Appropriate Use of Interferon Beta-1a in Multiple Sclerosis

Multiple sclerosis (MS), a chronic inflammatory demyelinating disease of the central nervous system, is the most common crippling neurological disease of young adults in the US. The 2 basic clinical forms of the disease (relapsing and progressive), which can occur singly or in combination, encompass a wide range of clinical severities are usually established between 18 and 35 years of age and can persist an entire lifetime. Life expectancy of 20 years is 85% of normal. Historically, the standard proven and generally accepted clinical treatment of the disease has been corticotropin (ACTH) and methylprednisolone, which benefited clinical relapses but had no effect on clinical disability (the most important factor influencing the lives of individual MS patients) or other aspects of the chronic course of the disease. The most important new development in the treatment of MS has been the introduction of interferon beta into the clinic. Two forms of recombinant interferon beta have been approved by the FDA for use in relapsing MS: interferon beta-1b (IFN-β-1b) and interferon beta-1a (IFN-β-1a). The efficacy of IFN-β-1b in the treatment of relapsing-remitting MS was established first but no effect on physical disability progression was discerned. In contrast, well designed trials of intramuscular IFN-β-1a (Avonex®) 6.0 MIU (30μ) weekly and subcutaneous IFN-α-1a (Rebif®) 6 MIU (22μg) or 12 MIU (44μg) 3 times weekly produced a significant delay in the time to sustained progression in physical disability, the first MS treatment to exert such a prophylactic effect. Additionally, IFN-β-1a significantly reduced clinical relapses and acute and chronic brain lesions revealed by MRI examinations. It is currently believed that IFN-β-1a treatment alters the fundamental course of relapsing MS. The mechanisms of the therapeutic benefit of recombinant interferon betas are incompletely understood but may include augmentation of suppressor T cell function, inhibition of interferon gamma actions, inhibition of T cell activation, or induction of interleukin-10 gene transcription.