Thesis (Ph. D.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains xi, 150 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.

Class of 2014 Abstract / Specific Aims: Busulfan is a chemotherapy used in conditioning regimens for hematopoeitic stem cell transplant (HSCT) that requires therapeutic drug monitoring (TDM) to reduce ther risk of adverse effects. Variable oral absorption and several studies demonstrating decreased toxicity with the intravenous formulation have led to IV preference despite the lower acquisition cost of oral busulfan. However, these studies failed to consider therapeutic drug monitoring and their results may therefore be flawed. The objective of this retrospective chart review was to determine the adverse effect, outcome profile, and cost-effectiveness of IV versus PO busulfan at a single medical center under TDM. Methods: This quality improvement project was a retrospective cohort analysis using patient data from a single large academic medical center from January 2007 to April 2013. Patients were included if they were 18 years or older and had undergone HSCT using either IV or PO busulfan using standard dosing regimens. This data was then used to design a cost-effectiveness model in order to determine if IV or PO busulfan is cost effective. Main Results: There were 68 subjects receiving autologous transplants and 37 subjects receiving allogeneic transplants that received busulfan as part of their pretreatment therapy and were included in this study. Allogeneic and autologous transplant populations were analyzed separately. In both populations there was no difference in occurrence of pulmonary toxicity, HVOD, or mucositis between the IV or PO groups. IV busulfan was significantly associated with an increased need for patient controlled analgesia in both autologous and allogeneic populations (p=0.038 and 0.028 respectively). Total cost of PO therapy was $30,081 and $30,047 less than IV for autologous and allogeneic transplants, respectively. PO therapy also represented a cost savings of $41 and $57 dollars for autologous and allogeneic transplants, respectively. This was confirmed through bootstrapping technique, which found PO to be dominant to IV busulfan. Conclusion: In conclusion, this study finds PO busulfan to be a therapeutically equivalent and cost saving option as part of a pretreatment regimen for both autologous and allogeneic hematopoietic stem cell transplants when therapeutic drug monitoring is performed.

La greffe de cellules souches hématopoïétiques est parfois le seul traitement curatif dans certaines pathologies pédiatriques telles que les leucémies, les sarcomes, les dédicits immunitaires ou les thalassémies. Le busulfan, un alkylant myéloablatif, fait partie de nombreux protocoles de conditionnement de greffe. C'est un médicament à marge thérapeutique étroite doté d'une forte variabilité pharmacocinétique, qui fait souvent l'objet d'un suivi thérapeutique pharmacologique afin d'optimiser la prise de greffe et d'éviter les risques de maladie veino-occlusive, principale toxicité du busulfan et responsable d'une morbidité et d'une mortalité importante. L'aire sous la courbe, dont il existe un intervalle cible recommandé, est aujourd'hui le paramètre pharmacocinétique utlisé pour effectuer le suivi thérapeutique du busulfan et l'adaptation posologique pendant le conditionnement.L'objectif de notre travail est d'étudier les relations entre la pharmacocinétique du busulfan et ses effets thérapeutiques et toxiques, en particulier la maladie veino-occlusive, et de développer des méthodes d'adaptation posologique pour optimiser l'usage de ce médicament chez l'enfant. Nos travaux ont conduit à plusieurs innovations méthodologiques, avec le développement et la validation d'un modèle pharmacocinétique de population non-paramétrique pour l'adaptation Bayésienne des posologies de busulfan en pédiatrie, et le développement d'une nouvelle méthode de détermination de la dose initiale maximisant la probabilité d'atteindre un intervalle cible d'exposition. Sur le plan clinique, nous avons pu mettre en évidence l'absence de bénéfice clinique de l'utilisation d'un intervalle cible d'exposition plus restreint que celui recommandé. Par ailleurs, nous avons