Recommendations for the use of methotrexate in juvenile idiopathic arthritis

Update on the systemic management of noninfectious uveitis in children and adolescents

Noninfectious uveitis (NIU) in children and adolescents is a rare but treatable cause of visual impairment in children. Treatments for pediatric NIU and their side effects, along with the risks of vision loss and the need for long-term disease monitoring, pose significant challenges for young patients and their families. Treatment includes local and systemic approaches and this review will focus on systemic therapies that encompass corticosteroids, conventional synthetic disease-modifying antirheumatic drugs (csDMARD), and biological disease-modifying antirheumatic drugs (bDMARD). Treatment is generally planned in a stepwise approach. Methotrexate is well-established as the preferential csDMARD in pediatric NIU. Adalimumab, an antitumor necrosis factor (TNF) agent, is the only bDMARD formally approved for pediatric NIU and has a good safety and efficacy profile. Biosimilars are gaining increasing visibility in the treatment of pediatric NIU. Other bDMARD with some evidence in literature for the treatment of pediatric NIU include infliximab, tocilizumab, abatacept, rituximab and, more recently, Janus kinase inhibitors. Important aspects of managing children on these systemic therapies include vaccination issues, risk of infection, and psychological distress. Also, strategies need to address regarding primary nonresponse/secondary loss of response to anti-TNF treatment, biological switching, and monitoring regimens for these drugs. Optimal management of pediatric uveitis involves a multidisciplinary team, including specialist pediatric uveitis and rheumatology nurses, pediatric rheumatologists, psychological support, orthoptic and optometry support, and play specialists.

Toward pharmacogenetic SLCO1B1-guided dosing of methotrexate in arthritis using a murine Slco1b2 knockout model

Low‐dose methotrexate (MTX) is a first‐line therapy for the treatment of arthritis. However, there is considerable interindividual variability in MTX exposure following standard dosing. Polymorphisms in SLCO1B1 significantly effect MTX clearance, altering therapeutic response. One decreased function variant, rs4149056 (c.521T>C, Val174Ala), slows MTX clearance and in vitro uptake of MTX. This phenotype was recapitulated in a mouse model using a knockout (KO) of the murine orthologue, Slco1b2. Our objective was to investigate the impact of this phenotype on the pharmacokinetics and therapeutic outcomes of low‐dose MTX in a murine model of collagen‐induced arthritis (CIA). We evaluated response to MTX in mice with CIA using wildtype (WT), heterozygous, and KO Slco1b2 mice on a DBA1/J background. Arthritis was macroscopically evaluated daily to quantify disease progression. Mice received 2 mg/kg or a pharmacogenetically guided MTX dose subcutaneously 3 times a week for 2 weeks. MTX concentrations were collected at the end of the study and exposure (day*µM) was estimated using a two‐compartment model. Mice displayed a seven‐fold range in MTX exposure and revealed a significant exposure‐response relationship (p = 0.0027). KO mice receiving the 2 mg/kg dosing regimen had 2.3‐fold greater exposure to MTX (p < 0.0001) and a 66% reduction in overall disease progression (p = 0.011) compared to WT mice. However, exposure and response were equivalent when pharmacogenetically guided dosing was used. These studies demonstrate that an exposure‐response relationship exists for MTX and that Slco1b2 genotype affects MTX exposure and therapeutic response. Such evidence supports the use of SLCO1B1‐pharmacogenetic dosing of low‐dose MTX for patients with arthritis.

