Background: Prolonged therapy with interferon beta (IFN beta) often leads to the development of anti-IFN beta binding antibodies (BAbs). A subset of the BAbs is of a neutralizing nature (neutralizing antibodies, NAbs) and is associated with reduced clinical efficacy of therapy. Myxovirus-resistance-protein A (MxA) has proven to be a reliable biomarker of IFN beta bioactivity. We analyzed the prognostic value of MxA mRNA, NAbs, and BAbs on the risk of having a new relapse in IFN beta-treated patients.
Methods: A 3-year study was conducted in 137 IFN beta-treated patients. Blood samples for BAbs, NAbs, and MxA mRNA measurements were taken after 12 +/- 3 months of therapy. Analysis of relapse-free survival (RFS) was performed for all measures by using known thresholds, generating "positive" and "negative" groups. Also, time between sampling and following relapse and risk of new relapses were calculated.
Results: The MxA-negative group showed poorer RFS rates than the MxA-positive group [p < 0.0001, hazard ratio (HR) = 2.87]. Likewise, the NAb-positive group showed poorer RFS rates than the NAb-negative group (p =0.0013; HR = 2.49). On the contrary, BAb measurement did not show a clear clinical significance.
Conclusions: Findings indicate that measurements of both myxovirus-resistance-protein A (MxA) and neutralizing antibodies (NAbs) predict the risk of new relapses; however, the slightly stronger prognostic significance of MxA mRNA and the easier method for it measurement make MxA mRNA the preferred biomarker for monitoring interferon beta (IFN beta)-treated patients. This information can be used to better tailor treatment to the individual patient with MS.