Biological responsiveness to first injections of interferon-beta in patients with multiple sclerosis

This study is the first to evaluate biological response to first injections of interferon-beta (IFNβ) in patients with multiple sclerosis. MxA mRNA was measured in 96 patients receiving IFNβ-1a (Avonex, n=32), IFNβ-1b (Betaferon, n=19), IFNβ-1a (Rebif) 22 μg (n=30), or IFNβ-1a 44 μg (n=15). Patients were analysed before, 3 and 24 h after the first injection, and 12 h after the second administration. Results showed that up-regulation was evident within 3 h of IFNβ injection, peaked 12 h after injection, and progressively declined 24 h after administration. The cumulative responses were similar after a single administration, regardless of product/dose. Moreover, data indicate that the abolition of the biological activity detected during IFNβ therapy is due to underlying phenomena (e.g., neutralizing antibodies), because all patients were constitutively responders to IFNβ at treatment initiation.