GENEVA, Switzerland, Feb. 29 --

New data from the largest and most comprehensive controlled long-term study in patients with relapsing-remitting multiple sclerosis (RRMS) has shown continued benefit of Rebif(R) 22 mcg and Rebif(R) 44 mcg administered three times weekly for four years. The PRISMS(1) four year data demonstrate a dose-effect relationship on clinical as well as MRI parameters with high dose Rebif(R) 3 x 44 mcg being superior to 3x22 mcg. In addition, the data also demonstrated that early treatment is better than delayed treatment and that the benefit of Rebif(R) on relapse rate may be greater than previously thought. Together, the data provide strong support to the concept of treating with the highest tolerated dose in order to gain maximum benefit and prevent disease progression, and to treat early (as issued by the guidelines of the US National MS Society(2)).

The PRISMS study began in 1994, involving 560 patients at 22 centers in 9 countries. Two year data were published(3) in 1998 demonstrating that both Rebif(R) 3 x 22 mcg and Rebif(R) 3 x 44 mcg per week significantly reduced the number and severity of relapses, delayed disability progression and reduced disease activity and burden of disease as measured in magnetic resonance imaging (MRI). The new data are from the extension phase of this study up to four years. Over 90 percent (506) of the originally enrolled patients entered the extension phase and the vast majority of these completed the full four years. The objectives of the extension phase included the assessment of long-term benefits on the frequency of relapses, delay of disability progression, changes in MRI activity and burden of disease, dose-response and the benefit of early versus late therapy onset.

"This is very important data and good news for the multiple sclerosis community. The study was the best designed of any of the trials conducted with interferon in relapsing-remitting multiple sclerosis to date and importantly with the longest controlled follow-up," comments Mark Freedman, MD, Director of the Multiple Sclerosis Clinic at Ottawa Hospital, General Campus, and Associate Professor of Medicine (Neurology) at the University of Ottawa, an investigator in the PRISMS trial. "It clearly indicates that beta-interferons can dramatically modify the natural course of the disease over four years, an effect that will hopefully continue for even longer. It also reinforces the need to treat as early as possible with the highest tolerable dose. We now have additional scientific evidence that through the continued use of Interferon beta-1a we are able to provide our patients with optimal care."