RESUMO
BACKGROUND AND OBJECTIVE: Thioguanine (TG), azathioprine (AZA), and mercaptopurine (MP) are thiopurine prodrugs commonly used to treat diseases, such as leukemia and inflammatory bowel disease (IBD). 6-thioguanine nucleotides (6-TGNs) have been commonly used for monitoring treatment. High levels of 6-TGNs in red blood cells (RBCs) have been associated with leukopenia, the cutoff levels that predict this side effect remain uncertain. Thiopurines are metabolized and incorporated into leukocyte DNA. Measuring levels of DNA-incorporated thioguanine (DNA-TG) may be a more suitable method for predicting clinical response and toxicities such as leukopenia. Unfortunately, most methodologies to assay 6-TGNs are unable to identify the impact of NUDT15 variants, effecting mostly ethnic populations (e.g., Chinese, Indian, Malay, Japanese, and Hispanics). DNA-TG tackles this problem by directly measuring thioguanine in the DNA, which can be influenced by both TPMT and NUDT15 variants. While RBC 6-TGN concentrations have traditionally been used to optimize thiopurine therapy due to their ease and affordability of measurement, recent developments in liquid chromatography-tandem mass spectrometry (LC-MS/MS) techniques have made measuring DNA-TG concentrations in lymphocytes accurate, reproducible, and affordable. The objective of this systematic review was to assess the current evidence of DNA-TG levels as marker for thiopurine therapy, especially with regards to NUDT15 variants. METHODS: A systematic review and meta-analysis were performed on the current evidence for DNA-TG as a marker for monitoring thiopurine therapy, including methods for measurement and the illustrative relationship between DNA-TG and various gene variants (such as TPMT, NUDT15, ITPA, NT5C2, and MRP4). PubMed and Embase were systematically searched up to April 2024 for published studies, using the keyword "DNA-TG" with MeSH terms and synonyms. The electronic search strategy was augmented by a manual examination of references cited in articles, recent reviews, editorials, and meta-analyses. A meta-analysis was performed using R studio 4.1.3. to investigate the difference between the coefficients (Fisher's z-transformed correlation coefficient) of DNA-TG and 6-TGNs levels. A meta-analysis was performed using RevMan version 5.4 to investigate the difference in DNA-TG levels between patients with or without leukopenia using randomized effect size model. The risk of bias was assessed using the Newcastle-Ottowa quality assessment scale. RESULTS: In this systematic review, 21 studies were included that measured DNA-TG levels in white blood cells for either patients with ALL (n = 16) or IBD (n = 5). In our meta-analysis, the overall mean difference between patients with leukopenia (ALL + IBD) versus no leukopenia was 134.15 fmol TG/µg DNA [95% confidence interval (CI) (83.78-184.35), P < 0.00001; heterogeneity chi squared of 5.62, I2 of 47%]. There was a significant difference in DNA-TG levels for patients with IBD with and without leukopenia [161.76 fmol TG/µg DNA; 95% CI (126.23-197.29), P < 0.00001; heterogeneity chi squared of 0.20, I2 of 0%]. No significant difference was found in DNA-TG level between patients with ALL with or without leukopenia (57.71 fmol TG/µg DNA [95% CI (- 22.93 to 138.35), P < 0.80]). DNA-TG monitoring was found to be a promising method for predicting relapse rates in patients with ALL, and DNA-TG levels are likely a better predictor for leukopenia in patients with IBD than RBC 6-TGNs levels. DNA-TG levels have been shown to correlate with various gene variants (TPMT, NUDT15, ITPA, and MRP4) in various studies, points to its potential as a more informative marker for guiding thiopurine therapy across diverse genetic backgrounds. CONCLUSIONS: This systematic review strongly supports the further investigation of DNA-TG as a marker for monitoring thiopurine therapy. Its correlation with treatment outcomes, such as relapse-free survival in ALL and the risk of leukopenia in IBD, underscores its role in enhancing personalized treatment approaches. DNA-TG effectively identifies NUDT15 variants and predicts late leukopenia in patients with IBD, regardless of their NUDT15 variant status. The recommended threshold for late leukopenia prediction in patients with IBD with DNA-TG is suggested to be between 320 and 340 fmol/µg DNA. More clinical research on DNA-TG implementation is mandatory to improve patient care and to improve inclusivity in thiopurine treatment.
