Régis Bouquié

UGT1A1 genotype and irinotecan therapy: general review and implementation in routine practice

Irinotecan is a major drug in the treatment of advanced colorectal cancer. Its active form is the SN38 metabolite, which is cleared by the biliary route after glucuronidation by uridine diphosphate–glucuronosyltransferase 1A1 (UGT1A1). UGT1A1 activity exhibits a wide intersubject variability, in part related to UGT1A1 gene polymorphisms. The present review on the impact of the deficient UGT1A1*28 variant on irinotecan efficacy and toxicity was produced by a French joint workgroup comprising the Group of Clinical Onco‐pharmacology (GPCO‐Unicancer) and the National Pharmacogenetics Network (RNPGx). It clearly emerges that for irinotecan doses at least equal to 180 mg/m2, patients homozygous for the UGT1A1*28 allele are at increased risk of developing hematological and/or digestive toxicities. Irinotecan dose reduction is thus recommended in homozygous *28/*28 patients. In addition, this personalized medicine strategy aims to secure high‐dose irinotecan administration (≥240 mg/m2) that have proven to be safe in homozygous *1/*1 patients only. The clinical relevance of this test is discussed in terms of treatment efficacy improvement, as increasing the irinotecan dose appears to be safe in patients not bearing a deficient allele. Best execution practices, cost‐effectiveness, and result interpretation are discussed with the aim of facilitating the implementation of this analysis in clinical practice. The existence of networks of laboratories performing this test in routine hospital treatment, as in France, offers the prospect of widespread screening, thus guaranteeing equal access to safe treatment and optimized therapy for patients receiving irinotecan‐based therapy in advanced colorectal cancer.

Colchicine-induced rhabdomyolysis in a heart/lung transplant patient with concurrent use of cyclosporin, pravastatin, and azithromycin.

We report a case of colchicine-induced rhabdomyolysis in a heart/lung-transplanted man treated with cyclosporin. A treatment was to resolve an acute gouty arthritis and was started with 3 mg of colchicine the first day, then 2 mg the second and the third day, and finally 1 mg/d during 6 days. Eight days later, the patient developed multiple organ failure and rhabdomyolysis. The concentration of colchicine analyzed was greater than the standard 153 hours after his last intake. Pharmacokinetic interactions are responsible of this toxicity. Cyclosporin, pravastatin, and azithromycin are known to inhibit P-glycoprotein, which will enhance the intracellular colchicine level by acting in its bioavailability and moderating hepatic and renal excretion. Moreover, long-term treatment by cyclosporin generates chronic renal failure that will, in the same time, decrease colchicine elimination. Even short-term administration of therapeutic colchicine dose may cause colchicine-related toxicity, especially in the setting of a renal failure and/or polymedicinal treatment.

Switching from tenofovir/emtricitabine and nevirapine to a tenofovir/emtricitabine/rilpivirine single-tablet regimen in virologically suppressed, HIV-1-infected subjects

OBJECTIVES Nevirapine is an inducer of hepatic metabolism. After discontinuation, nevirapine has an inductive effect on cytochrome P450 3A4, which persists for a few weeks and which, after switching to rilpivirine, may reduce rilpivirine exposures and have a negative clinical impact. This study evaluates the virological outcome, pharmacokinetics and safety of switching virologically suppressed, HIV-1-infected patients from nevirapine to rilpivirine. PATIENTS AND METHODS This 24 week open-label single-centre study included HIV-1-infected adults with HIV-1 RNA <50 copies/mL for >6 months on tenofovir/emtricitabine and nevirapine, who were willing to simplify their regimen to tenofovir/emtricitabine/rilpivirine. Virological suppression, safety and nevirapine and rilpivirine pharmacokinetics were assessed. RESULTS At weeks 12 and 24, all 32 subjects remained virologically suppressed. One subject discontinued at week 1 for rilpivirine-associated insomnia and two patients chose to resume tenofovir/emtricitabine and nevirapine after week 12 because of rilpivirine-associated food constraint. There was no grade 3/4 laboratory abnormality. Rilpivirine trough concentrations were above the mean trough concentrations observed in Phase 3 studies by 1 week post-switch. Twenty-seven out of 32 patients had no measurable levels of nevirapine by 2 weeks post-switch. The meal accompanying tenofovir/emtricitabine/rilpivirine intake satisfied food requirements in 81% of cases. Overall general satisfaction was improved in 90% of the subjects despite food constraints. CONCLUSION Nevirapine has a short and limited inductive effect on rilpivirine metabolism, which is not clinically significant. Tenofovir/emtricitabine/rilpivirine is an efficacious and safe option for virologically suppressed HIV-infected patients on nevirapine wishing to simplify their regimen.

