Methotrexate

Methotrexate, a folate antagonist, is a potent anti-inflammatory agent when used weekly in low concentrations, the anti-phlogistic action of which is due to increased adenosine release at inflamed sites. Studies have demonstrated that methotrexate polyglutamates are active inhibitors of several enzymatic reactions, including dihydrofolate reductase. On consideration of biochemical pharmacology of methotrexate of methotrexate, it is taken up by cells and tissues and converted to methotrexate–polyglutamates, long-lived derivatives that retain biochemical and biologic activity within the cell. There is evidence that methotrexate does not act in rheumatoid arthritis (RA) simply as a cytotoxic agent for the cells responsible for the inflammation.

Reference

Bruce N. Cronstein, Dwight Naime, Edward Ostad. The antiinflammatory mechanism of methotrexate. Increased adenosine release at inflamed sites diminishes leukocyte accumulation in an in vivo model of inflammation. Journal of Clinical Investigation. 1993 December; 92(6): 2675–2682.

Bruce N. Cronstein. The mechanism of action of methotrexate. Rheumatic Disease Clinics of North America Volume 23, Issue 4, 1 November 1997, Pages 739–755.

Predictors of overall survival among patients treated with sirolimus/tacrolimus vs methotrexate/tacrolimus for GvHD prevention.[Pubmed:28368376]

Bone Marrow Transplant. 2017 Jul;52(7):1003-1009.

Sirolimus (SIR)/tacrolimus (TAC) is an alternative to Methotrexate (MTX)/TAC. However, rational selection among these GvHD prophylaxis approaches to optimize survival of individual patients is not possible based on current evidence. We compared SIR/TAC (n=293) to MTX/TAC (n=414). The primary objective was to identify unique predictors of overall survival (OS). Secondary objective was to compare acute and chronic GvHD, relapse, non-relapse mortality, thrombotic microangiopathy (TMA), hepatic veno-occlusive disease (VOD/SOS), and acute kidney injury. Day 100 grades II-IV acute GvHD was significantly reduced in SIR/TAC vs MTX/TAC group (63 vs 73%, P=0.02). An interaction between GvHD prophylaxis groups and comorbidity index (hematopoietic cell transplantation (HCT)-CI) significantly impacted OS. Patients with HCT-CI4 had significantly worse OS with MTX/TAC (HR 1.86, 95% CI 1.14-3.04, P=0.01) while no such effect was seen for SIR/TAC (HR 0.78, 95% CI 0.48-1.26, P=0.31). Other end points did not significantly differ between groups except TMA and VOD/SOS were increased in the SIR/TAC group, but excess death from these complications was not observed. We conclude, GvHD prophylaxis approach of SIR/TAC is associated with reduced grades II-IV acute GvHD, comparable toxicity profile to MTX/TAC, and improved OS among patients with HCT-CI4.

Sequence-Defined Oligoamide Drug Conjugates of Pretubulysin and Methotrexate for Folate Receptor Targeted Cancer Therapy.[Pubmed:28371444]

Macromol Biosci. 2017 Oct;17(10).

The conjugation of small molecule drugs to ligand containing carrier systems facilitates receptor targeted delivery. The folate receptor (FR) constitutes an ideal target for tumor selective therapy, being overexpressed on several tumor types. It can be targeted using the vitamin folic acid (FolA) or the structurally related drug Methotrexate (MTX). Several sequence-defined oligoamides with mono- and multivalent FolA or MTX ligands and an additional thiol conjugation site are synthesized via solid-phase assisted synthesis. Their structure activity relationships are assessed in respect to dihydrofolate reductase inhibition, receptor mediated endocytosis, and cytotoxicity. Then, the tubulin-binding agent pretubulysin (PT), a highly potent drug exhibiting antitumoral, antiangiogenic, and antimetastatic properties, is conjugated via an activated mercaptane derivative to the set of FR-targeting oligoamides. In a combined PT/MTX cytotoxicity study in FR-overexpressing KB and L1210 cells, a 2-arm MTX-PT construct or the 4-arm analog displays the highest potency in the respective cell lines.

Dietary Intake of Polyunsaturated Fatty Acids and Pain in Spite of Inflammatory Control Among Methotrexate-Treated Early Rheumatoid Arthritis Patients.[Pubmed:28371257]

Arthritis Care Res (Hoboken). 2018 Feb;70(2):205-212.