Assuntos
Monitoramento de Medicamentos , Mercaptopurina , Tioguanina , Humanos , Mercaptopurina/farmacocinética , Mercaptopurina/uso terapêutico , Mercaptopurina/sangue , Tioguanina/farmacocinética , Monitoramento de Medicamentos/métodos , Azatioprina/uso terapêutico , Azatioprina/farmacocinética , DNA/genética , Biomarcadores/sangue , Pirofosfatases/genética , Pirofosfatases/metabolismo , Nucleotídeos de Guanina/sangue , Tionucleotídeos/sangue , Nudix HidrolasesRESUMO
BACKGROUND: In inflammatory bowel disease (IBD), conventional thiopurine users cease treatment in 60% of cases within 5 years, mostly because of adverse events or nonresponse. In this study, the authors aimed to investigate the role of 6-thioguanine nucleotide (TGN) measurements, geno/phenotyping of thiopurine S-methyltransferase (TPMT), and their mutual relationship with TG therapy in IBD. METHODS: An international retrospective, multicenter cohort study was performed at 4 centers in the Netherlands (Máxima Medical Centre) and the United Kingdom (Guy's and St. Thomas' Hospital, Queen Elizabeth Hospital, and East Surrey Hospital). RESULTS: Overall, 526 6-TGN measurements were performed in 316 patients with IBD. The median daily dosage of TG was 20 mg/d (range 10-40 mg/d), and the median duration of TG use was 21.1 months (SD, 28.0). In total, 129 patients (40.8%) had a known TPMT status. In the variant-type and wild-type TPMT genotype metabolism groups, median 6-TGN values were 1126 [interquartile range (IQR) 948-1562] and 467.5 pmol/8 × 10E8 red blood cells (RBCs) (IQR 334-593). A significant difference was observed between the 2 groups (P = 0.0001, t test). For TPMT phenotypes, in the slow, fast, and normal metabolism groups, the median 6-TGN values were 772.0 (IQR 459-1724), 296.0 (IQR 200-705), and 774.5 pmol/8 × 10E8 RBCs (IQR 500.5-981.5), with a significant difference observed between groups (P < 0.001, analysis of variance). CONCLUSIONS: Our findings indicated that TPMT measurements at TG initiation can be useful but are not necessary for daily practice. TPMT genotypes and phenotypes are both associated with significant differences in 6-TGN levels between metabolic groups. However, the advantage of TG remains that RBC 6-TGN measurements are not crucial to monitor treatments in patients with IBD because these measurements did not correlate with laboratory result abnormalities. This presents as a major advantage in countries where patients cannot access these diagnostic tests.
Assuntos
Imunossupressores , Doenças Inflamatórias Intestinais , Metiltransferases , Tioguanina , Adulto , Azatioprina , Feminino , Genótipo , Nucleotídeos de Guanina , Humanos , Imunossupressores/farmacocinética , Doenças Inflamatórias Intestinais/tratamento farmacológico , Doenças Inflamatórias Intestinais/genética , Masculino , Mercaptopurina , Metiltransferases/genética , Pessoa de Meia-Idade , Fenótipo , Estudos Retrospectivos , Tioguanina/farmacocinética , TionucleotídeosRESUMO
INTRODUCTION: Thiopurine methyltransferase (TPMT) catalyzes the S-methylation of thiopurines (mercaptopurine (MP) and tioguanine (TG)), chemotherapeutic agents used in the treatment of acute lymphoblastic leukemia (ALL). Polymorphisms in TPMT gene encode diminished activity enzyme, enhancing accumulation of active metabolites, and partially explaining the inter-individual differences in patients' clinical response. AREAS COVERED: This review gives an overview on TPMT gene and function, and discusses the pharmacogenomic implications of TPMT variants in the prevention of severe thiopurine-induced hematological toxicities and the less known implication on TG-induced sinusoidal obstruction syndrome. Additional genetic and non-genetic factors impairing TPMT activity are considered. Literature search was done in PubMed for English articles published since1990, and on PharmGKB. EXPERT OPINION: To titrate thiopurines safely and effectively, achieve the right degree of lymphotoxic effect and avoid excessive myelosuppression, the optimal management will combine a preemptive TPMT genotyping to establish a safe initial dose with a close phenotypic monitoring of TPMT activity and/or of active metabolites during long-term treatment. Compared to current ALL protocols, replacement of TG by MP during reinduction phase in TPMT heterozygotes and novel individualized TG regimens in maintenance for TPMT wild-type subjects could be investigated to improve outcomes while avoiding risk of severe hepatotoxicity.
Assuntos
Antimetabólitos Antineoplásicos/administração & dosagem , Metiltransferases/genética , Leucemia-Linfoma Linfoblástico de Células Precursoras/tratamento farmacológico , Animais , Antimetabólitos Antineoplásicos/efeitos adversos , Antimetabólitos Antineoplásicos/farmacocinética , Genótipo , Humanos , Mercaptopurina/administração & dosagem , Mercaptopurina/efeitos adversos , Mercaptopurina/farmacocinética , Metiltransferases/metabolismo , Terapia de Alvo Molecular , Polimorfismo Genético , Leucemia-Linfoma Linfoblástico de Células Precursoras/enzimologia , Tioguanina/administração & dosagem , Tioguanina/efeitos adversos , Tioguanina/farmacocinéticaRESUMO
INTRODUCTION: Despite new treatment options for inflammatory bowel disease (IBD), conventional thiopurines remain a common treatment option for maintaining remission, particularly in non-Westernized countries. Therapeutic drug monitoring (TDM) is advised in standard care for optimizing therapy strategies to improve effectiveness, reveal nonadherence, and reduce toxicity. Still, the rationale of TDM is debated. AREAS COVERED: Key insights on TDM of thiopurine metabolites are discussed. The pharmacology of thiopurines is described, emphasizing the interindividual differences in pharmacogenetics, pharmacokinetics, and pharmacodynamics. Pharmacological differences between conventional thiopurines and tioguanine are outlined. Finally, several optimization strategies for thiopurine therapy in IBD are discussed. EXPERT OPINION: TDM has been a useful, but limited, tool to individualize thiopurine therapy. Pharmacokinetic data on the active thiopurine metabolites, derived from measurements in erythrocytes, associated with clinical response only partially predict effectiveness and toxicity. An additional pharmacodynamic marker, such as Rac1/pSTAT3 expression in leukocytes, may improve applicability of TDM in the future.
