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No association between relapse hazard and thiopurine methyltransferase geno- or phenotypes in non-high risk acute lymphoblastic leukemia: a NOPHO ALL2008 sub-study. Cancer Chemother Pharmacol 2021; 88:271-279. [PMID: 33928426 DOI: 10.1007/s00280-021-04281-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Accepted: 04/14/2021] [Indexed: 10/21/2022]
Abstract
PURPOSE 6-mercaptopurine(6MP)/methotrexate maintenance therapy is essential to reduce relapse of childhood acute lymphoblastic leukemia (ALL). Common germline variants in TPMT cause low activity of thiopurine methyltransferase (TPMT) and higher 6MP metabolite (TGN) levels. Higher levels of TGNs incorporated into DNA (DNA-TG) and low TPMT activity have previously been associated with a lower relapse risk. We explored if TPMT geno- or phenotype was associated with DNA-TG levels and relapse rate in NOPHO ALL2008. METHODS TPMT genotype, repeated phenotyping, and DNA-TG measurements were collected in 918 children with non-high risk ALL (NOPHO ALL2008 maintenance therapy study). Maintenance therapy started with 6MP at 50 and 75 mg/m2 for TPMT heterozygous and wildtype patients and was adjusted to a target WBC of 1.5 - 3.0 × 109/L. RESULTS Of 918 patients, 78 (8.5%) were TPMT heterozygous and 903 had at least one TPMT measurement (total 3063). Mean TPMT activities were higher with wildtype than heterozygous TPMT (N = 752, 16.6 versus 9.6 U/mL ery., p < 0.001). The 5-year cumulative incidence of relapse was 6.4% and 6.0% for TPMT heterozygous and wildtype patients, and there was no association between genotype and relapse rate (N = 918, hazard ratio = 1.01, 95% confidence interval [CI] 0.40 - 2.54, p = 0.98). Although TPMT heterozygous patients had higher DNA-TG (N = 548, median 760.9 [interquartile range (IQR) 568.7 - 890.3] versus 492.7 [IQR 382.1 - 634.6] fmol/µg, p < 0.001), TPMT activity was not associated with relapse rate (N = 813; hazard ratio = 0.98 per one U/mL ery. increase in TPMT activity, 95% CI 0.91 - 1.06, p = 0.67). CONCLUSION TPMT geno- and phenotype were not associated with relapse in non-high risk NOPHO ALL2008.
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Role of Thiopurines in Pediatric Inflammatory Bowel Diseases: A Real-Life Prospective Cohort Study. J Pediatr Gastroenterol Nutr 2020; 70:825-832. [PMID: 32443042 DOI: 10.1097/mpg.0000000000002566] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
OBJECTIVES Use of thiopurines for inflammatory bowel diseases (IBDs) is declining in some parts of the world. We aimed to explore outcomes of thiopurines and predictors of response in a real-world prospective cohort of children with dose optimization. METHODS Children with IBD treated with thiopurines without biologics were enrolled. Dosing was guided by thiopurine S-methyltransferase-activity at baseline and by clinical response and toxicity at 4 months; 1 year into the study, therapeutic drug monitoring at 4 months was also considered in the decision making. The primary outcome was steroid-free remission without treatment escalation by 12 months (SFR), using the intention-to-treat approach. RESULTS A total of 129 children were included (74% Crohn disease [CD] and 26% ulcerative colitis [UC]). SFR was achieved in 37 (39%) CD and 13 (39%) UC patients, and SFR with normal erythrocyte sedimentation rate/C-reactive protein in 20 (21%) and 9 (27%), respectively. At 4 months, mean corpuscular volume/white blood cell ratio and Δ absolute neutrophil count weakly correlated with 6-thioguanine (r = 0.33, P = 0.02 and r = 0.32, P = 0.02, respectively). In CD, SFR was associated with 4-month median weighted Pediatric Crohn Disease Activity Index (2.5 [IQR 0-7.5] in responders vs 5 in nonresponders [0-12.5], P = 0.048) and Δabsolute neutrophil count (1.7 [IQR 0.7-4.1] vs 0.05 [-2.3-0.9]; P = 0.03). Mild drug-related adverse events were recorded in 30 children (22%), 3 required stopping the drug. CONCLUSIONS In this real-life prospective cohort using dose optimization, thiopurines were safe and effective in 21% of CD and 27% of UC patients, including normalization of C-reactive protein and erythrocyte sedimentation rate. Thiopurines remain a viable option in the treatment algorithm of mild-moderate pediatric IBD, especially in girls whose risk for lymphoma is lower.
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Illamola SM, Echaabi AK, Mazeron C, Deshayes S, Loriot MA, Pallet N. Development and validation of a UPLC-UV method for the quantification of thiopurine methyltransferase enzyme activity in human erythrocytes. J Chromatogr B Analyt Technol Biomed Life Sci 2019; 1113:91-97. [PMID: 30901734 DOI: 10.1016/j.jchromb.2019.03.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Revised: 02/13/2019] [Accepted: 03/13/2019] [Indexed: 01/07/2023]
Abstract
Thiopurines are drugs widely used for the treatment of autoimmune conditions, inflammatory bowel disease or acute lymphoblastic leukemia. Determination of thiopurine methyltransferase activity (TPMT), a major determinant of thiopurines toxicity, has been suggested before implementing thiopurine treatment. An ultraperformance liquid chromatography (UPLC) method was developed and validated for the quantification of TPMT enzyme activity based on the conversion of 6-mercaptopurine (6-MP) to 6-methylmercaptopurine (6-MMP) using S-adenosyl-L-methionine (SAM) as methyl donor in red blood cell lysates (RBC). This method was improved from a previous laborious high performance liquid chromatography (HPLC) method, using a lower volume of injection and with a shorter runtime. After incubation and protein precipitation 6-MMP was separated on a HSS-T3 (2.1 × 50 mm, 1.8 μm) column and monitored by UV detection (290 nm). A change on the organic solvent used to dissolve 6-MP resulted in a reduction of interference by endogenous or non-enzymatic methylated 6-MMP. A full validation of the 6-MMP assay was performed according to the FDA and EMA guidelines. The method was linear from 0.125 to 2 nmol/mL, with acceptable values of accuracy and precision. The method was applied in 106 patients treated with thiopurines whose TPMT activity was previously quantified by HPLC. Evaluation through Bland-Altman plot showed that TPMT activities were in agreement between both methods.
