Valérie Furlan

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.

SLCO1B1 genetic polymorphism influences mycophenolic acid tolerance in renal transplant recipients

AIMS This study aimed to determine the influence of gene candidates on mycophenolic acid (MPA) response during the first year of renal transplantation. MATERIALS & METHODS A total of 218 renal transplant recipients who received MPA from the first day of transplantation at a fixed dose of 2 g/day were genotyped for ABCB1, ABCC2, UGT2B7, UGT1A9, SLCO1B1, SLCO1B3 and IMPDH1 polymorphisms. Clinical end points were MPA-related adverse drug reactions (ADRs) and acute rejection episodes during the first year post-transplantation. RESULTS After correction for multiple statistical testing, SLCO1B1 (encoding the hepatic uptake transporter OATP1B1) was the only gene associated with MPA-related ADRs, showing a 75% risk reduction in favor of a protective effect of the SLCO1B1*5 allele (p = 0.002). In vitro experiments showed that MPA metabolites MPA-phenyl-glucuronide and MPA-acyl-glucuronide are substrates of OATP1B1. Their transport was decreased in the presence of the variant transporter (OATP1B1*5). CONCLUSION These results suggest for the first time that carriers of the SLCO1B1*5 allele seem to be protected from MPA-related ADRs.

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.

Pharmacokinetics of Rifampin and Isoniazid in Tuberculosis-HIV-Coinfected Patients Receiving Nevirapine- or Efavirenz-Based Antiretroviral Treatment

ABSTRACT This is a substudy of the Agence Nationale de Recherches sur le Sida et les Hépatites Virales (ANRS) Comparison of Nevirapine and Efavirenz for the Treatment of HIV-TB Co-infected Patients (ANRS 12146-CARINEMO) trial, which assessed the pharmacokinetics of rifampin or isoniazid with or without the coadministration of nonnucleoside reverse transcriptase inhibitor-based HIV antiretroviral therapy in HIV-tuberculosis-coinfected patients in Mozambique. Thirty-eight patients on antituberculosis therapy based on rifampin and isoniazid participated in the substudy (57.9% males; median age, 33 years; median weight, 51.9 kg; median CD4+ T cell count, 104 cells/μl; median HIV-1 RNA load, 5.5 log copies/ml). The daily doses of rifampin and isoniazid were 10 and 5 mg/kg of body weight, respectively. Twenty-one patients received 200 mg of nevirapine twice a day (b.i.d.), and 17 patients received 600 mg of efavirenz once a day (q.d.) in combination with lamivudine and stavudine from day 1 until the end of the study. Blood samples were collected at regular time-dosing intervals after morning administration of a fixed-dose combination of rifampin and isoniazid. When rifampin was administered alone, the median maximum concentration of drug in serum (Cmax) and the area under the concentration-time curve (AUC) at steady state were 6.59 mg/liter (range, 2.70 to 14.07 mg/liter) and 27.69 mg · h/liter (range, 11.41 to 109.75 mg · h/liter), respectively. Concentrations remained unchanged when rifampin was coadministered with nevirapine or efavirenz. When isoniazid was administered alone, the median isoniazid Cmax and AUC at steady state were 5.08 mg/liter (range, 1.26 to 11.51 mg/liter) and 20.92 mg · h/liter (range, 7.73 to 56.95 mg · h/liter), respectively. Concentrations remained unchanged when isoniazid was coadministered with nevirapine; however, a 29% decrease in the isoniazid AUC was observed when isoniazid was combined with efavirenz. The pharmacokinetic parameters of rifampin and isoniazid when coadministered with nevirapine or efavirenz were not altered to a clinically significant extent in these severely immunosuppressed HIV-infected patients. Patients experienced favorable clinical outcomes. (This study has been registered at ClinicalTrials.gov under registration no. NCT00495326.)

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.

Quantification of raltegravir (MK0518) in human plasma by high-performance liquid chromatography with photodiode array detection

A precise and accurate high-performance liquid chromatography (HPLC) method with photodiode array detection has been developed and validated for raltegravir, a human immunodeficiency virus integrase strand transfer inhibitor (HIV-1 INSTI). Plasma (300 microL) was extracted with dichloromethane/hexane 50:50 (v/v) after addition of the internal standard, 6,7-dimethyl-2,3-di(2-pyridyl) quinoxaline. The compounds were separated using a dC18 column and detected with ultraviolet detection at 320 nm. The limit of quantification was 10 ng/mL for raltegravir. The method was linear and validated over a concentration range of 0-10,000 ng/mL. The intra-day precision ranged from 3.1 to 12.3%, while the intra-day accuracy ranged from -15.0 to -0.5%, the inter-day precision and accuracy were less than 7%. The mean recovery was 76.8%. Application to clinical samples taken from patients treated with raltegravir indicated that the method is suitable for measuring plasma concentrations of raltegravir in pharmacokinetic studies of clinical trials.

Tacrolimus dose requirement in pediatric liver transplantation: influence of CYP3A5 gene polymorphism

AIM Little information is available regarding the influence of CYP3A5 genetic polymorphisms on tacrolimus dose requirement in pediatric liver transplantation. PATIENTS & METHODS We performed a retrospective study among 179 pediatric liver recipients grafted between 2002 and 2009 in order to determine the influence of donor CYP3A5 genotype along with clinical variables on tacrolimus daily dose requirement during the first weeks following transplantation. RESULTS Mean stable tacrolimus daily dose requirement was higher among children who received a liver expressing CYP3A5 (carrying the CYPA3A5*1 allele) compared with those with a liver that did not express CYP3A5 (CYP3A5*3/*3 genotype): 0.29 ± 0.20 vs 0.18 ± 0.13 mg.kg(-1).d(-1), p = 0.005, respectively. A younger recipient age and fluconazole prescription were also significantly associated with tacrolimus daily dose requirement. Time to reach stable tacrolimus therapeutic trough concentrations was prolonged among patients with a CYP3A5-expressing graft (26 vs 21 days, p = 0.04). CONCLUSION Donor CYP3A5 genotype partially explains tacrolimus dose requirement. Original submitted 30 January 2013; Revision submitted 2 May 2013.