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Background: Intracellular methotrexate polyglutamates (MTX-PGs) concentrations are measurable in red blood cells (RBCs) during MTX treatment. MTX-PG 3 concentrations correlate with efficacy in patients with Crohn's disease (CD). Since RBCs are not involved in pathogenesis of CD and lack extended MTX metabolism, we determined MTX-PGs accumulation in peripheral blood mononuclear cells (PBMCs: effector cells) and intestinal mucosa (target cells) and compared those with RBCs as a potential more precise biomarker., Methods: In a multicentre prospective cohort study, blood samples of patients with CD were collected during the first year of MTX therapy. Mucosal biopsies were obtained from non-inflamed rectum and/or inflamed intestine. MTX-PGs concentrations in mucosa, PBMCs and RBCs were measured by liquid chromatography-tandem mass spectrometry., Results: From 80 patients with CD, a total of 27 mucosal biopsies, 9 PBMC and 212 RBC samples were collected. From 12 weeks of MTX therapy onwards, MTX-PG 3 was the most predominant species (33%) in RBCs. In PBMCs, the distribution was skewed towards MTX-PG 1 (48%), which accounted for an 18 times higher concentration than in RBCs. Long-chain MTX-PGs were highly present in mucosa: 21% of MTX-PG total was MTX-PG 5 . MTX-PG 6 was measurable in all biopsies., Conclusions: MTX-PG patterns differ between mucosa, PBMCs and RBCs of patients with CD., (© 2024 The Author(s). Basic & Clinical Pharmacology & Toxicology published by John Wiley & Sons Ltd on behalf of Nordic Association for the Publication of BCPT (former Nordic Pharmacological Society).)

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., Competing Interests: Declarations of competing interest The authors have declared no conflicts of interest., (Copyright © 2024. Published by Elsevier B.V.)

Background and Purpose: Clinical studies showed that prolonged infusion of methotrexate (MTX) leads to more severe adverse reactions than short infusion of MTX at the same dose. We hypothesized that it is the saturation of folate polyglutamate synthetase (FPGS) at high MTX concentration that limits the intracellular synthesis rate of methotrexate polyglutamate (MTX-PG). Due to a similar accumulation rate, a longer infusion duration may increase the concentration of MTX-PG and, result in more serious adverse reactions. In this study, we validated this hypothesis., Experimental Approach: A549, BEL-7402 and MHCC97H cell lines were treated with MTX at gradient concentrations. Liquid chromatograph-mass spectrometer (UPLC-MS/MS) was used to quantify the intracellular concentration of MTX-PG and the abundance of FPGS and γ-glutamyl hydrolase (GGH). High quality data were used to fit the cell pharmacokinetic model., Key Results: Both cell growth inhibition rate and intracellular MTX-PG concentration showed a nonlinear relationship with MTX concentration. The parameter Vmax in the model, which represents the synthesis rate of MTX-PG, showed a strong correlation with the abundance of intracellular FPGS., Conclusion and Implications: According to the model fitting results, it was confirmed that the abundance of FPGS is a decisive factor limiting the synthesis rate of MTX-PG. The proposed hypothesis was verified in this study. In addition, based on the intracellular metabolism, a reasonable explanation was provided for the correlation between the severity of adverse reactions of MTX and infusion time. This study provides a new strategy for the individualized treatment and prediction of efficacy/side effects of MTX., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Tang et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Low-dose methotrexate (MTX) plays a key role in treatment of rheumatoid arthritis. However, not all patients respond satisfactorily, and no therapeutic drug monitoring has been implemented in clinical practice, despite the fact that MTX therapy has now been available for decades. Analysis of individual intracellular MTX metabolites among rheumatoid arthritis (RA) patients is hampered by the low intracellular concentrations of MTX-PGs which require a highly sensitive method to quantify. Here, we present a rapid and highly sensitive LC (HILIC) MS/MS method with LLOQ 0.1 nM, 0.8 nmol/L for each metabolite of MTX-PG 1-5 and MTX-PG 6-7 respectively. Over a linear range of 0.1-100 nM, 0.8-100 nmol/L for each metabolite of MTX-PG 1-5 and MTX-PG 6-7 , respectively, the inter- and intra- accuracy and precision were within 15% of the nominal value for all MTX metabolites. The presented assay was used to assess and compare MTX metabolite concentrations extracted from four different matrices: red blood cells, plasma, peripheral blood mononuclear cells, and whole blood that have been collected either using traditional venepuncture or volumetric absorptive micro-sampling (VAMS) sampling techniques. The presented method not only improves analyte coverage and sensitivity as compared to other published methods; it also improves the greenness., (© 2022. The Author(s).)

Low dose methotrexate (MTX) is commonly used in the treatment of rheumatoid arthritis. The clinical effect is mediated by its metabolite, methotrexate polyglutamate (MTX-PGn). The drug exhibits high interindividual pharmacokinetic variability and the optimal MTX dose is different among individuals. Thus, several MTX population pharmacokinetic (PopPK) models were developed to characterize factors affecting MTX pharmacokinetic variability. This review summarizes significant predictors for MTX pharmacokinetics and identifies knowledge gaps to be further examined. A total of 359 articles were identified from a systematic search of four databases: PubMed, Science Direct, and CINAHL Complete. Of these eight studies were included. Most studies investigated influential factors on MTX pharmacokinetics, but information on MTX-PGn is limited, with only one study performing a parent-metabolite (MTX-PG3) model. MTX pharmacokinetics was described using a two-compartment model with first-order elimination in most studies, with the MTX clearance ranging from 6.94 to 12.39 L/h. Significant predictors influencing MTX clearance included weight, creatinine clearance, sex, OATP1B3 polymorphism, and MTX multiple dosing. While body mass index and red blood cell counts were significant predictors for MTX-PG3 clearance. Providing that MTX-PGn plays a crucial role in clinical effect, further studies should determine other factors affecting MTX-PGn as well as its relationship with clinical response., (© 2022 Walter de Gruyter GmbH, Berlin/Boston.)

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.

Objectives: There are no head-to-head trials of different dose escalation strategies of methotrexate (MTX) in RA. We compared the efficacy, safety and tolerability of 'usual' (5 mg every 4 weeks) versus 'fast' (5 mg every 2 weeks) escalation of oral MTX., Methods: This multicentre, open-label (assessor blinded) RCT included patients 18-55 years of age having active RA with disease duration <5 years, and not on DMARDs. Patients were randomized 1:1 into usual or fast escalation groups, both groups starting MTX at 15 mg/week till a maximum of 25 mg/week. Primary outcome was EULAR good response at 16 weeks, secondary outcomes were ΔDAS28 and adverse effects (AE). Analyses were intention-to-treat., Results: 178 patients with mean DAS28-CRP of 5.4(1.1) were randomized to usual (n=89) or fast escalation groups (n=89). At 16 weeks, there was no difference in good EULAR response in the usual (28.1%) or fast escalation (22.5%) groups (p=0.8). There was no difference in mean ΔDAS28-CRP at 8 weeks (-0.9, -0.8, p=0.72) or 16 weeks (-1.3, -1.3, p=0.98). Even at 24 weeks (extended follow-up), responses were similar. There were no inter-group differences in ΔHAQ, or MTX-polyglutamates 1-3 levels at 8 or 16 weeks. Gastrointestinal AE were higher in the fast escalation group over initial 8 weeks (27%, 40%, p=0.048), but not over 16 weeks. There was no difference in cytopenias, transaminitis, or drug discontinuation/dose reduction between the groups. No serious AE were seen., Conclusion: A faster MTX escalation strategy in RA was not more efficacious over 16-24 weeks, and did not significantly increase AE, except higher gastrointestinal AE initially., Trial Registration Number: CTRI/2018/12/016549., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2021. No commercial re-use. See rights and permissions. Published by BMJ.)

