Response to interferon beta-1a treatment in African American multiple sclerosis patients.

BACKGROUND African Americans (AAs) with multiple sclerosis (MS) seem to have a more severe disease course than white Americans (WAs). To our knowledge, it is not known to what extent treatment with interferon beta-1a will effect the MS disease course within the AA population. OBJECTIVE To compare the response to treatment with interferon beta-1a between AA and WA MS patients. DESIGN This is an exploratory post hoc analysis of the Evidence of Interferon Dose-Response: European North American Comparative Efficacy (EVIDENCE) study. SETTING The EVIDENCE study is a randomized controlled trial that compared the efficacy of once weekly, intramuscular, 30-microg interferon beta-1a treatment with thrice weekly, subcutaneous, 44-microg interferon beta-1a therapy in treatment-naïve MS subjects. PARTICIPANTS Thirty-six AA subjects were compared with 616 WA subjects. MAIN OUTCOME MEASURES The number of MS exacerbations, the proportion of exacerbation-free subjects, and the number of new MS lesions present on brain magnetic resonance imaging were compared between AA and WA subjects at 24 and 48 weeks after initiating treatment with interferon beta-1a. RESULTS The AA subjects experienced more exacerbations and were less likely to remain exacerbation free (statistical trends). The AA subjects developed more new MS lesions on T2-weighted brain magnetic resonance imaging at 48 weeks (P = .04). CONCLUSIONS Despite the small sample size, AA subjects appeared less responsive to treatment than WA subjects on outcome measures, reaching significance only for T2-weighted lesion count at 48 weeks. However, it is difficult to base these differences solely on response to treatment given the potential differing in MS disease course in AA patients.