This study will evaluate the efficacy of Stribild® (elvitegravir/cobicistat/emtricitabine/tenofovir disoproxil fumarate (EVG/COBI/FTC/TDF)) single-tablet regimen (STR) after switching from a regimen consisting of raltegravir plus Truvada® (FTC/TDF) at baseline in maintaining HIV-1 RNA < 50 copies/mL at Week 12 in virologically suppressed, HIV-1 infected adults. This study will also evaluate the safety, tolerability, and efficacy of Stribild over 24 and 48 weeks of treatment.