Methotrexate Polyglutamate Levels Research Articles

Genetic polymorphisms and their association with methotrexate polyglutamates during maintenance treatment in Korean children and young adults with acute lymphoblastic leukemia

The aim of this study was to investigate the impact of genetic polymorphisms on methotrexate (MTX) metabolism in Korean children and young adults with acute lymphoblastic leukemia, specifically focusing on MTX polyglutamates (MTX-PGs) in erythrocytes, which have been rarely studied. Korean children and young adult patients undergoing maintenance therapy for acute lymphoblastic leukemia, who were receiving weekly oral MTX doses of 20 mg/m²/week, were prospectively included. We investigated erythrocyte MTX-PG (PG1 to PG5) levels, MTX-PG/MTX dose ratios, and 222 genetic polymorphisms spanning 78 genes and three intergenic areas related to MTX transport, folate cycle metabolism, purine/pyrimidine pathways, and non-pathway genes (including TPMT and NUDT15 genotypes) to explore their association with MTX metabolism. MTX-PG levels were associated with MTX dose (p < 0.05), and MTX-PG3 comprised the majority of the total MTX-PGs, with a median of 39.3 %. Various polymorphisms within the same gene demonstrated differing associations with each type of MTX-PG, underscoring the complexity of MTX pharmacogenetics. Among the polymorphisms examined, 14 across 13 genes showed significant associations with MTX-PG2–5 levels, even after adjusting for the false discovery rate (ABCC5, ATG16L1, CEP72, FSTL5, GMPS, HTR3A, IMPDH1, NT5C2, SLC28A3, SLCO1B3, SUCLA2, TPMT, and TYMS). This study enhances our understanding of genetic polymorphisms in MTX metabolism and therapeutic monitoring for MTX maintenance, promoting personalized medicine in acute lymphoblastic leukemia patients.

Methotrexate Polyglutamates Analysis by Chromatography Methods in Biological Matrices: A Review.

Methotrexate (MTX) is used as an immunosuppressant and antineoplastic drug in clinical practice. MTX is a parent drug and converts to MTX polyglutamates (MTXPGs) to exhibit its biological activity. Clinical studies found that MTXPG levels were associated with MTX response and toxicities, especially at low doses. Due to huge variance of MTX response and toxicities between individuals, therapeutic drug monitoring is necessary for its use in individualized therapy. Various chromatography methods coupled with ultraviolet-visible detector, fluorescence detector and mass spectrometry have been reported for MTXPG analysis in various biological matrices. The aim of this paper is to review the chromatographic based methods for the measurement of total and/or individual MTXPGs. We searched Embase, Science Direct and PubMed databases using "methotrexate polyglutamate" and "chromatography" as search terms, and found 745 articles. Of those, 14 articles were extracted for this study. The key steps for method development (sample pretreatment, parameter optimization of liquid chromatography and mass spectrometry, selection of internal standard) and validation (lower limit of quantitation, accuracy, precision, recovery, matrix effect and stability) were analyzed and summarized, which might be helpful for researchers to develop their own methods.

Adverse effects related to methotrexate polyglutamate levels: adjudicated results from the cardiovascular inflammation reduction trial.

Methotrexate is widely used at low dosages (LD-MTX) for non-oncologic indications and is associated with a variety of adverse effects (AEs). We sought to determine whether concentrations of the active metabolite, MTX polyglutamates (MTX-PGs) 1-5, correlate with AEs. We examined data from the LD-MTX arm of the randomized double-blind Cardiovascular Inflammation Reduction Trial (CIRT). All AEs were blindly adjudicated and monitoring laboratories were tested centrally. The MTX-PGs 1-5 were assessed in one reference laboratory using liquid chromatography-tandem mass spectrometry. Based on prior literature, MTX-PGs 3-5 were chosen as the exposure of interest and quartiles of MTX-PGs 3-5 were assessed for their relationship with all AEs and each pre-specified category of AE using adjusted Cox proportional hazards regression. Of the 2391 subjects randomized to LD-MTX, MTX-PG levels were available for 1319 subjects (median dosage 16.1 mg/week) from the 8 month visit. We followed these subjects for a median of 2.2 years [interquartile range (IQR) 1.5-2.9]. Higher MTX-PG3-5 levels were related to an increased risk of anaemia [compared with quartile 1 (Q1); hazard ratio (HR) for Q4 1.27 (95% CI 0.98, 1.65), P for trend = 0.05] and a decreased risk of thrombocytopenia [HR for Q4 0.52 (95% CI 0.32, 0.84), P for trend = 0.05]. MTX-PG3-5 levels >134 nmol/l were associated with an increased risk of liver abnormalities [HR 1.36 (95% CI 1.08, 1.72)]. Higher MTX- PG3-5 levels were modestly associated with LD-MTX AEs, including anaemia and liver function abnormalities, but a reduced risk of thrombocytopenia and haemorrhage. NCT01594333.

