Sivaraman, J (2014) A Study on the Clinical Profile and Pharmacogenetics of Methotrexate Treatment in Patients with Rheumatoid Arthritis. Masters thesis, Institute of Pharmacology, Madras Medical College, Chennai.
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Abstract
AIM AND OBJECTIVES: The present study is to investigate the single nucleotide polymorphism within Methotrexate pathway gene (MTHFR A1298C) related to efficacy and toxicity in Indian Rheumatoid arthritis patients Primary Objective: Genotyping assay to study the distribution of different alleles within the study population Secondary Objectives: To assess the efficacy of MTX therapy by DAS and HAQ. To evaluate the toxicity of MTX. To study the distribution of responders and non-responders to MTX therapy. Rheumatoid arthritis is an autoimmune disease that results in a chronic, Systemic inflammatory disorder that affects many tissues and organs, but principally affects the flexible (synovial) joints. It can be a disabling and painful condition, which can lead to substantial loss of functioning and mobility if not adequately treated. Methotrexate is the cornerstone for the therapy of rheumatoid arthritis in spite of the advent of newer biologics. MTX is fast acting and has best efficacy: toxicity ratio and also cheaper. Due to the variation in response and toxicity profile, 1/3rd of the patients discontinue therapy due to its adverse effects. At cellular level MTX and MTX-PGs (metabolite of MTX) inhibit several enzymes of purine, pyrimidine biosynthesis and also exert anti-inflammatory effect. MTHFR is one of such enzyme inhibited by MTX. So the study in the polymorphism of MTHFR gene can be a better tool to reveal the efficacy: toxicity of MTX. This study was done in the Department of Rheumatology at Rajiv Gandhi Government General Hospital, Madras Medical College, Chennai. A total of 100 patients were enrolled for this study and after 3months follow-up period 42 RA patients completed the study. Successful genotyping of MTHFR A1298C was observed in 96 RA patients and 44 control subjects. The frequency of MTHFR A1298C polymorphism was determined in RA patients and control subjects. During enrolment patients were assessed by clinical examination and lab investigations and they were repeated after 3 months. Data were compiled and results analysed statistically. The efficacy related parameters comprised of morning stiffness, pain scale, tender and swollen-joint counts, and disease activity score, health assessment questionnaire scoring and weekly dose of MTX. Toxicity related parameters were SGOT, SGPT and GI symptoms. The most widely reported polymorphisms were C677T and A1298C, in MTHFR gene which is associated with efficacy and adverse effects. In 1998, MTHFR A1298C has been reported by Weisberg et al, which causes glutamine to alanine substitution and renders reduced activity of the enzyme. In A1298C polymorphism the homozygous mutants have about ~40% reduction in enzyme activity. In our study, the frequency distribution of genetic polymorphism in south Indian healthy subjects is 32.6% and 67.44% respectively for wild-type and mutants, which is contradictory to a study conducted at Pune, European and African population. In Pune study the frequency of this polymorphism was reported to be 70% and 30% for wild-type and mutants respectively, in a total of one hundred and forty four unrelated healthy subjects, which is similar to European population. In African healthy subjects, the frequency was reported to be 87% and 13% by Yogita et al. [59] The reason for this difference could be due to Ethnic variation. In our study the frequency distribution of polymorphism in RA patients were observed as 31.3 : 68.75 for A and C alleles respectively, which is contradictory to a study conducted in Japanese RA patients by Sachie Inoue et al,[55] the frequency of A:C were 76:24 respectively. A study in Israel RA patients by Berkun et al,[49] it was reported as 53.8 : 46.2 for A and C alleles respectively.It was found to be 74 : 26 and in Caucasians it was reported as 45 : 55. This proves racial differences in the allelic frequency. Berkun et al,[49] reported that the allele frequency of 1298CC was higher in RA population and the carriers of 1298AA allele had higher frequency of adverse effects in spite of higher folic acid supplementation and 1298CC may protect against