Purpose: Osteonecrosis is a burdensome treatment-related toxicity that is mostly diagnosed during or soon after 6-mercaptopurine (6MP)/methotrexate (MTX) maintenance therapy for acute lymphoblastic leukemia (ALL), possibly indicating a pathogenic role of these drugs., Methods: We prospectively registered symptomatic osteonecrosis during treatment of 1234 patients aged 1.0-45.9 years treated according to the Nordic Society of Hematology and Oncology (NOPHO) ALL2008 protocol. MTX/6MP metabolites were measured as part of the NOPHO ALL2008 maintenance therapy study., Results: After a median follow-up of 5.6 years [interquartile range (IQR) 3.6-7.5], 68 patients had been diagnosed with symptomatic osteonecrosis. The cumulative incidence was 2.7% [95% confidence interval (CI) 1.6-3.8%] for patients aged < 10 years, 14.9% (95% CI 9.7-20.2%) for patients aged 10.0-17.9 years, and 14.4% (95% CI 8.0-20.8%) for patients aged ≥ 18 years. The median time from diagnosis of ALL to diagnosis of osteonecrosis in these age groups was 1.0 year (IQR 0.7-2.0), 2.0 years (IQR 1.1-2.4), and 2.2 years (IQR 1.8-2.8), respectively (p = 0.001). With 17,854 blood samples available for MTX and 6MP metabolite analysis, neither erythrocyte levels of 6-thioguanine (TG) nucleotides (p > 0.99), methylated 6MP metabolites (p = 0.37), MTX polyglutamates (p = 0.98) nor DNA-TG (p = 0.53) were significantly associated with the hazard of osteonecrosis in Cox models stratified by the three age groups and adjusted for sex., Conclusion: Maintenance therapy intensity determined by 6MP and MTX metabolites was not associated with the risk of developing osteonecrosis in the NOPHO ALL2008 cohort., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Methotrexate is the gold standard treatment in rheumatoid arthritis. Once absorbed, it is internalized in cells, where glutamate residues are added to produce polyglutamated forms, which are responsible for the effect of methotrexate. The aim of the current study is to determine the relationship between methotrexate triglutamate concentrations and the clinical evolution in rheumatoid arthritis patients, as well as to characterize the variability in both features to propose strategies for low-dose methotrexate optimization. The quantification of methotrexate triglutamate concentration in red blood cells was performed through ultra-performance liquid chromatography coupled with mass spectrometry. Polymorphisms of genes involved in the formation of polyglutamates were determined by real-time polymerase chain reaction. A multivariate regression was performed to determine the covariates involved in the variability of methotrexate triglutamate concentrations and a population pharmacokinetics model was developed through nonlinear mixed-effects modeling. Disease activity score changed according to methotrexate triglutamate concentrations; patients with good response to treatment had higher concentrations than moderate or nonresponding patients. The methotrexate triglutamate concentrations were related to time under treatment, dose, red blood cells, and body mass index. A 1-compartment open model was selected to estimate the pharmacokinetic parameters; the typical total clearance (L/day) was determined as 1.45 * (body mass index/28 kg/m 2 ) * (red blood cells/4.6 × 10 6 cells/μL) and the volume of distribution was 52.4 L, with an absorption rate of 0.0346/day and a fraction metabolized of 1.03%. Through the application of the model, the initial dose of methotrexate is proposed on the basis of stochastic simulations and considering methotrexate triglutamate concentrations found in responders patients., (© 2021, The American College of Clinical Pharmacology.)

We developed and validated a quantification method for methotrexate (MTX) polyglutamates (MTX-PGs, MTX-PG1 to MTX-PG5) by liquid chromatography-tandem mass spectrometry using stable isotope-labeled internal standards and applied to 196 clinical samples collected from pediatric acute lymphoblastic leukemia patients treated with MTX. MTX-PGs levels and their proportions (%) in sum of all MTX-PGs (MTXSum) were evaluated in relation to TPMT, NUDT15, and MTHFR genotypes. For the developed method, linearity ranges 1-500 nmol/L, bias for accuracy 0.3-13.5 %, coefficient of variation for within- and between-run imprecision of 3.2-9.5% and 1.5-12.0%, respectively. Recoveries achieved were 74.2-105.8 %. There was no significant carryover. The median level of the MTXSum for 196 clinical samples was 129.4 nmol/L (interquartile range 28.1-241.2). MTX dose and MTX-PGs were associated (P < 0.05) and among five MTX-PGs, MTX-PG3 was the predominant form (median 41.7 %). The MTX-PG3 level was significantly higher in patients with TPMT *1/*3C than in patients with wild type and MTX-PG3% was significantly higher and MTX-PG5% was significantly lower in NUDT15 intermediate metabolizers than normal or indeterminate phenotypes (P < 0.05). This validated MTX-PGs quantification method can facilitate a better understanding of MTX metabolism and therapeutic drug monitoring for MTX treatment., Competing Interests: Declaration of Competing Interest The authors report no declarations of interest., (Copyright © 2021. Published by Elsevier B.V.)

Objectives: The aim of the study was to explore the effect of total glucosides of paeony (TGP) and Tripterygium wilfordii polyglycosides (TWP) on erythrocyte methotrexate polyglutamates (MTXPGs), the metabolites of methotrexate (MTX)., Methods: An ultra-high-performance liquid chromatography (UPLC)-tandem mass spectrometry (MS/MS) method was developed to determine MTXPGs. The effects of MTXPGs were analysed using 24 male Sprague-Dawley rats that were randomly divided into the MTX alone, MTX-TGP combined, and MTX-TWP combined groups. Rats were administered MTX at a dose of 0.9 mg/kg once a week, TGP at 0.054 g/kg and TWP at 1.8 mg/kg three times a day. Venous blood (1.0 ml) was collected at weeks 2, 4, 6, 9, 12 and 15 and then analysed using the developed UPLC-MS/MS method., Key Findings: Specificity, linear range, inter-and intra-day precision, recovery, matrix effect and stability of MTXPGs met the standard regulations. This method was successfully used for the detection of MTXPGs. After administration of MTX alone, erythrocyte MTXPGs increased and accumulated in a time- and dose-dependent manner. Compared to MTX alone, the combination with TGP significantly decreased the content of total MTXPGs and short-chain MTXPGs (Methotrexate [MTX/MTXPG1] and 4-amino-10-methylpteroyldiglutamic acid [MTXPG2], P < 0.05), but had no significant effect on long-chain MTXPGs (4-amino-10-methylpteroyltriglutamic acid [MTXPG3], P > 0.05) and very long-chain MTXPGs (4-amino-10-methylpteroyltetraglutamic acid [MTXPG4] and 4-amino-10-methylpteroylpentaglutamic acid [MTXPG5], P > 0.05) at week 15. The combination of MTX with TWP had no significant effect on the content of total MTXPGs, short-chain MTXPGs and long-chain MTXPGs (P > 0.05), but it significantly decreased the content of very long-chain MTXPGs (P < 0.05) at week 15., Conclusions: The UPLC-MS/MS method was successfully used to determine MTXPGs in rat erythrocytes. TGP and TWP in combination with MTX affected the production of MTXPGs of different chain lengths in erythrocytes., (© The Author(s) 2021. Published by Oxford University Press on behalf of the Royal Pharmaceutical Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Objectives: 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., Method: 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., Results: 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)]., Conclusions: 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., Clinical Trial Registration: NCT01594333., (© The Author(s) 2020. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Low-dose methotrexate is the first-line therapy for juvenile idiopathic arthritis. In vivo, methotrexate is converted into a series of methotrexate polyglutamates whose intracellular levels contribute significantly to its efficacy and toxicity. In this study, a novel high-performance liquid chromatography-tandem mass spectrometry method was developed and validated to simultaneously determine erythrocyte methotrexate polyglutamates using stable isotope-labeled internal standards. Erythrocyte samples were precipitated by perchloric acid and then determined on an XBridge BEH C18 column with an XP vanguard precolumn in 12 min. The mobile phase consisted of 10 nM ammonium acetate (pH 10) and methanol under gradient elution. The detection was carried out in multiple reaction monitoring mode via an electrospray ionization source in positive ionization mode. The calibration curve for each metabolite was linear from 2.0 to 500.0 nmol/L (r 2  > 0.99). The intraday and interday accuracies were between 93.0 and 107.0%, and the corresponding precisions were between 0.8 and 5.2%. The relative recovery ranged from 82.7 to 105.1%, and the relative matrix effect varied from 96.5 to 104.4%. The erythrocyte metabolites were stable for 30 days at -80°C. This simple and accurate method is applicable to routine monitoring of the concentration of erythrocyte methotrexate polyglutamates in patients to achieve individualized treatment., (© 2021 Wiley-VCH GmbH.)