A fast LC-MS/MS assay for methotrexate monitoring in plasma: validation, comparison to FPIA and application in the setting of carboxypeptidase therapy

High-dose methotrexate remains a mainstay in the treatment of acute lymphoblastic leukaemia, osteosarcoma and non-Hodgkin lymphoma. Therapeutic drug monitoring of plasma MTX is important to monitor efficacy and adverse events. The authors aimed at developing a liquid chromatography tandem mass spectrometry (LC-MS/MS) method with online extraction to determine MTX and 7-OH-MTX in plasma for therapeutic drug monitoring. The analysis combined straightforward sample preparation, consisting of protein precipitation with methanol/ZnSO4, with a 4-minute run time consisting of an on-line enrichment by a flush/back-flush cycle (Poros column, R1/20, 2.1 mm × 30 mm) before the second dimension chromatography (Phenomenex Luna 5 μm Phenyl Hexyl, 2 mm × 50 mm column). Samples were analysed using an HPLC Agilent 1200 Series and ABSciex API 3200. The electrospray was operated in positive ionization mode monitoring the following mass transitions: m/z 455.11 → 308.3 for MTX, 471.14 → 324.3 for 7-OH-MTX and m/z 459.1 → 312.3 for internal standard (MTX13C2H3). The method was linear up to 50 μmol L−1, and intra-day and inter-day quality control CVs were below 8.3% for MTX and 11.71% for 7-OH-MTX. Average recovery was 24% for MTX and 57% for 7-OH-MTX. The lower limit of quantitation was 25 nmol L−1 for the 2 analytes. For MTX and 7-OH-MTX the standard line slope CV percentage was <3% and the slope difference <6%, indicating that our analytical method is almost free from a significant relative matrix effect. Method comparison with the Abbott TDx fluorescent polarization immunoassay (FPIA) showed excellent agreement: LC-MS/MS = 0.0011 + 1.0334 (FPIA). Because of antibody cross-reactivity between DAMPA and MTX, none of the immunoassays can be used after carboxypeptidase administration. The goal of our work was to develop a specific LC-MS/MS method to monitor both MTX and 7-OH-MTX plasma concentrations within the clinically relevant range. Its expected that the LC-MS/MS method for MTX monitoring after carboxypeptidase administration will be very rarely used since it concerns only exceptional cases. Therefore, the geographically balanced distribution of University Hospital able to ensure follow-up of these patients, within 24 hours of collection, can draw a reliable solution for the security of the patients. We develop a fast and reliable LC-MS/MS method for both routine TDM of MTX as in the setting of carboxypeptidase therapy.

A liquid chromatography–tandem mass spectrometry assay for quantification of rilpivirine and dolutegravir in human plasma

A liquid chromatography-tandem mass spectrometry assay requiring a 100μL aliquot of human plasma for simultaneous determination of rilpivirine, a second generation non-nucleoside reverse transcriptase inhibitors of HIV and dolutegravir, a novel integrase stand transfer inhibitors of HIV concentrations has been developed. Sample pre-treatment is limited to protein precipitation with a mixture of methanol and zinc sulfate. After centrifugation the supernatant is injected in the chromatographic system, which consists of on-line solid phase extraction followed by separation on a phenyl-hexyl column. This 2.5min method, with its simple sample preparation provides sensitive (the limit of quantitation is 25ng/mL for each compound), accurate and precise (the intra-day and inter-day imprecision and inaccuracy are lower than 15%) quantification of the plasma concentration of these drugs and can be used for therapeutic drug monitoring in patients infected with HIV.