Glutamic Acid Increased Methotrexate Polyglutamation and Cytotoxicity in a CCRF-SB Acute Lymphoblastic Leukemia Cell Line.

Background and Objectives: Acute lymphoblastic leukemia (ALL) is the most common type of cancer in childhood. The majority of patients respond to treatment, but those with resistant phenotypes suffer relapse or death. The antifolate methotrexate (MTX) is the most commonly used drug against ALL due to its efficacy. Once inside leukemic cells, MTX is metabolized into methotrexate polyglutamates (MTX-PG) by action of the enzyme folylpolyglutamate synthetase (FPGS), leading to a longer action compared to that of MTX alone. Materials and Methods: In this work, we demonstrated that the combination treatment of methotrexate and 5 and 10 mM glutamic acid could enhance methotrexate cytotoxicity in CCRF-SB (B-ALL) cells. In addition, MTX plus 20 mM glutamic acid was able to improve the synthesis of MTX-PG5. Results: All treatments induced an increase in FPGS expression compared to that of the control group. Furthermore, we detected different cellular expression patterns of FPGS in the different treatments. Conclusion: Based on these findings, we demonstrated that levels of methotrexate polyglutamates (MTX-PGs) could be a key determinant of methotrexate-induced cytotoxicity in CCRF-SB acute lymphoblastic leukemia cells.

Increased Risk of Early Hematologic Toxicity during Maintenance Therapy in Acute Lymphoblastic Leukemia Patients of South Indian Origin Carrying NUDT15*3 Allele

Background and Objectives: Globally the survival of ALL has increased tremendously with the five-year overall survival (OS) reaching 90% in high-income countries (HICs) (1, 2). However, in India, the five-year OS has been reported to be 30-70 %( 3) and deaths due to treatment related toxicity (TRT) in ALL were ranged from 2-24 % (4), which is ten times higher compared to HICs suggesting increased susceptibility to the toxicity of the chemotherapeutic drugs. This could be due to frequent variants in candidate genes determining the pharmacodynamic response or pharmacokinetics of the chemotherapeutic drugs used during maintenance therapy of ALL. Variations in the patient management, supportive care therapy are the other possible reasons of this increased incidence of TRT. Many patients are lost to follow-up due to the TRT, and eventually will die of the disease progression. The present study aimed to explore the association of common genetic variants in the candidate genes with early treatment related hematological toxicities (grade 3-4) in patients with Acute Lymphoblastic Leukemia (ALL) receiving low-dose MTX (LDMTX) and 6-Mercaptopurine (6-MP) based maintenance therapy. Materials and Methods: This prospective study was conducted between August 2011 and May 2016 and approved by institutional scientific and ethics committees. A total of 71 patients (43 males and 28 females aged between 1-51 years) with ALL were enrolled in the study after obtaining written informed consent and in the case of children, from legally accepted guardians. Patients below 25 years of age were treated using protocol-841 (MCP) I2A and those older than 25 years were treated with modified GMALL-84 protocols. MTX and 6-MP doses did not differ across both the protocols during maintenance therapy. Germline DNA samples collected at the time of remission from peripheral mononuclear cells was used to genotype15 selected variants frequent in the following candidate genes : ABCB1, DHFR, GGH, FPGS, MTHFR, RFC1, SLCO1B1, TPMT, and NUDT15 using allele discrimination assay by real-time PCR. LC-MS/MS method was used to measure methotrexate polyglutamate (MTXPG3-5) levels in RBC's.Toxicities were graded according to the Common Terminology Criteria for Adverse Events (CTCAE-version 4.03). Early grade 3-4 hematological toxicities occurring within first 100 days of the maintenance therapy was studied for its association with the genetic variants and other risk factors. Cumulative incidence curves were plotted and a risk factor analysis was performed using multivariate Cox regression. Co-linearity between variables was assessed. We used a back-ward selection method, retaining those variables with P-values&lt;0.05 in the final model. Data analysis was done using statistical software « R ». Results: The cumulative incidences of early hematological TRT (grade 3-4) and relapse were 54.9 %, and 38.0 %, respectively. The relapse free survival was 59.2 %. The median follow-up of all patients from the start of maintenance was 1018 days. In multivariate analysis including all genetic variants, age, and WBC counts at diagnosis, we observed a significant increase in the risk of TRT in carriers of NUDT15*3 allele(rs116855232 ; p=0.002 ; univariate Hazards ratio : 2.81 (95% CI : 1.41-5.59). 3435C&gt;T variant in ABCB1 gene showed a trend of association with that of relapse free survival. Neither the genetic variants studied were associated with the methotrexate polyglutamate levels, nor were the levels associated with the clinical outcomes. Conclusion: The NUDT15*3 allele carriers status could be used as one of the stratifying markers in South Indian ALL patients at the time of diagnosis to distinguish high and low-risk patients to develop early hematological toxicity, especially related to 6-mercaptopurine based ALL maintenance therapy protocols. Disclosures No relevant conflicts of interest to declare.

