Randomised double-blind placebo-controlled study of interferon beta-1a in relapsing/remitting multiple sclerosis. PRISMS (Prevention of Relapses and Disability by Interferon beta-1a Subcutaneously in Multiple Sclerosis) Study Group. Placebo-controlled multicentre randomised trial of interferon beta-1b in treatment of secondary progressive multiple sclerosis. European Study Group on interferon beta-1b in secondary progressive MS.
Previous trials of interferon beta in multiple sclerosis (MS) have shown efficacy, but the degree of clinical benefit remains uncertain, and the optimum dose is not known. We undertook a double-blind, placebo-controlled study in relapsing/remitting MS to investigate the effects of subcutaneous interferon beta-1a.
                560 patients with Kurtzke expanded disability status scale (EDSS) scores of 0-5.0, from 22 centres in nine countries, were randomly assigned subcutaneous recombinant interferon beta-1a 22 microg (n=189), or 44 microg (n=184), or placebo (n=187) three times a week for 2 years. Neurological examinations were done every 3 months. All patients had MRI twice yearly and 205 had monthly scans in the first 9 months of treatment. Analysis was by intention to treat.
                Clinical data on 533 (95%) patients were available at 2 years. The relapse rate was significantly lower at 1 and 2 years with both doses of interferon beta-1a than with placebo (mean number per patient 1.82 for 22 microg group, 1.73 for 44 microg group vs 2.56 for placebo group: risk reductions 27% [95% CI 14-39] and 33 [21-44]). Time to first relapse was prolonged by 3 and 5 months in the 22 microg and 44 microg groups respectively, and the proportion of relapse-free patients was significantly increased (p<0.05). Interferon beta-1a delayed progression in disability, and decreased accumulated disability during the study. The accumulation of burden of disease and number of active lesions on MRI was lower in both treatment groups than in the placebo group.
                Subcutaneous interferon beta-1a is an effective treatment for relapsing/remitting MS in terms of relapse rate, defined disability, and all MRI outcome measures in a dose-related manner, and it is well tolerated. Longer-term benefits may become clearer with further follow-up and investigation. The beneficial effects of interferon beta have only been shown for patients in the relapsing-remitting phase of multiple sclerosis (MS). The role of interferon beta in the treatment of patients who are in the secondary progressive phase of the disease (SP-MS), and for whom no effective drug treatment is available, has not been assessed.
                In this multicentre, double-masked, randomised, placebo-controlled trial, outpatients with SP-MS having scores of 3.0-6.5 on the Expanded Disability Status Scale (EDSS) received either 8 million IU interferon beta-1b every other day subcutaneously, or placebo, for up to 3 years. The primary outcome was the time to confirmed progression in disability as measured by a 1.0 point increase on the EDSS, sustained for at least 3 months, or a 0.5 point increase if the baseline EDSS was 6.0 or 6.5. A prospectively planned interim analysis of safety and efficacy of the intention-to-treat population was done after all patients had been in the study for at least 2 years.
                358 patients with SP-MS were allocated placebo and 360 were allocated interferon beta-1b; 57 patients (31 placebo, 26 interferon beta-1b) were lost to follow-up. There was a highly significant difference in time to confirmed progression of disability in favour of interferon beta-1b (p=0.0008). Interferon beta-1b delayed progression for 9-12 months in a study period of 2-3 years. The odds ratio for confirmed progression was 0.65 (95% CI 0.52-0.83). This beneficial effect was seen in patients with superimposed relapses and in patients who had only progressive deterioration without relapses. Positive results were also obtained regarding time to becoming wheelchair-bound, relapse rate and severity, number of steroid treatments and hospital admissions, as well as on magnetic resonance imaging variables. The drug was safe and side effects were in line with previous experience with interferon beta-1b. The study was stopped after the interim results gave clear evidence of efficacy.
                Treatment with interferon beta-1b delays sustained neurological deterioration in patients with SP-MS. Interferon beta-1b is the first treatment to show a therapeutic effect in patients with SP-MS.
Limited data on the effect of ß-interferon treatment on PPMS exists. Only two single-centre placebo controlled trials of interferon beta have been done. Based on this review, the included studies showed that ß-interferon treatment was not associated with reduced disability progression in PPMS patients. However, the trial population was too small to allow definitive conclusions on the efficacy of ß-interferon therapy in PPMS patients. Larger research studies need to be done in patients with PPMS in order to clarify whether ß-interferon is effective in this population.