Metaanalysis of methylenetetrahydrofolate reductase (MTHFR) polymorphisms affecting methotrexate toxicity

The Role of Genetics on Psoriasis Susceptibility, Comorbidities, and Treatment Response

This review highlights advances made in psoriasis genetics, including findings from genome-wide association studies, exome-sequencing studies, and copy number variant studies. The impact of genetic variants on various comorbidities and therapeutic responses is discussed.

Pharmacogenetics of Drug Therapies in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic systemic inflammatory disorder that can lead to severe joint damage and is often associated with a high morbidity and disability. Disease-modifying anti-rheumatic drugs (DMARDs) are the mainstay of treatment in RA. DMARDs not only relieve the clinical signs and symptoms of RA but also inhibit the radiographic progression of disease and reduce the effects of chronic systemic inflammation. Since the introduction of biologic DMARDs in the late 1990s, the therapeutic range of options for the management of RA has significantly expanded. However, patients' response to these agents is not uniform with considerable variability in both efficacy and toxicity. There are no reliable means of predicting an individual patient's response to a given DMARD prior to initiation of therapy. In this chapter, the current published literature on the pharmacogenetics of traditional DMARDS and the newer biologic DMARDs in RA is highlighted. Pharmacogenetics may help individualize drug therapy in patients with RA by providing reliable biomarkers to predict medication toxicity and efficacy.

Liver involvement in inflammatory bowel disease: What should the clinician know?

Inflammatory bowel disease (IBD) may show a wide range of extraintestinal manifestations. In this context, liver involvement is a focal point for both an adequate management of the disease and its prognosis, due to possible serious comorbidity. The association between IBD and primary sclerosing cholangitis is the most known example. This association is relevant because it implies an increased risk of both colorectal cancer and cholangiocarcinoma. Additionally, drugs such as thiopurines or biologic agents can cause drug-induced liver damage; therefore, this event should be considered when planning IBD treatment. Additionally, particular consideration should be given to the evidence that IBD patients may have concomitant chronic viral hepatitis, such as hepatitis B and hepatitis C. Chronic immunosuppressive regimens may cause a hepatitis flare or reactivation of a healthy carrier state, therefore careful monitoring of these patients is necessary. Finally, the spread of obesity has involved even IBD patients, thus increasing the risk of non-alcoholic fatty liver disease, which has already proven to be more common in IBD patients than in the non-IBD population. This phenomenon is considered an emerging issue, as it will become the leading cause of liver cirrhosis.

Severe Adverse Toxic Effects of Low-Dose Methotrexate Treatment on an Ectopic Pregnancy Patient With Methylenetetrahydrofolate Reductase Mutations: A Case Report

Background: Low-dose methylenetetrahydrofolate (LD-MTX) has been widely used for the treatment of the ectopic pregnancy (EP) for many decades, and related severe adverse toxic effects are rare. Current studies have shown that the polymorphisms of methylenetetrahydrofolate reductase (MTHFR) gene can decrease the MTX clearance, leading to the metabolite accumulation. However, there is a lack of literature report on an MTHFR gene polymorphism associated with adverse toxic effects resulting from the use of LD-MTX in an EP. Case Presentation: We report a rare case of a 38-year-old female who developed persistent fever, grade IV myelosuppression, skin lesions, mucositis, and liver injury after single dose of LDMTX to treat EP. The personalized genetic testing showed that MTHFR TT (677C>T) and MTHFR AA (1298A>C) were detected. Gradually, the symptoms improved after calcium leucovorin (CF) rescue, continuous renal replacement therapy (CRRT), promoting blood system regeneration, and multiple supportive treatments. Conclusion: This is the first report on the serious adverse toxic effects of LD-MTX on an EP patient with MTHFR mutations. We aim to alert obstetricians and gynecologists to this rare condition. The unexpected life-threatening toxicity with LD-MTX should be highly considered and recognized early. In particular, some easily overlooked gastrointestinal, skin, and mucosal symptoms occur earlier than severe myelosuppression. When toxic effects are suspected, detecting the polymorphisms of an MTHFR gene and monitoring MTX concentration in blood could assist us to formulate individualized and active treatments.

Are There Any Ethnic Differences in the Response to Baricitinib for the Treatment of Rheumatoid Arthritis?

Introduction Baricitinib is an oral synthetic Janus Kinase inhibitor that inhibits JAK1 and JAK2, and the new kid on the block in the treatment of rheumatoid arthritis (RA). To date, there are no studies comparing the clinical benefit of baricitinib in RA between different ethnicities. Ethnicity plays a role in the effectiveness of therapeutic agents. Given the large multi-ethnic population of Leicestershire in the United Kingdom and the range of new therapeutics in RA, we reviewed our cohort of patients with RA to see whether there is any difference in baricitinib Disease Activity Score 28 (DAS28) response between the Asian and White cohorts. Methods This was a retrospective study. The patients included were those under the care of rheumatology at University Hospitals of Leicester (UHL) with a diagnosis of RA and either receiving baricitinib or had received it in the past. Data was collected using the UHL information technology systems, clinic letters and pharmacy records. In addition to ethnicity, we reviewed patient age, gender, concurrent disease-modifying anti-rheumatic drugs (DMARDs) used, previous biologics used, baseline and post-treatment DAS28, dropout from therapy, baseline biochemical assays (anti-cyclic citrullinated peptide (anti-CCP) and rheumatoid factor (RF) status) and radiographic findings. An independent t-test was used to compare continuous data, and Pearson's chi-squared test was used to compare categorical data. Results A total of 120 patients were included in the analysis, and data were analysed with Portable Format for Analytics (PFA). There was no statistically significant difference in the mean DAS28 at baseline (Asian: 5.17 versus White: 4.65; p-value = 0.107) and post-treatment (Asian: 2.8 versus White: 3.3; p-value = 0.404). Comparing both ethnicities, there was no statistically significant difference in previous biologics used, anti-CCP and RF titres, and radiographic findings of erosions. Conclusion This is the first study of its kind, and it found no significant difference in baricitinib response between the Asian and White cohorts. Our study had certain limitations, and future studies will be needed to evaluate this subject further. Such data is important as it can contribute to a body of evidence that may in the future help inform clinical decision-making.

