Adherence to daily dosing is very important for how well Emtricitabine/Tenofovir Alafenamide (F/TAF) works for treatment of chronic human immunodeficiency virus (HIV), or prevention of HIV acquisition. Methods to measure medication adherence to Tenofovir disoproxil fumarate (tenofovir DF, TDF), a similar but different prodrug of tenofovir, have been developed but cannot be extrapolated to F-TAF. By measuring F-TAF (the drug) and metabolites in the blood cells and dried blood spots, the study plans to see if these results predict adherence to taking the drug. The goal of this study is to vary the amount of F-TAF dosing and see if the drug levels in dried blood spots (DBS) change in a predictable way. This study will mimic different levels of adherence (33%, 67%, and 100% of daily dosing) using directly observed therapy (DOT) to establish the relationship between F-TAF in dried blood spots and adherence. Investigators will also measure drug in hair clippings to see if hair or DBS are a better predictor of adherence.

Inclusion Criteria:

1. Ambulatory 18-59 year old adults. Enrollment will proceed without the need to meet specific race/gender targets, but balanced gender and African-Americans and Latino representation will be sought.
2. Ability to comply with study procedures, including directly observed dosing visits and availability and use of video streaming technology.

Exclusion Criteria:

1. Inability to give informed consent

2. Pregnancy or plan to become pregnant in the next 12 months or unwillingness to use birth control

3. Current breastfeeding

4. High risk of HIV-1 infection, for example:

   • sexually active with an HIV infected partner;
   • men who have sex with men who may engage in condomless intercourse with HIVinfected partners, or
   • partner of unknown status during the study;
   • males or females who exchange sex for money, shelter, or gifts;
   • active injection drug use or during the last 12 months;
   • newly diagnosed sexually transmitted infections in last 6 months

5. Positive screening HIV+ ELISA or suspected acute HIV infection in the opinion of the clinician. Example signs and symptoms of acute HIV infection include combinations of:

   • fever,
   • headache,
   • fatigue,
   • arthralgia,
   • vomiting,
   • myalgia, .
   • diarrhea,
   • pharyngitis,
   • rash,
   • night sweats, and
   • adenopathy (cervical or inguinal)

6. Positive Hepatitis B Virus (HBV) surface antigen test at screening

7. Active psychiatric illness, social condition, or alcohol/drug abuse that, in the opinion of the investigators, would interfere with study requirements.

8. Glomerular Filtration Rate (GFR) estimate < 60 ml/min (MDRD equation).

9. Urine dipstick protein ≥ 2+

10. Total bilirubin and/or hepatic transaminases (ALT and AST) ≥ 2.5x upper limit of normal

11. Absolute neutrophil count ≤ 1,500/mm3, platelets count ≤ 100,000/mm3, or hemoglobin ≤ 10 g/dL.

12. Symptomatic hemoglobinopathies or active hemolysis.

13. History of pathological, non-traumatic bone fractures

14. Any laboratory value or uncontrolled medical conditions that, in the opinion of the investigators, would interfere with the study conditions such as, heart disease and/or cancer.

15. Prohibited concomitant medications are:

    • investigational agents (within 30 days of enrollment),
    • aminoglycosides,
    • ganciclovir/valganciclovir,
    • chronic high-dose acyclovir/valacyclovir (>800mg acyclovir or > 500mg valacyclovir for 7 days),
    • cyclosporine, amphotericin B, foscarnet, and cidofovir, and products with same or similar active ingredients as the study medications including TRUVADA®, ATRIPLA®, COMPLERA®, EMTRIVA®, VIREAD®; or drugs containing lamivudine or adefovir, which are close analogs of FTC and tenofovir, respectively.

Baseline characteristics are not stratified based on dosing regimen. Dosing Arms were combined, regardless of dosing regimen order (i.e. all 33%, regardless if 33% regimen followed by other regimen (100% or 67%), or other regimen (100% or 67%) followed by 33%) to be consistent with data collection, protocol subject randomization and journal publications. Combined arms best categorize the study, population, and data.

Time of consenting to study exit (Week 36 or earlier), Max 10 months.

AEs were graded per the DAIDS Table for Grading the Severity of Adult and Pediatric Adverse Events, Version 2.0, November, 2014. Available: http://rsc.tech-res.com/safetyandpharmacovigilance/.

Arms were combined as Descovy was FDA approved for daily use (100% dosing) at the time of study initiation- no arm was considered to be more at risk for AEs than another.