Of 618 patients with follow-up for ≥10 years, 192 were continuously treated BID (192/501, 38% of the overall continuously treated BID population). Mean (SD) age 41.6 (8.7) years; 68% female. Fifty-one percent (98/192) of patients remained relapse-free; 73% (141/192) had ≤1 relapse; ARR over Year 0–10: 0.107 (rate ratio vs.10-year placebo/DMF 0.603 [p=0.018]). Median time to first relapse was 518 weeks. At baseline, mean (SD) expanded disability status scale (EDSS) score was 2.24 (1.18). Patients with EDSS ≤3.5: 164/184 (89%) Year 2, 148/184 (80%) Year 8, 146/184 (79%) Year 10. Over 10 years, 64% (122/191) of patients had no CDP. Overall, 77 (40%) patients experienced SAEs; most were MS relapse (18%, 34/192) or infections (6%; 12/192). Over 10 years, there was no increased incidence of serious infection. Patients remained stable on SF-36 and EQ-5D from baseline to Year 10.

Patients continuously treated with DMF BID for ≥10 years had a low incidence of relapses. The proportion of patients with EDSS ≤3.5 remained stable over time, the number of patients with CDP over 10 years remained low, and PROs remained stable. There was no increased incidence of serious infections over time. These results support the safety and efficacy of DMF as a long-term treatment option for patients with RRMS.

Support: Biogen