Dimethyl fumarate in the treatment of multiple sclerosis: real-world effectiveness in a Turkish cohort

Background Dimethyl fumarate (DMF) is approved as a first-line treatment in relapsing-remitting multiple sclerosis (RRMS). Aim To evaluate the demographic, clinical, and radiological outcomes of DMF treatment in a real-world setting. Study design Multicenter retrospective study based on data from 61 clinics across Türkiye. Methods Side effects, leukocyte and lymphocyte counts, liver enzymes, EDSS (Expanded Disability Status Scale), and upper- and lower-extremity test results were evaluated in patients with RRMS before DMF initiation and at 1, 6, 12, and 24 months. Additionally, NEDA-3 (No Evidence of Disease Activity-3) status was assessed at the 1 and 2-year follow-ups. Results 1,749 patients participated in this retrospective study. The most common side effects were flushing and gastrointestinal symptoms, which were more frequent in women and in patients with lower weight and lower Body Mass Index (BMI). Leukocyte and lymphocyte counts initially decreased and then stabilized, whereas transient elevations in liver enzymes resolved during follow-up. EDSS scores showed a significant improvement beginning at the 6-month follow-up. Performance on the Nine-Hole Peg Test (9HPT) improved, whereas no significant change was observed in the Timed 25-Foot Walk (T25FW). In addition, approximately 70% of the patients achieved NEDA-3 status at both the 1 and 2-year follow-ups. Conclusion DMF demonstrated a favorable safety profile and was associated with significant improvements in EDSS while maintaining NEDA-3 status in approximately 70% of patients with RRMS. Adverse events occurred more frequently among women and among patients with lower body weight and lower BMI.