A phase 3 clinical trial tested the safety and efficacy of teriflunomide, an oral immunomodulatory drug, in children with multiple sclerosis. Although the medication did not prevent disease relapses to a greater extent than placebo, the option for some patients to switch from placebo to teriflunomide before the end of the trial likely biased the results against treatment efficacy. The drug appeared to reduce the number of new or enlarged lesions that are detected through MRI.