Febrile neutropenia following with single-low-dose methotrexate for the treatment of ectopic pregnancy: a case report

Methotrexate (MTX) is an effective, economical and safe drug used in the treatment of ectopic pregnancy. Complications are very rare. Herein, we reported a case of febrile neutropenia following single low-dose methotrexate for the treatment of ectopic pregnancy. Febrile neutropenia developed on day 4 of single-dose methotrexate administered intramuscularly. Although methotrexate single-dose regimen is quite effective and safe in ectopic pregnancy, febrile neutropenia can occur very rarely.

Adverse Effects of Medications on Micronutrient Status: From Evidence to Guidelines

Recent dietary reference intake workshops focusing on nutrient requirements in chronic disease populations have called attention to the potential adverse effects of chronic medication use on micronutrient status. Although this topic is mostly ill defined in the literature, several noteworthy drug-nutrient interactions (DNIs) are of clinical and public health significance. The purpose of this narrative review is to showcase classic examples of DNIs and their impact on micronutrient status, including those related to antidiabetic, anticoagulant, antihypertensive, antirheumatic, and gastric acid-suppressing medications. Purported DNIs related to other drug families, while relevant and worthy of discussion, are not included. Unlike previous publications, this review is primarily focused on DNIs that have sufficient evidence supporting their inclusion in US Food and Drug Administration labeling materials and/or professional guidelines. While the evidence is compelling, more high-quality research is needed to establish clear and quantitative relationships between chronic medication use and micronutrient status. Expected final online publication date for the Annual Review of Nutrition, Volume 41 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Biomarkers to Personalize the Treatment of Rheumatoid Arthritis: Focus on Autoantibodies and Pharmacogenetics

Rheumatoid arthritis (RA) is a chronic inflammatory disease that is very complex and heterogeneous. If not adequately treated, RA patients are likely to manifest excess of morbidity and disability with an important impact on the quality of life. Pharmacological treatment is based on the administration of the disease-modifying antirheumatic drugs (DMARDs), subdivided into conventional synthetic (csDMARDs), targeted synthetic (tsDMARDs), and biological (bDMARDs). bDMARDs are now frequently administered in patients, both as alternative treatment and together with csDMARDs. Unfortunately, there is a therapeutic response variability both to old and new drugs. Therefore, to identify pre-therapeutic and on-treatment predictors of response is a priority. This review aims to summarize recent advances in understanding the causes of the variability in treatment response in RA, with particular attention to predictive potential of autoantibodies and DMARD pharmacogenetics. In recent years, several biomarkers have been proposed to personalize the therapy. Unfortunately, a magic bullet does not exist, as many factors concur to disease susceptibility and treatment outcomes, acting around the patient’s congenital background. Models integrating demographic, clinical, biochemical, and genetic data are needed to enhance the predictive capacity of specific factors singularly considered to optimize RA treatment in light of multidisciplinary patient management.

Are gene polymorphisms related to adverse events of methotrexate in patients with rheumatoid arthritis? A retrospective cohort study based on an updated meta-analysis

Aims:

We performed an updated meta-analysis to verify correlations between gene polymorphisms and adverse events in methotrexate (MTX)-treated rheumatoid arthritis (RA) patients. Then, we conducted a retrospective cohort study of Han Chinese in China.

Methods:

Relevant studies were collected from the PubMed database and the EMBASE database until December 2017. Pre-allele, dominant, recessive, codominant, and homozygotic models were applied. In addition, a retrospective cohort study enrolling 162 RA patients treated with MTX was conducted. Single nucleotide polymorphism (SNP) genotyping was analyzed by PCR and product sequencing.

Results:

A total of 39 studies were included in 20 meta-analyses; meta-analysis showed a significant association between MTX-related toxicity and 5,10-methylenetetrahydrofolate reductase (MTHFR) 677C>T(rs1801133) polymorphism in East Asian RA patients, and significant associations were observed between MTX-related toxicity and 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase (ATIC) 347C>G (rs2372536), reduced folate carrier 1 (RFC-1) 80G>A (rs1051266), and adenosine triphosphate-binding cassette B1 (ABCB1) 3435C>T(rs1045642) polymorphisms in European RA patients but not in East Asian RA patients. Moreover, in our retrospective cohort study, ATIC 347C>G(rs2372536) and ABCB1 3435C>T(rs1045642) polymorphisms were not associated with MTX-related toxicity. However, a significant association was observed between MTX-related toxicity and RFC-1 80G>A (rs1051266) polymorphism in Chinese Han RA patients.

Conclusion:

Evidence-based results suggest that the MTHFR 677C>T(rs1801133), ATIC 347C>G(rs2372536), RFC-1 80G>A (rs1051266), ABCB1 3435C>T(rs1045642) polymorphisms are associated with MTX-related toxicity. Larger and more stringent study designs may provide more accurate findings for the effects of these SNPs on MTX-related toxicity, and larger sample-size studies of the Chinese Han population should be conducted for further validation.

MTHFR gene polymorphisms and susceptibility to rheumatoid arthritis: a meta-analysis based on 16 studies

Rheumatoid arthritis (RA) is the most common autoimmune rheumatic disease, in which an epigenetic implication in the disease etiopathogenesis has been noted. Here in this meta-analysis, we attempted to investigate the pooled association of methylenetetrahydrofolate reductase (MTHFR) gene C677T and A1298C polymorphisms and susceptibility to RA risk. A systematic search was performed in the main databases, including MEDLINE and Scopus to search for studies assessing the association between MTHFR gene C677T and A1298C polymorphisms and the risk of RA prior to December 2019. In this meta-analysis, 15 studies with 2165 patients and 1751 healthy controls for C677T SNP and 14 studies containing 2021 patients and 1760 healthy controls for A1298C SNP were included. A significant positive association between C677T SNP and RA risk was recognized in the dominant, recessive, and allelic model, but not TT and CT genotypes. The results indicated that the risk of RA in African population was increased under all genotype models while these results were repeated in Asian population just for recessive model, allelic model, and TT genotype. Moreover, the analysis of A1298C SNP demonstrated a significant association in overall population according to only the recessive model and CC genotype. Subgroup analysis according to the genotyping method indicated that RFLP-PCR method could impress the results of association between MTHFR gene A1298C and C677T SNPs and RA risk. The outcome of this meta-analysis indicated that MTHFR gene C677T SNP was much possibly be associated with RA risk.

