Shire and GlaxoSmithKline Enter Agreement to Co-promote VYVANSE(R) (lisdexamfetamine dimesylate) CII for the Treatment of Adults With ADHD

PHILADELPHIA - Co-promotion Agreement Will Double the VYVANSE Sales Effort Across the
Country

Shire plc (LSE: SHP, NASDAQ: SHPGY), the global specialty
biopharmaceutical company, today announced a co-promotion agreement with
GlaxoSmithKline plc (NYSE: GSK) for VYVANSE(R) (lisdexamfetamine dimesylate)
capsules CII with the aim of improving recognition and treatment of ADHD in
adults. This three year agreement covers the United States and will more than
double the reach and frequency of the current sales effort for VYVANSE by
adding over 600 sales representatives from GSK who call on specialists and
primary care physicians. Shire currently has nearly 600 representatives
promoting VYVANSE, primarily to pediatricians and psychiatrists.

“Shire is an established leader in developing and commercializing
medicines that help patients with ADHD manage their symptoms,” said Michael
Cola, President of Shire’s Specialty Pharmaceuticals business. “Since its
launch in 2007, VYVANSE has become the fastest-growing, once-daily,
prescription ADHD treatment in the United States and today has achieved
nearly 12 percent of the prescription ADHD market. Increased diagnosis and
treatment of adults with ADHD is a significant driver of growth in this
category, and by collaborating with GSK, which has two of the most
accomplished CNS and Primary Care sales teams in the industry, VYVANSE will
be introduced to over 70,000 new physicians. We believe Shire, GSK and adults
with ADHD will benefit from this agreement.”

“GSK has been active in discovering and developing medicines to treat
psychiatric disorders for decades, and neuroscience is one of the company’s
key therapeutic categories,” said Deirdre Connelly, President,
GlaxoSmithKline North American Pharmaceuticals. “Our professional sales
representatives are well positioned to provide physicians with information on
the treatment of adult ADHD with VYVANSE and we look forward to helping meet
the needs of adult patients with ADHD.”

The GSK sales force is expected to begin promoting VYVANSE to physicians
in May 2009. The agreement is based on profit-sharing above an agreed-upon
baseline figure.

VYVANSE, which was introduced in the United States in July 2007 for the
treatment of ADHD in children aged 6 to 12 years and approved in April 2008
to treat ADHD in adults, is currently available in six dosage strengths of 20
mg, 30 mg, 40 mg, 50 mg, 60 mg, and 70 mg. To date, more than 4 million
VYVANSE prescriptions have been filled, bringing the current US market share
to nearly 12 percent based on weekly branded prescription volume.
Additionally, VYVANSE formulary coverage has been positive, with nine of
Shire’s top 11 managed care organizations covering the product in a preferred
formulary position.

VYVANSE is a therapeutically inactive prodrug, in which d-amphetamine is
covalently bonded to l-lysine, and after oral ingestion it is converted to
pharmacologically active d-amphetamine. The conversion of VYVANSE to
d-amphetamine is not affected by gastrointestinal pH and is unlikely to be
affected by alterations in GI transit times.

Additional information about VYVANSE and Full Prescribing Information,
including Medication Guide, are available at www.vyvanse.com.

About VYVANSE

VYVANSE is indicated for the treatment of ADHD. Efficacy based on two
controlled trials in children aged 6 to 12 and one controlled trial in
adults.

Tell the doctor about any heart conditions, including structural
abnormalities, that you, your child, or a family member, may have. Inform the
doctor immediately if you or your child develops symptoms that suggest heart
problems, such as chest pain or fainting.

VYVANSE should not be taken if you or your child has advanced disease of
the blood vessels (arteriosclerosis); symptomatic heart disease; moderate to
severe high blood pressure; overactive thyroid gland (hyperthyroidism); known
allergy or unusual reactions to drugs called sympathomimetic amines (for
example, pseudoephedrine); seizures; glaucoma; a history of problems with
alcohol or drugs; agitated states; taken a monoamine oxidase inhibitor (MAOI)
within the last 14 days.

Tell the doctor before taking VYVANSE if you or your child is being
treated for or has symptoms of depression (sadness, worthlessness, or
hopelessness) or bipolar disorder; has abnormal thought or visions, hears
abnormal sounds, or has been diagnosed with psychosis; has had seizures or
abnormal EEGs; has or has had high blood pressure; exhibits aggressive
behavior or hostility. Tell the doctor immediately if you or your child
develops any of these conditions or symptoms while taking VYVANSE.

Abuse of amphetamines may lead to dependence. Misuse of amphetamine may
cause sudden death and serious cardiovascular adverse events. These events
have also been reported rarely with amphetamine use.

