OPEN-LABEL PILOT STUDY TO EVALUATE SWITCHING FROM A REGIMEN CONSISTING OF RALTEGRAVIR PLUS EMTRICITABINE/TENOFOVIR DF FIXED-DOSE COMBINATION TO THE ELVITEGRAVIR/COBICISTAT/EMTRICITABINE/TENOFOVIR DF SINGLE-TABLET REGIMEN IN VIROLOGICALLY SUPPRESSED, HIV-1 INFECTED PATIENTS: