AB Science — Capital/Financing Update 2010

May 4, 2010

Paris, May 04, 2010 – 6:00 pm

Total initial public offering size increased to €31.6 million

post exercise in full of the over‐allotment option

AB Science announced today in relation to its initial public offering that the Lead manager and Bookrunner, Société Générale Investment Banking, on behalf of the Underwriters, has exercised in full the over‐ allotment option, resulting in the purchase of 325,515 additional existing shares at the offering price of €12.65 per share.

As a result, the total number of AB Science shares offered to the market in connection with its IPO amounts to 2,495,609 shares, or approximately 8.22% of AB Science group's share capital and voting rights (i.e. a free float of 9.0% post conversion of the convertible bonds into 237.154 ordinary shares).

The total size of the IPO, Public Offering & Global Placement, increased to €31.6 million.

In addition, Société Générale, in its capacity as stabilising agent, has informed AB Science that no stabilisation was carried out during the stabilisation period, which started on April 23th, 2010 (after the issue of AB Science 's press release announcing the results of the offering) and ended today.

Public information

Copies of the Prospectus are available free of charge from the Company and from the Lead Manager and Bookrunner and the Joint‐Lead Manager. The Prospectus may be viewed on the websites of the Company (www.ab‐science.com) and the AMF (www.amf‐france.org). The legal and financial documents required to be made available to shareholders may be consulted at the registered office of the Company, 3 avenue George V, 75008 Paris. The attention of investors is drawn to Section 4, "Risk Factors", contained in the Document de base registered with the AMF, the update of such Document de base filed with the AMF and to Section 2 "Risk Factors" contained in the Note d'opération.

About AB Science

Founded in 2001, AB Science is a pharmaceutical company specializing in the research, development and commercialization of protein kinase inhibitors (PKIs), a new class of targeted molecules whose action is to modify signalling pathways within cells. Through these PKIs, the Company targets diseases with high unmet medical needs (cancer, inflammatory diseases and central nervous system diseases), in both human and veterinary medicines. Thanks to its extensive research and development capabilities, AB Science has its own portfolio of molecules. Masitinib, a lead compound, has already been registered in veterinary medicine in Europe and is pursuing three on‐going phases 3 in human medicine in pancreatic cancer, GIST and mastocytosis.

AB Science is listed on NYSE Euronext Paris (Compartment B) ‐ ISIN: FR0010557264 – Ticker: AB

Further information is available on AB Science's website: www.ab‐science.com

Financial Communication & Press Relations

Contacts Citigate Dewe Rogerson : Agnès Villeret ‐ Tel: +33 1 53 32 78 95 ‐ agnes.villeret@citigate.fr Matthieu Pirouelle ‐ Tel : +33 1 53 32 84 77 ‐ matthieu.pirouelle@citigate.fr

Disclaimer

This press release, together with the material set forth herein, does not constitute an offer of securities for sale nor the solicitation of an offer to purchase securities in any jurisdiction. Distribution of such press release in certain jurisdiction may constitute a breach of applicable laws and regulation.

In particular:

This press release does not constitute an offer to sell or the solicitation of an offer to buy any financial instruments in the United States. Securities mentioned in this document have not been and will not be registered under the Securities Act of 1933, as amended (the "Securities Act") and may not be offered or sold in the United States absent registration or an exemption from the registration requirements of the Securities Act. Any public offer of securities in the United States shall be made by means of a prospectus that may be obtained from the issuer containing detailed information regarding the Company, its management and financial statements. The Company does not intend to register this offering in all or in part or to make a public offer of securities in the United States.

This press release is not an invitation nor is it intended to be an inducement to engage in investment activity for the purpose of section 21 of the Financial Services and Markets Act 2000, as amended ("FSMA"). This document is directed only at (i) persons outside the United Kingdom; or (ii) persons in the United Kingdom that are "qualified investors" within the meaning of Article 2(1)(e) of Directive 2003/71/EC including any relevant implementing measure in each member state, that are also (a) persons authorised under FSMA or otherwise having professional experience in matters relating to investments and qualifying as investment professionals under article 19 of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005, as amended (the "Financial Promotion Order"); or (b) institutions or corporations qualifying as high net worth persons under Article 49(2)(a) to (d) of the Financial Promotion Order; or (c) any other persons to whom this document for the purposes of Section 21 of FSMA can otherwise lawfully be made (all such persons together being referred to as "Relevant Persons"). Any person in the United Kingdom that is not a Relevant Person should not act or rely on this document.

This document contains forward‐looking statements. No guarantee can be given as to any of the events anticipated by the forward‐looking statements, which are subject to inherent risks, including those described in the Prospectus, changes in economic conditions, the financial markets or the markets in which AB Science operates.