Potential Benefits of the Self-Administration of Subcutaneous Methotrexate with Autoinjector Devices for Patients: A Review

The role of patient adherence in improving the efficacy of any treatment is widely accepted, as well as its impact in optimizing the use of healthcare resources and associated costs. Adherence is particularly affected in chronic conditions, such as rheumatoid arthritis (RA), requiring long-term therapies and a commitment of the patient to manage his/her disease. Methotrexate (MTX) is one of the mainstays of treatment for several immune-mediated inflammatory joint and skin diseases, especially RA. The use of parenteral MTX, particularly when administered as a subcutaneous (SC) injection, has recently raised a great interest to overcome the limitations of oral MTX. For addressing this issue, new optimized self-injection systems have been developed to improve the ease of use of SC MTX. Increasing evidence shows how patients tend to opt for autoinjectors over prefilled syringes or conventional syringes in terms of easiness of use, preference and satisfaction, regardless of whether the treatment is a biologic or MTX. Additionally, positive views and beliefs of patients about treatment may contribute to increasing expectations of effectiveness and treatment adherence. Similarly, the implementation of prefilled pens in clinical practice might be a way to facilitate and simplify the self-injection of SC MTX delivery, optimizing adherence and treatment outcomes as a consequence. This article aimed to review the available literature data on the use of MTX autoinjectors and their impact on treatment adherence and patients’ perceptions.

Outcome of children with oligoarticular juvenile idiopathic arthritis compared to polyarthritis on methotrexate- data of the German BIKER registry

BACKGROUND

Oligoarticular juvenile idiopathic arthritis (oligoJIA) is the most commonly diagnosed category of chronic arthritis in children. Nevertheless, there are no evidence- based guidelines for its treatment, in particular for the use of methotrexate (MTX). The primary objective of this analysis is to evaluate the outcomes in patients with persistent oligoJIA compared to those with extended oligoJIA and rheumatoid factor (RF) negative polyarthritis treated with methotrexate.

METHODS

Patients with persistent or extended oligoJIA or RF negative PA recorded in the Biologics in Pediatric Rheumatology Registry (BiKeR), receiving methotrexate for the first time were included in the analyses. Efficacy was determined using the Juvenile Arthritis Disease Activity Score 10 (JADAS 10). Safety assessment included the documentation of adverse and serious adverse events.

RESULTS

From 2005 through 2011, 1056 patients were included: 370 patients with persistent oligoJIA, 221 patients with extended oligoJIA and 467 patients with RF negative PA. Therapeutic efficacy was observed following the start of methotrexate. Over a period of 24 months JADAS-minimal disease activity (JADAS ≤2) was reached in 44% of patients with persistent oligoJIA, 38% with extended oligoJIA, 46% with RF negative PA, JADAS-remission defined as JADAS ≤1 was reached in 33% of patients with persistent oligoJIA, 29% with extended oligoJIA and 35% (RF negative PA). Patients with extended oligoJIA achieved JADAS remission significantly later and received additional biologic disease-modifying drugs significantly more often than patients with persistent oligoJIA or RF negative PA (p < 0.001). Tolerability was comparable. New onset uveitis occurred in 0.3 to 2.2 per 100 patient years.

CONCLUSIONS

Patients with persistent oligoJIA taking methotrexate are at least as likely to enter remission as patients with extended oligo JIA or polyarticular JIA. Patients with extended oligoJIA achieved JADAS remission significantly later. Within 2 years, almost half of the patients with persistent oligoJIA achieved JADAS-minimal disease activity.

MTX intolerance in children and adolescents with juvenile idiopathic arthritis

MTX is the medication most commonly used for antirheumatic treatment in juvenile idiopathic arthritis. It has high efficacy, is usually well tolerated and has an excellent safety profile. However, frequently intolerance symptoms develop that manifest as nausea, feelings of disgust or abdominal complaints prior to or directly after administration of the medication. No obvious toxicity is causing these intolerance symptoms, but symptoms are strictly limited to MTX and not transferred to other medications. MTX intolerance causes a significant reduction of quality of life in affected patients, frequently puts the treating physician in difficult situations regarding treatment choice, and may lead to uncomfortable decisions whether or not to stop an otherwise effective drug. Conventional countermeasures such as antiemetics, change of route from subcutaneous to oral or vice versa, or taste masking usually have only a limited effect. In this review, we present the current knowledge on MTX intolerance, its clinical picture and commonly employed strategies. We also consider newer behavioural treatment strategies that may offer a more effective symptom control.

