Background: Dimethyl fumarate (DMF) is an oral therapy for relapsing-remitting multiple sclerosis (RRMS). DMF is included in the Swedish post-market surveillance study “Immunomodulation and Multiple Sclerosis Epidemiology” (IMSE).
Objectives: To assess the effectiveness and safety of DMF with focus on patients treated at least 36 months in the IMSE study.
Methods: Descriptive data of Extended Disability Status Scale (EDSS), Multiple Sclerosis Severity Scale (MSSS), Symbol Digit Modalities Test (SDMT), Multiple Sclerosis Impact Scale (MSIS-29), European Quality of Life - 5 Dimensions Test (EQ-5D), Visual Analog Scale (VAS) and Adverse Events (AEs) is obtained from the nationwide Swedish Neuro Registry (NeuroReg). Effectiveness measures were assessed using the Wilcoxon Signed Rank Test and drug survival using the Kaplan-Meier curve.
Results: 2349 DMF-treated patients were included between March 2014 and June 2020 with an overall drug survival rate of 45%. The main reasons for discontinuation were AEs (50%) and lack of effect (30%). 186 AEs were reported to the Swedish Medical Products Agency, of which 59 were serious. A total of 8 patients have died during DMF treatment or within 6 months of treatment discontinuation.
36 month cohort: 940 patients had continuous treatment for at least 36 months. This cohort had a mean age of 42 years and a mean treatment duration of 56 months. The majority (50%) had switched from interferon or glatiramer acetate, and (24%) were treatment naïve (TN).
Significant improvements in mean values at 36 months of treatment compared to baseline for the 36-month cohort were noted for MSSS, SDMT, MSIS-29 Psychological, EQ-5D and VAS. When TN patients were solely assessed (n=230) improvements were noted for all above mentioned measures as well as MSIS-29 Psychological. The remaining patients in the cohort; treatment experienced patients (n=710) displayed significant improvements only for MSSS, MSIS-29 Psychological and EQ-5D. TN patients had a mean duration from diagnosis to treatment start of 5 months compared to 91 months for the remaining cohort. TN were also younger than the remaining cohort (37 years vs 43 years).
Conclusions: DMF demonstrates clinical improvements in patients treated 36 months, more pronounced in TN patients. However; due to the high discontinuation rate there is an unavoidable selection bias. Continued follow up is needed to assess the effectiveness and safety of DMF over longer time periods in a real world setting.