High-dose methotrexate (HDMTX) combined with leucovorin (LV) is the first-line drug therapy for many kinds of malignant tumors. However, the specific treatment plans, such as dosage and duration of administration, are usually formulated according to the clinician's experience and therapeutic drug monitoring (TDM) of methotrexate in patients' plasma, which are responsible for strong individual differences of drug usage. A large number of studies have shown that methotrexate targets the inside of the cell. The key cytotoxic component is the methotrexate polyglutamates (MTXPGs) in the cell. The concentration of methotrexate in plasma does not reflect the efficacy and side effects well. Based on mass spectrometry technology, we developed and validated an accurate, sensitive, and stable method to quantify the intracellular MTX (MTXPG 1 ) and its metabolites MTXPG 2-7 simultaneously. The lower limit of quantification was 0.100 ng/ml, and the run time was only 3 min. Moreover, our team has already developed two LC-MS/MS-based methods to respectively quantify methotrexate in plasma samples and two key proteins (γ-glutamyl hydrolase [GGH] and folylpolyglutamate synthetase [FPGS]) in peripheral blood mononuclear cells (PBMC). Through these highly sensitive and accurate approaches, we have gained a deep understanding of the whole pharmacokinetic process of MTX and explored the key factors affecting the accumulation process of intracellular active components (MTXPGs). Based on this research, it is possible to find a more effective way to provide an accurate reference for clinical drug use than traditional therapeutic drug monitoring (TDM).

Drug-induced nephrotoxicity is a frequent adverse event that contributes to acute kidney injury with tubular and/or glomerular lesions. Methotrexate (MTX) is a folate analog used against a myriad of malignancies and autoimmune diseases. Unfortunately, ambiguous renal toxicology limits its safe clinical usage. Based on our previous studies, 7-OH MTX as an overlooked oxidative metabolite of MTX was proposed to be the main culprit responsible for nephrotoxicity, while nobiletin, a naturally occurring polymethoxylated flavonoid screened from our prepared total phenolic extracts of Citrus aurantium L. (TPE-CA), was employed as a therapeutic agent for drug-drug interactions. According to the present study, nobiletin can ameliorate the renal accumulation of 7-OH MTX through the interaction with aldehyde oxidase. RNA-seq analysis revealed that 7-OH MTX was mainly related to protein processing in endoplasmic reticulum (ER) stress, with the PERK/CHOP pathway selected as the most significant for metabolic nephrotoxicity. Meanwhile, the cross-linked proteins and conducted signals were investigated by western blotting and further verified by GSK inhibition analyses. These results indicated that nobiletin protected renal function from MTX-induced nephrotoxicity by modulating metabolism and ameliorated the metabolic toxicity of 7-OH MTX on ER stress-induced PERK/CHOP conduction by maintaining Ca 2+ homeostasis and reducing the production of reactive oxygen species., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Nephrotoxicity, the most important toxicity in high-dose methotrexate (MTX) therapy, is partly caused by the formation of crystal deposits in the kidney due to poor water solubility of MTX and its metabolites 7-hydroxy methotrexate (7-OH MTX), deoxyaminopteroic acid (DAMPA) and 7-hydroxy deoxyaminopteroic acid (7-OH DAMPA). Plasma MTX level-guided urine alkalinization, leucovorin rescue and glucarpidase detoxification are common strategies to overcome MTX-related nephrotoxicity. However, overestimation is a problem for MTX analysis by immunoassays due to the cross-reactivity of MTX metabolites (7-OH MTX and DAMPA). An UHPLC-MS/MS method for the simultaneous determination of MTX, 7-OH MTX, DAMPA and 7-OH DAMPA in human urine was developed, validated and applied in clinical practice. Samples were treated by one-step protein precipitation and analyzed within 3 min. The calibration range was 0.02 to 4 μmol/L for MTX and DAMPA, and 0.1 to 20 μmol/L for 7-OH MTX and 7-OH DAMPA. For all analytes, the intra-day and inter-day bias and imprecision were -8.0 to 7.6 and <9.0%, the internal standard normalized recovery and matrix factor were 92.34 to 109.49 and <20.68%. The plasma MTX and 7-OH MTX levels increased with the urine drug levels, age, serum creatinine and alanine transaminase, but urine could not replace blood for MTX monitoring due to their poor correlation (R 2 , 0.16 to 0.51). Dose-normalized urine and plasma MTX and 7-OH MTX levels were similar between different patient groups (urine pH <7 or ≥7). Due to the large inter-individual variance of the analytes levels in both plasma and urine, these findings should be treated with caution.

BACKGROUNDInterpatient differences in the accumulation of methotrexate's active polyglutamylated metabolites (MTXPGs) in leukemia cells influence its antileukemic effects.METHODSTo identify genomic and epigenomic and patient variables determining the intracellular accumulation of MTXPGs, we measured intracellular MTXPG levels in acute lymphoblastic leukemia (ALL) cells from 388 newly diagnosed patients after in vivo high-dose methotrexate (HDMTX) (1 g/m2) treatment, defined ALL subtypes, and assessed genomic and epigenomic variants influencing folate pathway genes (mRNA, miRNA, copy number alterations [CNAs], SNPs, single nucleotide variants [SNVs], CpG methylation).RESULTSWe documented greater than 100-fold differences in MTXPG levels, which influenced its antileukemic effects (P = 4 × 10-5). Three ALL subtypes had lower MTXPG levels (T cell ALL [T-ALL] and B cell ALL [B-ALL] with the TCF3-PBX1 or ETV6-RUNX1 fusions), and 2 subtypes had higher MTXPG levels (hyperdiploid and BCR-ABL like). The folate pathway genes SLC19A1, ABCC1, ABCC4, FPGS, and MTHFD1 significantly influenced intracellular MTXPG levels (P = 2.9 × 10-3 to 3.7 × 10-8). A multivariable model including the ALL subtype (P = 1.1 × 10-14), the SLC19A1/(ABCC1 + ABCC4) transporter ratio (P = 3.6 × 10-4), the MTX infusion time (P = 1.5 × 10-3), FPGS mRNA expression (P = 2.1 × 10-3), and MTX systemic clearance (P = 4.4 × 10-2) explained 42% of the variation in MTXPG accumulation (P = 1.1 × 10-38). Model simulations indicated that a longer infusion time (24 h vs. 4 h) was superior in achieving higher intracellular MTXPG levels across all subtypes if ALL.CONCLUSIONSThese findings provide insights into mechanisms underlying interpatient differences in intracellular accumulation of MTXPG in leukemia cells and its antileukemic effectsFUNDINGTHE National Cancer Institute (NCI) and the Institute of General Medical Sciences of the NIH, the Basque Government Programa Posdoctoral de Perfeccionamiento de Personal Investigador doctor, and the American Lebanese Syrian Associated Charities (ALSAC).

Methotrexate (MTX) during maintenance therapy is essential for curing acute lymphoblastic leukemia (ALL), but dosing strategies aiming at adequate treatment intensity are challenged by interindividual differences in drug disposition. To evaluate genetic factors associated with MTX metabolism, we performed a genome-wide association study in 447 ALL cases from the Nordic Society for Pediatric Haematology and Oncology ALL2008 study, validating results in an independent set of 196 patients. The intergenic single-nucleotide polymorphism rs1382539, located in a regulatory element of DHFR, was associated with increased levels of short-chain MTX polyglutamates (P = 1.1 × 10-8) related to suppression of enhancer activity, whereas rs35789560 in FPGS (p.R466C, P = 5.6 × 10-9) was associated with decreased levels of long-chain MTX polyglutamates through reduced catalytic activity. Furthermore, the FPGS variant was linked with increased relapse risk (P = .044). These findings show a genetic basis for interpatient variability in MTX response and could be used to improve future dosing algorithms., (© 2020 by The American Society of Hematology.)

