Pharmacological properties : תכונות פרמקולוגיות

Pharmacodynamic Properties

5.1   Pharmacodynamic properties
Pharmacotherapeutic group: Antineoplastic and immunomodulating agents, ATC code: L04AX07 
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]).

Pharmacodynamic effects

Effects on the immune system
In preclinical and clinical studies, dimethyl fumarate 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 (TH1, TH17), and biased towards anti-inflammatory production (TH2). Dimethyl fumarate demonstrated therapeutic activity in multiple models of inflammatory and neuroinflammatory injury. In Phase 3 studies in MS patients, 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.

Clinical efficacy and safety

Two, 2-year, randomised, double-blind, placebo controlled studies [Study 1 (DEFINE) with 1234 subjects and Study 2 (CONFIRM) with 1417 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 below) 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, in the 6 weeks before 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.
12
DEFINE                            CONFIRM
Placebo    Tecfidera          Placebo    Tecfidera   Glatiramer
240 mg                        240 mg      acetate twice a day                   twice a day
Clinical Endpointsa
No. subjects                  408        410               363        359               350 Annualised relapse rate       0.364      0.172***          0.401      0.224***          0.286* Rate ratio                        0.47                         0.56              0.71 (95% CI)                          (0.37, 0.61)                 (0.42, 0.74)      (0.55, 0.93) Proportion relapsed           0.461      0.270***          0.410      0.291**           0.321** Hazard ratio                      0.51                         0.66              0.71 (95% CI)                          (0.40, 0.66)                 (0.51, 0.86)      (0.55, 0.92) Proportion with 12-week       0.271      0.164**           0.169      0.128#            0.156# confirmed disability progression
Hazard ratio                      0.62                         0.79              0.93 (95% CI)                          (0.44, 0.87)                 (0.52, 1.19)      (0.63, 1.37) Proportion with 24 week       0.169      0.128#            0.125      0.078#            0.108# confirmed disability progression
Hazard ratio                      0.77                         0.62              0.87 (95% CI)                          (0.52, 1.14)                 (0.37, 1.03)      (0.55, 1.38) MRI Endpointsb
No. subjects                  165        152               144        147               161 Mean (median) number of 16.5             3.2               19.9       5.7               9.6 new or newly enlarging        (7.0)      (1.0)***          (11.0)     (2.0)***          (3.0)*** T2 lesions over 2 years
Lesion mean ratio                 0.15                         0.29              0.46 (95% CI)                          (0.10, 0.23)                 (0.21, 0.41)      (0.33, 0.63) Mean (median) number of 1.8              0.1               2.0        0.5               0.7 Gd lesions at 2 years         (0)        (0)***            (0.0)      (0.0)***          (0.0)** Odds ratio                        0.10                         0.26              0.39 (95% CI)                          (0.05, 0.22)                 (0.15, 0.46)      (0.24, 0.65) Mean (median) number of 5.7              2.0               8.1        3.8               4.5 new T1 hypointense            (2.0)      (1.0)***          (4.0)      (1.0)***          (2.0)** lesions over 2 years
Lesion mean ratio                 0.28                         0.43              0.59 (95% CI)                          (0.20, 0.39)                 (0.30, 0.61)      (0.42, 0.82) a                                                         b
All analyses of clinical endpoints were intent-to-treat; MRI analysis used MRI cohort *P-value < 0.05; **P-value < 0.01; ***P-value < 0.0001; #not statistically significant 

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).

Paediatric population
13
Tecfidera was evaluated in a prospective open-label, uncontrolled study in 22 paediatric patients with RRMS aged 13 to 17 years (4 patients aged ≤14 years). Subjects received Tecfidera 120 mg twice a day for 7 days followed by 240 mg twice a day for 24 weeks. The median number of new or newly enlarging T2 hyperintense lesions changed from 2 in the 8 week pre-treatment evaluation period to 0 in the final 8 weeks of the treatment period (median change -2, n=16). Patients subsequently entered an extension study for a further 96 weeks. Among the 10 patients with MRI data between weeks 64 and week 72 of the extension study, the median number of subjects with new or newly enlarging T2 hyperintense lesions was 0 (range 0,2). Over the full treatment period (120-week), ARR was 0.2 representing an 84.5% relative reduction in relapses (n=20; 95% CI [66.8, 92.8], p<0.0001), when compared to the year prior to treatment initiation. These data should be considered cautiously regarding limitations of the study design (no control arm, pre- versus post-dose comparison) (see section 4.2)

Pharmacokinetic Properties

5.2   Pharmacokinetic properties

Orally administered 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.

Absorption

The Tmax 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 area under the curve (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 section 4.2).

Distribution

The apparent volume of distribution following oral administration of 240 mg dimethyl fumarate varies between 60 L and 90 L. Human plasma protein binding of monomethyl fumarate generally ranges between 27% and 40%.

Biotransformation

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 14C-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.

Elimination
14
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.
Linearity

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 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.

Paediatric population
The pharmacokinetic profile of 240 mg dimethyl fumarate twice a day was evaluated in a small, open- label, uncontrolled study in patients with RRMS aged 13 to 17 years (n=21). The pharmacokinetics of Tecfidera in these adolescent patients was consistent with that previously observed in adult patients (Cmax: 2.00±1.29 mg/l; AUC0-12hr: 3.62±1.16 h.mg/l, which corresponds to an overall daily AUC of 7.24 h.mg/l).

Renal impairment
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.

Hepatic impairment
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.