identifié que la survenue de la MVO était liée à la concentration maximale de busulfan, et non à l'aire sous la courbe des concentrations en fonction du temps.L'ensemble de ces résultats est une contribution à l'amélioration de l'utilisation et du suivi thérapeutique pharmacologique du busulfan en onco-hématologie pédiatrique / Hematopoietic stem cell transplantation remains the only curative treatment in many pediatric diseases as leukemia, sarcoma, immunodeficiencies or thalassemia. Busulfan, a myeloablative alkylant, is the cornerstone of pre-transplant conditioning. It has a narrow therapeutic index and a large pharmacokinetic variability. For these reasons, therapeutic drug monitoring is required in order to optimize engraftment and avoid veno-occlusive disease, the main toxicity of busulfan which is responsible of significant morbidity and mortality. Today, the area under the curve, of which there is a target range recommended, is the pharmacokinetic parameter used to carry out therapeutic drug monitoring and dose adjustment during conditioning. Our objective is to investigate relationships between busulfan PK and clinical outcomes, especially veno-occlusive disease, and to develop methods of dose adjustment in order to optimize the use of this medication in children.Our work leaded to several methodological innovations, with the development and the validation of a non-parametric pharmacokinetic model for Bayesian dose adjustment of busulfan in pediatrics, and the development of a new method for the first dose determination maximizing the probability of achieving an exposure target range. From a clinical point a view, we highlighted the lack of clinical benefit in using an exposure target range narrower than those recommended. Furthermore, we identified that veno-occlusive incidence was correlated to the maximal concentration of busulfan, contrary to the area under the concentration-time curve.All of these results contribute to improving use and therapeutic monitoring of busulfan in pediatric onco-hematology

Dans le contexte de la physiologie comparée de la reproduction, les amphibiens sont peu étudiés. Le travail réalisé durant cette thèse visait à analyser des marqueurs de différenciation testiculaire chez l'urodèle Pleurodeles waltl, dont le déterminisme génétique du sexe (ZZ/ZW) peut être influencé par la température. Nos études ont d'abord porté sur le gène sox9 marqueur de la différenciation testiculaire chez les vertébrés supérieurs. Le gène cloné chez le pleurodèle montre une bonne conservation par rapport aux autres vertébrés. Son expression plus élevée dans la gonade mâle n'apparaît que tardivement suggérant qu'il n'est probablement pas impliqué dans les stades précoces de la différenciation testiculaire. En outre, son expression dans le mésonéphros rend difficile son utilisation comme marqueur de différenciation testiculaire. Nous avons ensuite étudié l'Amh, hormone testiculaire impliquée dans la régression des canaux de Müller chez de nombreux vertébrés. Son expression spécifique de la gonade, précocement plus élevée chez les larves ZZ que les ZW en font un excellent marqueur de la différenciation testiculaire. Le fait que les pleurodèles mâles voient les canaux de Müller persister malgré la présence d'Amh suggère que la fonction primaire de cette hormone était en relation avec la différenciation gonadique et que la fonction de régression des canaux de Müller n'est apparue que secondairement au cours de l'évolution. Ces marqueurs ont été mis à profit pour caractériser le phénotype gonadique lors d'inversions sexuelles ou lors de développements en absence de cellules germinales. Ils ont permis de montrer que les cellules germinales ne semblent pas jouer de rôle dans la différenciation gonadique du pleurodèle / In the context of comparative physiology of reproduction, amphibians are poorly studied. This work was dedicated to the analysis of testis differentiation markers in the newt Pleurodeles waltl, which shows a ZZ/ZW genetic mode of sex determination that can be affected by temperature. First, we studied sox9, a testis differentiation marker well characterized in many higher vertebrates. The gene cloned in Pleurodeles shows a good level of identity with other