[MTX intolerance in children and adolescents with juvenile idiopathic arthritis]

Methotrexate (MTX) is the medication most commonly used for antirheumatic treatment in juvenile idiopathic arthritis. It has high efficacy, is usually well tolerated and has an excellent safety profile. However, intolerance symptoms frequently develop, which manifest as nausea, feelings of disgust, or abdominal complaints prior to or directly after application of the medication. A direct side effect can usually be easily excluded; however, the symptoms are limited to treatment with MTX. This MTX intolerance causes a significant reduction in the quality of life of affected patients, frequently puts the treating physician in an uncomfortable situation, and not uncommonly results in discontinuation of treatment. Conventional countermeasures such as antiemetics, change of route from subcutaneous to oral or vice versa, or, for example, taste masking, usually have only limited effect. Newer behavioral treatment strategies raise hopes of more effective symptom control.

Methotrexate in juvenile idiopathic arthritis: advice and recommendations from the MARAJIA expert consensus meeting

BACKGROUND

Conventional pharmacological therapies for the treatment of juvenile idiopathic arthritis (JIA) consist of non-biological, disease-modifying antirheumatic drugs, among which methotrexate (MTX) is the most commonly prescribed. However, there is a lack of consensus-based clinical and therapeutic recommendations for the use of MTX in the management of patients with JIA. Therefore, the Methotrexate Advice and RecommendAtions on Juvenile Idiopathic Arthritis (MARAJIA) Expert Meeting was convened to develop evidence-based recommendations for the use of MTX in the treatment of JIA.

METHODS

The preliminary executive committee identified a total of 9 key clinical issues according to the population, intervention, comparator, outcome (PICO) approach, and performed an evidence-based, systematic, literature review. During the subsequent Expert Meeting, the relevant evidence was assessed and graded, and 10 recommendations were made.

RESULTS

Recommendations relating to the efficacy, optimal dosing and route of administration and duration of treatment with MTX in JIA, and to the issue of folic acid supplementation to prevent MTX side effects, use of MTX in the treatment of chronic JIA-associated uveitis, combination treatment with biologic agents, and the use of vaccinations in patients with JIA were developed. The selected topics were considered to represent clinically important issues facing clinicians caring for patients with JIA. Evidence was insufficient to formulate recommendations for the use of biomarkers predictive of treatment response.

CONCLUSIONS

These consensus recommendations provide balanced and evidence-based recommendations designed to have broad value for physicians and healthcare clinicians involved in the clinical management of patients with JIA.

Associations between gene polymorphisms and treatment outcomes of methotrexate in patients with juvenile idiopathic arthritis

Aim: Performance of a meta-analysis with respect to the genetic predictors of methotrexate (MTX) treatment outcomes, efficacy and toxicity, in patients with juvenile idiopathic arthritis (JIA). Methods: Databases of OVID MEDLINE and OVID EMBASE were searched to collect the studies addressing correlations between gene polymorphisms and efficacy and/or toxicity in MTX-treated JIA patients. Pooled odds ratios (ORs) with 95% CIs were estimated in allelic, recessive and/or dominant models. Results: With regards to efficacy, the C677T (rs1801133) polymorphism in MTHFR was associated with nonresponse to MTX treatment in a recessive model (OR: 0.40; 95% CI: 0.19–0.84). For associations with toxicity, the MTHFR C677T (rs1801133) polymorphism was associated with presenting overall adverse events in an allelic model (OR: 1.54; 95% CI: 1.07–2.22) and a dominant model (OR: 1.70; 95% CI: 1.08–2.68). Conclusion: C677T (rs1801133) polymorphism in MTHFR predicts nonresponse and/or adverse effects of MTX treatment in JIA patients.