Ethnogeographic prevalence and implications of the 677C>T and 1298A>C MTHFR polymorphisms in US primary care populations

Aim: Variants of the MTHFR gene have been associated with a wide range of diseases. Materials & methods: The present study analyzed data from clinical genotyping of MTHFR 677C>T and 1298A>C in 1405 patients in urban primary care settings. Results: Striking differences in ethnogeographic frequencies of MTHFR polymorphisms were observed. African-Americans appear to be protected from MTHFR deficiency. Hispanics and Caucasians may be at elevated risk due to increased frequencies of 677C>T and 1298A>C, respectively. Conclusion: Individuals carrying mutations for both genes were rare and doubly homozygous mutants were absent, suggesting the TTcc is extremely rare in the greater population. The results suggest multilocus MTHFR genotyping may yield deeper insight into the ethnogeographic association between MTHFR variants and disease.

Side effects of methotrexate therapy for rheumatoid arthritis: A systematic review

Methotrexate (MTX) is used as an anchor disease-modifying anti-rheumatic drugs (DMARDs) in treating rheumatoid arthritis (RA) because of its potent efficacy and tolerability. MTX benefits a large number of RA patients but partially suffered from side effects. A variety of side effects can be associated with MTX when treating RA patients, from mild to severe or discontinuation of the treatment. In this report, we reviewed the possible side effects that MTX might cause from the most common gastrointestinal toxicity effects to less frequent malignant diseases. In order to achieve regimen with less side effects, the administration of MTX with appropriate dose and a careful pretreatment inspection is necessary. Further investigations are required when combining MTX with other drugs so as to enhance the efficacy and reduce side effects at the same time. The management of MTX treatment is also discussed to provide strategies for occurred side effects. Thus, this review will provide scholars with a comprehensive understanding the side effects of MTX administration by RA patients.

Relationship Between Polymorphisms in Methotrexate Pathway Genes and Outcome of Methotrexate Treatment in a Cohort of 119 Patients with Juvenile Idiopathic Arthritis

OBJECTIVE

To identify clinical and pharmacogenetic determinants of efficacy and toxicity of methotrexate (MTX) in juvenile idiopathic arthritis (JIA) over time.

METHODS

A cohort of 119 consecutive patients with JIA treated with MTX was reviewed. The Juvenile Arthritis Disease Activity Score including 71 joints was used to measure disease activity. Nonresponders were patients who did not reach a minimum of 30% improvement after 6 months of treatment or were switched to biologic drugs in the first 6 months because of inefficacy. All adverse events (AE) were noted. Genotyping of single-nucleotide polymorphisms (SNP) in the genes coding for MTX transporters, folate pathway, and adenosine pathway was performed using real-time PCR methods. Univariate and multivariable penalized logistic and Cox regression were used to analyze data.

RESULTS

Thirty patients (25.8%) were defined as nonresponders and 55 (47.2%) were switched to biologics during the followup. Sixty-five patients (54.5%) reported AE in a total of 405 patient-years, and 10 patients (8.4%) discontinued MTX because of AE. AMPD1 rs17602729 and MTHFD1 rs2236225 were associated with gastrointestinal AE while the latter together with MTRR rs1801394 also demonstrated associations with developing hepatoxicity. MTHFR rs1801131, ABCG2 rs2231137, wild-type of MTR rs1805087, and wild-type of ABCC2 rs2273697 were identified as potential markers for discontinuing MTX treatment because of AE. MTHFR rs1801133, MTRR rs1801394, and ABCC2 rs2273697 were associated with switching to biologics.

CONCLUSION

SNP in different MTX metabolic pathways influence treatment with MTX. Genetic variability is a better marker for toxicity than efficacy.

Hepatic complications induced by immunosuppressants and biologics in inflammatory bowel disease

The incidence of inflammatory bowel diseases (IBD) is rising worldwide. The therapeutic options for IBD are expanding, and the number of drugs with new targets will rapidly increase in coming years. A rapid step-up approach with close monitoring of intestinal inflammation is extensively used. The fear of side effects represents one the most limiting factor of their use. Despite a widespread use for years, drug induced liver injury (DILI) management remains a challenging situation with Azathioprine and Methotrexate. DILI seems less frequent with anti-tumor necrosis factor agents and new biologic therapies. The aim of this review is to report incidence, physiopathology and practical guidelines in case of DILI occurrence with the armamentarium of old and new drugs in the field of IBD.

Methotrexate Hepatotoxicity and the Impact of Nonalcoholic Fatty Liver Disease

Methotrexate (MTX) is commonly used to treat individuals with rheumatological and dermatologic disorders. Current American College of Rheumatology (ACR) and American Association of Dermatology (AAD) guidelines identify diabetes and obesity as risk factors for MTX-induced liver injury. Both diabetes and obesity are components of the metabolic syndrome, and are also risk factors for nonalcoholic fatty liver disease (NAFLD). NAFLD affects approximately 40% of the U.S. population, and those with more advanced NAFLD (i.e., nonalcoholic steatohepatitis with or without fibrosis) are likely to develop progressive liver disease. As such, individuals who are treated with MTX may need to be screened for advanced NAFLD, as this may put them at an increased risk of MTX-induced liver injury. In this mini-review, we review the current ACR and AAD guidelines on MTX hepatotoxicity, discuss the evidence (or lack thereof) of the impact of metabolic risk factors on MTX-induced liver injury and highlight the areas that need further research.

Polymorphisms and Pharmacogenomics for the Clinical Efficacy of Methotrexate in Patients with Rheumatoid Arthritis: A Systematic Review and Meta-analysis

Methotrexate (MTX) is widely used and considered a first-line disease modifying anti-rheumatic drug (DMARD) for the treatment of rheumatoid arthritis (RA). Many of the relevant genes have been investigated to estimate the association between gene polymorphisms and MTX effectiveness in RA patients, although inconsistent results have been reported. A systematic review and meta-analysis were performed to identify genetic variants associated with MTX efficacy. A total of 30 publications that included 34 genes and 125 SNPs associated with the transporters, enzymes, and metabolites of MTX or the progression of RA were included in the systematic review (SR), and 21 studies were included in 9 meta-analyses. Associations between MTX response in RA patients in MTHFR 1298A > C (rs1801131), ATIC 347C > G (rs2372536), RFC-1 80G > A (rs1051266), SLC19A1 A > G (rs2838956) and SLC19A1 G > A (rs7499) genetic polymorphisms were found, but not observed between the MTHFR 677C > T (rs1801133), TYMS 28 bp VNTR (rs34743033), MTRR 66A > G (rs1801394), and ABCB1 3435C > T (rs1045642). However, for the polymorphisms not being associated following meta-analysis could still be associated if larger cohorts were used, and studies of other polymorphisms are necessary in large cohorts and a rigorous way, which may provide more accurate results for the effect of the gene polymorphisms on the MTX response.