vertebrates. The testis-enriched expression appears late during the testis differentiation process indicating that it is probably not involved in the early steps of testis differentiation. Its use as a marker of testicular differentiation proved difficult since it is expressed not only in the gonads but also in the mesonephros. Then, we studied amh, a testis hormone responsible for müllerian duct regression in many vertebrates. Its early expression in the gonad, significantly higher in male than in female larvae makes it an excellent marker for testis differentiation. Since in Pleurodeles waltl, Müllerian ducts persist in males, it suggests that during the course of evolution, the function of Amh on the regression of Müllerian ducts appeared secondarily after its role in gonadal differentiation. These markers have been used to characterize the gonadal phenotype during sex reversal, or in gonads developed in the absence of germ cells. They showed that these cells do not seem to play a role in gonadal differentiation of Pleurodeles waltl

Busulfan, cyclophosphamide, and etoposide (BuCyE) is a commonly used conditioning regimen for autologous stem cell transplantation (ASCT). This multicenter, phase II study examined the safety and efficacy of BuCyE with individually adjusted busulfan based on preconditioning pharmacokinetics. The study initially enrolled Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL) patients ages 18 to 80 years but was amended due to high early treatment-related mortality (TRM) in patients > 65 years. BuCyE outcomes were compared with contemporaneous recipients of carmustine, etoposide, cytarabine, and melphalan (BEAM) from the Center for International Blood and Marrow Transplant Research. Two hundred seven subjects with HL (n = 66) or NHL (n = 141) were enrolled from 32 centers in North America, and 203 underwent ASCT. Day 100 TRM for all subjects (n = 203), patients > 65 years (n = 17), and patients ≤ 65 years (n = 186) were 4.5%, 23.5%, and 2.7%, respectively. The estimated rates of 2-year progression-free survival (PFS) were 33% for HL and 58%, 77%, and 43% for diffuse large B cell lymphoma (DLBCL; n = 63), mantle cell lymphoma (MCL; n = 29), and follicular lymphoma (FL; n = 23), respectively. The estimated rates of 2-year overall survival (OS) were 76% for HL and 65%, 89%, and 89% for DLBCL, MCL, and FL, respectively. In the matched analysis rates of 2-year TRM were 3.3% for BuCyE and 3.9% for BEAM, and there were no differences in outcomes for NHL. Patients with HL had lower rates of 2-year PFS with BuCyE, 33% (95% CI, 21% to 46%), than with BEAM, 59% (95% CI, 52% to 66%), with no differences in TRM or OS. BuCyE provided adequate disease control and safety in B cell NHL patients ≤ 65 years but produced worse PFS in HL patients when compared with BEAM.

O bussulfano (BU) e a ciclofosfamida (CY) são fármacos utilizados nos regimes de condicionamento pré-transplante de células tronco hematopoéticas (TCTH). O BU apresenta estreito intervalo terapêutico, alta variabilidade interindividual na farmacocinética e graves reações adversas. O presente estudo avaliou a administração de uma dose teste de BU oral para a individualização do regime de dosagem, definiu o melhor tempo de coletas esparsas para o monitoramento terapêutico do BU e validou um algoritmo baseado em modelo compartimental e farmacocinética populacional em pacientes submetidos ao TCTH. Trinta pacientes portadores de doenças hematológicas tiveram o tratamento com BU individualizado baseado em uma dose teste oral de 0,25 mg/Kg de BU. As doses foram baseadas no clearance aparente calculado na dose teste e as concentrações plasmáticas foram confirmadas após a quinta dose de tratamento. Os coeficientes de variação obtidos entre os valores de clearance avaliados na dose teste e na quinta dose foram <= 30%, exceto para 5 pacientes. Não foram observadas associação entre os parâmetros farmacocinéticos do BU e a evolução clínica dos pacientes. Com a finalidade de estimar os melhores tempos de coletas ideais para aplicação no monitoramento terapêutico do BU, um modelo farmacocinética populacional foi utilizado e um esquema de coletas esparsas com não mais de cinco amostras por paciente (t = 0,5; 2,25; 3; 4 e 5 horas