Mercè Brunet

Opportunities to optimize tacrolimus therapy in solid organ transplantation: report of the European consensus conference.

In 2007, a consortium of European experts on tacrolimus (TAC) met to discuss the most recent advances in the drug/dose optimization of TAC taking into account specific clinical situations and the analytical methods currently available and drew some recommendations and guidelines to help clinicians with the practical use of the drug. Pharmacokinetic, pharmacodynamic, and more recently pharmacogenetic approaches aid physicians to individualize long-term therapies as TAC demonstrates a high degree of both between- and within-individual variability, which may result in an increased risk of therapeutic failure if all patients are administered a uniform dose. TAC has undoubtedly benefited from therapeutic drug monitoring, but interpretation of the blood concentration is confounded by the relative differences between the assays. Single time points, limited sampling strategies, and area under concentration-time curve have all been considered to determine the most appropriate sampling procedure that correlates with efficacy. Therapeutic trough TAC concentration ranges have changed since the initial introduction of the drug, while still maintaining adequate immunosuppression and avoiding drug-related adverse effects. Pharmacodynamic markers have also been considered advantageous to the clinician, which may better reflect efficacy and safety, taking into account the between-individual variability rather than whole blood concentrations. The choice of method, differences between methods, and potential pitfalls of the method should all be considered when determining TAC concentrations. The recommendations of this consensus meeting regarding the analytical methods include the following: encourage the development and promote the use of analytical methods displaying a lower limit of quantification (1 ng/mL), perform careful validation when implementing a new analytical assay, participate in external proficiency testing programs, promote the use of certified material as calibrators in high-performance liquid chromatography with mass spectrometric detection methods, and take account of the assay and intermethod bias when comparing clinical trial outcomes. It is also important to consider that TAC concentrations may also be influenced by other factors such as specific pharmacokinetic characteristics associated with the population, drug interactions, pharmacogenetics, adverse events that may alter TAC concentrations, and any change in the oral formulation that may result in pharmacokinetic changes. This meeting emphasized the importance of obtaining multicenter prospective trials to assess the efficacy of alternative strategies to TAC trough concentrations whether it is other single time points or area under the concentration-time curve Bayesian estimation using limited sampling strategies and to select, standardize, and validate routine biomarkers of TAC pharmacodynamics.

The pharmacokinetics of mycophenolate mofetil in renal transplant recipients receiving standard-dose or low-dose cyclosporine, low-dose tacrolimus or low-dose sirolimus: the Symphony pharmacokinetic substudy

BACKGROUND Exposure to mycophenolic acid (MPA), the primary active metabolite of mycophenolate mofetil (MMF), is correlated with therapeutic efficacy of MMF but varies depending on the concomitantly administered immunosuppressive drugs. METHODS A 3-month pharmacokinetic substudy of the prospective, randomized, multicentre, open-label Symphony study was performed. Eighty-three adult renal transplant patients received standard-dose cyclosporine, MMF 2 g/day and corticosteroids, or daclizumab induction, MMF 2 g/day and corticosteroids plus low-dose cyclosporine, low-dose tacrolimus or low-dose sirolimus. The area under the concentration-time curve (AUC(0-12)) of MPA and its metabolites between treatment groups was compared. Pharmacokinetic sampling was performed before MMF administration and at 20, 40, 75 min; 2, 3, 6, 8, 10 and 12 h post-dose on Day 7 and Months 1 and 3. RESULTS Compared with standard-dose cyclosporine, patients receiving low-dose tacrolimus or low-dose sirolimus had significantly higher AUC(0-12) values for MPA at Day 7 and Month 1 and for free MPA at Day 7, and significantly lower AUC(0-12) values for 7-O-MPA-glucuronide (MPAG) at Month 1 and for acyl-glucuronide at Months 1 and 3 (P < 0.05). AUC(0-12) of MPA and free MPA was significantly greater with low-dose tacrolimus and low-dose sirolimus than with low-dose cyclosporine in the first month (P < 0.05). The ratio of MPA to MPAG exposure was significantly higher in the three low-dose groups than in the standard-dose cyclosporine group (P < 0.05). CONCLUSIONS Standard- and low-dose cyclosporine reduces the exposure of MPA and free MPA compared to low-dose tacrolimus or low-dose sirolimus in patients given the same dose of MMF.

