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Johnson D, Hughes D, Pirmohamed M, Jorgensen A. Evidence to Support Inclusion of Pharmacogenetic Biomarkers in Randomised Controlled Trials. J Pers Med 2019; 9:jpm9030042. [PMID: 31480618 PMCID: PMC6789450 DOI: 10.3390/jpm9030042] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 08/15/2019] [Accepted: 08/19/2019] [Indexed: 01/01/2023] Open
Abstract
Pharmacogenetics and biomarkers are becoming normalised as important technologies to improve drug efficacy rates, reduce the incidence of adverse drug reactions, and make informed choices for targeted therapies. However, their wider clinical implementation has been limited by a lack of robust evidence. Suitable evidence is required before a biomarker’s clinical use, and also before its use in a clinical trial. We have undertaken a review of five pharmacogenetic biomarker-guided randomised controlled trials (RCTs) and evaluated the evidence used by these trials to justify biomarker inclusion. We assessed and quantified the evidence cited in published rationale papers, or where these were not available, obtained protocols from trial authors. Very different levels of evidence were provided by the trials. We used these observations to write recommendations for future justifications of biomarker use in RCTs and encourage regulatory authorities to write clear guidelines.
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Affiliation(s)
- Danielle Johnson
- Institute of Translational Medicine, Department of Biostatistics, University of Liverpool, Waterhouse Building, 1-5 Brownlow Street, Liverpool L69 3GL, UK.
| | - Dyfrig Hughes
- Centre for Health Economics and Medicines Evaluation, Bangor University, Ardudwy, Normal Site, Bangor LL57 2PZ, UK
| | - Munir Pirmohamed
- MRC Centre for Drug Safety Science and Wolfson Centre for Personalised Medicine, Institute of Translational Medicine, Waterhouse Building, 1-5 Brownlow Street, Liverpool L69 3GL, UK
| | - Andrea Jorgensen
- Institute of Translational Medicine, Department of Biostatistics, University of Liverpool, Waterhouse Building, 1-5 Brownlow Street, Liverpool L69 3GL, UK
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Murray B, Hawes E, Lee RA, Watson R, Roederer MW. Genes and beans: pharmacogenomics of renal transplant. Pharmacogenomics 2014; 14:783-98. [PMID: 23651025 DOI: 10.2217/pgs.13.68] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Advances in the management of patients after solid organ transplantation have led to dramatic decreases in rates of acute rejection, but long-term graft and patient survival have remained unchanged. Individualized therapy after transplant will ideally provide adequate immunosuppression while limiting the adverse effects of drug therapy that significantly impact graft survival. Therapeutic drug monitoring represents the best approximation of individualized drug therapy in transplant at this time; however, obtaining pharmacogenomic data in transplant patients has the potential to enhance our current practice. Polymorphisms of target genes that impact pharmacokinetics have been identified for most immunosuppressants, including tacrolimus, cyclosporine, mycophenolate, azathioprine and sirolimus. In the future, pre-emptive assessment of a patient's genetic profile may inform drug selection and provide information on specific doses that will improve efficacy and limit toxicity.
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Affiliation(s)
- Brian Murray
- Critical Care Clinical Specialist, UNC Hospitals & Clinics, 101 Manning Drive, CB #7600, Chapel Hill, NC 27599-7600, USA.