Drug resistance is a core issue in cancer chemotherapy. A known folate antagonist, methotrexate (MTX) inhibits human dihydrofolate reductase (hDHFR), the enzyme responsible for the catalysis of 7,8-dihydrofolate reduction to 5,6,7,8-tetrahydrofolate, in biosynthesis and cell proliferation. Structural change in the DHFR enzyme is a significant cause of resistance and the subsequent loss of MTX. In the current study, wild type hDHFR and double mutant (engineered variant) F31R/Q35E (PDB ID: 3EIG) were subject to computational study. Structure-based pharmacophore modeling was carried out for wild type (WT) and mutant (MT) (variant F31R/Q35E) hDHFR structures by generating ten models for each. Two pharmacophore models, WT-pharma and MT-pharma, were selected for further computations, and showed excellent ROC curve quality. Additionally, the selected pharmacophore models were validated by the Guner-Henry decoy test method, which yielded high goodness of fit for WT-hDHFR and MT-hDHFR. Using a SMILES string of MTX in ZINC 15 with the selections of 'clean', in vitro and in vivo options, 32 MTX-analogs were obtained. Eight analogs were filtered out due to their drug-like properties by applying absorption, distribution, metabolism, excretion, and toxicity (ADMET) assessment tests and Lipinski's Rule of five. WT-pharma and MT-pharma were further employed as a 3D query in virtual screening with drug-like MTX analogs. Subsequently, seven screening hits along with a reference compound (MTX) were subjected to molecular docking in the active site of WT- and MT-hDHFR. Through a clustering analysis and examination of protein-ligand interactions, one compound was found with a ChemPLP fitness score greater than that of MTX (reference compound). Finally, a simulation of molecular dynamics (MD) identified an MTX analog which exhibited strong affinity for WT- and MT-hDHFR, with stable RMSD, hydrogen bonds (H-bonds) in the binding site and the lowest MM/PBSA binding free energy. In conclusion, we report on an MTX analog which is capable of inhibiting hDHFR in wild type form, as well as in cases where the enzyme acquires resistance to drugs during chemotherapy treatment.

Objective: To discuss the application value of the simultaneous determination of methotrexate (MTX) and 7-hydroxymethotrexate (7-OHMTX) in the delayed elimination of MTX for pediatric acute lymphoblastic leukemia (ALL). Methods: Cross sectional study. A total of 97 children who received 192 high-dose MTX treatments cycles in Lu Daopei Hospital from April to August 2019 were enrolled. The peripheral blood was collected at 0,24,48 h after the end of MTX infusion and analyzed by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). One hundred and ninety-two MTX treatments were divided into a normal MTX elimination group ( n= 149) and delayed elimination group ( n= 43) according to the standard of delayed elimination and divided into 0-9 year old group ( n= 95), 10-14 group ( n= 50), 15-18 group ( n= 47) according to age. The comparisons of the C(MTX), C(7-OHMTX) between normal and delayed group was conducted as well as among different age groups. Receiver operator characteristic curve (ROC) of C(MTX-0h) and C(7-OHMTX-0h) was analyzed and the concentration corresponding to the maximum of the Youden index on the ROC was set as the warning value for delayed elimination. Correlation between the delayed elimination after the end of MTX infusion and toxicity was investigated and the percentage of delayed elimination was also analyzed. Results: The concentrations of MTX and 7-OHMTX were significantly higher in the delayed elimination group than the normal group. Immediately after infusion (0 h), a C(7-OHMTX-0h) of >17.8 μmol/L (sensitivity 97.7%, specificity 54.4%) and a C(MTX-0h) of >148.8 μmol/L (sensitivity 72.1%, specificity 84.6%) were found to be warning predictors of delayed elimination under the MTX treatment protocol. MTX delayed elimination was positively correlated with methotrexate-induced toxicities ( r= 0.58, P< 0.01). The percentage of hepatotoxicity and nephrotoxicity was 32.6% and 37.2% in the delayed elimination group, which was significantly higher than normal group of 12.8% and 3.4% ( P< 0.05). No significant difference was found in other toxicities. There was significant difference in C(MTX) among different age groups but no significant difference in C(7-OHMTX). Conclusion: Simultaneously determination of MTX and 7-OHMTX in plasma by HPLC-MS/MS in childhood ALL patients can provide a reference for clinical individualized medicine and pharmacokinetic research.

Genetic variants influencing the pharmacokinetics and/or pharmacodynamics of the chemotherapeutic drugs used in Acute Lymphoblastic Leukemia (ALL) therapy often contribute to the occurrence of treatment related toxicity (TRT). In this study, we explored the association of candidate genetic variants with early hematological TRT (grade 3-4) occurring within the first 100 days of low-dose methotrexate and 6-mercaptopurine based maintenance therapy (n = 73). Fourteen variants in the following candidate genes were genotyped using allele discrimination assay by real-time PCR: ABCB1 , DHFR , GGH , FPGS , MTHFR , RFC1 , SLCO1B1 , TPMT , and NUDT15 . Methotrexate polyglutamate (MTXPG3-5) levels in red blood cells were measured by LC-MS/MS. Early hematological TRT (grade 3-4) was seen in 54.9% of patients. The NUDT15 *3 allele was associated with early TRT occurrence [HR: 3.04 (95% CI: 1.5-6.1); p = 0.007]. Sensitivity of early TRT prediction improved (from 30.7% to 89.7%) by considering FPGS variant (rs1544105) carrier status along with NUDT15 *3 allele [HR = 2.7 (1.5-4.7, p = 0.008)]. None of the considered genetic variants were associated with MTXPG3-5 levels, which in turn were not associated with early TRT. NUDT15 *3 allele carrier status could be used as a stratifying marker for Indian ALL patients to distinguish patients at high or low risk of developing early hematological TRT.

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 Method s : 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-PG 5 . 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., Competing Interests: The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Inadequate adherence to maintenance therapy is a major cause of relapse in patients with acute lymphoblastic leukemia (ALL). Therapeutic monitoring of mercaptopurine (thiopurine) red cell metabolites to assess adherence has been available for many years. Recently a clinical laboratory improvement amendments of 1988-approved test for methotrexate with three polyglutamate residues (MTXPG3) measured in peripheral blood red cells was approved. MTXPG3 is the primary intracellular metabolite of methotrexate, and like thiopurine metabolites, is retained for the life of the red cell giving an estimate of drug exposure over time. Normative values for MTXPG3 are available for adults and children with rheumatoid arthritis on methotrexate monotherapy, which are not applicable for patients with ALL on maintenance. Older literature on the MTXPG3 fraction in children with ALL is limited. We examined the MTXPG3 levels from 123 samples in 76 patients with ALL on maintenance oral methotrexate and mercaptopurine that were collected for clinical care. Male individuals had significantly higher MTXPG3 levels than female individuals which was unrelated to absolute neutrophil count, age, serum creatinine, and average doses of methotrexate or mercaptopurine. The MTXPG3 5th, 10th, 90th, and 95th percentile values are 0, 8.4, 53, and 64, respectively with a median of 24.7 nmol/L. The low 5th percentile MTXPG3 reflects 6 samples from 3 patients, age 16 to 21 years that were considered poorly adherent before collecting the specimen. As with red cell thiopurine (mercaptopurine) metabolites, MTXPG3 normative values may provide useful information to monitor for poor patient adherence or methotrexate toxicity during maintenance chemotherapy in ALL.

