Outcomes of Stable Multiple Sclerosis Patients Staying on Initial Interferon Beta Therapy Versus Switching to Another Interferon Beta Therapy: A US Claims Database Study

INTRODUCTION: This study was designed to assess real-world outcomes of patients with multiple sclerosis (MS) who were stable on interferon (IFN) beta therapy in the year prior to switching to another IFN beta therapy versus those who continued on the initial treatment. METHODS: This study used administrative claims from MarketScan Commercial Claims and Encounters Database, from January 1, 2010, to March 31, 2015, to identify MS patients aged 18–64 years who remained relapse free for at least 1 year while continuously treated with an IFN beta therapy. Stable patients remaining on their initial IFN beta therapy (no-switch patients) were matched with stable patients who switched IFN beta therapy (switch patients) using propensity score matching (first claim = index date). Outcome measures included annualized relapse rate (ARR), the percentage of patients who relapsed, medication possession ratio, and the proportion of days covered and were measured during the year following the index date. RESULTS: This study identified 531 patients in the no-switch group and 177 patients in the switch group, with subsets of 270 patients in the no-switch group and 90 patients in the switch group stable on intramuscular (IM) IFN beta-1a therapy. All outcomes during the follow-up year were significantly better in the no-switch group than in the switch group. For all patients, ARR in the switch group was more than twice that in the no-switch group (P = 0.002). For patients stable on IM IFN beta-1a at baseline, ARR was twice as high in the switch group as in the no-switch group (P = 0.012). CONCLUSION: Among all patients stable on IFN beta therapy and the subset stable on IM IFN beta therapy in particular, those who remained on therapy had significantly better outcomes than those who switched to another IFN beta therapy. FUNDING: Biogen (Cambridge, MA, USA).