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Skrzypczak-Zielinska M, Borun P, Milanowska K, Jakubowska-Burek L, Zakerska O, Dobrowolska-Zachwieja A, Plawski A, Froster UG, Szalata M, Slomski R. High-resolution melting analysis of the TPMT gene: a study in the Polish population. Genet Test Mol Biomarkers 2012; 17:153-9. [PMID: 23252704 DOI: 10.1089/gtmb.2012.0192] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The thiopurine S-methyltransferase (TPMT) gene encoding thiopurine methyltransferase is a crucial enzyme in metabolism of thiopurine drugs: azathioprine and 6-mercoptopurine, which are used in the treatment of leukemia or inflammatory bowel diseases. Genetic polymorphism of the TPMT gene correlates with activity of this enzyme, individual reaction, and dosing of thiopurines. Thirty-one variants of the TPMT gene with low enzymatic activity have been described with three major alleles: TPMT*2 (c.238G>C), *3A (c.460 G>A, c.719A>G), and *3C (c.719A>G), accounting for 80% to 95% of inherited TPMT deficiency in different populations in the world. The aim of the study was to establish a rapid and highly sensitive method of analysis for the complete coding sequence of the TPMT gene and to determine the spectrum and prevalence of the TPMT gene sequence variations in the Polish population. Recently, high-resolution melting analysis (HRMA) has become a highly sensitive, automated, and economical technique for mutation screening or genotyping. We applied HRMA for the first time to TPMT gene scanning. In total, we analyzed 548 alleles of the Polish population. We found 11 different sequence variations, where two are novel changes: c.200T>C (p.P67S, TPMT*30) and c.595G>A (p.V199I, TPMT*31). Detection of these new rare alleles TPMT*30 and *31 in the Polish population suggests the need to analyze the whole TPMT gene and maybe also the extension of routinely used tests containing three major alleles, TPMT*2, *3A, and *3C. Identification of sequence variants using HRMA is highly sensitive and less time consuming compared to standard sequencing. We conclude that HRMA can be easy integrated into genetic testing of the TPMT gene in patients treated with thiopurines.
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Higgs JE, Payne K, Roberts C, Newman WG. Are patients with intermediate TPMT activity at increased risk of myelosuppression when taking thiopurine medications? Pharmacogenomics 2010; 11:177-88. [PMID: 20136357 DOI: 10.2217/pgs.09.155] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
UNLABELLED Thiopurine S-methyltransferase (TPMT) metabolizes thiopurine medications, including azathioprine and 6-mercaptopurine. Absent TPMT activity (i.e., in individuals homozygous for a variant TPMT allele) is associated with an increased risk of myelosuppression in patients taking thiopurine drugs. However, it is not clear if there is also an increased risk for patients with intermediate TPMT activity (i.e., in individuals heterozygous for a variant TPMT allele). AIMS To quantify the increased risk of myelosuppression for patients with intermediate TPMT activity. MATERIALS & METHODS A systematic review identified published studies, up to 29 September 2008, that explored the relationship between TMPT and hematological adverse drug reactions to thiopurines. Following a critical appraisal of the quality of published studies, a meta-analysis calculated the odds ratio of myelosuppression for patients with intermediate TPMT activity compared with wild-type. RESULTS A total of 67 studies were identified, the majority retrospective cohort in design. Patients with two TPMT variant alleles who are TPMT deficient have a substantial increase in their risk of myelotoxicity (86% of deficient patients developed myelosuppression). The increase in odds ratio of developing leukopenia for patients with intermediate TPMT activity or one TPMT variant allele compared with wild-type was 4.19 (95% CI: 3.20-5.48). CONCLUSION This meta-analysis suggests that individuals with both intermediate and absent TPMT activity have an increased risk of developing thiopurine-induced myelosuppression, compared with individuals with normal activity. However, there is significant variability in the quality of the reported studies and large prospective studies to clarify the size of the effect of TPMT variant alleles on the risk of myelosuppression should be conducted. Accurate risk assessments will provide important data to inform clinical guidelines.
