Thèse doctorat : Pharmacie. Pharmaco-toxico-génétique : Université de Nantes : 2003. / Bibliogr. f. 112-120.

This study determined whether phenotype or genotype tests for thiopurine methyltransferase (TPMT) are cost effective interventions for guiding doses of 6-mercaptopurine in children with acute lymphoblastic leukemia (ALL) compared to standard weight-based dosing. A systematic review of the literature was conducted to assess the accuracy of the TPMT technologies, followed by a cost effectiveness analysis which compared genotype, phenotype and weight-based dosing strategies over a three month time horizon. Both TPMT phenotype and genotype technologies were considered accurate though there is no gold standard. Additionally, included studies were of low methodological quality. Neither of the interventions showed a benefit in survival and both were more costly compared to standard weight-based dosing. At this time there is insufficient evidence to recommend the use of phenotype or genotype testing prior to 6-mercaptopurine therapy to guide initial doses in pediatric ALL patients.

This study determined whether phenotype or genotype tests for thiopurine methyltransferase (TPMT) are cost effective interventions for guiding doses of 6-mercaptopurine in children with acute lymphoblastic leukemia (ALL) compared to standard weight-based dosing. A systematic review of the literature was conducted to assess the accuracy of the TPMT technologies, followed by a cost effectiveness analysis which compared genotype, phenotype and weight-based dosing strategies over a three month time horizon. Both TPMT phenotype and genotype technologies were considered accurate though there is no gold standard. Additionally, included studies were of low methodological quality. Neither of the interventions showed a benefit in survival and both were more costly compared to standard weight-based dosing. At this time there is insufficient evidence to recommend the use of phenotype or genotype testing prior to 6-mercaptopurine therapy to guide initial doses in pediatric ALL patients.

No description available.

Acute lymphoblastic leukemia, one of the most malignant cancer forms in children is commonly treated with the thiopurine 6-mercaptopurine (6-MP) in combination with a high dose of methotrexate (MTX). 6-Mercaptopurine is in the body metabolized by the enzyme thiopurine S-methyltransferase (TPMT). Polymorphic variants of TPMT express different catalytic activities, and for this reason the dosage of 6-MP needs to be individualized. In order to better optimize the treatment it is important to understand how mutations in TPMT affect its enzymatic activity. In this thesis we have investigated how the wild type and two variants of TPMT interact with different ligands using fluorescence and isothermal titration calorimetry. Experiments with MTX, ANS and furosemide resulted in a similar binding strength for the wild type and the variant TPMT*8, while the other variant TPMT*6 showed a slightly weaker binding. A binding affinity for polyglutamated MTX to TPMTwt was also determined which resulted in an almost twice as strong binding compared to MTX. Today’s methods to determine enzymatic activity are either based on radioactivity, time consuming or expensive. As an alternative the use of a spectrophotometric assay using 5-thio-2-nitrobenzoic acid (TNB) was investigated. The method showed positive results and could hopefully be adapted to plate readers in future experiments. Using 5.5’-dithiobis-(2-nitrobenzoic acid) (DTNB, also known as Ellman’s reagent) the amount of accessible thiol groups on the protein was estimated. This revealed a similar relationship between TPMTwt and TPMT*6, while the result for TPMT*8 was inconclusive.

Human thiopurine methyltransferase (TPMT) is an enzyme involved in the metabolism of thiopurine drugs, which are widely used in leukemia and inflammatory bowel diseases such as ulcerative colitis and Crohn´s disease. Due to genetic polymorphisms, approximately 30 protein variants are present in the population, some of which have significantly lowered activity. TPMT *5 (Leu49Ser) is one of the protein variants with almost no activity. The mutation is positioned in the hydrophobic core of the protein, close to the active site. Hydrogen exchange rates measured with NMR spectroscopy for N-terminally truncated constructs of TPMT *5 and TPMT *1 (wild type) show that local stability and hydrogen bonding patterns are changed by the mutation Leu49Ser. Most residues exhibit faster exchange rates and a lower local stability in TPMT *5 in comparison with TPMT *1. Changes occur close to the active site but also throughout the entire protein. Calculated overall stability is similar for the two constructs, so the measured changes are due to local stability. Protein dynamics measured with NMR relaxation experiments show that both TPMT *5 and TPMT *1 are monomeric in solution. Millisecond dynamics exist in TPMT *1 but not in TPMT *5, even though a few residues exhibit a faster dynamic. Dynamics on nanosecond to picosecond time scale have changed but no clear trends are observable.

Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2018-07-04T14:43:46Z No. of bitstreams: 1 alinecorrearibeiro.pdf: 2333411 bytes, checksum: 7c0df6693f47a6872d99460a06bc865b (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-07-06T14:24:16Z (GMT) No. of bitstreams: 1 alinecorrearibeiro.pdf: 2333411 bytes, checksum: 7c0df6693f47a6872d99460a06bc865b (MD5) / Made available in DSpace on 2018-07-06T14:24:16Z (GMT). No. of bitstreams: 1 alinecorrearibeiro.pdf: 2333411 bytes, checksum: 7c0df6693f47a6872d99460a06bc865b (MD5) Previous issue date: 2017-08-29 / Devido à importância que o sistema imune desempenha na doença de Crohn (DC), as tiopurinas são os imunomoduladores mais indicados na terapia. Entretanto, as tiopurinas, como a Azatioprina (AZA) e seus metabólitos intraeritrocitários, levam a uma série de reações adversas ou falha terapêutica, podendo ocasionar em não adesão ou abandono da terapia. A conversão da AZA para os nucleotídeos ativos de 6-tioguanina (6-TGN) é necessária para a eficácia clínica, entretanto, outro metabólito, a 6-metilmercaptopurina (6-MMP), é formado através de uma via concorrente pela tiopurina metil transferase e está relacionado à hepatotoxicidade. Devido à ampla variabilidade interindividual da tiopurina metil transferase e a uma faixa terapêutica estreita, torna-se importante a realização do monitoramento terapêutico do metabólito ativo 6-TGN e da 6-MMP. Neste trabalho, um método cromatográfico (CLAE/HPLC-UV) foi desenvolvido e validado para a quantificação dos metabólitos nos eritrócitos, envolvendo um procedimento de tratamento simples baseado na desproteinização por ácido perclórico seguido de hidrólise ácida e aquecimento para a conversão dos metabólitos em suas respectivas bases livres. A cromatografia foi realizada em coluna C18 (250 x 4,6 mm, 5 μm). A fase móvel consistiu em mistura de solução tampão fosfato de potássio (0,02 mol/L, pH = 3), acetonitrila e metanol, eluição por gradiente, num fluxo de 1,0 mL/minuto, com detecção de UV em 291 ηm e 342 ηm. Os tempos de retenção foram de 6,2 min (6-TGN); 23,1 min (6-MMP) e 24,7 min (cafeína: padrão interno). A resposta do detector foi linear na concentração de 0,89-29,91 μmol/L (r=0,999) para 6-TGN e entre 0,90-30,08 μmol/L (r=0,999) para 6-MMP. Os limites de detecção foram de 0,29 μmol/L e 0,30 μmol/L e os limites de quantificação foram de 0,89 μmol/L e 0,90 μmol/L, para 6-TGN e 6-MMP respectivamente. As médias das recuperações de 87,9% para 6-TGN e 91,9% para 6-MMP. Os CV da repetibilidade, de 5,48 e 10,48% (intradia) e 9,23 e 10,48% (interdia), enquanto os EPR da reprodutibilidade de 11,36 e 9,85% (intradia) e 10,48 e 7,32% (interdia) para 6-TGN e 6-MMP, respectivamente. As concentrações de 6-TGN e 6-MMP foram determinadas para todos os pacientes do estudo e os resultados encontrados variaram de 4,51 a 1515,27 ρmol/8 x 10⁸ eritrócitos para a 6-TGN e de 169,98 a 53951,53 ρmol/8 x 10⁸ eritrócitos para a 6-MMP. Observou-se uma correlação entre os pacientes em terapia combinada AZA e alopurinol e a diminuição da dosagem de AZA, consequentemente a diminuição significativa dos níveis de 6-MMP (2030,71 ρmol/8 x 10⁸ eritrócitos) em comparação com o grupo de pacientes sob monoterapia (9098,43 ρmol/8 x 10⁸ eritrócitos). Um outro achado foi a diminuição estatisticamente significativa da transaminase TGO/AST (25,03 + 18,62 U/L) no grupo de pacientes que apresentavam a doença em atividade, com os níveis de 6-TGN a 540,51 ρmol/8 x 10⁸ eritrócitos e de 6-MMP a 7952,32 ρmol/8 x 10⁸ eritrócitos, semelhante a relatos anteriores da literatura. O método proposto de quantificação por CLAE-UV mostrou-se preciso, exato e reprodutível, podendo ser utilizado como uma importante ferramenta na rotina de monitorização terapêutica de pacientes com DC, permitindo a individualização da dose, o acompanhamento dos efeitos adversos relacionados com a terapia farmacológica, o monitoramento da adesão ao tratamento e a avaliação da evolução clínica do paciente. / The conversion of azathioprine (AZA) to active nucleotides of 6-thioguanine (6-TGN) is essential for clinical efficacy in Crohn's disease. However, other metabolite, 6-methylmercaptopurine (6-MMP), which is formed through a competitive pathway for thiopurine methyltransferase (TPMT), is related to hepatotoxicity of this drug. Due to the wide interindividual variability of TPMT and a narrow therapeutic range it is important to accomplish the therapeutic monitoring of active metabolite 6-TGN and 6-MMP, which is an unusual procedure in Brazil. In this study, a HPLC-UV method for simultaneous quantification of these metabolites was developed, validated and applied in 37 Crohn's disease patients. The chromatographic process was performed on C18 column (250 x 4.6 mm, 5 μm i.d.), mobile phase consisted of potassium phosphate buffer (0.02 mol/L, pH = 3), acetonitrile and methanol, flow rate at 1.0 ml/min and UV detection at 291 ηm and 342 ηm. Retention times were 6.2 min (6-TGN); 23.1 min (6-MMP) and 24.7 min (caffeine: internal standard). The detector response was linear at 0.89-29.91 μmol/L (r=0.999) for 6-TGN and 0.90-30.08 μmol/L (r=0.999) for 6-MMP. Limits of detection were 0.29 μmol/L and 0.30 μmol/L, while the quantification limits were 0.89 μmol/L and 0.90 μmol/L, for 6-TGN and 6-MMP respectively. Precision, accuracy and recovery, were according FDA and ANVISA guidelines. The concentrations of 6-TGN and 6-MMP were determined in patients’ blood and the results found ranged from 4.51 to 1515 ρmol/8 x 10⁸ erythrocytes for 6-TGN and from 169.98 to 53.951 ρmol/8 x 10⁸ erythrocytes for 6-MMP. It was observed a reduction of levels of 6-MMP in patients using AZA + allopurinol therapy (2030.7 ρmol/8 x 10⁸ erythrocytes) when compared with patients undergoing monotherapy (9098.43 ρmol/8 x 10⁸ erythrocytes). Another finding was the correlation between the decrease in GOT transaminase in the group of patients who had the active disease with the increase in the 6-TGN levels, similar to previous reports in the literature. These results indicate that the method developed was reliable, accurate and reproducible, and can be used as an important tool in the routine monitoring of patients with Crohn's disease, allowing the individualization of the dose, the monitoring of the adverse effects related to the pharmacological therapy, monitoring the adherence to the treatment and the evaluation of the clinical evolution of these patients.

