General Information

Avonex (Interferon beta-1a) balances the expression of pro- and anti-inflammatory agents in the brain, and reduces the number of inflammatory cells that cross the blood brain barrier. Overall, therapy with interferon beta leads to a reduction of neuron inflammation. The mechanism of action by which Avonex exerts its effects in patients with multiple sclerosis is unknown.

Avonex is specifically indicated for the treatment of relapsing forms of multiple sclerosis (MS), to include clinically isolated syndrome, relapsing-remitting disease, and active secondary progressive disease, in adults.

Avonex is supplied as a solution for intramuscular injection. The recommended dose is 30 micrograms once a week. To reduce the incidence and severity of flu-like symptoms that may occur when initiating Avonex therapy at a dose of 30 micrograms, treatment may be started at a dose of 7.5 micrograms and the dose may be increased by 7.5 micrograms each week for the next three weeks until the recommended dose of 30 micrograms is achieved.

Clinical Results

The FDA approval of Avonex was based on the MSCRG clinical trial (Study 1) and the CHAMPS clinical trial (Study 2).

Study 1/MSCRG was a 2-year, randomized, double-blind, placebo-controlled study of 301 patients with relapsing MS in which 282 patients completed 1 year on study, and 172 (Avonex, n=85; placebo, n=87) patients completed 2 years on study. The primary endpoint was time to disability progression, defined as a ≥1-point increase in EDSS score sustained for at least 6 months, to help distinguish permanent increase in disability from a transient (due to an exacerbation) increase. In the MSCRG (Study 1) pivotal trial, Avonex significantly reduced the risk of sustained disability progression at 2 years. 78% of patients taking Avonex had no sustained disability progression at 2 years compared with 65% of placebo-treated patients. The percentage of patients progressing in disability by the end of 2 years was 22% in the Avonex group and 35% in the placebo group.

Study2/CHAMPS was a randomized, double-blind, placebo-controlled study of 383 patients at high risk for developing clinically definite multiple sclerosis (CDMS) who were followed for up to 3 years or until time to second relapse in an anatomically distinct region of the central nervous system, defined in CHAMPS as CDMS. The primary endpoint was time to second relapse. The time to second relapse was significantly delayed in Avonex-treated patients compared to placebo-treated patients. 79% of patients taking Avonex were relapse free at 2 years compared with 61% of placebo-treated patients. The percentage of patients developing a second relapse within 2 years was 21% in the Avonex group and 39% in the placebo group.