Pharmacotherapeutic group: Immunosuppressants, other immunosuppressants. ATC code: L04AX09
Mechanism of action
The mechanism by which diroximel fumarate exerts therapeutic effects in MS is not fully understood. Diroximel fumarate acts via the major active metabolite, monomethyl fumarate. Preclinical studies indicate that the pharmacodynamic responses of monomethyl fumarate appears to be mediated, at least in part, 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.
Pharmacodynamic effects
Effects on Immune System
In clinical studies, dimethyl fumarate demonstrated anti-inflammatory and immunomodulatory properties. Dimethyl fumarate and monomethyl fumarate (the active metabolite of diroximel fumarate and dimethyl fumarate) significantly reduce immune cell activation and subsequent release of pro‑inflammatory cytokines in response to inflammatory stimuli and moreover affect lymphocyte phenotypes through a down-regulation of pro-inflammatory cytokine profiles (TH1, TH17) and biased towards anti-inflammatory production (TH2). In phase 3 studies in MS patients (DEFINE, CONFIRM and ENDORSE), upon treatment with dimethyl fumarate mean lymphocyte counts decreased on average by approximately 30% of their baseline value over the first year with a subsequent plateau. In these studies, patients who discontinued dimethyl fumarate therapy with lymphocyte counts below the lower limit of normal (LLN, 910 cells/mm3) were monitored for recovery of lymphocyte counts to the LLN.
Figure 1 shows the proportion of patients estimated to reach the LLN based on the Kaplan-Meier method without prolonged severe lymphopenia. The recovery baseline (RBL) was defined as the last on-treatment ALC prior to dimethyl fumarate discontinuation. The estimated proportion of patients recovering to LLN (ALC ≥ 0.9 x 109/L) at Week 12 and Week 24, who had mild, moderate, or severe lymphopenia at RBL are presented in Table 2, Table 3, and Table 4 with 95% pointwise confidence intervals. The standard error of the Kaplan-Meier estimator of the survival function is computed using Greenwood's formula.
Figure 1: Kaplan-Meier Method; Proportion of Patients with Recovery to ≥ 910 cells/mm3 LLN from the Recovery Baseline (RBL)
Table 2: Kaplan-Meier Method; Proportion of patients estimated to reach LLN, mild lymphopenia at the recovery baseline (RBL), excluding patients with prolonged severe lymphopenia
| Number of patients with mild lymphopeniaa at risk | Baseline N=86 | Week 12 N=12 | Week 24 N=4 |
| Proportion reaching LLN (95% CI) | | 0.81 (0.71, 0.89) | 0.90 (0.81, 0.96) |
a Patients with ALC < 910 and ≥ 800 cells/mm3 at RBL, excluding patients with prolonged severe lymphopenia.
Table 3: Kaplan-Meier Method; Proportion of patients estimated to reach LLN, moderate lymphopenia at the recovery baseline (RBL), excluding patients with prolonged severe lymphopenia
| Number of patients with moderate lymphopeniaa at risk | Baseline N=124 | Week 12 N=33 | Week 24 N=17 |
| Proportion reaching LLN (95% CI) | | 0.57 (0.46, 0.67) | 0.70 (0.60, 0.80) |
a Patients with ALC < 800 and ≥ 500 cells/mm3 at RBL, excluding patients with prolonged severe lymphopenia.
Table 4: Kaplan-Meier Method; Proportion of patients estimated to reach LLN, severe lymphopenia at the recovery baseline (RBL), excluding patients with prolonged severe lymphopenia
| Number of patients with severe lymphopeniaa at risk | Baseline N=18 | Week 12 N=6 | Week 24 N=4 |
| Proportion reaching LLN (95% CI) | | 0.43 (0.20, 0.75) | 0.62 (0.35, 0.88) |
a Patients with ALC < 500 cells/mm3 at RBL, excluding patients with prolonged severe lymphopenia.
