Tenofovir and emtricitabine concentrations in hair are comparable between individuals on tenofovir disoproxil fumarate versus tenofovir alafenamide-based ART.

Tenofovir disoproxil fumarate (TDF) in combination with emtricitabine (FTC) is the backbone for both human immunodeficiency virus (HIV) treatment and pre-exposure prophylaxis (PrEP) worldwide. Tenofovir alafenamide (TAF) with FTC is increasingly used in HIV treatment and was recently approved for PrEP among men-who-have-sex-with-men. TDF and TAF are both metabolized into tenofovir (TFV). Antiretrovirals in plasma are taken up into hair over time, with hair levels providing a long-term measure of adherence. Here, we report a simple, robust, highly sensitive, and validated high-performance liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS)-based analytical method for analyzing TFV and FTC from individuals on either TDF/FTC or TAF/FTC in small hair samples. TFV/FTC are extracted from ~5 mg hair and separated on a column using a gradient elution. The lower quantification limits are 0.00200 (TFV) and 0.0200 (FTC) ng/mg hair; the assay is linear up to 0.400 (TFV) and 4.00 (FTC) ng/mg hair. The intra-day and inter-day coefficients of variance (CVs) are 5.39-12.6% and 6.40-13.5% for TFV and 0.571-2.45% and 2.45-5.16% for FTC. TFV concentrations from participants on TDF/FTC-based regimens with undetectable plasma HIV RNA were 0.0525 ± 0.0295 ng/mg, whereas those from individuals on TAF/FTC-based regimens were 0.0426 ± 0.0246 ng/mg. Despite the dose of TFV in TDF being 10 times that of TAF, hair concentrations of TFV were not significantly different for those on TDF versus TAF regimens. Pharmacological enhancers (ritonavir and cobicistat) did not boost TFV concentrations in hair. In summary, we developed and validated a sensitive analytical method to analyze TFV and FTC in hair and found that hair concentrations of TFV were essentially equivalent among those on TDF and TAF.

Probenecid-Boosted Tenofovir: A Physiologically-Based Pharmacokinetic Model-Informed Strategy for On-Demand HIV Preexposure Prophylaxis.

Multiple doses of tenofovir disoproxil fumarate (TDF) together with emtricitabine is effective for HIV preexposure prophylaxis (PrEP). TDF is converted to tenofovir (TFV) in circulation, which is subsequently cleared via tubular secretion by organic ion transporters (OATs; OAT1 and OAT3). Using in vitro kinetic parameters for TFV and the OAT1 and OAT3 inhibitor probenecid, a bottom-up physiologically-based pharmacokinetic model was successfully developed for the first time that accurately describes the probenecid-TFV interaction. This model predicted an increase in TFV plasma exposure by 60%, which was within 15% of the observed clinical pharmacokinetic data, and a threefold decrease in renal cells exposure following coadministration of a 600 mg TDF dose with 2 g probenecid. When compared with multiple-dose regimens, a single-dose probenecid-boosted TDF regimen may be effective for HIV PrEP and improve adherence and safety by minimizing TFV-induced nephrotoxicity by reducing TFV accumulation in renal cells.

Inhibitory Effects of Probenecid on Pharmacokinetics of Tenofovir Disoproxil Fumarate and Emtricitabine for On-Demand HIV Preexposure Prophylaxis.

In a randomized, crossover pharmacokinetic study in healthy volunteers (N = 14), a single dose of 2 g probenecid (PRO)-boosted 600 mg tenofovir disoproxil fumarate (TDF)/400 mg emtricitabine (FTC) (test (T) +PRO) was compared with the current on-demand HIV preexposure prophylaxis from the IPERGAY study (a 600 mg TDF/400 mg FTC on day 1 and 300 mg TDF/200 mg FTC on days 2 and 3) (control, C IPERGAY). PRO increased mean single-dose area under the plasma concentration-time curve extrapolated to infinity (AUC0-∞,SD ) of tenofovir (TFV) and FTC by 61% and 68%, respectively. The TFV-diphosphate (TFV-DP) concentrations in peripheral blood mononuclear cells were higher (~30%) at 24 hours in T +PRO but then fell significantly lower (~40%) at 72 hours compared with C IPERGAY. The interaction between FTC and PRO was unexpected and novel. Further study is needed to determine if this PRO-boosted TDF/FTC regimen would be clinically effective.

