Genelabs Technologies, Inc. Announces Presentation of Data on Non-Nucleoside HCV Polymerase Inhibitor at 20th International Conference on Antiviral Research Meeting

REDWOOD CITY, Calif., May 2 /PRNewswire-FirstCall/ -- Genelabs Technologies, Inc. announced today that a presentation was made today at the 20th International Conference on Antiviral Research being held in Palm Springs, California, on a non-nucleoside hepatitis C virus (HCV) polymerase inhibitor discovered by Genelabs.

The oral presentation was given by Christopher D. Roberts, Ph.D., Director of Medicinal Chemistry at Genelabs, entitled “GL59728: A Potent Allosteric Inhibitor of the HCV NS5b RNA Dependent RNA Polymerase with Excellent Pharmacokinetic Properties.”

GL59728 is one of a number of non-nucleoside HCV polymerase inhibitors discovered by Genelabs. In the presentation, Dr. Roberts outlined the lead optimization of certain non-nucleoside HCV polymerase inhibitors through an iterative process involving testing for potency in directly inhibiting HCV NS5b polymerase, inhibiting the replication of an HCV sub-genomic replicon, and pharmacokinetic properties.

The optimized lead that emerged from this chemistry approach, one of several taken by Genelabs, is known as GL59728. The IC50 of GL59728 for inhibition of the HCV NS5b polymerase is 16 nanomolar and the EC50 for inhibition of HCV replicon is 170 nanomolar. Further, GL59728 shows excellent oral bioavailability, exceeding 50% in all four species tested, including higher-order species, low clearance and a half-life consistent with once- or twice-daily dosing. The tissue distribution of GL59728 also appears favorable; since its concentration is enhanced several fold in liver, the site of HCV infection, relative to that obtained in plasma. Importantly, GL59728 was also tested in combination with other classes of HCV antiviral compounds, including a nucleoside chain terminator, a protease inhibitor and interferon alpha, and shown to be additive in activity with each.

In June 2006 Genelabs entered into a license and research collaboration with Novartis covering Genelabs’ non-nucleoside HCV polymerase inhibitors.

“The data presented today clearly support the further investigation of non-nucleoside polymerase inhibitors for the future treatment of HCV infection,” said Ronald C. Griffith, Ph.D., Genelabs’ Chief Scientific Officer. “Furthermore, we believe future treatment of HCV is likely to involve combinations of antiviral drugs and these data suggest that combinations of this type of non-nucleoside agent with interferon or other likely therapeutic drugs, such as nucleoside chain terminators or protease inhibitors, may be feasible.”

About Genelabs Technologies

Genelabs Technologies, Inc. is a biopharmaceutical company focused on the discovery and development of pharmaceutical products to improve human health. We have built drug discovery capabilities that can support various research and development projects. Genelabs is currently concentrating these capabilities on discovering novel compounds that selectively inhibit replication of the hepatitis C virus and advancing preclinical development of compounds from this hepatitis C virus drug discovery program, while also developing a late-stage product for lupus. We believe that these high-risk, potentially high reward programs focus our research and development expertise in areas where we have the opportunity to generate either first-in-class or best-in-class products that will address diseases for which current therapies are inadequate. For more information, please visit www.genelabs.com.

NOTE: Genelabs(R) and the Genelabs logo are registered trademarks and Prestara(TM) is a trademark of Genelabs Technologies, Inc.

NOTE ON FORWARD LOOKING STATEMENTS AND RISKS: This press release contains forward-looking statements including statements on the feasibility of non-nucleoside polymerase inhibitors for the future treatment of HCV infection and the prospects for GL59728. These forward-looking statements are based on Genelabs’ current expectations and are subject to uncertainties and risks that could cause actual results to differ materially from the statements made. Uncertainties and risks include, without limitation, that further testing will not yield positive results or that alternative compounds which may be at an earlier stage may be given preference over GL59728 for future development. Please see the information appearing in the Genelabs’ filings with the Securities and Exchange Commission, including our most recent Annual Report on Form 10-K, under the captions “Risk Factors” and “Forward-Looking Statements” for more discussion regarding these uncertainties and risks and others associated with the company’s research programs, early stage of development and other risks which may affect the company or cause actual results to differ from those included in the forward-looking statements. Genelabs does not undertake any obligation to update these forward-looking statements or risks to reflect events or circumstances after the date of this release.

Contact: James A. D. Smith

President and Chief Executive Officer

Phone: 650-562-1424

Genelabs Technologies, Inc.

CONTACT: James A. D. Smith, President and Chief Executive Officer ofGenelabs Technologies, Inc., +1-650-562-1424

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