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Methotrexate (MTX) is the first line drug for the treatment of a number of rheumatic and non-rheumatic disorders. It is currently used as an anchor disease, modifying anti-rheumatic drug in the treatment of rheumatoid arthritis (RA). Despite the development of numerous new targeted therapies, MTX remains the backbone of RA therapy due to its potent efficacy and tolerability. There has been also a growing interest in the use of MTX in the treatment of chronic viral mediated arthritis. Many viruses—including old world alphaviruses, Parvovirus B19, hepatitis B/C virus, and human immunodeficiency virus—have been associated with arthritogenic diseases and reminiscent of RA. MTX may provide benefits although with the potential risk of attenuating patients’ immune surveillance capacities. In this review, we describe the emerging mechanisms of action of MTX as an anti-inflammatory drug and complementing its well-established immunomodulatory activity. The mechanisms involve adenosine signaling modulation, alteration of cytokine networks, generation of reactive oxygen species and HMGB1 alarmin suppression. We also provide a comprehensive understanding of the mechanisms of MTX toxic effects. Lastly, we discussed the efficacy, as well as the safety, of MTX used in the management of viral-related rheumatic syndromes.

The growing field of immunometabolism has taught us how metabolic cellular reactions and processes not only provide a means to generate ATP and biosynthetic precursors, but are also a way of controlling immunity and inflammation. Metabolic reprogramming of immune cells is essential for both inflammatory as well as anti-inflammatory responses. Four anti-inflammatory therapies, DMF, Metformin, Methotrexate and Rapamycin all work by affecting metabolism and/or regulating or mimicking endogenous metabolites with anti-inflammatory effects. Evidence is emerging for the targeting of specific metabolic events as a strategy to limit inflammation in different contexts. Here we discuss these recent developments and speculate on the prospect of targeting immunometabolism in the effort to develop novel anti-inflammatory therapeutics. As accumulating evidence for roles of an intricate and elaborate network of metabolic processes, including lipid, amino acid and nucleotide metabolism provides key focal points for developing new therapies, we here turn our attention to glycolysis and the TCA cycle to provide examples of how metabolic intermediates and enzymes can provide potential novel therapeutic targets.

Cancer cells rewire their metabolism and rely on endogenous antioxidants to mitigate lethal oxidative damage to lipids. However, the metabolic processes that modulate the response to lipid peroxidation are poorly defined. Using genetic screens, we compared metabolic genes essential for proliferation upon inhibition of cystine uptake or glutathione peroxidase-4 (GPX4). Interestingly, very few genes were commonly required under both conditions, suggesting that cystine limitation and GPX4 inhibition may impair proliferation via distinct mechanisms. Our screens also identify tetrahydrobiopterin (BH4) biosynthesis as an essential metabolic pathway upon GPX4 inhibition. Mechanistically, BH4 is a potent radical-trapping antioxidant that protects lipid membranes from autoxidation, alone and in synergy with vitamin E. Dihydrofolate reductase catalyzes the regeneration of BH4, and its inhibition by methotrexate synergizes with GPX4 inhibition. Altogether, our work identifies the mechanism by which BH4 acts as an endogenous antioxidant and provides a compendium of metabolic modifiers of lipid peroxidation. Genetic screens reveal a compendium of metabolic modifiers of lipid peroxidation. Tetrahydrobiopterin is essential under GPX4 inhibition, acting as a radical-trapping antioxidant that inhibits lipid peroxidation and is regenerated by DHFR.

Intravenous (IV) and subcutaneous (SC) tocilizumab (RoActemra ® ), an IL-6 receptor antagonist, are approved (± methotrexate) in numerous countries throughout the world, for the treatment of adults with moderate to severe active rheumatoid arthritis (RA). Extensive clinical experience has firmly established the short- and long-term efficacy and safety of tocilizumab [monotherapy or in combination with conventional synthetic DMARDs (csDMARDs)] in adults with early-stage and longer-duration established RA. In the clinical trial and real-world settings, tocilizumab monotherapy or combination therapy provided rapid and sustained improvements in clinical and radiographic outcomes and health-related quality of life. The safety profile of tocilizumab is consistent over time and, in general, is consistent with that of other immunomodulatory agents. This narrative review, written from an EU perspective, summarizes the clinical use of IV and SC tocilizumab in RA. Given its low risk of immunogenicity, the flexibility of IV and SC administration and the convenience of the once-weekly, self-administered, SC regimen, tocilizumab provides an effective treatment for severe, active and progressive RA in adults not previously treated with methotrexate and an effective biologic first- or subsequent-line treatment for moderate to severe active RA in adults who have either responded inadequately to or were intolerant of previous therapy with ≥ 1 csDMARD or TNF inhibitor.