Effect of mycophenolate mofetil on immune response and plasma and lymphatic tissue viral load during and after interruption of highly active antiretroviral therapy for patients with chronic HIV infection a randomized pilot study

Summary: The main goal of this study was to assess the role of mycophenolate mofetil (MMF) during interruption of highly active antiretroviral therapy (HAART). Seventeen patients with early-stage chronic HIV type 1 infection were treated with HAART for 12 months. They were then randomized (day 0) to receive MMF (HAART–MMF group, n = 9) or to continue the regimen (HAART group, n = 6) for 120 additional days. At day 120 in the HAART–MMF group, HAART was discontinued, and MMF administration was continued. The primary end point of the study was the number of individuals maintaining a plasma viral load (VL) set point of <200 copies/mL after at least 6 months off HAART. At day 120, all patients in both groups had undetectable plasma VLs. After 6 months off HAART, 5 of 9 patients in the HAART–MMF group versus 1 of 6 patients in the HAART group maintained a plasma VL of <200 copies/mL (P = 0.28). According to the ability of their plasma to inhibit cellular proliferation, patients were reclassified and divided into an inhibition group (n = 6) and a no inhibition group (n = 9). The doubling time of VL rebound was significantly higher in the inhibition group (mean ± SE, 10.22 ± 1.3) than in the no inhibition group (mean ± SE, 4.6 ± 1.6; P = 0.03). Moreover, 5 of 6 patients in the inhibition group maintained a plasma VL of <200 copies/mL versus 1 of 9 patients in the no inhibition group (P = 0.005) after 6 months off HAART. We found that combining MMF and HAART delayed VL rebound and improved control of viral replication without HAART but only when inhibition of lymphocyte proliferation was achieved.

Sequential determination of pharmacokinetics and pharmacodynamics of mycophenolic acid in liver transplant patients treated with mycophenolate mofetil.

Background. In liver transplantation, mycophenolate mofetil (MMF) is habitually administered using fixed doses. We assessed whether mycophenolic acid (MPA) monitoring could be advisable in liver transplant patients. Methods. In 15 liver transplant patients receiving tacrolimus, daclizumab and MMF (1 g bid, orally), we determined the 12-hour plasma MPA pharmacokinetic profile after one dose of MMF at days 6, 10, and 16, and months 3 and 6. The inhibitory capacity of serum MPA on proliferation of CEM cells, a cell line insensitive to other immunosuppressants, was also determined. Results. A large interindividual variability in MPA profiles was observed at any time. Regardless of a gradual increase in individual MPA AUC and C0 over time following transplantation, a substantial proportion of patients had these parameters below the ranges recommended in other organ transplantations throughout the study. When MPA AUC and C0 were within the recommended ranges, CEM proliferation was inhibited by almost all serum samples, but when these pharmacokinetic parameters were below the recommended ranges, CEM proliferation was very variable and, therefore, unpredictable. No relationship between MPA pharmacokinetics and the efficacy of MMF could be established (only one patient developed rejection), probably due to the concomitant administration of tacrolimus and daclizumab. Gastrointestinal symptoms were the only adverse events with a significant relationship with MPA levels. Conclusions. During the first postoperative months, exposure to MPA is low in a considerable proportion of liver transplant patients receiving MMF at a fixed dose of 1 g bid. MPA monitoring appears necessary in these patients.

Mycophenolate, clinical pharmacokinetics, formulations, and methods for assessing drug exposure

