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INTRODUCTION: In EVOLVE-MS-1 (NCT02634307), mean absolute lymphocyte count (ALC) on diroximel fumarate (DRF) declined from baseline by approximately 28% in year 1, then stabilized, similar to ALC decline observed with dimethyl fumarate (DMF). Prior studies reported that clinical efficacy of DMF was not substantially different in patients with and without lymphopenia. METHODS: EVOLVE-MS-1-an open-label, 96-week, phase 3 study-assessed DRF safety and exploratory efficacy in patients with relapsing-remitting multiple sclerosis. This study analyzes efficacy-related outcomes comparing (1) patients with lymphopenia (≥ 1 ALC below lower limit of normal [LLN]) and without (all ALCs ≥ LLN); (2) across quartiles stratified by week 96 ALC decline from baseline: Q1 (≥ 47% decline); Q2 (30% to < 47% decline); Q3 (12% to < 30% decline); Q4 (< 12% decline). RESULTS: Baseline characteristics were similar between patients without (n = 593) and with lymphopenia (n = 452). At week 96, adjusted annualized relapse rate (ARR; 95% confidence interval) was 0.14 (0.11-0.17) without lymphopenia and 0.12 (0.09-0.15) with lymphopenia. Estimated proportions with 12-week confirmed disability progression (CDP12) at week 96 were 10.2% without and 9.3% with lymphopenia. When stratified by quartiles (Q1-Q4), ARR at week 96 was 0.11 (Q1), 0.09 (Q2), 0.13 (Q3), and 0.17 (Q4). Estimated proportions with CDP12 at week 96 were 9.6% (Q1), 10.2% (Q2), 5.7% (Q3), and 10.9% (Q4). At week 96, no evidence of disease activity was achieved by 47.2% (Q1), 47.8% (Q2), 45.4% (Q3), and 37.3% (Q4) of patients. CONCLUSION: In DRF-treated patients in EVOLVE-MS-1, clinical and radiological measurements indicated reduced disease activity regardless of lymphopenia or magnitude of ALC decline from baseline; however, patients who had greater ALC declines appeared to have numerically lower ARR and higher proportions free from relapses and gadolinium-enhancing lesions compared with those with smallest decline. This supports prior evidence that, while lymphopenia may contribute to fumarate efficacy outcomes, it is not the primary mechanism of action. TRIAL REGISTRATION: ClinicalTrials.gov identifier NCT02634307.
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People with multiple sclerosis (pwMS) have an increased risk of infection. As disease-modifying therapies (DMTs) and other treatments may interact with the immune system, there may be concerns about vaccine efficacy and safety. Therefore, it is important to evaluate possible interactions between DMTs and vaccines. The fumarates, dimethyl fumarate, diroximel fumarate, and monomethyl fumarate, are approved for the treatment of relapsing multiple sclerosis. This review assesses the evidence on vaccine response in pwMS treated with fumarates, with a particular focus on COVID-19 vaccines. Treatment with fumarates does not appear to result in blunting of humoral responses to vaccination; for COVID-19 vaccines, particularly RNA-based vaccines, evidence indicates antibody responses similar to those of healthy recipients. While data on the effect of fumarates on T-cell responses are limited, they do not indicate any significant blunting. COVID-19 vaccines impart a similar degree of protection against severe COVID-19 infection for pwMS on fumarates as in the general population. Adverse reactions following vaccination are generally consistent with those observed in the wider population; no additional safety signals have emerged in those on fumarates. Additionally, no increase in relapse has been observed in pwMS following vaccination. In pwMS receiving fumarates, vaccination is generally safe and elicits protective immune responses.
