Discontinuation and comparative effectiveness of dimethyl fumarate and fingolimod in 2 centers.

Background: Dimethyl fumarate (DMF) and fingolimod (FTY) are approved oral disease-modifying therapies for relapsing multiple sclerosis (MS). Observational studies are valuable when randomized clinical trials cannot be done due to ethical or practical reasons. Two-site studies allow investigators to further ascertain external validity of previously examined treatment effect differences.