May 2. 2000
MedscapeWire

Hit early and hit hard is the message from new long-term results of the Prevention of Relapses and Disability by Interferon beta-1a Subcutaneously in Multiple Sclerosis (PRISMS) trial. Mark Freedman, MD, professor of neurology at the University of Ottawa and director of the multiple sclerosis clinic at The Ottawa Hospital, reported the 4-year results at the American Academy of Neurology 52nd annual meeting in San Diego at a late-breaking news session.

"These data demonstrate that if patients are treated early with high-dose interferon beta-1a, the progression of disease can be delayed," Dr. Freedman said. "The results clearly indicate that beta interferons can dramatically modify the natural course of the disease over a 4-year period, which hopefully translates into an even longer-term benefit."

The PRISMS trial is one of the largest studies ever conducted of patients with relapsing remitting multiple sclerosis (RRMS), made up of 560 patients from 22 centers in 9 countries. The long-term data are the result of an extension phase of the original PRISMS trial. The first phase compared 2 doses of interferon beta-1a (Rebif) — 22 µg or 44 µg 3 times/week — with placebo. Results after 2 years demonstrated efficacy on all clinical and MRI measures for patients in both treatment arms compared with placebo. The study was extended to assess long-term efficacy.

A total of 506 patients (90% of the original cohort) continued in the extension phase of the trial. Those patients who switched from placebo to active therapy experienced a 52% to 54% reduction in relapse rates and had significant reductions in MRI activity and lesion burden. Nonetheless, patients in both treatment arms fared better than those who switched from placebo to treatment in the second phase of the study. Furthermore, patients on the higher, 44 µg dose from the beginning of the trial experienced longer delays before relapse and disease progression than either the placebo/treatment group or the lower-dose treatment group. Both treatment groups had markedly diminished development of active lesions on MRI as well as lower accumulation of lesion burden over time compared with placebo.