Objective: Methotrexate (MTX) polyglutamate (MTXPG 3 ) levels from isolated red blood cells (RBCs) collected by venipuncture have clinical utility in guiding MTX dosing for patients with rheumatoid arthritis (RA). Our objective was to transition this RBC-based therapeutic drug monitoring (TDM) assay to dried capillary blood collected by fingerstick., Methods: Patients with RA treated with MTX were enrolled. Specimens were collected by fingerstick (volumetric absorptive microsampler) and venipuncture to measure MTXPG 3 from dried capillary blood, total venous blood, and isolated RBCs. MTXPG 3 levels from dried capillary blood were measured using LC-MS/MS, converted to RBC equivalent (nmol/L), and compared with those from isolated RBCs (reference method). Following transition to fingerstick collection, comparability in the distributions of dried capillary and venipuncture-based RBC MTXPG 3 levels was assessed using the Kolmogorov-Smirnov (K-S) test., Results: Intraday and interday precision ranged from 2.0% to 10.9% and 3.1% to 10.8%, respectively, at MTXPG 3 concentrations ranging from 5 to 100 nmol/L. In 106 participants treated with MTX, MTXPG 3 levels from total venous and dried capillary blood were comparable [slope = 0.97 (95% CI, 0.92-1.03); R 2 = 0.92]. Dried capillary blood MTXPG 3 converted to RBC equivalent was similar to levels from isolated RBCs (30 ± 18 nmol/L vs 33 ± 19 nmol/L; n = 106). After implementation in the clinical laboratory, RBC equivalents MTXPG 3 from the fingerstick method were similar to levels from venipuncture [39 ± 22 nmol/L (n = 825) vs 39 ± 24 nmol/L (n = 47935)] (K-S test P = 0.09). Underexposure to MTX (MTXPG 3 ≤5 nmol/L RBCs) was detected in 7.0% and 8.5% patient specimens collected using the fingerstick and venipuncture methods, respectively., Conclusion: Capillary blood MTXPG 3 levels can be used to guide MTX dosing in TDM practice., (© 2018 American Association for Clinical Chemistry.)

Photopharmacology has attracted research attention as a new tool for achieving optical control of biomolecules, following the methods of caged compounds and optogenetics. We have developed an efficient photopharmacological inhibitor-azoMTX-for Escherichia coli dihydrofolate reductase (eDHFR) by replacing some atoms of the original ligand, methotrexate, to achieve photoisomerization properties. This fine molecular design enabled quick structural conversion between the active "bent" Z isomer of azoMTX and the inactive "extended" E isomer, and this property afforded quantitative control over the enzyme activity, depending on the wavelength of irradiating light applied. Real-time photoreversible control over enzyme activity was also achieved., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Chemoresistance is an important factor in the treatment failure of childhood acute lymphoblastic leukemia (ALL). One underlying mechanism of chemoresistance involves (over)expression of ATP-dependent drug efflux transporters such as multidrug resistance protein 1-5 (MRP1-5) and breast cancer resistance protein (BCRP), which can extrude the important antileukemia drug methotrexate (MTX). Survival of childhood ALL critically depends on the leukemic blasts' capacity for intracellular retention of MTX and MTX-polyglutamates. This pilot study assessed whether expression of MRP1, MRP4, MRP5 and BCRP (real-time PCR) in primary childhood ALL blasts (n = 23) correlated with ex vivo resistance to MTX (assayed by in situ thymidylate synthase inhibition assay (TSIA)), ex vivo accumulation of (radioactive) MTX polyglutamates, and patient survival. Results show that high MRP4 expression is correlated with ex vivo MTX resistance assayed by TSIA (P = 0.01). Moreover, elevated MRP4 and BCRP expression correlated with lower accumulation of MTX-PGs (P = 0.004 and P = 0.03, respectively). Combined high expression of BCRP and MRP4 even further impacted reduced MTX-PG accumulation (P = 0.02). Overall survival was lower (P logrank = 0.04) in children with ALL cells which featured a relatively high expression of both BCRP and MRP4 transporters. These results underscore the impact of high drug efflux transporter expression, notably MRP4 and BCRP, in diminished MTX response in childhood ALL., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The nutrient-sensing metabolite S-adenosylmethionine (SAM) controls one-carbon metabolism by donating methyl groups to biochemical building blocks, DNA, RNA, and protein. Our recent work uncovered a requirement for cytoplasmic arginine methylation during Wnt signaling through the activity of protein arginine methyltransferase 1 (PRMT1), which transfers one-carbon groups from SAM to many protein substrates. Here, we report that treatments that decrease levels of the universal methyl donor SAM were potent inhibitors of Wnt signaling and of Wnt-induced digestion of extracellular proteins in endolysosomes. Thus, arginine methylation provides the canonical Wnt pathway with metabolic sensing properties through SAM. The rapid accumulation of Wnt-induced endolysosomes within 30 minutes was inhibited by the depletion of methionine, an essential amino acid that serves as the direct substrate for SAM production. We also found that methionine is required for GSK3 sequestration into multivesicular bodies through microautophagy, an essential step in Wnt signaling activity. Methionine starvation greatly reduced Wnt-induced endolysosomal degradation of extracellular serum proteins. Similar results were observed by addition of nicotinamide (vitamin B3), which serves as a methyl group sink. Methotrexate, a pillar in the treatment of cancer since 1948, decreases SAM levels. We show here that methotrexate blocked Wnt-induced endocytic lysosomal activity and reduced canonical Wnt signaling. Importantly, the addition of SAM during methionine depletion or methotrexate treatment was sufficient to rescue endolysosomal function and Wnt signaling. Inhibiting the Wnt signaling pathway by decreasing one-carbon metabolism provides a platform for designing interventions in Wnt-driven disease., Competing Interests: The authors declare no conflict of interest., (Copyright © 2019 the Author(s). Published by PNAS.)

Purpose: 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., Methods and Results: 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 r s  = 0.68 and r s  = 0.25-0.42, respectively. Intercorrelations of MTXpg3,4,5,6 were all r s  ≥ 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., Conclusions: 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.

Methotrexate (MTX), an antifolate, is the anchor drug for the treatment of rheumatoid arthritis (RA). It is inexpensive, effective, and generally safe. When clinical response is inadequate, biological therapies are commonly used in combination with MTX. However, biological agents have safety concerns (i.e. infections, malignancy) and the addition of a biologic agent is expensive, making strategies to improve MTX efficacy important. Inhibition of pathways of folate metabolism involving purine metabolism by MTX, have been traditionally emphasized as important in MTX efficacy. However, inhibition MTX catabolism may also be important. MTX is irreversibly hydroxylated to form 7-hydroxy methotrexate (7-OH-MTX) by aldehyde oxidase (EC 1.2.3.1) (AOX). Catabolism of MTX to 7-OH-MTX is the first metabolic process imposed on an oral dose of MTX and will alter subsequent interactions of MTX with other enzymes. 7-OH-MTX is less potent than MTX in the treatment of rat adjuvant arthritis. RA patients with a low capacity to catabolize MTX to 7-OH-MTX do better clinically than individuals who are rapid formers of 7-OH-MTX. Therefore, altering the catabolism of MTX may be an innovative way to improve MTX efficacy. Raloxifene is a FDA-approved therapy for postmenopausal osteoporosis and for the reduction of invasive breast cancers but has no known activity in RA. Raloxifene is a potent inhibitor of human liver AOX. Postmenopausal women with RA frequently have low bone mineral density and would be candidates for raloxifene and MTX combination therapy. The effect of raloxifene on MTX metabolism has never been studied. Our hypothesis is that in postmenopausal women with RA and osteoporosis treated with MTX and raloxifene, the inhibition of AOX with resultant decreased formation of 7-OH MTX; will increase MTX levels and improve MTX efficacy. This hypothesis could be studied in an open-label, proof of concept clinical study in individuals before and after the addition of raloxifene. Red blood cell MTX and 7-OH-MTX levels and RA disease activity (DAS28) would be measured. In possible future studies, there are dietary substances, as supplements, (e.g. epigallocatechin gallate in green tea and resveratrol) which inhibit human liver AOX which could be evaluated., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The folate antagonist methotrexate is a cytotoxic drug used in the treatment of several cancer types. The entry of methotrexate into the cell is mediated by two main transport systems: the reduced folate carrier and membrane-associated folate receptors. These transporters differ considerably in their mechanism of (anti)folate uptake, substrate specificity, and tissue specificity. Although the mechanism of action of the reduced folate carrier is fairly well-established, that of the folate receptor has remained unknown. The development of specific folate receptor-targeted antifolates would be accelerated if additional mechanistic data were to become available. In this work, we used two fluorescently labeled conjugates of methotrexate, differently linked at the terminal groups, to clarify the uptake mechanism by folate receptor-α. The results demonstrate the importance of methotrexate amino groups in the interaction with folate receptor-α.

