Company Press Release

Cellectis S.A. wins patent battle in the field of targeted recombination and gene correction

European Patent Office Affirms Revocation of Sangamo's Licensed Patent

Romainville, France - June the 14^th, 2005 - Cellectis S.A., the genome engineering company, announced today that the Opposition Division of the European Patent Office ("EPO") invalidated the European Patent owned by Johns Hopkins University and licensed to Sangamo Biosciences, Inc. ("Sangamo"). The Patent No EP 0682699 entitled "Functional Domains in Flavobacterium okeanokoites Restriction Endonuclease" was granted on May 7, 2003 and formed the basis of Regional Phase patents in France, Germany, Great Britain, Ireland and Switzerland. The granted claims of the patent covered technologies used in Sangamo's programs in targeted recombination and gene correction.
On February 2004 Cellectis filed a Notice of Opposition to the EPO, and on May 2005 the Opposition Division revoked the Europen Patent EP 0682699 due to the lack of inventive step.

About Cellectis: 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. Cellectis is focusing on bringing "Genome Surgery" to clinic as a genuine new approach in molecular medicine and its mission is to turn Meganuclease Recombination Systems into therapeutic drugs for gene repair. This approach aims at repairing genomic DNA sequences causing diseases such as mutated genes or resident viruses. Cellectis first key market for human genome surgery is the possible cure of severe inborn diseases.

About c-MRS: Custom MRS (or c-MRS) is a product generated by Cellectis' Meganuclease platform and developed into a fully integrated genome engineering system. c-MRSs 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 c-MRS that can be used in multiple genome engineering applications by our partners. c-MRS will allow to target a preferred chromosomal target for any insertion, deletion, replacement or repair and according to any reverse genetics plans.

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