Simultaneous determination of ceftaroline, daptomycin, linezolid and rifampicin concentrations in human plasma by on-line solid phase extraction coupled to high-performance liquid chromatography–tandem mass spectrometry

Methicillin-resistant Staphylococcus aureus infection is a serious clinical problem worldwide. Ceftaroline, daptomycin, linezolid in combination with rifampicin are particularly used in this indication. To allow monitoring of these antibiotics, an on-line solid phase extraction coupled to high-performance liquid chromatography-tandem mass spectrometry assay requiring a 100 μL aliquot of human plasma has been developed. Besides, significance of 25-O-desacetylrifampicin concentrations was evaluated. Sample pre-treatment is limited to protein precipitation with methanol. After centrifugation 10 μL of supernatant are injected into the chromatographic system, which consists of an on-line solid phase extraction followed by a separation on a phenyl-hexyl column and detected by a tandem mass spectrometer. Plasma drug concentrations were determined by multiple reaction monitoring in positive ion mode, and assay performance was evaluated. 25-O-Desacetylrifampicin activity, was compared to rifampicin using a microbiological method. Sample preparation using methanol precipitation followed by solid-phase extraction yielded good recovery and ionization efficiency, with chromatographic separation achieved within 3 min per sample. Within-run and between-run precisions ranged respectively from 1.22% to 9.35% and from 1.61% to 9.36%. Lower limits of quantification were 0.04 mg/L for linezolid, 0.1mg/L for rifampicin, 0.2mg/L for ceftaroline and 0.5mg/L for daptomycin. It appears that 25-O-desacetylrifampicin displays a substantial intrinsic bactericidal activity against S. aureus. This assay provides simple, rapid, sensitive and accurate quantification of the four antibiotic drugs and one metabolite and can be routinely used to monitor drug concentration in methicillin-resistant S. aureus infected patients.

Crushed and Injected Buprenorphine Tablets: Characteristics of Princeps and Generic Solutions

Self-injection of high-dose buprenorphine is responsible for well-described complications. In 2011, we have been alerted by unusual but serious cutaneous complication among injection buprenorphine users. A prospective data collection identified 30 cases of necrotic cutaneous lesions after injection of filtered buprenorphine solution, among which 25 cases occurred following injection of buprenorphine generics. The main goal of our study was to put forward particularities that could explain the cutaneous complications, by qualitatively and quantitatively confronting particles present in Subutex and generics solutions. We used the same protocol that injected-buprenorphine users: generic or subutex tablets were crushed in sterile water and filtered through 2 filters commonly used (cotton-pad and sterifilt). Solutions were analyzed by laser granulometry, flow cytometry and scanning electron microscopy. We have highlighted the wide variation of the quantity and the size of the particles present in solution between the two drugs after cotton-pad filtration. The proportion of particles <10 µm is systematically higher in the generic solutions than with Subutex. All of the insoluble particles found in generic solutions contain silica, whereas non- organic element was to be identified in the insoluble particles of Subutex. One skin biopsy obtained from one patient who developed a necrotic lesion after intravenous injection of filtrated solution of buprenorphine generic, shows non-organic elements. Identification of particles in situ enables us to confirm the presence of silica in the biopsy. Actually the monitoring of patient receiving generic of buprenorphine must be strengthened.

Intérêt du génotypage de l’UGT1A1 dans le cadre du traitement des cancers digestifs par irinotécan*

