STALLERGENES: Excellent 1st Half-Year 2010 Performance

ANTONY, France, August 27, 2010 -

    - First Half-Year 2010 RESULTS

    - Excellent 1st Half-Year 2010 Performance by Stallergenes

    - Growth in France and Internationally +13%

    - Very Strong net Profit Growth +51%

    - Free Cash Flow Growth +90%

The Board of Directors' approved the 2010 half-year financial
statements at its meeting of 25 August 2010, chaired by Albert SAPORTA:

                     2010 half-year financial statements

                 In EURm                 H1 2009    09/08    H1 2010    10/09
                                              %CA   Var.%         %CA   Var.%

                  Sales                 97.6  100.0   12  110.6  100.0   13
                  Cost of goods sold   (22.5) (23.1)  13  (24.1) (21.8)   7
                  SG&A                 (37.8) (38.8)   8  (43.9) (39.7)  16
                  Profit before R&D     37.3   38.2   16   42.7   38.6   14
                  R&D costs            (21.3) (21.8)  30  (16.6) (15.0) (22)
                  R&D revenues           3.6    3.7   35    3.5    3.2   (2)
                  EBIT                  19.6   20.1    7   29.5   26.7   51
                  Net result, group     13.4   13.7   11   20.2   18.2   51
                  share
    Pour          EBITDA                24.1   24.7   12   35.6   32.2   48
    Com.          Capital expenditure    9.4    9.6   93    6.9    6.3  (26)
                  Free cash flow        14.5   14.9   45   27.6   24.9   90
                  Net cash               1.3          ns   25.0          ns
    Fi            Working capital        9.9         (16)   4.4         (55)
                  EPS, diluted          1.01EUR       11   1.50EUR       49

Sales growth and financial position

Sales grew by 13% in the first half-year. This significant
increase reflected the continuing advancement of sublingual treatments, in
particular buoyant Oralair(R) sales in Germany.

Under the combined effect of this growth and the temporary
reduction in R&D expenditure, a significant increase in earnings was achieved
in the 1st half-year 2010. Overall, the profit before R&D rose moderately in
relative value and represented 38.6% of sales, compared to 38.2% in the 1st
half-year 2009. R&D expenditure fell very significantly by 22% in the first
half-year and went from 21.8% of sales in 2009 to 15.0% this year. This
decline was due to a timing difference between the end of the clinical
studies in progress (and particularly the Oralair(R) study in the US) and the
start of new studies. Operating profit rose by 51% to EUR 29.5 million. The
net diluted earnings per share grew by 49% to EUR 1.50.

EBITDA grew by 48% to EUR 35.6 million. Investments
temporarily fell by 26% over the half-year to EUR 6.9 million. As a result,
and also due to stable working capital requirements, free cash flow recorded
a significant 90% increase to EUR 27.6 million.

At 30 June, net cash resources grew from EUR 1.3 million in
2009 to EUR 25.0 million in 2010.

The half-year financial report can be downloaded from the website:
www.stallergenes.com

At its meeting of 25 August 2010, the Board of Directors
authorised the implementation of the share buyback programme approved by the
Annual General Meeting of 28 May 2010, which will not exceed EUR 10 million
and will more particularly be used to cover stock options and
performance-based share payments.

Significant recent transactions and events

The positive clinical results achieved over the first
half-year, in particular for Oralair(R) and Actair(R) lead us to consider our
international expansion with confidence. These results are particularly
encouraging in our drive to enter into strategic partnerships.

Oralair(R), which is already marketed in Germany, will be
launched in the autumn in the Netherlands, the Czech Republic, Slovakia and
Austria. The market access process is ongoing in Southern European countries.
In France more specifically, talks have been initiated with the "Commission
de Transparence", which should issue a public opinion by the end of the year.

R&D expenditure will recover in the second half-year but the
2010 total will not exceed the 2009 level in absolute value. Against this
background, and considering projected sales growth in excess of 10%, the
Group expects a significant increase in its full-year operating margin.

The recovery in investment in the second half should only have
a marginal effect on the generation of free cash flow, which will be
significantly greater in the full year 2010 than in 2009.

The presentation of the 2010 half-year results and outlook for the Group
will take place on 27 August 2010 at 11.30 am (CET) at Hotel Le Bristol, 112,
rue du Faubourg Saint-Honore, 75008 Paris, France. This meeting will be
webcast and will be available both in French and English on our website:
finance.stallergenes.com from 3 pm.

ABOUT STALLERGENES

Stallergenes is a European biopharmaceutical laboratory
specialising in treatments by immunotherapy for the prevention and treatment
of allergy-related respiratory conditions, such as rhino conjunctivitis,
rhinitis and allergic asthma. A pioneer and a leader in immunotherapy
treatments by sublingual administration, Stallergenes dedicated more than 20%
(gross) of its sales in 2009 to its Research and Development activities,
which are primarily directed at developing a new therapeutic range enabling
the provision of immunotherapy treatments by sublingual tablets. Stallergenes
achieved 2009 sales of EUR 193 million, with over 500,000 patients treated
with Stallergenes products.

For further information, please visit our website:
www.stallergenes.com

Contacts: Albert Saporta, Chairman and CEO, Tel. +33-1-55-59-20-04, Christian Thiry, Chief Financial Officer, Tel. +33-1-55-59-20-95, e-mail: investorrelations 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; Stallergenes Press Relations, Lise Lemonnier, Communication Officer, Tel. + 33-1-55-59-20-96, e-mail: llemonnier at stallergenes.fr