Nine Abstracts Relating to Cinryze(R) (C1 Esterase Inhibitor [human]) Data Presented at 30th Congress of the European Academy of Allergy and Clinical Immunology (EAACI)

ISTANBUL, June 13, 2011 -

ViroPharma Incorporated (NASDAQ: VPHM) today announced that data relating
to Cinryze(R) (C1 esterase inhibitor [human]) from nine accepted abstracts
were presented as poster presentations at the 30th Congress of the European
Academy of Allergy and Clinical Immunology (EAACI), June 11 through 15, in
Istanbul, Turkey. Of the nine posters, two contain new data and seven contain
data previously presented at the 2010 International Scientific Conference of
the World Allergy Organization (WAO), the 2010 Annual Meeting of the American
College of Allergy, Asthma & Immunology (ACAAI), and the 2011 American
Academy of Allergy Asthma & Immunology (AAAAI) Annual Meeting.

Cinryze is the first and only U.S. FDA-approved C1 esterase inhibitor
therapy indicated for routine prophylaxis against angioedema attacks in
adolescent and adult patients with hereditary angioedema (HAE), a rare,
debilitating and potentially fatal disease. Currently, Cinryze is available
only in the United States, and is not approved to treat acute angioedema
attacks, for children with HAE, or for pre-procedural administration.

In Europe, the Committee for Medicinal Products for Human Use (CHMP) has
adopted a positive opinion for Cinryze for treatment and pre-procedural
prevention of angioedema attacks in adults and adolescents with hereditary
angioedema (HAE), and routine prevention of angioedema attacks in adults and
adolescents with severe and recurrent attacks of hereditary angioedema (HAE),
who are intolerant to or insufficiently protected by oral prevention
treatments or patients who are inadequately managed with repeated acute
treatment.

HAE is a rare, debilitating and potentially life-threatening genetic
disorder that affects at least 10,000 people in Europe. HAE is a variable
disease due to a deficiency of C1 inhibitor, a human plasma protein that
prevents swelling. Patients can experience unpredictable, recurrent,
disabling and potentially deadly attacks of swelling that can affect the
larynx, abdomen, face, extremities and genitourinary tract. If approved,
Cinryze would be the first C1 esterase inhibitor product approved for
preventative therapy of HAE across all of Europe.

“As we move closer toward providing Cinryze for HAE patients in Europe,
it is important that we expand the awareness among the medical community of
the available data on clinical experience with this important drug for
patients with hereditary angioedema,” commented Mark Sampson, MD,
ViroPharma’s vice president of clinical development and medical affairs,
Europe. “HAE is a variable disease that can be seen by various physician
specialties, and Cinryze is poised to be a comprehensive management option
for European physicians and patients.”

EAACI Poster Presentations (new data)

In a poster entitled, ‘Use of Nanofiltered C1 Esterase Inhibitor (Human)
[C1 INH-nf] for the Treatment of Gastrointestinal (GI) Attacks in Subjects
with Hereditary Angioedema (HAE),’ Dr. William Lumry, M.D., of the University
of Texas Southwestern Medical School in Dallas, Texas discussed the potential
for Cinryze to treat GI-localized HAE attacks. These data were compiled from
an open-label, multicenter (29 sites) study that enrolled 113 subjects with a
diagnosis of HAE. Gastrointestinal attacks represented the largest proportion
(351/598, 59 percent) of HAE attacks in this study. Subjects received
treatment with C1 INH-nf 1000U IV and could receive a second dose of C1
INH-nf 1000U if their symptoms had not improved by 60 minutes. The results
cited on the poster included the following:

    - Seventy-seven subjects experienced a total of 351 GI attacks, with 97
      percent (339/351) achieving relief within 4 hours after C1 INH-nf
      administration; median time to beginning of relief was 30 minutes. This
      response time was comparable to the overall median response time for
      all attacks at all anatomic locations in this study (30 minutes).
    - Among subjects treated for greater than one GI attack, the efficacy of
      C1 INH-nf did not diminish with subsequent repeated administration.
    - Of the 113 subjects enrolled, the most common (three to five percent of
      subjects) adverse events were sinusitis, nasopharyngitis, streptococcal
      pharyngitis, HAE, constipation, cough, rash, and bronchitis.
    - There were no hypersensitivity reactions, including anaphylaxis,
      related to C1 INH-nf. HBV, HCV, and HIV testing revealed no evidence of
      viral transmission. There was no evidence of development of clinically
      relevant anti-C1 INH antibodies.