após a dose) demonstrou ser suficiente para a caracterização da farmacocinética do BU. O presente estudo avaliou também a farmacocinética dos enantiômeros da ciclofosfamida (CY) e seus metabólitos (4-hidroxiciclofosfamida e carboxiciclofosfamida), em pacientes submetidos ao TCTH. Foram investigados pacientes portadores de esclerose sistêmica (n=10) e esclerose múltipla (n=10) em regime de condicionamento com 50 mg CY /kg/dia durante 4 dias. Dois ensaios específicos baseados na análise por LC-MS/MS foram desenvolvidos e validados para analisar os enantiômeros da CY e seus metabólito 4- hidroxiciclofosfamida (HCY) e carboxiciclofosfamida (CEPM) em plasma humano. Os parâmetros farmacocinéticos dos enantiômeros da CY e seus metabólitos foram calculados empregando o programa WinNonlin e mostraram acúmulo plasmático dos enantiômeros (S)- (-)-CY (AUC 215, 0 vs 186,2 ?g.h/mL para os paciente EM e 219,1 vs 179,2 ?g.h/mL para os paciente ES) e HCY (1), provavelmente o (R)-(+)-HCY (AUC 5,6 vs 3,7 ?g.h/mL para os paciente EM e 6,3 vs 5,6 ?g.h/mL para os paciente ES) em ambos os grupos de pacientes investigados. A disposição cinética do metabólito CEPM não mostrou enantiosseletividade. A farmacocinética da CY e seus metabólitos HCY e CEPM não diferiu entre os pacientes portadores de EM ou ES. Não foi observado correlação entre o metabolismo da CY e os genótipos avaliados (CYP2B6 e CYP2C9). Não foi possível correlacionar os valores de AUC0-? dos enantiômeros da CY e/ou dos metabólitos HCY e CEPM com a toxicidade ao uso de CY em virtude do pequeno número de pacientes investigados. / Busulfan (BU) and cyclophosphamide (CY) are drugs used during conditioning treatment for hematopoietic stem cell transplantation (HSCT). BU presents narrow therapeutic window, high interindividual variability in the pharmacokinetics and serious adverse effects. The present study evaluated the administration of a BU test dose for dose individualization, set the best sparse sampling scheme for BU therapeutic monitoring and validated an algorithm based on compartmental and population pharmacokinetics model in HSCT patients. Thirty patients received BU individualized treatment based on an oral test dose of 0.25 mg/kg. Doses were based on apparent clearance calculated with BU test dose. Plasma concentrations were confirmed after the fifth treatment dose. Coefficients of variation obtained between the clearance values evaluated in the test dose and fifth dose were <= 30%, except for 5 patients. No association between BU pharmacokinetic parameters and clinical outcome was observed. To estimate the ideal sampling scheme for BU therapeutic drug monitoring, a population pharmacokinetic model was used. Sparse sampling scheme with no more than five samples per patient (t = 0.5, 2.25, 3, 4 and 5 hours after dosing) was shown to be sufficient to characterize the BU pharmacokinetics. This study also evaluated the pharmacokinetics of the cyclophosphamide enantiomers and its metabolites (4-hydroxycyclophosphamide and carboxicyclophosphamide) in HSCT patients. We investigated patients with systemic sclerosis (SS) (n = 10) and multiple sclerosis (MS) (n = 10) in the conditioning regimen with CY 50 mg/kg/day for 4 days. Two specific tests based on LC-MS/MS analysis were developed and validated to analyze the CY enantiomers and its metabolite 4-hydroxycyclophosphamide (HCY) and carboxicyclophosphamide (CEPM) in human plasma. Pharmacokinetics of CY enantiomers and its metabolites were calculated using WinNonlin software and showed plasma accumulation of (S)-(-)-CY (AUC 215.0 vs 186.2 ?g.h/mL for the MS patient and 219.1 vs. 179.2 ?g.h/mL for the SS patient) and HCY (1), probably the (R)-(+)-HCY (AUC 5.6 vs 3.7 ?g.h /mL for MS patients and 6.3 vs 5.6 ?g.h/ mL for the SS patients) enantiomers in both groups of investigated patients. CEPM kinetics disposition showed lack of enantioselectivity. The pharmacokinetics of CY and its metabolites (HCY and CEPM) did not differ between patients with MS or SS. There was no correlation between the metabolism of CY, CYP2B6 and CYP2C9 genotypes. It was not possible to correlate the AUC0-? of CY enantiomers and/or its metabolites (HCY and CEPM) with CY toxicity due to the small number of patients investigated.

