The effect of dimethyl fumarate (Tecfidera™) on lymphocyte counts: A potential contributor to progressive multifocal leukoencephalopathy risk

Dimethyl fumarate (Tecfidera (TM)) is an effective therapy for relapsing forms of multiple sclerosis (MS). Our study suggests that this drug may have immunosuppressive properties evidenced by significant sustained reduction in CD8 lymphocyte counts and, to a lesser extent, CD4 lymphocyte counts. This observation is relevant in light of the recent case of progressive multifocal leukoencephalopathy in a patient receiving this drug. (C) 2015 Published by Elsevier B.V.