Upadacitinib (Rinvoq™), an orally-administered Janus kinase 1 (JAK-1) inhibitor, is being developed by AbbVie for the treatment of rheumatoid arthritis. In August 2019, based on positive results from multinational phase III trials conducted in patients with rheumatoid arthritis, upadacitinib received marketing approval in the USA for the treatment of moderately to severely active rheumatoid arthritis and an inadequate response or intolerance to methotrexate. This article summarizes the milestones in the development of upadacitinib leading to this first approval for the treatment of rheumatoid arthritis.

The chemotherapeutic drug methotrexate inhibits the enzyme dihydrofolate reductase 1 , which generates tetrahydrofolate, an essential cofactor in nucleotide synthesis 2 . Depletion of tetrahydrofolate causes cell death by suppressing DNA and RNA production 3 . Although methotrexate is widely used as an anticancer agent and is the subject of over a thousand ongoing clinical trials 4 , its high toxicity often leads to the premature termination of its use, which reduces its potential efficacy 5 . To identify genes that modulate the response of cancer cells to methotrexate, we performed a CRISPR–Cas9-based screen 6 , 7 . This screen yielded FTCD , which encodes an enzyme—formimidoyltransferase cyclodeaminase—that is required for the catabolism of the amino acid histidine 8 , a process that has not previously been linked to methotrexate sensitivity. In cultured cancer cells, depletion of several genes in the histidine degradation pathway markedly decreased sensitivity to methotrexate. Mechanistically, histidine catabolism drains the cellular pool of tetrahydrofolate, which is particularly detrimental to methotrexate-treated cells. Moreover, expression of the rate-limiting enzyme in histidine catabolism is associated with methotrexate sensitivity in cancer cell lines and with survival rate in patients. In vivo dietary supplementation of histidine increased flux through the histidine degradation pathway and enhanced the sensitivity of leukaemia xenografts to methotrexate. The histidine degradation pathway markedly influences the sensitivity of cancer cells to methotrexate and may be exploited to improve methotrexate efficacy through a simple dietary intervention. Histidine metabolism influences the sensitivity of cancer cells to methotrexate, with mice bearing leukaemia xenografts showing increased response to the drug upon histidine supplementation.

Key Points Methotrexate shows good efficacy in a proportion of patients: 40% of treated patients with rheumatoid arthritis achieve an ACR50 response The mechanism of action of methotrexate has not fully been defined, however potentiation of adenosine signalling carries the most robust data Pharmacokinetic parameters, particularly intracellular methotrexate polyglutamation, show some association with disease activity, although they cannot yet be used to predict treatment response An exploration of the expression and polymorphisms of genes encoding molecules linked to proposed mechanisms of methotrexate action is underway to identify methotrexate-responsive signatures At present, no robust markers or predictive models exist for methotrexate responsiveness in RA Methotrexate remains the first-line therapy for rheumatoid arthritis (RA). However, not all treated patients respond, and its mechanism of action remains incompletely understood. This Review describes putative mechanisms of action of methotrexate at the low doses used in RA and discusses potential biomarkers of treatment response, which could ultimately inform precision use of this therapy. The treatment and outcomes of patients with rheumatoid arthritis (RA) have been transformed over the past two decades. Low disease activity and remission are now frequently achieved, and this success is largely the result of the evolution of treatment paradigms and the introduction of new therapeutic agents. Despite the rapid pace of change, the most commonly used drug in RA remains methotrexate, which is considered the anchor drug for this condition. In this Review, we describe the known pharmacokinetic properties and putative mechanisms of action of methotrexate. Consideration of the pharmacodynamic perspective could inform the development of biomarkers of responsiveness to methotrexate, enabling therapy to be targeted to specific groups of patients. Such biomarkers could revolutionize the management of RA.