Clinical efficacy and safety
Diroximel fumarate and dimethyl fumarate are rapidly metabolised by esterases before they reach the systemic circulation to the same active metabolite, monomethyl fumarate, upon oral administration. The PK comparability of diroximel fumarate to dimethyl fumarate through the analysis of monomethyl fumarate exposure has been demonstrated (see section 5.2), thus efficacy profiles are expected to be similar.
Clinical studies with dimethyl fumarate
Two, 2-year, randomised, double-blind, placebo-controlled studies (DEFINE with 1,234 patients and CONFIRM with 1,417 patients) of patients with RRMS were performed. Patients with progressive forms of MS were not included in these studies.
Efficacy (see table below) and safety were demonstrated in patients 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 CONFIRM contained a rater-blinded (i.e. study physician/ investigator assessing the response to study treatment was blinded) reference comparator of glatiramer acetate.
In DEFINE, patients had the following median baseline characteristics: age 39 years, disease duration 7 years, EDSS score 2. 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 CONFIRM, patients had the following median baseline characteristics: age 37 years, disease duration 6 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, patients treated with dimethyl fumarate had a clinically meaningful and statistically significant reduction on the primary endpoint in study DEFINE, proportion of patients relapsed at 2 years; and the primary endpoint in study CONFIRM, annualised relapse rate (ARR) at 2 years.
The ARR for glatiramer acetate and placebo was 0.286 and 0.401 respectively in study CONFIRM, corresponding to a reduction of 29% (p=0.013).
| | DEFINE | CONFIRM |
| | Placebo | dimethyl fumarate 240 mg twice a day | Placebo | dimethyl fumarate 240 mg twice a day | Glatiramer acetate |
| Clinical Endpointsa | | | | | |
| No. patients | 408 | 410 | 363 | 359 | 350 |
| Annualised relapse rate | 0.364 | 0.172*** | 0.401 | 0.224*** | 0.286* |
| Rate ratio (95% CI) | | 0.47 (0.37, 0.61) | | 0.56 (0.42, 0.74) | 0.71 (0.55, 0.93) |
| Proportion relapsed | 0.461 | 0.270*** | 0.410 | 0.291** | 0.321** |
| Hazard ratio (95% CI) | | 0.51 (0.40, 0.66) | | 0.66 (0.51, 0.86) | 0.71 (0.55, 0.92) |
| Proportion with 12-week confirmed disability progression | 0.271 | 0.164** | 0.169 | 0.128# | 0.156# |
| Hazard ratio (95% CI) | | 0.62 (0.44, 0.87) | | 0.79 (0.52, 1.19) | 0.93 (0.63, 1.37) |
| Proportion with 24 week confirmed disability progression | 0.169 | 0.128# | 0.125 | 0.078# | 0.108# |
| Hazard ratio (95% CI) | | 0.77 (0.52, 1.14) | | 0.62 (0.37, 1.03) | 0.87 (0.55, 1.38) |
| MRI Endpointsb | | | | | |
| No. patients | 165 | 152 | 144 | 147 | 161 |
| Mean (median) number of new or newly enlarging T2 lesions over 2 years | 16.5 (7.0) | 3.2 (1.0)*** | 19.9 (11.0) | 5.7 (2.0)*** | 9.6 (3.0)*** |
| Lesion mean ratio (95% CI) | | 0.15 (0.10, 0.23) | | 0.29 (0.21, 0.41) | 0.46 (0.33, 0.63) |
| Mean (median) number of Gd lesions at 2 years | 1.8 (0) | 0.1 (0)*** | 2.0 (0.0) | 0.5 (0.0)*** | 0.7 (0.0)** |
| Odds ratio (95% CI) | | 0.10 (0.05, 0.22) | | 0.26 (0.15, 0.46) | 0.39 (0.24, 0.65) |
| Mean (median) number of new T1 hypointense lesions over 2 years | 5.7 (2.0) | 2.0 (1.0)*** | 8.1 (4.0) | 3.8 (1.0)*** | 4.5 (2.0)** |
| Lesion mean ratio (95% CI) | | 0.28 (0.20, 0.39) | | 0.43 (0.30, 0.61) | 0.59 (0.42, 0.82) |
aAll analyses of clinical endpoints were intent-to-treat; bMRI analysis used MRI cohort
*P-value < 0.05; **P-value < 0.01; ***P-value < 0.0001; #not statistically significant
An open non-controlled 8-year extension study (ENDORSE) enrolled 1,736 eligible RRMS patients from the pivotal studies (DEFINE and CONFIRM). The primary objective of the study was to assess the long-term safety of dimethyl fumarate in patients with RRMS. Of the 1,736 patients, approximately half (909, 52%) were treated for 6 years or longer. 501 patients were continuously treated with dimethyl fumarate 240 mg twice daily across all 3 studies and 249 patients who were previously treated with placebo in studies DEFINE and CONFIRM received treatment 240 mg twice daily in study ENDORSE. Patients who received treatment twice daily continuously were treated for up to 12 years.
