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

ROMAINVILLE, France--(Business Wire)--
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. André 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 Autorité des marchés financiers
("AMF") granted its visa n° 07-023 on January 22, 2007, could cause the Company
to fail to achieve the objectives expressed by the forward-looking statements
above.

Cellectis S.A.
Marc Le Bozec, CFO
+33 (0)1 41 83 99 00
investors@cellectis.com
or
Alizé RP
Caroline Carmagnol
+33 (0) 6 64 18 99 59
caroline@alizerp.com

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