Folyl polyglutamate synthethase (FPGS) gene polymorphisms may influence methotrexate adverse events in South Indian Tamil Rheumatoid Arthritis patients.

The aim of the study was to look for the association of FPGS 2752 G > A (rs1544105), FPGS 1994 A > G (rs10106), and GGH 452 C > T (rs 11545078), GGH -401C > T (rs 3758149) gene polymorphisms with methotrexate (MTX) treatment response and MTX-induced adverse events in South Indian Tamil patients with rheumatoid arthritis (RA). Further the influence of these gene polymorphisms on MTX polyglutamate levels was analyzed. A total of 330 patients with RA were investigated. FPGS gene polymorphisms were analyzed by TaqMan 5'nuclease assay and GGH gene polymorphisms were analyzed by PCR-RFLP. Methotrexate polyglutamates (nmol/L of packed erythrocytes) were measured by liquid chromatography mass spectrometry (LCMS/MS) method. We found that the heterozygous genotype of FPGS rs1544105 [p = 0.02, OR 1.93, 95% CI (1.15-3.35)] and FPGS rs10106 AG genotype [p = 0.01, OR 2.11, 95% CI (1.20-3.71)] were associated with MTX adverse events. FPGS rs1544105 and GGH -401C > T SNPs influenced the polyglutamate levels. None of the investigated SNPs seems to be associated with MTX treatment outcome.

The relationship between the efficacy of methotrexate in rheumatoid arthritis and the achieved level of its polyglutamates in erythrocytes (pilot study)

Therapeutic control of the methotrexate (MT) polyglutamates (MTPG) level in erythrocytes can be an objective marker of the effective dose of MT prescribed for rheumatoid arthritis (RA).Objective: to assess the relationship between the level of MTPG in red blood cells and efficacy of the MT dose used by RA patients.Subjects and methods. The study included 60 patients with RA (44 women and 16 men over 18 years) who met the criteria of the American College of Rheumatology and the European League Against Rheumatism (ACR/EULAR) 2010 and received MT ≥20 mg/week subcutaneously for ≥12 weeks. The patients were divided into two groups of comparable age, sex, alcohol intake, number of smokers, body mass index (BMI), depending on the presence (group 1; n=30) or absence (group 2; n=30) of the effect of MT, according to the EULAR efficacy criteria (DAS28). The concentration of MTPG (total MTPG and metabolites of MTPG 1, 2, 3, 4, 5) was determined in erythrocytes by high-performance liquid chromatography with mass spectrometric detection.Results and discussion. It was found that the levels of total MTPG and MTPG1, 2, 3, 5 in erythrocytes did not differ in groups of responders and nonresponders, and the dose of MT was comparable in both groups. At the same time, the level of MTPG4 in the first group was significantly higher (26.4±6.1 nmol/l; p=0.023) than in the second one (22.1±6.8 nmol/l). Analysis of the ROC curve showed that the values of MTPG4 &lt;22.5 nmol/l corresponded to the absence of effect of MT. The area under the curve was 0.672 (95% confidence interval 0.536–0.808 (p=0.022), sensitivity 77%, specificity 53.3%.Conclusion. For effective treatment of patients with RA MT dose should provide MTPG4 level in red blood cells ≥22.5 nmol/l.