During study ENDORSE, more than half of all patients treated with dimethyl fumarate 240 mg twice daily did not have a relapse. For patients continuously treated twice daily across all 3 studies, the adjusted ARR was 0.187 (95% CI: 0.156, 0.224) in studies DEFINE and CONFIRM and 0.141 (95% CI: 0.119, 0.167) in study ENDORSE. For patients previously treated with placebo, the adjusted ARR decreased from 0.330 (95% CI: 0.266, 0.408) in studies DEFINE and CONFIRM to 0.149 (95% CI: 0.116, 0.190) in study ENDORSE.
In study ENDORSE, the majority of patients (> 75%) did not have confirmed disability progression (measured as 6-month sustained disability progression). Pooled results from the three studies demonstrated dimethyl fumarate treated patients had consistent and low rates of confirmed disability progression with slight increase in mean EDSS scores across ENDORSE. MRI assessments (up to year 6, including 752 patients who had previously been included in the MRI cohort of studies DEFINE and CONFIRM showed that the majority of patients (approximately 90%) had no Gd-enhancing lesions. Over the 6 years, the annual adjusted mean number of new or newly enlarging T2 and new T1 lesions remained low.
Efficacy in patients with high disease activity:
In Studies DEFINE and CONFIRM, 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).
Clinical studies with Vumerity
The gastrointestinal tolerability of diroximel fumarate was evaluated in a randomised, multi-centre, phase 3 study (EVOLVE-MS-2) in 504 adult patients with RRMS. The study included a 5-week, double-blind treatment period with two treatment arms. Patients had a 1-week titration period and were randomised (1:1) to receive diroximel fumarate 462mg twice daily (n=253) or dimethyl fumarate 240 mg twice daily (n=251). Patients had the following median baseline characteristics: age 44 years, disease duration 6 years and EDSS score 2.5. In this study, GI tolerability was investigated using the Individual GI Symptom and Impact Scale (IGISIS), which evaluated the incidence, intensity, onset, duration, and functional impact of five individual GI symptoms: nausea, vomiting, upper abdominal pain, lower abdominal pain, and diarrhoea.
Overall gastrointestinal adverse reactions were observed in 34.8% of diroximel fumarate‑treated patients and in 49.0% of dimethyl fumarate-treated patients. Treatment discontinuations were in total 1.6% and 6.0%, for diroximel fumarate and dimethyl fumarate, respectively. The discontinuations for gastrointestinal tolerability reasons were 0.8% and 4.8%, for diroximel fumarate and dimethyl fumarate, respectively. Treatment‑emergent gastrointestinal adverse reactions of ≥ 5% for diroximel fumarate and dimethyl fumarate, respectively, were diarrhoea (15.4% and 22.3%), nausea (14.6% and 20.7%), upper abdominal pain (6.7% and 15.5%), abdominal pain (6.3% and 9.6%), lower abdominal pain (5.9% and 6.8%), and vomiting (3.6% and 8.8%).
Paediatric population
The efficacy of Vumerity in paediatric patients has not been established.
The Medicines and Healthcare products Agency have waived the obligation to submit the results of studies with Vumerity in all subsets of the paediatric population in the treatment of MS (see section 4.2 for information on paediatric use).