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Affiliation(s)
- S M Illamola
- Service de Biochimie, Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris, Paris, France.
| | - A K Echaabi
- Service de Biochimie, Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris, Paris, France
| | - C Mazeron
- Service de Biochimie, Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris, Paris, France
| | - S Deshayes
- Service de Biochimie, Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris, Paris, France
| | - M A Loriot
- Service de Biochimie, Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris, Paris, France; INSERM U1147, Centre Universitaire des Saints Pères, Paris, France; Université Paris Descartes, Paris, France
| | - N Pallet
- Service de Biochimie, Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris, Paris, France; INSERM U1147, Centre Universitaire des Saints Pères, Paris, France; Université Paris Descartes, Paris, France; Service de Néphrologie, Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris, Paris, France
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4
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Rucci F, Cigoli MS, Marini V, Fucile C, Mattioli F, Robbiano L, Cavallari U, Scaglione F, Perno CF, Penco S, Marocchi A. Combined evaluation of genotype and phenotype of thiopurine S-methyltransferase (TPMT) in the clinical management of patients in chronic therapy with azathioprine. Drug Metab Pers Ther 2019; 34:dmpt-2018-0037. [PMID: 30840585 DOI: 10.1515/dmpt-2018-0037] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 01/29/2019] [Indexed: 06/09/2023]
Abstract
Background The thiopurine S-methyltransferase (TPMT)/azathioprine (AZA) gene-drug pair is one of the most well-known pharmacogenetic markers. Despite this, few studies investigated the implementation of TPMT testing and the combined evaluation of genotype and phenotype in multidisciplinary clinical settings where patients are undergoing chronic therapy with AZA. Methods A total of 356 AZA-treated patients for chronic autoimmune diseases were enrolled. DNA was isolated from whole blood and the samples were analyzed for the c.460G>A and c.719A>G variants by the restriction fragment length polymorphism (RFLP) technique and sequenced for the c.238G>C variant. The TPMT enzyme activity was determined in erythrocytes by a high-performance liquid chromatography (HPLC) assay. Results All the patients enrolled were genotyped while the TPMT enzyme activity was assessed in 41 patients. Clinical information was available on 181 patients. We found no significant difference in the odds of having adverse drug reactions (ADRs) in wild-type patients and variant allele carriers, but the latter had an extra risk of experiencing hematologically adverse events. The enzyme activity was significantly associated to genotype. Conclusions TPMT variant allele carriers have an extra risk of experiencing hematologically adverse events compared to wild-type patients. Interestingly, only two out of 30 (6.6%) patients had discordant results between genotype, phenotype and onset of ADRs.
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Affiliation(s)
- Francesco Rucci
- Department of Laboratory Medicine, Medical Genetics, ASST Niguarda Hospital, Piazza Ospedale Maggiore, 3-20162 - Milan, Italy, Tel. +39 0264442803
- University of Milan, Department of Oncology and Onco-Hematology, Postgraduate School of Clinical Pharmacology and Toxicology, Milan, Italy
| | - Maria Sole Cigoli
- Department of Laboratory Medicine, Medical Genetics, ASST Niguarda Hospital, Milan, Italy
| | - Valeria Marini
- Department of Internal Medicine, University of Genova, Genova, Italy
| | - Carmen Fucile
- Department of Internal Medicine, University of Genova, Genova, Italy
| | | | - Luigi Robbiano
- Department of Internal Medicine, University of Genova, Genova, Italy
| | - Ugo Cavallari
- Department of Laboratory Medicine, Medical Genetics, ASST Niguarda Hospital, Milan, Italy
| | - Francesco Scaglione
- University of Milan, Department of Oncology and Onco-Hematology, Postgraduate School of Clinical Pharmacology and Toxicology, Milan, Italy
| | - Carlo F Perno
- Department of Laboratory Medicine, ASST Niguarda Hospital, Milan, Italy
| | - Silvana Penco
- Department of Laboratory Medicine, Medical Genetics, ASST Niguarda Hospital, Milan, Italy
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Gong X, Mei S, Li X, Li X, Zhou H, Liu Y, Zhou A, Yang L, Zhao Z, Zhang X. WITHDRAWN: Association between TPMT*3C and decreased thiopurine S-methyltransferase activity in patients with neuromyelitis optica spectrum disorders in China. J Clin Neurosci 2018:S0967-5868(17)31443-1. [PMID: 29534852 DOI: 10.1016/j.jocn.2018.01.051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Accepted: 01/08/2018] [Indexed: 02/07/2023]
Abstract
This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.
