A 48-week study to investigate the safety and effectiveness of a new compact formulation of two already FDA-approved anti-HIV drugs in subjects who have already been receiving treatment for their HIV infection.

A phase III, randomized, open-label, parallel, multicenter study to evaluate treatment with fixed-dose combination of abacavir/lamivudine (600mg/300mg) once-daily versus abacavir (300mg) twice-daily and lamivudine (300mg) once-daily in combination with tenofovir once-daily and a new PI or NNRTI for 48 weeks in ART-experienced HIV-1 infected patients.

Inclusion Criteria:

• Antiretroviral therapy (ART) experienced and currently receiving a stable regimen containing 3 nucleoside reverse transcriptase inhibitors (NRTIs), or 2 NRTIs plus a protease inhibitor (PI) or non-nucleoside reverse transcriptase inhibitors (NNRTI) for at least 3 months (there should be no significant ART modifications for at least 3 months and no ART change anticipated between Screening and initiation of the study therapy).
• Patients must be naive to tenofovir.
• HIV-1 RNA level > 1000 copies/ml on at least one occasion within 21 days of study entry.
• A CD4 cell count > 50 cells/mm3.
• Specified viral genotypes.

Exclusion Criteria:

• Pregnant or breast-feeding women.
• Has an active diagnosis of AIDS.
• Additional qualifying criteria to be determined by the physician.