Methotrexate polyglutamate levels and co-distributions in childhood acute lymphoblastic leukemia maintenance therapy

Methotrexate polyglutamates (MTXpg) facilitate incorporation of thioguanine nucleotides into DNA (DNA-TG, the primary cytotoxic thiopurine metabolite and outcome determinant in MTX/6-mercaptopurine treatment of childhood ALL). We hypothesized that mapping erythrocyte levels of MTXpg with 1-6 glutamates and their associations with DNA-TG formation would facilitate future guidelines for maintenance therapy dosing. Summed MTX with 1-6 glutamates resolved by LCMS [median (interquartile): 5.47 (3.58-7.69) nmol/mmol hemoglobin] was in agreement with total MTX by radio ligand assay. In 16,389 blood samples from 1426 ALL maintenance therapy patients, MTXpg3 21.0 (15.2-27.4)% was the predominant metabolite, and MTXpg1 (the maternal drug) constituted 38.6 (27.2-50.2)% of MTXpg1-6. All subsets correlated; the strongest associations were between metabolites with similar polyglutamate lengths. Correlations of MTXpg1 with MTXpg2 and MTXpg3,4,5,6 were rs = 0.68 and rs = 0.25-0.42, respectively. Intercorrelations of MTXpg3,4,5,6 were all rs ≥ 0.51. MTXpg4 accounted for 29.8 (24.7-33.3)% of MTXpg3-6, yet explained 96% of the summed MTXpg3-6 variation. MTXpg1-4, MTXpg1-6, MTXpg2-6 and MTXpg3 were all associated with DNA-TG levels (p < 0.00001), but collinearity precluded identification of the most informative subset. Measuring erythrocyte MTXpg4 simplifies and can replace longer chain MTXpg monitoring. Resolving individual MTXpg identifies samples that are unsuitable for dose guidance due to high levels of MTXpg1 remaining in the plasma fraction because of recent MTX intake. All tested MTXpg subsets correlated with DNA-TG and may be used for ALL maintenance therapy dose adjustments, but the most informative subset remains to be identified.

Do SNPs in folate pharmacokinetic pathway alter levels of intracellular methotrexate polyglutamates and affect response? A prospective study in Indian patients.

This study investigated the impact of seven polymorphisms in genes of folate transport and (de)glutamation pathway on methotrexate polyglutamate levels and response in patients with rheumatoid arthritis. This prospective study included patients with rheumatoid arthritis. They were treated with methotrexate (up to 25mg per week) for 24weeks and categorized by EULAR response criteria into responders (good and moderate) and non-responders. Using real-time Taqman discrimination assay, SNPs were genotyped-rs1045642 (ABCB1 3435C>T), rs1128503 (ABCB1 1236C>T), rs10106 (FPGS 1994A>G), rs1544105 (FPGS G>A), rs11545078 (GGH 452C>T), rs3758149 (GGH -401C>T), and rs1051266 (RFC1 80G>A). RBC methotrexate polyglutamate1-5(MTX-glu1-5) levels were determined at 4, 8, 16, and 24weeks using by reverse phase HPLC using C-18 column followed by post column photo-oxidation. This study included 117 patients with rheumatoid arthritis (M:F = 14:103). The mean dose of methotrexate at 24weeks was 22.0 ± 4.0mg, with data on DAS28(3) at 24weeks available in 96 patients-61 responders and 35 non-responders. Minor allele of GGH 452C>T had an association with non-response (odds ratio 2.9, 95% CI 1.4-5.6) and assuming the dominance of C, the recessive genetic model found GGH 452C>T CC genotype (odds ratio 9.5, 95% CI 1.2 to 76.0) was significantly associated with response. However, there was no difference in MTX-glu1-5 levels among the various genotypes of this SNP (p = 0.9). Other SNPs were neither associated with response nor with alteration in methotrexate polyglutamate levels. On logistic regression, GGH 452C>T CC genotype and DAS28(3) at baseline were independent predictors of response. GGH 452C>T CC genotype was associated with response to methotrexate. None of the SNPs affected MTX-glu1-5levels.

