Real-World Safety and Effectiveness of Dimethyl Fumarate in Black or African American Patients with Multiple Sclerosis: 3-Year Results from ESTEEM

Introduction: Black or African American (black/AA) patients with multiple sclerosis (MS) are reported to exhibit greater disease severity compared with non-black or non-AA patients. Whether differences exist in response to MS disease-modifying therapies remains uncertain, as MS clinical trials have included low numbers of non-white patients. We evaluated real-world safety and effectiveness of dimethyl fumarate (DMF) on MS disease activity in black/AA patients. Methods: ESTEEM is an ongoing, 5-year, multinational, prospective study evaluating long-term safety and effectiveness of DMF in patients with MS. This interim analysis included patients newly prescribed DMF in routine practice at 394 sites globally. Results: Overall, 4897 non-black/non-AA and 187 black/AA patients were analyzed; median (range) follow-up 18 (2–37) months. Unadjusted annualized relapse rates (ARRs) for 12 months before DMF initiation versus 36 months post DMF initiation, respectively, were: non-black/non-AA patients, 0.83 (95% CI 0.80–0.85) versus 0.10 (95% CI 0.09–0.10), 88% lower ARR (P < 0.0001); black/AA patients, 0.68 (95% CI 0.58–0.80) versus 0.07 (95% CI 0.05–0.10), 90% lower ARR (P < 0.0001). In total, 35 (19%) black/AA patients reported adverse events leading to treatment discontinuation; gastrointestinal disorders were most common (7%), consistent with non-black/non-AA patients (8%). Median lymphocyte counts decreased by 22% in the first year (vs 36% in non-black/non-AA patients), then remained stable and above lower limit of normal in most patients. Conclusions: Relapse rates remained low in black/AA patients, consistent with non-black/non-AA patients. The safety profile of DMF in black/AA patients was consistent with that in the non-black/non-AA ESTEEM population, although lymphocyte decrease was less pronounced in black/AA patients.