Methotrexate-Induced Epithelial-Mesenchymal Transition in the Alveolar Epithelial Cell Line A549

PURPOSE

Methotrexate (MTX) therapy of certain cancers and rheumatoid arthritis often induces serious interstitial lung complications including pulmonary fibrosis. In this study, we investigated the epithelial-mesenchymal transition (EMT) induced by MTX and by transforming growth factor (TGF)-β1 in the human alveolar epithelial cell line A549 in order to develop new strategies for the prevention of EMT.

METHODS

First, we examined the effect of TGF-β1 and MTX on cell morphology and the expression of EMT-related mRNAs in A549 cells. Then, the effects of SB431542 (SB), a potent inhibitor of TGF-β receptor kinase, and a neutralizing antibody for TGF-β1 on the phenotypic changes of A549 cells induced by TGF-β1 and MTX were examined.

RESULTS

After incubation with TGF-β1 and MTX, the mRNA expression of epithelial markers such as cytokeratin 19 was reduced, while that of mesenchymal markers such as α-smooth muscle actin was increased. SB suppressed the development of morphological changes and partially rescued alterations in mRNA expression of EMT markers induced by MTX. In addition, the enhancement of SMAD2 phosphorylation by MTX was also prevented by SB. On the other hand, EMT-related changes induced by MTX were not affected by a neutralizing antibody for TGF-β1.

CONCLUSION

We have demonstrated that phenotypic changes of A549 cells induced by MTX are partly mediated by a TGF-β1-related intracellular signaling pathway, although TGF-β1 itself is not directly involved in this process.

The role of synthetic drugs in the biologic era: therapeutic strategies for treating juvenile idiopathic arthritis

INTRODUCTION

Juvenile idiopathic arthritis is the most frequent chronic rheumatic disease in childhood. Synthetic disease modifying drugs (DMARDs) have been used in its treatment since the 1980s and have led to substantial improvement of quality of life and disease outcome. Recent pharmacological research has focused on newer medications, especially biologic agents.

AREAS COVERED

Synthetic DMARDS, especially methotrexate, rightfully remain the first-line treatment of most categories of juvenile arthritis, as attested by several international guidelines. A substantial body of evidence supports these medications, and recent research tries to clarify their optimal use in the clinical setting, both as monotherapy and in combination with biologics. In addition, new forms of synthetic DMARDs are in the research pipeline, or are already used for rheumatoid arthritis.

EXPERT OPINION

Methotrexate remains the preferred first-line medication for polyarticular arthritis, with leflunomide as a viable alternative in case of intolerance or toxicity, despite lack of approval in Europe and the US. Sulfasalazine and hydroxychloroquine are used only rarely in clinical practice, considered in combination with methotrexate if biologics are not available. New synthetic DMARDS are in the research pipeline for JIA, in the form of small molecules.

Life-threatening pneumonitis complicating low-dose methotrexate treatment for juvenile idiopathic arthritis in a child

Methotrexate, a drug commonly used to treat juvenile idiopathic arthritis (JIA), has been reported to cause interstitial pneumonitis as a rare complication in adults with rheumatoid arthritis. Only 1 suspicious case of methotrexate pneumonitis in a child with JIA has been reported in 1998, though with no histopathologic proof. Given its rarity and nonspecific presenting symptoms, diagnosis may be challenging, and a life-threatening illness can occur without a high index of suspicion, as illustrated by this report of a 13-year-old girl with JIA who developed fever, nonproductive cough, and dyspnea as presenting features of interstitial pneumonitis after 1 year of methotrexate therapy. Chest high-resolution computed tomography revealed patchy ground-glass opacities and interlobular septal thickening without pleural effusion. Lung biopsy showed interstitial pneumonitis with diffuse alveolar damage. The symptoms and radiographs improved dramatically after withdrawal of methotrexate and administration of corticosteroids. A restrictive ventilatory defect with decreased diffusion capacity on pulmonary function testing persisted until 20 months after methotrexate withdrawal. There is no single pathognomic feature for methotrexate pneumonitis; rather, diagnosis relies on a constellation of clinical, radiologic, and pathologic findings. This report highlights the necessity for pediatricians to be continuously vigilant for interstitial pneumonitis in children receiving methotrexate who develop new unexplained pulmonary symptoms.

