New TYSABRI Data Reaffirm Substantial Efficacy in Treatment of People with MS and Demonstrate Stability of Anti-JCV Antibody

  New TYSABRI Data Reaffirm Substantial Efficacy in Treatment of People with
  MS and Demonstrate Stability of Anti-JCV Antibody Status

– Continued Research into Risk Stratification and PML Early Detection Provides
                     Additional Insights for Physicians –

Business Wire

WESTON, Mass. -- March 18, 2013

Biogen Idec (NASDAQ: BIIB) and Elan Corporation, plc (NYSE: ELN) announced
results from several studies of TYSABRI^® (natalizumab) that demonstrate its
efficacy compared to other multiple sclerosis (MS) treatments, provide
additional data supporting anti-JC virus (JCV) antibody status stability, and
suggest better outcomes when progressive multifocal leukoencephalopathy (PML)
is detected early. These data will be presented at the 65th Annual Meeting of
the American Academy of Neurology (AAN) in San Diego.

“These new data reinforce our belief in the substantial efficacy TYSABRI has
demonstrated at both the early and advanced stages of relapsing forms of MS,”
said Alfred Sandrock, M.D., Ph.D., senior vice president, Development Sciences
and chief medical officer,Biogen Idec. “We are also encouraged by the
consistency in anti-JCV antibody status demonstrated over 18 months, as well
as results from our pursuit of additional paths to help mitigate the impact of
PML. These combined efforts may allow a more individualized approach when
selecting TYSABRI treatment, while helping physicians better understand a
patient’s benefit-risk profile.”

Substantial TYSABRI Efficacy Demonstrated Against First-Line Therapies

In an independent statistical analysis led by Timothy Spelman and Helmut
Butzkueven, M.D. at the University of Melbourne, with contribution by Fabio
Pellegrini and Annie Zhang, TYSABRI demonstrated a significantly lower rate of
first relapse compared to interferon beta (IFN) and glatiramer acetate (GA).
This propensity-matched analysis was conducted using data from two MS patient
registries: TYSABRI Observational Program (TOP) and MSCOMET. The results
indicate that relapses were not only more likely to occur in patients taking
IFN and GA, but that they occurred more quickly, when compared to patients
taking TYSABRI (hazard ratio 2.73, 95 percentconfidence interval 2.10-3.55,
p<0.001).

  *Comparison of Patients Treated with Natalizumab and
    Interferon-Beta/Glatiramer Using Propensity-Matched Multiple Sclerosis
    Registry Data (P01.211) will be available for viewing on Monday, March 18,
    2013 from 2:00 to 6:30 p.m. PDT

Anti-JCV Antibody Stability Data Support Risk Stratification Approach

To help physicians better identify the most appropriate patients for TYSABRI
treatment, Biogen Idec developed a risk stratification approach. This approach
assesses each patient’s personal benefit-risk profile based on several
factors, including anti-JCV antibody status, which was added to the TYSABRI EU
label in 2011 and the U.S. label in 2012.

An analysis of data from the longitudinal, observational U.S. study of
TYSABRI-treated patients, STRATIFY-1, demonstrates that anti-JCV antibody
status remained consistent in 90 percent of the study population when tested
every six months over an 18-month period. Approximately 38 percent of patients
tested consistently negative and 52 percent tested consistently positive.

  *Longitudinal Stability of Anti-JC Virus Antibody Status in Multiple
    Sclerosis Patients: Results of STRATIFY-1  (S30.001)  will bepresented on
    Wednesday, March 20, 2013 from 2:00 to 3:45 p.m. PDT

Early PML Detection May Improve Survival

Results from Biogen Idec’s ongoing research into PML, an infrequent but
serious brain infection, suggest that TYSABRI-treated patients who develop PML
and are asymptomatic at time of diagnosis may have improved survival and less
functional disability compared with patients who are diagnosed when
symptomatic.

This analysis includes preliminary data from four years of case reports and
evaluates outcomes in 319 TYSABRI-treated patients who developed PML, 21 of
whom had no clinical symptoms of PML but were diagnosed based on magnetic
resonance imaging (MRI) findings that were consistent with PML and spinal
fluid that was positive for the presence of JCV. It shows that survival
following PML was 100 percent in the patients without symptoms at diagnosis,
compared to 77 percent in the patients with symptoms at diagnosis. Functional
outcomes and disability were also better in the asymptomatic group one year
after PML diagnosis: the average score on the Karnofsky Performance Scale,
which measures functional outcomes, was 70 for asymptomatic patients (meaning
the person can care for him/herself), compared to 47 for those with symptoms
at diagnosis (meaning the person may be disabled and requires considerable
assistance and frequent medical care; p=0.021); and scores on the Expanded
Disability Status Scale, which measures disability, were numerically better
for asymptomatic patients (3.7 vs. 6.5 p=0.066).

  *Natalizumab–associated Progressive Multifocal Leukoencephalopathy (PML) in
    Multiple Sclerosis Patients: Survival and Functional Outcome when
    Asymptomatic at Diagnosis (P04.271) will be  available for viewing on
    Wednesday, March 20, 2013 from 7:30 a.m. – 12:00 p.m. PDT

For members of the media interested in more information and additional
resources, please visit www.biogenidec.com/us_media_corner.

