Press Release

Cellectis announces Research Collaboration and License Agreement with Biogen Idec to engineer a novel customized Meganuclease Recombination System

Romainville, France - September the 21^st, 2005 - Cellectis SA announced today that it had entered into a research collaboration and license agreement with Biogen Idec (NASDAQ: BIIB) to develop a custom Meganuclease Recombination System (c-MRS) designed to enable reproducible high yield production of target proteins in mammalian cells. Cellectis will engineer a novel meganuclease and DNA targeting matrix to induce site-specific homologous recombination and Biogen Idec will assess the robustness of the system. Financial terms of the agreement were not disclosed.

"We are very pleased to be able to provide Biogen Idec, one of the world's leading research-based biopharmaceutical companies, with c-MRS Product and site-directed insertion technologies," said Isabelle Pelletier-Bressac, Vice President Business Development of Cellectis. "Meganuclease are sequence-specific endonucleases with large recognition sites. Cellectis can engineer these meganucleases to induce homologous recombination in a wide range of genomic loci of various organisms such as mammalian derived cell lines and consequently brings a tremendous robustness in the generation of cell lines producing biotherapeutic protein, i.e. reproducibility, predictability of yields, and a gain of time in manufacturing."

c-MRS products are based on the use of a custom meganuclease engineered by Cellectis and a DNA targeting matrix sharing some similarities upstream and downstream the target DNA sequence to be modified. These two compounds (custom meganuclease and DNA targeting matrix) make a highly patented system that can be used in multiple genome engineering applications by our partners.

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.

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