Stallergenes and Shionogi Sign Exclusive Partnership Agreements for Immunotherapy Tablets in Japan

ANTONY, France, September 6, 2010 - Stallergenes S.A. has announced today the signing of exclusive
partnership agreements with Shionogi & Co., Ltd. for two sublingual allergen
immunotherapy tablet products resulting from the Stalair(R) program:
Actair(R) house dust mite tablets and Japanese cedar pollen tablets.

With 32 million respiratory allergy sufferers, there is a
strong - and as yet unmet - demand for treatment in Japan, where sublingual
allergen immunotherapy is currently not available. House dust mites and
Japanese cedar pollen are the two main causes of respiratory allergies and
the Japanese cedar allergy is a major public health concern in the country.
This partnership is the first of its kind in Japan and will bring sublingual
immunotherapy to patients suffering from severe allergic rhinitis,
inadequately controlled using symptomatic treatments (antihistamines,
corticosteroids).

The agreement covers the development, registration, promotion
and distribution of Actair(R) in Japan and Taiwan, and of the Japanese cedar
pollen tablet in Japan. The clinical development of Actair(R) will be
launched in 2011 in order to prepare the license application. For the
Japanese cedar pollen tablet, a specific development plan will be initiated
through close collaboration between the two partners, since the product is
exclusively aimed at the Japanese market.

    Stallergenes will receive:

    - an immediate upfront payment of Euros 24 million,
    - up to Euros 46 million in development and regulatory
      milestones payments,
    - as well as sales milestones.

Furthermore, Stallergenes will be entitled to royalty payments
on net sales of the products by Shionogi & Co., Ltd.

Shionogi & Co., Ltd. will be responsible for the clinical
development, registration, marketing and sales of the products covered by
this agreement in Japan. Stallergenes will be responsible for tablet
production and supply, and early-stage development.

"We are enthusiastic about the prospect of collaborating with
Stallergenes, the world leader in sublingual allergen immunotherapy, and are
very looking forward to bringing new treatment options of sublingual
immunotherapy to a huge number of allergic rhinitis patients in Japan, most
of whom suffer from allergy to house dust mite and/or Japanese cedar,"
declared Dr. Isao Teshirogi, President of Shionogi & Co., Ltd.

"We are delighted to team up with Shionogi & Co., Ltd., one of
Japan's biggest pharmaceutical companies, an R&D-based organization and a key
player in the allergy field. Shionogi & Co., Ltd., thanks to its strong
allergy franchise and its well-established presence alongside allergy
specialists, and Stallergenes will develop immunotherapy in Japan,
particularly for house dust mite allergy, in which it has recently
demonstrated its efficacy after 4 months of treatment and the persistence of
its therapeutic effect after only one year of treatment," declared Albert
Saporta, Stallergenes' Chairman and CEO.

ABOUT RESPIRATORY ALLERGY IN JAPAN

Allergic rhinitis affects 25%[1] of the population in Japan,
and asthma 6.7%[2]. House dust mites and Japanese cedar pollen are the two
main causes of respiratory allergies.

The Japanese allergy market is the 2nd biggest in the world
behind the USA. There is a very strong - and as yet unmet - demand for
allergy treatments in Japan.

ABOUT THE STALAIR(R) PROGRAM

Stalair(R) is the name of the pharmaceutical and clinical
development program for immunotherapy tablets being implemented by
Stallergenes with a view to obtaining marketing authorizations for
pharmaceutical products in Europe and in other strategic markets.

The Stalair(R) development program includes 5 immunotherapy
tablets: Oralair(R) (grass pollen), Actair(R) (house dust mites), r Bet v 1
(birch pollen recombinant allergen), ragweed pollen and Japanese cedar
pollen.

Oralair(R) is the first project resulting from this program. A
Mutual Recognition Procedure has been completed in Europe. Oralair(R), which
is already marketed in Germany, will be launched in the fall in the
Netherlands, the Czech Republic, Slovakia and Austria. Having recently
demonstrated its efficacy after 3 years of treatment (study VO53.06 conducted
in Europe), Oralair(R) has been the subject of a positive phase III trial in
adults in the United States (VO61.08).

The second project in the program is Actair(R), house dust
mite immunotherapy tablet. Having recently demonstrated Actair(R) efficacy
after 4 months of treatment and the persistence of its therapeutic effect
after only one year of treatment (study VO57.07 conducted in Europe),
Stallergenes is now preparing filing NDA in Germany. A phase III pediatric
study has been launched.

The Stalair(R) r Bet v 1 tablet (birch pollen recombinant
allergen) has been the subject of a positive phase IIb/III clinical trial
conducted in allergic rhinitis caused by birch pollen. A confirmatory phase
III study is currently being prepared with a view to EMA registration.

The ragweed pollen and Japanese cedar pollen tablets are at an
early stage of development.

Altogether, the program covers 80% of the epidemiology for all
markets.

ABOUT SHIONOGI & CO.,LTD

Headquartered in Osaka, Japan, Shionogi & Co., Ltd. is a major
research-driven pharmaceutical company dedicated to placing the highest value
on patients. Shionogi's Research and Development currently targets three
therapeutic areas: Infectious Diseases, Pain, and Metabolic Syndrome. The
Company is the originator of innovative medicines which have been
successfully delivered to millions of patients worldwide. In addition,
Shionogi is engaged in new research areas such as allergy and cancer.
Contributing to the health of patients around the world through development
in these therapeutic areas is Shionogi's primary goal. For more details,
please visit www.shionogi.co.jp.

ABOUT STALLERGENES

Stallergenes is a European biopharmaceutical company dedicated
to immunotherapy treatments for the prevention and treatment of
allergy-related respiratory diseases, such as allergic rhinoconjunctivitis,
rhinitis and asthma.

A pioneer and leader in sublingual immunotherapy treatments,
Stallergenes dedicates more than 20% of its turnover, in gross terms, to
Research and Development and is actively involved in the development of a new
therapeutic class: sublingual immunotherapy tablets. In 2009, Stallergenes
had a turnover of 193 million euros and more than 500,000 patients were
treated with Stallergenes' immunotherapy products.

    Euronext Paris (Compartment B)
    SBF 120.
    ISIN code: FR0000065674
    Reuters code: GEN.PA
    Bloomberg code: GEN.FP

    Additional information is available at www.stallergenes.com

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[1] Sakurai Y, Nakamura K, Teruya K, Shimada N, Umeda T, Tanaka H,
Yoshizawa N. Prevalence and risk factors of allergic rhinitis and cedar
pollinosis among Japanese men. Prev Med. 1998 Jul-Aug;27(4):617-22.

[2] Masoli M, Fabian D, Holt S, Beasley R; Global Initiative for Asthma
(GINA) Program. The global burden of asthma: executive summary of the GINA
Dissemination Committee report. Allergy. 2004 May;59 (5):469-78.

Contacts: Albert Saporta - Chairman and CEO, Tel.: +33-1-55-59-20-04; Christian Thiry - Financial Director, Tel: +33-1-55-59-20-95, e-mail: investorrelations at stallergenes.fr; Press relations, Lise Lemonnier - Communications Manager, Tel: +33-1-55-59-20-96, e-mail: llemonnier at stallergenes.fr;
Investor and analyst relations, Lucile de Fraguier - Pavie Finance, Tel: +33-1-42-15-04-39, e-mail: contact at pavie-finance.com