The study seeks to define the expected blood levels of pre-exposure prophylaxis (PrEP) medications (tenofovir) for cisgender women taking directly observed oral PrEP therapy to understand the frequency of PrEP dosing associated with HIV protection in cisgender women. Cisgender women will be randomly assigned to receive varying frequencies of weekly PrEP doses and followed for up to 16 weeks. The study will also investigate how pregnancy affects the expected blood levels to help define optimal dosing of PrEP for HIV prevention during pregnancy.

This is an open-label, randomized, three-arm, directly observed therapy (DOT) study. HIV-uninfected non-pregnant cisgender women at low risk for HIV acquisition will be randomly assigned to 1 of 3 dosing frequencies of DOT with Tenofovir Disoproxil Fumarate/Emtricitabine (TDF/FTC) oral PrEP to help differentiate poor and moderate from perfect dosing. An additional cohort of pregnant women at high risk of HIV acquisition will be recruited and will receive daily dosing of TDF/FTC oral PrEP to evaluate the impact of pregnancy on blood and cellular drug levels. Study participants will receive directly observed oral PrEP for eight weeks, and will be followed for an additional eight weeks after their final PrEP dose. Drug concentrations in blood, vaginal fluid, and tissue will be measured during the study. The primary objectives of the study are:

1. To define expected blood concentrations and dose-proportionality specific to cisgender women for tenofovir-diphosphate (TFV-DP) in dried blood spots (DBS) and peripheral blood mononuclear cells (PBMCs) using directly observed therapy of TDF/FTC at 2, 4, and 7 doses per week, representing poor, moderate, and perfect adherence, respectively.
2. To establish a model to predict adherence rate to TDF/FTC by level of TFV-DP observed in DBS for cisgender women. HIV-uninfected non-pregnant cisgender women will be randomly assigned to 1 of 3 dosing frequencies of directly observed therapyt of TDF/FTC oral PrEP: 2, 4, or 7 doses/week to differentiate poor and moderate from perfect adherence.

The study is the first to define TDF/FTC PrEP adherence-blood concentration thresholds for African cisgender women, a priority population for HIV prevention. The findings will guide accurate interpretation of adherence and success of PrEP programs in cisgender women. This data will also help guide decisions on optimal PrEP dosing for pregnant cisgender women at risk of acquiring HIV in Africa.

Inclusion Criteria:

• Age ≥18 and ≤30 years old
• Willing to undergo urine pregnancy tests
• Has understood the information provided and has provided written informed consent before any study-related procedures are performed.
• HIV uninfected based on negative HIV rapid tests, according to Kenyan national algorithm
• Normal renal function (estimated glomerular filtration rate >60 mL/min)
• Hepatitis B surface Ag negative
• No active clinically significant medical or psychiatric conditions that would interfere with study participation
• Lack of severe anemia
• Willing to use DOT and come to clinic frequently for DOT PrEP for at least 8 weeks
• Willing to have home visits for follow up
• Has access to an active smartphone to allow off-site observation of dosing if unable to come to the clinic or as determined by the study staff, the participant resides in close location to clinic to permit home visit if unable to come to the clinic. i.e., potential participants without a smartphone may be enrolled in the study if investigator determines that the participant resides within reasonable distance from the clinic that would permit home visit id the participant misses their visit.
• Intention to stay within the study site's catchment area for at least 8 weeks.
• Resides or works in catchment area with high speed internet coverage to permit video streaming

Specific for non-pregnant cisgender women cohort

• Not pregnant or breast feeding
• At low risk for HIV. In Kenya, national guidelines define substantial risk for HIV and recommend PrEP be an option for individuals reporting: partner of HIV-infected person not on ART or on ART for <6 months, >1 partner of unknown status, transactional sex, recent STI, recurrent PEP use, inconsistent condom use, or injection drug use. So, non-pregnant cisgender women reporting any of these factors will not be eligible for the study but will be linked for PrEP at clinic of choice including at Thika Site itself.
• Willing to be randomized to non-daily PrEP and come to clinic frequently for DOT PrEP
• Willingness and ability to be abstinent for at least 7 days after each vaginal biopsy visit.

Specific for pregnant cisgender women only

• At screening, evidence of a viable pregnancy with gestational age of 13-26 weeks after the date of conception with sonographic confirmation. If adequate sonographic results are not available from medical records at screening, an ultrasound must be performed in the interim so that the result is available at study entry.
• At elevated risk for acquiring HIV according to Kenya guideline for PrEP. This is to ensure an ethical approach for provision of PrEP in pregnancy (i.e., only exposing PrEP to those who want and might benefit from it). Kenya national guidelines define substantial risk for HIV and recommend PrEP be an option for individuals reporting partner of HIV-infected person not on ART or on ART for <6 months, >1 partner of unknown status, transactional sex, recent STI, recurrent PEP use, no or inconsistent condom use
• At study entry, willing to use PrEP during pregnancy for HIV prevention

Exclusion Criteria:

• For all cisgender women
• Inability to give informed consent
• Positive screening HIV+ as determined by standard rapid serologic assays 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)
• Positive HBV surface antigen test at screening
• Calculated creatinine clearance < 60 ml/min.
• 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.
• 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 TAF®, ATRIPLA®, COMPLERA®, EMTRIVA®, VIREAD®; or drugs containing lamivudine or adefovir, which are close analogs of FTC and tenofovir, respectively.
• Current or past use of PrEP (pre-exposure prophylaxis)
• Not willing to have home visits

Specific for non-pregnant cisgender women cohort

• Pregnancy or plan to become pregnant in the next 6 months or unwillingness to use birth control
• Current breastfeeding
• High risk of HIV infection (for example: sexually active with an HIV infected partner; engages in condomless intercourse with HIV-infected partners or partner of unknown status during the study; 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.

Specific for pregnant cisgender women cohort

• Mother has a known history of any of the following, as determined by the site investigator or designee based on maternal report and available medical records:
• Sickle cell anemia (excluding sickle cell trait), chronic bleeding, blood transfusion within the past 120 days (excluding for chronic illness) or other blood dyscrasias
• Fetus has a known or suspected major congenital anomaly, from chart review of prior data, defined ultrasound.
• Complications in prior pregnancies that would be considered exclusionary

Adverse event data for each participant was collected over the eight weeks between randomization (i.e., administration of the first dose of study product) and administration of the final dose of study product at the end of the directly observed therapy (DOT) phase.

Adverse events meeting the following criteria were recorded: Clinical AEs of Grade 1 and above, laboratory AEs of Grade 2 and above, all AEs (clinical or laboratory) leading to a study product hold (temporary or permanent)

1. Dosing of TDF/FTC was up to 8 weeks which is about 90% of TFV-DP steady-state in DBS. However, pharmacokinetic modeling enabled steady-state estimates.
2. Assessment of drug concentrations in PBMCs is highly dependent on cell processing and count protocols, meaning that it is difficult to compare PBMCs results across laboratories and studies.
3. The study focused on the adherence-concentration thresholds but did not explicitly evaluate the concentration-efficacy relationship.