and variability in postgraft immunosuppression. Given the curative potential of alloHCT, the pharmacodynamics of these immunosuppressants deserves to be explored in depth. Development of sophisticated systems pharmacology models and improved TCI tools are needed to accurately evaluate patients' exposure to drugs in general and to immunosuppressants in particular. Sequential studies, first without and then with TCI, should be conducted to validate the clinical benefit of TCI in homogenous populations; randomized trials are not feasible, because there are higher-priority research questions in alloHCT. In Part I of this article, we review the alloHCT process to facilitate optimal design of pharmacokinetic and pharmacodynamics studies. We also review the pharmacokinetics and TCI of calcineurin inhibitors and methotrexate.

[Small airway diseases and immune deficiency]

INTRODUCTION

Innate or acquired immune deficiency may show respiratory manifestations, often characterized by small airway involvement. The purpose of this article is to provide an overview of small airway disease across the major causes of immune deficiency.

BACKGROUND

In patients with common variable immune deficiency, recurrent lower airway infections may lead to bronchiolitis and bronchiectasis. Follicular and/or granulomatous bronchiolitis of unknown origin may also occur. Bronchiolitis obliterans is the leading cause of death after the first year in patients with lung transplantation. Bronchiolitis obliterans also occurs in patients with allogeneic haematopoietic stem cell transplantation, especially in the context of systemic graft-versus-host disease.

VIEWPOINT AND CONCLUSION

Small airway diseases have different clinical expression and pathophysiology across various causes of immune deficiency. A better understanding of small airways disease pathogenesis in these settings may lead to the development of novel targeted therapies.

Mycophenolic mofetil optimized pharmacokinetic modelling, and exposure-effect associations in adult heart transplant recipients

Mycophenolic acid (MPA) area under the curve (AUC) has been associated with graft outcome.

THE AIMS OF OUR STUDY WERE

(1) to develop pharmacokinetic tools to optimize MPA inter-dose AUC estimation in heart transplant patients; and (2) to investigate the relationships between acute allograft rejection and MPA AUC, trough level (C0) or mycophenolate mofetil (MMF) dose. Two independent modeling approaches (parametric and non parametric) were used to fit 56 rich MPA pharmacokinetic (PK) profiles collected from 40 adult heart transplant recipients enrolled in the PIGREC study, receiving MMF and a calcineurin inhibitor (CNI), in the first year post-transplantation. In addition, associations between drug exposure (MPA C0, AUC and MMF dose) and acute rejection or MMF adverse events were investigated using time-dependent Cox models with stratification on the type of calcineurin inhibitor. Exposure threshold values were investigated using ROC curve analysis. The 2 models developed fit adequately the data and the use of their combination yielded 100% consistency with the measured AUC in terms of strategy of dose adjustment (maintain, increase or decrease). MPA measured AUC adjusted on CNI exposure was significantly associated with rejection (per unit increase: HR [95% CI]=0.97 [0.95-0.99], p=0.0122), while no effect was shown for adverse events attributable to MMF. An AUC threshold of 50 mg×h/L was proposed (sensitivity=77%, specificity=25%) beyond which the risk of rejection was significantly increased (low vs. high: HR=3.48 [1.21-10.0], p=0.0204). The tools developed have already been made available to the heart transplant community on our ISBA website (https://pharmaco.chu-limoges.fr).

Oral intake of curcumin markedly activated CYP 3A4: in vivo and ex-vivo studies

Curcumin, a specific secondary metabolite of Curcuma species, has potentials for a variety of beneficial health effects. It is nowadays used as a dietary supplement. Everolimus (EVL) is an immunosuppressant indicated for allograft rejection and cancer therapy, but with narrow therapeutic window. EVL is a substrate of P-glycoprotein (P-gp) and cytochrome P450 3A4 (CYP3A4). This study investigated the effect of coadministration of curcumin on the pharmacokinetics of EVL in rats and the underlying mechanisms. EVL (0.5 mg/kg) was orally administered without and with 50 and 100 mg/kg of curcumin, respectively, in rats. Blood samples were collected at specific time points and EVL concentrations in blood were determined by QMS® immunoassay. The underlying mechanisms were evaluated using cell model and recombinant CYP 3A4 isozyme. The results indicated that 50 and 100 mg/kg of curcumin significantly decreased the AUC_0-540 of EVL by 70.6% and 71.5%, respectively, and both dosages reduced the C_max of EVL by 76.7%. Mechanism studies revealed that CYP3A4 was markedly activated by curcumin metabolites, which apparently overrode the inhibition effects of curcumin on P-gp. In conclusion, oral intake of curcumin significantly decreased the bioavailability of EVL, a probe substrate of P-gp/CYP 3A4, mainly through marked activation on CYP 3A4.