Folate usage in MTX-treated juvenile idiopathic arthritis (JIA) patients is inconsistent and highly variable

Folate supplementation is widely accepted and utilized for the prevention of adverse events in juvenile idiopathic arthritis (JIA) patients who are treated with methotrexate. Despite the widespread use of folate supplementation, there is a lack of convincing evidence to support the role of folate in the enhancement of methotrexate efficacy and the prevention of methotrexate-related adverse events. In order to understand current practices used by experts, we surveyed 214 pediatric rheumatologists around the globe. Seventy-one unique folate supplementation regimens were reported for this study. Results indicated that folate supplementation (either in the form of folic acid or folinic acid) is inconsistent and highly variable within the United States as well as between the United States and other countries. This level of variability is often associated with lack of evidence and emphasizes the need for well-designed clinical trials to support a rational folate supplementation regimen in patients with JIA who are treated with methotrexate.

Drug repositioning in the treatment of malaria and TB

The emergence and spread of drug resistance in the malaria parasite Plasmodium falciparum as well as multi- and extremely drug-resistant forms of Mycobacterium tuberculosis, the causative agent of TB, could hamper the control of these diseases. For instance, there are indications that the malaria parasite is becoming resistant to artemisinin derivatives, drugs that form the backbone of antimalarial combination therapy. Likewise, Mycobacterium tuberculosis strains that are multidrug-resistant or extremely drug-resistant to first- and second-line drugs have been associated with increased mortality. Thus, more than ever, new antimalarials and anti-TB drugs are needed. One of the strategies to discover new drugs is to reposition or repurpose existing drugs, thus reducing the cost and time of drug development. In this review, we discuss how this concept has been used in the past to discover antimalarial and anti-TB drugs, and summarize strategies that can lead to the discovery and development of new drugs.

A phase I trial to evaluate the safety and pharmacokinetics of low-dose methotrexate as an anti-malarial drug in Kenyan adult healthy volunteers

Background

Previous investigations indicate that methotrexate, an old anticancer drug, could be used at low doses to treat malaria. A phase I evaluation was conducted to assess the safety and pharmacokinetic profile of this drug in healthy adult male Kenyan volunteers.

Methods

Twenty five healthy adult volunteers were recruited and admitted to receive a 5 mg dose of methotrexate/day/5 days. Pharmacokinetics blood sampling was carried out at 2, 4, 6, 12 and 24 hours following each dose. Nausea, vomiting, oral ulcers and other adverse events were solicited during follow up of 42 days.

Results

The mean age of participants was 23.9 ± 3.3 years. Adherence to protocol was 100%. No grade 3 solicited adverse events were observed. However, one case of transiently elevated liver enzymes, and one serious adverse event (not related to the product) were reported. The maximum concentration (C_max) was 160-200 nM and after 6 hours, the effective concentration (C_eff) was <150 nM.

Conclusion

Low-dose methotraxate had an acceptable safety profile. However, methotrexate blood levels did not reach the desirable C_eff of 250-400-nM required to clear malaria infection in vivo. Further dose finding and safety studies are necessary to confirm suitability of this drug as an anti-malarial agent.

