A Cochrane review «Dimethyl fumarate for multiple sclerosis»1 «Xu Z, Zhang F, Sun F et al. Dimethyl fumarate for ...»1 included 2 studies with a total of 2667 subjects with relapsing remitting multiple sclerosis. The two dosages of dimethyl fumarate (DMF, 240 mg orally 3 times or twice daily) were compared with placebo for 2 years. Here are shown only the results for twice-daily dosing as it is the final dosing of the product. Among the patients a subsample of 1221 (45.8%) patients was selected to participate in MRI evaluations. Meta-analyses showed that DMF reduced the number of patients with a relapse (0.64, 95% CI 0.54 to 0.77, p < 0.00001; 2 studies, n=1540) or disability worsening (0.65, 95% CI 0.53 to 0.81, p = 0.0001, 2 studies, n=1539) over 2 years compared to placebo. However, the follow-up for disability worsening was too short for clinically meaningful conclusions. DMF also reduced the annualised relapse rate (ARR). Data of active lesions on MRI scans were not combined because there was a high risk of selection bias for MRI outcomes and imprecision of MRI data in both studies. For patients on DMF the RR was 2.18 (1.56 to 3.06; 2 studies, n=1540) to discontinue the study drug because of adverse events (excluding relapses) during 2 years. The most common adverse events (AE) included flushing and gastrointestinal events (upper abdominal pain, nausea and diarrhoea). Uncommon AEs included lymphopenia and leukopenia, which were more likely to happen with DMF than with placebo (RR 5.69, 95% CI 2.40 to 13.46, p < 0.0001 and 6.53, 95% CI 3.13 to 13.64, p < 0.00001, respectively).
The drop out rate was quite high in both trials (more than 20% in both trials) and reasons for dropouts were unbalanced among groups.