MTX related adverse effects, conducted in 93 RA patients in Israel. In our study, similarly 1298CC was higher in RA population but the frequency of adverse effects was higher in the CC genotype and is not protective of MTX-related adverse effects. Instead, CC genotype is predictive of adverse effects in spite of folate supplementation. The reason for this difference could be due to Ethnic variation and probably be attributed to smaller sample size of the study. In our study 1298AA genotypes were associated with better response to MTX treatment and lower incidence of adverse effects, whereas the 1298C allele carriers are prone for adverse effects. In a study by Wessels et al,[58] who reported that MTHFR 1298AA was associated with less improvement relative to mutants, which is contradictory to our study and MTHFR 1298C allele carriers, developed more adverse effects. Whereas Graber et al reported that MTHFR A1298C polymorphism is protective related to adverse effects of MTX, which is a contradictory to above finding. Polygenetic analysis will address this limitation. In our study, the elevation in transaminases and GI adverse events in spite of folate supplementation was found to be higher in 1298CC genotype than the 1298AC and this polymorphism warrants susceptibility to MTX toxicity. This is similar to the results of the study conducted by Davis et al.[52] In our study the proportion of patients experiencing toxicity is found to be higher in 1298CC genotypes than 1298AA genotypes and this is similar to the study conducted by Choe et al,[51] in Korean RA patients. In our study the 1298AA genotype shows better improvement comparable to 1298CC genotypes. The DAS score and HAQ score increased insignificantly for 1298CC genotype and the dose required for remission has also increased and they could become non-responders if the drug is administered chronically. This is similar to the results of study conducted by Kato et al.[54] Urano et al,[56] in 2002 assessed both C677T & A1298C polymorphisms in this gene and found A1298C polymorphism rendered the patients sensitive to MTX treatment, whereas C677T rendered the patients prone for toxicity. In haplotype analysis 677C-1298C were receiving lower dose of MTX and 677T-1298A had a higher frequency of side-effects from MTX. The reported toxicities were elevation of transaminases, gastrointestinal (GI) disturbances, hair loss, fatigue and rash. The same was confirmed in their second study published in the year 2007. In their subsequent study in 2009, the same group also reported that these two polymorphisms are not associated with the occurrence of fracture. In our study, haplotype-analysis was not done and further studies are essential to study the interaction of these two polymorphisms in the MTHFR gene. Assessment of the genotypes could be useful to identify the subset of genotypes such as 1298CC and their relative phenotypes and appropriate dose decisions with track of adverse effects could be useful to assess better clinical response. This study proves pharmacogenetics could be a tool for assessing the treatment outcomes. Larger sample size, haplotype analysis and investigation of other genes contributing to the enzymatic pathway of methotrexate could guide clinicians in tackling variations in clinical toxicity and efficacy in rheumatoid arthritis. CONCLUSION: The frequency distribution of genetic polymorphism of MTHFR A1298C gene was different among control and RA patients. The 1298CC genotype was higher in RA patients compared to control group. The 1298AA genotype shows better efficacy and lower incidence of toxicity to MTX therapy in the RA patients. The 1298CC genotype shows elevation in transaminases and GI adverse events in spite of folate supplementation to MTX therapy in the RA patients. The RA patients with 1298AA genotype found were to be good responders and 1298CC genotype patients show poor response to MTX therapy in RA.
| Item Type: | Thesis (Masters) |
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| Uncontrolled Keywords: | Pharmacogenetics; Methotrexate Treatment; Patients; Rheumatoid Arthritis |
| Subjects: | PHARMACY > Pharmacology |
| Depositing User: | Ravindran C |
| Date Deposited: | 23 Oct 2017 05:25 |
| Last Modified: | 23 Oct 2017 05:25 |
| URI: | http://repository-tnmgrmu.ac.in/id/eprint/3767 |
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