Elvitegravir (EVG) Cerebrospinal Fluid (CSF) Pharmacokinetics in HIV-Infected Individuals

The project will have two tracks, one for participants who are currently taking elvitegravir/cobicistat/emtricitabine/tenofovir disoproxil fumarate or E/C/F/tenofovir alafenamide (E/C/F/TDF or E/C/F/TAF) single-tablet regimen\* (STR) (Track A) and one for participants who will begin therapy with E/C/F/TDF or E/C/F/TAF STR during the study (Track B). Participants will take E/C/F/TDF and/or E/C/F/tenofovir alafenamide fumarate (E/C/F/TAF) STR\*\* (if available) for 24 weeks. \*Co-formulation of 150 mg of elvitegravir, 150 mg of cobicistat, 200 mg of emtricitabine, and 300 mg of tenofovir disoproxil fumarate. \*\*Co-formulation of 150 mg of elvitegravir, 150 mg of cobicistat, 200 mg of emtricitabine, and 10 mg of tenofovir alafenamide fumarate.