Thesis (Ph. D.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains xi, 109 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 92-109).

O bussulfano (BU) e a ciclofosfamida (CY) são fármacos utilizados nos regimes de condicionamento pré-transplante de células tronco hematopoéticas (TCTH). O BU apresenta estreito intervalo terapêutico, alta variabilidade interindividual na farmacocinética e graves reações adversas. O presente estudo avaliou a administração de uma dose teste de BU oral para a individualização do regime de dosagem, definiu o melhor tempo de coletas esparsas para o monitoramento terapêutico do BU e validou um algoritmo baseado em modelo compartimental e farmacocinética populacional em pacientes submetidos ao TCTH. Trinta pacientes portadores de doenças hematológicas tiveram o tratamento com BU individualizado baseado em uma dose teste oral de 0,25 mg/Kg de BU. As doses foram baseadas no clearance aparente calculado na dose teste e as concentrações plasmáticas foram confirmadas após a quinta dose de tratamento. Os coeficientes de variação obtidos entre os valores de clearance avaliados na dose teste e na quinta dose foram <= 30%, exceto para 5 pacientes. Não foram observadas associação entre os parâmetros farmacocinéticos do BU e a evolução clínica dos pacientes. Com a finalidade de estimar os melhores tempos de coletas ideais para aplicação no monitoramento terapêutico do BU, um modelo farmacocinética populacional foi utilizado e um esquema de coletas esparsas com não mais de cinco amostras por paciente (t = 0,5; 2,25; 3; 4 e 5 horas após a dose) demonstrou ser suficiente para a caracterização da farmacocinética do BU. O presente estudo avaliou também a farmacocinética dos enantiômeros da ciclofosfamida (CY) e seus metabólitos (4-hidroxiciclofosfamida e carboxiciclofosfamida), em pacientes submetidos ao TCTH. Foram investigados pacientes portadores de esclerose sistêmica (n=10) e esclerose múltipla (n=10) em regime de condicionamento com 50 mg CY /kg/dia durante 4 dias. Dois ensaios específicos baseados na análise por LC-MS/MS foram desenvolvidos e validados para analisar os enantiômeros da CY e seus metabólito 4- hidroxiciclofosfamida (HCY) e carboxiciclofosfamida (CEPM) em plasma humano. Os parâmetros farmacocinéticos dos enantiômeros da CY e seus metabólitos foram calculados empregando o programa WinNonlin e mostraram acúmulo plasmático dos enantiômeros (S)- (-)-CY (AUC 215, 0 vs 186,2 ?g.h/mL para os paciente EM e 219,1 vs 179,2 ?g.h/mL para os paciente ES) e HCY (1), provavelmente o (R)-(+)-HCY (AUC 5,6 vs 3,7 ?g.h/mL para os paciente EM e 6,3 vs 5,6 ?g.h/mL para os paciente ES) em ambos os grupos de pacientes investigados. A disposição cinética do metabólito CEPM não mostrou enantiosseletividade. A farmacocinética da CY e seus metabólitos HCY e CEPM não diferiu entre os pacientes portadores de EM ou ES. Não foi observado correlação entre o metabolismo da CY e os genótipos avaliados (CYP2B6 e CYP2C9). Não foi possível correlacionar os valores de AUC0-? dos enantiômeros da CY e/ou dos metabólitos HCY e CEPM com a toxicidade ao uso de CY em virtude do pequeno número de pacientes investigados. / Busulfan (BU) and cyclophosphamide (CY) are drugs used during conditioning treatment for hematopoietic stem cell transplantation (HSCT). BU presents narrow therapeutic window, high interindividual variability in the pharmacokinetics and serious adverse effects. The present study evaluated the administration of a BU test dose for dose individualization, set the best sparse sampling scheme for BU therapeutic monitoring and validated an algorithm based on compartmental and population pharmacokinetics model in HSCT patients. Thirty patients received BU individualized treatment based on an oral test dose of 0.25 mg/kg. Doses were based on apparent clearance calculated with BU