Julie B. Dumond

Antiretroviral drug exposure in the female genital tract: implications for oral pre- and post-exposure prophylaxis

Objectives:To describe first dose and steady state antiretroviral drug exposure in the female genital tract. Design:Non-blinded, single center, open-label pharmacokinetic study in HIV-infected women. Method:Twenty-seven women initiating combination antiretroviral therapy underwent comprehensive blood plasma and cervicovaginal fluid sampling for drug concentrations during the first dose of antiretroviral therapy and at steady-state. Drug concentrations were measured by validated HPLC/UV or HPLC-MS/MS methods. Pharmacokinetic parameters were estimated for 11 drugs by non-compartmental analysis. Descriptive statistics and 95% confidence intervals were generated using Intercooled STATA Release 8.0 (Stata Corporation, College Station, Texas, USA). Results:For all antiretroviral drugs, genital tract concentrations were detected rapidly after the first dose. Drugs were stratified according to the genital tract concentrations achieved relative to blood plasma. Median rank order of highest to lowest genital tract concentrations relative to blood plasma at steady state were: lamivudine (concentrations achieved were 411% greater than blood plasma), emtricitabine (395%), zidovudine (235%) tenofovir (75%), ritonavir (26%), didanosine (21%), atazanavir (18%), lopinavir (8%), abacavir (8%), stavudine (5%), and efavirenz (0.4%). Conclusions:This is the first study to comprehensively evaluate antiretroviral drug exposure in the female genital tract. These findings support the use of lamivudine, zidovudine, tenofovir and emtricitabine as excellent pre-exposure/post-exposure prophylaxis (PrEP/PEP) candidates. Atazanavir and lopinavir might be useful agents for these applications due to favorable therapeutic indices, despite lower genital tract concentrations. Agents such as stavudine, abacavir, and efavirenz that achieve genital tract exposures less than 10% of blood plasma are less attractive PrEP/PEP candidates.

Maraviroc Concentrates in the Cervicovaginal Fluid and Vaginal Tissue of HIV-Negative Women

Objective:To compare single- and multiple-dose maraviroc exposures in cervicovaginal fluid (CVF) and vaginal tissue (VT) with blood plasma (BP) and quantify maraviroc protein binding in CVF. Design:Open-label pharmacokinetic study. Methods:In 12 HIV-negative women, 7 paired CVF and BP samples were collected over 12 hours after 1 maraviroc dose. Subjects then received maraviroc twice daily for 7 days. After the last dose, subjects underwent CVF and BP sampling as on day 1, with additional sampling during terminal elimination. VT biopsies were obtained at steady state. Results:Day 1 and day 7 median maraviroc CVF AUCτ were 1.9- and 2.7-fold higher, respectively, than BP. On day 1, 6 of 12 subjects had detectable maraviroc CVF concentrations within 1 hour; 12 of 12 were detectable within 2 hours, and all exceeded the protein-free IC90. On day 7, maraviroc CVF protein binding was 7.6% and the VT AUCτ was 1.9-fold higher than BP. Maraviroc CVF concentrations 72 hours after dose and BP concentrations 12 hours after dose were similar. Conclusions:Higher maraviroc exposure in the female genital tract provides a pharmacologic basis for further evaluation of chemokine receptor 5 antagonists in HIV infection prophylaxis. This is the first study to report antiretroviral VT concentrations, CVF protein binding, and CVF terminal elimination.

Single and Multiple Dose Pharmacokinetics of Maraviroc in Saliva, Semen, and Rectal Tissue of Healthy HIV-Negative Men

BACKGROUND Antiretroviral pharmacology in seminal plasma (SP) and rectal tissue (RT) may provide insight into antiretroviral resistance and the prevention of sexual transmission of human immunodeficiency virus (HIV). Saliva may be of utility for noninvasively measuring adherence. METHODS A pharmacokinetic study was performed in 12 HIV-negative men receiving maraviroc 300 mg twice daily for 8 days. Seven time-matched pairs of blood plasma (BP) and saliva samples were collected over 12 h on day 1 (PK1) and days 7 and 8 (PK2). One RT sample from each subject was collected during PK1 and PK2. Two SP samples were collected from each subject during PK1, and 6 SP samples were collected from each subject during PK2. RESULTS SP AUCs were ∼50% lower than BP. However, protein binding in SP ranged from 4% to 25%, resulting in protein-free concentrations >2-fold higher than BP. RT AUCs were 7.5- to 26-fold higher than BP. Maraviroc saliva AUCs were ∼70% lower than BP, but saliva concentrations correlated with BP (r(2) = 0.58). CONCLUSIONS More pharmacologically available maraviroc was found in SP than BP. High RT concentrations are promising for preventing rectal HIV acquisition. Saliva correlation with BP suggests that this may be useful for monitoring adherence. CLINICAL TRIALS REGISTRATION NCT00775294.