In a poster entitled, ‘Use of Nanofiltered C1 Esterase Inhibitor (Human)
[C1 INH-nf] for the Treatment of Extremity and Facial Attacks in Subjects
with Hereditary Angioedema (HAE),’ Dr. Marc Riedl, M.D., of the University of
California, Los Angeles, David Geffen School of Medicine presented the
experience of 51 subjects who received C1 INH-nf to treat 156 facial and
extremity attacks of HAE. Cutaneous attacks of the extremity (N=86) and face
(N=70) represented the second largest proportion (156/598, 26 percent) of HAE
attacks in this study. Subjects received treatment with C1 INH-nf 1000U IV
and could receive a second dose of C1 INH-nf 1000U if their symptoms had not
improved by 60 minutes. The results cited on the poster included the
following:

    - Ninety six percent of these attacks (149/156) achieved relief within 4
      hours after C1 INH-nf administration; median time to beginning of
      relief was 30 minutes. This response time was comparable to the overall
      median response time for all attacks at all anatomic locations in this
      study (30 minutes).
    - The efficacy of C1 INH-nf did not diminish with subsequent repeated
      administration. Of the 113 subjects enrolled, the most common (three to
      five percent of subjects) adverse events were sinusitis,
      nasopharyngitis, streptococcal pharyngitis, HAE, constipation, cough,
      rash, and bronchitis.
    - There were no hypersensitivity reactions, including anaphylaxis,
      related to nf-C1 INH. HBV, HCV, and HIV testing revealed no evidence of
      viral transmission. There was no evidence of development of clinically
      relevant anti-C1 INH antibodies.

Additional EAACI Poster Presentations (previously presented data)

    1. Open-Label Use of Nanofiltered C1 Esterase Inhibitor (Human) (C1
       INH-nf) for the Treatment of Hereditary Angioedema (HAE) Attacks
    2. Open-Label Use of Nanofiltered C1 Esterase Inhibitor (Human) (C1
       INH-nf) for the Prophylaxis of Hereditary Angioedema (HAE) Attacks
    3. Pre-procedure Administration of C1 Esterase Inhibitor (Human) (C1
       INH-nf) for the Prevention of Hereditary Angioedema (HAE) Attacks
       after Medical, Dental, or Surgical Procedures
    4. Site of Care of Nanofiltered C1 Esterase Inhibitor (Human) (C1 INH-nf)
       in Patients With Hereditary Angioedema (HAE)
    5. Safety and Efficacy of Nanofiltered C1 Esterase Inhibitor (Human) (C1
       INH-nf) for the Treatment of Laryngeal Attacks in Subjects with
       Hereditary Angioedema (HAE)
    6. Open-Label Use of Nanofiltered C1 Esterase Inhibitor (Human) (C1
       INH-nf) for Treatment of Acute Attacks of Hereditary Angioedema (HAE)
       in Pediatric Subjects
    7. Open-Label Use of Nanofiltered C1 Esterase Inhibitor (Human) (C1
       INH-nf) for Treatment or Prophylaxis of Acute Attacks of Hereditary
       Angioedema (HAE) in Pregnant Subjects

EAACI Symposium

ViroPharma is also sponsoring a scientific symposium on Monday June 13th
at 13.30 hrs (1:30 PM) local time entitled, “New Strategies for Preventing
Hereditary Angioedema (HAE) Attacks.” This symposium, sponsored by ViroPharma
through an independent educational grant, will be webcast live, and all
content will be available for three additional months. It can be accessed at
the following URL: go.podia.net/viropharma_istanbul_symposium_2011

About Cinryze(R) (C1 esterase inhibitor [human])

Cinryze is a highly purified, pasteurized and nanofiltered plasma-derived
C1 esterase inhibitor product that is approved by U.S. FDA for routine
prophylaxis against angioedema attacks in adolescent and adult patients with
HAE. In Europe, on March 17, 2011, the CHMP adopted a positive opinion for
Cinryze for treatment and pre-procedure prevention of angioedema attacks in
adults and adolescents with hereditary angioedema (HAE), and routine
prevention of angioedema attacks in adults and adolescents with severe and
recurrent attacks of hereditary angioedema (HAE), who are intolerant to or
insufficiently protected by oral prevention treatments or patients who are
inadequately managed with repeated acute treatment. The CHMP positive opinion
forms the scientific basis for the European Commission to issue a binding
decision for a Centralized Marketing Authorization, which is expected in the
second quarter of 2011.

