Caroline Barau

Practical management of boceprevir and immunosuppressive therapy in liver transplant recipients with hepatitis C virus recurrence.

ABSTRACT Hepatitis C virus (HCV) recurrence is the most important complication in HCV liver transplant patients. Boceprevir with pegylated interferon and ribavirin (PegIFN/RBV) enabled improvement in sustained virological response rates of patients with genotype 1 HCV. Boceprevir interacts with immunosuppressive therapy (IT) by inhibiting the cytochrome P450 3A enzyme. Our aim was to study interactions and assess the safety of boceprevir in the context of HCV recurrence. Boceprevir (800 mg three times a day) initiated after a 4-week lead-in phase was associated with cyclosporine (three patients), tacrolimus (two patients), and everolimus (one patient) in five liver transplant patients with genotype 1 HCV infection who experienced HCV recurrence. The mean follow-up period after HCV therapy was 14.8 ± 3.1 weeks. Estimated oral clearances of IT decreased on average by 50%, requiring reduced dosing regimens. Anemia occurred in all patients, with a mean fall in hemoglobin levels between baseline and week 12 of 3.12 ± 2.27 g/dl. All patients required administration of β-erythropoietin (n = 5), three needed ribavirin dose reduction, and one needed a blood transfusion. A virological response was observed in all patients (mean HCV viral load [HVL] decrease at week 12, 6.64 ± 0.35 log10 IU/ml). These preliminary results in liver transplant patients with HCV recurrence demonstrate the feasibility and safety of coadministration of boceprevir and IT.

Evaluation of the Architect® tacrolimus assay in kidney, liver, and heart transplant recipients

The narrow therapeutic range of tacrolimus requires therapeutic drug monitoring to prevent transplant rejection and to minimize nephrotoxicity. The aim of this study was to evaluate the analytical performance of the tacrolimus chemiluminescent microparticle immunoassay (CMIA) in everyday practice comparatively with other methods. CMIA imprecision and accuracy were tested using low, medium, and high concentrations in control samples. The limits of quantification (LOQ) of CMIA and antibody-conjugated magnetic immunoassay (ACMIA) were evaluated using negative whole-blood samples containing 0.4-5.7 ng/ml of tacrolimus from a stock solution. CMIA was compared with ACMIA, enzyme multiplied immunoassay (EMIT), and liquid chromatography-tandem mass spectrometry (LC-MS/MS), using 176 samples from recipients (135 men and 41 women) of heart (n=19), kidney (n=107), or liver (n=50) transplants. CMIA total precision was 5.7%, 3.7% and 3.6% with the low-, medium-, and high-concentration controls, respectively; corresponding values for accuracy were 98%, 104%, and 104%. LOQ was 0.5 (95%CI, 0.22-1.38) with CMIA and 2.5 ng/ml with ACMIA. Linear regression results were as follows: CMIA=1.2LC-MS/MS+0.14 (r=0.98); CMIA=0.93EMIT+0.36 (r=0.975); CMIA=1.15ACMIA-0.25 (r=0.988); and, for tacrolimus concentrations in the 1-15 ng/ml range, of special interest as many transplant recipients are given low-dose tacrolimus, CMIA=1.05LC-MS/MS+0.38 (r=0.94). Two patients had falsely elevated tacrolimus concentrations due to interference in the ACMIA assay; one was a renal transplant recipient who stopped her treatment and had tacrolimus concentrations of 12.5 ng/ml by ACMIA and <0.5 ng/ml by CMIA; the other was an HIV-positive renal transplant recipient whose tacrolimus concentrations by ACMIA were 1.8-43.7-fold those by CMIA. Such interferences with ACMIA, which may be related to endogenous antibodies in the plasma, are likely to negatively impact patient care. In conclusion, the tacrolimus CMIA assay is suitable for routine laboratory use and does not suffer from the interferences seen with ACMIA in some patients.

High Concentration of Raltegravir in Semen of HIV-Infected Men: Results from a Substudy of the EASIER-ANRS 138 Trial

ABSTRACT Raltegravir concentrations and human immunodeficiency virus type 1 (HIV-1) RNA levels in semen samples from 10 treatment-experienced HIV-1-infected patients were measured after 24 weeks of raltegravir-based highly active antiretroviral therapy (HAART). Semen and plasma HIV-1 RNA levels were below 100 copies/ml and 50 copies/ml, respectively, in all samples. The median raltegravir concentrations in semen samples (n = 10) and in plasma samples (n = 9) drawn simultaneously were 345 (range, 83 to 707) ng/ml and 206 (range, 106 to 986) ng/ml, respectively. The median semen-to-plasma ratio of raltegravir concentration was 1.42 (range, 0.52 to 6.66), indicating good although variable levels of drug penetration of raltegravir in the seminal compartment.

