Phase I/II Data from GS 840 Study in Patients with HIV Infection Presented at Eighth International Conference on Antiviral Research; Data Also Presented on Additional Antiviral Compounds Under Development.

FOSTER CITY, Calif.--(HealthWire)--April 24, 1995--Gilead Sciences, Inc. (NASDAQ: GILD) announced today the presentation of results from its first Phase I/II placebo-controlled human clinical study of GS 840 in patients with human immunodeficiency virus (HIV) infection, the causative agent of AIDS. These data demonstrate that GS 840, when administered orally once per day for two weeks, is safe, generally well tolerated and associated with anti-HIV activity as measured by a drug-related decrease in p24 antigen levels that was statistically significant compared to placebo. The level of p24 antigen in the blood is a surrogate marker of HIV infection. Dose-related side effects observed included mild to moderate gastrointestinal symptoms. A maximum tolerated dose was not reached.

These data were presented today at the Eighth International Conference on Antiviral Research in Santa Fe, New Mexico, by Patricia Barditch-Crovo, M.D., principal investigator of the study from The Johns Hopkins University School of Medicine in Baltimore, Maryland.

As planned, the double-blind, placebo-controlled study enrolled a total of 36 patients who were randomized to receive treatment with GS 840 tablets at one of three dose levels (125, 250 and 500 mg) or an inactive placebo once daily for two weeks. The study was designed to determine the safety, tolerance, pharmacokinetics and potential anti-HIV activity of GS 840 in HIV-infected patients who had CD4 antigen cell counts above 100 and measurable levels of p24 antigen in their blood.

A second Phase I/II study of GS 840 is ongoing at multiple centers in the U.S. for the potential treatment of HIV infection. To date, this study has enrolled and randomized more than 60 patients to receive treatment with either GS 840 or placebo once daily for up to twelve weeks.

GS 840 is an oral prodrug of Gilead's intravenously administered GS 393 (PMEA), a member of a new class of antiviral compounds called nucleotides. A prodrug is a modified version of a parent compound designed to enhance the compound's delivery properties and be converted to the parent compound once inside the body. Preclinical and clinical studies have demonstrated that, following oral delivery, GS 840 is rapidly converted to GS 393 in vivo.

Conference Presentation Recaps Pivotal VISTIDE(TM) Data

In addition, data were presented at a pre-conference symposium that recapped pivotal efficacy results from a Phase II/III study of intravenous VISTIDE(TM) (cidofovir) for the potential treatment of cytomegalovirus (CMV) retinitis, a disease that if untreated can cause blindness in patients with AIDS. These previously reported data demonstrate that VISTIDE delayed the time to progression of retinitis with a median time to progression of 120 days in the treatment group and 22 days in the deferred control group (p=0.000006).

Two other ongoing pivotal studies of intravenous VISTIDE continue to enroll patients with CMV retinitis. A 90-patient study is being conducted in the U.S. by the Studies for the Ocular Complications of AIDS (SOCA) research group, a clinical trials network affiliated with the National Institutes of Health. A 100-patient open-label study, sponsored by Gilead, is being conducted in the U.S. and Europe for patients who have failed approved intravenous therapies for CMV retinitis.

In the above studies, VISTIDE is administered by intravenous infusion once per week for two weeks, and then once every other week thereafter. Currently approved therapies for CMV retinitis are administered multiple times daily by intravenous infusion during the initial weeks of treatment, usually via a surgically implanted catheter. Gilead Sciences is also developing an intravitreous formulation of VISTIDE for local administration by direct injection into the eye. Gilead intends to commence a Phase I/II multi-center, dose-escalating study of this formulation in the second half of 1995.

Conference Presentation Profiles GS 930 Prodrug

At the conference, Gilead researchers and their collaborators will also present preclinical results regarding the oral bioavailability and distribution of GS 930, a prodrug of VISTIDE, that has demonstrated comparable in vivo and in vitro efficacy and an enhanced safety profile. Once administered, GS 930 is converted inside cells to the active component of VISTIDE and has demonstrated preclinical activity against herpes viruses, including CMV, in addition to papilloma viruses. Gilead intends to commence human studies of GS 930 in the second half of 1995.

Gilead has multiple product candidates in clinical studies for severe viral diseases, including cytomegalovirus (CMV); human immunodeficiency virus (HIV), the causative agent of AIDS; human papillomavirus-associated genital warts and herpes simplex virus. Gilead plans to commence clinical studies for chronic hepatitis B virus infection in the near future. Gilead's most advanced candidate is VISTIDE(TM) (cidofovir), which is in pivotal studies for the potential treatment of CMV retinitis.

Gilead Sciences is a leader in the discovery and development of a new class of human therapeutics based on nucleotides, the building blocks of DNA and RNA. The Company's research and development efforts encompass three interrelated programs: small molecule antivirals, cardiovascular therapeutics and genetic code blockers. Gilead's expertise in each of these areas has also resulted in the discovery of non-nucleotide product candidates that expand the Company's technology platforms to include protein synthesis and combinatorial chemistry. Gilead's programs are focused on potential human therapeutics for certain types of viral infection, cardiovascular disease, inflammatory disease and cancer. Gilead Common Stock is traded in The Nasdaq Stock Market's National Market under the symbol GILD.

CONTACT: Gilead Sciences, Inc.

Lana Lauher, 415/573-4858