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Affiliation(s)
- Xiaoqing Gong
- Neuroinfection and Neuroimmunology Center, Department of Neurology, Beijing Tiantan Hospital, Capital Medical University, 6 Tiantan Xili, Dongcheng District, Beijing 100050, PR China; Department of Neurology, Beijing Shunyi District Hospital, Beijing 101300, PR China
| | - Shenghui Mei
- Department of Pharmacy, Beijing Tiantan Hospital, Capital Medical University, 6 Tiantan Xili, Dongcheng District, Beijing 100050, PR China; Department of Clinical Pharmacology, College of Pharmaceutical Sciences, Capital Medical University, Beijing 100045, PR China
| | - Xindi Li
- Neuroinfection and Neuroimmunology Center, Department of Neurology, Beijing Tiantan Hospital, Capital Medical University, 6 Tiantan Xili, Dongcheng District, Beijing 100050, PR China
| | - Xingang Li
- Department of Pharmacy, Beijing Tiantan Hospital, Capital Medical University, 6 Tiantan Xili, Dongcheng District, Beijing 100050, PR China; Department of Clinical Pharmacology, College of Pharmaceutical Sciences, Capital Medical University, Beijing 100045, PR China
| | - Heng Zhou
- Neuroinfection and Neuroimmunology Center, Department of Neurology, Beijing Tiantan Hospital, Capital Medical University, 6 Tiantan Xili, Dongcheng District, Beijing 100050, PR China
| | - Yonghong Liu
- Neuroinfection and Neuroimmunology Center, Department of Neurology, Beijing Tiantan Hospital, Capital Medical University, 6 Tiantan Xili, Dongcheng District, Beijing 100050, PR China
| | - Anna Zhou
- Neuroinfection and Neuroimmunology Center, Department of Neurology, Beijing Tiantan Hospital, Capital Medical University, 6 Tiantan Xili, Dongcheng District, Beijing 100050, PR China
| | - Li Yang
- Department of Pharmacy, Beijing Tiantan Hospital, Capital Medical University, 6 Tiantan Xili, Dongcheng District, Beijing 100050, PR China; Department of Clinical Pharmacology, College of Pharmaceutical Sciences, Capital Medical University, Beijing 100045, PR China
| | - Zhigang Zhao
- Department of Pharmacy, Beijing Tiantan Hospital, Capital Medical University, 6 Tiantan Xili, Dongcheng District, Beijing 100050, PR China; Department of Clinical Pharmacology, College of Pharmaceutical Sciences, Capital Medical University, Beijing 100045, PR China.
| | - Xinghu Zhang
- Neuroinfection and Neuroimmunology Center, Department of Neurology, Beijing Tiantan Hospital, Capital Medical University, 6 Tiantan Xili, Dongcheng District, Beijing 100050, PR China.
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Ma J, Sies CW, Pike LS. Analytical and clinical validation of an LC-MS/MS method to measure thiopurine S-methyltransferase activity by quantifying d3-6-MMP. Clin Biochem 2018; 54:100-105. [PMID: 29425801 DOI: 10.1016/j.clinbiochem.2018.02.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2017] [Revised: 01/31/2018] [Accepted: 02/04/2018] [Indexed: 10/18/2022]
Abstract
BACKGROUND Identification of patients with thiopurine S-methyltransferase (TPMT) deficiency prior to thiopurine drug therapy has become routine clinical practice worldwide. To measure TPMT activity, traditional radiochemical assays have been replaced by chromatographic methods. METHOD Inspired by the increasing number of isotope labelled sources that may be of benefit for the TPMT assay, a new LC-MS/MS method for TPMT activity was developed and validated. Isotope labelled d3-S-adenosyl-l-methionine (d3-SAM) was selected for the enzymatic methylation of mercaptopurine during sample incubation; d3-6-methylmercaptopurine (d3-6-MMP) with d2-2, 8-hypoxanthine as the internal standard was quantified to ascertain individual TPMT activity. RESULTS The validation of the analytical part of this method showed good linearity (coefficient of determination 0.9999 in the range of 1-500 ng/mL) with the intra-and inter-day impression CV% between 7.6% and 9.1% and 3.7% and 9.2%, respectively. Recovery ranged from 94.9% to 112.3%. The specificity of the enzymatic reaction was validated by using 108 clinical check samples. After compared with traditional radiochemical assay and genotype results, all homozygous and heterozygous deficiency clinical checks fitted into the nominal groups, inter-batch and intra-batch impression CV% were between 2.3% and 9.7%. CONCLUSION With the inclusion of isotope labelled substrate, interfering non-enzymatic methylation no longer results in potential false assignment of abnormal patients. Furthermore, the method can be applied to patients who have already been prescribed thiopurine drugs. This new LC-MS/MS is therefore a favourable clinical routine application to test TPMT activity, as it shows excellent performance in identifying patients with TPMT deficiency.
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Affiliation(s)
- Jing Ma
- Specialist Chemistry, Canterbury Health Laboratories, Christchurch, New Zealand.
| | - Christiaan W Sies
- Specialist Chemistry, Canterbury Health Laboratories, Christchurch, New Zealand.
| | - Linda S Pike
- Specialist Chemistry, Canterbury Health Laboratories, Christchurch, New Zealand.
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Gong X, Mei S, Li X, Li X, Zhou H, Liu Y, Zhou A, Yang L, Zhao Z, Zhang X. Association between TPMT*3C and decreased thiopurine S-methyltransferase activity in patients with neuromyelitis optica spectrum disorders in China. Int J Neurosci 2017; 128:549-553. [PMID: 29191122 DOI: 10.1080/00207454.2017.1401621] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
AIM OF THE STUDY Thiopurines are effective drugs in treating neuromyelitis optica spectrum disorders and other diseases. Thiopurines' toxicity is mainly imputed to thiopurine S-methyltransferase activity. In Chinese population, the most common and important variation of thiopurine S-methyltransferase is TPMT*3C (rs1142345). This study aims to reveal the association between thiopurine S-methyltransferase activity and genetic polymorphisms of thiopurine S-methyltransferase in patients with neuromyelitis optica spectrum disorders in China. MATERIAL AND METHODS A liquid chromatography tandem mass/mass method was used to evaluate the thiopurine S-methyltransferase activity by using 6-mercapthioprine as the substrate in human erythrocyte haemolysate via 1 h incubation at 37 °C to form its methylated product 6-methylmercaptopurine. The amount of 6-methylmercaptopurine was adjusted by haematocrit and normalized to 8 × 108 erythrocytes. The selected polymorphisms of thiopurine S-methyltransferase were identified using MassARRAY system (Sequenom) and multiple SNaPshot technique. RESULTS In 69 patients with neuromyelitis optica spectrum disorders, thiopurine S-methyltransferase activity was 80.29-154.53 (127.51 ± 16.83) pmol/h/8 × 108 erythrocytes. TPMT*3C (rs1142345) was associated with lower thiopurine S-methyltransferase activity (BETA = -25.37, P = 0.011). Other selected variants were not associated with thiopurine S-methyltransferase activity. CONCLUSIONS TPMT*3C affects TPMT activity in Chinese patients with neuromyelitis optica spectrum disorders. Further studies are warranted to confirm the results. ABBREVIATIONS TPRs = thiopurines; NMOSD = neuromyelitis optica spectrum disorders; TPMT = thiopurine S-methyltransferase; LC-MS/MS = liquid chromatography tandem mass/mass; 6-MMP = 6-methylmercaptopurine; IS = internal standard; SNP = single nucleotide polymorphism; MAF = minor allele frequency; HWE = Hardy-Weinberg equilibrium; BETA = regression coefficients; UTR-3 = untranslated region 3.