Severe hypersensitivity reactions to Cinryze may occur. Thrombotic events
have occurred in patients receiving Cinryze for routine prophylaxis, and in
patients receiving off-label high dose C1 inhibitor therapy. Monitor patients
with known risk factors for thrombotic events. With any blood or plasma
derived product, there may be a risk of transmission of infectious agents,
e.g. viruses and, theoretically, the CJD agent. The risk has been reduced by
screening donors for prior exposure to certain virus infections and by
manufacturing steps to reduce the risk of viral transmission including
pasteurization and nanofiltration. The most common adverse reactions observed
have been upper respiratory infection, sinusitis, rash and headache. No
drug-related serious adverse events (SAEs) have been observed in clinical
trials.

Cinryze is approved for intravenous use only.

About Hereditary Angioedema (HAE)

HAE is a rare, severely debilitating, life-threatening genetic disorder
caused by a deficiency of C1 inhibitor, a human plasma protein. This
condition is the result of a defect in the gene controlling the synthesis of
C1 inhibitor. C1 inhibitor maintains the natural regulation of the contact,
complement, and fibrinolytic systems, that when left unregulated, can
initiate or perpetuate an attack by consuming the already low levels of
endogenous C1 inhibitor in HAE patients. Patients with C1 inhibitor
deficiency experience recurrent, unpredictable, debilitating, and potentially
life threatening attacks of inflammation affecting the larynx, abdomen, face,
extremities and urogenital tract. Patients with HAE experience approximately
20 to 100 days of incapacitation per year. There are estimated to be at least
6,500 people with HAE in the United States, and at least 10,000 people across
Europe.

For more information on HAE, visit the U.S. HAE Association’s website at:
www.haea.org or the HAEi (International Patient Organization for C1
Inhibitor Deficiencies) at www.haei.org.

About ViroPharma Incorporated

ViroPharma Incorporated is an international biopharmaceutical company
committed to developing and commercializing novel solutions for physician
specialists to address unmet medical needs of patients living with diseases
that have few if any clinical therapeutic options, including C1 esterase
inhibitor deficiency, pediatric epilepsy and C. difficile infection (CDI).
Our goal is to provide rewarding careers to employees, to create new
standards of care in the way serious diseases are treated, and to build
international partnerships with the patients, advocates, and health care
professionals we serve. ViroPharma’s commercial products address diseases
including hereditary angioedema (HAE) and CDI; for prescribing information on
our products, please download the package inserts at
www.viropharma.com/Products.aspx.

ViroPharma routinely posts information, including press releases, which
may be important to investors in the investor relations and media sections of
our company’s website, www.viropharma.com/. The company encourages
investors to consult these sections for more information on ViroPharma and
our business

Forward Looking Statements

Certain statements in this press release contain forward-looking
statements that involve a number of risks and uncertainties. Forward-looking
statements provide our current expectations or forecasts of future events.
There can be no assurance that that the data presented during the 30th
Congress of the European Academy of Allergy and Clinical Immunology (EAACI)
regarding Cinryze is predictive of how Cinryze will perform in commercial
usage. Cinryze is currently available only in the United States. Cinryze is
not approved in the U.S. for acute treatment of attack, children with HAE or
for pre-procedure prophylaxis. We cannot assure that current or future
studies with Cinryze in the patient populations described in the EAACI
presentations will demonstrate the same or similar safety and efficacy
profile of Cinryze as described in the data presented during the 2011 EAACI.
These factors, and other factors, including, but not limited to those
described in our annual report on Form 10-K for the year ended December 31,
2010 and 10-Q for the quarter ended March 31, 2011 filed with the Securities
and Exchange Commission, could cause future results to differ materially from
the expectations expressed in this press release. The forward-looking
statements contained in this press release are made as of the date hereof and
may become outdated over time. ViroPharma does not assume any responsibility
for updating any forward-looking statements. These forward looking statements
should not be relied upon as representing our assessments as of any date
subsequent to the date of this press release.

ViroPharma Incorporated: Kristina M. Broadbelt (Media), Assistant Director, PR & Advocacy, +1-610-321-2358, or Robert A. Doody Jr. (Investors), Assistant Director, Investor Relations, +1-610-321-6290