Plasma Distribution of Methotrexate and Its Polyglutamates in Pediatric Acute Lymphoblastic Leukemia: Preliminary Insights.

BACKGROUND AND OBJECTIVE: High-dose methotrexate (HD-MTX) is the mainstream therapy of current acute lymphoblastic leukemia (ALL) regimens, but frequent intra- and interindividual differences in the clinical response to HD-MTX lead to chemotherapeutic interruption or discontinuation. The exact mechanism of transport across the cell membrane and the disposition of active methotrexate metabolites-methotrexate polyglutamates (MTXPGs)-are not well described in the literature. The aim of this study was to gain more insight into the plasma distribution of methotrexate and MTXPGs in pediatric patients with ALL and to clarify the obscure pathways of MTXPGs. METHODS: We prospectively measured the concentrations of MTXPG1-7 in plasma samples from three male pediatric patients treated with HD-MTX and leucovorin rescue according to the IC-BFM 2009 protocol using liquid chromatography-mass spectrometry (LC-MS). Blood samples were obtained at 24, 36, 42, and 48 h after the start of HD-MTX treatment. RESULTS: Noticeable plasma concentrations of MTXPGs with a 2.2-fold interpatient variability were detected. The highest interindividual variability in total plasma MTXPG concentration was observed at 36 h, and ranged from 13.78 to 30.82 µmol/L. Among all patients, the predominant polyglutamate types in relation to the total plasma MTXPG concentration at each time point were MTXPG3 (16.71-30.02%) and MTXPG5 (26.23-38.60%), while MTXPG7 was the least abundant MTXPG (3.22-5.02%). CONCLUSION: The presence of MTXPGs in plasma of patients with ALL could be related to the action of ABC efflux transporters on blood cells and hepatocytes resulting from the administration of high doses of methotrexate. This study may not draw definitive conclusions, but it does reduce uncertainty about the dynamics of methotrexate and its active metabolites, which may be of vital importance for achieving a clinical response.

Comparison of two dose escalation strategies of methotrexate in active rheumatoid arthritis: a multicentre, parallel group, randomised controlled trial.

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.

Methotrexate Triglutamate as a Determinant of Clinical Response in Mexican Patients With Rheumatoid Arthritis: Pharmacokinetics and Dose Recommendation.

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/m2 ) * (red blood cells/4.6 × 106 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.

Studies on the intracellular accumulation process of methotrexate and its correlation with the key protein using an LC-MS/MS method: a novel way to realize prospective individualized medication.

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 (MTXPG1) and its metabolites MTXPG2-7 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).

Weekly split-dose regimen for oral methotrexate reduced polyglutamation in red blood cells in patients with rheumatoid arthritis compared with single-dose regimen: Results from a multicentered randomized control trial.

AIMS: We compared the incidence of adverse events between single and divided-dose regimens of methotrexate (MTX) by using a multicenter randomized controlled trial. METHODS: Eighty-nine patients with insufficient control on MTX 8 mg/wk were randomly assigned into single-dose (39 patients) or triple dose (39 patients) groups. The MTX dose for all patients was gradually increased to 16 mg/wk. The primary endpoint was the occurrence of liver dysfunction during the observation period (20 weeks). RESULTS: There were no differences in baseline data and MTX dose at Week 20 between groups. There was no significant difference in the incidence of liver dysfunction between groups (single dose, 3 [7.7%] patients vs. triple dose, 5 [13.2%] patients; P = .455). The incidence of adverse event increased in triple dose (single dose, 12 [30.8%] patients vs. triple dose, 20 [51.3%]), but the difference was not significant (P = .066). There was no significant difference in disease activity between groups, although MTX-triglutamate (PG3), MTX-PG4, and MTX-PG5 were significantly higher in the single dose group. CONCLUSIONS: Weekly split dosing reduced the polyglutamation of MTX. There was no significant difference in efficacy and safety between the 2 groups.

Methotrexate Polyglutamate Values in Children and Adolescents With Acute Lymphoblastic Leukemia During Maintenance Therapy.

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.

High and individually variable enzymatic activity precludes accurate determination of pemetrexed, methotrexate and their polyglutamate metabolite concentrations in plasma.