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Affiliation(s)
- Xiaoqing Gong
- a Neuroinfection and Neuroimmunology Center , Department of Neurology, Beijing Tiantan Hospital , Capital Medical University , Beijing , P. R. China.,b Department of Neurology, Beijing Shunyi District Hospital , Beijing , P. R. China
| | - Shenghui Mei
- c Department of Pharmacy, Beijing Tiantan Hospital , Capital Medical University , Beijing , P. R. China.,d Department of Clinical Pharmacology, College of Pharmaceutical Sciences , Capital Medical University , Beijing , P. R. China
| | - Xindi Li
- a Neuroinfection and Neuroimmunology Center , Department of Neurology, Beijing Tiantan Hospital , Capital Medical University , Beijing , P. R. China
| | - Xingang Li
- c Department of Pharmacy, Beijing Tiantan Hospital , Capital Medical University , Beijing , P. R. China.,d Department of Clinical Pharmacology, College of Pharmaceutical Sciences , Capital Medical University , Beijing , P. R. China
| | - Heng Zhou
- a Neuroinfection and Neuroimmunology Center , Department of Neurology, Beijing Tiantan Hospital , Capital Medical University , Beijing , P. R. China
| | - Yonghong Liu
- a Neuroinfection and Neuroimmunology Center , Department of Neurology, Beijing Tiantan Hospital , Capital Medical University , Beijing , P. R. China
| | - Anna Zhou
- a Neuroinfection and Neuroimmunology Center , Department of Neurology, Beijing Tiantan Hospital , Capital Medical University , Beijing , P. R. China
| | - Li Yang
- c Department of Pharmacy, Beijing Tiantan Hospital , Capital Medical University , Beijing , P. R. China.,d Department of Clinical Pharmacology, College of Pharmaceutical Sciences , Capital Medical University , Beijing , P. R. China
| | - Zhigang Zhao
- c Department of Pharmacy, Beijing Tiantan Hospital , Capital Medical University , Beijing , P. R. China.,d Department of Clinical Pharmacology, College of Pharmaceutical Sciences , Capital Medical University , Beijing , P. R. China
| | - Xinghu Zhang
- a Neuroinfection and Neuroimmunology Center , Department of Neurology, Beijing Tiantan Hospital , Capital Medical University , Beijing , P. R. China
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Wiwattanakul S, Prommas S, Jenjirattithigarn N, Santon S, Puangpetch A, Pakakasama S, Anurathapan U, Sukasem C. Development and validation of a reliable method for thiopurine methyltransferase (TPMT) enzyme activity in human whole blood by LC–MS/MS: An application for phenotypic and genotypic correlations. J Pharm Biomed Anal 2017; 145:758-764. [DOI: 10.1016/j.jpba.2017.07.039] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Revised: 07/06/2017] [Accepted: 07/28/2017] [Indexed: 11/29/2022]
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9
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Pecher D, Dokupilová S, Zelinková Z, Peppelenbosch M, Mikušová V, Mikuš P. Determination of thiopurine S-methyltransferase activity by hydrophilic interaction liquid chromatography hyphenated with mass spectrometry. J Pharm Biomed Anal 2017; 142:244-251. [PMID: 28525791 DOI: 10.1016/j.jpba.2017.05.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Revised: 05/05/2017] [Accepted: 05/08/2017] [Indexed: 12/18/2022]
Abstract
Thiopurine S-methyltransferase (TPMT) plays an important role in the metabolism of thiopurines used in the therapy of inflammatory bowel diseases (IBD). In this work a new progressive method for the determination of TPMT activity in red blood cells lysates was developed. Analysis was carried out by means of hydrophilic interaction liquid chromatography (HILIC) hyphenated with mass spectrometry (MS). In comparison with reversed-phase high-performance liquid chromatography (RP-HPLC), that has been typically applied in determination of TPMT activity, the HILIC significantly improved the analytical signal provided by MS, shortened analysis time, and improved chromatographic resolution. The HILIC-HPLC-MS method was optimized and validated, providing favorable parameters of detection and quantitation limits (5.5 and 16.5pmol/mL, respectively), linearity (coefficient of determination 0.9999 in the range of 0.01-1.0nmol/mL), recovery and precision (93.25-100.37% with RSD 1.06-1.32% in the whole concentration range of QC samples). Moreover, in contrast to the conventional RP-HPLC-UV approach, the complex phenotype TPMT profiles can be reliably and without interferences monitored using the HILIC-HPLC-MS method. Such advanced monitoring can provide valuable detail information on the thiopurines (e.g. evaluating ratio of methylated and non-methylated 6-mercaptopurine) and, by that, TPMT action in biological systems before and during the therapy of IBD.