HIV Antiretroviral Pre-Exposure Prophylaxis: Development Challenges and Pipeline Promise.

The US Food and Drug Administration (FDA) approved oral daily tenofovir/emtricitabine (Truvada) for pre-exposure prophylaxis of human immunodeficiency virus (HIV) infection in 2012 on the basis of two randomized controlled trials (RCTs), one in men who have sex with men (MSM) and another in HIV serodiscordant heterosexual couples. Subsequently, even greater efficacy has been demonstrated in MSM with rapid population-level incidence reductions in some locations. In contrast, studies of antiretroviral pre-exposure prophylaxis (PrEP) in heterosexual women showed only modest or no efficacy, largely attributed to low adherence. The mixed results of antiretroviral-based PrEP bear witness to unique drug development challenges at this complicated intersection of sexual behavior, public health, and drug development. Multiple innovative methods and formulation strategies followed to address unmet medical needs of persons struggling with daily oral PrEP adherence or preference for nonsystemic PrEP options. Clinical pharmacology plays essential roles throughout this PrEP development process, especially in early product development and through pharmacologically informed enhancement and interpretation of clinical trials.

Short Communication: Bioequivalence of Tenofovir and Emtricitabine After Coencapsulation with the Proteus Ingestible Sensor.

Adherence to tenofovir disoproxil fumarate/emtricitabine (TDF/FTC, Truvada®) is the primary determinant of HIV pre-exposure prophylaxis (PrEP) efficacy. Despite its importance, limitations exist in current methods of adherence quantification, restricting their implementation in the clinic. Proteus Discover (Proteus Digital Health®) can measure the time of each dose using an ingestible sensor that is coencapsulated with medication. In this study, the bioequivalence of coencapsulated TDF/FTC with the Proteus sensor was compared relative to unencapsulated drug. This was a 1:1 randomized cross-over study in which healthy participants received a single dose of unencapsulated and coencapsulated TDF/FTC. A 14-day washout separated each period. Blood was collected at predose and at 0.25, 0.5, 1, 2, 4, 6, 10, 24, 48, and 72 h postdose. Plasma concentrations were determined by LC-MS/MS methods, with a 10 ng/mL lower limit of quantitation (LLOQ) for both tenofovir (TFV) and FTC. Noncompartmental analysis was carried out with Phoenix® WinNonlin® for maximum concentrations (Cmax), area under the concentration-time curve from time 0 to the last measured time point (AUClast) and AUC extrapolated to infinity (AUCinf). Geometric mean ratios were calculated for each parameter and bioequivalence was defined as the 90% confidence interval (CI) of each ratio being within 80%-125%. Twenty-four participants (11 males; 19 white, 3 African American, and 2 Hispanic) completed both visits. Mean ± SD age was 28 ± 4 years and weight was 74 ± 14 kg. The 90% CIs for TFV Cmax, AUClast, and AUCinf were 89%-119%, 94%-111%, and 96%-111%, respectively. The 90% CIs for FTC Cmax, AUClast, and AUCinf were 96%-120%, 96%-108%, and 96%-108%, respectively. Bioequivalence was observed for the coencapsulation of TDF/FTC with the Proteus ingestible sensor, as assessed by a rigorously conducted pharmacokinetic study. Future studies will evaluate the utility and effectiveness of the sensor system as a tool to monitor PrEP adherence in clinical settings.

A case study of chewed Truvada® for PrEP maintaining protective drug levels as measured by a novel urine tenofovir assay.

