New TYSABRI Data Presented at 64th Annual AAN Meeting Highlight Biogen Idec & Elan Commitment to Improving Outcomes in Multiple Sclerosis

Published April 27, 2012

Biogen Idec (NASDAQ: BIIB) and Elan Corporation, plc (NYSE: ELN) today announced findings from several studies of TYSABRI® (natalizumab) evaluating its long-term safety and efficacy in the treatment of multiple sclerosis (MS) across the course of disease and impact on MS-related symptoms such as fatigue. These data, as well as data relating to the companies’ risk stratification algorithm as a way to help enable individual benefit risk assessment for patients with MS, were accepted for presentation at the 64th Annual Meeting of the American Academy of Neurology (AAN).

“We continue to build on the extensive data we have for TYSABRI and are committed to studying its long-term use and potential effect on symptoms like fatigue, which MS patients struggle with every day,” said Douglas E. Williams, Ph.D., executive vice president of Research and Development at Biogen Idec. “Our research is aimed at discovering additional ways TYSABRI can help physicians and patients best manage the symptoms of MS and make informed and personalized treatment choices.”

Long-Term Observational Study of TYSABRI

Initial results from the TYSABRI Observational Program (TOP) indicate that post-baseline annualized relapse rates (ARR) after four years for patients receiving TYSABRI therapy decreased from 1.99 at baseline to 0.28 (p<0.0001); disability, as measured by the Expanded Disability Status Scale (EDSS), remained stable over time. TOP is an ongoing open-label, multicenter, observational study designed to assess long-term outcomes in patients with relapsing-remitting MS (RRMS) in Europe, Australia, and Canada. TOP is expected to enroll more than 4,500 patients who will be followed for 10 years.

Neither reduction in ARR nor stabilization of a patient’s EDSS was affected by the type of treatment they were using before initiating TYSABRI therapy. However, ARR were lowest in immunosuppressant (IS) therapy-naïve patients and highest in patients who had used IS therapy (p<0.0001).

The incidence and type of serious adverse events (SAEs) seen in these patients after long-term use was consistent with TYSABRI’s known safety profile. There were no significant differences by baseline treatment history in the incidence of SAEs, infection-related SAEs, or progressive multifocal leukoencephalopathy (PML) during TYSABRI therapy, although there was a trend of higher incidence of PML in patients with prior IS use.

“TOP may help provide insight into the potential impact current treatment may have on long term efficacy and safety outcomes with TYSABRI,” said Professor Ludwig Kappos, MD, chair of Neurology, Research Group Leader Clinical Neuroimmunology and Neurobiology, Department of Biomedicine, University Hospital, Basel, Switzerland. “The reduction of MS relapse and stable disability progression that we observed with TYSABRI in the TOP study across naive and previously treated patients was sustained after four years of treatment.”

Risk-Stratification Initiatives