OBJECTIVE: To investigate potential associations between dietary intake of polyunsaturated fatty acids (FAs) and pain patterns in early rheumatoid arthritis (RA) patients after 3 months of Methotrexate (MTX) treatment. METHODS: We included 591 early RA patients with MTX monotherapy from a population-based prospective case-control study, the Epidemiological Investigation of Rheumatoid Arthritis. Dietary data on polyunsaturated FAs (food frequency questionnaires) were linked with data on unacceptable pain (visual analog scale [VAS] >40 mm), noninflammatory/refractory pain (VAS >40 mm and C-reactive protein [CRP] level <10 mg/liter), and inflammatory pain (VAS >40 mm and CRP level >10 mg/liter) after 3 months. Statistical analysis included logistic regression. RESULTS: After 3 months of MTX treatment, 125 patients (21.2%) had unacceptable pain, of which 92 patients had refractory pain, and 33 patients had inflammatory pain. Omega-3 FA intake was inversely associated with unacceptable pain and refractory pain (odds ratio [OR] 0.57 [95% confidence interval (95% CI) 0.35-0.95] and OR 0.47 [95% CI 0.26-0.84], respectively). The omega-6:omega-3 FA ratio, but not omega-6 FA alone, was directly associated with unacceptable pain and refractory pain (OR 1.70 [95% CI 1.03-2.82] and OR 2.33 [95% CI 1.28-4.24], respectively). Furthermore, polyunsaturated FAs were not associated with either inflammatory pain or CRP level and erythrocyte sedimentation rate at followup. Omega-3 FA supplementation was not associated with any pain patterns. CONCLUSION: Omega-3 FA was inversely associated with, and the omega-6:omega-3 FA ratio was directly associated with, unacceptable and refractory pain, but not with inflammatory pain or systemic inflammation. The inverse association between omega-3 FA and refractory pain may have a role in pain suppression in RA.

Single-dose methotrexate for the treatment of ectopic pregnancy: Our experience from 2010 to 2015.[Pubmed:28367164]

Pak J Med Sci. 2017 Jan-Feb;33(1):13-17.

OBJECTIVE: To evaluate the success of systemic single-dose Methotrexate (MTX) treatment in patients with ectopic pregnancy (EP) and to investigate factors related to treatment success. METHODS: This retrospective study had been performed in Yildirim Beyazit University between January 2010 and December 2015. Demographic and clinical characteristics, ultrasonografic findings, pretreatment serum beta-human chorionic gonadotropin (beta-hCG) and progesterone levels of 58 patients with EP were retrieved from hospital records retrospectively. The patients were grouped according to MTX treatment success (response vs. failure). RESULTS: Single-dose MTX-treatment was successful in 72.4% (42/58) of patients. The mean pretreatment beta-hCG level was significantly lower in responders than in failures (2080 +/- 2322 vs. 5707 +/- 3885 IU/L, p = 0.001), and 2678 IU/L was the most suitable cutoff to predict success (75% sensitivity, 73.8% specificity). Moreover, failure rate was 8.45 times more in group of patients whose beta-hCG values were determined above the cutoff. The presence of fetal cardiac activity adversely affected treatment success (odds ratio = 12, p = 0.004). Treatment success was not affected by past history of ectopic pregnancy, thickness of endometrium, progesterone value or presences of pseudosac and free pelvic fluid. CONCLUSION: The success rate of single dose MTX in this study was 72.8 %, and we found that failure rate of MTX treatment was 8.45 times more in group of patients whose initial serum beta-hCG values were above 2678 IU/L and 12 times more in patients with fetal cardiac activity.

Targeting Ras signaling through inhibition of carboxyl methylation: an unexpected property of methotrexate.[Pubmed:12750467]

Proc Natl Acad Sci U S A. 2003 May 27;100(11):6529-34.

The antifolate Methotrexate is one of the most successful drugs in cancer chemotherapy. Although its efficacy is widely attributed to a decrease in nucleotide biosynthesis (1), Methotrexate is known to increase homocysteine (2), a compound associated with an elevated risk of heart disease, Alzheimer's disease (3), and neural tube defects (4). A potential mechanism for the detrimental effects of homocysteine is cellular hypomethylation from an increase in S-adenosylhomocysteine (5), an inhibitor of methyltransferases including isoprenylcysteine carboxyl methyltransferase (Icmt). Among the substrates of Icmt is the monomeric G protein Ras, a critical component of many signaling pathways that regulate cell growth and differentiation. Because carboxyl methylation of Ras is important for proper plasma membrane localization and function (6), we investigated the role of Icmt in the antiproliferative effect of Methotrexate. After Methotrexate treatment of DKOB8 cells, Ras methylation is decreased by almost 90%. This hypomethylation is accompanied by a mislocalization of Ras to the cytosol and a 4-fold decrease in the activation of p44 mitogen-activated protein kinase and Akt. Additionally, cells lacking Icmt are highly resistant to Methotrexate. Whereas cells expressing wild-type levels of Icmt are inhibited by Methotrexate, stable expression of myristoylated H-Ras, which does not require carboxyl methylation for membrane attachment (7), confers resistance to Methotrexate. These results suggest that inhibition of Icmt is a critical component of the antiproliferative effect of Methotrexate, expanding our understanding of this widely used drug and identifying Icmt as a target for drug discovery.