Since its discovery in 1945, methotrexate has become a standard therapy for number of diseases, including oncological, inflammatory and pulmonary ones. Major physiological interactions of methotrexate include folate pathway, adenosine, prostaglandins, leukotrienes and cytokines. Methotrexate is used in treatment of pulmonary sarcoidosis as a second line therapy and is drug of choice in patients who are not candidates for corticosteroid therapy, with recommended starting weekly dose of 5–15 mg. Number of studies dealt with methotrexate use in rheumatoid arthritis and oncological patients. Authors are conducting research on oral methotrexate use and pharmacokinetics in chronic sarcoidosis patients and have performed literature research to better understand molecular mechanisms of methotrexate action as well as high level pharmacokinetic considerations. Polyglutamation of methotrexate affects its pharmacokinetic and pharmacodynamic properties and prolongs its effect. Bile excretion plays significant role due to extensive enterohepatic recirculation, although majority of methotrexate is excreted through urine. Better understanding of its pharmacokinetic properties in sarcoidosis patients warrant optimizing therapy when corticosteroids are contraindicated in these patients.

The recently identified Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is the cause of the COVID-19 pandemic. How this novel beta-coronavirus virus, and coronaviruses more generally, alter cellular metabolism to support massive production of ~30 kB viral genomes and subgenomic viral RNAs remains largely unknown. To gain insights, transcriptional and metabolomic analyses are performed 8 hours after SARS-CoV-2 infection, an early timepoint where the viral lifecycle is completed but prior to overt effects on host cell growth or survival. Here, we show that SARS-CoV-2 remodels host folate and one-carbon metabolism at the post-transcriptional level to support de novo purine synthesis, bypassing viral shutoff of host translation. Intracellular glucose and folate are depleted in SARS-CoV-2-infected cells, and viral replication is exquisitely sensitive to inhibitors of folate and one-carbon metabolism, notably methotrexate. Host metabolism targeted therapy could add to the armamentarium against future coronavirus outbreaks. Viruses rely on host metabolism for replication. Here, the authors perform transcriptional and metabolomic analyses at 8 hours after SARS-CoV-2 infection and find that the virus alters host folate and one-carbon metabolism at a post-transcriptional level.

Carbon nanotubes (CNTs) have the potential to serve as delivery systems for medicinal substances and gene treatments, particularly in cancer treatment. Co-delivery of curcumin (CUR) and Methotrexate (MTX) has shown promise in cancer treatment, as it uses fewer drugs and has fewer side effects. This study used MTX-conjugated albumin (BSA)-based nanoparticles (BSA-MTX) to enhance and assess the efficiency of CUR. In-vitro cytotoxicity tests, DLS, TEM, FTIR, UV/Vis, SEM, and DSC studies assessed the formulations' physical and chemical properties. The Proteinase K enzyme was used to severe amidic linkages between MTX and BSA. The findings demonstrated the efficacy of using ƒ-MWCNT-CUR-BSA-MTX as a vehicle for efficient co-delivery of CUR and MTX in cancer treatment. The MTT colorimetric method was used to evaluate the effect of chemical and medicinal compounds. Cell division was studied using the MTT method to investigate the effect of pure MWCNT, pure CUR, MTX-BSA, and ƒ-MWCNT-CUR-MTX-BSA. Studies on cell lines have shown that the combination of curcumin and MTX with CNT can increase and improve the effectiveness of both drugs against cancer. A combination of drugs curcumin and methotrexate simultaneously had a synergistic effect on MCF-7 cells, which indicated that these drugs could potentially be used as a strategy for both prevention and treatment of breast cancer. Also, ƒ-MWCNT-CUR-MTX-BSA was found to have a significant effect on cancer treatment with minimal toxicity compared to pure curcumin, pure MTX-BSA, MTX, and ƒ-MWCNT alone. Unique properties such as a high ratio of specific surface area to volume, high chemical stability, chemical adsorption ability, high capacity of drug and biomolecules of carbon nanotubes, as well as multiple drug loading at the same time The combination of ƒ-MWCNT-CUR-BSA MTX significantly impacts cancer therapy), are desirable as an alternative option for targeted drug delivery and high therapeutic efficiency.