Les thiopurines sont des médicaments cytotoxiques et immunosuppresseurs largement prescrits, notamment dans les maladies inflammatoires chroniques de l’intestin (MICI). Ils représentent l’un des meilleurs exemples d’application clinique de la pharmacogénétique avec le dépistage du déficit en thiopurine S-méthyltransférase (TPMT), enzyme clé du métabolisme des thiopurines. La variabilité interindividuelle de la réponse à ces médicaments rend nécessaire leur optimisation thérapeutique. Ce travail de thèse a d’une part, analysé les relations entre activité TPMT et concentrations des métabolites thiopuriniques, et d’autre part, recherché des facteurs associés à la résistance aux thiopurines. A l’aide d’une base de données pharmacogénétiques hospitalière et d’une étude « PheWAS » à partir d’un entrepôt de données cliniques, nous avons analysé la distribution et la corrélation génotype-phénotype pour la TPMT, en lien avec les concentrations des métabolites thiopuriniques. Nous avons observé qu’une activité TPMT très élevée (phénotype « ultra-rapide ») était associée à des paramètres clinico-biologiques reflétant une maladie évolutive et un traitement inefficace dans les MICI. De plus, une étude clinique rétrospective dans les MICI pédiatriques a permis d’identifier des facteurs associés à la lymphopénie observée sous thiopurines. Enfin, à partir d’un modèle in vitro fondé sur des lignées cellulaires lymphoblastoïdes (LCL) sélectionnées, nous avons établi une signature transcriptomique, incluant 32 gènes, prédictive de la résistance aux thiopurines. Une analyse fonctionnelle bioinformatique a abouti à l’identification de voies métaboliques liées à la protéine p53 et au cycle cellulaire, ainsi que des mécanismes moléculaires associés à la résistance aux thiopurines. En conclusion, ce travail de thèse, qui a exploré la variabilité de réponse aux thiopurines et tout particulièrement la résistance à ces médicaments, propose des hypothèses pour l’individualisation et l’optimisation thérapeutique des thiopurines. / Thiopurines are cytotoxic and immunosuppressive drugs widely prescribed, mainly in inflammatory bowel disease (IBD). They constitute one of the best success story of pharmacogenetic implementation into clinical practice based on the screening of thiopurine S-methyltransferase (TPMT) deficiency, a key enzyme in thiopurine metabolism. Optimization of thiopurine response is challenging because of its large interindividual variability such as inefficacy and toxicities. This thesis has explored, on one hand, the relationships between TPMT activity and metabolite concentrations, and on the other hand, factors associated with thiopurine inefficacy. Using a primary care pharmacogenetic database, we first analyzed TPMT distribution and genotype-phenotype correlation, in relation with thiopurine metabolites in a large population. Using a PheWAS study based on a clinical data warehouse we then reported that a very high TPMT activity (“ultra-rapid” phenotype) was associated with parameters of active IBD and poor response to thiopurines. Furthermore, a retrospective study in pediatric IBD identified factors predicting the occurrence of lymphopenia during thiopurine therapy. Finally, using a lymphoblastoid cell line (LCL) in vitro model, we established a transcriptomic signature, including 32 genes predicting thiopurine cellular resistance. A bioinformatic functional analysis identified metabolic pathways in relation with p53 and cell cycle, as well as molecular mechanisms associated with thiopurine resistance. To conclude, this research work, focusing on the variability of thiopurine response and mainly therapeutic resistance, provides new hypotheses to individualize and optimize therapeutic response to thiopurines.