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.

Renal targeting potential of a polymeric drug carrier, poly-l-glutamic acid, in normal and diabetic rats.

BACKGROUND AND PURPOSE: Poly-l-glutamic acid (PG) has been used widely as a carrier to deliver anticancer chemotherapeutics. This study evaluates PG as a selective renal drug carrier. EXPERIMENTAL APPROACH: 3H-deoxycytidine-labeled PGs (17 or 41 kDa) and 3H-deoxycytidine were administered intravenously to normal rats and streptozotocin-induced diabetic rats. The biodistribution of these compounds was determined over 24 h. Accumulation of PG in normal kidneys was also tracked using 5-(aminoacetamido) fluorescein (fluoresceinyl glycine amide)-labeled PG (PG-AF). To evaluate the potential of PGs in ferrying renal protective anti-oxidative stress compounds, the model drug 4-(2-aminoethyl)benzenesulfonyl fluoride hydrochloride (AEBSF) was conjugated to 41 kDa PG to form PG-AEBSF. PG-AEBSF was then characterized and evaluated for intracellular anti-oxidative stress efficacy (relative to free AEBSF). RESULTS: In the normal rat kidneys, 17 kDa radiolabeled PG (PG-Tr) presents a 7-fold higher, while 41 kDa PG-Tr shows a 15-fold higher renal accumulation than the free radiolabel after 24 h post injection. The accumulation of PG-AF was primarily found in the renal tubular tissues at 2 and 6 h after an intravenous administration. In the diabetic (oxidative stress-induced) kidneys, 41 kDa PG-Tr showed the greatest renal accumulation of 8-fold higher than the free compound 24 h post dose. Meanwhile, the synthesized PG-AEBSF was found to inhibit intracellular nicotinamide adenine dinucleotide phosphate oxidase (a reactive oxygen species generator) at an efficiency that is comparable to that of free AEBSF. This indicates the preservation of the anti-oxidative stress properties of AEBSF in the conjugated state. CONCLUSION/IMPLICATIONS: The favorable accumulation property of 41 kDa PG in normal and oxidative stress-induced kidneys, along with its capabilities in conserving the pharmacological properties of the conjugated renal protective drugs, supports its role as a potential renal targeting drug carrier.

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

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.

Methotrexate Polyglutamate Monitoring in Patients With Crohn's Disease.

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 (MTXGlun ) 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 MTXGlun levels were measured in red blood cells (RBCs) using high-performance liquid chromatography-mass spectrometry. No association was observed between RBC individual (MTXGlun ) 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 (MTXGlu3+4+5 ) concentrations compared with those with active disease, a definitive association between RBC MTXGlu3+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 MTXGlun levels as indicators of treatment efficacy and clinical outcome.

Prediction of the therapeutic response to methotrexate at 24 weeks by methotrexate-polyglutamates concentration in erythrocytes at 8 weeks in patients with rheumatoid arthritis.

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.

A new quantification method for assessing plasma concentrations of pemetrexed and its polyglutamate metabolites.

Currently no quantification method exists for potentially therapeutically relevant polyglutamate metabolites of the drug pemetrexed which is used for the treatment of lung carcinoma patients. We developed and tested an LC-MS/MS-based analytical assay that uses isotope-labeled internal standards to quantify pemetrexed and its (poly)glutamate metabolites in clinical human plasma samples of lung carcinoma patients. UHPLC chromatography and triple quadrupole mass spectrometry showed an LLOQ of 0.2nmol/L for pemetrexed and an LLOQ of 0.5nmol/L for the two metabolites (one glutamate and two glutamate moieties covalently bound to the pemetrexed molecule, for which no other quantification methods have previously been published). The recoveries for PMTX and its metabolites ranged between 30% and 67%. Precision and accuracy at a concentration of 20nmol/L for all four analytes was well below 15% CV. The precision (RSD) in the biological replicates of the separate days (within-run precision) as well as the reproducibility over several days (between-run precision), tested in the range of 5-250nmol/L, were all below 15%. Autosampler, benchtop and freeze-thaw cycle stability of the analytes was also demonstrated. To illustrate the new assay in a relevant biological context, concentrations of pemetrexed and the two metabolites were quantified in plasma samples of lung carcinoma patients treated with pemetrexed. The assay is straightforward, relatively easy to perform, and has potential for use in therapeutic drug monitoring in non-small cell lung carcinoma patients.

