Lexicon Genetics Discusses Small Molecule Drug Discovery Programs Monday September 26, 7:30 am ET 
  THE WOODLANDS, Texas, Sept. 26 /PRNewswire-FirstCall/ -- Lexicon Genetics Incorporated (Nasdaq: LEXG - News) is highlighting its progress in several small molecule drug discovery programs today at the UBS Global Life Sciences Conference. Lexicon will discuss the physiological function of the drug targets of two new lead optimization programs -- LG727 for obesity and LG267 for autoimmune disease -- and will also provide preliminary compound data associated with the programs. In addition, Lexicon will provide an update on its progress with optimized lead compounds in its LG617 program for Alzheimer's disease and cognitive impairment. Each of these three drug targets represents a new biologic mechanism of action.
  ADVERTISEMENTLexicon identified these small molecule drug targets in its Genome5000(TM) program. In this program, Lexicon is using its gene knockout technology to discover the physiological functions of 5,000 potential drug targets. Lexicon has knocked out and fully analyzed more than 50% of the genes in the Genome5000, and has completed or initiated the generation of knockouts for all but 10% of the genes included in the program.
  "Lexicon is currently optimizing lead compounds for seven of its internal small molecule drug discovery programs, with encouraging results," said Arthur T. Sands, M.D., Ph.D., president and chief executive officer of Lexicon. "In addition, we have several internal biotherapeutic programs, and we are making significant progress on our drug discovery programs with collaborators. We believe that our broad pipeline will enable us to select for clinical development those compounds and targets that offer a differentiated therapeutic benefit and a strong market opportunity."
  Select Lexicon Small Molecule Drug Discovery Programs
  Lexicon is highlighting its progress in three of its small molecule drug discovery programs. These programs are:
  LG727: Obesity - LG727 is an enzyme that, when knocked out, results in leanness and resistance to diet-induced obesity. Small molecule drugs that block this enzyme may have utility in the treatment of obesity, type II diabetes and metabolic diseases. More than 60 million Americans are considered obese. Lexicon has achieved significant inhibition of the activity of this enzyme with its lead compound in the LG727 program.
  LG267: Autoimmune disease - LG267 is a kinase that, when knocked out, results in decreased immune cell activation and a reduced number of lymphocytes in the peripheral blood. Small molecule drugs that block this kinase may have utility in the treatment of autoimmune diseases, immunosuppression, and lymphoproliferative diseases. Autoimmune diseases alone are estimated to impact between 5% and 8% of the U.S. population. Lexicon's lead compound in the LG267 program is orally bioavailable and is a potent inhibitor of this kinase.
  LG617: Alzheimer's disease and cognition - Lexicon will describe its progress in developing small molecule inhibitors of LG617, a membrane protein that may play a role in cognitive function and has potential application for the treatment of Alzheimer's disease and cognitive impairment. When knocked out, LG617 results in mice with improved learning and memory. Normal mice treated with Lexicon's lead compound in its LG617 program demonstrated enhanced learning and memory.
  Dr. Sands will discuss these small molecule drug discovery programs during his presentation today at 12:30 p.m. Eastern Time at the UBS Global Life Sciences Conference in New York City. A live audio webcast of Dr. Sands' presentation may be accessed on Lexicon's corporate website at lexicon-genetics.com . An archived version of the webcast will be available on the website through October 4, 2005.
  About Lexicon Genetics
  Lexicon Genetics is a biopharmaceutical company focused on the discovery and development of breakthrough treatments for human disease. Lexicon is systematically discovering the physiological and behavioral functions of genes to identify potential points of therapeutic intervention, or drug targets. Lexicon makes these discoveries using its proprietary gene knockout technology to model the physiological effects that could be expected from prospective drugs directed against novel targets. The Company has advanced knockout- validated targets into drug discovery programs in six therapeutic areas: diabetes and obesity, cardiovascular disease, psychiatric and neurological disorders, cancer, immune system disorders and ophthalmic disease. Lexicon is working both independently and through strategic collaborations and alliances to accelerate the development and commercialization of its discoveries. Additional information about Lexicon is available through its corporate website, lexicon-genetics.com .
  Lexicon Genetics Safe Harbor Statement
  This press release contains "forward-looking statements," including statements about Lexicon's growth and future operating results, discovery and development of products, strategic alliances and intellectual property, as well as other matters that are not historical facts or information. These forward-looking statements are based on management's current assumptions and expectations and involve risks, uncertainties and other important factors, specifically including those relating to Lexicon's ability to successfully conduct preclinical development of its drug candidates and advance such candidates into clinical development, achieve its operational objectives, obtain patent protection for its discoveries and establish strategic alliances, as well as those relating to manufacturing, the regulatory process, intellectual property rights, and the therapeutic or commercial value of its drug candidates, that may cause Lexicon's actual results to be materially different from any future results expressed or implied by such forward-looking statements. Information identifying such important factors is contained under "Factors Affecting Forward-Looking Statements" and "Business - Risk Factors" in Lexicon's annual report on Form 10-K for the year ended December 31, 2004, as filed with the Securities and Exchange Commission. Lexicon undertakes no obligation to update or revise any such forward-looking statements, whether as a result of new information, future events or otherwise. |