General Information

Rebif (interferon beta-1a) has been approved by the FDA for the treatment of relapsing forms of multiple sclerosis. Rebif has been shown to decrease the frequency of clinical exacerbations and delay the accumulation of physical disability in patients with MS. Rebif previously was approved in Europe in 1998 and currently is registered for use in over 70 countries.

Mechanism of Action

Interferons are a family of naturally occurring proteins that are produced by eukaryotic cells in response to viral infection and other biological inducers. Interferons possess immunomodulatory, antiviral and antiproliferative biological activities. They exert their biological effects by binding to specific receptors on the surface of cells. Type 1 interferons have considerably overlapping, but also distinct, biological activities. Interferon beta is produced naturally by various cell types including fibroblasts and macrophages. Binding of interferon beta to its receptors initiates a complex cascade of intracellular events that leads to the expression of numerous interferon-induced gene products and markers, including 2’, 5’-oligoadenylate synthetase, beta 2-microglubin and neopterin, which may mediate some of the biological activities. The specific interferon-induced proteins and mechanisms by which interferon beta-1a exerts its effects in multiple sclerosis have not been fully defined (from Rebif package insert).

Side Effects

In clinical trials, the most commonly reported adverse reactions to Rebif were:

Injection site disorders

Flu-like symptoms

Abdominal pain

Depression

Elevation of liver enzymes

Blood cell abnormalities

Depression and suicidal ideation have been reported to occur more frequently in patients being treated with interferon compounds, including Rebif.

Clinical Trial Results

FDA approval of Rebif was based on the results of two large multi-center studies evaluating the safety and efficacy of the drug in patients with relapsing-remitting multiple sclerosis (RRMS). The first study was a randomized, double-blind, placebo-controlled study of 560 subjects with multiple sclerosis for at least one year. Subjects received either placebo, Rebif 22 mcg or Rebif 44 mcg, administered three times a week for a duration of two years. Results indicated that both the 22 mcg and 44 mcg doses of Rebif significantly reduced the number of exacerbations per subject as compared to placebo. There was no statistically significant difference between percent reduction of exacerbations in subjects receiving 22 mcg (29 percent reduction) and 44 mcg (32 percent reduction). A secondary endpoint was the progression of disability, defined as an increase in the Kurtzke Expanded Disability Status Scale (EDSS) of at least one1 point sustained for at least three months. Results showed that the time to onset of progression in disability sustained for three months was significantly longer in subjects treated with either dose or Rebif than in subjects received placebo only.

The second study was a randomized, open-label, evaluator-blinded, active comparator study comparing the effects of Rebif 44 mcg to those of Avonex 30 mcg in 677 subjects with RRMS who had not been treated with interferon before. Subjects received either Rebif 44 mcg (three times weekly, subcutaneously) or Avonex 30 mcg (once weekly, intramuscularly) and underwent repeated clinical and MRI assessments during the course of treatment. Results showed that during the first 24 weeks of treatment, 75 percent of subjects receiving Rebif did not experience a relapse, compared to 63 percent of subjects receiving Avonex who did not experience a relapse during the same period. This difference was statistically significant. In addition, researchers assessed the combined unique active lesions as measured by MRI. At 24 weeks, Rebif-treated subjects had an average of 0.8 active lesions per scan, while Avonex-treated patients averaged 1.2 lesions per scan. This represents a reduction of approximately one-third of lesion activity in the subjects receiving Rebif.