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.

INTRODUCTION: Methotrexate (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. METHODS: Data 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. RESULTS: Wide 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). CONCLUSIONS: Nonadherence 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 REGISTRATION: ISRCTN Registry identifier: ISRCTN93945409 . Registered 2 December 2011.

Immunoassay for Capsular Antigen of Bacillus anthracis Enables Rapid Diagnosis in a Rabbit Model of Inhalational Anthrax.

Inhalational anthrax is a serious biothreat. Effective antibiotic treatment of inhalational anthrax requires early diagnosis; the further the disease has progressed, the less the likelihood for cure. Current means for diagnosis such as blood culture require several days to a result and require advanced laboratory infrastructure. An alternative approach to diagnosis is detection of a Bacillus anthracis antigen that is shed into blood and can be detected by rapid immunoassay. The goal of the study was to evaluate detection of poly-γ-D-glutamic acid (PGA), the capsular antigen of B. anthracis, as a biomarker surrogate for blood culture in a rabbit model of inhalational anthrax. The mean time to a positive blood culture was 26 ± 5.7 h (mean ± standard deviation), whereas the mean time to a positive ELISA was 22 ± 4.2 h; P = 0.005 in comparison with blood culture. A lateral flow immunoassay was constructed for detection of PGA in plasma at concentrations of less than 1 ng PGA/ml. Use of the lateral flow immunoassay for detection of PGA in the rabbit model found that antigen was detected somewhat earlier than the earliest time point at which the blood culture became positive. The low cost, ease of use, and rapid time to result of the lateral flow immunoassay format make an immunoassay for PGA a viable surrogate for blood culture for detection of infection in individuals who have a likelihood of exposure to B. anthracis.

Fast and sensitive detection of an anthrax biomarker using SERS-based solenoid microfluidic sensor.

We report the application of a fully automated surface-enhanced Raman scattering (SERS)-based solenoid-embedded microfluidic device to the quantitative and sensitive detection of anthrax biomarker poly-γ-D-glutamic acid (PGA) in solution. Analysis is based on the competitive reaction between PGA and PGA-conjugated gold nanoparticles with anti-PGA-immobilized magnetic beads within a microfluidic environment. Magnetic immunocomplexes are trapped by yoke-type solenoids embedded within the device, and their SERS signals were directly measured and analyzed. To improve the accuracy of measurement process, external standard values for PGA-free serum were also measured through use of a control channel. This additional measurement greatly improves the reliability of the assay by minimizing the influence of extraneous experimental variables. The limit of detection (LOD) of PGA in serum, determined by our SERS-based microfluidic sensor, is estimated to be 100 pg/mL. We believe that the defined method represents a valuable analytical tool for the detection of anthrax-related aqueous samples.

Feasibility of antibody-poly(glutamic acid) complexes: preparation of high-concentration antibody formulations and their pharmaceutical properties.

Development of high-concentration antibody formulations for subcutaneous administration remains challenging. Recently, a precipitation-redissolution method was proposed to prepare suspensions or precipitates of salt-dissociable protein-poly(amino acid) complexes. To elucidate the utility of this method for protein therapy, we investigated the feasibility of a precipitation-redissolution method using poly(amino acid) for high-concentration antibody formulation. Omalizumab and adalimumab formulations of 150 mg/mL could be prepared using poly-l-glutamic acid (polyE) from low-concentration stock solutions. Enzyme-linked immunosorbent assay, circular dichroism, and size-exclusion chromatography revealed that the formation of antibody-polyE complex and precipitation-redissolution process did not significantly affect the immunoreactivity or secondary structure of the antibodies. The precipitation-redissolution method was less time-consuming and more effective than lyophilization-redissolution, evaporation-redissolution, and ultrafiltration from the viewpoint of final yield. Scalability was confirmed from 400 µL to 1.0 L. The general toxicity and pharmacokinetic profiles of the antibody-polyE complex formulations were similar to those of conventional antibody formulations. These results suggested that the precipitation-redissolution method using poly(amino acid) has great potential as a concentration method for antibody formulation and medicinal use.