Falsely Elevated Whole Blood Tacrolimus Concentrations due to Interference in an Affinity Column-mediated Immunoassay Method on Xpand Dimension

The whole blood concentration of tacrolimus is required for therapeutic drug monitoring of this immunosuppressive drug. Abnormal tacrolimus levels affect its efficacy or toxicity, leading to changes in its dosage. Here, we report analytical interference in the affinity column-mediated immunoassay tacrolimus method on the Xpand autoanalyzer in a kidney transplant human immunodeficiency virus-infected patient. Tacrolimus concentrations obtained by affinity column-mediated immunoassay are 3- to 7-fold higher than measurements with the enzyme multiplied immunoassay technique assay. The cause of this interference remains unknown. However, it would be necessary to identify this type of interference to measure tacrolimus concentration with another method to avoid analytical error, which may lead to a poor clinical outcome.

Population pharmacokinetics of mycophenolic acid and dose optimization with limited sampling strategy in liver transplant children

AIMS The aims were to estimate the mycophenolic acid (MPA) population pharmacokinetic parameters in paediatric liver transplant recipients, to identify the factors affecting MPA pharmacokinetics and to develop a limited sampling strategy to estimate individual MPA AUC(0,12 h). METHODS Twenty-eight children, 1.1 to 18.0 years old, received oral mycophenolate mofetil (MMF) therapy combined with either tacrolimus (n= 23) or ciclosporin (n= 5). The population parameters were estimated from a model-building set of 16 intensive pharmacokinetic datasets obtained from 16 children. The data were analyzed by nonlinear mixed effect modelling, using a one compartment model with first order absorption and first order elimination and random effects on the absorption rate (k(a)), the apparent volume of distribution (V/F) and apparent clearance (CL/F). RESULTS Two covariates, time since transplantation (≤ and >6 months) and age affected MPA pharmacokinetics. k(a), estimated at 1.7 h(-1) at age 8.7 years, exhibited large interindividual variability (308%). V/F, estimated at 64.7 l, increased about 2.3 times in children during the immediate post transplantation period. This increase was due to the increase in the unbound MPA fraction caused by the low albumin concentration. CL/F was estimated at 12.7 l h(-1). To estimate individual AUC(0,12 h), the pharmacokinetic parameters obtained with the final model, including covariates, were coded in Adapt II(®) software, using the Bayesian approach. The AUC(0,12 h) estimated from concentrations measured 0, 1 and 4 h after administration of MMF did not differ from reference values. CONCLUSIONS This study allowed the estimation of the population pharmacokinetic MPA parameters. A simple sampling procedure is suggested to help to optimize pediatric patient care.

Optimization of the dosing regimen of mycophenolate mofetil in pediatric liver transplant recipients.

Mycophenolate mofetil (MMF) is now commonly used in pediatric liver transplant recipients, but no clear recommendations about the dosing regimen have been made for this population. The aim of this study was to determine the MMF dosage required for pediatric liver transplant recipients to achieve an area under the plasma concentration–time curve from 0 to 12 hours (AUC0‐12) for mycophenolic acid (MPA) greater than 30 mg hour/L. A pharmacokinetic study of 15 children (median age = 8.3 years, range = 1.1‐15.2 years) was performed at a median of 11.0 months (range = 0.5‐88.0 months) after liver transplantation. MMF was initially introduced at a median starting dose of 300 mg/m2 twice a day (range = 186‐554 mg/m2 twice a day). Thirteen of the 15 patients had an MPA AUC0‐12 value less than 30 mg hour/L. The MMF dosage had to be increased in all patients except 1. The MMF dosage required to reach an MPA AUC0‐12 value greater than the defined target of 30 mg hour/L ranged from 371 to 1014 mg/m2/day. For 2 patients who received rifampin in addition to MMF, the MPA AUC0‐12 value remained low despite a 2‐fold increase in the MMF dosage. In conclusion, an initial MMF dose of 600 mg/m2 twice a day led to MPA AUC0‐12 values greater than the 30 mg hour/L threshold except when rifampin was coadministered. Because of the important interindividual variability of MPA pharmacokinetics, therapeutic drug monitoring is recommended for optimizing the daily MMF dosage. Furthermore, these results suggest that the coadministration of MPA with rifampin should be avoided. Liver Transpl 17:1152–1158, 2011.