Polymorphisms and pharmacogenomics for the toxicity of methotrexate monotherapy in patients with rheumatoid arthritis: A systematic review and meta-analysis

BACKGROUND

Methotrexate (MTX) is widely used and considered a first-line disease modifying antirheumatic drug (DMARD) for the treatment of rheumatoid arthritis (RA). However, 10% to 30% of patients discontinue therapy within a year of starting the treatment, usually because of undesirable side effects. Many of the relevant genes have been investigated to estimate the association between gene polymorphisms and MTX toxicity in RA patients, although inconsistent results have been reported.

METHODS

We searched EMBASE and PubMed in February 2016 for polymorphisms and pharmacogenomics study of the toxicity of MTX monotherapy in RA patients. The meta-analysis was stratified by whether genetic variants associated with MTX toxicity.

RESULTS

A total of 42 publications that included 28 genes with 88 gene SNPs associated with the transporters, enzymes, and metabolites of MTX or the progression of RA were included in the SR, and 31 studies were included in 7 meta-analyses. The meta-analysis showed a significant association between the toxicity of MTX and the RFC-1 80G > A (rs1051266) polymorphism in the European RA patients.

CONCLUSION

RFC-1 80G > A (rs1051266) polymorphism was associated with MTX toxicity, and larger and more stringent study designs may provide more accurate results for the effect of these SNPs on the MTX toxicity.

Are gene polymorphisms related to treatment outcomes of methotrexate in patients with rheumatoid arthritis? A systematic review and meta-analysis

Aim: Identifying the predictors of responsiveness and adverse events in methotrexate (MTX) treated patients with rheumatoid arthritis (RA) has been the focus of most concern, but still without consistent consensus. Methods: PubMed and OVID EMBASE were searched to collect relevant studies that addressed correlations between gene polymorphisms and efficacy and/or toxicity in MTX-treated RA patients. Allelic, recessive, dominant and over-dominant model were applied. Results: A total of 68 studies were included. For associations with efficacy, AMPD1 34C>T polymorphism was related to responsiveness in dominant model (odds ratio [OR]: 1.77; 95% CI: 1.19–2.63) and over-dominant model (OR: 1.59; 95% CI: 1.04–2.45). ATIC T675C polymorphism had association with responsiveness in recessive model (OR: 2.54; 95% CI: 1.23–5.26). For associations with toxicity, polymorphisms in TYMS 1494 del6 and FPGS rs10106 were correlated to absenting overall adverse events in recessive model (OR: 0.68; 95% CI: 0.49–0.95) and dominant model (OR: 0.54; 95% CI: 0.35–0.83) respectively while MTHFR C677T was associated with presenting overall adverse events in allelic model (OR: 1.29; 95% CI: 1.02–1.63), recessive model (OR: 1.38; 95% CI: 1.00–1.89) and dominant model (OR: 1.41; 95% CI: 1.02–1.94). Conclusion: Polymorphisms in AMPD1 34C>T and ATIC T675C predict responsiveness. The absence of TYMS 1494 del6 and FPGS rs10106 and presence of MTHFR C677T predict adverse events in RA patients treated with MTX. Moreover, variations of the associations were found between Caucasians and non-Caucasians.

C677T (RS1801133 ) MTHFR gene polymorphism frequency in a colombian population

INTRODUCTION

Abnormal levels of the enzyme methylenetetrahydrofolate reductase (MTHFR) are associated with an increased risk of both cardiovascular and cerebrovascular disease and higher concentrations of homocysteine. Abnormal levels are also related to birth defects, pregnancy complications, cancer and toxicity to methotrexate (MTX). Polymorphisms of MTHFR affect the activity of the enzyme. Genetic associations have been related to treatment efficacy.

OBJECTIVE

To establish the frequency of the C> T polymorphism at nucleotide 677 of the MTHFR gene in a group of Colombian individuals.

METHODS

Data from pharmacogenetic microarrays that include MTX sensibility-associated polymorphisms were retrospectively collected (Pathway Genomics(®)). The frequency of the C> T MTHFR rs1801133 marker polymorphism was analyzed.

RESULTS

Microarray data from 68 men and 84 women were analyzed. Comparisons of genotype C/C vs. C/T and T/T were statistically significantly different (p= 0.00, p= 0.026, respectively), as were C/T and T / T (p= 0.0001).

CONCLUSIONS

Results for the C/C and C/T genotypes in a Colombian population are similar to other previously studied groups of healthy subjects. Subjects from our population might be at risk of developing diseases associated with MTHFR polymorphisms and might present toxicity and adverse effects if treated with MTX, which suggests the need to evaluate therapeutic alternatives based on individual pharmacogenetic studies.

Identifying Common Genetic Risk Factors of Diabetic Neuropathies

Type 2 diabetes mellitus (T2DM) is a global public health problem of epidemic proportions, with 60-70% of affected individuals suffering from associated neurovascular complications that act on multiple organ systems. The most common and clinically significant neuropathies of T2DM include uremic neuropathy, peripheral neuropathy, and cardiac autonomic neuropathy. These conditions seriously impact an individual's quality of life and significantly increase the risk of morbidity and mortality. Although advances in gene sequencing technologies have identified several genetic variants that may regulate the development and progression of T2DM, little is known about whether or not the variants are involved in disease progression and how these genetic variants are associated with diabetic neuropathy specifically. Significant missing heritability data and complex disease etiologies remain to be explained. This article is the first to provide a review of the genetic risk variants implicated in the diabetic neuropathies and to highlight potential commonalities. We thereby aim to contribute to the creation of a genetic-metabolic model that will help to elucidate the cause of diabetic neuropathies, evaluate a patient's risk profile, and ultimately facilitate preventative and targeted treatment for the individual.

