Antiretroviral naive adults with HIV-1 RNA 5000 copies per milliliter and a CD4 count 50 cells per microliter were randomized 2:1 to receive an STR of elvitegravir/cobicistat/emtricitabine / tenofovir alafenamide ( E/C/F / TAF ) or elvitegravir/cobicistat/emtricitabine / tenofovir disoproxil fumarate ( E/C/F / TDF ) , plus placebo for 48 weeks .