Optimising MS disease-modifying therapies: antibodies in perspective

Abstract

A proportion of people with multiple sclerosis (MS) treated with interferon (IFN) a develop neutralising anti-IFN beta antibodies (NABs). The immunogenicity of the available commercial compounds relates to the genetic structure of the IFN beta molecule, its mode of production, glycosylation status, aggregate formation, commercial formulation, potency, dose, frequency and, possibly, route of administration. At present, it is not possible to predict who will develop NABs usually appear within the first 2 years of starting therapy. In patients treated with IFN beta in whom NABs persist for a significant period of time, their presence is associated with a reduction in both the biological effects and clinical efficacy. Approximately one third of NAB-positive patients with a titre > 20 NU/mL will revert to NAB-negative status with long-term follow-up. The persistence of NABs appears to be linked to the type of IFN beta treatment as well as the titre of antibodies. The overall efficacy of IFN beta and, hence, of any biological disease-modifying treatment (DMT) would be substantially improved if the development of NABs could be prevented or reversed. Although the overall efficacy of IFN beta in MS is relatively modest, the efficacy in individuals who remain NAB-negative is considerably better than in those who become persistently NAB-positive. One could argue that when comparing the 'true' clinical efficacy of different IFN beta products, the comparisons should be limited to the cohorts that remain NAB-negative. As a corollary, the therapeutic efficacy of IFN beta could be maximised if patients who tolerate higher-dose preparations could be prevented from developing persistent NABs. Strategies employed to prevent or reverse the development of NABs with other biological compounds (e. g. insulin, factor VIII, IFN beta, recombinant human erythropoietin) include improvements in the manufacturing process, immunosuppression, induction of tolerance and deimmunisation, and these should be considered in relation to biological DMT therapy as part of future clinical studies.

Neutralizing antibodies in MS therapy: reviewing the Rebif experience

“…For this reason, most reported studies have used the level of CPE inhibition to assess NAb presence and titer during MS therapy; however, variation in assay procedures (including cell line employed, serum dilution protocols, and 'reference' dose of IFN␤) have made comparing results from different laboratories difficult [13,14].…”

“…In order to assess the clinical significance of NAbs, it is particularly crucial that standard cutoff values be established to classify patients as NAb positive or NAb negative [14]. Ideally, these values should also bear some relationship to a clinically meaningful attenuation of IFN␤ function.…”

“…. at present, treatment decisions on optimizing therapy should still be largely based on clinical factors [14]. '…”

Quantification of Neutralizing Antibodies to Human Type I Interferons Using Division-Arrested Frozen Cells Carrying an Interferon-Regulated Reporter-Gene

“…Although direct comparisons among many of the studies is difficult because of the use of different neutralization assays and standards, comparative studies have shown that IFN-β1b is more immunogenic than IFN-β1a (Bertolotto and others 2002), possibly because of the lower specific activity of IFN-β1b and, hence, the higher protein mass injected. Amino acid differences and lack of glycosylation of IFN-β1b compared with the native protein or currently licensed recombinant forms of IFN-β1a or formulation characteristics may also contribute to the immunogenicity of IFN-β1b (Giovannoni 2004).…”