Role of single nucleotide polymorphisms in pharmacogenomics and their association with human diseases

Global statistical data shed light on an alarming trend that every year thousands of people die due to adverse drug reactions as each individual responds in a different way to the same drug. Pharmacogenomics has come up as a promising field in drug development and clinical medication in the past few decades. It has emerged as a ray of hope in preventing patients from developing potentially fatal complications due to adverse drug reactions. Pharmacogenomics also minimizes the exposure to drugs that are less/non-effective and sometimes even found toxic for patients. It is well reported that drugs elicit different responses in different individuals due to variations in the nucleotide sequences of genes encoding for biologically important molecules (drug-metabolizing enzymes, drug targets and drug transporters). Single nucleotide polymorphisms (SNPs), the most common type of polymorphism found in the human genome is believed to be the main reason behind 90% of all types of genetic variations among the individuals. Therefore, pharmacogenomics may be helpful in answering the question as to how inherited differences in a single gene have a profound effect on the mobilization and biological action of a drug. In the present review, we have discussed clinically relevant examples of SNP in associated diseases that can be utilized as markers for "better management of complex diseases" and attempted to correlate the drug response with genetic variations. Attention is also given towards the therapeutic consequences of inherited differences at the chromosomal level and how associated drug disposition and/or drug targets differ in various diseases as well as among the individuals.

A case of recurrent pancytopenia in a patient with acute promyelocytic leukemia on maintenance chemotherapy and concomitant methyltetrahydrofolate reductase and thiopurine S-methyltransferase mutation - review of literature

Pharmacogenetics is a study of how genetic variation of an individual affects the drug response. We report a case of recurrent pancytopenia resulting from maintenance chemotherapy in a patient with acute promyelocytic leukemia and two pharmacogenetic mutations, namely, methylene tetrahydrofolate reductase C677T homozygous mutation and thiopurine methyltransferase mutation.

Outcomes related to methotrexate dose and route of administration in patients with rheumatoid arthritis: a systematic literature review

OBJECTIVES

Methotrexate (MTX) is considered the 'anchor drug' in the therapy of rheumatoid arthritis (RA), yet many physicians do not optimise MTX regimens in spite of high RA disease activity. The recent development of an auto-injector for the subcutaneous (subQ) administration of MTX has prompted re-evaluation of MTX utilisation. The purpose of this systematic literature review is to determine the optimal dose, drug level, and route of administration for MTX in the context of relevant pharmacokinetics and pharmacogenomics.

METHODS

A systematic literature review was performed in Medline searching specifically for randomised controlled trials, systematic reviews, case control and cohort studies evaluating outcomes related to MTX dose and route of administration. Articles fulfilling these inclusion criteria were reviewed. Data on MTX dose, route of administration, clinical response, drug levels and adverse events were evaluated.

RESULTS

Our search identified 420 articles of which 6 were eligible for inclusion using the above criteria. These included 2 systematic reviews, 2 randomised open label trials, one longitudinal study and one retrospective cohort study.

CONCLUSIONS

Efficacy and toxicity for MTX appear related to absorbed dose of MTX, not to route of administration. While bioavailability is greater for parenteral MTX, there is no evidence yet that splitting the oral dose of MTX is less advantageous, less safe or less tolerable than administering parenteral MTX. However, there appear to be modest benefits in beginning with higher doses of MTX, and switching to parenteral MTX when the clinical response to an oral dose is inadequate.

Prediction of methotrexate intolerance in juvenile idiopathic arthritis: a prospective, observational cohort study

BACKGROUND

Methotrexate (MTX) is an effective and safe drug in the treatment of juvenile idiopathic arthritis (JIA). Despite its safety, MTX-related gastrointestinal adverse effects before and after MTX administration, termed MTX intolerance, occur frequently, leading to non-compliance and potentially premature MTX termination. The aim of this study was to construct a risk model to predict MTX intolerance.

METHODS

In a prospective JIA cohort, clinical variables and single nucleotide polymorphisms were determined at MTX start. The Methotrexate Intolerance Severity Score was employed to measure MTX intolerance in the first year of treatment. MTX intolerance was most prevalent at 6 or 12 months after MTX start, which was defined as the outcome for the prediction model. The model was developed in 152 patients using multivariable logistic regression analysis and subsequently internally validated using bootstrapping.

RESULTS

The prediction model included the following predictors: JIA category, antinuclear antibody, parent/patient assessment of pain, Juvenile Arthritis Disease Activity Score-27, thrombocytes, alanine aminotransferase and creatinine. The model classified 77.5% of patients correctly, and 66.7% of patients after internal validation by bootstrapping. The lowest predicted risk of MTX intolerance was 18.9% and the highest predicted risk was 85.9%. The prediction model was transformed into a risk score (range 0-17). At a cut-off of ≥6, sensitivity was 82.0%, specificity 56.1%, positive predictive value was 58.7% and negative predictive value 80.4%.

CONCLUSIONS

This clinical prediction model showed moderate predictive power to detect MTX intolerance. To develop into a clinically usable tool, it should be validated in an independent cohort and updated with new predictors. Such an easy-to-use tool could then assist clinicians in identifying patients at risk to develop MTX intolerance, and in turn to monitor them closely and intervene timely in order to prevent the development of MTX intolerance.

TRIAL REGISTRATION

ISRCTN register, www.isrctn.com, ISRCTN13524271.

