Safety profile and clinical activity of sifalimumab, a fully human anti-interferon α monoclonal antibody, in systemic lupus erythematosus: a phase I, multicentre, double-blind randomised study

Background Type I interferons (IFNs) appear to play a central role in disease pathogenesis in systemic lupus erythematosus (SLE), making them potential therapeutic targets. Methods Safety profile, pharmacokinetics, immunogenicity, pharmacodynamics and clinical activity of sifalimumab, an anti-IFN alpha monoclonal antibody, were assessed in a phase I, multicentre, randomised, double-blind, dose-escalation study with an open-label extension in adults with moderately active SLE. Subjects received one intravenous dose of sifalimumab (n = 33 blinded phase, 0.3, 1, 3, 10 or 30 mg/kg; n = 17 open-label, 1, 3, 10 or 30 mg/kg) or placebo (n = 17). Each phase lasted 84 days. Results Adverse events (AEs) were similar between groups; about 97% of AEs were grade 1 or 2. All grade 3 and 4 AEs and all serious AEs (2 placebo, 1 sifalimumab) were deemed unrelated to the study drug. No increase in viral infections or reactivation was observed. Sifalimumab caused dose-dependent inhibition of type I IFN-induced mRNAs (type I IFN signature) in whole blood and corresponding changes in related proteins in affected skin. Exploratory analyses showed consistent trends toward improvement in disease activity in sifalimumab-treated versus placebo-treated subjects. A lower proportion of sifalimumab-treated subjects required new or increased immunosuppressive treatments (12% vs 41%; p = 0.03) and had fewer Systemic Lupus Erythematosus Disease Activity Index flares (3% vs 29%; p = 0.014). Conclusions Sifalimumab had a safety profile that supports further clinical development. This trial demonstrated that overexpression of type I IFN signature in SLE is at least partly driven by IFN alpha, and exploratory analyses suggest that IFN alpha inhibition may be associated with clinical benefit in SLE.