¹ Institute of Clinical Neuroscience, Sahlgrenska University Hospital, University of Göteborg, Göteborg, Sweden
² Neuroimmunology Unit, Department of Neurology, Tampere University Hospital and Medical School, University of Tampere, Tampere, Finland
³ Neurology Department, Århus Community Hospital, Århus, Denmark
⁴ Department of Neurology, Helsinki University, Helsinki, Finland
⁵ Department of Neurology, University Hospital of North Norway, Tromsö, Norway
⁶ Department of Neurology, Haukeland Hospital, Bergen, Norway
⁷ Department of Neurology, University Hospital, University of Lund, Lund, Sweden
⁸ Department of Neurology, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark

Correspondence to:
Correspondence to:
Professor Oluf Andersen
Institute of Clinical Neuroscience, Neurologen-Sahlgrenska, Sahlgrenska University Hospital, SE 413 45 Göteborg, Sweden; oluf.andersen{at}neuro.gu.se

Objective: Interferon (IFN) beta has repeatedly shown benefit in multiple sclerosis (MS) in reducing the rate of relapse, the disease activity as shown with magnetic resonance imaging and, to some degree, the progression of disability; however, it is unknown how much the therapeutic response depends on the dose, the subgroup involved, and the disease stage. This multicentre, double blind, placebo controlled study explored the dose–response curve by examining the clinical benefit of low dose IFN beta-1a (Rebif®), 22 µg subcutaneously once weekly, in patients with secondary progressive MS.

Methods: A total of 371 patients with clinically definite SPMS were randomised to receive either placebo or subcutaneous IFN beta-1a, 22 µg once weekly, for 3 years. Clinical assessments were performed every 6 months. The primary outcome was time to sustained disability, as defined by time to first confirmed 1.0 point increase on the Expanded Disability Status Scale (EDSS). Secondary outcomes included a sensitive disability measure and relapse rate.

Results: Treatment had no beneficial effect on time to confirmed progression on either the EDSS (hazard ratio (HR) = 1.13; 95% confidence interval (CI) 0.82 to 1.57; p = 0.45 for 22 µg v placebo) or the Regional Functional Status Scale (HR = 0.93; 95% CI 0.68 to 1.28; p = 0.67). Other disability measures were also not significantly affected by treatment. Annual relapse rate was 0.27 with placebo and 0.25 with IFN (rate ratio = 0.90; 95% CI 0.64 to 1.27; p = 0.55). The drug was well tolerated with no new safety concerns identified. No significant gender differences were noted.

Conclusions: This patient population was less clinically active than SPMS populations studied in other trials. Treatment with low dose, IFN beta-1a (Rebif®) once weekly did not show any benefit in this study for either disability or relapse outcomes, including a subgroup with preceding relapses. These results add a point at one extreme of the dose–response spectrum of IFN beta therapy in MS, indicating that relapses in this phase may need treatment with higher doses than in the initial phases.

Keywords: secondary progressive multiple sclerosis; interferon beta; randomised controlled trial

Abbreviations: EDSS, Expanded Disability Status Scale; EU-SPMS, European Secondary Progressive Multiple Sclerosis trial; HR, hazard ratio; IFN, interferon; IM, intramuscular; KFS, Kurtzke Functional System; MRI, magnetic resonance imaging; PH, proportional hazard; RFSS, Regional Functional System Score; RRMS, relapsing–remitting multiple sclerosis; SAE, serious adverse event; SC, subcutaneous; SPMS, secondary progressive multiple sclerosis; TTP, time to progression

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