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

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.