Population pharmacokinetics of everolimus in cardiac recipients: comedications, ABCB1, and CYP3A5 polymorphisms

BACKGROUND

The aim of this study was, using routine drug monitoring data, to identify patient characteristics that may influence everolimus (EVE) pharmacokinetic parameters and to develop a population pharmacokinetic model to predict EVE whole blood concentrations in cardiac recipients.

METHODS

Fifty-nine patients were enrolled in the prospective study. Patient's characteristics were recorded including biological covariates and treatments. CYP3A5 and ABCB1 polymorphisms were determined. Seven hundred seventy-five EVE blood samples were collected for routine drug monitoring. Population pharmacokinetic modeling was carried out using the nonlinear mixed-effects modeling program. Results were analyzed according to a 1-compartment pharmacokinetic model with linear absorption and elimination. The model was evaluated using a bootstrap method and a visual predictive check procedure.

RESULTS

The pharmacokinetic of EVE in cardiac recipients was best described by a 1-compartment model. Interindividual variability was best described by an exponential error model and residual error by a proportional plus additive error model. Estimation of EVE apparent clearance (3.33 ± 0.20 L/h) and apparent volume of distribution (146 ± 33 L) were in accordance with previously published data. Bilirubinemia and cyclosporine significantly influenced EVE clearance. Some covariates that were expected to influence EVE clearance, for example, ABCB1 and CYP3A5 polymorphisms, were not evidenced. No covariates influenced the volume of distribution of EVE.

CONCLUSIONS

This study is the first population pharmacokinetic model of EVE in heart transplantation patients. It allows a better description of the pharmacokinetics of EVE. The present population pharmacokinetic model allows estimating a priori and a posteriori EVE concentrations in cardiac recipients and could limit the over and under drug exposure in this population.

Pilot study of a pharmaceutical care intervention in an outpatient lung transplant clinic

BACKGROUND

Lung transplant recipients have complex drug regimens. Study objectives were to assess drug therapy problems (DTPs), pharmacist recommendations, and patient satisfaction with pharmacist services.

METHODS

Using a pharmaceutical care assessment process, pharmacists identified DTPs and made therapeutic recommendations. Number of DTPs identified per pharmacist visit was calculated and compared to standard care visits through retrospective chart review. Potential clinical impact of recommendations was evaluated by blinded clinicians. Patient satisfaction was assessed via survey.

RESULTS

Fifty-five DTPs were identified in 43 patients over 50 pharmacist visits (1.05 ± 1.34 DTPs per visit). In these same patients, rate of DTP identification was 0.51 ± 0.64 DTPs per standard visit in the preceding two-wk period (p = 0.018 vs. pharmacist visit). The most common DTPs identified by the pharmacist were adverse drug effect (27%) and untreated indication (25%). Overall, 62% of pharmacist recommendations were rated very significant or significant. Survey return rate was 58% and satisfaction scores ranged from 3 to 5 out of 5. Review of medications and teaching regarding the use of medications received the most "very satisfied" and "highly important" scores.

CONCLUSIONS

Pharmacists can make valuable contributions in a lung transplant clinic setting by identifying DTPs and making recommendations with a positive impact on patient outcomes and satisfaction.