Assuntos
Monitoramento de Medicamentos , Doenças Inflamatórias Intestinais , Azatioprina/efeitos adversos , Azatioprina/farmacocinética , Humanos , Doenças Inflamatórias Intestinais/tratamento farmacológico , Mercaptopurina/efeitos adversos , Tioguanina/farmacocinéticaRESUMO
BACKGROUND: The utility of measuring thiopurine metabolites (TM) to individualize therapy in autoimmune hepatitis (AIH) has not been defined, and the evidence regarding its use in clinical practice is heterogeneous. This systematic review and meta-analysis aimed to compare the mean concentration of TM between patients in biochemical remission and those not in remission. METHODS: A systematic literature search was conducted using PubMed, Scopus, the Cochrane Library, and Google Scholar for keywords related to TM and AIH. Two reviewers independently searched and selected studies comparing the levels of 6-methyl mercaptopurine (6-MMP) and 6-thioguanine nucleotide (6-TGN) and their ratio in cases of AIH in remission and otherwise. Meta-analysis was performed by calculating the weighted mean difference using the inverse variance heterogeneity model. RESULTS: A total of 1066 records were identified through systematic search; of which, 7 (n = 3 pediatric, n = 4 adults) were considered for inclusion, and 442 TM measurements (n = 128 in children) were analyzed. Mean 6-TGN levels were significantly higher among patients in remission than in those who were not, with a pooled weighted mean difference (WMD) of 15.67 [95% confidence interval (CI), 6.68-24.66] pmol/8 × 108 red blood cells (RBC). The difference was higher in the pediatric age group (WMD, 56.11; 95% CI, 13.60-98.62) than in adults (WMD, 13.77; 95% CI, 4.58-22.97). There was no significant difference in the 6-MMP levels (WMD, -431.7; 95% CI, -1237.4 to 373.9 pmol/8 × 108 RBC; I2 = 82%; n = 3 studies) or 6-MMP/6-TGN ratio among the patients who were in biochemical remission and those who were not (WMD, -0.97; 95% CI, -5.77 to 3.84; I2 = 82%; n = 3 studies). CONCLUSIONS: This meta-analysis suggests a link between 6-TGN levels and biochemical remission in AIH. Further high-quality studies are required to determine the therapeutic cutoff of 6-TGN.
Assuntos
Hepatite Autoimune , Tioguanina , Adulto , Azatioprina/farmacocinética , Azatioprina/uso terapêutico , Criança , Hepatite Autoimune/tratamento farmacológico , Humanos , Imunossupressores/farmacocinética , Imunossupressores/uso terapêutico , Mercaptopurina/farmacocinética , Tioguanina/farmacocinéticaRESUMO
Introduction: In the 1950s, thioguanine (TG), a thiopurine-derivative together with azathioprine (AZA) and mercaptopurine (MP), were developed for the treatment of childhood leukemia. Over the years, the use of TG was also explored for other, mainly immune-mediated and inflammatory, diseases such as in the field of dermatology and rheumatology (e.g. psoriasis, systemic lupus erythematosus (SLE)) and gastroenterology and hepatology (e.g. inflammatory bowel diseases (IBD), autoimmune hepatitis).Areas covered: This review provides a comprehensive overview of all the clinical uses of TG and describes its mechanism of action, pharmacokinetic/pharmacodynamic features, and toxicity.Expert opinion: Thioguanine has shown beneficial clinical effects in hematological (particularly leukemia) and several immune-inflammatory diseases including psoriasis, SLE, polycythemia vera, Churg-Strauss syndrome, IBD, collagenous sprue, refractory celiac disease, and autoimmune hepatitis. Thioguanine is not effective in treating solid-cancers. At relatively low dosages, i.e. 0.2- 0.3mg/kg/day or 20 mg/day, TG has a favorable risk-benefit ratio and is a safe and effective drug in the long-term treatment of amongst other IBD patients. Thioguanine toxicity, especially myelotoxicity, and hepatotoxicity, including nodular regenerative hyperplasia (NRH) of the liver, is limited when dosed adequately. The occurrence of NRH appears dose-dependent and has been especially described during high dose TG above 40 mg/day.
Assuntos
Antimetabólitos Antineoplásicos/administração & dosagem , Tioguanina/administração & dosagem , Antimetabólitos Antineoplásicos/efeitos adversos , Antimetabólitos Antineoplásicos/farmacocinética , Relação Dose-Resposta a Droga , Humanos , Leucemia/tratamento farmacológico , Tioguanina/efeitos adversos , Tioguanina/farmacocinéticaRESUMO
INTRODUCTION AND OBJECTIVES: Thiopurines are drugs widely used in patients for the maintenance of remission in inflammatory bowel disease. The optimal plasma levels are known, but there is controversy about whether the need for other drugs is reduced or is cost-effective. The aim of this study is to describe the use of the optimised treatment with thiopurines in paediatric patients with inflammatory bowel disease followed up in this Unit since the introduction of determining the drug levels. MATERIAL AND METHODS: A descriptive retrospective study was conducted in which the plasma values of 6-thioguanine (6-TGN), 6-methyl-mercapto-purine (6-MMP), and their ratios were analysed using liquid chromatography. Other variables were collected, such as clinical status, analytical and demographic variables of patients with inflammatory bowel disease followed up in this Unit. RESULTS: A total of 72 patients were included, and 149 determinations of metabolites were performed. The 6-TGN levels were found to below the therapeutic range in 61.5% of patients (in 7 cases due to lack of adherence to therapy), and 6-MMP was in the toxicity range in 7.4%. After the determination of 77 specimens, some action was taken, such as modifying the dose, change of formula, or withdrawing the drug. Only 9 patients were scaled to a biological drug (13.4% of the total on single therapy). No association was found between the activity of the disease and the thiopurine levels. CONCLUSIONS: In our experience, the monitoring of thiopurine levels helped to modify the drug dose that the patient received, adjusting their therapeutic levels, and potentially avoiding the addition of new drugs.
