Other nervous system drugs. ATC Code:
Pharmacology: Pharmacodynamics: Mechanism of Action:
The mechanism by which dimethyl fumarate exerts therapeutic effects in multiple sclerosis is not fully understood. Preclinical studies indicate that dimethyl fumarate pharmacodynamic responses appear to be primarily mediated through activation of the Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) transcriptional pathway. Dimethyl fumarate has been shown to up regulate Nrf2-dependent antioxidant genes in patients (e.g. NAD(P)H dehydrogenase, quinone 1; [NQO1]).
Effects on the Immune System: In preclinical and clinical studies, Tecfidera demonstrated anti-inflammatory and immunomodulatory properties. Dimethyl fumarate and monomethyl fumarate, the primary metabolite of dimethyl fumarate, significantly reduced immune cell activation and subsequent release of pro-inflammatory cytokines in response to inflammatory stimuli in preclinical models. In clinical studies with psoriasis patients, dimethyl fumarate affected lymphocyte phenotypes through a down-regulation of pro-inflammatory cytokine profiles (TH
17), and biased towards anti-inflammatory production (TH
2). Dimethyl fumarate demonstrated therapeutic activity in multiple models of inflammatory and neuroinflammatory injury. In Phase 3 studies, upon treatment with Tecfidera mean lymphocyte counts decreased on average by approximately 30% of their baseline value over the first year with a subsequent plateau.
Effect on Cardiovascular System: Single doses of 240 mg or 360 mg Tecfidera did not have any effect on the QTc interval when compared to placebo in a QTc study.
Clinical Efficacy and Safety:
Two, 2-year, randomised, double-blind, placebo controlled studies [Study 1 (DEFINE) with 1,234 subjects and Study 2 (CONFIRM) with 1,417 subjects] of subjects with relapsing-remitting multiple sclerosis (RRMS) were performed. Subjects with progressive forms of MS were not included in these studies. Efficacy (see Table 1) and safety were demonstrated in subjects with Expanded Disability Status Scale (EDSS) scores ranging from 0 to 5 inclusive, who had experienced at least 1 relapse during the year prior to randomisation, or, within 6 weeks of randomisation had a brain Magnetic Resonance Imaging (MRI) demonstrating at least one gadolinium-enhancing (Gd+) lesion. Study 2 contained a rater-blinded (i.e. study physician/ investigator assessing the response to study treatment was blinded) reference comparator of glatiramer acetate.
In Study 1, patients had the following median baseline characteristics: Age 39 years, disease duration 7.0 years, EDSS score 2.0. In addition, 16% of patients had an EDSS score >3.5, 28% had ≥2 relapses in the prior year and 42% had previously received other approved MS treatments. In the MRI cohort 36% of patients entering the study had Gd+ lesions at baseline (mean number of Gd+ lesions 1.4).
In Study 2, patients had the following median baseline characteristics: Age 37 years, disease duration 6.0 years, EDSS score 2.5. In addition, 17% of patients had an EDSS score >3.5, 32% had ≥2 relapses in the prior year and 30% had previously received other approved MS treatments. In the MRI cohort 45% of patients entering the study had Gd+ lesions at baseline (mean number of Gd+ lesions 2.4).
Compared to placebo, subjects treated with Tecfidera had a clinically meaningful and statistically significant reduction on: the primary endpoint in Study 1, proportion of subjects relapsed at 2 years; and the primary endpoint in Study 2, annualised relapse rate at 2 years.
The annualised relapse rate for glatiramer acetate and placebo was 0.286 and 0.401 respectively in Study 2, corresponding to a reduction of 29% (p=0.013), which is consistent with approved prescribing information. (See Table 1.)
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Efficacy in Patients with High Disease Activity: Consistent treatment effect on relapses in a subgroup of patients with high disease activity was observed, whilst the effect on time to 3-month sustained disability progression was not clearly established. Due to the design of the studies, high disease activity was defined as follows: Patients with 2 or more relapses in one year, and with one or more Gd-enhancing lesions on brain MRI (n=42 in DEFINE; n=51 in CONFIRM) or, patients who have failed to respond to a full and adequate course (at least one year of treatment) of beta-interferon, having had at least 1 relapse in the previous year while on therapy, and at least 9 T2-hyperintense lesions in cranial MRI or at least 1 Gd-enhancing lesion, or patients having an unchanged or increased relapse rate in the prior year as compared to the previous 2 years (n=177 in DEFINE; n=141 in CONFIRM).