Pre-exposure prophylaxis for HIV prevention: how to predict success.

Use of antiretroviral drugs to prevent sexual transmission of HIV-1 has been a critical priority since their development. In the past 2 years results from seven important prevention trials have been reported (table). One of the trials, HPTN 052,1 showed nearly complete prevention of HIV transmission when viraemia was suppressed. The other studies focused on antiretroviral agents for pre-exposure prophylaxis: two used 1% tenofovir gel (CAPRISA 0042 and VOICE3), four used oral tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC) in combination (iPrEX,4 TDF2,5 Partners in Prevention [PIP],6 and Fem-PrEP7), and two used oral TDF alone (VOICE3 and PIP6). Somewhat confusingly, the findings of these studies have led to reports both of successful prevention of HIV infection (CAPRISA 004,2 iPrEx,4 TDF2,5 and PIP6) and of futility (VOICE3 and Fem-PrEP7). Table Antiretroviral-based HIV prevention studies Clearly, results on pre-exposure prophylaxis will be used to inform policy and to plan future research, and so the trials’ findings need to be considered carefully. There were key differences in the pre-exposure prophylaxis trials (table): each included different populations with distinct routes of HIV transmission. For example, iPrEx4 was the first success for oral pre-exposure prophylaxis and focused on men who have sex with men. It is reasonable to assume that anal intercourse was the key route of transmission in the iPrEx trial,4 and was less frequently the source of HIV infection in the heterosexual women and men in the Fem-PrEP,7 VOICE,3 TDF2,5 and PIP6 studies. HIV acquisition is more efficient after anal intercourse,8 and more HIV variants are acquired during anal intercourse than cervicovaginal exposure.9 We have reported substantial differences in anti-retroviral drug concentrations in mucosal tissues.10–12 After oral administration of co-formulated TDF and FTC, there were 100-fold higher concentrations of tenofovir in rectal tissue compared with cervicovaginal tissue.12 Intracellularly phosphorylated tenofovir (TFV-DP) and emtricitabine (FTC-TP) are required to inhibit HIV replication.12 100-fold higher concentrations of TFV-DP were detected in the rectum as compared with cervix and vagina.12 Conversely, FTC-TP concentrations were 10–15 fold higher in vaginal and cervical tissue than in rectal tissue. Although we do not know the concentrations of TFV-DP and FTC-TP required to prevent HIV infection, the differences in tissue concentrations are substantial and suggest implications for HIV prevention. In the VOICE trial,3 the lack of protection with oral TDF could reflect low tissue concentrations of the drug. How, then, can we explain the protection provided by TDF in PIP6? It seems possible that HIV transmission in a discordant couple relationship might be prevented differently, or more readily. It is also possible, indeed likely, that adherence in a discordant relationship is better, resulting in a critical (currently unknown) tissue concentration being achieved. The protection from HIV observed with the TDF and FTC combination in TDF25 and PIP6 suggests an important role for higher FTC concentrations, perhaps in combination with the lower concentrations of tenofovir, in the female genital tract. The differences in benefit of 1% tenofovir gel in CAPRISA 0042 and VOICE3 demand further exploration; the studies used different dosage schedules, and women at different sites might differ in ways that affect study outcomes (table). Adherence, however, will still determine the value of antiretroviral agents both in clinical trials and in clinical practice. In HPTN 0521 HIV viraemia was prospectively monitored in infected trial participants to ensure adherence, which allowed determination of the antiretrovirals’ ability to suppress transmission under ideal conditions. To date, the only prospective measurement of adherence in pre-exposure prophylaxis trials has been by self-report or pill counts, which might overestimate adherence.13 These values have then been compared to potential efficacy with post-hoc measurement of blood concentrations in a limited number of samples using a case-control design. In the iPrEx trial,4 the investigators used combined data to argue that pre-exposure prophylaxis was perhaps more than 90% protective in participants who took the treatment reliably. In CAPRISA 004,2 the effectiveness of protection was 52% with more than 80% adherence as measured retrospectively by evaluation of used gel applicators. But such retrospective analyses cannot be used to confirm the intervention’s success or failure. Less adherence to daily use of 1% tenofovir gel in VOICE3 could have compromised benefit relative to the coitally-driven use of the gel in CAPRISA 004.2 Paradoxically, daily use may confer a degree of difficulty that reduces adherence. We believe that, before future pre-exposure prophylaxis studies are undertaken, knowledge of biological plausibility must be secure. Evidence of strong and durable tissue concentrations of active agents should be a condition of such studies taking place. Powerful antiviral agents limited in their tissue penetration, intracellular metabolism, or tissue half-life are not appropriate for pre-exposure prophylaxis. Moreover, adherence must be measured prospectively in future trials.14,15 Under these conditions trial participants who do not adhere to treatment can be counselled or the study analysis designed to incorporate these most rigorous measures of adherence. To predict success in clinical practice reliably, both the drug concentrations needed for protective efficacy and the best way to assess adherence in clinical trials must first be defined. Effectiveness trials that depend on adherence and many other factors—the real world—should await proof that antiretroviral agents work as anticipated.

