Rebif trial disappointing for secondary-progressive MS.

The results of a large international, placebo-controlled clinical trial of Rebif (interferon beta-1a) for secondary-progressive MS were disappointing, though the trial included some positive observations. Secondary-progressive MS begins as relapsing-remitting MS and then develops a pattern of occasional attacks with on-going "progressive" increases in disability. About half of all people with relapsing-remitting MS develop the secondary-progressive pattern within 10 years of diagnosis.

Ares-Serono, the manufacturer of Rebif, designed the 3-year study to see if the drug could slow progression of disability. In this study, it did not. People who took the active drug had fewer and less severe attacks, however, and less brain lesion activity as seen on MRI scans.

The Rebif trial is one of several studies on the interferon drugs for secondary-progressive MS. A large European trial of Betaferon (interferon beta-1b, marketed as Betaseron in the U.S.) in secondary-progressive MS showed a slowing of progression of disability. (See Fall 1998, p. 39.) Currently, a North American trial of Betaseron and an international study of Avonex (interferon beta-1a) for people who have secondary-progressive MS are in progress.

Rebif is available in Canada and Europe for relapsing-remitting MS, but did not get FDA approval for marketing in the U.S. The FDA found no treatment advantage in using Rebif compared to the other interferons. Under the terms of the Orphan Drug Act, which offers marketing protections for similar agents that are already available, the FDA has not allowed Rebif to be marketed in the U.S. (See Spring 1999, p. 34.)