Daclizumab shows potential for new immunoregulatory approach to treating MS

Cambridge, Mass. and Redwood City, Calif. – February 16, 2010 – Biogen Idec (NASDAQ: BIIB) and Facet Biotech Corporation (NASDAQ: FACT) today announced the publication of Phase 2 data showing that the addition of daclizumab to interferon beta (IFNβ) led to a significant reduction in the number of new or enlarged multiple sclerosis (MS) lesions when compared to IFNβ alone in patients with active relapsing forms of MS. The trial, called CHOICE, also showed that daclizumab led to an increase in a subset of the natural killer (NK) cells that help regulate the immune system. These data were published in Online First, the online edition of The Lancet Neurology, and will be published in the April issue of the Lancet Neurology.

Study results showed that daclizumab 2mg/kg administered subcutaneously every two weeks in combination with IFNβ reduced the number of new or enlarged gadolinium contrast-enhancing lesions (Gd-CELs) by 72 percent versus IFNβ therapy alone. The presence of Gd-CELs is thought to indicate inflammation within the central nervous system that corresponds with MS disease activity. In addition, treatment with daclizumab resulted in a seven- to eight-fold increase of CD56bright NK cells, which was associated with a decrease in disease activity. Daclizumab was well-tolerated in the CHOICE trial and common adverse events occurred with a similar frequency in each of the treatment groups.

"The CHOICE trial demonstrated that daclizumab was associated with a robust increase in important cells that help regulate the immune system, as well as a significant reduction in MS lesion formation," said John W. Rose, M.D., professor of Neurology, Research Laboratory, Veterans Affairs Salt Lake City Health Care System and the University of Utah, and an author on the manuscript. "Previous studies have shown that people with MS have less of these immunoregulatory cells than people without MS which, coupled with the reduction in active lesions, supports further study of daclizumab."

Multiple sclerosis, one of the most common neurological disorders, affects more than 400,000 people in the United States each year. Despite significant advances in MS therapy, many patients continue to experience disease activity. There is a need for additional MS therapies that offer new approaches to treating the disease.

Daclizumab is a humanized monoclonal antibody that binds to CD25, a high affinity receptor that is expressed at low levels on resting T cells, which are a type of immune cell, and at high levels on T cells that can become activated in response to autoimmune conditions such as MS.

"Daclizumab is believed to work by selectively targeting immune cells that play a key role in MS without depleting healthy immune cells and has the potential to provide a new approach to treating this chronic and debilitating disease," said Gilmore O'Neill, senior director, Experimental Neurology at Biogen Idec. "Daclizumab was well tolerated in the CHOICE trial and significantly reduced MS activity in patients who were not responding to interferon beta."

"We believe the results from the CHOICE study, combined with clinical data from smaller trials of daclizumab in MS, provide a basis for advancing daclizumab into registrational studies as a novel therapeutic for the treatment of patients with relapsing MS," said Mark Rolfe, Ph.D., senior vice president and chief scientific officer of Facet Biotech. "Despite advances in MS treatment, there remains a significant unmet medical need for new therapies such as daclizumab and we look forward to seeing data from our registrational studies."

Results from this Phase 2 study provided evidence for Biogen Idec and Facet Biotech to continue the development of daclizumab in two registrational trials in MS. The Phase 2b SELECT trial is evaluating the efficacy and safety of monthly subcutaneous daclizumab as a monotherapy versus placebo, and is currently enrolling patients. The Phase 3 DECIDE trial is expected to be initiated in the second quarter of 2010.

The CHOICE study is the first randomized, double-blind, placebo-controlled trial that evaluated the efficacy and safety of daclizumab (DAC) when added to IFNβ therapy. The study enrolled 230 patients, ages 18 to 55 years, with active relapsing MS who had an entry score of five or less on the Expanded Disability Status Scale (EDSS). The patients had to be taking a stable IFNβ regimen for a minimum of six months prior to enrollment. During the year prior to enrollment, patients had to have experienced at least one MS relapse or incurred at least one MS lesion of the brain or spinal cord while on a stable IFNβ regimen.

Patients remained on their baseline IFNβ regimens and were randomized in a ratio of 1:1:1 to three "add-on" treatment groups for 24 weeks: 2mg/kg daclizumab administered subcutaneously every two weeks (DAC high dose/ IFNβ); 1mg/kg daclizumab administered every four weeks (DAC low dose/ IFNβ); or placebo (placebo/ IFNβ).