About TYSABRI

TYSABRI is approved in more than 65 countries. TYSABRI is approved inthe
United Statesas a monotherapy for relapsing forms of MS, generally for
patients who have had an inadequate response to, or are unable to tolerate, an
alternative MS therapy. In theEuropean Union, it is approved for highly
active relapsing-remitting MS (RRMS) in adult patients who have failed to
respond to beta interferon or have rapidly evolving, severe RRMS.

TYSABRI has advanced the treatment of MS patients with its established
efficacy. Data from the Phase 3 AFFIRM trial, which was published in theNew
England Journal of Medicine, showed that after two years, TYSABRI treatment
led to a 68 percent relative reduction (p<0.001) in the annualized relapse
rate when compared with placebo and reduced the relative risk of disability
progression by 42-54 percent (p<0.001).

TYSABRI increases the risk of progressive multifocal leukoencephalopathy
(PML), an opportunistic viral infection of the brain which usually leads to
death or severe disability. Infection by the JC virus (JCV) is required for
the development of PML and patients who are anti-JCV antibody positive have a
higher risk of developing PML. Factors that increase the risk of PML are
presence of anti-JCV antibodies, prior immunosuppressant use, and longer
TYSABRI treatment duration. Patients who have all three risk factors have the
highest risk of developing PML. Other serious adverse events that have
occurred in TYSABRI-treated patients include hypersensitivity reactions (e.g.,
anaphylaxis) and infections, including opportunistic and other atypical
infections. Clinically significant liver injury has also been reported in the
post-marketing setting. A list of adverse events can be found in the full
TYSABRI product labeling for each country where it is approved.

TYSABRI is marketed and distributed byBiogen Idec Inc.andElan Corporation,
plc. For full prescribing information and more information about TYSABRI,
please visit www.biogenidec.com.

About Multiple Sclerosis

Multiple sclerosis (MS) is a chronic, often disabling disease that attacks the
central nervous system (CNS), which is made up of the brain, spinal cord and
optic nerves. Symptoms may be mild or severe, ranging from numbness in the
limbs to paralysis or loss of vision. The progression, severity and specific
symptoms of MS are unpredictable and vary from one person to another. MS
affects more than 2.5 million people worldwide,^1 with approximately 400,000
sufferers in the United States.^2 Relapsing-remitting MS is the most common
form of the disease, accounting for 85 percent of cases, and is characterized
by clearly defined acute attacks with full recovery or with residual deficit
upon recovery.^3

AboutBiogen Idec

Through cutting-edge science and medicine,Biogen Idecdiscovers, develops and
delivers to patients worldwide innovative therapies for the treatment of
neurodegenerative diseases, hemophilia and autoimmune disorders. Founded in
1978,Biogen Idecis the world’s oldest independent biotechnology company.
Patients worldwide benefit from its leading multiple sclerosis therapies, and
the company generates more than$5 billionin annual revenues. For product
labeling, press releases and additional information about the company, please
visit www.biogenidec.com.

About Elan

Elan is a biotechnology company, headquartered in Ireland, committed to making
a difference in the lives of patients and their families by dedicating itself
to bringing innovations in science to fill significant unmet medical needs
that continue to exist around the world. For additional information about
Elan, please visit http://www.elan.com.

Safe Harbor

This press release contains forward-looking statements, including statements
regarding risk-stratification and the therapeutic impact of TYSABRI in MS.
These forward-looking statements may be accompanied by such words as
"anticipate," "believe," "estimate," "expect," "forecast," "intend," "may,"
"plan," "will," and other words and terms of similar meaning. You should not
place undue reliance on these statements. These statements involve risks and
uncertainties that could cause actual results to differ materially from those
reflected in such statements, including the occurrence of adverse safety
events, failure to comply with government regulation and possible adverse
impact of changes in such regulation, product liability claims and the other
risks and uncertainties that are described in the Risk Factors section of our
most recent annual or quarterly report and in other reports we have filed with
the SEC. These statements are based on our current beliefs and expectations
and speak only as of the date of this press release. We do not undertake any
obligation to publicly update any forward-looking statements.

^1 Multiple Sclerosis International Federation. About MS – What is MS. Date
Accessed: March 6, 2013. http://www.msif.org/en/about_ms/what_is_ms.html

^2 Multiple Sclerosis Association of America (MSAA). About MS. Date accessed:
March 6, 2013. http://mymsaa.org/about-ms/overview/

^3 National Multiple Sclerosis Society (NMSS). For People with Relapsing MS.
Date accessed: March 6, 2013.
http://www.nationalmssociety.org/about-multiple-sclerosis/relapsing-ms/index.aspx

Contact:

MEDIA CONTACTS:
Biogen Idec
Lindsey Smith, +1 781-464-3260
or
Elan
Emer Reynolds, +353-1-709-4022
or
Jonathan Birt, +44-751-559-7858
or
INVESTOR CONTACTS:
Biogen Idec
Kia Khaleghpour, +1 781-464-2067
or
Elan
Chris Burns, +1-800-252-3526
or
David Marshall, +353-1-709-4444
 
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