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RDEA806, A Potent, New HIV NNRTI With a High Genetic Barrier to Resistance and a Broad Spectrum of Activity, Introduced at 47th ICAAC

* RDEA806 is highly active in vitro against wild-type and the majority of HIV strains carrying key reverse transcriptase mutations

CHICAGO, September 18, 2007 /PRNewswire-FirstCall/ -- Ardea Biosciences, Inc. today presented promising preclinical data on RDEA806, a novel HIV non-nucleoside reverse transcriptase inhibitor (NNRTI) at the 47th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) posters H-1040 and H-1041, Poster Session 101, HIV: New Drugs. To view the posters on-line, go to

Preclinical data suggest that RDEA806 has the potential to be used in both naive and treatment-experienced patients, including those harboring the K103N mutation, the most abundant mutation observed in patients failing therapy with efavirenz (Sustiva(R), Bristol-Myers Squibb) and in some newly infected patients.

RDEA806 was designed to accommodate the amino acid changes associated with NNRTI resistance and is highly active in vitro against wild-type and the majority of HIV strains carrying key reverse transcriptase mutations, including potent coverage of the 10 most prevalent strains of HIV found in patients failing therapy with efavirenz.* These include viral strains with both single and double mutations, e.g., K103N-L100I.

RDEA806 also has a much higher barrier to resistance than currently approved NNRTIs, which could translate into more durable viral suppression. In parallel serial passage studies with wild-type and K103N virus, high-level resistance to RDEA806 was not obtained for almost one year, compared to 3 months for efavirenz with wild-type virus and one month for efavirenz with virus with the K103N mutation.

"To discover RDEA806, our medicinal chemists synthesized over 1,000 analogues in a structure-activity relationship (SAR) effort to optimize potency and pharmacokinetic properties, while ensuring potent antiviral activity against the majority of the HIV strains associated with NNRTI treatment failure. These promising preclinical results led us to conduct Phase 1 clinical trials, the results of which will be presented at ICAAC tomorrow at Poster Session 160 on Antiviral Agents," said Barry D. Quart, PharmD, President and CEO.

About RDEA806

RDEA806 is a novel non-nucleoside reverse transcriptase inhibitor (NNRTI) for the potential treatment of HIV infection. Based on preclinical and clinical studies to-date, Ardea believes that RDEA806 possesses several attractive properties. These include: potent antiviral activity against a wide range of HIV viral isolates, including those that are resistant to efavirenz (Sustiva(R), Bristol-Myers Squibb) and other currently available NNRTIs; a high genetic barrier to resistance; the potential to be administered in a patient-friendly, oral dosing regimen; limited pharmacokinetic interactions with other drugs; and the ability to be co-formulated with other HIV antiviral drugs.

About Ardea Biosciences, Inc.

Ardea Biosciences is focused on the discovery and development of small-molecule therapeutics for the treatment of viral diseases, cancer and inflammatory diseases. The Company plans to initiate clinical studies on four compounds this year. These include RDEA806, the Company's lead non-nucleoside reverse transcriptase inhibitor (NNRTI) for the treatment of HIV, which recently completed Phase 1 clinical trials, RDEA119, a mitogen-activated ERK kinase (MEK) inhibitor for the treatment of cancer and inflammatory diseases, scheduled to enter Phase 1 clinical trials in the second half of 2007, and a follow-on NNRTI and a follow-on MEK inhibitor, both of which are scheduled to enter first-in-human studies in the fourth quarter of 2007.

Statements contained in this press release regarding matters that are not historical facts are "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act of 1995. Because such statements are subject to risks and uncertainties, actual results may differ materially from those expressed or implied by such forward-looking statements. Such statements include, but are not limited to, statements regarding: Ardea's goals, including its goal of initiating clinical studies on four compounds this year, the expected properties and benefits of its compounds and the results of clinical and other studies. Risks that contribute to the uncertain nature of the forward-looking statements include: risks related to the outcomes of preclinical and clinical trials, risks related to regulatory approvals, delays in commencement of preclinical and clinical tests, and costs associated with internal development and in-licensing activities. These and other risks and uncertainties are described more fully in Ardea's most recently filed SEC documents, including its Annual Report on Form 10-K and Quarterly Reports on Form 10-Q, under the headings "Risk Factors." All forward-looking statements contained in this press release speak only as of the date on which they were made. Ardea undertakes no obligation to update such statements to reflect events that occur or circumstances that exist after the date on which they were made.

    *Potent coverage is defined as less than a 10-fold shift in antiviral

     activity versus wild-type virus.  Prevalence of resistant strains based

     on Bachelor et al. Antimicrob Agents Chemother. 2000 Sep; 44(9):


CONTACT: Chris Krueger, Chief Business Officer of Ardea Biosciences, Inc.,+1-760-602-9406

Web site:

Ticker Symbol: (OTC-PINK:ARDC)

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Posted: September 2007