Sylvie Quaranta

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.

Ethnic differences in the distribution of CYP3A5 gene polymorphisms

The genetic polymorphism affecting the CYP3A5 enzyme is responsible for interindividual and interethnic variability in the metabolism of CYP3A5 substrates. The full extent of the CYP3A5 genetic polymorphism was analysed in French Caucasian, Gabonese and Tunisian populations using a polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) strategy. In the three populations, eight, 17 and ten single nucleotide polymorphisms (SNPs), respectively, were identified, among which nine correspond to rare new mutations. Also identified were 16 alleles including eight new allelic variants. Significant differences were observed in the distribution of these alleles. Particularly, the frequency of the CYP3A5*3C null allele in French Caucasians (81.3%) and in Tunisians (80.0%) is higher than in the Gabonese population (12.5%) (p < 0.001). Considering the CYP3A5 genotypes of the tested individuals, only 10.4% of French Caucasians and 30.0% of Tunisians were identified as CYP3A5 expressors. In contrast, 90.0% of Gabonese subjects appear to express the CYP3A5 protein.

Validation of an Electrospray Ionization LC-MS/MS Method for Quantitative Analysis of Raltegravir, Etravirine, and 9 Other Antiretroviral Agents in Human Plasma Samples

Background: Raltegravir is the first human immunodeficiency virus-1 (HIV-1) integrase inhibitor used in treatment-experienced patients who have evidence of viral replication and HIV-1 strains resistance to multiple antiretroviral regimens. Etravirine is a novel NNRTI, active against HIV-1 strains harboring multiple NNRTI mutations. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the quantification of raltegravir, etravirine, and 9 other antiretroviral agents (amprenavir, atazanavir, darunavir, efavirenz, indinavir, lopinavir, ritonavir, saquinavir, and tipranavir) in plasma at the concentrations associated with therapy. Materials and Methods: The ritonavir analog, methyl indinavir, and lopinavir-d8 were used as internal standards, added to 100 μL of plasma sample prior to a protein precipitation using methanol. Chromatographic separation was achieved on a C18 HPLC column (Waters Sunfire 100 × 2.1 mm, 3.5 μm) with a mobile phase gradient at a flow rate of 0.3 mL/min. Five μL of sample were injected into the LC-MS/MS system (Waters Quattro Premier XE) to determine concentrations of raltegravir, etravirine, and other antiretroviral agents. Results and Discussion: This method showed an excellent linearity for all calibration curves (r2 > 0.998). The lower limit of quantification was established at 5 ng/mL for raltegravir and 40 ng/mL for etravirine, with precision and accuracy within ±20% and 80% to 120% for all analytes. Intraassay and interassay precision and inaccuracy ranged from −9.2% to 6.9% for raltegravir and from −14.3% to 12.3% for etravirine and were less than 15% for all other compounds. No matrix effect was observed for any of the antiretrovirals studied. Conclusion: A rapid, specific, and sensitive LC-MS/MS method for quantification of raltegravir, etravirine, and 9 other antiretrovirals in human plasma was developed and was successfully applied for routine therapeutic drug monitoring.

Population pharmacokinetics and pharmacogenetics of vincristine in paediatric patients treated for solid tumour diseases

PurposeThe interindividual variability of vincristine pharmacokinetics is quite large, but the origins of this variability are not properly understood. The aim of this study was to develop a population pharmacokinetic model of vincristine in a paediatric population treated for solid tumour disease and evaluate the impact of different ABCB1, CYP3A4 and CYP3A5 polymorphisms on the different pharmacokinetic parameters.MethodsWe assessed vincristine pharmacokinetics in 26 children treated for various solid tumour diseases. Genotypes were determined by real-time PCR with a LightCycler™ and ABCB1 haplotypes calculated using the software program Phase 2.1. Vincristine plasma concentrations were determined by LC–MS/MS, and a population approach was performed on 184 samples by the NONMEM computer program. Demographic, therapeutic and genotypic covariables were evaluated on vincristine pharmacokinetic parameters.ResultsThe frequency of CYP3A4*1A/*1A and *1A/*1B genotypes were 87.5 and 12.5%, respectively. CYP3A5*1/*3 and *3/*3 were observed in 20.8 and 79.2% of the patients, respectively. The three major haplotypes were (allelic frequencies) CGC (50%), CGT (14.6%) and TTT (23.2%). Vincristine pharmacokinetics was well described by a two-compartment model. Large interindividual and interoccasion variability were observed. The different polymorphisms studied did not improve the model prediction.ConclusionsCYP3A4, CYP3A5 and ABCB1 polymorphisms did not significantly affect in vivo vincristine pharmacokinetics. Our results demonstrate that vincristine pharmacokinetic variability cannot be explained by these genetic polymorphisms.

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.

