Phase 3 Open-Label Study to Evaluate Switching From Optimized Stable Antiretroviral Regimens Containing Darunavir to Elvitegravir/Cobicistat/Emtricitabine/Tenofovir Alafenamide (E/C/F/TAF) Fixed Dose Combination (FDC) Plus Darunavir (DRV) in Treatment Experienced HIV-1 Positive Adults

Key Inclusion Criteria:

- Ability to understand and sign a written informed consent form

- History of at least two prior antiretroviral regimens, and history of resistance to at
least two different classes of antiretroviral agents

- Plasma HIV-1 RNA levels < 50 copies/mL at screening. Virologically suppressed on the
current antiretroviral regimen containing darunavir 600 mg twice a day or 800 mg once
daily continuously for ≥ 4 months preceding the screening visit and have maintained
documented undetectable plasma HIV-1 RNA levels (< 50 copies/mL) and must have
documentation of genotype/phenotype prior to current regimen which shows no darunavir
associated resistance mutation.

- Currently receiving raltegravir, elvitegravir, or dolutegravir (50 mg once daily, but
not twice daily), or have never received integrase inhibitor, or have documentation of
genotype/phenotype within 12 months prior to current regimen which must show no
evidence of resistance to integrase inhibitors

- Normal 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 (absolute neutrophil count ≥ 1,000/mm^3; platelets ≥
50,000/mm^3; hemoglobin ≥ 8.5 g/dL)

- Serum amylase ≤ 5 × ULN (individuals with serum amylase > 5 × ULN will remain eligible
if serum lipase is ≤ 5 × ULN)

- A female individual is eligible to enter the study if it is confirmed that she is:

- Not pregnant or nursing

- Of non-childbearing potential (i.e., women who have had a hysterectomy, have had
both ovaries removed or medically documented ovarian failure, or are
postmenopausal women > 54 years of age with cessation (for ≥ 12 months) of
previously occurring menses), or

- Of childbearing potential and agrees 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 study drug dose.

- Female individuals 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.

- Male individuals must agree to utilize a highly effective method of contraception
during heterosexual intercourse or be non-heterosexually active, or practice sexual
abstinence from first dose throughout the study period and for 30 days following the
last study drug dose.

- Male individuals must agree to refrain from sperm donation from first dose until at
least 30 days after the last study drug dose.

Key Exclusion Criteria:

- A new AIDS-defining condition diagnosed within the 30 days prior to screening (except
CD4 cell count and/or percentage criteria)

- Hepatitis B surface antigen (HBsAg) positive

- Individuals receiving drug treatment for Hepatitis C, or individuals who are
anticipated to receive treatment for Hepatitis C during the course of the study.

- Must not have Q151M, T69ins, or > 3 thymidine analogue mutations (TAMS) present on
documented historic genotype report

- Individuals experiencing decompensated cirrhosis

- Females who are breastfeeding

- Positive serum pregnancy test

- Have an implanted defibrillator or pacemaker

- Current alcohol or substance use that may interfere with individual's study compliance

- A history of malignancy within the past 5 years or ongoing malignancy other than
cutaneous Kaposi's sarcoma (KS), basal cell carcinoma, or resected, non-invasive
cutaneous squamous carcinoma.

- Active, serious infections (other than HIV-1 infection) requiring parenteral
antibiotic or antifungal therapy within 30 days prior to Day 1 visit

- Any other clinical condition or prior therapy that 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 from the sponsor is prohibited while participating in this trial

- Individuals receiving ongoing therapy with any of the disallowed medications,
including drugs not to be used with elvitegravir, cobicistat, emtricitabine, TAF, or
DRV; or individuals with any known allergies to the study drugs.

Note: Other protocol defined Inclusion/Exclusion criteria may apply.