UNLABELLED This article summarizes part of a consensus meeting about mycophenolate (MPA) therapeutic drug monitoring held in Rome under the auspices of The Transplantation Society in November 2008 (Clin J Am Soc Nephrol. 2010;5:341-358). This part of the meeting focused on the clinical pharmacokinetics of MPA and included discussion on how to measure MPA (active drug) exposure and the differences between the currently available formulations. SUMMARY POINTS Because of variability in the dose-concentration relationship, MPA exposure should be measured and doses should be adjusted accordingly to achieve optimal clinical outcomes. Suggested therapeutic exposures derived for MPA from mycophenolate mofetil (MMF) may differ to those that could be useful for MPA from enteric-coated mycophenolate sodium (EC-MPS), particularly if limited sampling strategies or single concentration, especially trough concentrations, is used, as the concentration-time profiles of MPA from the 2 formulations are quite different. The 2 MPA formulations cannot be considered as bioequivalent. The area under the concentration-time curve (AUC 0-12) is considered the criterion standard for monitoring of MPA, which is a reflection of exposure to the drug over the entire dosing period. If a limited sampling protocol coupled with multilinear regression or Bayesian estimation is used to estimate this parameter, it should be used only for the population in which the model has been developed and should preferably include at least one time point after 4 hours (preferably around 8 or 9 hours after MMF dosing). If a single time point is to be used as a surrogate for an AUC 0-12, trough concentration of MPA may be the most practical but, from a pharmacokinetic standpoint, is not the most informative time point to choose. Because limited sampling strategies to estimate MPA exposure from EC-MPS have not yet been well developed and fully evaluated, nor have accurate Bayesian estimators been reported, AUC 0-12 measurement is still necessary to obtain reliable estimates of MPA exposure in patients treated with EC-MPS. The measurement of MPA trough concentrations should not be used at all for MPA exposure assessment following administration of EC-MPS. Because limited sampling strategies to estimate MPA exposure from EC-MPS have not yet been well developed and fully evaluated, nor have accurate Bayesian estimators been reported, AUC 0-12 measurement is still necessary to obtain reliable estimates of MPA exposure in patients treated with EC-MPS. The measurement of MPA trough concentrations should not be used at all for MPA exposure assessment following administration of EC-MPS. Lower (or higher) than expected total MPA exposure in patients with severe renal impairment may still indicate sufficient free MPA exposure. Mycophenolate free exposure measurement/estimation is likely to be beneficial in patients with severe renal impairment (creatinine clearance b25 mL/min) to guide dosage estimation, especially because renal function changes over time after transplant, while recognizing that robust prospective studies to show the clinical advantage of measuring free MPA exposure are still required. Lower total measured MPA exposure in patients with hypoalbuminemia may still indicate sufficient free MPA exposure. Mycophenolate free concentration measurement and estimation of exposure are likely to be beneficial in patients with a serum albumin less than or equal to 31 g/L to guide interpretation of MPA exposure. A 1.5-g twice-daily starting dose of MMF rather than a 1-g twice-daily starting dose of MMF is more likely to achieve the minimum target MPA exposure in adult transplant recipients receiving concomitant cyclosporine therapy. Because the cyclosporine dose is progressively tapered following transplantation, MPA exposure should be measured repeatedly and MMF should be doses adjusted accordingly to achieve optimal clinical outcome. Mycophenolate exposure should be measured in the first week after transplant, then each week for the first month, each month until month 3, and subsequently every 3 months up to 1 year with appropriate dosage adjustment, as AUC is likely to increase over time. After 1 year, if dosage requirement has stabilized, MPA exposure can be assessed each time the immunosuppressive regimen is changed or a potentially interacting drug is introduced or withdrawn. Assessment of UGT1A9 single nucleotide polymorphisms (-275TNA, -2152CNT, -440CNT, -331TNC) should be considered before transplantation to assist in dosing decisions to achieve optimal MPA exposure immediately after transplant. Consideration of the points summarized above should lead to more effective dosage adjustment based on sound applied pharmacokinetic and pharmacodynamic principles.

Mammalian Target of Rapamycin Inhibition Halts the Progression of Proteinuria in a Rat Model of Reduced Renal Mass

Many kidney transplant patients experience an increase in proteinuria when converted from a calcineurin inhibitor-based regimen to one based on a mammalian target of rapamycin (mTOR) inhibitor, and preexisting proteinuria and poor renal function have been identified as risk factors for this increase. Our aim was to evaluate the effect of sirolimus, an mTOR inhibitor, on renal function and histology in a proteinuric model of reduced renal mass. Sirolimus-treated animals had approximately half as much proteinuria as vehicle-treated animals (P < 0.05), and had less glomerulosclerosis, tubular atrophy, interstitial fibrosis, and inflammation. Immunohistochemistry showed that sirolimus attenuated the increased expression of renal vascular endothelial growth factor (VEGF), as well as the expression of VEGF receptors 1 and 2. In conclusion, sirolimus halted the progression of proteinuria and structural damage in a rat model of reduced renal mass, possibly through a reduction in renal VEGF activity.

Cadmium and zinc relationships in the liver and kidney of humans exposed to environmental cadmium

Concentrations of cadmium and zinc were determined in the liver and in the kidney (cortex and medulla) of subjects from the general population of Barcelona (Spain) by atomic absorption spectrometry. Tissues were collected from necropsies of 50 selected subjects without any occupational exposure to heavy metals. Cadmium levels calculated on a fresh tissue basis were 14.6 +/- 5.9 micrograms/g (2.4-31) in the kidney cortex, 8.6 +/- 4.3 micrograms/g (1.5-16.7) in the kidney medulla and 0.98 +/- 0.50 micrograms/g (0.32-2.32) in the liver. Zinc concentrations ranged between 18-53 micrograms/g, (mean +/- S.D.: 38.0 +/- 10 micrograms/g) in the kidney cortex, 25.0 +/- 7.7 micrograms/g (12-42 micrograms/g) in the kidney medulla and 41.7 +/- 18.3 micrograms/g (20-84 micrograms/g) in the liver. The aim of the present work was to study the association of cadmium and zinc in the kidney and in the liver of a human population with cadmium accumulation from an environmental origin. The results obtained showed a significant correlation between cadmium and zinc concentration in the liver (r = 0.86, P < 0.001), but not in the kidney.