Talk to your health care provider if your child experiences slowing of
growth (height and weight). Children should have their height and weight
checked periodically while taking VYVANSE. Your healthcare provider may stop
VYVANSE treatment if a problem is found during these check-ups.

VYVANSE was generally well tolerated in clinical studies. The most common
side effects reported in studies of VYVANSE were: children - decreased
appetite, difficulty falling asleep, stomachache, and irritability; adult -
decreased appetite, difficulty falling asleep, and dry mouth.

Aggression, new abnormal thoughts/behaviors, mania, growth suppression,
worsening of motion or verbal tics, and Tourette’s syndrome have been
associated with use of drugs of this type. Tell the doctor if you or your
child has blurred vision while taking VYVANSE.

About ADHD

ADHD is one of the most common psychiatric disorders in children and
adolescents. Worldwide prevalence of ADHD is estimated at 5.3 percent (with
large variability), according to a comprehensive systematic review of this
topic published in 2007 in the American Journal of Psychiatry. In the United
States, approximately 7.8 percent of all school-aged children, or about 4.4
million children aged 4 to 17 years, have been diagnosed with ADHD at some
point in their lives, according to the U.S. Centers for Disease Control and
Prevention (CDC). The disorder is also estimated to affect 4.4 percent of US
adults aged 18-44 based on results from the National Comorbidity Survey
Replication. When this percentage is extrapolated to the full US population,
approximately 9.8 million adults are believed to have ADHD.

ADHD is a psychiatric behavioral disorder that manifests as a persistent
pattern of inattention and/or hyperactivity-impulsivity that is more frequent
and severe than is typically observed in individuals at a comparable level of
development. The specific etiology of ADHD is unknown and there is no single
diagnostic test for this syndrome. Adequate diagnosis requires the use of
medical and special psychological, educational and social resources,
utilizing diagnostic criteria such as Diagnostic and Statistical
Manual(TM)-IV (DSM-IV) or International Classification of Diseases 10
(ICD-10).

Although there is no “cure” for ADHD, there are accepted treatments that
specifically target its symptoms. Standard treatments include educational
approaches, psychological, or behavioral modification, and medication.

Shire Plc

Shire’s strategic goal is to become the leading specialty
biopharmaceutical company that focuses on meeting the needs of the specialist
physician. Shire focuses its business on attention deficit hyperactivity
disorder (ADHD), human genetic therapies (HGT) and gastrointestinal (GI)
diseases as well as opportunities in other therapeutic areas to the extent
they arise through acquisitions. Shire’s in-licensing, merger and acquisition
efforts are focused on products in specialist markets with strong
intellectual property protection and global rights. Shire believes that a
carefully selected and balanced portfolio of products with strategically
aligned and relatively small-scale sales forces will deliver strong results.

For further information on Shire, please visit the Company’s website:
www.shire.com.

THE “SAFE HARBOR” STATEMENT UNDER THE PRIVATE SECURITIES LITIGATION
REFORM ACT OF 1995

Statements included herein that are not historical facts are
forward-looking statements. Such forward-looking statements involve a number
of risks and uncertainties and are subject to change at any time. In the
event such risks or uncertainties materialize, the Company’s results could be
materially adversely affected. The risks and uncertainties include, but are
not limited to, risks associated with: the inherent uncertainty of research,
development, approval, reimbursement, manufacturing and commercialization of
the Company’s Specialty Pharmaceutical and Human Genetic Therapies products,
as well as the ability to secure and integrate new products for
commercialization and/or development; government regulation of the Company’s
products; the Company’s ability to manufacture its products in sufficient
quantities to meet demand; the impact of competitive therapies on the
Company’s products; the Company’s ability to register, maintain and enforce
patents and other intellectual property rights relating to its products; the
Company’s ability to obtain and maintain government and other third-party
reimbursement for its products; and other risks and uncertainties detailed
from time to time in the Company’s filings with the Securities and Exchange
Commission.

GlaxoSmithKline

GlaxoSmithKline - one of the world’s leading research-based
pharmaceutical and healthcare companies - is committed to improving the
quality of human life by enabling people to do more, feel better and live
longer. For further information please visit www.gsk.com

For further information please contact:

Investor Relations Clea Rosenfeld (Rest of the World) +44-1256-894-160
Eric Rojas (North America) +1-617-551-9715
Media Jessica Mann (Rest of the World) +44-1256-894-280
Matthew Cabrey (Specialty Pharma) +1-484-595-8248

Source: Shire Plc

Investor Relations: Clea Rosenfeld (Rest of the World) +44-1256-894-160; Eric Rojas (North America), +1-617-551-9715; Media: Jessica Mann (Rest of the World), +44-1256-894-280; Matthew Cabrey (Specialty Pharma), +1-484-595-8248