Genital Tract, Cord Blood, and Amniotic Fluid Exposures of Seven Antiretroviral Drugs during and after Pregnancy in Human Immunodeficiency Virus Type 1-Infected Women

ABSTRACT The objective of the study was to measure antiretroviral exposures in four physiological compartments during pregnancy, delivery, and postpartum. This prospective, open-label, longitudinal study collected paired blood plasma (BP) and genital tract (GT) aspirates antepartum, at delivery, and up to 12 weeks postpartum. Antiretroviral cord BP and amniotic fluid concentrations were also measured. Drug concentrations were analyzed by validated high-performance liquid chromatography/UV and liquid chromatography/tandem mass spectrometry methods, with secondary compartment concentrations presented as the percentage of BP. Fourteen women taking lamivudine plus zidovudine and either lopinavir-ritonavir (n = 7), nelfinavir (n = 6), or nevirapine (n = 1) were enrolled; four also received tenofovir. GT penetration relative to BP was highest for the nucleoside reverse transcriptase inhibitors compared to the protease inhibitors and nevirapine. Only antepartum nelfinavir GT penetration was significantly higher than in the second trimester (geometric mean ratio [GMR], 179.3) or third trimester (GMR, 41.9). Compared to nonpregnant historical controls, antepartum GT penetration was significantly lower (P < 0.05) for zidovudine (GMR, 0.25) and lopinavir (GMR, 0.03); postpartum lopinavir GT penetration continued to be significantly lower (GMR, 0.27). Cord BP exposures were highest for lamivudine and tenofovir (≥100%), with cord BP levels of the remaining drugs ranging from 49 to 86% of that of the respective BP level. Amniotic exposures for lamivudine, zidovudine, tenofovir, and nelfinavir were ≥100%, nevirapine exposure was 53%, and lopinavir and ritonavir exposures were ≤6% that of BP. We conclude that GT, cord BP, and amniotic fluid exposures vary within and between antiretroviral drug classes and biologic sites. Measurement of antiretroviral exposure in maternal genital secretions, cord BP, and amniotic fluid may be needed to identify signals of subtherapeutic or supratherapeutic drug exposure.

A Phenotype–Genotype Approach to Predicting CYP450 and P‐Glycoprotein Drug Interactions With the Mixed Inhibitor/Inducer Tipranavir/Ritonavir

