Lexicon Genetics Inc has reiterated its position that Deltagen Inc continued to willfully infringe the claims of US Patent No. 5,789,215 (the ``215 patent'') which, among other things, covers the most widely-used processes for producing knockout mice.

Since the 215 patent claims a patented process, a prevailing plaintiff will be able to halt any further use of any knockout mice produced using the patented process by either the defendant or the defendant's customers.

``We believe Deltagen's products and services demonstrate broad use and dependence upon isogenic DNA technology,'' stated Lance Ishimoto, Lexicon's Vice President of Intellectual Property. ``We believe these activities are in clear violation of our rights under the 215 patent.''

United States Patent No. 5,789,215 covers methods of engineering the animal genome using isogenic DNA technology -- a technology of critical importance for the efficient commercial-scale production of knockout mice by homologous recombination.

Lexicon itself uses two methods to produce knockout mice: homologous recombination, which involves the use of the same isogenic DNA technology that is the subject of Lexicon's claims against Deltagen, and a separate, high-throughput gene trapping technology invented by Lexicon which it has used to create the OmniBank library of more than 75,000 knockout mouse clones.

Lexicon Genetics Incorporated is a leader in defining the functions of genes for drug discovery using large-scale knockout mouse technology. Lexicon has invented high-throughput gene trapping technology to discover thousands of genes and expand its OmniBank library of tens of thousands of knockout mouse clones.

The company uses an integrated platform of functional genomic technologies to accelerate large-scale analysis of mammalian gene function for drug discovery.