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Affiliation(s)
- Daniel Pecher
- Department of Pharmaceutical Analysis and Nuclear Pharmacy, Faculty of Pharmacy, Comenius University in Bratislava, Odbojárov 10, SK-832 32 Bratislava, Slovak Republic; Toxicological and Antidoping center, Faculty of Pharmacy, Comenius University in Bratislava, Odbojárov 10, SK-832 32 Bratislava, Slovak Republic
| | - Svetlana Dokupilová
- Department of Pharmaceutical Analysis and Nuclear Pharmacy, Faculty of Pharmacy, Comenius University in Bratislava, Odbojárov 10, SK-832 32 Bratislava, Slovak Republic; Toxicological and Antidoping center, Faculty of Pharmacy, Comenius University in Bratislava, Odbojárov 10, SK-832 32 Bratislava, Slovak Republic
| | - Zuzana Zelinková
- Department of Gastroenterology, St Michael's Hospital, Bratislava, Slovak Republic
| | | | - Veronika Mikušová
- Toxicological and Antidoping center, Faculty of Pharmacy, Comenius University in Bratislava, Odbojárov 10, SK-832 32 Bratislava, Slovak Republic; Department of Cell and Molecular Biology of Drugs, Faculty of Pharmacy, Comenius University in Bratislava, Odbojárov 10, SK-832 32 Bratislava, Slovak Republic
| | - Peter Mikuš
- Department of Pharmaceutical Analysis and Nuclear Pharmacy, Faculty of Pharmacy, Comenius University in Bratislava, Odbojárov 10, SK-832 32 Bratislava, Slovak Republic; Toxicological and Antidoping center, Faculty of Pharmacy, Comenius University in Bratislava, Odbojárov 10, SK-832 32 Bratislava, Slovak Republic.
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10
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Mei S, Li X, Gong X, Zhang X, Li X, Yang L, Zhu L, Zhou H, Liu Y, Zhou A, Zhang X, Zhao Z. Comparison of 6-mercaptopurine with 6-thioguanine for the analysis of thiopurine S-methyltransferase activity in human erythrocyte by LC-MS/MS. Biomed Chromatogr 2017; 31. [PMID: 28212467 DOI: 10.1002/bmc.3959] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2016] [Revised: 01/25/2017] [Accepted: 02/11/2017] [Indexed: 11/05/2022]
Abstract
Thiopurines (TPDs) are first-line drugs in treating neuromyelitis optica spectrum disorders (NMOSD). Evaluation of thiopurine S-methyltransferase activity (TPMT), a major determinant of TPD toxicity, before TPD treatment using 6-mercaptopurine (6-MP) and 6-thioguanine (6-TG) as substrate was suggested. However, the equivalent of the two substrates in TPMT activity evaluation was unknown, and an alternative substrate was required in TPMT activity evaluation in patients who were already taking 6-MP or 6-TG. Before evaluating the agreement of 6-MP and 6-TG in TPMT activity measurement in patients with NMOSD, the affinity of the two substrates for the active center of TPMT should be established. A computer-based simulation indicated that 6-MP and 6-TG had similar affinities for the two active sites of TPMT. According to the guidelines, an LC-MS/MS method was developed and validated to evaluate the TPMT activity in human erythrocyte hemolysate using 6-MP or 6-TG as substrates via 1 h incubation at 37°C. The method was applied in 81 patients with NMOSD. Evaluated by Bland-Altman plot, 6-methylmercaptopurine and 6-methylthioguanine represented TPMT activities were in agreement with each other. Further studies are warranted to confirm the results.
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Affiliation(s)
- Shenghui Mei
- Department of Pharmacy, Beijing Tiantan Hospital, Capital Medical University, Beijing, People's Republic of China.,Department of Clinical Pharmacology, College of Pharmaceutical Sciences, Capital Medical University, Beijing, People's Republic of China
| | - Xindi Li
- Neuroinfection and Neuroimmunology Center, Department of Neurology, Beijing Tiantan Hospital, Capital Medical University, Beijing, People's Republic of China.,China National Clinical Research Center for Neurological Diseases, Beijing Tiantan Hospital, Capital Medical University, Beijing, People's Republic of China
| | - Xiaoqing Gong
- Neuroinfection and Neuroimmunology Center, Department of Neurology, Beijing Tiantan Hospital, Capital Medical University, Beijing, People's Republic of China.,China National Clinical Research Center for Neurological Diseases, Beijing Tiantan Hospital, Capital Medical University, Beijing, People's Republic of China
| | - Xiaoyi Zhang
- College of Pharmaceutical Sciences, Capital Medical University, Beijing, People's Republic of China
| | - Xingang Li
- Department of Pharmacy, Beijing Tiantan Hospital, Capital Medical University, Beijing, People's Republic of China.,Department of Clinical Pharmacology, College of Pharmaceutical Sciences, Capital Medical University, Beijing, People's Republic of China
| | - Li Yang
- Department of Pharmacy, Beijing Tiantan Hospital, Capital Medical University, Beijing, People's Republic of China.,Department of Clinical Pharmacology, College of Pharmaceutical Sciences, Capital Medical University, Beijing, People's Republic of China
| | - Leting Zhu
- Department of Pharmacy, Beijing Tiantan Hospital, Capital Medical University, Beijing, People's Republic of China
| | - Heng Zhou
- Neuroinfection and Neuroimmunology Center, Department of Neurology, Beijing Tiantan Hospital, Capital Medical University, Beijing, People's Republic of China.,China National Clinical Research Center for Neurological Diseases, Beijing Tiantan Hospital, Capital Medical University, Beijing, People's Republic of China
| | - Yonghong Liu
- Neuroinfection and Neuroimmunology Center, Department of Neurology, Beijing Tiantan Hospital, Capital Medical University, Beijing, People's Republic of China.,China National Clinical Research Center for Neurological Diseases, Beijing Tiantan Hospital, Capital Medical University, Beijing, People's Republic of China
| | - Anna Zhou
- Neuroinfection and Neuroimmunology Center, Department of Neurology, Beijing Tiantan Hospital, Capital Medical University, Beijing, People's Republic of China.,China National Clinical Research Center for Neurological Diseases, Beijing Tiantan Hospital, Capital Medical University, Beijing, People's Republic of China
| | - Xinghu Zhang
- Neuroinfection and Neuroimmunology Center, Department of Neurology, Beijing Tiantan Hospital, Capital Medical University, Beijing, People's Republic of China.,China National Clinical Research Center for Neurological Diseases, Beijing Tiantan Hospital, Capital Medical University, Beijing, People's Republic of China