Assuntos
Colite Ulcerativa/tratamento farmacológico , Doença de Crohn/tratamento farmacológico , Imunossupressores/farmacocinética , Mercaptopurina/análogos & derivados , Tioguanina/farmacocinética , Adolescente , Criança , Pré-Escolar , Cromatografia Líquida , Colite Ulcerativa/sangue , Colite Ulcerativa/diagnóstico , Doença de Crohn/sangue , Doença de Crohn/diagnóstico , Relação Dose-Resposta a Droga , Monitoramento de Medicamentos , Feminino , Humanos , Imunossupressores/sangue , Imunossupressores/uso terapêutico , Lactente , Recém-Nascido , Masculino , Mercaptopurina/sangue , Mercaptopurina/farmacocinética , Mercaptopurina/uso terapêutico , Estudos Retrospectivos , Tioguanina/sangue , Tioguanina/uso terapêutico , Resultado do TratamentoRESUMO
BACKGROUND: Concentrations of 6-thioguanine (6TG) nucleotides and 6-methylmercaptopurine (6MMP) nucleotides in RBCs were measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS). This assay was validated for clinical use and was applied to blood samples from patients taking mercaptopurine (6MP). METHODS: RBCs were hemolyzed and deproteinized using perchloric acid, followed by heating for the hydrolysis of nucleotides, and the resultant base was measured using LC-MS/MS. Precision, recovery, linearity, matrix effect, and limit of quantification was validated for clinical application. Our results were compared with another institution's established LC-MS/MS assay. We measured the concentrations of 6TG and 6MMP in RBCs of pediatric patients with acute lymphoblastic leukemia (ALL), and the clinical impact of those metabolites was investigated. RESULTS: The imprecision coefficient of variations of 6TG and 6MMP were 5.7%-8.1%, and the bias was within 5%. Lower limits of quantification were set at 54 ng/mL for 6TG and 1036 ng/mL for 6MMP. Correlation coefficients for 6TG and 6MMP were 0.997 and 1.0 in a comparison study. For clinical proof-of-concept, 74 blood samples were collected from 37 pediatric ALL patients receiving maintenance therapy. Concentration of 6TG ranged from 16.1 to 880 pmol/8 × 10 RBCs and that of 6MMP from 55 to 20,937 pmol/8 × 10 RBCs. The 6MP metabolites were not correlated with WBC or absolute neutrophil count. On the other hand, the higher 6MMP level was associated with elevated alanine aminotransferase and aspartate aminotransferase. CONCLUSIONS: In this study, an assay for the quantification of 6TG and 6MMP in RBCs was established and applied to pediatric ALL patients. Interindividual variability in 6MP metabolite concentrations was considerable and associated with elevation of liver enzymes, which may be useful in the clinical monitoring of 6MP maintenance therapy in pediatric ALL patients.
Assuntos
Antimetabólitos Antineoplásicos/farmacocinética , Eritrócitos/efeitos dos fármacos , Nucleotídeos/metabolismo , Leucemia-Linfoma Linfoblástico de Células Precursoras/tratamento farmacológico , Leucemia-Linfoma Linfoblástico de Células Precursoras/metabolismo , Tioguanina/farmacocinética , Tioguanina/uso terapêutico , Adolescente , Antimetabólitos Antineoplásicos/sangue , Antimetabólitos Antineoplásicos/uso terapêutico , Criança , Pré-Escolar , Cromatografia Líquida/métodos , Eritrócitos/metabolismo , Feminino , Humanos , Masculino , Mercaptopurina/análogos & derivados , Mercaptopurina/sangue , Mercaptopurina/metabolismo , Nucleotídeos/sangue , Nucleotídeos/uso terapêutico , Leucemia-Linfoma Linfoblástico de Células Precursoras/sangue , Espectrometria de Massas em Tandem/métodos , Tioguanina/sangueRESUMO
Thiopurine methyltransferase (TPMT) activity exhibits a monogenic codominant inheritance and catabolizes thiopurines. TPMT variant alleles are associated with low enzyme activity and pronounced pharmacologic effects of thiopurines. Loss-of-function alleles in the NUDT15 gene are common in Asians and Hispanics and reduce the degradation of active thiopurine nucleotide metabolites, also predisposing to myelosuppression. We provide recommendations for adjusting starting doses of azathioprine, mercaptopurine, and thioguanine based on TPMT and NUDT15 genotypes (updates on www.cpicpgx.org).
