Open-Label Study to Evaluate Switching From a TDF-Containing Combination Regimen to a TAF-Containing Combination Single Tablet Regimen (STR) in Virologically-Suppressed, HIV-1 Positive Subjects

Inclusion Criteria:

• Ability to understand and sign a written informed consent form, which must be obtained prior to initiation of study procedures
• Currently receiving antiretroviral therapy consisting of E/C/F/TDF, EFV/FTC/TDF, ATV/r + FTC/TDF, or ATV/co + FTC/TDF for ≥ 6 consecutive months preceding the final visit in their earlier study
• Completion of the Week 144 visit in studies GS-US-236-0102, GS-US-236-0103, GS-US-216-0114, or completion of the Week 96 visit in study GS-US-264-0110 (only subjects on an efavirenz-based regimen), or completion of studies GS-US-236-0104, GS-US-216-0105
• Plasma HIV-1 RNA concentrations at undetectable levels for at least 6 consecutive months prior to the screening visit and have HIV RNA <50 copies/mL at the screening visit
• Normal echocardiograph (ECG)
• Estimated glomerular filtration rate (GFR) ≥ 50 mL/min according to the Cockcroft-Gault formula for creatinine clearance
• Hepatic transaminases (AST and ALT) ≤ 5 × upper limit of normal
• Total bilirubin ≤ 1.5 mg/dL, or normal direct bilirubin
• Adequate hematologic function
• Serum amylase ≤ 5 × ULN
• Females of childbearing potential must agree to utilize highly effective contraception methods or be non-heterosexually active or practice sexual abstinence from screening throughout the duration of study treatment and for 30 days following the last dose of study drug
• Female subjects who utilize hormonal contraceptive as one of their birth control methods must have used the same method for at least three months prior to study dosing
• Female subjects who have stopped menstruating for ≥ 12 months but do not have documentation of ovarian hormonal failure must have a serum follicle stimulating hormone (FSH) level at screening within the post-menopausal range based on the Central Laboratory reference range
• Age ≥ 18 years

Exclusion Criteria:

• A new AIDS-defining condition diagnosed within the 30 days prior to screening
• Hepatitis B surface antigen position
• Hepatitis C antibody positive
• Subjects experiencing decompensated cirrhosis
• Females who are breastfeeding
• Positive serum pregnancy test
• Have an implanted defibrillator or pacemaker
• Current alcohol or substance use judged by the Investigator to potentially interfere with subject study compliance
• History of malignancy within the past 5 years or ongoing malignancy other than cutaneous Kaposi's sarcoma, basal cell carcinoma, or resected, noninvasive cutaneous squamous carcinoma
• Active, serious infections (other than HIV-1 infection) requiring parenteral antibiotic or antifungal therapy within 30 days prior to baseline
• Any other clinical condition or prior therapy that, in the opinion of the Investigator, would make the subject unsuitable for the study or unable to comply with dosing requirements
• Participation in any other clinical trial without prior approval from the sponsor is prohibited while participating in this trial
• Subjects receiving ongoing therapy with drugs not to be used with EVG, COBI, FTC, TDF, and TAF or subjects with any known allergies to the excipients of E/C/F/TDF or E/C/F/TAF single-tablet regimen tablets