Press Release

Cellectis S.A. announces the full exercise of the greenshoe in the context of its initial public offering on the Alternext market of Euronext Paris.

Romainville, France - March the 5^th, 2007 - Cellectis S.A., a biotechnology company specializing in genome engineering and developing a new range of products for the custom rewriting of DNA sequences for the research, healthcare and industrial sectors, today announced the full exercise of the over-allotment option granted to its bookrunner and listing sponsor SOCIETE GENERALE Corporate & Investment Banking, as part of the company's initial public offering (IPO) on the Alternext market of Euronext Paris. Cellectis also emphasized its satisfaction with the success of the listing.
SOCIETE GENERALE Corporate & Investment Banking has notified Cellectis S.A. of the full exercise of the over-allotment option, thus increasing the sum raised by the Cellectis IPO from around 21.2 million euros to around 24.4 million euros (prior to deduction of bank commissions and legal & administration fees associated with the offering).

• the reimbursement on February 16th 2007 of the warrants issued by Cellectis S.A. in June 2005 (resulting in the issue of 1,738,678 new shares),
• the exercise of 102,000 "BSPCE" warrants for company founders (resulting in the issue of 2,040 new shares) and
• the exercise of the above-mentioned over-allotment option (resulting in the issue of 310,112 additional new shares);

In view of the above-mentioned operations, the free float stands at around 28.1% of the company's share capital.

The sole bookrunner and listing sponsor is SOCIETE GENERALE Corporate & Investment Banking, 17, cours Valmy, 92972 Paris-La Défense 7.

Practical information:

About Cellectis S.A.

Cellectis S.A. is a biotech company developing innovative, proprietary technologies for genome engineering: a new class of "molecular scissors" - MeganucleaseTM enzymes - capable of recognizing, binding and cutting DNA with extremely high specificity. The company is developing and commercializing Meganuclease Recombination Systems (MRSs) which combine these molecular scissors with a DNA matrix for targeting and modifying a gene of interest in vivo (and without affecting the rest of the genome) via the action of the cell's natural maintenance and repair system. By developing this first-in-class technology on the industrial scale, Cellectis has opened the way to rational genome engineering, which seeks to accurately and reliability insert, modify, modulate or correct genes in any living organism - without the addition of foreign genes, which are often imprecise and poorly tolerated. Cellectis now holds a portfolio of 8 MRSs in development, of which 5 have a therapeutic focus.

Cellectis is a spin-off from the Pasteur Institute in Paris, which has granted the company exclusive rights to 26 of the 27 granted patents and 38 of the 69 pending applications in its current portfolio, including one which will fall into the public domain in 2009, followed by 6 others in 2010. Before its IPO, Cellectis had already raised 17.5 million euros in two rounds (in 2000 and 2002/2005) to support its R&D and commercial development. The company's principal shareholders are AGF Private Equity, BankInvest Biomedical Venture, Edmond de Rothschild Investment Partners, Kaminvest Holding and Odyssée Venture. To date, Cellectis has signed 45 collaboration agreements and alliances worldwide with pharma companies (including AstraZeneca, Merck & Co., Wyeth and Shire), agrochemical groups (including Bayer, DuPont and BASF) and biotech companies (including Genentech, Regeneron and Lexicon Genetics). Cellectis' corporate headquarters are located on the Biocitech biopark at Romainville near Paris. It currently has 40 staff, including 16 PhDs.

Availability of the prospectus

Copies of the prospectus approved by the French Autorité des Marchés Financiers ("AMF") on January 22nd, 2007 under visa number 07-023 are available free of charge from Cellectis S.A, 102, route de Noisy, F-93230 Romainville, France, and on the websites of the AMF (http://www.amf-france.org) and Cellectis (http://www.cellectis.com). The French prospectus includes the document de base registered with the AMF on December 22, 2006 under number I.06-198, the note d'opération and a summary thereof.

Risk factors

Cellectis draws the attention of the public to the risks set out in Chapter 4 of the document de base and in Chapter 2 of the note d'opération.

This press release, and the information contained herein, do not constitute an offer to sell or a solicitation of an offer to buy or subscribe for shares in Cellectis in any country.
Shares in Cellectis may not be sold in the United States of America absent registration or an exemption from registration under the U.S. Securities Act of 1933, as amended. There will be no registration of all or part of the offering referred to in this press release in the United States of America nor any public offering of Cellectis in the United States of America. This press release may not be distributed, in particular, either directly or indirectly, in the United States of America and does not constitute an offer to sell securities in the United States of America.