The effects of tipranavir/ritonavir (TPV/r) on hepatic and intestinal P‐glycoprotein (P‐gp) and cytochrome P450 (CYP) enzyme activity were evaluated in 23 volunteers. The subjects received oral (p.o.) caffeine, warfarin + vitamin K, omeprazole, dextromethorphan, and midazolam and digoxin (p.o. and intravenous (i.v.)) at baseline, during the first three doses of TPV/r (500 mg/200 mg b.i.d.), and at steady state. Plasma area under the curve (AUC)0–∞ and urinary metabolite ratios were used for quantification of protein activities. A single dose of TPV/r had no effect on the activity of CYP1A2 and CYP2C9; it weakly inhibited CYP2C19 and P‐gp; and it potently inhibited CYP2D6 and CYP3A. Multiple dosing produced weak induction of CYP1A2, moderate induction of CYP2C19, potent induction of intestinal P‐gp, and potent inhibition of CYP2D6 and CYP3A, with no significant effects on CYP2C9 and hepatic P‐gp. Several P450/transporter single‐nucleotide polymorphisms correlated with the baseline phenotype but not with the extent of inhibition or induction. Although mixed induction and inhibition are present, this approach offers an understanding of drug interaction mechanisms and ultimately assists in optimizing the clinical use of TPV/r.

Differential Extracellular and Intracellular Concentrations of Zidovudine and Lamivudine in Semen and Plasma of HIV-1–Infected Men

Objectives:To quantitate extracellular and intracellular zidovudine (ZDV) and lamivudine (3TC) concentrations in blood and semen of HIV-1-infected men. Design:Nonblind, single-center, open-label pharmacokinetic (PK) study in 14 subjects receiving ZDV plus 3TC. Methods:Paired blood and semen samples were obtained during 1 intensive visit and 3 single time point visits over 2 weeks. Extracellular ZDV and 3TC concentrations were measured in blood plasma (BP) and seminal plasma (SP), and intracellular ZDV and 3TC triphosphate (TP) concentrations were measured in isolated mononuclear cells using validated methods. HIV-1 RNA was measured in blood and semen. PK parameters were estimated using noncompartmental analysis. Results:Median (interquartile range [IQR]) SP/BP area under the time-concentration curve over the 12-hour dosing interval (AUC0-12h) ratios for ZDV and 3TC were 2.28 (1.48 to 2.97) and 6.67 (4.10 to 9.14), respectively, whereas individual SP/BP concentration ratios ranged from 1.9 to 91.4. Intracellular median (IQR) SP/BP AUC0-12h ratios for ZDV-TP and 3TC-TP were 0.36 (0.30 to 0.37) and 1.0 (0.62 to 1.30), respectively, whereas individual SP/BP concentration ratios ranged from 0.11 to 2.9. HIV-1 RNA was undetectable in both compartments. Conclusions:ZDV and 3TC SP exposures are 2- to 6-fold greater than BP exposures. Seminal ZDV-TP exposures are ∼40% of those found in peripheral blood mononuclear cells (PBMCs), whereas 3TC-TP exposures are similar to PBMC exposures. PK variability makes individual SP/BP ratios a suboptimal surrogate for genital tract exposure.

Dolutegravir pharmacokinetics in the genital tract and colorectum of HIV-negative men after single and multiple dosing

Objectives:To describe first-dose and steady state pharmacokinetics (PKs) of dolutegravir (DTG) in blood plasma (BP), seminal fluid (SF), colorectal tissue (RT), and rectal mucosal fluid (RF) of healthy HIV-negative men. Design:A phase 1, open-label, PK study that enrolled 12 healthy men taking 50 mg DTG daily for 8 days. Methods:Eleven paired BP samples and 3 SF and RF samples were collected over 24 hours after first (PK1) and multiple (PK2) dosing. RT biopsies were collected at 1 of 6 time points at PK1 and PK2 to generate composite PK profiles. DTG concentrations were analyzed by validated liquid chromatography-tandem mass spectrometry (LC-MS/MS). Noncompartmental PK analysis was conducted with Phoenix WinNonlin v6.3, and Spearman rank correlations were determined using SAS v9.3. Results:BP area under the concentration–time curves (AUCs) were similar to previous reports, and concentrations at 24 hours (C24 h) were 6- to 34-fold greater than the protein-adjusted concentration required for 90% viral inhibition (PA-IC90) of 64 ng/mL. SF exposures were <7% of BP and below the PA-IC90. RT exposures were 17% of BP and ∼2-fold greater than the PA-IC90. RF AUCs were ∼2%–5% of RT and did not correlate with RT (rho = 0.43, P = 0.17). Accumulation of DTG with multiple dosing was observed in BP, SF, and RT. Conclusions:DTG BP PKs were consistent with previously published values. SF concentrations were <7% BP, with SF C24 h below the PA-IC90. However, SF protein binding was not measured. Although the AUC of DTG in RT was <20% BP, RT C24 h remained ∼2-fold higher than the PA-IC90. RF was not a strong surrogate for RT concentrations.