La présente étude a pour objectif de mettre en évidence l‘intérêt du suivi thérapeutique pharmacologique (STP) des métabolites thiopuriques en vue de l‘optimisation du traitement par l‘azathioprine chez les enfants atteints de maladie inflammatoire de l‘intestin et d‘hépatite autoimmune. Les travaux réalisés nous ont permis de montrer, en utilisant une analyse multi-niveaux, une corrélation significative entre la dose d‘azathioprine et les concentrations en 6-TGN et Me6-MPN ainsi qu‘avec le ratio Me6-MPN/6-TGN confortant l‘utilisation des métabolites pour ajuster la posologie d‘azathioprine chez les enfants présentant une maladie inflammatoire de l‘intestin. Différents facteurs pouvant modifier les concentrations de métabolites thiopuriques ont été identifiés. La co-administration d‘infliximab a conduit à une augmentation significative des concentrations de 6-TGN. Des concentrations plus faibles de 6-TGN ont été observées chez les jeunes enfants suggérant l‘influence de l‘âge sur le métabolisme ou sur l‘absorption de l‘azathioprine. Nous avons également montré qu‘une concentration de 6-TGN supérieure à 405 pmol/8.108RBCs chez des patients ayant une activité TPMT normale et pour lesquels la rémission clinique n‘a pas pu être obtenue en l‘absence de stéroïdes, était prédictive d‘une résistance à l‘azathioprine. Un seuil de 250 pmol/8.108RBCs en 6-TGN est significativement associé à une meilleure réponse thérapeutique. D‘autre part, une corrélation a été observée entre les métabolites thiopuriques et la leucopénie. Chez les enfants atteints d‘hépatite autoimmune, une corrélation positive entre la dose d‘azathioprine et les concentrations de métabolites a été retrouvée. L‘importante variabilité inter-individuelle dans les concentrations en métabolites thiopuriques et dans la réponse thérapeutique a été confirmée démontrant l‘intérêt d‘une individualisation de la thérapeutique. L‘instauration d‘un STP des métabolites thiopuriques associé au suivi hématologique, à la détermination de la TPMT et au suivi clinique paraît justifié afin d‘optimiser la thérapeutique par l‘azathioprine dans la population pédiatrique / The present study aimed to investigate the usefulness of thiopurine metabolite monitoring in pediatric inflammatory bowel disease (IBD) and Autoimmune Hepatitis (AIH) for optimizing azathioprine therapy. Using multilevel analysis, we demonstrated for the first time the significant positive correlations between the weight-based azathioprine dosage and the 6-thioguanine nucleotide (6-TGN) and 6-methyl-mercaptopurine (6-MeMPN) levels as well as 6-MeMPN/6-TGN ratio, supporting the use of metabolites to adjust dosing in IBD children. Other factors affecting metabolite levels were also identified. Co-administration of infliximab resulted in a significant increase in 6-TGN levels. Younger children exhibited lower metabolite levels, suggesting the influence of age on metabolism/absorption of azathioprine. We also reported that a 6-TGN level above 405 pmol/8.108RBCs in IBD children with normal TPMT activity who did not achieve steroid-free clinical remission was predictive of azathioprine refractoriness. A cut-off of 250 pmol/8.108RBCs for 6-TGN was found to be significantly associated with higher therapeutic response. Moreover, both 6-TGN and 6-MeMPN levels were correlated with leucopenia. In AIH children, a positive correlation between azathioprine dosage and metabolite levels was also observed. The wide variability in thiopurine metabolites and therapeutic response in both IBD and AIH children was confirmed, pointing to the important role of treatment individualization. Monitoring of thiopurine metabolites combined with hematological tests, TPMT activity and clinical evaluation may be of interest for optimizing thiopurine therapy and minimizing toxicity in IBD and AIH children

