Press Release

Cellectis has been granted a worldwide License to
Lexicon Genetics' Isogenic DNA Technology.

Romainville, France - July the 11^th, 2006 - Cellectis S.A., the genome engineering company, announced today that it entered into an agreement with Lexicon Genetics Incorporated by which Lexicon granted Cellectis a worldwide, non-exclusive commercial sublicense to use isogenic DNA technology for homologous recombination in eukaryotic cells by double-stranded break methodology.

The isogenic DNA technology improves the success rate of homologous recombination - the most precise approach to gene targeting and broadly used to perform gene knock-in or knock-out in organisms or cell lines. Cellectis already had one of the stronger intellectual properties on uses of homologous recombination, including exclusive rights granted by Institut Pasteur under European patent number 419,621, Japanese patents number 3059481, 3298842 and 3298864 and US patents number 6,528,313, 6,638,768 and 6,528,314 as well as related patents and patent applications in other countries.

Homologous recombination is central to genome engineering, and the license granted by Lexicon relating to U.S. Patent number 5,789,215 complements Cellectis' technological portfolio. Isogenic DNA can also be used in conjunction with engineered meganucleases, sequence-specific enzymes developed by Cellectis to induce targeted recombination at high efficiency in chosen locations in genomes.

David Sourdive, Cellectis' Chief Operating Officer & Corporate Development commented, "We have taken an important step with this license. Access to this aspect of the homologous recombination technology strengthens our intellectual property portfolio". He added: "This license further consolidates our position in the field of genome engineering and its applications. It should expand our capability to introduce targeted modifications in genomes through the use of meganucleases with our partners in agriculture, protein production, biological models or stem cells."

Financial terms and conditions of the agreement were not disclosed.

About Cellectis SA

Cellectis SA (www.cellectis.com) was founded in 2000, as a spin-off from Institut Pasteur. Today, Cellectis is the world leader in applying the technology of Meganuclease Recombination Systems to in vivo genome engineering and genome surgery. The company is focused on the research and development of custom-made Meganucleases for in vivo DNA interventions and also provides new tools for rational reverse genetics and targeted recombination. Cellectis develops Meganucleases that can induce unique site-directed double-strand breaks in a living cell, and can be used for biotechnological and therapeutic applications. The company is focusing on bringing "genome surgery" to clinic as a genuine new molecular medicine approach.

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