test dose. Plasma concentrations were confirmed after the fifth treatment dose. Coefficients of variation obtained between the clearance values evaluated in the test dose and fifth dose were <= 30%, except for 5 patients. No association between BU pharmacokinetic parameters and clinical outcome was observed. To estimate the ideal sampling scheme for BU therapeutic drug monitoring, a population pharmacokinetic model was used. Sparse sampling scheme with no more than five samples per patient (t = 0.5, 2.25, 3, 4 and 5 hours after dosing) was shown to be sufficient to characterize the BU pharmacokinetics. This study also evaluated the pharmacokinetics of the cyclophosphamide enantiomers and its metabolites (4-hydroxycyclophosphamide and carboxicyclophosphamide) in HSCT patients. We investigated patients with systemic sclerosis (SS) (n = 10) and multiple sclerosis (MS) (n = 10) in the conditioning regimen with CY 50 mg/kg/day for 4 days. Two specific tests based on LC-MS/MS analysis were developed and validated to analyze the CY enantiomers and its metabolite 4-hydroxycyclophosphamide (HCY) and carboxicyclophosphamide (CEPM) in human plasma. Pharmacokinetics of CY enantiomers and its metabolites were calculated using WinNonlin software and showed plasma accumulation of (S)-(-)-CY (AUC 215.0 vs 186.2 ?g.h/mL for the MS patient and 219.1 vs. 179.2 ?g.h/mL for the SS patient) and HCY (1), probably the (R)-(+)-HCY (AUC 5.6 vs 3.7 ?g.h /mL for MS patients and 6.3 vs 5.6 ?g.h/ mL for the SS patients) enantiomers in both groups of investigated patients. CEPM kinetics disposition showed lack of enantioselectivity. The pharmacokinetics of CY and its metabolites (HCY and CEPM) did not differ between patients with MS or SS. There was no correlation between the metabolism of CY, CYP2B6 and CYP2C9 genotypes. It was not possible to correlate the AUC0-? of CY enantiomers and/or its metabolites (HCY and CEPM) with CY toxicity due to the small number of patients investigated.

O bussulfano (Bu) é um agente alquilante usado no condicionamento que precede o transplante de células-tronco hematopoiéticas (TCTH) em crianças. Sua farmacocinética (FC) apresenta uma grande variabilidade interindivíduo, que pode ser parcialmente explicada pelas variantes genéticas de GSTA1, gene da enzima glutationa S-transferase α1, crucial para o metabolismo do Bu. Vários métodos de predição da FC do Bu são usados para calcular sua dose, essencialmente com base na idade e peso do paciente. Até o momento, apenas um modelo adulto incorporou as variantes de GSTA1 no cálculo da sua dose do Bu. No presente trabalho, avaliou-se, inicialmente, o desempenho de métodos atualmente disponíveis em pediatria, em função das variantes genéticas de GSTA1. Foram avaliados os parâmetros de FC da primeira dose de 101 crianças e adolescentes submetidos a TCTH alogênico no CHU Sainte-Justine, Montreal, Canadá, após regime de condicionamento que incluía Bu intravenoso (BuCR, do inglês busulfan-containing regimen). Os haplótipos GSTA1 foram interpretados em pares (diplótipos) e depois classificados em três grupos com base nos seus diferentes potenciais de expressão enzimática. As AUCs (area under the curve) medidas e as AUCs calculadas a partir de doses de Bu preditas por 11 modelos diferentes foram classificadas de acordo com a sua capacidade para atingir a AUC-alvo (900 a 1.500 μM.min). Também foram calculados os erros de previsão do clearance do Bu. Após a primeira dose, as AUCs medidas atingiram a AUC-alvo em 38,7%. Os diplótipos de GSTA1 relacionados ao metabolismo lento (G3) e regimes contendo fludarabina (FluCR, do inglês fludarabine-containing regimen) foram os únicos fatores associados à AUC no alvo (OR 4,7, IC 95%, 1,1 - 19,8, p = 0,04 e OR 9,9, IC 95%, 1,6 - 61,7, p = 0,01, respectivamente). Utilizando os outros métodos para o cálculo da