ATP-binding cassette transporters as pharmacogenetic biomarkers for kidney transplantation

Immunosuppressive drugs used in organ transplantation are highly effective in preventing acute rejection. However, the clinical use of these drugs is complicated by the fact that they display highly variable pharmacokinetics and pharmacodynamics between individual patients. The influence of genetic variation on the interindividual variability in immunosuppressive drug disposition, efficacy, and toxicity has been explored in recent years. The polymorphically-expressed ATP-binding cassette (ABC) transporter proteins, in particular ABCB1 and ABCC2, have been investigated extensively because they play an important role in the absorption, distribution and elimination of many immunosuppressive drugs in use today. From these studies it can be concluded that polymorphisms in ABCB1 and ABCC2 have no consistent effect on immunosuppressant pharmacokinetics and toxicity although polymorphisms in ABCB1 appear to be related to the risk of developing calcineurin inhibitor-related nephrotoxicity. However, the latter needs to be replicated before an individual's ABCB1 genotype can become a useful marker that is applied in clinical practice. Future studies evaluating the influence of ABC transporter gene polymorphisms should explore the relationship with intracellular rather than systemic drug concentrations further in well-designed clinical studies. Until then, single-nucleotide polymorphisms in ABC transporter genes are not suitable to act as biomarkers for solid organ transplantation.

Sensitive quantification of sirolimus and everolimus by LC-MS/MS with online sample cleanup

Sirolimus and its derivative everolimus are widely used today as immunosuppressive agents for example in the transplantation medicine. The problematic pharmacokinetic behavior of those substances makes therapeutic drug monitoring mandatory. Therefore, a fast, simple and sensitive high-throughput procedure using online extraction with turbulent flow chromatography for the concurrent measurement of sirolimus and everolimus has been developed. 200 microl of whole blood was mixed with internal standard (23-desmethoxyrapamycin) and the precipitation solution and centrifuged. An aliquot of the supernatant was transferred into autosampler vials. 50 microl of the supernatant was injected into the LC system, where the analytes were extracted using turbulent flow chromatography and thereafter analyzed using reversed phase chromatography. Detection was done by atmospherical pressure chemical ionization (APCI) mass spectrometry in the negative ionization mode. The method has been fully validated and compared to a previously used method. The method was shown to be linear over the entire calibration range (2.2-43.7 microg/l for everolimus and 2.9-51.2 microg/l for sirolimus). The lower limit of quantification was 0.5 microg/l for both compounds. For within-day and between-day analysis, the CV's were <7.6% for everolimus and <8.7% for sirolimus, respectively. The accuracy was between 92.1% and 105% for everolimus and 96.1% and 106% for sirolimus. Recovery ranged between 46.3% and 50.6% for everolimus and 51.2% and 57.2% for sirolimus. The method was demonstrated to be free of matrix effects and comparable to the previously used method. The presented LC-MS/MS method, using turbulent flow chromatography online extraction, allows a fast, simple and reliable determination of everolimus and sirolimus.

[Medical complications of lung transplantation]

In 2010, lung transplantation is a valuable therapeutic option for a number of patients suffering from of end-stage non-neoplastic pulmonary diseases. The patients frequently regain a very good quality of life, however, long-term survival is often hampered by the development of complications such as the bronchiolitis obliterans syndrome, metabolic and infectious complications. As the bronchiolitis obliterans syndrome is the first cause of death in the medium and long term, an intense immunosuppressive treatment is maintained for life in order to prevent or stabilize this complication. The immunosuppression on the other hand induces a number of potentially severe complications including metabolic complications, infections and malignancies. The most frequent metabolic complications are arterial hypertension, chronic renal insufficiency, diabetes, hyperlipidemia and osteoporosis. Bacterial, viral and fungal infections are the second cause of mortality. They are to be considered as medical emergencies and require urgent assessment and targeted therapy after microbiologic specimens have been obtained. They should not, under any circumstances, be treated empirically and it has also to be kept in mind that the lung transplant recipient may present several concomitant infections. The most frequent malignancies are skin cancers, the post-transplant lymphoproliferative disorders, Kaposi's sarcoma and some types of bronchogenic carcinomas, head/neck and digestive cancers. Lung transplantation is no longer an exceptional procedure; thus, the pulmonologist will be confronted with such patients and should be able to recognize the symptoms and signs of the principal non-surgical complications. The goal of this review is to give a general overview of the most frequently encountered complications. Their assessment and treatment, though, will most often require the input of other specialists and a multidisciplinary and transversal approach.