Assuntos
Antimetabólitos Antineoplásicos , Azatioprina , Mercaptopurina , Metiltransferases/genética , Pirofosfatases/genética , Tioguanina , Antimetabólitos Antineoplásicos/administração & dosagem , Antimetabólitos Antineoplásicos/farmacocinética , Azatioprina/administração & dosagem , Azatioprina/farmacocinética , Relação Dose-Resposta a Droga , Cálculos da Dosagem de Medicamento , Humanos , Inativação Metabólica/genética , Mercaptopurina/administração & dosagem , Mercaptopurina/farmacocinética , Farmacogenética , Testes Farmacogenômicos , Tioguanina/administração & dosagem , Tioguanina/farmacocinéticaRESUMO
Thiopurines (TP) represent an important therapeutic tool for the treatment of inflammatory bowel diseases (IBD) in the current situation of rising incidence and health care costs. The results of multiple clinical studies aimed at finding correlations between levels of TP metabolites and response of IBD patients to the treatment are, however, often controversial due to variability in analytical and sample preparation procedures among these studies. In this work, therefore, an updated analytical and sample preparation procedure for therapeutic drug monitoring (TDM) of TP metabolites in blood samples obtained from patients with IBD was proposed to establish a unified protocol. An advanced analytical method based on ion-exchange liquid chromatography hyphenated with tandem mass spectrometry (IEC-ESI-MS/MS) was used for the determination of the profiles of 12 individual TP metabolites in the particular steps of sample preparation procedure including blood collection, red blood cells (RBC) isolation, lysis, and storage. Favorable performance parameters of the IEC-ESI-MS/MS method (LLOQs 1â»10 nmol/L, accuracy 95â»105%, intra-day and inter-day precision < 10%, selectivity demonstrated via no sample matrix interferences) and acceptable stability (peak area fluctuations < 15%) of clinical samples under the proposed sample preparation conditions {(i) EDTA anticoagulant tube for the blood collection; (ii) 4 °C and 4 h between the sample collection and RBC isolation; (iii) phosphate-buffered saline for RBC washing and re-suspendation; (iv) -20 °C for RBC lysis and short-term storage; (v) 50 mmol/L phosphate buffer, pH 7.4, 10 mmol/L DTT as a stabilizing medium for TPN in RBC lysates} demonstrated the suitability of such protocol for a well-defined and reliable routine use in studies on thiopurines TDM.
Assuntos
Azatioprina , Monitoramento de Medicamentos/métodos , Doenças Inflamatórias Intestinais/sangue , Doenças Inflamatórias Intestinais/tratamento farmacológico , Mercaptopurina , Tioguanina , Adulto , Azatioprina/administração & dosagem , Azatioprina/farmacocinética , Eritrócitos/metabolismo , Feminino , Humanos , Masculino , Mercaptopurina/administração & dosagem , Mercaptopurina/farmacocinética , Pessoa de Meia-Idade , Tioguanina/administração & dosagem , Tioguanina/farmacocinéticaRESUMO
Ubiquitin-specific protease 2 (USP2) belongs to the family of deubiquitinases that can rescue protein targets from proteasomal degradation by reversing their ubiquitination. In various cancers, including prostate cancer and ovarian carcinoma, upregulation of USP2 leads to an increase in the levels of deubiquitinated substrates such as fatty acid synthase, MDM2, cyclin D1 and Aurora-A. USP2 thus plays a critical role in tumor cells' survival and therefore represents a therapeutic target. Here a leukemia drug, 6-thioguanine, was found to be a potent inhibitor of USP2. Enzyme-kinetic and X-ray crystallographic data suggest that 6-thioguanine displays a noncompetitive and slow-binding inhibitory mechanism against USP2. Our study provides a clear rationale for the clinical evaluation of 6-thioguanine for USP2-upregulated cancers.
Assuntos
Endopeptidases/metabolismo , Tioguanina/farmacologia , Cristalografia por Raios X/métodos , Enzimas Desubiquitinantes/antagonistas & inibidores , Enzimas Desubiquitinantes/metabolismo , Humanos , Cinética , Processamento de Proteína Pós-Traducional , Tioguanina/metabolismo , Tioguanina/farmacocinética , Ubiquitina Tiolesterase , Ubiquitinação/fisiologiaRESUMO
The use of thiopurines in the treatment of inflammatory bowel disease (IBD) can be optimized by the application of therapeutic drug monitoring. In this procedure, 6-thioguanine nucleotides (6-TGN) and 6-methylmercaptopurine (6-MMP) metabolites are monitored and related to therapeutic response and adverse events, respectively. Therapeutic drug monitoring of thiopurines, however, is hampered by several analytical limitations resulting in an impaired translation of metabolite levels to clinical outcome in IBD. Thiopurine metabolism is cell specific and requires nucleated cells and particular enzymes for 6-TGN formation. In the current therapeutic drug monitoring, metabolite levels are assessed in erythrocytes, whereas leukocytes are considered the main target cells of these drugs. Furthermore, currently used methods do not distinguish between active nucleotides and their unwanted residual products. Last, there is a lack of a standardized laboratorial procedure for metabolite assessment regarding the substantial instability of erythrocyte 6-TGN. To improve thiopurine therapy in patients with IBD, it is necessary to understand these limitations and recognize the general misconceptions in this procedure.
Assuntos
Azatioprina/sangue , Monitoramento de Medicamentos/métodos , Doenças Inflamatórias Intestinais/tratamento farmacológico , Mercaptopurina/sangue , Tioguanina/sangue , Antimetabólitos/sangue , Antimetabólitos/farmacocinética , Antimetabólitos/uso terapêutico , Azatioprina/farmacocinética , Azatioprina/uso terapêutico , Humanos , Mercaptopurina/farmacocinética , Mercaptopurina/uso terapêutico , Tioguanina/farmacocinética , Tioguanina/uso terapêuticoRESUMO
Methotrexate/6-mercaptopurine maintenance therapy of childhood acute lymphoblastic leukemia is challenged by treatment-related hepatotoxicity, failure to achieve the myelosuppressive target, and lack of direct parameters for monitoring treatment efficacy or even intensity. Patients with low thiopurine methyltransferase (TPMT) activity have lower levels of hepatotoxic methylated thiopurine metabolites (MeMPs), higher levels of thioguanine nucleotides (TGNs), and reduced relapse rates. Addition of 6-thioguanine to maintenance therapy of a child with ALL and high TPMT activity increased the TGN/MeMP index in erythrocytes 5.5-fold, mimicking the more favorable thiopurine metabolism seen in patients with low TPMT activity.