Genotype and allele frequencies of drug-metabolizing enzymes and drug transporter genes affecting immunosuppressants in the Spanish white population

Interpatient variability in drug response can be widely explained by genetically determined differences in metabolizing enzymes, drug transporters, and drug targets, leading to different pharmacokinetic and/or pharmacodynamic behaviors of drugs. Genetic variations affect or do not affect drug responses depending on their influence on protein activity and the relevance of such proteins in the pathway of the drug. Also, the frequency of such genetic variations differs among populations, so the clinical relevance of a specific variation is not the same in all of them. In this study, a panel of 33 single nucleotide polymorphisms in 14 different genes (ABCB1, ABCC2, ABCG2, CYP2B6, CYP2C19, CYP2C9, CYP3A4, CYP3A5, MTHFR, NOD2/CARD15, SLCO1A2, SLCO1B1, TPMT, and UGT1A9), encoding for the most relevant metabolizing enzymes and drug transporters relating to immunosuppressant agents, was analyzed to determine the genotype profile and allele frequencies in comparison with HapMap data. A total of 570 Spanish white recipients and donors of solid organ transplants were included. In 24 single nucleotide polymorphisms, statistically significant differences in allele frequency were observed. The largest differences (>100%) occurred in ABCB1 rs2229109, ABCG2 rs2231137, CYP3A5 rs776746, NOD2/CARD15 rs2066844, TPMT rs1800462, and UGT1A9 rs72551330. In conclusion, differences were recorded between the Spanish and other white populations in terms of allele frequency and genotypic distribution. Such differences may have implications in relation to dose requirements and drug-induced toxicity. These data are important for further research to help explain interindividual pharmacokinetic and pharmacodynamic variability in response to drug therapy.

The impact of C677T and A1298C MTHFR polymorphisms on methotrexate therapeutic response in East Bohemian region rheumatoid arthritis patients

Some single-nucleotide polymorphisms (SNPs) might be predictive of methotrexate (MTX) therapeutic outcome in rheumatoid arthritis (RA). The aim of this study was to determine whether SNPs in the methylenetetrahydrofolate reductase (MTHFR) gene are predictive of MTX response. Comparison was made using EULAR response criteria and according to the change of DAS28 (∆DAS28) after a 6-month MTX treatment in RA patient cohort. The two SNPs C677T (rs1801133) and A1298C (rs1801131) have been genotyped. A total of 120 patients were enrolled in the study, and all of them fulfilled the American College of Rheumatology 1987 RA criteria and are currently or previously taking MTX oral treatment, either as a monotherapy (n = 65) or in a combination with other disease-modifying antirheumatic drugs (n = 55). Genotyping was performed using qPCR allelic discrimination. We did not found any association of C677T and A1298C genotypes with MTX treatment inefficacy in dominant model (OR 1.23, 95 % CI 0.57-2.65, P = 0.697; and OR 0.98, 95 % CI 0.47-2.14, P = 1.0, respectively), or in recessive and codominant models. However, when ∆DAS28 after a 6-month therapy was used as a measure of treatment efficacy, the 677CT and 1298AC genotypes were found to be significantly associated with less favorable response to MTX (P = 0.025 and P = 0.043, respectively). In addition, even lower ∆DAS28 was determined for double-mutated 677CT-1298AC heterozygotes. It means that a synergistic effect of 677CT and 1298AC genotypes was observed. Nevertheless, the DAS28 baseline was lower here comparing to other genotypes. Unexpectedly, quite the opposite trend-i.e., better response to MTX-was found in genotypes 677CC-1298CC and 677TT-1298AA. It is an intriguing finding, because these double-mutated homozygotes are known for their low MTHFR-specific activity. Global significance was P = 0.013, η (2) = 0.160-i.e., large-size effect. Thus, our data show greater ability of 677CC-1298CC and 677TT-1298AA genotypes to respond to MTX treatment.

Leukoencephalopathy due to oral methotrexate

Methotrexate (MTX) is considered the main agent for the treatment of rheumatoid arthritis (RA). Neurotoxicity is often mild, but severe encephalopathy can develop, especially with intrathecal or intravenous administration. In rare cases, this syndrome has been observed in patients on long-term low-dose oral administration. A 68-year-old male was diagnosed with RA and on treatment with oral MTX 25 mg weekly for 4 years. The patient started with progressive dysarthria, ataxia and cognitive dysfunction. Complementary tests were normal. Magnetic resonance imaging (MRI) showed hyperintense lesions in both cerebellar hemispheres on T2-weighted and FLAIR images with a diffusion restriction on diffusion-weighted imaging (DWI) and on the apparent diffusion coefficient map (ADC). On postgadolinium T1-weighted images, there were mild enhancements. Spectroscopy showed a demyelinating pattern. A pharmacogenetics determination was made, showing a heterozygous genotype in the MTHFR and ABCB1 genes. Medication with antirheumatic drug was stopped immediately on admission, and the patient gradually improved. MTX-induced leukoencephalopathy can occur even with low-dose administration. The exact pathogenic mechanism is still unknown, but it is hypothesised that it could be the result of a cumulative toxic effect on the blood-brain barrier. The nature of the relationship between the polymorphism and CNS toxicity is still unclear, and thus, further studies are warranted. Often located in the occipital lobes, the involvement of the cerebellum is quite rare. Early recognition of the condition and withdrawal of the drug lead to a better prognosis.

Challenge of liver disease in systemic lupus erythematosus: Clues for diagnosis and hints for pathogenesis

Systemic lupus erythematosus (SLE) encompass a broad spectrum of liver diseases. We propose here to classify them as follows: (1) immunological comorbilities (overlap syndromes); (2) non-immunological comorbilities associated to SLE; and (3) a putative liver damage induced by SLE itself, referred to as "lupus hepatitis". In the first group, liver injury can be ascribed to overlapping hepatopathies triggered by autoimmune mechanisms other than SLE occurring with higher incidence in the context of lupus (e.g., autoimmune hepatitis, primary biliary cirrhosis). The second group includes non-autoimmune liver diseases, such as esteatosis, hepatitis C, hypercoagulation state-related liver lesions, hyperplasic parenchymal and vascular lesions, porphyria cutanea tarda, and drug-induced hepatotoxicity. Finally, the data in the literature to support the existence of a hepatic disease produced by SLE itself, or the occurrence of a SLE-associated prone condition that increases susceptibility to acquire other liver diseases, is critically discussed. The pathological mechanisms underlying each of these liver disorders are also reviewed. Despite the high heterogeneity in the literature regarding the prevalence of SLE-associated liver diseases and, in most cases, lack of histopathological evidence or clinical studies large enough to support their existence, it is becoming increasingly apparent that liver is an important target of SLE. Consequently, biochemical liver tests should be routinely carried out in SLE patients to discard liver disorders, particularly in those patients chronically exposed to potentially hepatotoxic drugs. Diagnosing liver disease in SLE patients is always challenging, and the systematization of the current information carried out in this review is expected to be of help both to attain a better understanding of pathogenesis and to build an appropriate work-up for diagnosis.