The European Medicines Agency has deferred the obligation to submit the results of studies with Tecfidera in one or more subsets of the paediatric population in multiple sclerosis (see Dosage & Administration for information on paediatric use).
Orally administered Tecfidera (dimethyl fumarate) undergoes rapid presystemic hydrolysis by esterases and is converted to its primary metabolite, monomethyl fumarate, which is also active. Dimethyl fumarate is not quantifiable in plasma following oral administration of Tecfidera. Therefore, all pharmacokinetic analyses related to dimethyl fumarate were performed with plasma monomethyl fumarate concentrations. Pharmacokinetic data were obtained in subjects with multiple sclerosis and healthy volunteers.
of monomethyl fumarate is 2 to 2.5 hours. As Tecfidera gastro-resistant hard capsules contain microtablets, which are protected by an enteric coating, absorption does not commence until they leave the stomach (generally less than 1 hour). Following 240 mg twice a day administered with food, the median peak (Cmax
) was 1.72 mg/L and overall (AUC) exposure was 8.02 h·mg/L in subjects with multiple sclerosis. Overall, Cmax
and AUC increased approximately dose-proportionally in the dose range studied (120 mg to 360 mg). In subjects with multiple sclerosis, two 240 mg doses were administered 4 hours apart as part of a three times a day dosing regimen. This resulted in a minimal accumulation of exposure yielding an increase in the median Cmax
of 12% compared to the twice daily dosing (1.72 mg/L for twice daily compared to 1.93 mg/L for three times daily) with no safety implications.
Food does not have a clinically significant effect on exposure of dimethyl fumarate. However, Tecfidera should be taken with food due to improved tolerability with respect to flushing or gastrointestinal adverse events (see Dosage & Administration).
The apparent volume of distribution following oral administration of 240 mg Tecfidera varies between 60 L and 90 L. Human plasma protein binding of monomethyl fumarate generally ranges between 27% and 40%.
In humans, dimethyl fumarate is extensively metabolised with less than 0.1% of the dose excreted as unchanged dimethyl fumarate in urine. It is initially metabolised by esterases, which are ubiquitous in the gastrointestinal tract, blood and tissues, before it reaches the systemic circulation. Further metabolism occurs through the tricarboxylic acid cycle, with no involvement of the cytochrome P450 (CYP) system. A single 240 mg 14
C-dimethyl fumarate dose study identified glucose as the predominant metabolite in human plasma. Other circulating metabolites included fumaric acid, citric acid and monomethyl fumarate. The downstream metabolism of fumaric acid occurs through the tricarboxylic acid cycle, with exhalation of CO2
serving as a primary route of elimination.
Exhalation of CO2
is the primary route of dimethyl fumarate elimination accounting for 60% of the dose. Renal and faecal elimination are secondary routes of elimination, accounting for 15.5% and 0.9% of the dose respectively.
The terminal half-life of monomethyl fumarate is short (approximately 1 hour) and no circulating monomethyl fumarate is present at 24 hours in the majority of individuals. Accumulation of parent drug or monomethyl fumarate does not occur with multiple doses of dimethyl fumarate at the therapeutic regimen.
Dimethyl fumarate exposure increases in an approximately dose proportional manner with single and multiple doses in the 120 mg to 360 mg dose range studied.
Pharmacokinetics in special patient groups:
Based on the results of Analysis of Variance (ANOVA), body weight is the main covariate of exposure (by Cmax
and AUC) in relapsing remitting multiple sclerosis (RRMS) subjects, but did not affect safety and efficacy measures evaluated in the clinical studies.
Gender and age did not have a clinically significant impact on the pharmacokinetics of dimethyl fumarate. The pharmacokinetics in patients aged 65 and over has not been studied.
The pharmacokinetics in patients below the age of 18 has not been studied.
Since the renal pathway is a secondary route of elimination for dimethyl fumarate accounting for less than 16% of the dose administered, evaluation of pharmacokinetics in individuals with renal impairment was not conducted.
As dimethyl fumarate and monomethyl fumarate are metabolised by esterases, without the involvement of the CYP450 system, evaluation of phamacokinetics in individuals with hepatic impairment was not conducted.
Toxicology: Preclinical Safety Data:
The adverse reactions described in the Toxicology and Reproduction toxicity sections below were not observed in clinical studies, but were seen in animals at exposure levels similar to clinical exposure levels.