The primary endpoint of the study was the total number of new or enlarged Gd-CELs measured monthly on brain MRI scans collected between weeks eight to 24. Additional endpoints included changes in the number and volume of lesions on TI- and T2-weighted MRIs, clinical relapse as assessed by the annualized relapse rate (ARR) and time to relapse, changes in EDSS and Multiple Sclerosis Functional Composite-3 (MSFC-3) scores, immunogenicity, pharmacokinetics (PK), pharmacodynamics (PD), clinical laboratory abnormalities and adverse events (AEs).

Compared with patients on placebo/IFNβ therapy alone, there was a 72 percent reduction in the number of new or enlarged Gd-CELs between weeks eight and 24 in the DAC high dose/IFNβ group (p=0.004, 95% CI 34%, 88%) and a 25 percent reduction in the DAC low dose/IFNβ group (p=0.51, 95% CI -76%, 68%). Daclizumab reduced MS lesion activity as early as week four with an average of 2.1 new or enlarged MS lesions appearing in the placebo/IFNβ group versus 0.9 new or enlarged MS lesions for the DAC high dose/IFNβ group.

Daclizumab treatment was generally well-tolerated. Common adverse events were similar in all treatment arms. Grade 3 adverse events were observed in 24 percent of DAC/IFNβ-treated patients and 14 percent of placebo/IFNβ-treated patients. The most frequent grade 3 adverse events were infections, which occurred in 7 percent of DAC/IFNβ-treated patients and 3 percent of placebo/IFNβ-treated patients. There were no opportunistic infections or deaths, and all infections resolved with standard therapies.

Daclizumab is a humanized monoclonal antibody that binds to the high affinity IL-2 receptor and selectively inhibits this receptor on activated T cells. Daclizumab is an investigational agent in clinical development for the treatment of MS under a collaboration between Facet and Biogen Idec. Daclizumab is not approved for the treatment of MS.

Biogen Idec creates new standards of care in therapeutic areas with high unmet medical needs. Founded in 1978, Biogen Idec is a global leader in the discovery, development, manufacturing, and commercialization of innovative therapies. Patients worldwide benefit from Biogen Idec's significant products that address diseases such as lymphoma, multiple sclerosis, and rheumatoid arthritis. For product labeling, press releases and additional information about the company, please visit www.biogenidec.com.

Facet Biotech is a biotechnology company dedicated to advancing its pipeline of five clinical-stage products focused in multiple sclerosis and oncology, leveraging its research and development capabilities to identify and develop new oncology drugs and applying its proprietary next-generation protein engineering technologies to potentially improve the clinical performance of protein therapeutics. For additional information about the company, please visit www.facetbiotech.com.

This press release contains forward-looking statements regarding the development of daclizumab in multiple sclerosis. These statements are based on the companies' current beliefs and expectation. Drug development involves a high degree of risk. Factors which could cause actual results to differ materially from the companies' current expectations include the risk that we may not fully enroll our planned clinical trials, unexpected concerns may arise from additional data or analysis, regulatory authorities may require additional information, further studies, or may fail to approve the drug, or the companies may encounter other unexpected hurdles. Other factors that may cause actual results to differ materially from those expressed or implied in the forward-looking statements in this press release are discussed in Facet Biotech's and Biogen Idec's filings with the Securities and Exchange Commission (SEC), including the "Risk Factors" sections of the companies' periodic reports on Form 10-K and Form 10-Q filed with the SEC. Copies of each company's filings with the SEC may be obtained at the "Investors" section of their respective websites (www.facetbiotech.com and www.biogenidec.com). The companies expressly disclaim any obligation or undertaking to release publicly any updates or revisions to any forward-looking statements contained herein to reflect any change in their expectations with regard thereto or any change in events, conditions or circumstances on which any such statements are based for any reason, except as required by law, even as new information becomes available or other events occur in the future. All forward-looking statements in this press release are qualified in their entirety by this cautionary statement.

MEDIA CONTACTS:
Biogen Idec
Kate Weiss
617-914-6524

INVESTOR CONTACTS:
Biogen Idec
John Applegate
617-679-2812

Facet Biotech Corporation
Jean Suzuki
Jean.Suzuki@facetbiotech.com
Ph: 650-454-2648