| | - Zhigang Zhao
- Department of Pharmacy, Beijing Tiantan Hospital, Capital Medical University, Beijing, People's Republic of China
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Kasirer Y, Mevorach R, Renbaum P, Algur N, Soiferman D, Beeri R, Rachman Y, Segel R, Turner D. Thiopurine S-methyltransferase (TPMT) activity is better determined by biochemical assay versus genotyping in the Jewish population. Dig Dis Sci 2014; 59:1207-12. [PMID: 24390675 DOI: 10.1007/s10620-013-3008-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Accepted: 12/17/2013] [Indexed: 12/19/2022]
Abstract
BACKGROUND Thiopurine S-methyltransferase (TPMT) is a key enzyme that deactivates thiopurines, into their inactive metabolite, 6-methylmercaptopurine. Intermediate and low TPMT activity may lead to leukopenia following thiopurine treatment. The aim of this study was to determine TPMT activity and TPMT alleles (genotype-phenotype correlation) in Jews, aiming to develop an evidence-based pharmacogenetic assay for this population. METHODS TPMT activity was determined in 228 Jewish volunteers by high performance liquid chromatography. Common allelic variants in the Caucasian population [TPMT*2 (G238C), TPMT *3A (G460A and A719G), TPMT* 3B (G460A) and TPMT*3C (A719G)] were tested. Phenotype-genotype correlation was examined and discordant cases were fully sequenced to identify novel genetic variants. RESULTS Mean TPMT activity was 15.4 ± 4 U/ml red blood cells (range 1-34). Intermediate activity was found in 33/228 (14%) subjects and absent activity was found in one sample (0.4%). Only eight individuals (3.5% of the entire cohort and 24% of those with intermediate/low activity) were identified as carriers of a TPMT genetic variant, all of whom had the TPMT*3A allele. Sequencing the entire TPMT coding region and splice junctions in the remainder of the discordant cases did not reveal any novel variants. CONCLUSION Genotyping TPMT in Jews yields a much lower rate of variants than identified in the general Caucasian population. We conclude that a biochemical assay to determine TPMT enzymatic activity should be performed in Jews before starting thiopurine treatment in order to identify low activity subjects.
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Affiliation(s)
- Yair Kasirer
- Pediatric Gastroenterology and Nutrition Unit, Shaare Zedek Medical Center, The Hebrew University, P.O. B 3235, 91031, Jerusalem, Israel
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12
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Loit E, Tricco AC, Tsouros S, Sears M, Ansari MT, Booth RA. Pre-analytic and analytic sources of variations in thiopurine methyltransferase activity measurement in patients prescribed thiopurine-based drugs: A systematic review. Clin Biochem 2011; 44:751-7. [PMID: 21402061 DOI: 10.1016/j.clinbiochem.2011.03.022] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Revised: 02/16/2011] [Accepted: 03/04/2011] [Indexed: 12/13/2022]
Abstract
OBJECTIVES Low thiopurine S-methyltransferase (TPMT) enzyme activity is associated with increased thiopurine drug toxicity, particularly myelotoxicity. Pre-analytic and analytic variables for TPMT genotype and phenotype (enzyme activity) testing were reviewed. DESIGN AND METHODS A systematic literature review was performed, and diagnostic laboratories were surveyed. RESULTS Thirty-five studies reported relevant data for pre-analytic variables (patient age, gender, race, hematocrit, co-morbidity, co-administered drugs and specimen stability) and thirty-three for analytic variables (accuracy, reproducibility). TPMT is stable in blood when stored for up to 7 days at room temperature, and 3 months at -30°C. Pre-analytic patient variables do not affect TPMT activity. Fifteen drugs studied to date exerted no clinically significant effects in vivo. Enzymatic assay is the preferred technique. Radiochemical and HPLC techniques had intra- and inter-assay coefficients of variation (CVs) below 10%. CONCLUSION TPMT is a stable enzyme, and its assay is not affected by age, gender, race or co-morbidity.
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Affiliation(s)
- Evelin Loit
- Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
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13
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Influences of thiopurine methyltransferase genotype and activity on thiopurine-induced leukopenia in Korean patients with inflammatory bowel disease: a retrospective cohort study. J Clin Gastroenterol 2010; 44:e242-8. [PMID: 20308917 DOI: 10.1097/mcg.0b013e3181d6baf5] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
BACKGROUND AND AIM Myelotoxicity has been shown to be very common in Korean patients with inflammatory bowel disease (IBD) during azathioprine (AZA) or 6-mercaptopurine (6-MP) treatment. The purpose of this study was to investigate the relative risk of the thiopurine methyltransferase (TPMT) and inosine triphosphate pyrophosphatase (ITPA) genotypes and TPMT activity for the development of leukopenia in Korean IBD patients during AZA/6-MP treatment. METHODS We retrospectively analyzed 286 Korean patients with IBD who had been treated with AZA/6-MP for at least 6 months between June 1996 and September 2006. Common TPMT mutations, including TPMT*1, *2, *3A, *3B, and *3C, and ITPA mutations, including 94C>A and IVS2+21A>C, were determined using a high-performance liquid chromatography method. TPMT activity was measured using liquid chromatography with coupled mass spectrometry/mass spectrometry. RESULTS Leukopenia occurred in 118 cases (41.3%). TPMT *1/*3C was detected in 7 cases (2.4%), and ITPA 94 C>A was detected in 66 cases (23.1%), including 63 heterozygotes (22.1%) and 3 homozygotes (1.0%). The median TPMT activity was 9.3 U/mL (interquartile range 10.4, range 2.1 to 76.2). Cox regression analysis revealed that patients with heterozygous *3C type TPMT had a higher probability of leukopenia than those with wild type TPMT (P=0.02). Patients with intermediate TPMT activity had a lower probability of leukopenia than those with low activity (P=0.01). However, the ITPA genotype did not affect the risk of leukopenia. CONCLUSIONS Our data showed that it could be helpful to examine TPMT genotypes and to measure TPMT activity in Korean patients taking AZA/6-MP to predict the development of leukopenia.
