Disease-Modifying Agents in the Treatment of Multiple Sclerosis: A Review of Long-Term Outcomes

Multiple sclerosis (MS) is a chronic, debilitating condition mediated by inflammation and neurodegeneration. The ultimate goal of treatment is to delay or halt the progression of irreversible disability. Disease-modifying drugs (DMDs), including beta interferon and glatiramer acetate during phase III trials, have been shown to reduce relapse rates in relapsing-remitting multiple sclerosis (RRMS) as detected by magnetic resonance imaging (MRI). However, the long-term effects of DMDs on MS progression are not very clear; therefore, the aim of this paper is to evaluate the evidence available of the long-term effects of DMDs on reducing the progression of multiple sclerosis. A number of open-label, prospective extensions that followed a cohort of patients enrolled in double-blind, placebo-controlled trials were examined. Methodological difficulties faced in designing a trial of extended duration were hard to overcome, however, and long-term, open-label extensions of interferon and glatiramer acetate failed to show significant beneficial effects in delaying disability progression, questioning the cost-effectiveness of these therapies in the long-term.