Methotrexate is highly potent against pyrimethamine-resistant Plasmodium vivax

Resistance of vivax malaria to treatment with antifolates, such as pyrimethamine (Pyr), is spreading as mutations in the dihydrofolatereductase (dhfr) genes are selected and disseminated. We tested the antitumor drug methotrexate (MTX), a potent competitive inhibitor of dhfr, against 11 Plasmodium vivax isolates ex vivo, 10 of which had multiple dhfr mutations associated with Pyr resistance. Despite high-grade resistance to Pyr (median 50% inhibitory concentration [IC₅₀], 13,345 nM), these parasites were all highly susceptible to MTX (median IC₅₀, 2.6 nM). Given its potency against Pyr-resistant P. vivax, the antimalarial potential of MTX deserves further investigation.

Anticancer agents against malaria: time to revisit?

The emergence of artemisinin resistance could adversely impact the current strategy for malaria treatment; thus, new drugs are urgently needed. A possible approach to developing new antimalarials is to find new uses for old drugs. Some anticancer agents such as methotrexate and trimetrexate are active against malaria. However, they are commonly perceived to be toxic and thus not suitable for malaria treatment. In this opinion article, we examine how the toxicity of anticancer agents is just a matter of dose or ‘only dose makes the poison’, as coined in Paracelsus’ law. Thus, the opportunity exists to discover new antimalarials using the anticancer pharmacopoeia.

Long-term safety and effectiveness of etanercept in children with selected categories of juvenile idiopathic arthritis

OBJECTIVE

This study was undertaken to evaluate the long-term safety and effectiveness of etanercept alone or in combination with methotrexate (MTX) in children with selected categories of juvenile idiopathic arthritis (JIA).

METHODS

Patients ages 2-18 years with rheumatoid factor (RF)-positive or RF-negative polyarthritis, systemic JIA, or extended oligoarthritis were eligible for the study. Patients received MTX alone (> or =10 mg/m(2)/week [ approximately 0.3 mg/kg/week], maximum dosage 1 mg/kg/week), etanercept alone (0.8 mg/kg/week, maximum dose 50 mg), or etanercept plus MTX for 3 years in an open-label, nonrandomized study. Safety was assessed by measuring rates of adverse events, and effectiveness was assessed using the physician's global assessment of disease activity and the pediatric total joint assessment.

RESULTS

A total of 197, 103, and 294 patients were enrolled in the MTX, etanercept, and etanercept plus MTX groups, respectively. Exposure-adjusted rates of adverse events were similar among the 3 treatment groups (18.3, 18.7, and 21.6 per 100 patient-years in the MTX, etanercept, and etanercept plus MTX groups, respectively). Respective rates per 100 patient-years of serious adverse events (4.6, 7.1, and 6.0) and medically important infections (1.3, 1.8, and 2.1) were also similar among the 3 treatment groups. Scores for physician's global assessment and total active joints improved from baseline, and improvement was maintained for the duration of the study.

CONCLUSION

These data confirm the findings of other long-term studies and suggest that etanercept or etanercept plus MTX has an acceptable safety and effectiveness profile in children with selected categories of JIA. Improvement was maintained for 3 years in those continuing to receive medication.

In vitro activity of antifolate and polymorphism in dihydrofolate reductase of Plasmodium falciparum isolates from the Kenyan coast: emergence of parasites with Ile-164-Leu mutation

We have analyzed the activities of the antifolates pyrimethamine (PM), chlorcycloguanil (CCG), WR99210, trimethoprim (TMP), methotrexate (MTX), and trimetrexate (TMX) against Kenyan Plasmodium falciparum isolates adapted in vitro for long-term culture. We have also assessed the relationship between these drug activities and mutations in dihydrofolate reductase (dhfr), a domain of the gene associated with antifolate resistance. As expected, WR99210 was the most potent drug, with a median 50% inhibitory concentration (IC50) of <0.075 nM, followed by TMX, with a median IC50 of 30 nM. The median IC50 of CCG was 37.80 nM, and that of MTX was 83.60 nM. PM and TMP were the least active drugs, with median IC50s of 733.26 nM and 29,656.04 nM, respectively. We analyzed parasite dhfr genotypes by the PCR-enzyme restriction technique. No wild-type dhfr parasite was found. Twenty-four of 33 parasites were triple mutants (mutations at codons 108, 51, and 59), and only 8/33 were double mutants (mutations at codons 108 and 51 or at codons 108 and 59). IC50s were 2.1-fold (PM) and 3.6-fold (TMP) higher in triple than in double mutants, though these differences were not statistically significant. Interestingly, we have identified a parasite harboring a mutation at codon 164 (Ile-164-Leu) in addition to mutations at codons 108, 51, and 59. This quadruple mutant parasite had the highest TMP IC50 and was in the upper 10th percentile against PM and CCG. We confirmed the presence of this mutation by sequencing. Thus, TMX and MTX are potent against P. falciparum, and quadruple mutants are now emerging in Africa.

