Different responses to interferon beta‐1b treatment in patients with neuromyelitis optica and multiple sclerosis

Background: Although the benefit of treatment for relapsing–remitting multiple sclerosis (MS) is firmly established, whether interferon beta‐1b (IFNB‐1b) therapy is efficacious for neuromyelitis optica (NMO) has been debated. Methods: We reviewed the responses to IFNB‐1b treatment in 18 patients with relapsing NMO and compared the results with those from 38 patients with relapsing–remitting MS. We compared clinical characteristics, the annualized relapse rate (ARR) and the probability of being relapse free before and after IFNB‐1b treatment in patients with NMO and MS. Results: The proportion of patients with more than 50% increase in the ARR after IFNB‐1b treatment was much higher in NMO than in MS (P = 0.046). ARR was significantly lower in patients with MS after IFNB‐1b administration than before (P = 0.015), but not in NMO. Kaplan–Meier and log‐rank statistical analyses revealed that relapse‐free rates were lower in NMO than MS after IFNB‐1b treatment (P = 0.032). The analyses also showed lower relapse‐free rates during the pre‐IFNB‐1b treatment period than the post‐IFNB‐1b treatment period in MS (P < 0.001), but not in NMO. Conclusion: IFNB‐1b treatment does not appear to be effective for preventing relapse in NMO likely because of differences between the immune‐pathogenesis of NMO and MS.