Assuntos
Antimetabólitos Antineoplásicos/farmacocinética , Mercaptopurina/farmacocinética , Recidiva Local de Neoplasia/prevenção & controle , Leucemia-Linfoma Linfoblástico de Células Precursoras/tratamento farmacológico , Tioguanina/farmacocinética , Antimetabólitos Antineoplásicos/administração & dosagem , Criança , Eritrócitos/efeitos dos fármacos , Eritrócitos/metabolismo , Feminino , Humanos , Mercaptopurina/administração & dosagem , Metiltransferases/metabolismo , Leucemia-Linfoma Linfoblástico de Células Precursoras/metabolismo , Prognóstico , Indução de Remissão , Tioguanina/administração & dosagemRESUMO
The activity of the enzyme thiopurine methyltransferase (TPMT) is regulated by a common genetic polymorphism. One in 300 individuals lack enzyme activity and 11% are heterozygous for a variant low activity allele and have an intermediate activity. The thiopurine drugs azathioprine, mercaptopurine and thioguanine are substrates for TPMT; these drugs exhibit well documented myelosuppressive effects on haematopoietic cells and have a track record of idiosyncratic drug reactions. The development of severe bone marrow toxicity, in patients taking standard doses of thiopurine drugs, is associated with TPMT deficiency whilst the TPMT heterozygote is at an increased risk of developing myelosuppression. Factors influencing TPMT enzyme activity, as measured in the surrogate red blood cell, are discussed in this review to enable an appreciation of why concordance between TPMT genotype and phenotype is not 100%. This is particularly important for lower/intermediate TPMT activities to avoid misclassification of TPMT status. TPMT testing is now widely available in routine service laboratories. The British National Formulary suggests TPMT testing before starting thiopurine drugs. Dermatologists were quick to adopt routine TPMT testing whilst gastroenterologists do not specifically recommend TPMT screening. TPMT testing is mandatory prior to the use of mercaptopurine in childhood leukaemia. Thiopurine drug dose and other treatment related influences on cell counts explain some of the differing recommendations between clinical specialities. TPMT testing is cost-effective and the major role is in the identification of the TPMT deficient individual prior to the start of thiopurine drugs.
Assuntos
Antimetabólitos Antineoplásicos/efeitos adversos , Hipersensibilidade a Drogas/diagnóstico , Testes Genéticos/economia , Metiltransferases/genética , Erros Inatos do Metabolismo da Purina-Pirimidina/diagnóstico , Tioguanina/efeitos adversos , Antimetabólitos Antineoplásicos/farmacocinética , Azatioprina/efeitos adversos , Azatioprina/farmacocinética , Análise Custo-Benefício/economia , Rotulagem de Medicamentos/normas , Genótipo , Humanos , Mercaptopurina/efeitos adversos , Mercaptopurina/farmacocinética , Metiltransferases/metabolismo , Fenótipo , Tioguanina/farmacocinéticaRESUMO
BACKGROUND: Ten percent of patients with autoimmune hepatitis (AIH) are nonresponsive or intolerant to thiopurine therapy. A skewed metabolism, leading to the preferential generation of (hepato)toxic thiopurine metabolites (6-MMPs) instead of the metabolic active 6-tioguanine (thioguanine) nucleotides (6-TGNs), may explain this unfavourable outcome. Co-administration of allopurinol to low-dose thiopurine therapy may effectively revert this deviant metabolism, as has been shown in inflammatory bowel disease. AIM: To describe the effect of adding allopurinol to low-dose thiopurine therapy in patients with AIH with intolerance or nonresponse to normal thiopurine dosages due to a skewed metabolism. METHODS: We describe the clinical efficacy and tolerability of allopurinol-thiopurine combination therapy with allopurinol 100 mg and low-dose thiopurine (25-33% of the original dosage) in eight AIH patients with a skewed thiopurine metabolism. Patients were switched because of dose-limiting intolerance (n = 3), nonresponse (n = 3) or loss of response (n = 2) to conventional thiopurine treatment. RESULTS: All eight patients showed biochemical improvement with a reduction in median alanine aminotransferase (ALT) levels of 62 U/L at start to 35 U/L at 1 month (P = 0.03). This clinical benefit was sustained in seven patients. Allopurinol-thiopurine combination therapy effectively bypassed thiopurine side effects in four of five patients. Median 6-tioguanine nucleotides levels increased from 100 to 200 pmol/8 × 10(8) red blood cells (RBC) at 3 months (P = 0.04). Median 6-MMP levels decreased in all patients from 6090 to 175 pmol/8 × 10(8) RBC (P = 0.01). CONCLUSION: Allopurinol safely and effectively optimises thiopurine therapy in patients with autoimmune hepatitis with intolerance and/or nonresponse due to an unfavourable thiopurine metabolism.