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 25 mg per week) for 24 weeks 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 polyglutamate 1-5 (MTX-glu 1-5 ) levels were determined at 4, 8, 16, and 24 weeks 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 24 weeks was 22.0 ± 4.0 mg, with data on DAS28(3) at 24 weeks 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-glu 1-5 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-glu 1-5 levels.

Background: High-dose methotrexate (HDMTX) therapy is a key component of many chemotherapy protocols. However, some patients develop HDMTX-induced nephrotoxicity. Carboxypeptidase-G2 (CPDG2) hydrolyses MTX into 2,4-diamino-N10-methylpteroic acid (DAMPA) and glutamic acid, and is used as a rescue agent in patients with nephrotoxicity and delayed elimination. Despite the frequency of HDMTX-induced renal injury, crystalluria is uncommon. Furthermore, crystals are rarely identified by conventional chemical methods., Objective: To determine the composition of crystalluria in a patient with osteosarcoma who was treated with CPDG2., Methods: Crystalluria was evaluated by optical microscopy, and chemical identification was performed by Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and Orbitrap™ high-resolution mass spectrometry (HRMS)., Results: The HRMS spectra of the patient's urine sediment showed a main peak at m/z 326.13, corresponding to the molecular mass of DAMPA [(C 15 H 15 O 2 N 7 ) + H + ]. The FT-IR spectral patterns of the sediment and DAMPA were not identical. SEM was unable to identify the crystal., Conclusion: DAMPA crystalluria was identified by Orbitrap™ HRMS in a patient treated with CPDG2 after HDMTX nephrotoxicity. This case reinforces the need to implement adequate measures to prevent nephrotoxicity. In cases of HDMTX-induced nephrotoxicity, urine sediment analysis should be requested., (Copyright © 2018. Published by Elsevier B.V.)

The efficacy and tolerability of systemically administered anticancer agents are limited by their off-target effects. Precise spatiotemporal control over their cytotoxic activity would allow improving chemotherapy treatments, and light-regulated drugs are well suited to this purpose. We have developed phototrexate, the first photoswitchable inhibitor of the human dihydrofolate reductase (DHFR), as a photochromic analogue of methotrexate, a widely prescribed chemotherapeutic drug to treat cancer and psoriasis. Quantification of the light-regulated DHFR enzymatic activity, cell proliferation, and in vivo effects in zebrafish show that phototrexate behaves as a potent antifolate in its photoactivated cis configuration and that it is nearly inactive in its dark-relaxed trans form. Thus, phototrexate constitutes a proof-of-concept to design light-regulated cytotoxic small molecules and a step forward to develop targeted anticancer photochemotherapies with localized efficacy and reduced adverse effects.

The plasma concentrations of methotrexate (MTX) and its major metabolite 7-hydroxy methotrexate (7-OH-MTX) are highly correlated with the toxicities in patients with high-dose MTX therapy. Routine monitoring of MTX and 7-OH-MTX plasma levels is useful for dose adjustment of rescue drugs and toxicity prevention. A UHPLC-MS/MS method for simultaneous determination of plasma MTX and 7-OH-MTX was developed, validated, and applied in 181 plasma samples. The ion transition was m/z 455.2 → 308.2 for MTX and m/z 471.2 → 324.1 for 7-OH-MTX. The flow rate was 0.4 mL/min with a run time of 2.6 min. The calibration range was 0.002-2 μM for MTX, and 0.01-10 μM for 7-OH-MTX. The intra-day and inter-day inaccuracy and imprecision were -5.50% to 10.93% and less than 9.20% for both analytes. The internal standard (MTX-D 3 ) normalized recovery and matrix factor were consistent at four quality control levels. 14 h, 38 h, and 62 h after dosing, MTX and 7-OH-MTX plasma levels were significantly higher in patients with impaired renal function compared to those with normal renal function. 7-OH-MTX plasma levels were significantly higher in patients with impaired liver function compared to those with normal liver function., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Methotrexate (MTX) is the standard of care in the treatment of rheumatoid arthritis (RA), a common autoimmune disease that is characterized by chronic inflammation in the synovial membrane of joints. Unfortunately, MTX suffers from high discontinuation rates due to a large variability in efficacy and, in particular, adverse effects. As inflammation is associated with elevated levels of reactive oxygen species (ROS) like H 2 O 2 , we propose to improve treatment through site-selective delivery of MTX to inflammatory tissue by use of a H 2 O 2 sensitive MTX prodrug. To establish proof proof-of-concept, two novel H 2 O 2 sensitive, thiazolidinone-based MTX prodrugs were synthesized and evaluated for this purpose. MTX-γ-thiazolidinone (MTX-γ-TZ) exhibited the most promising properties - good to high chemical and metabolic stability, excellent aqueous solubility, while being activated when subjected to patho-physiological concentrations of H 2 O 2 . In vivo, MTX-γ-TZ exhibited comparable efficacy to MTX in a murine collagen type II-induced arthritis (CIA) model while treated mice showed indications of reduced toxicity as their body weight decreased less towards the end of the study, compared to the MTX-treated group., (Copyright © 2018 Elsevier Masson SAS. All rights reserved.)

Background: Morbidly placenta accreta as a cause of postpartum morbidity is increasing in incidence. One conservative option is use of methotrexate as an adjuvant therapy for the management of placenta accreta. There is concern that use of methotrexate in a lactating mother could potentially expose her neonate to harmful effects of this medication., Case Report: Here we report a 29-year-old woman subjected to methotrexate treatment for placenta accreta. Her child was delivered at 32 weeks weighing 3 lbs. On postpartum day 5, this patient was diagnosed with placenta accreta and treated with intramuscular methotrexate for 3 consecutive days. She received 92 mg methotrexate intramuscularly daily, and was advised not to breastfeed. She collected milk samples on day 2, the 0 hour before the second dose and at 1, 2, 4, 8, 12, and 24 hours after taking the dose. A high-performance liquid chromatography mass spectrometry method was developed to measure methotrexate and its metabolite 7-hydroxymethotrexate levels in milk samples., Discussion: Very low levels were found for both methotrexate and 7-hydroxymethotrexate in the milk samples obtained. The results indicate that methotrexate or its metabolite receded to minimum concentration over a period of 24 hours., Conclusion: This case report found the relative infant dose of methotrexate to be 0.11%. Methotrexate does transfer into breast milk, although the levels detected were very low. However, caution should still be used in counseling mothers regarding breastfeeding with this toxic drug.

Methotrexate (MTX) is the gold standard drug for the treatment of rheumatoid arthritis (RA), and it is frequently combined with leflunomide (LEF) to enhance its clinical efficacy. However, this combination can exacerbate liver toxicity, and the underlying mechanism has not yet been clarified. We investigated whether LEF affects the pharmacokinetics of MTX and its primary toxic metabolite, 7-hydroxyl methotrexate (7OH MTX), in mice. LEF significantly increased the plasma concentration (area under the plasma concentration-time curve) of MTX and 7OH MTX (2.4 and 4.5 times, respectively), decreased their bile excretion, and increased their accumulation in the liver and kidneys. When we investigated the effect of LEF on the MTX absorption, distribution, metabolism, and excretion process, we found that LEF had little effect on liver aldehyde oxidase and 7OH MTX formation. However, LEF significantly decreased the expression of the apical efflux transporter multidrug resistance-associated protein 2 (Mrp2) and increased that of the basolateral efflux transporters Mrp3/4, except there was no significant change in Mrp4 protein expression. Mrp2/3/4 alteration changed the distribution of MTX and 7OH MTX in plasma and tissues. Further studies suggested that LEF indirectly activated peroxisome proliferator-activated receptor α (PPAR α ), which was likely responsible for the Mrp2/3/4 alteration in the liver. The MTX plasma concentration change induced by LEF was reversed by the PPAR α -specific antagonist GW6471. These results may partially explain the exacerbated liver toxicity caused by combination treatment with MTX and LEF and may raise concerns regarding the risk of potential drug-drug interactions between PPAR α agonists and Mrp substrates in the clinic., (Copyright © 2018 by The American Society for Pharmacology and Experimental Therapeutics.)