dose, a percentagem de AUC no alvo variou de 16% a 74%. G3 e FluCR foram, em alguns modelos, associados à AUC no alvo ou na faixa tóxica, enquanto que os metabolizadores rápidos (G1) foram por vezes associados a AUCs subterapêuticas. Essas associações foram confirmadas na análise de predição do clearance, em que os diplótipos da GSTA1 e o regime de condicionamento influenciaram significativamente a maioria dos erros de previsão dos métodos testados. Uma vez que GSTA1 mostrou influenciar significativamente os algoritmos disponíveis, pretendeu-se desenvolver um modelo de FC de população que incluísse variantes genéticas de GSTA1 como um fator no cálculo de dose do Bu. Para tanto, foram analisados os dados de concentração-tempo de 112 crianças e adolescentes que receberam um BuCR mieloablativo antes de 115 TCTH (autólogos e alogênicos), realizados também no CHU Sainte-Justine. Para a construção do modelo de FC de população, utilizou-se uma análise mista não linear. Sexo, doença de base (maligna vs. não maligna), idade pós-menstrual (PMA) ou idade cronológica, regime de condicionamento e diplótipos de GSTA1 foram avaliados como fatores potenciais. Um modelo de um compartimento com eliminação de primeira ordem foi o que melhor descreveu os dados disponíveis. Um fator de maturação do metabolismo de Bu (Fmat) e o peso elevado a exponencial alométrico teórico foram incluídos no modelo de base. A análise dos fatores revelou PMA (ΔOFV = -26,7, p = 2,3x10-7) e grupos de diplótipos de GSTA1 (ΔOFV = -11,7, p = 0,003) como fatores significativamente associados, respectivamente, ao volume e ao CL do Bu. Os CL dos metabolizadores rápidos (G1) foram preditos como sendo 7% mais elevados que os definidos como metabolizadores normais (G2), enquanto que os metabolizadores lentos (G3) foram descritos com CL 12% menor que os G2. Em conclusão, após se evidenciar que os métodos disponíveis para o cálculo de dose do Bu não são adequados para todos os grupos de diplótipos de GSTA1, propôs-se o primeiro algoritmo de cálculo de dose de Bu em pediatria baseado em farmacogenética. Seu uso pode contribuir para uma melhor previsibilidade da FC do Bu e, desta forma, melhor predizer a exposição de crianças e adolescentes à droga, de acordo com a capacidade metabólica de cada indivíduo. / Busulfan (Bu) is an alkylating agent used in the conditioning before hematopoietic stem cells transplantation (HSCT) in children. Its pharmacokinetics (PK) presents a great inter-individual variability, which can be partially explained by GSTA1 genetic variants, gene coding for the enzyme glutathione s-tranferase α1, crucial for Bu metabolism. Several methods of predicting PK are available and are used to calculate the Bu dose, based essentially on patients’ age and anthropometric characteristics. So far, a single adult model successfully incorporated this factor into the Bu dose calculation. In the present work, we initially evaluate the performance of the currently available guidelines across the different GSTA1 genetic variants. The PK parameters from the Bu first doses from 101 children and adolescents who have undergone allogenic SCT at the CHU Sainte-Justine, Montreal, Canada following a IV Bu-containing conditioning regimen (BuCR). GSTA1 haplotypes were interpreted in pairs (diplotypes) and then classified in 3 groups based on different potentials of enzyme expression. Measured AUCs and AUCs calculated from Bu doses predicted by 11 different models were classified according to their ability to achieve the AUC target (900 and 1500μM.min). Clearance prediction errors were also calculated. After the first dose, measured AUCs achieved the target in 38.7%. GSTA1 diplotypes groups related to poor Bu metabolism (G3) and fludarabine-containing regimens (FluCR) were the only factors associated with AUC within target (OR 4.7, 95% CI, 1.1 - 