Assuntos
Alopurinol/uso terapêutico , Antimetabólitos/uso terapêutico , Hepatite Autoimune/tratamento farmacológico , Mercaptopurina/análogos & derivados , Adulto , Idoso , Alanina Transaminase/metabolismo , Interações Medicamentosas , Quimioterapia Combinada , Feminino , Hepatite Autoimune/sangue , Humanos , Masculino , Mercaptopurina/farmacocinética , Mercaptopurina/uso terapêutico , Metiltransferases/metabolismo , Pessoa de Meia-Idade , Terapia de Salvação , Tioguanina/farmacocinéticaRESUMO
A high-performance liquid chromatography method capable of measuring thiopurine mono-, di-, and triphosphates separately in red blood cells (RBCs) was developed. RBCs were isolated from whole blood using centrifugation. Proteins were precipitated using dichloromethane and methanol. The thioguanine nucleotides (TGNs) were derivatised using potassium permanganate before analysis. Analytes were separated by ion-pairing liquid chromatography using tetrabutylammonium ions and detected using UV absorption and fluorescence. The method was designed for use in clinical trials. Ten patient samples were analysed to demonstrate clinical application and to establish pilot ranges for all analytes. The method measured thioguanosine mono-(TGMP), di-(TGDP), and triphosphate (TGTP), as well as methylthioinosine mono- (meTIMP), di- (meTIDP) and triphosphate (meTITP) in RBCs collected from patients treated with thiopurine drugs (azathioprine, 6-mercaptopurine, and 6-thioguanine). LOQ was 0.3, 3, 2, 30, 30 and 40 pmol/8 × 108 RBC, for TGMP, TGDP, TGTP, meTIMP, meTIDP and meTITP, respectively. Between-day precision were below 14% for all analytes at all concentrations and samples were stable at 4 °C for 8 h after sampling.
Assuntos
Antimetabólitos Antineoplásicos/farmacocinética , Monitoramento de Medicamentos/métodos , Eritrócitos/química , Inibidores da Síntese de Ácido Nucleico/farmacocinética , Purinas/sangue , Tionucleotídeos/sangue , Adulto , Métodos Analíticos de Preparação de Amostras , Antimetabólitos Antineoplásicos/sangue , Antimetabólitos Antineoplásicos/uso terapêutico , Azatioprina/sangue , Azatioprina/farmacocinética , Azatioprina/uso terapêutico , Biotransformação , Cromatografia Líquida de Alta Pressão , Eritrócitos/metabolismo , Feminino , Humanos , Indicadores e Reagentes/química , Masculino , Mercaptopurina/sangue , Mercaptopurina/farmacocinética , Mercaptopurina/uso terapêutico , Inibidores da Síntese de Ácido Nucleico/sangue , Inibidores da Síntese de Ácido Nucleico/uso terapêutico , Projetos Piloto , Permanganato de Potássio/química , Leucemia-Linfoma Linfoblástico de Células Precursoras/sangue , Leucemia-Linfoma Linfoblástico de Células Precursoras/tratamento farmacológico , Purinas/metabolismo , Compostos de Amônio Quaternário/química , Tioguanina/sangue , Tioguanina/farmacocinética , Tioguanina/uso terapêutico , Tionucleotídeos/metabolismoRESUMO
Therapeutic drug monitoring (TDM) of major metabolites of thiopurine drugs is a widely used tool for assessing treatment efficacy and toxicity in patients with inflammatory bowel disease (IBD). We report the laboratory and clinical validation of a simple and reliable high performance liquid chromatography (HPLC) method for the measurement of 6-thioguanine nucleotides (6-TGN) and 6-methylmercaptopurine (6-MMP) on paediatric patients with IBD. The aim of this paper is to develop and validate a method for the measurement of 6-TGN and 6-MMP applicable to routine practice and to evaluate the usefulness of the TDM of thiopurine drugs in children with IBD attending our Gastroenterology Unit. The HPLC method was validated following international guidelines starting from red blood cells (RBC) and whole blood (WB). A comparison between RBC and WB was assessed. The usefulness of TDM was then evaluated using the new method from WB in 47 paediatric patients with IBD treated with thiopurine drugs. WB and RBC resulted in interchangeable matrices. The majority of patients had the metabolite levels inside the therapeutic ranges. A moderate correlation was found between 6-MMP concentration and the dose of thiopurines. A higher percentage of non responders was found among patients with lower levels of 6-TGN. Toxicity was found in eight patients and was evaluated in respect to the metabolite concentration. The described HPLC method is applicable to routine practice and it is suitable for its use in multicentric studies. Our results of TDM on paediatric IBD patients can contribute to clarify its role in their therapeutic management.
