Gilead Sciences announced preliminary data from a planned interim 24-week analysis of the company's ongoing Study 934. This study, a 48-week clinical trial, was designed to compare a regimen of Viread (tenofovir disoproxil fumarate), Emtriva (emtricitabine) and efavirenz to Combivir (lamivudine 150 mg/zidovudine 300 mg) and efavirenz in more than 500 treatment-naive patients with HIV.

Preliminary results show a statistically significant difference favouring Viread/Emtriva in the percentage of patients who achieved and maintained HIV RNA less than 400 copies/mL at 24 weeks, based on the FDA Time to Loss of Virologic Response algorithm (TLOVR), a company release said.

Study 934 is a phase III, multi-centre, open-label 48-week clinical trial that enrolled 517 HIV-infected patients in the United States and Europe. The prespecified intent-to-treat population includes 487 patients. Participants in one arm of the study receive Viread 300 mg, Emtriva 200 mg and efavirenz 600 mg, all dosed once daily. Patients in the comparator arm receive Combivir twice daily and efavirenz 600 mg once daily. At study entry, patients had not previously received antiretroviral therapy and had HIV RNA greater than 10,000 copies/mL.

Based on a planned interim 24-week analysis (n=487), preliminary data show 88 per cent of patients in the Viread/Emtriva arm compared to 80 percent of patients in the Combivir arm achieved and maintained HIV RNA less than 400 copies/mL at week 24 using the TLOVR algorithm (p=0.019; 95% CI, +0.8% to +13.3%). In the TLOVR algorithm, 3 per cent of patients on the Viread/Emtriva arm compared to 9 per cent of patients on the Combivir arm discontinued from study regimen due to adverse events (p=0.013). Patients had an increase from baseline of 129 and 111 CD4 cells/mm in the Viread/Emtriva and Combivir arms, respectively. The incidence of grade 3 or 4 clinical adverse events was 9 per cent for the Viread/Emtriva arm compared to 15 per cent for the Combivir arm. Gilead expects to present these data at a scientific conference later this year.

On August 2, the FDA granted marketing approval of Truvada (emtricitabine and tenofovir disoproxil fumarate), a fixed-dose combination of the company's anti-HIV medications Emtriva and Viread. Truvada combines 200 mg of emtricitabine and 300 mg of tenofovir disoproxil fumarate in one tablet, taken once a day in combination with other antiretroviral agents.

Viread, Emtriva and Truvada work by blocking reverse transcriptase, an enzyme crucial for viral replication. By interfering with the replication process, these drugs, when combined with other anti-HIV medications, can help lower the amount of HIV or "viral load" in a patient's body and increase the number of immune system cells (called T cells or CD4 cells). Both of these changes are generally associated with improving a patient's health and decreasing the likelihood of AIDS-related illnesses. The use of Viread, Emtriva and Truvada may be considered for treating patients with HIV strains that are expected to be susceptible as assessed by laboratory testing or treatment history.