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.