Methotrexate and aminopterin lack in vivo antimalarial activity against murine malaria species

The antifolate anticancer drug methotrexate (MTX) has potent activity against Plasmodium falciparum in vitro. Experience of its use in the treatment of rheumatoid arthritis indicates that it could be safe and efficacious for treating malaria. We sought to establish a murine malaria model to study the mechanism of action and resistance of MTX and its analogue aminopterin (AMP). We used Plasmodium berghei, Plasmodium yoelii yoelii, Plasmodium chabaudi and Plasmodium vinckei. None of these species were susceptible to either drug. We have also tested the efficacy of pyrimethamine in combination with folic acid in P. berghei, and data indicate that folic acid does not influence pyrimethamine efficacy, which suggests that P. berghei may not transport folate. Since MTX and AMP utilise folate receptor/transport to gain access to cells, their lack of efficacy against the four tested murine malaria species may be the result of inefficiency of drug transport.

Pharmacotherapy of Juvenile Idiopathic Arthritis

Juvenile idiopathic arthritis is the most common rheumatic disorder of childhood, and is defined as arthritis beginning prior to the age of 16 years, lasting more than 6 weeks, with an unknown cause. Seven subtypes of juvenile idiopathic arthritis have recently been categorized and named. These subtypes differ broadly in the number of affected joints and the presence of systemic illness. Although many children with juvenile idiopathic arthritis may achieve remission prior to entering adulthood, many others will continue to have debilitating disease into adulthood. Pharmacotherapy plays a major role in the treatment of juvenile idiopathic arthritis. Nonsteroidal anti-inflammatory drugs and corticosteroids can be beneficial for many children and are used as initial therapy. Methotrexate may offer benefits to children unresponsive to these initial agents. Studies evaluating the use of several biologic agents and immunosuppressants have recently been published, and the role of these drugs for children with juvenile idiopathic arthritis is being assessed. Major clinical trials and pediatric implications are reviewed.

Effect of folate derivatives on the activity of antifolate drugs used against malaria and cancer

The folate derivatives folic acid (FA) and folinic acid (FNA) decrease the in vivo and in vitro activities of antifolate drugs in Plasmodium falciparum. However, the effects of 5-methyl-tetrahydrofolate (5-Me-THF) and tetrahydrofolate (THF), the two dominant circulating folate forms in humans, have not been explored yet. We have investigated the effects of FA, FNA, 5-Me-THF, and THF on the in vitro activity of the antimalarial antifolates pyrimethamine and chlorcycloguanil and the anticancer antifolates methotrexate (MTX), aminopterin, and trimetrexate (TMX), against P. falciparum. The results indicate that these anticancers are potent against P. falciparum, with IC50 < 50 nM. 5-Me-THF does not significantly decrease the activity of all tested drugs, and none of the tested folate derivatives significantly decrease the activity of these anticancers. Thus, malaria folate metabolism has features different from those in human, and the exploitation of this difference could lead to the discovery of new drugs to treat malaria. For instance, the combination of 5-Me-THF with a low dose of TMX could be used to treat malaria. In addition, the safety of a low dose of MTX in the treatment of arthritis indicates that this drug could be used alone to treat malaria.