Folic acid pathway single nucleotide polymorphisms associated with methotrexate significant adverse events in United States veterans with rheumatoid arthritis

OBJECTIVES

Methotrexate (MTX) is the cornerstone medication in the treatment of rheumatoid arthritis (RA). We examined whether single nucleotide polymorphisms (SNPs) in enzymes of the folic acid pathway (folylpoly-gamma-glutamate synthetase [FPGS], gamma-glutamyl hydrolase [GGH], and methylenetetrahydrofolate reductase [MTHFR]) associate with significant adverse events (SigAE).

METHODS

Patients (n=319) enrolled in the Veterans Affairs RA (VARA) registry taking MTX were genotyped for HLA-DRB1-SE and the following SNPs: FPGS (rs7033913, rs10760503, rs10106), GGH (12548933, rs7010484, rs4617146, rs719235, rs11988534), MTHFR (rs1801131, rs1801133). AE were abstracted from the medical record using a structured instrument. SigAE were defined as an AE leading to MTX discontinuation. Covariates included: age, gender, race, RA antibody status, tobacco, RA disease duration between diagnosis and MTX course, Charlson-Deyo comorbidity index, glucocorticoids, use of prior RA medications, and mean 4-variable disease activity score. Cox regression was performed to determine factors associated with time-to-SigAE. A p-value ≤ 0.005 established significance in the final model.

RESULTS

The presence of ≥ 1 copy of the minor allele in MTHFR rs1801131 was associated with an increased hazard ratio (HR) of SigAE (HR 3.05, 95% CI 1.48-6.29, p-value 0.003 and HR 3.88, 95% CI 1.62-9.28, p-value 0.002 for heterozygotes and homozygotes for the minor allele, respectively). An interaction term, between FPGS rs7033913 heterozygotes and GGH rs11988534 homozygotes for the minor allele, had a p-value <0.0001.

CONCLUSIONS

RA subjects taking MTX may have decreased time-to-SigAE with ≥ 1 copy of the minor allele in MTHFR rs1801131. Further investigation is warranted, as these SNPs may indicate susceptibility to MTX toxicity.

Indispensable or intolerable? Methotrexate in patients with rheumatoid and psoriatic arthritis: a retrospective review of discontinuation rates from a large UK cohort

Methotrexate (MTX) has become the first-line treatment for rheumatoid (RA) and psoriatic arthritis (PsA); however, few studies have focused on its tolerability. The objective of our analyses was to study RA and PsA patients in whom MTX was discontinued, the reasons for this and the duration of MTX treatment prior to withdrawal. A retrospective electronic database review was undertaken to identify all patients who had received MTX for RA or PsA. Patients who had discontinued MTX were then identified, and the reasons for this were categorised. The duration of MTX treatment was assessed in those who had stopped treatment due to intolerability. A total of 1,257 patients who had received MTX were identified [762 (61 %) RA and 193 (15 %) PsA]. MTX had been stopped in 260 (34 %) patients with RA and 71 (36 %) patients with PsA most commonly due to gastrointestinal intolerability. The median duration of MTX treatment was 10 months in both groups, mean duration 21 and 18.6 months in RA and PsA groups, respectively. Overall, one third of patients with RA and PsA stop MTX most commonly due to poor tolerability. In the context of chronic disease, the median duration of treatment is short (10 months). Our analysis did not include patients who suffer from side effects but continue therapy; thus, the magnitude of the problem may be substantially greater therefore as poor tolerability impacts treatment adherence.

Pharmacogenetics and pharmacogenomics for rheumatoid arthritis responsiveness to methotrexate treatment: the 2013 update

Rheumatoid arthritis (RA) is a complex, systemic autoimmune disease characterized by chronic inflammation of multiple peripheral joints, which leads to serious destruction of cartilage and bone, progressive deformity and severe disability. Methotrexate (MTX) is one of the first-line drugs commonly used in RA therapy owing to its excellent long-term efficacy and cheapness. However, the efficacy and toxicity of MTX treatment have significant interpatient variability. Genetic factors contribute to this variability. In this review, we have summarized and updated the progress of RA response to MTX treatment since 2009 by focusing on the fields of pharmacogenetics and pharmacogenomics. Identification of genetic factors involved in MTX treatment response will increase the understanding of RA pathology and the development of new personalized treatments.

MTHFR functional genetic variation and methotrexate treatment response in rheumatoid arthritis: a meta-analysis

Aim: To date, functional MTHFR SNPs have been tested for their impact on low-dose methotrexate (MTX) response in small rheumatoid arthritis (RA) cohorts. We sought to test their effect in the single largest cohort studied to date, and undertook a meta-analysis utilizing stringent study inclusion criteria. Materials & methods: RA patients treated with MTX monotherapy from the Yorkshire Early Arthritis Register (YEAR) were genotyped using RFLP assays, and tested for association with treatment efficacy. Studies for meta-analysis were screened by a set of stringent inclusion criteria. Results & conclusion: rs1801131 and rs1801133 were not associated with response to MTX in the YEAR cohort, nor did they affect the probability of achieving a low disease activity state. A meta-analysis of comparable studies found no association with these SNPs. MTHFR SNPs rs1801131 and rs1801133 are unlikely to have a clinically meaningful effect on the first 6 months of MTX treatment in early RA.

Original submitted 30 May 2013; Revision submitted 20 November 2013

Pharmacogenetics in rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic inflammatory arthritis leading to severe joint damage and associated with high morbidity and mortality. Disease-modifying antirheumatic drugs (DMARDs) are the mainstay of treatment in RA. DMARDs not only relieve the clinical signs and symptoms of RA but also inhibit the radiographic progression of disease. In the last decade, a new class of disease-modifying medications, the biologic agents, has been added to the existing spectrum of DMARDs in RA. However, patients' response to these agents is not uniform with considerable variability in both efficacy and toxicity. There are no reliable means of predicting an individual patient's response to a given DMARD prior to initiation of therapy. In this chapter, the current published literature on the pharmacogenetics of traditional DMARDS and the newer biologic DMARDs in RA is highlighted. Pharmacogenetics may help individualize drug therapy in patients with RA in the near future.

