Lessons learned after 20 years of real-world experience with natalizumab.

Background: While natalizumab (NTZ) is an effective therapy for multiple sclerosis (MS), it is associated with an increased risk of progressive multifocal leukoencephalopathy (PML). After 20 years (2002-2022) of experience with NTZ at our center, we observed no cases of PML.

Objectives: We evaluated the likelihood of experiencing PML in a subset of our treatment cohort, as well as reviewed treatment practices at our center that may mitigate PML risk.

Delayed lymphocyte re-population following discontinuation of dimethyl fumarate and after switching to other disease modifying drug therapies.

Background: Dimethyl fumarate (DMF) reduces absolute lymphocyte counts, CD4, and CD8 counts, without significantly affecting total white blood cell counts. However, the recovery rate of these cells after discontinuation of DMF is unknown. The effect of subsequent disease modifying therapies (DMTs) on re-population rate is also unknown.

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

Dimethyl fumarate (Tecfidera™) 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.