US and EU Regulatory Authorities Accept PLEGRIDY™ (peginterferon beta-1a) Marketing Applications for Review

  US and EU Regulatory Authorities Accept PLEGRIDY™ (peginterferon beta-1a)
  Marketing Applications for Review

Business Wire

WESTON, Mass. -- July 19, 2013

Today Biogen Idec (NASDAQ: BIIB) announced that U.S. and EU regulatory
authorities have accepted the marketing applications for the review of
PLEGRIDY™ (peginterferon beta-1a), the company’s pegylated subcutaneous
injectable candidate for relapsing forms of multiple sclerosis (MS). The U.S.
Food and Drug Administration(FDA) has accepted Biogen Idec’s Biologics
License Application (BLA) for marketing approval of PLEGRIDY inthe United
Statesand granted the company a standard review timeline. The Marketing
Authorisation Application (MAA) of PLEGRIDY for review in the European Union
was also validated by the European Medicines Agency.

The regulatory applications included positive one-year results from the
two-year global Phase 3 ADVANCE study. The data demonstrated that PLEGRIDY met
all primary and secondary endpoints by significantly reducing disease activity
including relapses, disability progression and brain lesions compared to
placebo, and showed favorable safety and tolerability profiles at one year.

“We expect that interferons will remain an important and widely used option
for patients with MS. At one-year, PLEGRIDY demonstrated significant
reductions in relapses and disability progression, as well as a robust impact
on several MRI endpoints,” said Douglas E. Williams, Ph.D., Biogen Idec’s
executive vice president of Research and Development. “PLEGRIDY, if approved,
could offer a less frequent dosing schedule, a favorable safety profile, and
the potential to become the preferred interferon treatment.”

About PLEGRIDY

PLEGRIDY is a new molecular entity in which interferon beta-1a is pegylated to
extend its half-life and prolong its exposure in the body. PLEGRIDY is a
member of the interferon class of treatments, which is often used as a
first-line treatment for MS.

About ADVANCE

The two-year Phase 3 ADVANCE clinical trial is a global, multi-center,
randomized, double-blind, parallel-group, placebo-controlled study designed to
evaluate the efficacy and safety of PLEGRIDY in 1,516 patients with
relapsing-remitting MS.

The study investigates two dose regimens of PLEGRIDY, 125 mcg administered
subcutaneously every two weeks or every four weeks compared to placebo. The
analysis for all primary and secondary efficacy endpoints occurred at one
year. After the first year, patients on placebo are re-randomized to one of
the PLEGRIDY arms for the duration of the second year of the study. After
completing two years in the ADVANCE study, patients have the option of
enrolling in an open-label extension study called ATTAIN and will be followed
for up to four years.

About Biogen Idec

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

Safe Harbor

This press release includes forward-looking statements, including statements
about the potential of PLEGRIDY, including the dosage and related therapeutic
effects of PLEGRIDY 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. Drug development and
commercialization involve a high degree of risk. Factors which could cause
actual results to differ materially from our current expectations include the
risk that unexpected concerns may arise from additional data or analysis,
regulatory authorities may require additional information or further studies,
or may fail to approve or may delay approval of our drug candidates, or we may
encounter other unexpected hurdles. For more detailed information on the risks
and uncertainties associated with our drug development and commercialization
activities, please review the Risk Factors section of our most recent annual
or quarterly report filed with the Securities and Exchange Commission. 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.

Contact:

MEDIA CONTACT:
Biogen Idec
Ligia Del Bianco, +1 781-464-3283
or
INVESTOR CONTACT:
Biogen Idec
Carlo Tanzi, PhD, +1 781-464-2442