Prediction of methotrexate efficacy and adverse events in patients with juvenile idiopathic arthritis: a systematic literature review.

BACKGROUND: Methotrexate (MTX) is the cornerstone disease-modifying anti-rheumatic drug in juvenile idiopathic arthritis (JIA). In JIA, it is important to start effective treatment early to avoid long-term sequelae, such as joint damage. To accomplish this goal, it is crucial to know beforehand who is going to respond well to MTX. In addition, MTX adverse effects such as MTX intolerance occur frequently, potentially hindering its efficacy. To avoid inefficacy of an otherwise effective drug, the physician should be timely aware of these adverse events. Consequently, to optimise treatment of JIA patients with MTX, predictors for efficacy and adverse events should be used in daily clinical practice. The aim of this study was to summarise the existing knowledge about such predictors. METHODS: A systematic literature search was performed in PubMed, Embase and The Cochrane Library, and 1,331 articles were identified. These were selected based on their relevance to the topic and critically appraised according to pre-defined criteria. Predictors for MTX efficacy and adverse events were extracted from the literature and tabulated. RESULTS: Twenty articles were selected. The overall quality of the studies was good. For MTX efficacy, candidate predictors were antinuclear antibody positivity, the childhood health assessment questionnaire score, the myeloid-related protein 8/14 level, long-chain MTX polyglutamates, bilateral wrist involvement and some single nucleotide polymorphisms (SNPs) in the adenosine triphosphate binding cassette and solute carrier transporter gene families. For MTX adverse events, potential predictors were alanine aminotransferase and thrombocyte level and two SNPs in the γ-glutamyl hydrolase and methylenetetrahydrofolate reductase genes. However, validation of most predictors in independent cohorts was still lacking. CONCLUSIONS: Interesting candidate predictors were found, especially for MTX efficacy. However, most of these were not validated. This should be the goal of future efforts. A clinically relevant way to validate the predictors is by means of creating a clinical prediction model.

Determinants of erythrocyte methotrexate polyglutamate levels in rheumatoid arthritis.

OBJECTIVE: Low-dose methotrexate (MTX) is the anchor drug in the treatment for rheumatoid arthritis (RA). Response to MTX is related to the intracellular MTX-polyglutamate (MTX-PG) levels and little is known about its determinants. We aimed to define the determinants of erythrocyte MTX-PG concentrations in 2 prospective cohorts of patients with RA. METHODS: Patients with RA treated with MTX from 2 longitudinal cohorts were included: 93 from the MTX-R study (Rotterdam, the Netherlands derivation cohort), and 247 from the treatment in Rotterdam Early Arthritis Cohort study (validation cohort). MTX-PG concentrations were measured at 3 months of treatment using liquid chromatography/mass spectrometry. The MTX-PG were used as outcome measure. Various sociodemographic, clinical, biochemical, and genetic factors were assessed at baseline. Associations with MTX-PG levels were analyzed using multivariate regression analysis. RESULTS: Age was positively associated with MTX-PG1 (stß 0.23, p=0.033) and total MTX-PG (stß 0.23, p=0.018) in the derivation cohort, and with all MTX-PG in the validation cohort (MTX-PG1: stß 0.13, p=0.04; MTX-PG2: stß 0.21, p=0.001; MTX-PG3: stß 0.22, p<0.001; MTX-PG4+5: stß 0.25, p<0.001; and total MTX-PG: stß 0.32, p<0.001). Erythrocyte folate levels were positively associated with MTX-PG3 (stß 0.3, p=0.021) and total MTX-PG levels (stß 0.32, p=0.022) in the derivation cohort, which was replicated for MTX-PG3 (stß 0.15, p=0.04) in the validation cohort. Patients with the folylpolyglutamate synthase (FPGS) rs4451422 wild-type genotype had higher concentrations of MTX-PG3 (p<0.05), MTX-PG4+5 (p<0.05), and total MTX-PG (p<0.05) in both cohorts. In the combined cohort, MTX dose was positively associated with levels of MTX-PG3 (stß 0.23, p<0.001), MTX-PG4+5 (stß 0.30, p<0.001), and total MTX-PG (stß 0.20, p=0.002), but negatively associated with MTX-PG2 levels (stß -0.22, p<0.001). CONCLUSION: Our prospective study shows that higher age, higher MTX dose, higher erythrocyte folate status, and the FPGS rs4451422 wild-type genotype are associated with higher MTX-PG concentrations. While only up to 21% of interpatient variability can be explained by these determinants, this knowledge may aid in the development of personalized treatment in RA.

