STALLERGENES : Significant Growth : Q3 2010 + 10% and +12% Over the First 9 Months / Shionogi Partnership: First EUR24 Million Instalment

ANTONY, France, October 14, 2010 -

    EUR million              2009         09-Aug     2010         10-Sep
                             EURm  %Sales  Var.%     EURm  %Sales  Var.%

    Southern Europe(1)         26      68      9     29.2      70     12
    Other EU countries(2)    10.3      27     20     10.6      25      3
    Other markets             1.9       5      8      2.2       5     15

    SLIT                     30.5      79     16     34.7      83     14
    SCIT                      6.3      17     -2      5.9      14     -6
    Other products            1.4       4      0      1.3       3     -8

    Total Q3 sales           38.2     100     12       42     100     10
    Southern Europe(1)       96.3      71      9    108.4      71     13
    Other EU countries(2)    34.4      25     27       38      25     10
    Other markets             5.2       4     -5      6.2       4     21

    SLIT                    111.6      82     14      129      85     16
    SCIT                     19.1      14      2     18.4      12     -4
    Other products            5.2       4      7      5.2       3     -1

    Cumulated sales         135.9     100     12    152.6     100     12

    (1) Portugal, Spain, France, Italy, Greece; (2) Switzerland included

Sales growth

Consolidated sales for the 3rd quarter of 2010 grew by 10%
compared to the same period last year to EUR 42.0 million, resulting in sales
growth of 12% during the first 9 months of the year. Foreign exchange effects
were negligible.

The slight slowdown in the pace of growth compared to the
first half of the year (up 13%) was primarily due to the relatively weak
grasses and tree pollen season, as well as the recognition of a 10%
regulatory rebate in Germany, applicable over the last two months of the
quarter.

Change in financial position

The financial position improved: at 30 September 2010, the net cash
position remained substantial, in spite of a very slight decline which was
consistent with business seasonality.

Significant transactions and events of the quarter

On 6 September, Stallergenes announced having entered into an
exclusive partnership agreement in Japan with Shionogi & Co., Ltd. for the
development and distribution in Japan of Actair(R) (house dust mite allergen
tablets) and a Japanese cedar pollen allergen tablet.

In respect of this partnership, on 6 October 2010 Stallergenes
collected a first instalment of EUR 24 million: corresponding revenues will
be recognised over a period of 2 to 3 years as development work progresses,
including about EUR 3 million over 2010. Stallergenes may subsequently
receive up to EUR 46 million as the various clinical and regulatory
milestones are achieved, compounded by marketing milestone payments and
royalties on net sales of products sold by the partner.

The rollout of Oralair(R) is ongoing at a very satisfactory
pace in Germany and early feedback from markets recently launched - the
Netherlands, Austria, Slovakia and the Czech Republic - is very encouraging.

In France, the Commission de Transparence of the Haute
Autorite de Sante (French HTA) issued a favourable ruling for the inclusion
of Oralair(R) on the formulary of the public health insurance (Securite
Sociale), while considering that the file was not sufficient enough to
support Oralair(R)'s claims to public health interest in relation to
morbidity and quality of life. As a consequence, the SMR (medical service
rendered) should be classified as weak in this first assessment, thereby
entitling to a 15% health insurance refund. A further assessment is to take
place early in 2011 based on new data to be provided by the Company.

As a result, the Company will not be in a position to market
Oralair(R) for the 2011 pollen season in France or other European countries
where refund granting procedures are progressing well but are still ongoing.

Outlook for the current year

Strong growth in the quarter allows us to confirm our guidance
in excess of 10% for the full year and a significant increase in earnings,
due to a stabilised R&D effort this year as well as revenue from the
partnership in Japan.

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.

    Euronext Paris (Compartment B)              GENP
    SBF 120 index.                             LISTED
    ISIN code: FR0000065674                     NYSE
    Reuters code: GEN.PA                      EURONEXT
    Bloomberg code: GEN.FP

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

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