The STAR Study: a real-world, international, observational study of the safety and tolerability of, and adherence to, serum-free subcutaneous interferon β-1a in patients with relapsing multiple sclerosis.

Background: Adverse reactions, particularly injection site reactions (ISRs), are common reasons for nonadherence to injectable multiple sclerosis (MS) treatments. Adherence to MS treatment is important to ensure good treatment outcomes.

Objective: The aim of this study was to assess the local tolerability of subcutaneous (SC) serum-free interferon (IFN) β-1a in patients with relapsing MS over 1 year in a real-life, international setting. The study also assessed safety, disease activity, and adherence.

Methods: This was a prospective, international, multicenter, observational study of 251 patients with relapsing-remitting MS treated with SC serum-free IFN β-1a 44 μg or 22 μg 3 times weekly for 12 months or until early discontinuation. The primary end point was the proportion of patients with ISRs. Secondary end points included proportion of patients with adverse events (AEs); annualized relapse rate (ARR); proportion of patients remaining relapse-free; and adherence to treatment.

Results: During the observation period, 27.5% (69 of 251) of patients experienced nonserious ISRs, which was consistent with the incidence reported in clinical studies. Five patients discontinued treatment and 2 patients suspended treatment because of ISRs. Mean age was 35.8 years; patients were predominantly white (94.8%), and two thirds (66.1%) were female. The overall incidence of AEs was 63.7% (160 of 251), and overall safety and tolerability were assessed as excellent, very good, or good in >85% of patients. More than 70% of patients remained relapse-free, and the mean ARR was 0.4. More than 90% of patients had very good or good adherence to treatment; a significantly greater proportion of these were relapse-free at 12 months compared with those with fair or poor adherence (77.6% vs 50.0%; P = 0.0107), and their ARR was significantly lower (0.3 vs 0.9; P = 0.0055). Patients with fair or poor adherence had 4.6 times higher odds of experiencing a relapse than those with very good or good adherence.

Conclusions: The incidence of ISRs and the overall safety profile in this observational study, in an international population in a real-life setting, confirm the good local tolerability of SC serum-free IFN β-1a reported in clinical studies. The association between good adherence and a lower ARR underlines the importance of good adherence. The good local and general tolerability of SC IFN β-1a may help ensure a high level of adherence, which is associated with better clinical outcomes. ClinicalTrials.gov identifier: NCT01080027.