Press Releases

May 21, 2002

Gilead Announces Initiation of NIH-sponsored Phase I Trial to Evaluate Tenofovir Topical Gel as Preventive for Vaginal Transmission of HIV

The Phase I study (HPTN 050) is sponsored by the Division of AIDS of the National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), and is being conducted by the HIV Prevention Trials Network under the auspices of Family Health International.

Recent statistics estimate that worldwide nearly 40 million adults and children were living with HIV/AIDS at the end of 2000, and that each day 15,000 new HIV infections occur. Because the majority of HIV is transmitted through heterosexual contact, public health experts have identified the need for new ways to prevent the sexual transmission of HIV. While condom use has been shown to prevent HIV transmission, public health experts point out that women often are unable to negotiate the proper use of condoms by their male partners.

"Tenofovir topical gel is a very exciting investigational microbicide because it is the first one that contains an antiretroviral agent," said Lisa A. Maslankowski, MD, Principal Investigator, University of Pennsylvania and Co-Chair of the Phase I clinical trial. "Unlike other microbicides, when HIV comes in contact with an uninfected T-cell, tenofovir is already activated to prevent the HIV virus from replicating. If HIV is unable to reproduce, it is unlikely to survive long enough to cause systemic infection."

"Even if the use of a topical microbicide, such as tenofovir, could prevent half of the new HIV infections estimated to occur, that would potentially mean that as many as 7,500 people each and every day could be spared from contracting this terrible disease," continued Dr. Maslankowski.

"Another compelling characteristic of tenofovir is its potent activity against strains of HIV that have become resistant to other anti-HIV drugs," explained Dr. Maslankowski. "With the increasing incidence of patients who become infected with multidrug-resistant HIV, it is important that a topical microbicide remain active against a variety of HIV mutations. In vitro data show that tenofovir is a potent inhibitor of many drug-resistant strains of HIV."

As a member of the novel class of antivirals called nucleotide analogues, tenofovir is characterized by its ability to enter and inhibit viral replication in infected and uninfected or resting cells, where it may form protective reservoirs of active drug. Tenofovir also has a long intracellular half-life, which is an important characteristic for drugs designed to treat chronic viral infections.

    About the Phase I Tenofovir Microbicide Study

At the conclusion of the study, patients will be evaluated for signs of the effects of daily use of tenofovir topical gel including symptoms of irritation or other systemic side effects. Secondary endpoints include degree of acceptance of the treatment by study participants and their sexual partners. A subgroup of women will be tested to see if the active ingredient in tenofovir gel is absorbed into the bloodstream.

"This study protocol went through a rigorous peer-review process by NIH committees and clinical researchers before being approved for conduct by the HIV Prevention Trials Network," said Kenneth Mayer, MD, Principal Investigator, Miriam Hospital and Brown University, Providence, RI and Co-Chair of the Phase I clinical trial. "The feedback we received indicates that the research community is very enthusiastic about the potential development of tenofovir as a topical microbicide."

    Early Animal Data

"We are pleased to be working with the NIAID to explore additional applications of this important antiviral beyond the treatment setting. As a topical microbicide gel, tenofovir may be able to help prevent the thousands of new HIV infections that occur each year, and consequently help slow the growing magnitude of the worldwide AIDS epidemic," said John C. Martin, PhD, President and Chief Executive Officer of Gilead. "From our controlled clinical trials of the drug's oral formulation, Viread, we know that the unique molecular properties of tenofovir can result in a valuable anti-HIV treatment. We will continue to work with government, the advocacy community and international health organizations to explore additional uses of tenofovir to potentially extend its therapeutic benefits to a greater variety of patient populations in need."

    About Viread

In the United States, Viread is indicated in combination with other antiretroviral agents for the treatment of HIV-1 infection. This indication is based on analyses of plasma HIV-1 RNA levels and CD4 cell counts in a controlled study of Viread of 24 weeks duration and in a controlled, dose ranging study of Viread of 48 weeks duration. Both studies were conducted in treatment-experienced adults with evidence of HIV-1 viral replication despite ongoing antiretroviral therapy. Studies in antiretroviral-naive patients are ongoing; consequently, the risk-benefit ratio for this population has yet to be determined.

    Viread Safety Profile

The most common adverse events in patients receiving Viread were mild to moderate gastrointestinal events, such as nausea, diarrhea, vomiting and flatulence. Laboratory abnormalities observed in clinical studies occurred with similar frequency in the Viread and placebo-treated groups. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogues alone or in combination with other antiretrovirals.

    Gilead Sciences, Inc.

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 that could cause actual results to differ materially from those referred to in the forward-looking statements. For example, in vitro and animal data for tenofovir referred to in this press release cannot predict with certainty clinical success in humans. Accordingly, there is a risk that these data will not be observed in human studies. 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, 2001 and in Gilead's Quarterly Reports on Form 10-Q, all of which are on file 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.

Note to Editors: The following are principal investigators in the tenofovir gel microbicide study:

Wafaa El-Sadr, MD          Lisa Maslankowski, MD
Principal Investigator     Principal Investigator
Harlem Hospital            University of Pennsylvania
New York, NY               Philadelphia, PA
Kenneth Mayer, MD
Principal Investigator
Miriam Hospital and
Brown University
Providence, RI

For full prescribing information for Viread, please visit www.viread.com. Viread is a trademark of Gilead Sciences, Inc.

CONTACT:          Gilead Sciences
                  Susan Hubbard, 650/522-5715 (Investors)
                  Erin Edgley, 650/522-5635 (Media)

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