Prevalence of anti-drug antibodies against interferon beta has decreased since routine analysis of neutralizing antibodies became clinical practice

Background: Neutralizing antibodies (NAbs) against interferon beta (IFN beta) lead to loss of treatment efficacy in multiple sclerosis patients. The seroprevalence of NAbs in multiple sclerosis patients treated with IFN beta during 2003-2004 was 32% in a cross-sectional analysis of routine data. Objectives: The aim of this study was to investigate whether the seroprevalence of NAbs, the levels of NAb titres and the IFNa preparations used for treatment of multiple sclerosis patients had changed in 2009-2010. Methods: This study included 1296 patients, analysed for NAbs with the myxovirus resistance protein A gene expression assay in 2009-2010. Results: The seroprevalence of NAbs had decreased to 19% in 2009-2010, which is significantly lower compared with the previous study in 2003-2004 (p<0.0001). This decrease was attributed to the IFN beta-1a preparations only, not to IFN beta-1b. The frequency of patients with high positive titres decreased the most, from 16% to 7% (p<0.0001). Conclusions: NAb seroprevalence has decreased since NAb monitoring became clinical practice in 2003, especially for patients with high NAb titres. This might be due to the stricter monitoring of NAb titres that prompt NAb positive patients to stop treatment, to preferential use of less immunogenic drugs and to alteration of drug formulations.