Interferon beta-1a (also interferon beta 1-alpha) is a cytokine in the interferon family used to treat multiple sclerosis (MS). It is produced by mammalian cells, while interferon beta-1b is produced in modified E. coli. Some claims have been made that Interferons produce about an 18–38% reduction in the rate of MS relapses.

Interferon beta has not been shown to slow the advance of disability.Interferons are not a cure for MS (there is no known cure); the claim is that interferons may slow the progress of the disease if started early and continued for the duration of the disease.