Intramuscular interferon beta-1a in chronic inflammatory demyelinating polyradiculoneuropathy

Objective: Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) shares immunologic features with multiple sclerosis (MS). Because IM interferon beta-1a (IM IFNβ-1a) is an effective and safe treatment for MS, we conducted a dose-ranging efficacy study of IFNβ-1a in patients with CIDP. Methods: Adults with IV immunoglobulin (IVIg)-dependent CIDP (n = 67) were enrolled in this 32-week double-blind trial and randomized to IM IFNβ-1a. Patients received 30 μg once weekly plus placebo (n = 12), IM IFNβ-1a 60 μg once weekly plus placebo (n = 11), IM IFNβ-1a 30 μg twice weekly (n = 11), IM IFNβ-1a 60 μg twice weekly (n = 11), or placebo twice weekly (n = 22). Participants were maintained on IVIg through week 16, when IVIg was discontinued. Patients who worsened were restarted on IVIg. The primary outcome was total IVIg dose (g/kg) administered from week 16 to 32. Results: There was no difference in total IVIg dose administered after week 16 for patients treated with IFNβ-1a (1.20 g/kg) compared with placebo (1.34 g/kg; p = 0.75). However, exploratory analyses suggested IFNβ-1a significantly reduced total dose of IVIg compared with placebo for participants who required either high-dose IVIg (>0.95 g/kg per month) or had greater weakness at baseline (Medical Research Council sum score <51). Adverse events included flu-like symptoms, headache, and fatigue in the IFNβ-1a groups. Conclusions: Interferon beta-1a (IFNβ-1a) therapy did not provide significant benefit over IV immunoglobulin (IVIg) therapy alone for patients with chronic inflammatory demyelinating polyradiculoneuropathy. However, IFNβ-1a might be beneficial for patients with more severe disability or those needing high doses of IVIg. Level of evidence: This study was designed to provide Class I evidence for the safety and efficacy of IM IFNβ-1a in the treatment of CIDP but has been subsequently classified as Class II due to a >20% patient dropout rate. Thus, this randomized, controlled clinical trial provides Class II evidence of no effect on primary and secondary endpoints of 4 dosage regimens of IM IFNβ-1a added to IVIg in persons with CIDP.