19.8, p=0.04 and OR 9.9, 95% CI, 1.6 - 61.7, p=0.01, respectively). Using other methods for dose calculation, percentage of AUCs within target varied from 16% to 74%. G3 and FluCR were, in some models, associated to AUC within the target and in the toxic range, whereas rapid-metabolizers (G1) were correlated with sub therapeutic AUCs. These associations were confirmed in clearance-prediction analysis, where GSTA1 diplotypes groups and conditioning regimen consistently influenced methods’ most prediction errors. Once GSTA1 status was demonstrated to influence significantly the available Bu dosing algorithms, we aimed to develop a population PK (PPK) model which included GSTA1 genetic variants as a covariate. For that, concentration-time data from 112 children and adolescents receiving IV Bu as a component of the conditioning regimen for 115 stem cell transplantations (autologous and allogenic) performed at CHU Sainte-Justine were analyzed. Non-linear mixed effects analysis was used to build a PPK model. Sex, baseline disease (malignant vs. non-malignant), post-menstrual age (PMA) or chronological age, conditioning regimen and GSTA1 diplotypes groups were evaluated as potential covariates. A one-compartment model with first-order elimination best described the data. A factor of Bu metabolism maturation (Fmat) and theoretical allometric scaling of weight were included in the base model. Covariate analysis revealed PMA (ΔOFV=-26.7, p=2.3x10-7) and GSTA1 diplotypes groups (ΔOFV=-11.7, p=0.003), as significant factors on volume and clearance (CL), respectively. CL of rapid metabolizers (G1) were predicted as being 7% higher and that of poor ones (G3) 12% lower than CL of those defined as normal metabolizers (G2). In conclusion, after evidencing that available Bu dosing methods are not suitable for all GSTA1 diplotypes groups, we have proposed the first pharmacogenomics-based dosing algorithm for Bu to be used in a pediatrics. Its use may contribute considerably to better predict Bu exposure in children and adolescents tailoring the dose according to individual metabolic capacity.

Dans le contexte de la physiologie comparée de la reproduction, les amphibiens sont peu étudiés. Le travail réalisé durant cette thèse visait à analyser des marqueurs de différenciation testiculaire chez l'urodèle Pleurodeles waltl, dont le déterminisme génétique du sexe (ZZ/ZW) peut être influencé par la température. Nos études ont d'abord porté sur le gène sox9 marqueur de la différenciation testiculaire chez les vertébrés supérieurs. Le gène cloné chez le pleurodèle montre une bonne conservation par rapport aux autres vertébrés. Son expression plus élevée dans la gonade mâle n'apparaît que tardivement suggérant qu'il n'est probablement pas impliqué dans les stades précoces de la différenciation testiculaire. En outre, son expression dans le mésonéphros rend difficile son utilisation comme marqueur de différenciation testiculaire. Nous avons ensuite étudié l'Amh, hormone testiculaire impliquée dans la régression des canaux de Müller chez de nombreux vertébrés. Son expression spécifique de la gonade, précocement plus élevée chez les larves ZZ que les ZW, en fait un excellent marqueur de la différenciation testiculaire. Le fait que les pleurodèles mâles voient les canaux de Müller persister malgré la présence d'Amh suggère que la fonction primaire de cette hormone était en relation avec la différenciation gonadique et que la fonction de régression des canaux de Müller n'est apparue que secondairement au cours de l'évolution. Ces marqueurs ont été mis à profit pour caractériser le phénotype gonadique lors d'inversions sexuelles ou lors de développements en absence de cellules germinales. Ils ont permis de montrer que les cellules germinales ne semblent pas jouer de rôle dans la différenciation gonadique du pleurodèle.