Dimethyl fumarate and mono-methylfumarate were negative in a battery of in vitro
assays (Ames, chromosomal aberration in mammalian cells). Dimethyl fumarate was negative in the in vivo
micronucleus assay in the rat.
Carcinogenicity studies of dimethyl fumarate were conducted for up to 2 years in mice and rats. Dimethyl fumarate was administered orally at doses of 25, 75, 200 and 400 mg/kg/day in mice, and at doses of 25, 50, 100, and 150 mg/kg/day in rats. In mice, the incidence of renal tubular carcinoma was increased at 75 mg/kg/day, at equivalent exposure (AUC) to the recommended human dose. In rats, the incidence of renal tubular carcinoma was increased at 100 mg/kg/day, approximately 3 times higher exposure than the recommended human dose. The relevance of these findings to human risk is unknown.
The incidence of squamous cell papilloma and carcinoma in the nonglandular stomach (forestomach) was increased at equivalent exposure to the recommended human dose in mice and below exposure to the recommended human dose in rats (based on AUC). The forestomach in rodents does not have a human counterpart.
Nonclinical studies in rodent, rabbits, and monkeys were conducted with a dimethyl fumarate suspension (dimethyl fumarate in 0.8% hydroxypropyl methylcellulose) administered by oral gavage. The chronic dog study was conducted with oral administration of the dimethyl fumarate capsule.
Kidney changes were observed after repeated oral administration of dimethyl fumarate in mice, rats, dogs, and monkeys. Renal tubule epithelial regeneration, suggestive of injury, was observed in all species. Renal tubular hyperplasia was observed in rats with life time dosing (2-year study). Cortical atrophy was observed in dogs and monkeys, and single cell necrosis and interstitial fibrosis were observed in monkeys that received daily oral doses of dimethyl fumarate for 12 months, at 6 times the recommended dose based on AUC. The relevance of these findings to humans is not known.
In the testes, degeneration of the seminiferous epithelium was seen in rats and dogs. The findings were observed at approximately the recommended dose in rats and 6 times the recommended dose in dogs (AUC basis). The relevance of these findings to humans is not known.
Findings in the forestomach of mice and rats consisted of squamous epithelial hyperplasia and hyperkeratosis; inflammation; and squamous cell papilloma and carcinoma in studies of 3 months or longer in duration. The forestomach of mice and rats does not have a human counterpart.
Oral administration of dimethyl fumarate to male rats at 75, 250, and 375 mg/kg/day prior to and during mating had no effects on male fertility up to the highest dose tested (at least 2 times the recommended dose on an AUC basis). Oral administration of dimethyl fumarate to female rats at 25, 100, and 250 mg/kg/day prior to and during mating, and continuing to Day 7 of gestation, induced reduction in the number of estrous stages per 14 days and increased the number of animals with prolonged diestrus at the highest dose tested (11 times the recommended dose on an AUC basis). However, these changes did not affect fertility or the number of viable fetuses produced.
Dimethyl fumarate has been shown to cross the placental membrane into fetal blood in rats and rabbits, with ratios of fetal to maternal plasma concentrations of 0.48 to 0.64 and 0.1 respectively. No malformations were observed at any dose of dimethyl fumarate in rats or rabbits. Administration of dimethyl fumarate at oral doses of 25, 100, and 250 mg/kg/day to pregnant rats during the period of organogenesis resulted in maternal adverse effects at 4 times the recommended dose on an AUC basis, and low fetal weight and delayed ossification (metatarsals and hindlimb phalanges) at 11 times the recommended dose on an AUC basis. The lower fetal weight and delayed ossification were considered secondary to maternal toxicity (reduced body weight and food consumption).
Oral administration of dimethyl fumarate at 25, 75, and 150 mg/kg/day to pregnant rabbits during organogenesis had no effect on embryo-fetal development and resulted in reduced maternal body weight at 7 times the recommended dose and increased abortion at 16 times the recommended dose, on an AUC basis.
Oral administration of dimethyl fumarate at 25, 100, and 250 mg/kg/day to rats during pregnancy and lactation resulted in lower body weights in the F1 offspring, and delays in sexual maturation in F1 males at 11 times the recommended dose on an AUC basis. There were no effects on fertility in the F1 offspring. The lower offspring body weight was considered secondary to maternal toxicity.