Tolerability and safety profile of 12- to 28-week treatment with interferon beta-1b 250 and 500 µg QOD in patients with relapsing-remitting multiple sclerosis: A multicenter, randomized, double-blind, parallel-group pilot study

Abstract Background: It is not known whether the currently available treatment regimen of interferon beta-1b (IFN²-1b) 250 µg provides the maximum benefit possible in the treatment of relapsing-remitting multiple sclerosis (RRMS), or whether higher doses of IFN²-1b will prove to be more beneficial. Objective: The objective of the present study was to evaluate the tolerability and safety profile of IFN²-1b 500 µg compared with the currently approved 250-µg dose. Methods: A multicenter, randomized, double-blind, parallel-group pilot study was carried out to compare IFN²-1b 250 µg with IFN²-1b 500 µg, both self-administered SC QOD for ≥ 12 weeks in patients with RRMS. Patients in both groups started with 25% (0.25 mL) of their final dose and were scheduled to increase the dose by 0.25 mL every 2 weeks, so that the full dose (1.0 mL, 250 µg or 500 µg) would be reached by week 7. The primary outcome measure was the percentage of patients experiencing each of the following adverse events (AEs): influenza-like symptoms (general term used to code the presence of>1 symptom typical of influenza), fever, myalgia, asthenia, headache, injection-site reactions, injection-site pain, or liver or hematologic abnormalities. All patients underwent a priori magnetic resonance imaging (MRI) with 0.1 mmol/kg gadolinium (Gd)-diethylenetriaminepentaacetic acid as contrast medium at screening and at week 12. MRI evaluation was included as a safety measure to monitor for excessive new disease not visible through clinical symptoms. Results: Seventy-seven patients were assessed for inclusion in the study. Of these, 6 patients were screening failures and the remaining 71 were randomized to treatment (38–250 and 33–500 µg IFN²-1b). The uneven numbers in the groups were a consequence of the randomization process. Two patients in the 250-µg group (withdrawal of consent) and 1 in the 500-µg group (not completing follow-up visit) prematurely discontinued medication. The demographic characteristics were not significantly different between the 250-µg (n = 38; mean [SD] age, 37.9 [8.3] years; weight, 83.5 [19.0] kg; height, 168.4 [9.3] cm) and 500-µg (n = 33; mean [SD] age, 37.8 [7.7] years; weight, 82.3 [19.5] kg; height, 169.9 [10.5] cm) treatment groups. The patients in both groups were mostly white (87% and 73%, respectively). Baseline Expanded Disability Status Scale scores also were not significantly different between the 2 groups (mean [SD] score, 2.8 [1.4] vs 2.0 [1.4], respectively).