Serono S.A.'s multiple sclerosis data comparing its Rebif interferon beta-1a to Biogen Inc.'s Avonex interferon beta-1a showed significant benefits for Rebif at 24 weeks, but neurologists believe that treatment decisions should be determined by longer-term data of at least one year. Additionally, some doctors believe that frequency of dosing is the primary driver of patients' therapy selections, with a pervading "fewer is better" mentality.

Serono (SRA; SWX:SEO, Geneva, Switzerland) must show superior efficacy compared to Avonex in a head-to-head trial in order to break through BGEN's U.S. Orphan Drug exclusivity, which expires in mid-2003. SRA hopes it has done just that, as the company said its 677-patient trial showed significance on the primary end point of relapse-free patients after 24 weeks, expressed as an adjusted odds ratio (see B12). According to SRA, patients treated with Rebif had a 90% greater chance of remaining relapse-free at 24 weeks than patients given Avonex (p=0.0005). The trial also will assess patients at 48 weeks.