Using fluorescence polarization immunoassay for determination of erythrocyte methotrexate polyglutamates, a quick and easy test?

BACKGROUND: The folate antagonist methotrexate (MTX) is the anchor drug in the treatment of rheumatoid arthritis. The therapeutic effects of MTX are attributed to the intracellular levels of MTX, present in the cell as polyglutamates (MTX-PGs). We aimed to validate an immunoassay for the measurement of MTX-PG in erythrocytes. METHODS: Samples were analyzed by an adapted fluorescence polarization immune assay (FPIA) method on the FLx analyzer (Abbott). Cross-reactivity was determined in both plasma and erythrocyte pellet. In erythrocyte pellet, the imprecision, linearity, and lower limit of quantitation were determined. The method was compared with our in-house liquid chromatography tandem mass spectrometry (LC-MS/MS) method for total MTX-PG. RESULTS: For the adapted FPIA method, a linear range of 25-1000 nmol/L (R = 0.993) was obtained for total MTX-PG in erythrocytes. A coefficient of variation of <17% for interday and <8% for intraday imprecision was found and average recovery was 91%. Lower limit of quantitation was determined at 50 nmol/L total MTX-PG with a coefficient of variation of 15%. There was no significant proportional bias of the FPIA assay compared with our in-house LC-MS/MS method, but a (nonsignificant) constant positive bias was present [FPIA = 1.00 (95% confidence interval: 0.60-1.95) × LC-MS/MS + 31.00 nmol/L (95% confidence interval: -11.83 to 61.00)]. Results could be very different for individual patients as reflected in the poor R of 0.419. CONCLUSIONS: The FPIA method can be used to measure total MTX-PG in erythrocytes. Although there was no significant bias detected compared with the LC-MS/MS method, the FPIA method showed constant positive bias, probably because of interference from folates and MTX metabolites 2,4-diamino-N10-methylpteroic acid and 7-hydroxy-MTX. The correlation between both methods was average and resulted in large differences in individual patients, most likely because of problems during sample preparation.

A novel dried blood spot-LCMS method for the quantification of methotrexate polyglutamates as a potential marker for methotrexate use in children.

OBJECTIVE: Development and validation of a selective and sensitive LCMS method for the determination of methotrexate polyglutamates in dried blood spots (DBS). METHODS: DBS samples [spiked or patient samples] were prepared by applying blood to Guthrie cards which was then dried at room temperature. The method utilised 6-mm disks punched from the DBS samples (equivalent to approximately 12 µl of whole blood). The simple treatment procedure was based on protein precipitation using perchloric acid followed by solid phase extraction using MAX cartridges. The extracted sample was chromatographed using a reversed phase system involving an Atlantis T3-C18 column (3 µm, 2.1 × 150 mm) preceded by Atlantis guard column of matching chemistry. Analytes were subjected to LCMS analysis using positive electrospray ionization. KEY RESULTS: The method was linear over the range 5-400 nmol/L. The limits of detection and quantification were 1.6 and 5 nmol/L for individual polyglutamates and 1.5 and 4.5 nmol/L for total polyglutamates, respectively. The method has been applied successfully to the determination of DBS finger-prick samples from 47 paediatric patients and results confirmed with concentrations measured in matched RBC samples using conventional HPLC-UV technique. CONCLUSIONS AND CLINICAL RELEVANCE: The methodology has a potential for application in a range of clinical studies (e.g. pharmacokinetic evaluations or medication adherence assessment) since it is minimally invasive and easy to perform, potentially allowing parents to take blood samples at home. The feasibility of using DBS sampling can be of major value for future clinical trials or clinical care in paediatric rheumatology.