Emtricitabine/tenofovir disoproxil fumarate (FTC/TDF; Truvada®) given as pre-exposure prophylaxis (PrEP) successfully blocks HIV when taken once daily prior to potential HIV exposure. A 22-year-old male reported difficulty swallowing FTC/TDF for PrEP and subsequently began chewing the FTC/TDF tablets. Monthly urine samples assessed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) indicated tenofovir levels >1,000 ng/ml, indicative of protection from HIV acquisition, over a 48-week period. Data from observational studies of HIV-positive patients details the successful treatment of HIV using crushed FTC/TDF delivered via feeding and gastronomy tubes while small, randomized trials of healthy volunteers demonstrate bioequivalence between whole and crushed FTC/TDF.

Comparative bioavailability of two tablet formulations of emtricitabine/tenofovir in healthy, fasting volunteers: a single-dose, randomized-sequence, open-label crossover study.

OBJECTIVE: To evaluate the relative bioavailability of a new formulation of emtricitabine (EMT) 200 mg and tenofovir disoproxil fumarate (TNF) 300 mg and to compare with reference formulation to meet regulatory criteria in Argentina. METHODS: A randomized-sequence, open-label, twoperiod crossover study was conducted on 24 healthy Caucasian volunteers in a fasting state. A single oral dose of T or R formulations was followed by a 7-day washout period. Samples were collected at baseline, 0.25, 0.50, 0.75, 1, 1.25, 1.5, 2, 2.5, 3, 4, 7, 12, 24, and 48 hours after administration. EMT and TNF were determined by LC-MS/MS. RESULTS: Geometric means (90% CI) Cmax for EMT in test and reference were 1,891.22 (1,777.1 - 2,187.31) and 1,830.31 (1,721.19 - 2,134.01) ng/mL, the AUC0-t were 10,283.07 (9,624.29 - 11,566.34) and 10,518.76 (9,942.79 - 11,578.30) ng × h/mL and the AUC0-∞ were 10,615.14 (9,948.56 - 11,866.26) and 10,804.12 (10,221.04 - 11,864.85) ng × h/mL, respectively. For TNF test and reference, Cmax geometric means (CI range) were 202.91 (187.91 - 255.78) and 212.04 (195.98 - 264.87) ng/mL, AUC0-t were 1,429.96 (1,334.63 - 1,680.00) and 1,420.75 (1,326.76 - 1,622.18) ng × h/mL and AUC0-∞ were 1,657.11 (1,551.60 - 1,921.75) and 1,631.84 (1,523.95 - 1,857.97), respectively. No differences were detected between the formulations. The test/reference ratios (90% CI) for Cmax, AUC0-t, and AUC0-∞ were 103.33% (95.7 - 111.6), 97.76% (93.6 - 102.1), and 98.25% (94.3 - 102.4) for EMT, and 95.70% (85.9 - 106.6), 95.20% (83.4 - 108.6) and 91.10% (80.7 - 102.7) for TNF. CONCLUSIONS: In this single-dose study, the EMT/TNF tablets (test formulation) met the standard 90% CI criterion for bioequivalence with the reference formulation.

Reporting of Adherence in the VOICE Trial: Did Disclosure of Product Nonuse Increase at the Termination Visit?

VOICE-a phase 2B, placebo-controlled, randomized trial testing daily use of an antiretroviral tablet (tenofovir or Truvada) or daily use of tenofovir gel in 5029 women from South Africa, Uganda, and Zimbabwe-found none of the drug regimens effective in reducing HIV-1 acquisition in the intent-to-treat analysis. More than half of women assigned to active products in a case cohort sample had no drug detected in any plasma specimens tested during the trial. Yet, in response to questions asked of participants during the trial, ≥90 % of doses were reportedly taken. To explore factors associated with low adherence, a behavioral termination visit questionnaire was developed after early closure of the oral tenofovir and vaginal gel arms. We hypothesized that participants would be more forthcoming about nonuse after they exited the trial than during monthly/quarterly follow-up visits. Comparison of adherence reporting at routine follow-up visits with reporting at trial termination, however, indicates that disclosure of product nonadherence did not increase at the termination visit as anticipated. In resource-limited settings where women value the ancillary benefits provided by trial participation and are concerned that disclosure of nonuse may jeopardize trial participation, objective measures of adherence may yield more meaningful data regarding the inability or reluctance to use than measures of product use derived from self-report.