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14
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Lee BWK, Sun HG, Zang T, Kim BJ, Alfaro JF, Zhou ZS. Enzyme-catalyzed transfer of a ketone group from an S-adenosylmethionine analogue: a tool for the functional analysis of methyltransferases. J Am Chem Soc 2010; 132:3642-3. [PMID: 20196537 DOI: 10.1021/ja908995p] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
S-adenosylmethionine (AdoMet or SAM)-dependent methyltransferases belong to a large and diverse family of group-transfer enzymes that perform vital biological functions on a host of substrates. Despite the progress in genomics, structural proteomics, and computational biology, functional annotation of methyltransferases remains a challenge. Herein, we report the synthesis and activity of a new AdoMet analogue functionalized with a ketone group. Using catechol O-methyltransferase (COMT, EC 2.1.1.6) and thiopurine S-methyltransferase (TPMT, EC 2.1.1.67) as model enzymes, this robust and readily accessible analogue displays kinetic parameters that are comparable to AdoMet and exhibits multiple turnovers with enzyme. More importantly, this AdoMet surrogate displays the same substrate specificity as the natural methyl donor. Incorporation of the ketone group allows for subsequent modification via bio-orthogonal labeling strategies and sensitive detection of the tagged ketone products. Hence, this AdoMet analogue expands the toolbox available to interrogate the biochemical functions of methyltransferases.
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Affiliation(s)
- Bobby W K Lee
- The Barnett Institute and Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts 02115, USA
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15
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Serpe L, Calvo PL, Muntoni E, D'Antico S, Giaccone M, Avagnina A, Baldi M, Barbera C, Curti F, Pera A, Eandi M, Zara GP, Canaparo R. Thiopurine S-methyltransferase pharmacogenetics in a large-scale healthy Italian-Caucasian population: differences in enzyme activity. Pharmacogenomics 2010; 10:1753-65. [PMID: 19891552 DOI: 10.2217/pgs.09.103] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
AIMS To investigate the influence of genotype, age and gender on the thiopurine S-methyltransferase (TPMT) phenotype in healthy Italian-Caucasian subjects. MATERIALS & METHODS The study investigated the TPMT genotype and the TPMT phenotype of 943 healthy Italian-Caucasian subjects of different age and gender (age range: 0.08-68 years; 623 males 320 females). TPMT red blood cell activity was measured in all samples and genotype was determined for the TPMT alleles *2, *3A, *3B and *3C. RESULTS TPMT activity levels in our whole population ranged from 1.6 up to 75.2 U/gHb. Significant TPMT activity differences between wild-type and heterozygous subjects were observed. We divided our TPMT activity into four categories according to our frequency distribution: low (0.1%), intermediate (32.9%), normal (60%) and high (7%), with arbitrary cut-off values of 8.0, 19.4 and 37.0 U/gHb, respectively. The whole population had a total of 94.5% of homozygous wild-type subjects, 5.4% heterozygous variants and one (0.1%) compound heterozygous variant TPMT*3B/*3C. The overall concordance rate between TPMT genotypes and phenotypes was 71.6%. The TPMT activity was significantly higher in wild-type children (0.08-17 years) than in wild-type adults (aged 18-68 years). Moreover, it was noted that wild-type infants from 0.08 to 5 years had a 9% higher average TPMT activity than the other wild-type groups, and only in children from 0.08 to 2 years was the TPMT activity higher in males than in females. CONCLUSION The data obtained in this study show that genetic factors seem to be the major aspect in TPMT phenotype variability in adults, whilst, in children, other physiological factors should be taken into consideration when assessing the TPMT phenotype, such as age and gender.
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Affiliation(s)
- Loredana Serpe
- Department of Anatomy, Pharmacology and Forensic Medicine, Division of Pharmacology and Experimental Therapeutics, University of Torino, 10125 Torino, Italy
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16
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Daperno M, Sostegni R, Canaparo R, Serpe L, Lavagna A, Crocellà L, Castagno F, Vernetto A, Rigazio C, Ercole E, D'Antico S, Pera A, Zara G, Rocca R. Prospective study of the effects of concomitant medications on thiopurine metabolism in inflammatory bowel disease. Aliment Pharmacol Ther 2009; 30:843-53. [PMID: 19650826 DOI: 10.1111/j.1365-2036.2009.04106.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND Thiopurines are increasingly used in the treatment of inflammatory bowel disease (IBD), being the most common immunosuppressive therapy; however, potentially harmful interactions between thiopurines and other drugs (especially 5-aminosalicylic acid, 5-ASA) were described. AIM To explore potential interactions between thiopurines and concomitant medications. METHODS A total of 183 consecutive IBD patients were enrolled. Clinical characteristics and concomitant medications were recorded. Thiopurine metabolism was analysed with thiopurine S-methyl transferase (TPMT) genetic variants and enzyme activity assays. Comparisons were carried out with stratification of patients according to clinical characteristics and active treatments. RESULTS Based on TPMT genetics, 95% IBD patients were wild-type homozygous, the remaining being heterozygous. Median TPMT activity was 24.9 U/Hgb g (IQR 20.7-29.5). No difference in TPMT activity was noted according to 5-ASA exposure. IBD patients on thiopurines had higher TPMT activity levels, but no dose-effect was evident. No difference in TPMT activity was observed in 41 (63%) patients co-treated with 5-ASA. In patients on active thiopurines also, 6-TGN and 6-MMP levels were evaluated and no significant difference was observed based on co-medication. TPMT activity was independently associated only with thiopurines dose (P = 0.016). CONCLUSIONS Our data suggest the absence of significant interactions between thiopurines and 5-ASA.
