Press Release

Cellectis announces publication of data demonstrating ability of meganucleases to induce efficient in toto recombination in mouse liver.

Romainville, France - March the 14^th, 2006 - Cellectis, a biotechnology company specialized in rational genome engineering, announced today the publication, in the Journal of Gene Medicine, of an article entitled "Efficient in toto targeted recombination in mouse liver by meganuclease-induced double-strand break".

Meganuclease-induced gene targeting has emerged as the universal method for efficient and precise genome engineering. Naturally occurring meganucleases have been shown to cleave DNA in living cells, and as a consequence, stimulate homologous recombination up to 10,000-fold. While ex vivo applications have been studied for several years, in toto applications are still out of our reach. Cellectis' recent paper in the Journal of Gene Medicine uses transgenic mice carrying a reporter system based on single-strand annealing to demonstrate, for the first time, using the natural meganuclease I-SceI that double-strand break-induced recombination can be achieved in toto in mammals by simple tail vein injection of a meganuclease expressing adenovirus. These results establish the proof of principle for in toto applications of the technology and represent an important initial step towards the use of designed meganucleases as drugs for genomic therapy.

Cellectis (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 therapeutic 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 44 deals on its Genome Engineering technologies, including with major pharmaceutical and agroscience companies. Cellectis' team today consists of 35 people including 14 PhDs and the total invested capital since the company's inception is approximately EUR 20 million.

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