Gilead Sciences, Inc. (Nasdaq: GILD) announced 48- week data from a Phase III clinical trial evaluating virologically-suppressed patients with HIV who switched from treatment with twice-daily Combivir® (lamivudine/zidovudine) to treatment with Gilead's once-daily Truvada® (emtricitabine and tenofovir disoproxil fumarate) as part of their combination drug therapy. In the SWEET (Simplification With Easier Emtricitabine and Tenofovir) study, patients who switched from Combivir to Truvada, both in combination with once-daily Sustiva® (efavirenz), experienced improvements in a number of treatment-related side effects. Patients in both study arms maintained virological suppression at 48 weeks. The data were presented at the 11th European AIDS Conference (EACS), held October 24-27 in Madrid, Spain.

"As HIV patients live longer and remain on therapy for extended periods of time, the long-term side effect profile of treatment is increasingly more important," said Martin Fisher, MD, Brighton and Sussex University Hospitals, Brighton, United Kingdom and the principal investigator for the SWEET study. "Data from this study indicate that patients on long-term Combivir therapy without clinical lipoatrophy may benefit from switching to Truvada, as virological control can be maintained and limb fat loss and recovery may be improved. These data support the new EACS 2007 guidelines regarding proactive switching."

New European HIV treatment guidelines issued this week at EACS list Truvada among the recommended components of a first-line treatment regimen for antiretroviral naïve patients. Combivir, previously recommended as a first-line treatment option, is now listed as an alternative treatment option.

In the United States, the components of Truvada and Sustiva are available in a fixed-dose combination tablet called Atripla® (efavirenz 600mg / emtricitabine 200mg / tenofovir disoproxil fumarate 300 mg). Atripla is currently the first and only once-daily single tablet regimen approved for the treatment of HIV-1 infection in adults in the United States for use either as stand-alone therapy or in combination with other antiretroviral agents. On October 18, 2007, the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMEA) recommended that Atripla be approved for use in the European Union. A final decision on Atripla by the European Commission is expected by the end of the year.

About The SWEET Study

SWEET was a 48-week, multicenter, prospective, open-label study evaluating 250 HIV-infected patients. At study entry, patients received a treatment regimen of Combivir and Sustiva and were virologically controlled with HIV RNA of less than 50 copies/mL for the last two consecutive testings and less than 400 copies/mL for more than three months. Of the 250 patients enrolled in the study, 234 received at least one dose of study drug. Subjects were randomized 1:1 to continue with a regimen of Combivir and Sustiva (n=117) or switch to a regimen of Truvada and Sustiva (n=117). Baseline characteristics were well matched between study arms. The median prior use of Combivir among patients was 36 months. Among patients who switched to Truvada and Sustiva, 88 percent were suppressed to less than 50 copies/mL at 48 weeks, compared to 85 percent of patients who continued with Combivir (intent-to-treat, missing = failure analysis; 95% CI: -6% to +11%; p=0.70). In addition, median CD4 counts remained comparable between the study arms.

Limb fat was measured using DEXA scans in a subset of 100 study participants, of whom 74 had both baseline and 48-week data available. In this sub-study, a median increase in limb fat of 0.21 kg was observed among patients who switched to Truvada and a median decrease of 0.14 kg was observed among patients who continued on Combivir (p=0.025). Differences in limb fat were more pronounced among patients who had less experience with AZT (zidovudine).

At week 48, a median increase in hemoglobin of 0.5 g/dL was observed among Truvada patients and a median decrease of 0.1 g/dL was observed among those taking Combivir (p