Intramuscular interferon beta-1a is effective in Japanese patients with relapsing–remitting multiple sclerosis: a pre-treatment versus treatment comparison study of gadolinium-enhanced MRI brain lesions

Background and objective: Interferon beta (IFNβ) is standard therapy for multiple sclerosis (MS). The efficacy of intramuscular (IM) IFNβ-1a (AVONEX®) was assessed in 25 Japanese patients with relapsing–remitting MS (RRMS). Methods: Patients with RRMS not previously treated with IFNβ or other disease-modifying therapies were included in this 36-week study. The primary outcome was the average total number of gadolinium-enhanced lesions detected on four brain MRI scans during the last 12 weeks of 24 weeks’ treatment with IM IFNβ-1a 30 μg once weekly compared with the number during the 12-week pre-treatment period. Lesions were counted by blinded investigators. Results: IM IFNβ-1a significantly decreased the median number of gadolinium-enhanced lesions from 2.5 to 0.3 (p < 0.0001) compared with pre-treatment values. The median number of new gadolinium-enhanced lesions also decreased significantly from 2.0 to 0.3 (p = 0.0002). Serum neopterin was induced in a manner similar to that observed previously in a Caucasian RRMS population. No new adverse events occurred during the study. Conclusion: This first study of IM IFNβ-1a in Japanese patients with RRMS demonstrated a level of efficacy similar to that reported in Caucasian patients based on an assessment of pre-treatment and post-treatment gadolinium-enhanced lesions.