Gilead Provides Update on Development of Fixed-Dose Regimen of Truvada -emtricitabine and tenofovir disoproxil fumarate- and Sustiva -efavirenz-

FOSTER CITY, Calif.--(BUSINESS WIRE)--April 26, 2005--Gilead Sciences, Inc. (Nasdaq: GILD) today announced that the company is proceeding with the evaluation of a second formulation of a fixed-dose combination of Truvada(R) (emtricitabine and tenofovir disoproxil fumarate) and Bristol-Myers Squibb's Sustiva(R) (efavirenz) for the treatment of HIV. The company will initiate a bioequivalence study in humans and stability studies of the second formulation shortly and, in addition, is evaluating several different alternative formulations.

Preliminary results from the bioequivalence study of the first formulation indicate that efavirenz levels in the blood are lower than those achieved with the recommended 600 mg dose of Sustiva alone and do not meet the definition of bioequivalence. A bioequivalence study is required to demonstrate that a co-formulated product results in the same levels of medication in the blood as achieved when the individual products are dosed simultaneously as separate pills. Based on improvements in formulation as well as data from preclinical studies, Gilead believes the next-generation formulations are likely to achieve higher levels of efavirenz in the blood than those achieved with the first formulation. If the second formulation is proven to be bioequivalent to the products dosed simultaneously as separate pills, the companies could submit a New Drug Application requesting marketing approval of the fixed-dose combination to the U.S. Food and Drug Administration before the end of 2005.

In December 2004, Gilead and Bristol-Myers Squibb announced the establishment of a U.S. joint venture to co-formulate the antiretrovirals Truvada and Sustiva in a fixed-dose regimen. If approved, the new product would be the first complete Highly Active Antiretroviral Therapy (HAART) treatment regimen for HIV available in a fixed-dose combination taken once daily. Fixed-dose combinations contain multiple medicines formulated together and may help simplify HIV therapy for patients and providers. The joint venture established by the two companies is the first of its kind in the field of HIV therapy.

Guidelines issued by the U.S. Department of Health and Human Services (DHHS) list the combination of emtricitabine, tenofovir disoproxil fumarate and efavirenz as one of the preferred non-nucleoside reverse transcriptase inhibitor (NNRTI)-based treatments for use in appropriate patients that have never taken anti-HIV medicines before. It is important that patients be aware that individual HIV medications must be taken as part of combination regimens, and that they do not cure HIV infection or prevent passing HIV to others.

About Truvada

Truvada combines Emtriva(R) (emtricitabine) and Viread(R) (tenofovir disoproxil fumarate) in one tablet taken once a day in combination with other antiretroviral agents. In the United States, Truvada is indicated in combination with other antiretroviral agents (such as non-nucleoside reverse transcriptase inhibitors or protease inhibitors) for the treatment of HIV-1 infection in adults. Safety and efficacy studies using Truvada tablets or using Emtriva and Viread in combination are ongoing.

Emtriva and Viread have each been studied as part of multi-drug regimens and have been found to be safe and effective. In clinical study 303 Emtriva and lamivudine (3TC) demonstrated comparable efficacy, safety and resistance patterns as part of multidrug regimens. These data, and those from study 903, in which lamivudine and tenofovir were used in combination, support the use of Truvada for the treatment of HIV-1 infection in treatment-naive adults. In treatment-experienced patients, the use of Truvada should be guided by laboratory testing and treatment history.

There are no study results demonstrating the effect of Truvada on clinical progression of HIV-1, and it is not recommended that Truvada be used as a component of a triple nucleoside regimen.

Truvada should not be used with Emtriva or Viread, or other drugs containing lamivudine, including Combivir(R), Epivir(R), Epivir-HBV(R), Epzicom(TM) or Trizivir(R). Two-hundred eighty-three patients have received combination therapy with Emtriva and Viread with either a non-nucleoside reverse transcriptase inhibitor or protease inhibitor for 24 to 48 weeks in ongoing clinical studies. Based on these limited data, no new patterns of adverse events were identified and there was no increased frequency of established toxicities. For additional safety information about Emtriva or Viread in combination with other antiretroviral agents, please see "About Emtriva" and "About Viread," below.

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. Viread, Emtriva and Truvada are not indicated for the treatment of chronic hepatitis B virus (HBV) infection and the safety and efficacy of these drugs has not been established in patients co-infected with HBV and HIV. Severe acute exacerbations of hepatitis B have been reported in patients who have discontinued Viread or Emtriva. Hepatic function should be monitored closely with both clinical and laboratory follow-up for at least several months in patients who discontinue Viread, Emtriva or Truvada and are co-infected with HIV and HBV. If appropriate, initiation of anti-hepatitis B therapy may be warranted.

