Dimethyl fumarate treatment does not seem to have any effect in patients with primary progressive multiple sclerosis (PPMS), according to a new study published in the journal Multiple Sclerosis and Related Disorders. However, the disease of some patients improved following 96 weeks of treatment.

“This finding is very interesting and warrants further investigation,” the study authors said.

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A previous study by the same authors had shown that treatment with dimethyl fumarate for 48 weeks did not reduce the concentration of neurofilament light chain in the cerebrospinal fluid of patients with PPMS.

Here, the authors reported results from the open-label extension phase of the study where all patients received dimethyl fumarate for another 48 weeks (from week 48 to week 96).

A total of 33 patients completed the second 48-week period of the study. The researchers did not find any differences in clinical and magnetic resonance imaging (MRI) measures between patients who were treated with dimethyl fumarate for the whole 96 weeks and those who received a placebo for the first 48 weeks and then moved to dimethyl fumarate treatment.

The concentration of neurofilament light chain remained stable in the serum of all patients over the 96 weeks.

The disease progressed in 14 patients over the 96-week period as assessed by the Expanded Disability Status Scale (EDSS), Timed 25-Foot Walk test, and 9-Hole Peg Test. Interestingly, the same tests showed that 15 patients improved in the same time period. 

When they analyzed the results of the Symbol Digit Modalities Test and a cut-off of 8 points, the researchers found that the disease of 2 patients worsened, while that of 25 patients remained the same, and that of 5 patients improved.

“The reasons for the physical improvement in an unexpectedly high proportion of patients must be addressed in future studies,” they concluded. 

Reference

Højsgaard Chow H, Talbot J, Lundell H, et al. Dimethyl fumarate treatment of primary progressive multiple sclerosis: results of an open-label extension study. Mult Scler Relat Disord. Published online December 9, 2022. doi:10.1016/j.msard.2022.104458