A series of novel hydrogen peroxide sensitive prodrugs of methotrexate (MTX) and aminopterin (AMT) were synthesized and evaluated for therapeutic efficacy in mice with collagen induced arthritis (CIA) as a model of chronic rheumatoid arthritis (RA). The prodrug strategy selected is based on ROS-labile 4-methylphenylboronic acid promoieties linked to the drugs via a carbamate linkage or a direct C-N bond. Activation under pathophysiological concentrations of H 2 O 2 proved to be effective, and prodrug candidates were selected in agreement with relevant in vitro physicochemical and pharmacokinetic assays. Selected candidates showed moderate to good solubility, high chemical and enzymatic stability, and therapeutic efficacy comparable to the parent drugs in the CIA model. Importantly, the prodrugs displayed the expected safer toxicity profile and increased therapeutic window compared to MTX and AMT while maintaining a comparable therapeutic efficacy, which is highly encouraging for future use in RA patients.

Background: The aim of this study was to investigate the correlation between 7-hydroxymethotrexate (7-OHMTX) and creatinine and to evaluate the predictive value of 7-OHMTX levels on delayed elimination at 24 and 48 hours. In addition, differences in methotrexate (MTX), 7-OHMTX levels, and MTX metabolism using the ratio MTX/7-OHMTX were determined according to age., Methods: The authors included a total of 106 cycles, corresponding to 33 patients (mean age: 9.8 years, range: 2-18 years) suffering from acute lymphoblastic leukemia, non-Hodgkin lymphoma and osteosarcoma and receiving high-dose MTX (HD-MTX). Plasma MTX, 7-OHMTX, and creatinine at T24 and T48 hours were measured., Results: Children older than 14 years had significantly higher MTX levels at T48 hours (1.25 versus 0.5 μmol/L, P < 0.05) and a higher MTX/7-OHMTX ratio (0.63 versus 0.20, P < 0.05) than children younger than 6 years. Plasma 7-OHMTX at T24 and T48 hours was positively correlated with serum creatinine and creatinine ratio at T24 and T48 hours. MTX levels provided a better specificity and sensitivity at both 24 and 48 hours than 7-OHMTX to predict delayed MTX elimination. A MTX threshold close to 0.83 μmol/L at T48 hours improved specificity from 58% to 82% and keeps sensitivity at 100%. The authors identified a cut-off at 65 μmol/L for MTX at T24 hours with a good sensitivity (75%) and specificity above 50%., Conclusions: These results confirm the concentration-dependent nephrotoxicity of 7-OHMTX. Children older than 14 years old had a higher MTX levels at 48 hours and a higher MTX/7-OHMTX ratio, suggesting a faster metabolism in younger children. This study identified a higher and more specific MTX threshold at T48 hours compared to those currently used, and a new threshold at T24 hours.

Purpose: Methotrexate (MTX) and adalimumab are well-recognized treatments of rheumatoid arthritis (RA), the efficacy of which may be driven by intracellular polyglutamates (PGs). The aim of this analysis was to characterize MTX PG concentrations and adalimumab pharmacokinetics in the CONCERTO trial. In addition, the relationships between MTX dose/pharmacokinetics, adalimumab pharmacokinetics, and efficacy were evaluated., Methods: CONCERTO was a double-blind, parallel-arm study in patients with early RA randomized to adalimumab 40 mg SC every other week plus blinded MTX 2.5, 5, 10, or 20 mg PO once weekly, for 26 weeks. Blood samples were obtained through week 26 for the determination of concentrations of MTX PG, adalimumab, and anti-adalimumab antibody (AAA). Clinical outcomes were also assessed., Findings: A total of 395 patients were included in the analysis (MTX, 329; adalimumab, 395). The mean time to steady-state MTX PG concentration was increased with MTX dose, from 8 to >26 weeks, depending on PG chain length. Dose proportionality changed with PG chain length. As MTX dose was increased, the percentage of short-chain PGs increased less than dose proportionally, while the percentage of long-chain PGs increased more than dose proportionally. For very-long-chain PGs, dose proportionality could not be assessed due to the nonmeasurable concentrations in the 2.5- and 5-mg MTX dose groups. As MTX dose increased, mean adalimumab concentrations also increased (P < 0.001). The percentage of patients with AAA decreased with increasing MTX dose, and at week 26, AAA + status was significantly correlated with MTX dose level (P = 0.005). In general, rates of response, defined using the 28-joint count disease activity score based on C-reactive protein (DAS28[CRP]; response, <3.2), were greater in the subgroup without AAA. The likelihood of a patient achieving a DAS28(CRP) response was related to the baseline measurement (P < 0.001) and to the concentration of adalimumab (P = 0.001), but not to the MTX regimen (P = 0.689)., Implications: The dose-response characteristics of MTX PG pharmacokinetics and the resultant effects of MTX on adalimumab exposures should be considered when determining the benefit-risk profile of MTX and adalimumab combination therapy in patients with early RA. ClinicalTrials.gov identifier: NCT01185301., (Copyright © 2018 Elsevier HS Journals, Inc. All rights reserved.)

Most drugs are metabolized in the human body. Therefore, it is essential for therapeutic drug monitoring studies to also take into account the concentrations of drug metabolites. One of the possible metabolic activities on drugs such as pemetrexed or methotrexate is (poly)glutamation. Here, we report on a series of experiments that we performed to investigate the stability of polyglutamate metabolites in plasma. Removal of glutamate residues from pemetrexed polyglutamate by most likely proteases in human plasma is influenced by temperature as it is observed at 25°C and even more strongly at 37°C, but not at 4°C. The observed protease activity is highly variable among patients; in approximately 15-20% of the patients tested it is not observed, whereas in other individuals the activity is so extensive that after 10min, more than 50% of spiked polyglutamated pemetrexed is degraded at room temperature (5-10% of the tested individuals). Similar observations also pertain to methotrexate polyglutamates. These observations do not extend to pemetrexed and methotrexate themselves which are unaffected by this activity. Due to the considerable and, among individuals, variable protease activities on polyglutamated drug metabolites in plasma, these metabolites are virtually impossible to quantify if no precautions are taken., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Available ecotoxicological data for anti-cancer drugs and their metabolites are incomplete, and only some studies have been accompanied by chemical analysis. Therefore, the main aim of this study was to evaluate the acute toxicity of the six most commonly used cytostatics, namely cyclophosphamide (CF), ifosfamide (IF), 5-fluorouracil (5-FU), imatinib (IMT), tamoxifen (TAM) and methotrexate (MET) and its metabolite - 7-hydroxymethotrexate (7-OH-MET), towards selected aquatic organisms, namely bacteria Vibrio fischeri, algae Raphidocelis subcapitata, crustaceans Daphnia magna and duckweed Lemna minor. All ecotoxicological tests were accompanied by chemical analysis to determine the differences between nominal and actual concentrations of investigated compounds and their stability under test conditions. For unstable compounds, tests were performed in static and semi-static conditions. It was observed that L. minor was the most sensitive organism. The compounds that were most toxic to aquatic organisms were 5-FU (highly toxic to algae, EC 50  = 0.075 mg L -1 ), MET and TAM (very toxic to highly toxic to duckweed depending on the test conditions; EC 50MET 0.08-0.16 mg L -1 , EC 50TAM 0.18-0.23 mg L -1 ). It is suspected that MET and 5-FU mainly affected algae and plants most probably because the exposure time was long enough for them to cause a specific effect (they inhibit DNA replication and act predominantly on actively dividing cells). Furthermore, the obtained results also suggest that the toxicity of the metabolites/potentially produced degradation products of MET towards duckweed is lower than that of the parent form, whereas the toxicity of TAM degradation products is in the same range as that of TAM., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Introduction: The use of hybrid molecules has become one of the most significant approaches in new cytotoxic drug design. This study describes synthesis and characterization of conjugates consisting of two well-known and characterized chemotherapeutic agents: methotrexate (MTX) and epirubicin (EPR). The synthesized conjugates combine two significant anticancer strategies: combinatory therapy and targeted therapy. These two drugs were chosen because they have different mechanisms of action, which can increase the anticancer effect of the obtained conjugates. MTX, which is a folic acid analog, has high cytotoxic properties and can serve as a targeting moiety that can reach folate receptors (FRs) overexpresing tumor cells. Combination of nonselective drugs such as EPR with MTX can increase the selectivity of the obtained conjugates, while maintaining the high cytotoxic properties., Materials and Methods: Conjugates were purified by RP-HPLC and the structure was investigated by MS and MS/MS methods. The effect of the conjugates on proliferation of LoVo, LoVo/Dx, MCF-7 and MV-4-11 human cancer cell lines was determined by SRB or MTT assay., Results: The conjugation reaction results in the formation of monosubstituted (α, γ) and disubstituted MTX derivatives. In vitro proliferation data demonstrate that the conjugates synthesized in our study show lower cytotoxic properties than both chemotherapeutics used alone., Discussion: Epirubicin cytotoxicity was not observed in obtained conjugates. Effective drugs release after internalization needs further investigation.

