Safety and efficacy of delayed-release dimethyl fumarate in patients with relapsing-remitting multiple sclerosis: 9 years' follow-up of DEFINE, CONFIRM, and ENDORSE

Introduction: We report safety and efficacy in patients treated with dimethyl fumarate (DMF) for ~9 years in ENDORSE. Lymphocyte analysis data are also reported.

Methods: Incidence of serious adverse events (SAEs), discontinuations due to adverse events (AEs), annualized relapse rate (ARR) and Expanded Disability Status Scale (EDSS) score were assessed. Patients were treated with DMF 240 mg twice daily (BID): placebo (PBO)/DMF (PBO for years 0-2 /DMF for years 3-9) or continuous (DMF/DMF) treatment; newly diagnosed patients were included. Annual magnetic resonance imaging (MRI) was evaluated in patients from the MRI cohort of DEFINE/CONFIRM. For the lymphocyte analysis, data from first DMF exposure were analyzed.

Results: Of 2079 DEFINE/CONFIRM completers, 1736 enrolled and received ⩾1 dose of DMF. The MRI cohort included 530 patients. In the overall population, 527 (30%) patients experienced SAEs; most were fall and urinary tract infection. Over 9 years on DMF treatment, adjusted ARR remained low (⩽0.20). In patients treated with PBO in years 0-2, decreased ARR was apparent as early as year 3. Of DMF/DMF and PBO/DMF patients, 73% and 74%, respectively, had no 24-week confirmed disability progression. Most patients (~70%) had no new T1 or new/newly enlarging T2 lesions compared with previous MRI scans after 7 years treatment with DMF; the annual number of new T1 hypointense lesions and new/newly enlarging T2 hyperintense lesions were 0.6-0.8 and 0.9-2.0, respectively. Mean percentage brain volume change from ENDORSE baseline (6 years treatment in ENDORSE) was -1.32% (range -1.60% to -1.05%). Of the 2513 patients with lymphocyte assessments, 2470 had ⩾1 post-baseline measurement, 53 developed severe prolonged lymphopenia and were followed for up to 11 years; incidence of serious infection was not higher than in patients with absolute lymphocyte count (ALC) always ⩾ lower limit of normal (LLN). In patients with lymphopenia while on DMF and ALC < 0.91 × 10⁹/L at discontinuation (n = 138), median time to ALC ⩾ LLN was 7 weeks post-discontinuation.

Conclusions: Sustained safety and efficacy of DMF was observed in patients continuing on treatment for up to 11 years, supporting DMF as a long-term treatment option for patients with RRMS.

Trial registration: ClinicalTrials.gov identifiers, NCT00835770 (ENDORSE); NCT00420212 (DEFINE); NCT00451451 (CONFIRM).