Les médicaments thiopuriniques que sont l'azathioprine, la 6-mercaptopurine et la 6-thioguanine sont utilisés depuis des décennies pour leurs propriétés cytotoxiques et immunosuppressives dans le traitement de certaines leucémies, de maladies inflammatoires chroniques ou auto-immunes ainsi que dans la prévention du rejet de greffe. Certains patients, traités par des doses conventionnelles de ces molécules, développent cependant des effets indésirables parfois très sévères. Le déficit d'activité, d'origine génétique, de la thiopurine S-méthyltransférase (TPMT), enzyme impliquée dans le métabolisme des thiopurines, constitue l'un des facteurs majeurs de la myélotoxicité de ces médicaments. La détermination du phénotype TPMT par génotypage, qui est une mesure préventive avant l'introduction d'un traitement thiopurinique, repose sur l'identification des mutations inactivatrices les plus fréquentes du gène TPMT. Une partie de ce travail a consisté en l'analyse fonctionnelle de quatre variants alléliques rares du gène TPMT dans un système d'expression hétérologue, la levure S. cerevisiae. Le caractère non-fonctionnel de deux d'entre eux a ainsi été démontré. Cependant, le déficit d'activité de la TPMT ne permet d'expliquer qu'environ 30 % des cas de myélotoxicité sous thiopurines, ce qui laisse supposer l'existence d'autres anomalies génétiques affectant d'autres gènes impliqués dans la réponse de l'organisme à ces molécules. Ainsi, nous avons étudié le polymorphisme génétique de deux autres protéines candidates, celui de l'inosine monophosphate déshydrogénase de type 2 (IMPDH2), enzyme-clé de la formation des métabolites actifs des thiopurines, et celui de la RhoGTPase RAC1, qui est l'une des cibles pharmacologiques de ces molécules. Certains des polymorphismes que nous avons identifiés dans ces deux gènes semblent affecter in vitro l'expression et/ou l'activité de ces protéines et pourraient, par conséquent, contribuer aux variations inter-individuelles de réponse aux thiopurines