Press Release

Cellectis S.A. Announces a License Agreement with Xenogen Biosciences Corporation

Romainville, France - June the 29^th, 2005 - Cellectis S.A., the genome engineering company, announced today that it entered into an agreement with Xenogen Biosciences Corporation, a wholly owned subsidiary of Xenogen Corporation (Nasdaq: XGEN), by which Cellectis granted Xenogen Biosciences and Xenogen a worldwide non-exclusive commercial license under its patent family relating to a process for the specific replacement or insertion of a gene in an eukaryotic genome.
Under this agreement, Xenogen Biosciences obtained a license from Cellectis for creating and developing genetically engineered mice pursuant to its business activities relating to the production of knock-in mice, and custom LPTA® Animal Models and related technologies.
Financial terms and conditions of the agreement were not disclosed.
Isabelle Pelletier-Bressac, vice-president Business Development of Cellectis commented, "We are delighted to come to an agreement with Xenogen Biosciences, who can use the patented technology in their programs that are both custom and comprehensive for scientific partners looking to develop animal models using gene addition and gene modification techniques".

Cellectis SA (www.cellectis.com) was founded in 2000, as a spin-off from the 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 therapeutical applications. The company is focusing on bringing "genome surgery" to clinic as a genuine new molecular medicine approach.
As of today, Cellectis has entered into 33 deals on its Genome Engineering technologies.

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