Genetic risk factors for drug-induced liver injury in rheumatoid arthritis patients using low-dose methotrexate

Low-dose methotrexate (MTX) is part of the mainstay of rheumatoid arthritis treatment. Hepatotoxicity is among the most feared side effects of low-dose MTX and is associated with increased morbidity. At present, histological evaluation of liver biopsies is the gold standard to retrospectively diagnose MTX-induced liver damage. Genetic markers present an interesting opportunity to preemptively identify patients at risk for MTX-induced hepatotoxicity. Here, we will review the literature on candidate genetic markers for the risk of MTX-induced hepatotoxicity. These candidate genetic markers include polymorphisms in the gene encoding the enzyme MTHFR.

Methotrexate pharmacogenetics in rheumatoid arthritis: a status report

Methotrexate (MTX), an antifolate drug, is the first-line disease-modifying agent for the treatment of rheumatoid arthritis (RA) worldwide. MTX has excellent long-term efficacy, tolerability and safety. Early initiation of MTX in patients with RA controls joint destruction and slows progression of disease. However, the clinical response to MTX and frequency of adverse effects from the drug exhibit marked interpatient variability. Over the past decade, there has been a quest to identify genetic markers that reliably predict MTX efficacy and toxicity and help optimize MTX therapy in RA; that is, the field of MTX pharmacogenetics. This review will summarize key pharmacogenetic studies examining SNPs in the genes encoding enzymes in the MTX cellular pathway and their association with MTX response in RA. As evident from this review, MTX pharmacogenetics in RA remains a muddled field, mostly due to inconsistent results from several small underpowered studies.

Do impaired memory, cognitive dysfunction and distress play a role in methotrexate-related neutropenia in rheumatoid arthritis patients? A comparative study

We evaluated the roles of sociocultural status, distress and cognitive functions in rheumatoid arthritis (RA) patients who developed methotrexate (MTX)-related neutropenia. The data of 37 RA patients with MTX-related neutropenia who were being followed up at 3 centers were evaluated. The control group included 74 RA patients. The clinical features, biochemical tests and treatment modalities of the patients were obtained from hospital files. The mini-mental state examination (MMSE) test and the Hospital Anxiety and Depression Scale (HADS) were administered for all RA patients with neutropenia as well as the control group. The frequencies of male patients, illiterate patients, patients living alone, patients with serious visual impairment, those with low income, and patients with high creatinine were significantly higher among RA patients with MTX-related neutropenia than in controls (p values <0.05). The RA patients with MTX-related neutropenia had significantly lower MMSE scores, and significantly higher HADS-A and HADS-D scores than controls (p values <0.05). In addition, the proportion of patients with probable dementia was significantly higher in RA patients with MTX-related neutropenia than in controls (p < 0.001). Twenty-six of the 37 patients (70.3 %) developed neutropenia with daily dosing. Patients who used MTX daily were more likely to be living alone than those using weekly dosing (p = 0.011). Multivariate analysis showed that having probable dementia on the MMSE test (OR 52.6), low income level (OR 56.8) and age (OR 1.12) were independent risk factors for the development of MTX-related neutropenia. The presence of probable dementia on MMSE, low socioeconomical status and older age are associated with serious toxicity in RA patients using MTX. Measures should be taken to prevent wrong MTX dosing by the patients. Compliance and patient education is of major importance, in particular, in the patients presented in this study.

Role of interactions in pharmacogenetic studies: leukotrienes in asthma

Researchers have identified thousands of loci involved in complex traits and drug response. However, in most cases they only explain a small proportion of the heritability of the trait. Among different strategies conducted to identify this 'missing heritability', here we illustrate the importance of complex gene-environment interactions using findings regarding the role of leukotrienes on the bronchodilator response to albuterol in Latino asthmatics. Patients managing their asthma with leukotriene-modifying medication presented higher increases in the bronchodilator response to albuterol. Moreover, interactions between genes responsible for leukotriene production were associated with a decreased risk of asthma. Combining genetic and pharmacologic effects, leukotriene-modifying users carrying certain combinations of alleles presented higher improvements in lung function after bronchodilator administration. Genes and drugs act at different orders of interaction (from individual effects to gene-gene-drug-drug interactions) and population-specific effects have to be considered. These results may be extrapolated to other complex phenotypes.

Old and new antirheumatic drugs and the risk of hepatotoxicity

Given the high prevalence of the use of medications in daily practice and the large number of people taking antirheumatic agents, the risk of drug-drug interactions and of hepatotoxicity is of concern. Both old and new compounds show such a risk. Nonsteroidal antinflammatory drugs are widely used drugs with potential adverse hepatic reactions. Nonsteroidal antinflammatory drugs are responsible for an important aliquot of transaminase elevation in the general population. Genetic susceptibility to diclofenac hepatotoxicity has promoted the knowledge about drug-specific, class-specific reactions. Some drugs (sulfasalazine, azathioprine, and leflunomide) may cause acute liver injury, whereas other compounds (methotrexate) may cause chronic liver damage as the result of the interaction among drug, host and environmental factors. The tumor necrosis factor-alpha inhibitor, infliximab, is associated with typical drug-induced autoimmune hepatitis. Also, the other biological disease-modifying antirheumatic drugs are not free of potential hepatotoxicity. The diagnosis of drug-induced liver injury follows the exclusion of other causes, involves a temporal relationship between drug exposure and adverse event, and should consider the potential participation of the underlying rheumatic disease to event occurrence. This article also includes data regarding hepatotoxicity from our outclinic patients receiving biological disease-modifying antirheumatic drugs.

Pharmacogenetics of disease-modifying antirheumatic drugs in rheumatoid arthritis: towards personalized medicine

Rheumatoid arthritis is a disease showing considerable heterogeneity in all its aspects, including response to therapy. The efficacy of disease-modifying antirheumatic drugs (DMARDs), with or without biological activity, has been unambiguously established. DMARDs improve the symptoms associated with the disease, and, even more importantly, are capable of stagnating the joint damage associated with the disease. Nonetheless, a considerable proportion of patients fail to achieve an adequate response and/or experience toxicity. This variability in treatment response between individuals has given rise to an extensive search for prognostic markers in order to personalize and optimize therapy in rheumatoid arthritis patients. Pharmacogenetics, the study of genetic variation underlying differential responses to drugs, is a rapidly progressing field in rheumatology that might enable personalized therapy in rheumatic diseases. This review will summarize the pharmacogenetics of commonly used synthetic and biological DMARDs.