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Affiliation(s)
- M Daperno
- Gastroenterology Division, A.O. Ordine Mauriziano, Torino, Italy.
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Tomkova J, Friedecky D, Polynkova A, Adam T. Capillary electrophoresis determination of thiopurine methyl transferase activity in erythrocytes. J Chromatogr B Analyt Technol Biomed Life Sci 2009; 877:1943-5. [DOI: 10.1016/j.jchromb.2009.05.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2008] [Revised: 04/29/2009] [Accepted: 05/01/2009] [Indexed: 02/04/2023]
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Wolf A, Burnat P, Garcia-Hejl C, Ceppa F. [Pharmacological and pharmacogenetic study of two immunomodulators: azathioprine and 6-mercaptopurine. Strategies for preventing complications]. ACTA ACUST UNITED AC 2009; 33:176-84. [PMID: 19243907 DOI: 10.1016/j.gcb.2008.10.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2008] [Revised: 09/18/2008] [Accepted: 10/23/2008] [Indexed: 12/22/2022]
Abstract
Thiopurines are frequently used in gastroenterology for Crohn's disease or hemorrhagic rectocolitis. Their metabolism is regulated by a particular enzyme, thiopurine S-methyltransferase or TPMT. There are three ways to evaluate the effectiveness and the risk of side effects associated with this treatment. TPMT activity measurement or genotyping are recommended to decide for treatment, while metabolites determination is a used as marker of monitoring. Phenotypic approach (TPMT activity measurement or metabolites determination) requires delicate techniques and interindividual variations make the interpretation difficult. Genotyping is easier to interpret but cannot exclude some risk of side effects.
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Affiliation(s)
- A Wolf
- Service de biochimie, toxicologie et pharmacologie cliniques, hôpital d'instruction-des-armées-Begin, 69, avenue de Paris, 94160 Saint-Mandé, France
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Xu J, Yang Q, Qian X, Samuelsson J, Janson JC. Assessment of 4-nitro-1,8-naphthalic anhydride reductase activity in homogenates of bakers’ yeast by reversed-phase high-performance liquid chromatography. J Chromatogr B Analyt Technol Biomed Life Sci 2007; 847:82-7. [PMID: 17070119 DOI: 10.1016/j.jchromb.2006.09.040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2006] [Revised: 09/08/2006] [Accepted: 09/15/2006] [Indexed: 10/24/2022]
Abstract
A simple reversed-phase high-performance liquid chromatographic (RP-HPLC) method was developed for the simultaneous determination of yield and conversion ratio of 4-nitro-1,8-naphthalic anhydride to 4-amino-1,8-naphthalic anhydride following incubation with a crude bakers' yeast homogenate. The analytes were separated on a C18 column in gradient mode. The detection limit of 4-amino-1,8-naphthalic anhydride is 10ng/microl when using a 10microl sample injection volume. The nitroreductase activity in the homogenate system can be assessed during the bioconversion process. The method can be used for the simultaneous detection of 4-hydroxylamino-1,8-naphthalic anhydride, an intermediate with limited stability.
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Affiliation(s)
- Jianqiang Xu
- Department of Bioscience and Biotechnology, Dalian University of Technology, Dalian 116024, China
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20
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Oselin K, Anier K, Tamm R, Kallassalu K, Mäeorg U. Determination of thiopurine S-methyltransferase (TPMT) activity by comparing various normalization factors: Reference values for Estonian population using HPLC-UV assay. J Chromatogr B Analyt Technol Biomed Life Sci 2006; 834:77-83. [PMID: 16517227 DOI: 10.1016/j.jchromb.2006.02.031] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2006] [Revised: 02/10/2006] [Accepted: 02/17/2006] [Indexed: 10/24/2022]
Abstract
Thiopurine S-methyltransferase (TPMT; EC 2.1.1.67) is the key enzyme in the metabolism of thiopurine drugs. Determination of TPMT activity has been used for the individualization of thiopurine dose. We developed HPLC-UV assay for the determination of TPMT activity in human erythrocytes using 6-mercaptopurine as a substrate. Various extraction and chromatographic conditions were compared. In-house developed extraction with acetonitrile provided the lowest limit of quantification. TPMT activity was determined in 99 previously genotyped healthy Estonians. TPMT activity was expressed as the formation of 6-methylmercaptopurine ng/ml/h and normalized either to haemoglobin, haematocrit, erythrocyte count or protein content. The receiver-operating characteristic curve analysis revealed similar accuracy values for TPMT activity in predicting heterozygous and wild type individuals for each method of calculation. In healthy Estonians, TPMT activity varied from 21.5 to 129.6 ng/ml/h. For heterozygous individuals (n = 18), TPMT activity was 48.1 +/- 11.7 ng/ml/h. Wild type individuals (n = 81) revealed significantly higher TPMT activity 79.3 +/- 20.7 ng/ml/h (P < 0.001). This sensitive HPLC assay for quantitative determination of TPMT activity could easily be used in clinical settings. Under constant experimental conditions for haemolysate preparation no normalization is required.
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Affiliation(s)
- Kersti Oselin
- Department of Pharmacology, Tartu University, 51014 Tartu, Estonia.
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