BACKGROUND: Diroximel fumarate (DRF) is a novel oral fumarate approved in the USA for relapsing forms of multiple sclerosis. DRF is converted to monomethyl fumarate, the pharmacologically active metabolite of dimethyl fumarate (DMF). DRF 462 mg and DMF 240 mg produce bioequivalent exposure of monomethyl fumarate and are therefore expected to have similar efficacy/safety profiles; the distinct chemical structure of DRF may contribute to its tolerability profile.

OBJECTIVES: The objective of this study was to compare the gastrointestinal tolerability of DRF and DMF over 5 weeks in patients with relapsing-remitting multiple sclerosis.

METHODS: EVOLVE-MS-2 was a phase III, randomized, double-blind, head-to-head, 5-week study evaluating the gastrointestinal tolerability of DRF 462 mg vs DMF 240 mg, administered twice daily in patients with relapsing-remitting multiple sclerosis, using two self-administered gastrointestinal symptom scales: Individual Gastrointestinal Symptom and Impact Scale (IGISIS) and Global Gastrointestinal Symptom and Impact Scale (GGISIS). The primary endpoint was the number of days with an IGISIS intensity score ≥ 2 relative to exposure. Other endpoints included the degree of gastrointestinal symptom severity measured by IGISIS/GGISIS and assessment of safety/tolerability.

RESULTS: DRF-treated patients experienced a statistically significant reduction (46%) in the number of days with an IGISIS symptom intensity score ≥ 2 compared with DMF-treated patients (rate ratio [95% confidence interval]: 0.54 [0.39-0.75]; p = 0.0003). Lower rates of gastrointestinal adverse events (including diarrhea, nausea, vomiting, and abdominal pain) were observed with DRF than DMF (34.8% vs 49.0%). Fewer patients discontinued DRF than DMF because of adverse events (1.6% vs 5.6%) and gastrointestinal adverse events (0.8% vs 4.8%).

CONCLUSIONS: DRF demonstrated an improved gastrointestinal tolerability profile compared with DMF, with less severe gastrointestinal events and fewer days of self-assessed gastrointestinal symptoms, fewer gastrointestinal adverse events, and lower discontinuation rates because of gastrointestinal adverse events.

CLINICAL TRIALS REGISTRATION: ClinicalTrials.gov (NCT03093324).