Mechanism of thymidylate synthase inhibition by methotrexate in human neoplastic cell lines and normal human myeloid progenitor cells.[Pubmed:2341391]

J Biol Chem. 1990 May 25;265(15):8470-8.

We have studied the roles of 5,10-methylenetetrahydrofolate (5,10-methylene-H4PteGlu) depletion and dihydrofolate (H2PteGlu) accumulation in the inhibition of de novo thymidylate synthesis by Methotrexate (MTX) in human MCF-7 breast cancer cells. Using both a high pressure liquid chromatography system and a modification of the 5-fluoro-2'-deoxyuridine-5'-monophosphate radioenzymatic binding assay, we determined that the 5,10-methylene-H4PteGlu pool is 50-60% depleted in human MCF-7 breast cancer cells following exposure to 1 micron MTX for up to 21 h. Similar alterations in the 5,10-methylene-H4PteGlu pools were obtained when human promyelocytic HL-60 leukemia cells and normal human myeloid precursor cells were incubated with 1 micron MTX. The H2PteGlu pools within the MCF-7 cells increased significantly after 15 min of 1 micron MTX exposure, reaching maximal levels by 60 min. Thymidylate synthesis, as measured by labeled deoxyuridine incorporation into DNA, decreased to less than 20% of control activity within 30 min of 1 micron MTX exposure. The inhibition of thymidylate synthesis coincided temporally with the rapid intracellular accumulation of H2PteGlu, a known inhibitor of thymidylate synthase. Furthermore, inhibition of this pathway was associated in a log-linear fashion with the intracellular level of dihydrofolate. These studies provide further evidence that depletion of the thymidylate synthase substrate 5,10-methylene-H4PteGlu is inadequate to account completely for diminished thymidylate synthesis resulting from MTX treatment. Our findings suggest that acute inhibition of de novo thymidylate synthesis is a multifactorial process consisting of partial substrate depletion and direct enzymatic inhibition by H2PteGlu polyglutamates.

Evidence for direct inhibition of de novo purine synthesis in human MCF-7 breast cells as a principal mode of metabolic inhibition by methotrexate.[Pubmed:2443493]

J Biol Chem. 1987 Oct 5;262(28):13520-6.

We have investigated the role of dihydrofolate (H2PteGlu) accumulation in the inhibition of de novo purine synthesis by Methotrexate (MTX) in human MCF-7 breast cancer cells. Previous studies have shown that cytotoxic concentrations of MTX that inhibit dihydrofolate reductase produce only minimal depletion of the reduced folate cofactor, 10-formyltetrahydrofolate, required for purine synthesis. At the same time, de novo purine synthesis is totally inhibited. In these studies, we show that 10 microM MTX causes inhibition of purine synthesis at the step of phosphoribosylaminoimidazolecarboxamide (AICAR) transformylase, as reflected in a 2-3-fold expansion of the intracellular AICAR pool. The inhibition of purine synthesis coincides with the rapid intracellular accumulation of H2PteGlu, a known inhibitor of AICAR transformylase. When the generation of H2PteGlu is blocked by pretreatment with 50 microM 5-fluorodeoxyuridine (FdUrd), an inhibitor of thymidylate synthase, MTX no longer causes inhibition of purine synthesis. Intermediate levels of H2PteGlu produced in the presence of lower (0.1-10 microM) concentrations of FdUrd led to proportional inhibition of purine biosynthesis, and the exogenous addition of H2PteGlu to breast cells in culture re-established the block in purine synthesis in the presence of FdUrd and MTX. The early phases of inhibition of purine biosynthesis could be ascribed only to H2PteGlu accumulation. MTX polyglutamates, also known to inhibit AICAR transformylase, were present in breast cells only after 6 h of incubation with the parent compounds and were not formed in cells preincubated with FdUrd. The lipid-soluble antifolate trimetrexate, which does not form polyglutamates, produced modest 10-formyltetrahydrofolate depletion, but caused marked H2PteGlu accumulation and a parallel inhibition of purine biosynthesis. This evidence leads to the conclusion that MTX and the lipid-soluble analog trimetrexate cause inhibition of purine biosynthesis through the accumulation of H2PteGlu behind the blocked dihydrofolate reductase reaction.

Methotrexate (Amethopterin) is an antimetabolite and antifolate agent that inhibits the enzyme dihydrofolate reductase, thereby preventing the conversion of folic acid into tetrahydrofolate, and inhibiting DNA synthesis. Methotrexate (Amethopterin) is the disease-modifying antirheumatic drug (DMARD) of first choice for the treatment of RA in most countries worldwide. Methotrexate is an antineoplastic agent used to fight a number of different cancers, such as acute lymphoblastic leukemia and solid cancers.

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