Purpose: Dimethyl fumarate (DMF) has been approved by the U.S. Food and Drug Administration (FDA) for the treatment of relapsing-remitting multiple sclerosis (RRMS), a demyelinating autoimmune disease characterized by acute episodes of motor, sensory, and cognitive symptoms. Optic neuritis is an episodic sequela experienced by some patients with RRMS that typically presents as acute, monocular vision loss. Episodes of optic neuritis damage and kill retinal ganglion cells (RGCs), and can culminate in permanent vision loss. The purpose of these studies was to evaluate the capacity of DMF to mitigate optic neuritis. The work presented combines studies of a mouse model of MS and a retrospective chart analysis of files of patients with RRMS treated at the MS Center of Excellence within the Oklahoma Medical Research Foundation.
Methods: Experimental autoimmune encephalomyelitis (EAE) is a well-established mouse model that recapitulates cardinal features of somatic and visual MS pathologies. EAE was induced in female C57BL/6J mice by inoculation with myelin oligodendrocyte glycoprotein peptide (residues 35-55; MOG35-55). DMF or vehicle was administered twice a day by oral gavage. Visual acuity was measured longitudinally with optokinetic tracking. Post-mortem analyses included quantification of RGCs in retinal flatmounts and quantitative PCR (qPCR) of Nrf2 target genes and regulators of myelin. Retrospective chart analyses were performed using data obtained from deidentified files of patients with RRMS.
Results: In the EAE mouse studies, DMF decreased optic neuritis severity, preserved vision and RGCs, and concomitantly reduced motor deficits when administered by two different treatment regimens (prevention or interventional). DMF was more efficacious when administered as an interventional therapy, and the beneficial effects occurred independently of the induction of Nrf2 target genes. A complementary retrospective chart analysis demonstrated that DMF increased the time to a recurrence of optic neuritis, and protected against subsequent bouts of optic neuritis.
Conclusions: This work underscores the potential of DMF to mitigate the severity and recurrence of optic neuritis episodes in patients with RRMS.