High Methotrexate Triglutamate Level Is an Independent Predictor of Adverse Effects in Asian Indian Rheumatoid Arthritis Patients-A Preliminary Study.

It is unclear whether erythrocyte methotrexate polyglutamate levels (MTX-glun) are associated with response or adverse effects to methotrexate in rheumatoid arthritis. This preliminary study evaluated their utility in Asian Indian patients over 24 weeks. Rheumatoid arthritis patients were started on oral methotrexate at a dose of 15 mg/wk, which was escalated to 25 mg by 12 weeks and continued till 24 weeks. Erythrocyte (RBC) MTX-glu1 to MTX-glu5 levels (nmol/L RBC) were determined at 4, 8, 16, and 24 weeks by using reverse-phase high-performance liquid chromatography. Area under the concentration curve (AUC) of MTX-glu1-5, MTX-glu3-5, and MTX-glu3 levels was compared between groups with regards to response and adverse effects. This study included 117 patients with mean (SD) age of 42.7 (±11.9) years and disease duration of 2.0 (1.7) years. Mean (SD) RBC MTX-glu1-5 levels at 4, 8, 16, and 24 weeks were 93 (±29), 129 (±46), 143 (±49), and 159 (±65) nmol/L RBC; the highest individual polyglutamate was MTX-glu3 (40%). There was significant correlation between MTX-glu1-5 (r = 0.38, P < 0.001) and MTX-glu3 (r = 0.49, P < 0.001) with methotrexate dose. There was no significant difference of AUC MTX-glun between responders and nonresponders. However, AUC MTX-glu3 was significantly (P = 0.03) higher in patients with adverse effects. On logistic regression, AUC of MTX-glu3 [odds ratio = 1.004 (95% confidence interval 1.002-1.007)] and methotrexate dose at 24 weeks were independent predictors of adverse effects. In this preliminary study, higher levels of RBC MTX-glu3 were found to be the independent predictors for adverse effects in rheumatoid arthritis patients.

Investigating methotrexate toxicity within a randomized double-blinded, placebo-controlled trial: Rationale and design of the Cardiovascular Inflammation Reduction Trial-Adverse Events (CIRT-AE) Study.

The role of low dose methotrexate (LDM) in potential serious toxicities remains unclear despite its common use. Prior observational studies investigating LDM toxicity compared LDM to other active drugs. Prior placebo-controlled clinical trials of LDM in inflammatory conditions were not large enough to investigate toxicity. The Cardiovascular Inflammation Reduction Trial (CIRT) is an ongoing NIH-funded, randomized, double-blind, placebo-controlled trial of LDM in the secondary prevention of cardiovascular disease. We describe here the rationale and design of the CIRT-Adverse Events (CIRT-AE) ancillary study which aims to investigate adverse events within CIRT. CIRT will randomize up to 7000 participants with cardiovascular disease and no systemic rheumatic disease to either LDM (target dose: 15-20mg/week) or placebo for an average follow-up period of 3-5 years; subjects in both treatment arms receive folic acid 1mg daily for 6 days each week. The primary endpoints of CIRT include recurrent cardio vascular events, incident diabetes, and all-cause mortality, and the ancillary CIRT-AE study has been designed to adjudicate other clinically important adverse events including hepatic, gastrointestinal, respiratory, hematologic, infectious, mucocutaneous, oncologic, renal, neurologic, and musculoskeletal outcomes. Methotrexate polyglutamate levels and genome-wide single nucleotide polymorphisms will be examined for association with adverse events. CIRT-AE will comprehensively evaluate potential LDM toxicities among subjects with cardiovascular disease within the context of a large, ongoing, double-blind, placebo-controlled trial. This information may lead to a personalized approach to monitoring LDM in clinical practice.

Association of erythrocyte methotrexate-polyglutamate levels with the efficacy and hepatotoxicity of methotrexate in patients with rheumatoid arthritis: a 76-week prospective study

ObjectiveTo assess the utility of erythrocyte methotrexate-polyglutamate (MTX-PG) concentrations in determining the safety and efficacy of MTX in patients with rheumatoid arthritis (RA).Methods79 MTX-naïve patients with RA were enrolled in...