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Affiliation(s)
- Jenny E Higgs
- Central Manchester & Manchester Children's University Hospitals NHS Trust, Manchester Royal Infirmary, Manchester, UK
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Molyneux G, Gibson FM, Chen CM, Marway HK, McKeag S, Mifsud CVJ, Pilling AM, Whayman MJ, Turton JA. The haemotoxicity of azathioprine in repeat dose studies in the female CD-1 mouse. Int J Exp Pathol 2008; 89:138-58. [PMID: 18336531 PMCID: PMC2525763 DOI: 10.1111/j.1365-2613.2008.00575.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2007] [Accepted: 12/02/2007] [Indexed: 01/27/2023] Open
Abstract
Azathioprine (AZA) is a cytotoxic immunosuppressive drug used in the prevention of rejection in organ transplants and the treatment of auto-immune diseases. However, AZA is haemotoxic causing significant bone marrow depression. The present studies were to characterize the haemotoxicity of AZA in the female CD-1 mouse. In Experiment 1, a dose-ranging study, with AZA gavaged daily for 10 days, clinical evidence of toxicity was evident at 125 mg/kg and above. Experiment 2 was a dose-response study with AZA gavaged daily for 10 days at 40-120 mg/kg. At day 1 after the final dose, AZA induced a dose-related pancytopaenia, reduced femoral marrow cellularity, increases in serum levels of the cytokine fms-like tyrosine kinase 3 ligand, reduction in granulocyte-monocyte colony-forming units and erythroid colonies, and increased bone marrow apoptosis. Histology demonstrated hepatocyte hypertrophy, thymic atrophy, reduced splenic extramedullary haemopoiesis, and reduced cellularity of sternal bone marrow. In Experiment 3, AZA was dosed for 10 days at 100 mg/kg with autopsies at 1, 3, 9, 22, 29, 43 and 57 days postdosing. At 1, 3 and 9 days, haematological parameters reflected changes in Experiment 2. At 22/29 days, many blood parameters were returning towards normal; at 43/57 days, most parameters compared with controls. However, there was some evidence of a persistent (i.e. residual/late-stage) mild reduction in RBC and erythroid progenitor cell counts at day 43/57. We conclude that the CD-1 mouse provides an acceptable model for the haemotoxicity of AZA in man.
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Affiliation(s)
- Gemma Molyneux
- Division of Cellular and Molecular Medicine, Section for Cellular and Molecular Pathology, St. George's, University of London, London,UK
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Song DK, Zhao J, Zhang LR. TPMT genotype and its clinical implication in renal transplant recipients with azathioprine treatment. J Clin Pharm Ther 2006; 31:627-35. [PMID: 17176368 DOI: 10.1111/j.1365-2710.2006.00775.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND Thiopurine S-methyltransferase (TPMT) catalyses the S-methylation of thiopurine drugs. Patients with intermediate or deficient TPMT activity are at risk of toxicity after receiving standard doses of these drugs. OBJECTIVE This study determined the frequencies of TPMT alleles (TPMT*2, *3A, *3B and *3C) and explored the association between TPMT genetic polymorphism and the development of adverse drug reactions in Chinese renal transplant patients receiving azathioprine (AZA). METHODS TPMT genotypes were determined using polymerase chain reaction-based assays in 122 renal transplant patients and 210 healthy subjects. Biochemical and clinical data were retrospectively evaluated after renal transplantation. RESULTS Of 122 patients, eight (allele frequency 3.28%) were heterozygous for TPMT*3C and no TPMT*2, *3A or *3B or homozygous TPMT*3C subjects were identified. The pattern and frequency of the main mutant TPMT alleles were similar in patients and healthy subjects. Four of five patients (80%) with haematopoietic toxicity were heterozygotes. TPMT heterozygosity was associated with significant reductions in haematological indices and a significant decrease in cyclosporine plasma concentrations in the first year after renal transplantation. No association between TPMT genotype and renal rejection was identified. CONCLUSION Our results, together with those of others pointing in the same direction, suggest that genotyping the major TPMT variant alleles may be a valuable tool in preventing AZA toxicity and optimization of immunosuppressive therapy.
