Cellectis SA Clarifies Competitor's Comments on Preliminary U.S. Patent Office Action.

ROMAINVILLE, France -- Parc Biocitech, Romainville, June 10, 2009 -- On March 13, 2008, the genome engineering company Cellectis SA (Alternext: ALCLS) initiated a patent infringement lawsuit in the U.S. District Court in North Carolina against Precision Biosciences Inc., for infringing two of its patents directed to the use of molecules known as megaucleases in recombinant biotechnology. These two patents-in-suit, U.S. Patent Nos. 7,309,605 and 6,610,545, are exclusively licensed from Institut Pasteur, a world-renowned, not-for-profit research institution, and are part of a portfolio of patents and applications in the endonuclease field that Cellectis owns or to which it has exclusive rights. Currently, Cellectis holds a portfolio of 42 granted patents, with more than 130 applications for additional patents pending.

Well after Cellectis filed its suit, Precision asked the U.S. Patent Office to reexamine two related, but separate, patents also licensed exclusively to Cellectis by Institut Pasteur, U.S. Patent Nos. 7,214,536 and 6,833,252. The Patent Office recently agreed to reexamine these two related patents. "This is a normal and common administrative procedure. The process is likely to be long, involving multiple legal steps. A final decision ultimately will be given by the U.S. Patent Office and any conclusions drawn before this decision are premature," said Dr. Andre Choulika, CEO of Cellectis.

The Cellectis patents to be reexamined by the U.S. Patent Office are not the two patents-in-suit that Cellectis has accused Precision of infringing in the U.S. District Court. And, in fact, Precision has not sought to reexamine the patents it has been accused of infringing. Nevertheless, Precision issued a press release to the industry yesterday that Cellectis believes is misleading, in that it not only overstates the Patent Office's decision to reexamine the related patents, a routine matter and one to which the patent owner has not yet responded, but conflates the Patent Office proceeding with the U.S. District court infringement action. The U.S. District Court and the Patent Office proceedings involve separate patents, yet Precision's press release misleadingly suggests that the Patent Office has determined that Precision does not infringe the separate patents-in-suit in the U.S. District Court.

"We are disappointed that Precision is trying to litigate its case in the press, rather than in the Court. We are confident in the value of Cellectis' extensive patent portfolio, and we will continue to vigorously assert our patent rights in our infringement case against Precision in the U.S. District Court," said Dr. Choulika.

About Cellectis

Cellectis S.A. (www.cellectis.com) is a world leader in genome engineering and genome surgery. For more information on Cellectis, visit our web site: www.cellectis.com

Disclaimer

This press release contains forward-looking statements that relate to the Company's objectives. Such forward-looking statements are based on the current expectations and assumptions of the Company's management only and involve risk and uncertainties. Potential risks and uncertainties include, without limitation, whether the Company will be successful in implementing its strategies, whether there will be continued growth in the relevant market and demand for the Company's products, new products or technological developments introduced by competitors, and risks associated with managing growth. Unfavorable developments in connection with these and other risks and uncertainties described, in particular, in the Company's prospectus prepared in connection with its IPO and on which the French Autorite des marches financiers ("AMF") granted its visa nx 07-023 on January 22, 2007, could cause the Company to fail to achieve the objectives expressed by the forward-looking statements above.