Effect of fluid loading during hypovolaemic shock on caspofungin pharmacokinetic parameters in pig

IntroductionCaspofungin treatment is frequently initiated in shock patients. In the present study, we investigated the influence of hypovolaemic shock requiring fluid loading on the plasma and pulmonary pharmacokinetic parameters of caspofungin in the pig.MethodsAfter being anaesthetised and mechanically ventilated, 12 pigs were bled to induce a two-hour deep shock and resuscitated using normal saline based on haemodynamic goals. A one-hour infusion of 70 mg of caspofungin was started at the beginning of the resuscitation period. The lungs were removed four hours after caspofungin administration. Sixteen animals served as controls without haemorrhage. Caspofungin concentrations were measured by using high-performance liquid chromatography, and a two-compartment population pharmacokinetic analysis was performed.ResultsIn the shock group, the volume of blood removed was 39 ± 7 mL/kg and a volume of 90 ± 17 mL/kg saline was infused throughout the resuscitation period. The extravascular lung water index was higher in the shock group (9.3 ± 1.6 mL/kg vs 5.7 ± 1 mL/kg in the control group; P < 0.01). In the shock group, the median (interquartile range) maximal plasma concentration was 37% lower than in the control group (21.6 μg/mL (20.7 to 22.3) vs 33.1 μg/mL (28.1 to 38.3); P < 0.01). The median area under curve (AUC) from zero to four hours was 25% lower in the shock group than in the control group (60.3 hours × μg/mL (58.4 to 66.4) vs 80.8 hours × μg/mL (78.3 to 96.9); P < 0.01), as was the median lung caspofungin concentration (1.22 μg/g (0.89 to 1.46) vs 1.64 μg/g (1.22 to 2.01); P < 0.01). However, the plasma-to-tissue ratios were not different between the groups, indicating that lung diffusion of caspofungin was not affected after shock followed by fluid loading. Pharmacokinetic analysis showed that the peripheral volume of distribution of caspofungin and intercompartmental clearance were significantly higher in the shock group, as was the total apparent volume of distribution.ConclusionsHypovolaemic shock followed by fluid loading in the pig results in a significant increase in the apparent volume of distribution of caspofungin and in a decrease in its plasma and pulmonary exposition. Although our model was associated with capillary leakage and pulmonary oedema, our results should be generalised to the septic shock with caution. Future investigations should focus on monitoring plasma caspofungin concentrations and optimal caspofungin dosing in shock patients.

Niveau de preuve du suivi therapeutique pharmacologique de la ribavirine

Ribavirin in combination with pegylated interferon alpha is the current treatment for chronic hepatitis C (HCV). Ribavirin presents a wide inter-individual pharmacokinetic variability and adequate exposure seems crucial for achieving sustained virologic response. Severe anaemia frequently occurred under ribavirin treatment and is a dose-dependent limiting side effect. Several studies have been carried out in HVC-infected or HIV-HCV co-infected patients to evaluate the pharmacokinetic-pharmacodynamic relationships of ribavirin. Achievement of a sustained virologic response, defined as undetectable HCV-RNA six months after the end of treatment, have been significantly associated with ribavirin concentration. A cut-off for the trough concentration of ribavirin ranging between 2-3 μg/ml at week 4 has been proposed. A significant correlation has also been reported between ribavirin concentration and the extent of haemoglobin decline. A ribavirin concentration >2 μg/ml is significantly associated to an increase risk of severe anaemia. Non randomized studies have shown that therapeutic drug monitoring of ribavirin improve the management of therapeutic response and haematologic toxicity. Therefore, the level of evidence of the therapeutic drug monitoring of ribavirin is recommended.

Pharmacogenetics of anti-cancer drugs: State of the art and implementation – recommendations of the French National Network of Pharmacogenetics

Individualized treatment is of special importance in oncology because the drugs used for chemotherapy have a very narrow therapeutic index. Pharmacogenetics may contribute substantially to clinical routine for optimizing cancer treatment to limit toxic effects while maintaining efficacy. This review presents the usefulness of pharmacogenetic tests for some key applications: dihydropyrimidine dehydrogenase (DPYD) genotyping for fluoropyrimidine (5-fluorouracil, capecitabine), UDP glucuronosylstransferase (UGT1A1) for irinotecan and thiopurine S-methyltransferase (TPMT) for thiopurine drugs. Depending on the level of evidence, the French National Network of Pharmacogenetics (RNPGx) has issued three levels of recommendations for these pharmacogenetic tests: essential, advisable, and potentially useful. Other applications, for which the level of evidence is still discussed, will be evoked in the final section of this review.

Clinical application, limits and perspectives of pharmacogenetic and pharmacokinetic analysis of anticancer drugs

Despite significant progress in the discovery and design of drugs, the interindividual variability to the standard dose of a given drug remains a serious problem in clinical practice. In the future, the aim of pharmacogenetic is to provide new strategies for optimizing drug therapy, both in terms of efficacy and safety. The clinical validation of an increasing number of pharmacogenetic tests, as well as the development of new highly efficient technologies should further promote pharmacogenetics in clinical practice and lead to the optimization and individualization, before treatment, of drug therapy. Therapeutic drug monitoring is a valid tool to determine the pharmacokinetic of a drug and individualized drug therapy, adjusting patients dose requirement through the measurement and interpretation of drug concentrations. Thus, phenotyping and genotyping tests are now available that determine or predict the metabolic status of an individual and enable the evaluation of risk of drug failure or toxicity. Based on clinical applications, this review focuses on interest of pharmacogenetics, in combination with anticancer agents TDM, on the individualization of treatments used in oncology.

Pharmacogenetics of antidepressant drugs: State of the art and clinical implementation – recommendations from the French National Network of Pharmacogenetics

Tailoring antidepressant drug therapy to each individual patient is a complex process because these drugs have adverse effects leading to discontinuation. Pharmacogenetics may provide useful information in routine practice for optimizing antidepressant treatment by helping limit toxic effects while maintaining efficacy. This review presents the usefulness of pharmacogenetic tests for P450 cytochromes CYP2C19 and CYP2D6 in psychiatric patients taking antidepressants. Depending on the level of evidence, the French National Network of Pharmacogenetics (RNPGx) has issued recommendations stating that pharmacogenetic tests for CYP2D6 and CYP2C19 genes are potentially useful in psychiatric patients treated with antidepressant drugs.