Lexicon Genetics Incorporated has been issued U.S. Patent No. 6,436,707 (the "707 patent") entitled "Vectors for Gene Mutagenesis and Gene Discovery." The newly-issued patent extends the scope of Lexicon's broad patent estate in the field of gene trapping, now covered by a total of six issued U.S. patents. The Company also announced the recent issuance of two U.S. patents covering the full-length sequences of potential drug targets discovered through its gene discovery programs. These two patents mark the beginning of a continuing pipeline of expected patent issuances from Lexicon's portfolio of patent applications covering more than 300 full-length human gene sequences.

The 707 patent covers Lexicon's OmniBank library of more than 200,000 gene knockout embryonic stem (ES) cell clones, each of which is identified by DNA sequence from the trapped gene. Knockout mice from OmniBank have been the source of nine of the Company's 14 drug discovery programs to date, the remainder having been derived from Lexicon's complementary gene targeting technologies.

OmniBank is expected to represent about one-half of the gene knockouts in Lexicon's Genome5000 program, which is designed to systematically discover the physiological functions and pharmaceutical utility of 5,000 genes over five years. Lexicon estimates that OmniBank contains gene knockout clones for more than one-half of all genes in the mammalian genome.