Single and multiple dose pharmacokinetics of dolutegravir in the genital tract of HIV-negative women

BACKGROUND Antiretrovirals that achieve adequate concentrations in anatomical sites of transmission are of interest for HIV prevention. A Phase I open-label pharmacokinetic (PK) study was performed to describe first dose (PK1) and steady-state (PK2) PKs of the integrase inhibitor dolutegravir (DTG) in blood plasma (BP), cervicovaginal fluid (CVF), cervical tissue (CT) and vaginal tissue (VT) in HIV type-1-negative women. METHODS A total of 8 healthy females given DTG 50 mg daily for 5-7 days had 11 paired BP and CVF samples collected over 24 h following the first dose (PK1) and multiple dosing (PK2). Each woman underwent CT and VT biopsies at 1/4 time points at PK1 and PK2 to generate composite PK profiles. DTG concentrations were analysed by validated liquid chromatography-tandem mass spectrometry methods. Non-compartmental PK analysis was performed and Spearman rank correlations determined between matrices. RESULTS BP areas under the concentration-time curve (AUCs) were similar to previous reports and concentrations remained greater than the protein-adjusted (PA) 90% inhibitory concentration (IC90) for wild-type HIV (64 ng/ml). CVF exposures were approximately 6% of BP with low inter-individual variability. CT and VT exposures were 7% of BP at PK1, and 9-10% of BP at PK2 with 94% of samples >PA-IC90. CT and VT concentrations were correlated to each other (ρ=0.70, P=0.003), and to CVF at steady state (ρ=0.52, P=0.04). Accumulation of DTG from PK1 to PK2 occurred in BP, CT and VT, but only marginally in CVF. CONCLUSIONS DTG BP PK were consistent with previously published values. CVF, CT and VT exposures were highly correlated. At PK2, DTG accumulated to a greater extent in tissue than in BP or CVF, suggesting increased tissue affinity.

Protein binding of lopinavir and ritonavir during 4 phases of pregnancy: Implications for treatment guidelines

Objective:To investigate the intraindividual pharmacokinetics (PKs) of total (protein bound plus unbound) and unbound lopinavir/ritonavir (LPV/RTV) and to assess whether the pediatric formulation (100 mg/25 mg) can overcome any pregnancy-associated changes. Design:Prospective longitudinal PK study. Methods:HIV-infected pregnant antiretroviral therapy–naive and experienced women receiving LPV/RTV 400 mg/100 mg tablets twice daily. Intensive PK evaluations were performed at 20–24 weeks (PK1), 30 weeks (PK2) followed by empiric dose increase using the pediatric formulation (100 mg/25 mg twice daily), 32 weeks (PK3), and 8 weeks postpartum (PK4). Results:Twelve women completed prespecified PK evaluations. Median (range) age was 28 (18–35) years and baseline BMI was 32 (19–41) kg/m2. During pregnancy, total area under the time concentration (AUC0–12h) for LPV was significantly lower than postpartum (PK1, PK2, or PK3 vs. PK4, P = 0.005). Protein-unbound LPV AUC0–12h remained unchanged during pregnancy [PK1: 1.6 (1.3–1.9) vs. PK2: 1.6 (1.3–1.9) &mgr;g·h/mL, P = 0.4] despite a 25% dose increase [PK2 vs. PK3: 1.8 (1.3–2.1) &mgr;g·h/mL, P = 0.5]. Protein-unbound LPV predose concentrations (C12h) did not significantly change despite dose increase [PK2: 0.10 (0.08–0.15) vs. PK3: 0.12 (0.10–0.15) &mgr;g/mL, P = 0.09]. Albumin and LPV AUC0–12h fraction unbound were correlated (rs = 0.3, P = 0.03). Conclusions:Total LPV exposure was significantly decreased throughout pregnancy despite the increased dose. However, the exposure of unbound LPV did not change significantly regardless of trimester or dose. Predose concentrations of unbound LPV were not affected by the additional dose and were 70-fold greater than the minimum efficacy concentration. These findings suggest dose adjustments may not be necessary in all HIV-infected pregnant women.