Irinotecan is a cytotoxic agent administered by IV infusion in the treatment of advanced colorectal cancer. Its anticancer activity results from its bioactivation into SN-38 metabolite, which is cleared through glucuronidation by the hepatic enzyme uridine diphosphate-glucuronosyltransferase 1A1 (UGT1A1). In the general population, there is wide inter-subject variability in UGT1A1 enzyme activity related to UGT1A1 gene polymorphisms. The French joint workgroup coming from the National Pharmacogenetic Network (RNPGx) and the Group of Clinical Oncologic Pharmacology (GPCO) herein presents an updated review dealing with efficacy and toxicity clinical studies related to UGT1A1 genetic variants. From a critical analysis of this review it clearly emerges that, for doses higher than 180 mg/m(2), hematologic and digestive irinotecan-induced toxicities could be prevented in daily clinical practice by generalizing the use of a simple pharmacogenetic test before starting treatment. The clinical relevance of this test is also discussed in terms of treatment efficacy improvement, with the possibility of increasing the irinotecan dose in patients not bearing the deleterious allele. This test involves using a blood sample to analyze the promoter region of the UGT1A1 gene (UGT1A1*28 allele). Best execution practices, laboratory costs, as well as results interpretation are described with the aim of facilitating the implementation of this analysis in clinical routine. The existence of a French laboratories network performing this test in clinical routine makes it possible to generalize UGT1A1 deficiency screening, so as to guarantee equal access to safe treatment and optimized irinorecan-based therapy for the many patients receiving irinotecan-based therapy in advanced colorectal cancer.

Chiral on-line solid phase extraction coupled to liquid chromatography-tandem mass spectrometry assay for quantification of (R) and (S) enantiomers of methadone and its main metabolite in plasma

The authors aimed at developing a liquid chromatography tandem mass spectrometry (LC-MS/MS) method with online extraction to determine (R)- and (S)- methadone enantiomers and its main metabolite 2-ethylidine-1,5-dimethyl-3,3 diphenylpyrrolidine (EDDP) in plasma. The analysis combined straightforward sample preparation, consisting of protein precipitation with acetonitrile, and an online enrichment by a flush/back-flush cycle before the second dimension chromatography. Using D3-deuterated internal standards allows overcoming significant relative matrix effect. Our method was linear up to 2000 ng/mL. This simple sample preparation provides sensitive (the limit of quantitation is 25 ng/mL for (R,S)-methadone and EDDP and 12.5 ng/mL for (R)- and (S)- methadone), accurate and precise (the intra-day and inter-day imprecision and inaccuracy are lower than 15%) quantification of the plasma concentration of these drugs. We have developed a reliable LC-MS/MS method for both routine therapeutic drug monitoring and pharmacokinetics studies and for toxicology analysis in the setting of methadone treatment or intoxication.

Influence of nevirapine administration on the pharmacokinetics of dolutegravir in patients infected with HIV-1

OBJECTIVES The metabolic pathways of dolutegravir and nevirapine suggest a potential pharmacokinetic interaction between these drugs. The objective of this study was to investigate the influence of nevirapine administration on the pharmacokinetics of dolutegravir in patients infected with HIV-1. PATIENTS AND METHODS This study was an investigator-initiated trial registered at ClinicalTrials.gov under identifier NCT02067767. Dolutegravir (50 mg once daily) was added to the antiretroviral regimen (400 mg of nevirapine once daily + 600/300 mg of abacavir/lamivudine once daily) in 10 adult patients for 5 days. After discontinuation of nevirapine, the combination of dolutegravir + abacavir/lamivudine was continued. Full pharmacokinetic profiles were assessed on the day of nevirapine discontinuation and 2 weeks after discontinuation of nevirapine. The pharmacokinetic parameters of dolutegravir were calculated by non-compartmental analysis. The log-transformed values of these parameters were compared between periods with and without nevirapine co-administration. RESULTS The co-administration of nevirapine led to a significant decrease (P < 0.05) in the area under the plasma concentration-time curve for dolutegravir from the time the dose was administered until the end of the dosing interval (-19%, P = 0.011), as well as decreases in trough plasma concentration (-34%, P = 0.018) and terminal half-life (-15%, P = 0.039), and a significant increase (P < 0.05) in apparent oral clearance for dolutegravir (+23%, P = 0.011). CONCLUSIONS The decrease in dolutegravir exposure in combination with nevirapine suggests that the metabolism of dolutegravir is induced by nevirapine. According to therapeutic drug monitoring for dolutegravir, some patients may need a higher dose than 50 mg of dolutegravir once daily to maintain the therapeutic plasma concentration throughout the dosing interval.