Randomized pilot trial of beta INF1a (Avonex) in patients with inclusion body myositis

Background: Inclusion body myositis (IBM) is the most common acquired disea se of muscle in adults over the age of 50 years. Although there is compelli ng evidence for the importance of immunologic abnormalities in its pathogen esis, the cause of the disease is not known, and it is considered to be res istant to treatment with corticosteroids and other conventional immunosuppr essive agents. beta -Interferon (beta IFN), an immunomodulatory cytokine, i s a candidate therapeutic agent for IBM. Methods: A 24-week, multicenter, r andomized, placebo-controlled, parallel-group clinical trial of 30 mug of b eta -interferon-1a (beta INF1a) administered IM once a week in 30 patients with IBM was conducted. The primary goal was to establish the safety and to lerability of beta INF1a in IBM. A secondary goal was to obtain preliminary data on the efficacy of beta INF1a by measuring changes from baseline in m uscle strength and muscle mass. Results: Twenty-nine of the 30 subjects enr olled completed the study. Two subjects (one in the placebo group, one in t he beta INF1a group) experienced severe adverse events. One subject, random ized to receive beta INF1a, died from an ischemic bowel after resection of a colonic mass. No subjects required dosage reductions, and the adverse eve nt profile was similar for the placebo and beta INF1a groups. There were no significant differences in the changes in muscle strength and muscle mass between the placebo and beta INF1a groups at 6 months. Conclusions: beta IN F1a at a dose of 30 mug/week IM is well tolerated in IBM. Further studies a re needed to establish its therapeutic usefulness in this inflammatory myop athy.