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Affiliation(s)
- D-K Song
- Department of Urology, The First Affiliated Hospital, Zhengzhou University, Zhengzhou, China
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Kurzawski M, Dziewanowski K, Gawrońska-Szklarz B, Domański L, Droździk M. The impact of thiopurine s-methyltransferase polymorphism on azathioprine-induced myelotoxicity in renal transplant recipients. Ther Drug Monit 2006; 27:435-41. [PMID: 16044099 DOI: 10.1097/01.ftd.0000164393.09402.c9] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Thiopurine S-methyltransferase (TPMT) is an enzyme that catalyzes the S-methylation of thiopurine drugs such as 6-mercaptopurine, 6-thioguanine, and azathioprine. TPMT activity exhibits an interindividual variability, mainly as a result of genetic polymorphism. Patients with intermediate or deficient TMPT activity are at risk for toxicity after receiving standard doses of thiopurine drugs. It has previously been reported that 3 variant alleles: TPMT*2, *3A, and *3C are responsible for over 95% cases of low enzyme activity. The purpose of this study was to explore the association between these polymorphisms and the occurrence of azathioprine adverse effects in 112 renal transplant recipients undergoing triple immunosuppressive therapy including azathioprine, cyclosporine, and prednisone. TPMT genetic polymorphism was determined using PCR-RFLP and allele-specific PCR methods. Azathioprine dose, leukocyte, erythrocyte, and platelet counts, graft rejection episodes, as well as cyclosporine levels were analyzed throughout the first year after organ transplantation. We found the frequency of leukopenia episodes (WBC < 4.0 x 10(9)/L) significantly higher in heterozygous patients (53.8%) compared with those with TPMT wild-type genotype (23.5%). One patient, who was a compound homozygote (3A/*3C), experienced severe azathioprine-related myelotoxicity each time after receiving the standard drug dose. Our results suggest that polymorphisms in TPMT gene may be responsible for approximately 12.5% of all leukopenia episodes in renal transplant recipients treated with azathioprine. Genotyping for the major TPMT variant alleles may be a valuable tool in preventing AZA toxicity and optimization of immunosuppressive therapy.
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Affiliation(s)
- Mateusz Kurzawski
- Department of Pharmacology, Pomeranian Medical University, Szczecin, Poland.
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Formea CM, Myers-Huentelman H, Wu R, Crabtree J, Fujita S, Hemming A, Reed A, Howard R, Karlix JL. Thiopurine S-methyltransferase genotype predicts azathioprine-induced myelotoxicity in kidney transplant recipients. Am J Transplant 2004; 4:1810-7. [PMID: 15476481 DOI: 10.1111/j.1600-6143.2004.00575.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Azathioprine (AZA) is an immunosuppressive prodrug that undergoes metabolism by thiopurine S-methyltransferase (TPMT). Eighty to ninety-five percent of low or deficient TPMT enzyme activity is genetically determined by the presence of three nonfunctional mutant alleles: TPMT*2, TPMT*3A and TPMT*3C. Using TPMT as a pharmacogenetic paradigm, we explored the association between these genetic mutations and development of adverse drug effects in an ethnically diverse renal transplant population receiving azathioprine. Biochemical and clinical data were retrospectively evaluated during the first four weeks after kidney transplantation. TPMT nonfunctional mutant alleles were identified by polymerase chain reaction-based methods. Of 89 patients initially consented, 36 met inclusion criteria for this retrospective study. Five patients possessing a single TPMT nonfunctional mutant allele were identified: TPMT*3A: n = 2 Caucasians; TPMT*3B: n = 1 Caucasian; TPMT*3C: n = 2 African-Americans. TPMT nonfunctional mutant alleles were associated with significant reductions in hematological indices and a significant increase in cyclosporine plasma concentrations in the first month post-transplant. TPMT genotype was an independent predictor for hemoglobin, hematocrit and red blood cell changes while mean azathioprine dose (mg/kg/day), azathioprine dose (mg/kg/day) at day 30 and cyclosporinemia at day 30 were not. Prospective application of pharmacogenetic principles may assist in optimization of immunosuppressive drug therapy and minimize drug toxicities.
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Affiliation(s)
- Christine M Formea
- College of Pharmacy, Department of Nephrology, University of Florida, Gainesville, Florida, USA.
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Pharmacoepidemiology and drug safety. Pharmacoepidemiol Drug Saf 2003; 12:73-88. [PMID: 12616852 DOI: 10.1002/pds.787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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