Stallergenes: Positive Results for Oralair(R) Phase III Trial in the USA

ANTONY, France, April 19, 2010 - Stallergenes S.A. today announced the first results of a phase
III clinical trial (VO61.08) conducted in the USA on its sublingual grass
pollen immunotherapy tablet, Oralair(R).

This phase III study is the first clinical study in the USA to
be conducted by Stallergenes as part of the Oralair(R) clinical development
which already encompassed 4 phase III clinical trials conducted in Europe.
This development program has so far included over 2,300 patients. This study
is pivotal in the perspective of a market authorization application for
Oralair(R) in the USA with an adult indication (BLA[1]).

The VO61.08 study is a randomized, double-blind,
placebo-controlled, phase III trial. It included 473 adult patients, aged 18
to 65 years, suffering from grass pollen-induced rhinoconjunctivitis, in 51
centers in the United States. The patients were divided into two arms: one
group was treated with Oralair(R) and the other with a placebo. The primary
endpoint was the reduction of the "combined score", taking into account
symptoms and rescue drugs.

The study achieved its objective on the primary endpoint: the
reduction of the combined score obtained by Oralair(R) compared to the
placebo is statistically very significant and of a similar magnitude to the
results of European studies. The product was very well tolerated.

"We are proud to have conducted this study in the USA and very
satisfied with the results obtained which confirm the high level of evidence
in support of Oralair(R)" commented Albert Saporta, Chairman and CEO of
Stallergenes. "We have passed an important milestone in our strategy for the
US market and are actively preparing the registration file with a view to
filing a Market Authorization application in early 2011."

About Oralair(R)

The Oralair(R) active substance consists of five purified and
calibrated pollen extracts corresponding to the epidemiological
characteristics of patient exposure in Europe: perennial rye grass (Lolium
perenne), meadow grass (Poa pratensis), timothy grass (Phleum pratense),
cocksfoot (Dactylis glomerata) and sweet vernal grass (Anthoxanthum
odoratum).

From the outset, its clinical development has taken into
account the benefit to patients: proven efficacy, safety, ease of use,
compliance, and cost-containment through a pre- and coseasonal protocol (the
treatment is taken for four months prior to the pollen season and then
throughout it, for three consecutive seasons) rather than a perennial
protocol.

The clinical development program for Oralair(R) is continuing.
Stallergenes has recently announced the positive 3-year results of a phase
III clinical trial (VO53.06) intended to assess the long-term or sustained
effect of Oralair(R) along with maintenance of the therapeutic benefit after
treatment discontinuation (disease-modifier effect). This study is the first
ever pivotal study designed to measure this dual effect from the outset. It
will continue for 2 years without treatment so that the disease-modifier
effect can be fully assessed.

About the Stalair(R) Program

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

Oralair(R) is the first project resulting from this program. A
Mutual Recognition Procedure has been completed in Europe.

A positive phase IIb/III study was completed for the dust mite
immunotherapy tablet, Actair(R) in allergic rhinitis in adults during the
first half of 2009. A pediatric phase III study has been launched.

The Bet v 1 tablet (birch pollen recombinant) 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 other allergens concerned by the program are ragweed for
the North American market and Japanese cedar pollen for the Japanese market.
Altogether, the program covers 80% of the epidemiology for all markets.

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 over 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, the company had
a turnover of 193 million euros and more than 500,000 patients were treated
with Stallergenes 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] BLA: Biologics License Application

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