Gilead Announces Results from Phase I/II Study of Investigational HIV Integrase Inhibitor GS 9137

DENVER--(BUSINESS WIRE)--Feb. 9, 2006-- Data Presented at 13th Conference on Retroviruses and Opportunistic Infections; GS 9137 to Enter Phase II Clinical Testing by Second Quarter of 2006

Gilead Sciences, Inc. (Nasdaq:GILD) today announced results of a Phase I/II dose-escalation study of GS 9137, or JTK-303, a novel oral HIV integrase inhibitor. The data, presented this week at the 13th Conference on Retroviruses and Opportunistic Infections (CROI) by Edwin DeJesus, MD, FACP, Medical Director, Orlando Immunology Center (Abstract #J-1011, Late Breaker #160LB), show significant reductions in viral load among HIV-positive patients receiving GS 9137 as monotherapy or in combination with ritonavir as a boosting agent, compared to placebo.

Integrase inhibitors are a new class of antiretrovirals that interfere with HIV replication by blocking the ability of the virus to integrate into the genetic material of human cells. Novel classes of HIV-fighting drugs are needed as patients live longer and exhaust currently available treatment options.

"Ten years after the introduction of combination therapy for HIV, we are seeing an increase in the number of patients whose virus has developed resistance to many of today's drugs," said Dr. DeJesus, the study's principal investigator. "New and better options are desperately needed, particularly among treatment-experienced patients who must often take complex regimens."

About the Study

This Phase I/II study was a double-blind, randomized, placebo-controlled monotherapy study to evaluate the safety, tolerability and antiviral activity of GS 9137 in HIV-infected treatment-naive and treatment-experienced patients. Forty patients were randomized and received one of five doses of GS 9137 (n=30) or placebo (n=10) with food for 10 days. The study evaluated GS 9137 at 200 mg twice daily (BID) (n=6), 400 mg BID (n=6), 800 mg BID (n=6), 800 mg once daily (QD) (n=6), and 50 mg boosted with 100 mg ritonavir QD (n=6). At study entry, patients were not receiving antiretroviral therapy, had HIV RNA (viral load) between 10,000 and 300,000 copies/mL and CD4 cell count greater than or equal to 200 cells/microliter. At baseline, study participants had a mean viral load of 4.75 log10 copies/mL and mean CD4 cell count of 442 cells/microliter. The primary efficacy endpoint was the maximum reduction in viral load from baseline.

GS 9137 monotherapy demonstrated significant antiviral activity compared to placebo (p less than 0.0001) at all doses. Median changes in viral load for all doses appear in the following chart.


----------------------------------------------------------------------
Study Cohort  200 mg   400 mg   800 mg  800 mg QD  50 mg +   Placebo
                BID      BID      BID              100 mg
              (N = 6)  (N = 6)  (N = 6)  (N = 6)   RTV QD    (N = 10)
                                                   (N = 6)
----------------------------------------------------------------------
Median Change
 in HIV RNA
   log10
  copies/mL    -1.48    -2.03    -1.78    -0.96     -2.03     -0.24
----------------------------------------------------------------------

There were no discontinuations or serious adverse events in groups receiving GS 9137. All adverse events were grade 1/2 in severity, resolved while on treatment and were not associated with GS 9137 dosing.

"The antiviral response observed in this early study is promising," said Norbert Bischofberger, PhD, Executive Vice President, Research and Development, Gilead Sciences. "Larger and longer-term studies are needed to continue to assess the safety and efficacy of this compound, and Gilead looks forward to initiating a Phase II study shortly."

About GS 9137

GS 9137, also known as JTK-303, was licensed by Gilead from Japan Tobacco (JT) in March 2005. Under the terms of the company's agreement with JT, Gilead has exclusive rights to develop and commercialize GS 9137 in all countries of the world, excluding Japan where JT will retain rights. GS 9137 has been previously evaluated in a Phase I study in Japan to assess pharmacokinetics and safety in healthy volunteers. Data from preclinical and Phase I studies by Japan Tobacco describing the compound's human pharmacokinetics and safety profile were also presented this week. As an investigational compound, GS 9137 has not yet been determined safe or efficacious in humans for its ultimate intended use.

About Gilead Sciences

Gilead Sciences is a biopharmaceutical company that discovers, develops and commercializes innovative therapeutics in areas of unmet medical need. The company's mission is to advance the care of patients suffering from life-threatening diseases worldwide. Headquartered in Foster City, California, Gilead has operations in North America, Europe and Australia.

This press release includes forward-looking statements, within the meaning of the Private Securities Litigation Reform Act of 1995, that are subject to risks, uncertainties and other factors, including risks related to Gilead's ability to develop and commercialize this product. For example, the safety and efficacy data from additional clinical studies may not warrant further development of this compound and initiating and completing clinical trials may take longer or cost more than expected. These risks, uncertainties and other factors could cause actual results to differ materially from those referred to in the forward-looking statements. The reader is cautioned not to rely on these forward-looking statements. These and other risks are described in detail in the Gilead Annual Report on Form 10-K for the year ended December 31, 2004, filed with the U.S. Securities and Exchange Commission. All forward-looking statements are based on information currently available to Gilead and Gilead assumes no obligation to update any such forward-looking statements.

For more information on Gilead Sciences, please visit the company's website at www.gilead.com or call Gilead Public Affairs at 1-800-GILEAD-5 or 1-650-574-3000.

CONTACT: Gilead Sciences, Inc.
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SOURCE: Gilead Sciences, Inc.