Changes in body fat have been observed in patients taking Viread, Emtriva, Truvada and other anti-HIV medicines. The cause and long term health effect of these conditions are unknown.

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 controlled studies of Viread in treatment-naive adults and in treatment-experienced adults. There are no study results demonstrating the effect of Viread on clinical progression of HIV-1. The use of Viread should be considered for treating adult patients with HIV-1 strains that are expected to be susceptible to tenofovir as assessed by laboratory testing or treatment history.

Drug interactions have been observed when didanosine, atazanavir or lopinavir/ritonavir is co-administered with Viread and dose adjustments may be necessary. Data are not available to recommend a dose adjustment of didanosine for patients weighing less than 60 kg. Patients on atazanavir or lopinavir/ritonavir plus Viread should be monitored for Viread-associated adverse events which may require discontinuation. When co-administered with Viread, it is recommended that atazanavir 300 mg be given with ritonavir 100 mg. Atazanavir without ritonavir should not be co-administered with Viread.

Renal impairment, including serious cases, has been reported. Renal impairment occurred most often in patients with underlying systemic or renal disease or in patients taking concomitant nephrotoxic agents, though some cases have appeared in patients without identified risk factors. Decreases in bone mineral density (BMD) at the lumbar spine and hip have been seen with the use of Viread. The clinical significance of changes in BMD and biochemical markers is unknown and follow-up is continuing to assess long-term impact. The most common adverse events and those occurring in more than 5 percent of patients receiving Viread with other antiretroviral agents in clinical trials include asthenia, pain, abdominal pain, headache, nausea, diarrhea, vomiting, rash (rash, pruritis, maculopapular rash, urticaria, vesiculobullous rash and pustular rash), flatulence, dizziness and depression. Less than 1 percent of patients discontinued participation because of gastrointestinal events.

About Emtriva

    In the United States, Emtriva is indicated, in combination with
other antiretroviral agents, for the treatment of HIV-1 infection in
adults. This indication is based on analyses of plasma HIV-1 RNA
levels and CD4 cell counts from controlled studies of 48 weeks
duration in antiretroviral-naive patients and
antiretroviral-treatment-experienced patients who were virologically
suppressed on an HIV treatment regimen. In
antiretroviral-treatment-experienced patients, the use of Emtriva may
be considered for adults with HIV strains that are expected to be
susceptible to Emtriva as assessed by genotypic or phenotypic testing.

Adverse events that occurred in more than 5 percent of patients receiving Emtriva with other antiretroviral agents in clinical trials include abdominal pain, asthenia (weakness), headache, diarrhea, nausea, vomiting, dizziness and rash (rash, pruritis, maculopapular rash, urticaria, vesiculobullous rash, pustular rash and allergic reaction). Approximately 1 percent of patients discontinued participation because of these events. All adverse events were reported with similar frequency in Emtriva and control treatment groups with the exception of skin discoloration which was reported with higher frequency in the Emtriva treated group. Skin discoloration, manifested by hyperpigmentation on the palms and/or soles, was generally mild and asymptomatic. The mechanism and clinical significance are unknown.

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. Visit Gilead on the World Wide Web at www.gilead.com.

This press release contains "forward-looking statements" as that term is defined in the Private Securities Litigation Reform Act of 1995. The forward-looking statements include statements regarding approval and licensure of the combination product. These statements involve risks and uncertainties, which may cause results to differ materially from those set forth in the statements, including the risks related to the ability of the companies to successfully complete bioequivalence studies of the second or any subsequent formulation or other regulatory requirements to support approval of the combination product, and the willingness of regulatory authorities to grant regulatory approval for the combination product based on data from those studies. No forward-looking statement can be guaranteed, and actual results may differ materially from those projected. Gilead undertakes no obligation to publicly update any forward-looking statement, whether as a result of new information, future events or otherwise. Forward-looking statements in this press release should be evaluated together with the many uncertainties that affect Gilead's business, particularly those mentioned in the cautionary statements in the company's Form 10-K for the year ended December 31, 2004, and in periodic reports on Form 10-Q and Form 8-K.

Truvada, Viread and Emtriva are registered trademarks of Gilead Sciences, Inc.

Sustiva is a registered trademark of Bristol-Myers Squibb Company.

For more information on Gilead, please call the Gilead Public Affairs Department at 1-800-GILEAD-5 (1-800-445-3235) or visit www.gilead.com.

CONTACT: Gilead Sciences, Inc. Amy Flood, 650-522-5643 (media) Susan Hubbard, 650-522-5715 (investors) SOURCE: Gilead Sciences, Inc.