Effect of coadministered HIV-protease inhibitors on tacrolimus and sirolimus blood concentrations in a kidney transplant recipients

A patient with human immunodeficiency virus infection and end‐stage renal disease received a renal transplant. At the time of surgery, the patient was on quadruple antiretroviral therapy (lamivudine, zidovudine, and amprenavir/ritonavir). Immunosuppression was initiated with basiliximab, corticosteroid, mycophenolate mofetil, and a single 0.5 mg dose of tacrolimus. In the following days, an increase in tacrolimus concentration was observed with a peak of 37 ng/mL. Tacrolimus half‐life was 6.5 days and tacrolimus maintenance dose was 0.5 mg every 4 days. Eleven months later, the patient had developed Kaposi sarcoma. Tacrolimus was replaced by sirolimus (first dose 1 mg), and the patient was stabilized with 1.5 mg of sirolimus once a week. Increased tacrolimus half‐life and increased dose interval of sirolimus and tacrolimus were due to CYP3A4/5 and/or P‐glycoprotein inhibition by protease inhibitors. Close monitoring is required in the management of tacrolimus and sirolimus dosing regimens when combined with ritonavir boosted HIV‐1 protease inhibitors.

Characterization of Binding of Raltegravir to Plasma Proteins

ABSTRACT The objective of this study was to characterize raltegravir (RAL) binding to albumin and alpha-1-acid glycoprotein (AAG). Unbound and bound RAL were separated by ultrafiltration. The association constant (Ka) was estimated by a graphical method. In HIV-infected patients, the average plasma protein binding is 76%. RAL did not bind to AAG but bound to nonsaturable, low-affinity albumin sites with an n (number of sites) · Ka product of 9.8 × 102 liters/mol. A pH increase of 0.2 U led to a 2% increase in the bound fraction.

Comparison of 3 Estimation Methods of Mycophenolic Acid AUC based on a Limited Sampling Strategy in Renal Transplant Patients

A significant relationship between mycophenolic acid (MPA) area under the plasma concentration-time curve (AUC) and the risk for rejection has been reported. Based on 3 concentration measurements, 3 approaches have been proposed for the estimation of MPA AUC, involving either a multilinear regression approach model (MLRA) or a Bayesian estimation using either gamma absorption or zero-order absorption population models. The aim of the study was to compare the 3 approaches for the estimation of MPA AUC in 150 renal transplant patients treated with mycophenolate mofetil and tacrolimus. The population parameters were determined in 77 patients (learning study). The AUC estimation methods were compared in the learning population and in 73 patients from another center (validation study). In the latter study, the reference AUCs were estimated by the trapezoidal rule on 8 measurements. MPA concentrations were measured by liquid chromatography. The gamma absorption model gave the best fit. In the learning study, the AUCs estimated by both Bayesian methods were very similar, whereas the multilinear approach was highly correlated but yielded estimates about 20% lower than Bayesian methods. This resulted in dosing recommendations differing by 250 mg/12 h or more in 27% of cases. In the validation study, AUC estimates based on the Bayesian method with gamma absorption model and multilinear regression approach model were, respectively, 12% higher and 7% lower than the reference values. To conclude, the bicompartmental model with gamma absorption rate gave the best fit. The 3 AUC estimation methods are highly correlated but not concordant. For a given patient, the same estimation method should always be used.

Regular treadmill exercise inhibits mitochondrial accumulation of cholesterol and oxysterols during myocardial ischemia-reperfusion in wild-type and ob/ob mice

Mitochondria play a central role in the irreversible damages induced to the heart by a prolonged period of ischemia followed by reperfusion. We previously demonstrated that (1) myocardial ischemia-reperfusion induces mitochondrial accumulation of cholesterol and oxysterols that are deleterious for the organelle; (2) inhibition of cholesterol and oxysterol accumulation prevents mitochondrial injury at reperfusion; (3) exercise is cardioprotective and remains efficient in the presence of co-morbidities such as obesity. The aim of this study was to investigate whether regular exercise limits mitochondrial cholesterol and oxysterol accumulation in wild-type and obese mice. Wild-type C57BL/6J and obese (ob/ob) mice were assigned to sedentary conditions or regular treadmill exercise and submitted to 30min of coronary artery occlusion followed by 15min of reperfusion. Regular exercise improved oxidative phosphorylation, restored the antioxidant capacity of the heart by increasing the expression of SOD1 and catalase and reduced the mitochondrial generation of oxysterols in wild-type as well as in ob/ob mice. In wild-type animals, exercise limited the production of oxysterols. In ob/ob mice, despite hypercholesterolemia, chronic exercise abolished the mitochondrial accumulation of cholesterol and concomitantly reduced the generation of 7α-hydroxycholesterol, 7-ketocholesterol and cholesterol-5α,6α-epoxide. In conclusion, regular exercise prevents the mitochondrial accumulation of cholesterol and oxysterols which occurs during early reperfusion of an ischemic myocardium in mice. This effect is observed in normo and hypercholesterolemic animals. It may be partly responsible for the antioxidant properties of regular exercise and contribute to its cardioprotective effect in obese conditions.