Intracellular IFN-γ and IL-2 expression monitoring as surrogate markers of the risk of acute rejection and personal drug response in de novo liver transplant recipients

Biomarker monitoring is needed in transplantation to reflect individual response to immunosuppressive drugs and graft outcome. We evaluated intracellular expression and soluble production of interferon-(IFN)-γ and interleukin-(IL)-2 as predictive biomarkers of acute rejection (AR) and personal drug response. Pharmacokinetic-pharmacodynamic profiles were determined in 47 de novo liver recipients treated with tacrolimus, mycophenolate mofetil and prednisone. Of the 47 patients, AR occurred in nine. There were no differences in drug concentrations between rejectors and non-rejectors. A pre-transplantation cut-off value of 55.80% for %CD8(+)-IFN-γ(+) identified patients at high risk of AR with a sensitivity of 75% and a specificity of 82%. In the first week post-transplantation, patients with a % inhibition for soluble IFN-γ, %CD8(+)-IFN-γ(+) and %CD8(+)-IL2(+) lower than 40% developed AR, showing low susceptibility to immunosuppressive drugs. Therefore, effector-T-cell response monitoring may help physicians to identify personal response to treatment and patients at high risk of AR.

Therapeutic Drug Monitoring of Everolimus: A Consensus Report

Abstract: In 2014, the Immunosuppressive Drugs Scientific Committee of the International Association of Therapeutic Drug Monitoring and Clinical Toxicology called a meeting of international experts to provide recommendations to guide therapeutic drug monitoring (TDM) of everolimus (EVR) and its optimal use in clinical practice. EVR is a potent inhibitor of the mammalian target of rapamycin, approved for the prevention of organ transplant rejection and for the treatment of various types of cancer and tuberous sclerosis complex. EVR fulfills the prerequisites for TDM, having a narrow therapeutic range, high interindividual pharmacokinetic variability, and established drug exposure–response relationships. EVR trough concentrations (C0) demonstrate a good relationship with overall exposure, providing a simple and reliable index for TDM. Whole-blood samples should be used for measurement of EVR C0, and sampling times should be standardized to occur within 1 hour before the next dose, which should be taken at the same time everyday and preferably without food. In transplantation settings, EVR should be generally targeted to a C0 of 3–8 ng/mL when used in combination with other immunosuppressive drugs (calcineurin inhibitors and glucocorticoids); in calcineurin inhibitor-free regimens, the EVR target C0 range should be 6–10 ng/mL. Further studies are required to determine the clinical utility of TDM in nontransplantation settings. The choice of analytical method and differences between methods should be carefully considered when determining EVR concentrations, and when comparing and interpreting clinical trial outcomes. At present, a fully validated liquid chromatography tandem mass spectrometry assay is the preferred method for determination of EVR C0, with a lower limit of quantification close to 1 ng/mL. Use of certified commercially available whole-blood calibrators to avoid calibration bias and participation in external proficiency-testing programs to allow continuous cross-validation and proof of analytical quality are highly recommended. Development of alternative assays to facilitate on-site measurement of EVR C0 is encouraged.

Biomarkers of immunoregulatory status in stable liver transplant recipients undergoing weaning of immunosuppressive therapy

Biomarkers that reflect immune response recovery and predict clinical events during withdrawal or minimization of immunosuppressive therapy have not been evaluated. This study aimed to evaluate whether immune response recovers after withdrawal of long-term immunosuppressive treatment in stable liver transplant patients and to determine whether specific biomarkers reflect immune response reactivity and predict rejection. Pharmacokinetic-pharmacodynamic profiles were determined in 24 patients and 80 healthy donors before immunosuppressive treatment reduction began, at 50%, and at complete withdrawal. In patients who rejected, effector-T-cell response mediated by soluble IFN-γ, %CD4(+)IFN-γ and %CD8(+)IL-2/IFN-γ were significantly increased, while TGF-β1 production and the TGF-β1/IFN-γ ratio were significantly decreased. In patients with rejection, soluble IFN-γ and %CD8(+)IL-2 were significantly higher before immunosuppressive treatment was reduced. Further studies are required, but this battery of biomarkers performed in whole blood could be a useful tool to monitor immunosuppressive treatment minimization or withdrawal protocols and identify patients at increased risk of rejection.