Study to Evaluate the Safety and Efficacy of E/C/F/TAF Versus E/C/F/TDF in HIV-1 Positive, Antiretroviral Treatment-Naive Adults

Key Inclusion Criteria: * Ability to understand and sign a written informed consent form, which must be obtained prior to initiation of study procedures * Plasma HIV-1 RNA levels ≥ 1,000 copies/mL at screening * No prior use of any approved or investigational antiretroviral drug for any length of time, except the use for pre-exposure prophylaxis (PREP), or post-exposure prophylaxis (PEP) up to 6 months prior to screening * Screening genotype report must show sensitivity to elvitegravir, emtricitabine, tenofovir DF * Normal electrocardiogram (ECG) * Estimated glomerular filtration rate (eGFR) ≥ 50 mL/min according to the Cockcroft-Gault formula for creatinine clearance * Hepatic transaminases (AST and ALT) ≤ 5 × upper limit of normal (ULN) * Total bilirubin ≤ 1.5 mg/dL, or normal direct bilirubin * Adequate hematologic function * Serum amylase ≤ 5 × ULN * Males and 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 * Females 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 * Females 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 Key Exclusion Criteria: * A new AIDS-defining condition diagnosed within the 30 days prior to screening * Hepatitis B surface antigen (HBsAg) positive * Hepatitis C antibody positive * Individuals 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 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 individual unsuitable for the study or unable to comply with dosing requirements * Participation in any other clinical trial (including observational trials) without prior approval * Receiving ongoing therapy with drugs not to be used with elvitegravir, cobicistat, emtricitabine, tenofovir DF, and TAF or participants with any known allergies to the excipients of E/C/F/TDF or E/C/F/TAF Note: Other protocol defined Inclusion/Exclusion criteria may apply.