The application of Raman spectroscopy as a detection method coupled with liquid chromatography (LC) has recently attracted considerable interest, although this has currently been limited to isocratic elution. The combination of LC with rapidly advancing Raman techniques, such as surface-enhanced Raman scattering (SERS), allows for rapid separation, identification and quantification, leading to quantitative discrimination of closely eluting analytes. This study has demonstrated the utility of SERS in conjunction with reversed-phase liquid chromatography (RP-LC), for the detection and quantification of the therapeutically relevant drug molecule methotrexate (MTX) and its metabolites 7-hydroxy methotrexate (7-OH MTX) and 2,4-diamino-N(10)-methylpteroic acid (DAMPA) in pure solutions and mixtures, including spikes into human urine from a healthy individual and patients under medication. While the RP-LC analysis developed employed gradient elution, where the chemical constituents of the mobile phase were modified stepwise during analysis, this did not overtly interfere with the SERS signals. In addition, the practicability and clinical utility of this approach has also been demonstrated using authentic patients' urine samples. Here, the identification of MTX, 7-OH MTX and DAMPA are based on their unique SERS spectra, providing limits of detection of 2.36, 1.84, and 3.26 μM respectively. Although these analytes are amenable to LC and LC-MS detection an additional major benefit of the SERS approach is its applicability toward the detection of analytes that do not show UV absorption or are not ionised for mass spectrometry (MS)-based detection. The results of this study clearly demonstrate the potential application of online LC-SERS analysis for real-time high-throughput detection of drugs and their related metabolites in human biofluids.

Objectives: The objective of this study is to evaluate the pharmacokinetics and pharmacodynamics of methotrexate-polyglutamates (MTX-PGs) in erythrocytes in patients with rheumatoid arthritis and correlate them with the efficacy., Methods: MTX-PG concentrations in erythrocytes were measured in 42 MTX-naïve patients repeatedly for 24 weeks by high-performance liquid chromatography. In 56 patients receiving stable MTX doses for at least 12 weeks, the correlation between MTX doses and MTX-PG concentrations was examined. The efficacy was measured by the change of DAS28CRP (ΔDAS28CRP)., Results: There were moderate correlations between MTX dose and MTX-PG 3, 4, and 5. At 24 weeks, MTX-PG2, 3, 4, and 1-5 were higher in patients with ΔDAS28CRP >1.2 than in those with ≤1.2. The cutoff value of MTX-PG1-5 to discriminate ΔDAS28CRP >1.2 from ≤1.2 at 24 weeks was 68.7 nM. Among 20 patients with MTX-PG1-5 > 50.6 nM at 8 weeks, seven already improved at 8 weeks and additional 11 improved at 24 weeks (p < 0.001). On the contrary, among the nine patients with MTX-PG1-5 ≤ 50.6 nM at 8 weeks, none improved at 8 weeks and only one improved at 24 weeks (p = 0.500)., Conclusions: Erythrocyte MTX-PGs might be a potential indicator and predictor of MTX efficacy.

Methotrexate is an efficacious immunosuppressant for induction and maintenance of remission in Crohn's disease. The goal of this pilot study was to determine whether total or individual methotrexate glutamate levels (MTXGlu n ) in red blood cells correlate with disease activity and adverse events in Crohn's disease. A cross-sectional study was undertaken with 12 patients on a stable dose of 25 mg weekly methotrexate (oral or subcutaneous). Clinical disease activity was assessed by the Harvey-Bradshaw Index (HBI), and biologic disease activity was measured by inflammatory markers. Concentrations of individual MTXGlu n levels were measured in red blood cells (RBCs) using high-performance liquid chromatography-mass spectrometry. No association was observed between RBC individual (MTXGlu n ) or total methotrexate glutamate concentrations and clinical disease activity (HBI score) or inflammatory markers or adverse events. Although Crohn's disease patients in remission appeared to generally have higher RBC total longer-chain methotrexate polyglutamate (MTXGlu 3+4+5 ) concentrations compared with those with active disease, a definitive association between RBC MTXGlu 3+4+5 levels and clinical disease activity could not be established. Larger longitudinal studies in patients with diverse disease activity are needed to establish the value of MTXGlu n levels as indicators of treatment efficacy and clinical outcome., (© 2016, The American College of Clinical Pharmacology.)

Background: Adjustment of mercaptopurine and methotrexate maintenance therapy of acute lymphoblastic leukaemia by leucocyte count is confounded by natural variations. Cytotoxicity is primarily mediated by DNA-incorporated thioguanine nucleotides (DNA-TGN). The aim of this study was to establish whether DNA-TGN concentrations in blood leucocytes during maintenance therapy are associated with relapse-free survival., Methods: In this substudy of the NOPHO ALL2008 phase 3 trial done in 23 hospitals in seven European countries (Denmark, Estonia, Finland, Iceland, Lithuania, Norway, and Sweden), we analysed data from centralised and blinded analyses of 6-mercaptopurine and methotrexate metabolites in blood samples from patients with non-high-risk childhood acute lymphoblastic leukaemia. Eligible patients were aged 1·0-17·9 years; had been diagnosed with non-high-risk precursor B-cell or T-cell leukaemia; had been treated according to the Nordic Society of Pediatric Hematology and Oncology ALL2008 protocol; and had reached maintenance therapy in first remission. Maintenance therapy was (mercaptopurine 75 mg/m 2 once per day and methotrexate 20 mg/m 2 once per week, targeted to a leucocyte count of 1·5-3·0 × 10 9 cells per L). We measured DNA-TGN and erythrocyte concentrations of TGN nucleotides, methylated mercaptopurine metabolites, and methotrexate polyglutamates. The primary objective was the association of DNA-TGN concentrations and 6-mercaptopurine and methotrexate metabolites with relapse-free survival. The secondary endpoint was the assessment of DNA-TGN concentration and 6-mercaptopurine and methotrexate metabolites during maintenance therapy phase 2., Findings: Between Nov 26, 2008 and June 14, 2016, 1509 patients from the NOPHO ALL2008 study were assessed for eligibility in the DNA-TGN substudy, of which 918 (89%) of 1026 eligible patients had at least one DNA-TGN measurement and were included in the analyses. Median follow-up was 4·6 years (IQR 3·1-6·1). Relapse-free survival was significantly associated with DNA-TGN concentration (adjusted hazard ratio 0·81 per 100 fmol/μg DNA increase, 95% CI 0·67-0·98; p=0·029). In patients with at least five blood samples, erythrocyte concentrations of TGN, methylated mercaptopurine metabolites, and methotrexate polyglutamates were associated with DNA-TGN concentration (all p<0·0001)., Interpretation: Our results suggest the need for intervention trials to identify clinically applicable strategies for individualised drug dosing to increase DNA-TGN concentration, and randomised studies to investigate whether such strategies improve cure rates compared with current dose adjustments based on white blood cell counts., Funding: Danish Cancer Society, Childhood Cancer Foundation (Denmark), Childhood Cancer Foundation (Sweden), Nordic Cancer Union, Otto Christensen Foundation, University Hospital Rigshospitalet, and Novo Nordic Foundation., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Background: 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., Methods: 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., Results: 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., Conclusions: In this preliminary study, higher levels of RBC MTX-glu3 were found to be the independent predictors for adverse effects in rheumatoid arthritis patients.