Methotrexate polyglutamates as a potential marker of adherence to long-term therapy in children with juvenile idiopathic arthritis and juvenile dermatomyositis: an observational, cross-sectional study.

IntroductionMethotrexate (MTX) is a cornerstone of treatment in a wide variety of inflammatory conditions, including juvenile idiopathic arthritis (JIA) and juvenile dermatomyositis (JDM). However, owing to its narrow therapeutic index and the considerable interpatient variability in clinical response, monitoring of adherence to MTX is important. The present study demonstrates the feasibility of using methotrexate polyglutamates (MTXPGs) as a biomarker to measure adherence to MTX treatment in children with JIA and JDM.MethodsData were collected prospectively from a cohort of 48 children (median age 11.5 years) who received oral or subcutaneous (SC) MTX therapy for JIA or JDM. Dried blood spot samples were obtained from children by finger pick at the clinic or via self- or parent-led sampling at home, and they were analysed to determine the variability in MTXPG concentrations and assess adherence to MTX therapy.ResultsWide fluctuations in MTXPG total concentrations (>2.0-fold variations) were found in 17 patients receiving stable weekly doses of MTX, which is indicative of nonadherence or partial adherence to MTX therapy. Age (P = 0.026) and route of administration (P = 0.005) were the most important predictors of nonadherence to MTX treatment. In addition, the study showed that MTX dose and route of administration were significantly associated with variations in the distribution of MTXPG subtypes. Higher doses and SC administration of MTX produced higher levels of total MTXPGs and selective accumulation of longer-chain MTXPGs (P < 0.001 and P < 0.0001, respectively).ConclusionsNonadherence to MTX therapy is a significant problem in children with JIA and JDM. The present study suggests that patients with inadequate adherence and/or intolerance to oral MTX may benefit from SC administration of the drug. The clinical utility of MTXPG levels to monitor and optimise adherence to MTX in children has been demonstrated.Trial registrationISRCTN Registry identifier: ISRCTN93945409. Registered 2 December 2011.

Are methotrexate polyglutamate levels associated with response to methotrexate? A pilot study of 24 weeks

Are methotrexate polyglutamate levels associated with response to methotrexate? A pilot study of 24 weeks

THU0122 Effect of Two MTX Dosing Regimens on Intracellular MTX Accumulation in Rheumatoid Arthritis Patients

BackgroundLow-dose methotrexate (MTX) is gold standard in the treatment of rheumatoid arthritis (RA). Response to MTX is very variable and is related to the intracellular MTX-polyglutamate (MTX-PG) levels.1,2 Similar to...

AB0593 Subcutaneous methotrexate is more efficacious and better tolerated than oral methotrexate: The experience of a large group of patients in the rheumatology department of a district general hospital

BackgroundWith the emphasis in the management of inflammatory arthritis on early disease modification it is vital that prescribed treatments are tolerated and adhered to. Methotrexate can prove difficult for patients...

Methotrexate polyglutamation in relation to infliximab pharmacokinetics in rheumatoid arthritis

ObjectiveThe combination of methotrexate (MTX) with infliximab can modify infliximab pharmacokinetics and lower the incidence of antibodies against infliximab (ATIs). We hypothesised that the pharmacokinetic interaction between MTX and infliximab...

