Stallergenes: Staloral(R) Mites 300 Clinical Study in China: Efficacy is Demonstrated

ANTONY, France, June 21, 2010 - Stallergenes S.A. announces the results of a phase III
clinical trial (VO55.06) conducted in China aimed at assessing the efficacy
and safety of sublingual immunotherapy (Staloral(R) mites 300) in adult
patients suffering from asthma triggered by house dust mites.

Study VO55.06 is a phase III randomized, double-blind,
placebo-controlled study conducted over a period of 15 months in 14 centers
located in China's main cities. After an observation period of 3 months, 484
adult patients with mild to moderate asthma well controlled under inhaled
corticosteroid therapy were divided into two groups, one treated with
Staloral(R) 300 and one given a placebo for a period of 12 months. Throughout
the duration of the study, the patients received inhaled corticosteroid
therapy at gradually reduced dosages. The patients were assessed on the basis
of the level of asthma control as defined by GINA(1).

Staloral(R) 300 demonstrated statistically significant
efficacy versus placebo for the control of asthma, on the basis of the
following criteria: "well-controlled asthma" and "totally controlled asthma"
in GINA 3 patients (moderate asthma stabilized with corticosteroids by
bronchial route). In this population, the probability of a patient having
his/her asthma well or totally controlled is more than twice as high with
Staloral(R) 300 as it is in the placebo group (odds ratios and 95% confidence
intervals of 2.10 [1.01; 4.36] and 2.43 [1.28; 4.61] respectively).

The treatment was well tolerated. There were no pulmonary side
effects related to worsening of asthma or deterioration in lung function.

"We are very pleased with the outstanding outcomes of this
large-scale study, conducted in China with a solid methodology. They pave the
way for better asthma management and improved quality of life for patients",
emphasizes Prof. YIN Jia, Principal Coordinator and Head of the Allergy
Department at the Peking Union Medical College Hospital and President of the
Chinese Allergology Society.

"For the first time, the efficacy of sublingual allergen
immunotherapy has been demonstrated in the stabilization of allergic asthma
due to mites in adults through a large-scale clinical trial. This very good
outcome will enable us to apply for registration of Staloral(R) mites 300 in
China in the near future. Obviously, these results will lead the clinical
development program for Actair(R), our sublingual immunotherapy tablet for
the treatment of allergic rhinitis triggered by dust mites, to also focus on
the treatment of asthma in patients allergic to mites", adds Albert Saporta,
Chairman and CEO of Stallergenes.

ABOUT ALLERGIC ASTHMA

Asthma is a chronic inflammatory disease of the airways, very
often linked to allergic rhinitis: 80% of allergic asthma sufferers also have
allergic rhinitis and 40% of patients with untreated rhinitis go on to
develop asthma.

Particularly common in children, asthma is a major public
health problem. The frequency of the condition varies from one country to
another; in the great majority of developed countries, between 5 and 15% of
the adult population and 3 to 7% of the pediatric population are affected.
The prevalence of asthma has been gradually increasing over the last 20 years
in industrialized countries, at a rate of around 5% per year.

ABOUT RESPIRATORY ALLERGY IN CHINA

The prevalence of respiratory allergy in China ranges from 10
to more than 20% of the population. The most commonly reported related
conditions are asthma (9.2%), rhinosinusitis (13.3%) and atopic dermatitis
(16.4%). In urban populations, 2 out of 3 allergic rhinitis sufferers are
consulting a physician, and 40% of these will have allergen tests.

China is one of the countries offering the greatest potential
for economic growth globally in the medium term. It is among the top ten
pharmaceutical markets in the world and is well on the way to entering the
top 5 by 2011(1).

ABOUT STALORAL(R) 300

Staloral(R) 300 is a sublingual solution of allergen extracts
for allergen immunotherapy. It is indicated in the treatment of seasonal or
perennial allergic rhinitis, rhinoconjunctivitis and allergic mild to
moderate asthma in adults and children over the age of 5 years. Prescribed by
allergy specialists, Staloral(R) 300 is particularly aimed at patients
suffering from severe allergic diseases inadequately controlled despite the
use of symptomatic treatments.

ABOUT ACTAIR(R)

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

Actairâ was the subject of a positive IIb/III trial in
allergic rhinitis in adults in the first half of 2009. A phase III pediatric
trial has been launched.

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. Stallergenes is the seventh-ranked French pharmaceutical
company. A pioneer and leader in sublingual immunotherapy treatments,
Stallergenes devotes 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

(1)GINA : Global Initiative on Asthma. GINA, in collaboration with the
National Heart, Lung, and Blood Institute, National Institute of Health, USA,
and the World Health Organization, is elaborating and updating the worldwide
consensus on asthma management. GINA has defined 4 levels of asthma from mild
(1) up to severe (4).

(2)IMS Health, Market Prognosis, March 2009 classification in constant
US$

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 - Communication 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