Assuntos
Anti-Inflamatórios/farmacocinética , Cromatografia Líquida de Alta Pressão , Monitoramento de Medicamentos/métodos , Fármacos Gastrointestinais/farmacocinética , Doenças Inflamatórias Intestinais/tratamento farmacológico , Mercaptopurina/análogos & derivados , Tioguanina/farmacocinética , Adolescente , Fatores Etários , Anti-Inflamatórios/sangue , Anti-Inflamatórios/uso terapêutico , Biotransformação , Criança , Pré-Escolar , Eritrócitos/metabolismo , Feminino , Fármacos Gastrointestinais/sangue , Fármacos Gastrointestinais/uso terapêutico , Humanos , Lactente , Doenças Inflamatórias Intestinais/sangue , Itália , Masculino , Mercaptopurina/sangue , Mercaptopurina/farmacocinética , Mercaptopurina/uso terapêutico , Reprodutibilidade dos Testes , Tioguanina/sangue , Tioguanina/uso terapêuticoRESUMO
BACKGROUND AND PURPOSE: Although 6-mercaptopurine and azathioprine are effective treatments in inflammatory bowel disease (IBD), many patients discontinue treatment because of side effects. 6-Thioguanine (6-TG) may be an alternative rescue therapy in these intolerant patients but the pharmacokinetics of 6-TG are not fully described. Here we have measured the pharmacokinetics of the biotransformation of 6-TG into the pharmacologically active metabolites, 6-thioguanine nucleotides (6-TGN), in IBD patients. EXPERIMENTAL APPROACH: In 12 patients with IBD, levels of 6-TGN and activities of thiopurine S-methyltransferase, xanthine oxidase and hypoxanthine guanine-phosphoribosyl-transferase were measured in a two-stage (i.v. and p.o. administration of 0.3 mg·kg(-1) 6-TG), prospective study. Median exposure of 6-TGN in red blood cells (RBC) was expressed as the ratio of the area under the curve (AUC) per mg 6-TG after i.v. dosing and that after p.o. dosing. KEY RESULTS: The median AUC per mg 6-TG was 1068 (p.o.) and 7184 (i.v.) pmol·h (8 × 10(8) RBC)(-1) . Median exposure of 6-TGN in RBC was 15% (9-28). Hypoxanthine guanine-phosphoribosyl-transferase activity correlated with peak 6-TGN and with AUC per mg (r= 0.7, P= 0.02 and r= 0.6, P= 0.03 respectively). Thiopurine S-methyltransferase activity was inversely related to AUC per mg (r=-0.8, P= 0.001), whereas that of xanthine oxidase was correlated with a lower peak 6-TGN (r=-0.7, P= 0.02). CONCLUSIONS AND IMPLICATIONS: The great variability of the AUC per mg for 6-TG observed after p.o. and i.v. administration of 6-TG, was partly explained by variability in activities of metabolizing enzymes. Exposure of 6-TGN was low in all patients.
Assuntos
Doenças Inflamatórias Intestinais/tratamento farmacológico , Doenças Inflamatórias Intestinais/metabolismo , Tioguanina/farmacocinética , Administração Oral , Adulto , Feminino , Nucleotídeos de Guanina/sangue , Nucleotídeos de Guanina/metabolismo , Humanos , Hipoxantina Fosforribosiltransferase/metabolismo , Doenças Inflamatórias Intestinais/sangue , Infusões Intravenosas , Masculino , Metiltransferases/metabolismo , Pessoa de Meia-Idade , Estudos Prospectivos , Tioguanina/farmacologia , Tionucleotídeos/sangue , Tionucleotídeos/metabolismo , Xantina Oxidase/metabolismo , Adulto JovemRESUMO
Azathioprine, 6-mercaptopurine, and 6-thioguanine are immunosuppressive drugs indicated in the prevention of graft rejection, and treatment of auto-immune disease or inflammatory bowel disease. Their anti-nucleotidic properties are also used for the treatment of acute leukaemia. Their metabolism involves thiopurine methyl transferase, which activity varies according to genetic polymorphisms. In inflammatory bowel disease patients, there is no recommended therapeutic range of intra-erythrocyte 6-thioguanine nucleotide concentration, the active metabolite. Therapeutic drug monitoring of 6-thioguanine nucleotide concentrations is however proposed in the following clinical situations: to check the observance, to try to explain therapeutic failure, to manage patients with limited thiopurine methyl transferase activity or patients treated with associated drugs that can modify thiopurine methyl transferase activity. The literature review shows that high concentrations of 6-thioguanine nucleotides and methylated metabolites are associated with an increased risk of bone marrow toxicity. In addition, high concentrations of methylated metabolite might increase the risk of hepatic toxicity. These major side-effects can be prevented by the use of pre-treatment screening for thiopurine methyl transferase activity or genotype in inflammatory bowel disease patients in order to propose an adapted dosing.
Assuntos
Imunossupressores/uso terapêutico , Doenças Inflamatórias Intestinais/tratamento farmacológico , Tioguanina/uso terapêutico , Azatioprina/uso terapêutico , Relação Dose-Resposta a Droga , Monitoramento de Medicamentos , Humanos , Imunossupressores/farmacocinética , Doenças Inflamatórias Intestinais/patologia , Nucleotídeos/uso terapêutico , Tioguanina/farmacocinéticaRESUMO
6-mercaptopurine, a key drug for the treatment of acute lymphoblastic leukaemia in children, is a prodrug metabolized into 6-thioguanine (6-TGN) which are the active compounds and into methylated metabolites, primary by thiopurine S-methyltransferase enzyme (TPMT). This enzyme displays important inter subject variability linked to a genetic polymorphism: when treated with standard doses of thiopurine, TPMT-deficient and heterozygous patients are at great risk for developing severe and potentially life-threatening toxicity (hematopoietic, hepatic, mucositis...) but show a better survival rate while patients with high TPMT activity (wild type) present lower peripheral red blood cells 6-TGN concentrations and a higher risk of leukemia relapse. Genotyping remains crucial before 6-MP administration at diagnosis to identify patients with homozygous mutant TPMT genotype and therefore prevent severe and life-threatening toxicity, and to individualize therapy according to TMPT genotype. Follow-up of ALL treatment should preferentially be based on repeated determinations of intracellular active metabolites (6-thioguanine nucleotides) and methylated metabolites in addition to haematological surveillance.