Understanding the variation in response to methotrexate

ORIGINAL ARTICLE, p 165 Methotrexate (MTX) has been used in the management of psoriasis since the 1960s and despite the increasing use and success of newer biologic agents, it remains a first‐line treatment in patients with moderate to severe psoriasis, due to its efficacy and cost‐effectiveness.1 It is used as a standard comparator in randomized controlled trials of biologic agents in psoriasis. However, a significant number of patients on MTX do not experience benefit and up to 30% of patients are unable to tolerate the drug because of toxicity including nausea, myelosuppression or hepatotoxicity.2 Reasons for this inter‐individual variability in both toxicity and response are partially unknown but may include demographic factors (such as patient age and weight), external or environmental influences (for instance adherence to treatment, drug dosage), and genetic variation in pharmacokinetics (for instance, drug metabolizing enzymes) or pharmacodynamics (drug targets). Pharmacogenetics is the study of those inherited factors that influence the inter‐individual variability in response to drugs and is a rapidly developing field. The pharmacokinetics and pharmacodynamics of MTX, as have recently been unravelled, have proved to be complicated, and early attempts at pharmacogenetic studies in both rheumatology and dermatology using a candidate gene approach have not been definitive. MTX is a pro‐drug which is actively transported into the cell via a transmembrane reduced folate carrier protein (SLC19A1) and actively exported from the cell by ATP‐binding cassette transporters ABCC1 and ABCG2. Polymorphisms in ABCC1 and ABCG2 have been found to correlate with a better response to MTX (with odds ratios of about 2) and polymorphisms in SLC19A1 and ABCC1 have been associated with MTX toxicity. Within the cell, MTX is activated by the sequential addition of between two and seven glutamic acid residues under the action of the enzyme folylpolyglutamate synthetase, thus converting the parent drug to the active and more stable polyglutamated form. MTX polyglutamates (MTXPGs) persist intracellularly, exerting a sustained effect which allows for its once‐weekly administration.3 Some studies of patients with rheumatoid arthritis have shown a correlation between intracellular MTXPG levels and MTX treatment efficacy.4, 5

Accumulation of methotrexate and methotrexate polyglutamates in lymphoblasts and treatment outcome in children with B-progenitor-cell acute lymphoblastic leukemia: a Pediatric Oncology Group study

We reported that children with B-progenitor-cell acute lymphoblastic leukemia (BpALL) treated in the early 1980s whose lymphoblasts accumulated high levels of methotrexate (MTX) and of methotrexate polyglutamates (MTXPGs) in vitro had an improved 5-year event-free survival (EFS) (65% (standard error (s.e.) 12%) vs 22% (s.e. 9%)). We repeated this study in children with BpALL treated in the early 1990s. The major change in treatment was the addition of 12 24-h infusions of 1 g/M2 MTX with leucovorin rescue (IDMTX). In 87 children treated on Pediatric Oncology Group (POG) study 9005 and POG 9006, the 5-year EFS for those whose lymphoblasts accumulated high levels of MTX and MTXPGs (79.2%, s.e. 8.3%) was not significantly different from that of patients with lesser accumulation of MTX and MTXPGs (77.7%, s.e. 5.4%). These findings support the notion that higher dose MTX therapy has contributed to increased cure, particularly for patients whose lymphoblasts accumulate the drug less well.

Contribution of common polymorphisms in reduced folate carrier and ??-glutamylhydrolase to methotrexate polyglutamate levels in patients with rheumatoid arthritis

We investigated whether polymorphisms in reduced folate carrier (SLC19A1 G80A) and gamma-glutamyl-hydrolase (GGH-401C/T) are predictive of methotrexate polyglutamate (MTXPG) levels in patients with rheumatoid arthritis treated with weekly low-dose methotrexate (MTX). Adult patients treated with MTX were enrolled in a multicentred study. Blood was drawn at the time of the visit, DNA was extracted and red blood cell (RBC) MTXPG levels (up to the penta-order of glutamation) were measured by high-performance liquid chromatography-fluorometry. A G80A polymorphism in SLC19A1 and a -401C/T promoter polymorphism in GGH were measured by polymerase chain reaction-restriction fragment length polymorphism. Multivariate linear and logistic regressions were used to predict long-chain RBC MTXPG3-5. In 226 adult patients receiving MTX (median 15 mg range: 5-25 mg) median RBC long-chain MTXPG3-5 was 56 nmol/l (range < 5-224 nmol/l). A total of 35 patients carried the SLC19A1 80AA genotype whereas 36 patients carried the GGH-401TT genotype. Weekly MTX dose, age, presence of the SLC19A1 80AA and GGH-401TT genotypes predicted independently and significantly MTXPG3-5 levels (global r = 0.38; P < 0.0001). Patients with the GGH-401TT genotype were 4.8-fold [odds ratio (OR) 95% confidence interval (CI) 1.8-13.0; P = 0.002] more likely to have MTXPG3-5 below the group median compared to patient carriers of the GGH-401CC or CT genotype. Conversely, those with the SLC19A1 80AA genotype were 3.4-fold more likely to have MTXPG3-5 levels above the group median compared to those with the SLC19A1 80GG or 80GA genotype (OR CI 95% 1.4-8.4; P = 0.007). These data demonstrate that polymorphisms in SLC19A1 and GGH affect polyglutamation of MTX.