Study to Evaluate Switching From Regimens Consisting of a Ritonavir-boosted Protease Inhibitor Plus Emtricitabine/Tenofovir Fixed-Dose Combination to the Elvitegravir/Cobicistat/Emtricitabine/Tenofovir DF Single-Tablet Regimen in Virologically Suppressed, HIV-1 Infected Patients

Inclusion Criteria:

• Ability to understand and sign a written informed consent form

• Be on a stable antiretroviral regimen consisting of a ritonavir boosted PI plusFTC/TDF continuously for ≥ 6 consecutive months preceding the screening visit

• Be on the first or second antiretroviral drug regimen documented undetectable plasmaHIV 1 RNA levels for ≥ 6 months preceding the screening visit

• No previous use of any approved or experimental integrase strand transfer inhibitor (INSTI) for any length of time

• Documented historical genotype prior to starting initial antiretroviral therapyshowing no known resistance to TDF or FTC

• HIV RNA < 50 copies/mL at screening

• Normal ECG

• Hepatic transaminases ≤ 5 × the upper limit of the normal range (ULN)

• Total bilirubin ≤ 1.5 mg/dL, or normal direct bilirubin

• Adequate hematologic function

• Serum amylase ≤ 5 × ULN

• Estimated glomerular filtration rate ≥ 70 mL/min

• Females of childbearing potential must agree to utilize highly effective contraceptionmethods, or be nonheterosexually active, practice sexual abstinence from screeningthroughout the duration of the study period and for 30 days following the last dose ofstudy drug

• Female participants who utilize hormonal contraceptive as one of their birth controlmethods must have used the same method for at least three months prior to study dosing

• Male participants must agree to utilize a highly effective method of contraceptionduring heterosexual intercourse from the screening visit, throughout the duration ofthe study and for 30 days following discontinuation of investigational medicinalproduct, or must be nonheterosexually active, or practice sexual abstinence

• Age ≥ 18 years

Exclusion Criteria:

• A new AIDS-defining condition diagnosed within the 30 days prior to screening

• Females who are breastfeeding

• Positive serum pregnancy test (female of childbearing potential)

• Receiving drug treatment for hepatitis C, or participants who are anticipated toreceive treatment for hepatitis C during the course of the study

• Experiencing decompensated cirrhosis

• Have an implanted defibrillator or pacemaker

• Current alcohol or substance abuse that would interfere with compliance

• A history of malignancy within the past 5 years or ongoing malignancy other thancutaneous Kaposi's sarcoma, basal cell carcinoma, or resected, noninvasive cutaneoussquamous carcinoma

• Active, serious infections requiring parenteral antibiotic or antifungal therapywithin 30 days prior to Baseline, except for intramuscular penicillin for thetreatment of syphilis

• Have been treated with immunosuppressant therapies or chemotherapeutic agents within 3months of study screening, or expected to receive these agents or systemic steroidsduring the study

• Receiving ongoing therapy with any of the medications, including drugs not to be usedwith elvitegravir, cobicistat, FTC, or TDF; or those with any known allergies to theexcipients of E/C/F/TDF tablets, or FTC/TDF tablets

• No anticipated need to initiate drugs during the study that are contraindicated

• Receiving other investigational drugs

• Participation in any other clinical trial

• Any other clinical condition or prior therapy that would make the participantunsuitable for the study or unable to comply with the dosing requirements