Safety, tolerability, and efficacy of diroximel fumarate in a cohort of Black patients with multiple sclerosis from the phase 3 EVOLVE-MS-1 study

Abstract

Background: Multiple sclerosis (MS) has not been well studied in racial and ethnic minorities, as these populations are typically underrepresented in clinical trials. Black or African Americans comprise ∼13 % of the US population, yet are represented by as little as 5 % in clinical trials. Differences in disease course and progression have been reported between races and ethnicities, so there is a need to understand the safety and efficacy of disease-modifying therapies (DMTs) in Black patients, to inform evidence-based approaches to treatment in this population.

Methods: EVOLVE-MS-1 (NCT0234307) was an open-label, single-arm, phase 3 study assessing the long-term safety, tolerability, and efficacy of diroximel fumarate (DRF) over 96 weeks in adults with relapsing-remitting multiple sclerosis (RRMS). Patients were either newly initiated to DRF or rolled over from completing EVOLVE-MS-2 (NCT03093324). In this post-hoc analysis of the phase 3 EVOLVE-MS-1 study, we evaluate the safety and exploratory efficacy outcomes for DRF in Black and non-Black patient subgroups.

Results: Of 1057 patients enrolled, 72 (6.8 %) were Black. In Black vs non-Black patients, mean age was 42 vs 43 years and 75 % vs 72 % were female, respectively. In both groups, median (range) duration of DRF exposure was 1.8 (0.0-2.0) years and mean Expanded Disability Status Scale (EDSS) was 2.7. The most common prior DMTs for both Black vs non-Black patients were interferons (47 % vs 37 %) and glatiramer acetate (36 % vs 24 %). DRF treatment was discontinued in 33 (46 %) Black and 224 (23 %) non-Black patients; most common reasons for discontinuation were withdrawal by patient (n = 11, 15.3 %), adverse events (AEs; n = 7, 9.7 %), and lost to follow-up (n = 7, 9.7 %) in Black patients; AEs (8.2 %) and withdrawal by patient (7.0 %) in non-Black patients. AEs were reported in 90 % Black and 89 % non-Black patients; most AEs were mild or moderate in both groups. Gastrointestinal (GI) AEs were reported in 36 % Black and 32 % non-Black patients; no Black patients discontinued due to GI AEs, vs 7 (0.7 %) non-Black patients. The most commonly reported AE was flushing (18 % Black and 28 % non-Black patients). No AEs of lymphopenia were reported in Black patients compared with 13 % of non-Black patients. Mean absolute lymphocyte count declined from baseline to week 48 by 15 % in Black patients and 29 % in non-Black patients, then plateaued and remained above the lower limit of normal (LLN; 0.91 × 10⁹/L). Adjusted annualized relapse rate (95 % confidence interval) was reduced by 78.2 % (54.6 - 89.5; p < 0.0001) in Black patients, from 12 months before to 96 weeks after DRF treatment; similar to 81.7 % (78.5 - 84.5 %; p < 0.0001) reduction in non-Black patients. Mean number of patients free from confirmed disability progression was 93.4 % by week 48, then 86.2 % vs 90.4 % by week 96 in Black vs non-Black patients, respectively.

Conclusion: This study presents the first analysis of safety and efficacy of DRF in Black patients. Relapse rates remained low in Black patients on DRF, consistent with non-Black patients, and there were no new safety signals identified in the Black patient subgroup in EVOLVE-MS-1. Together, these outcomes support DRF as an effective treatment option in Black patients with RRMS.

Keywords: Diroximel fumarate; Minority populations; Multiple sclerosis; Safety and effectiveness.