Kristine B. Patterson

Penetration of Tenofovir and Emtricitabine in Mucosal Tissues: Implications for Prevention of HIV-1 Transmission

Antiretroviral drugs are found at different concentrations in human cervical, vaginal, and rectal mucosal tissues with implications for designing PrEP trials to prevent HIV transmission. HAARTening News for HIV Prevention Antiretroviral drug therapy (ART) has been used successfully for treating HIV-1. However, HIV transmission, principally through sexual intercourse, is still a major problem, with 7000 new infections reported daily worldwide. ART is now being investigated as a way not only to treat individuals with HIV but also to prevent the transmission of HIV infection. This strategy, called PrEP, or PrEP, requires that the concentrations of the antiretroviral drugs under investigation are at high enough concentrations in the target mucosal tissues, predominantly genital and colorectal, to prevent HIV infection. Such knowledge will be essential for designing new HIV prevention trials and also for interpreting the data from several prevention trials that have yielded conflicting results. In a new study, Patterson et al. set out to obtain this information for two antiretroviral drugs that have shown promise for HIV prevention: tenofovir (TFV) disoproxil fumarate (TDF) and emtricitabine (FTC). The researchers gave 12 healthy men and women a single oral dose of the fixed-dose combination pill TDF/FTC (Truvada) and then took samples of blood plasma, genital secretions, and vaginal, cervical, and rectal tissue biopsies over the next 14 days. The pro-drug forms TFV and FTC were measured in blood plasma and genital secretions, whereas the active intracellular phosphorylated metabolites of these drugs (TFV-DP and FTC-TP) were measured in vaginal, cervical, and rectal tissues. After a single oral dose, TFV and FTC were detected in blood plasma for the 14-day duration of the study. Encouragingly, the concentration of FTC was 27-fold greater in genital secretions than in blood plasma. However, the concentration of TFV was only 2.5-fold greater in genital secretions than in blood plasma. Both TFV and its active phosphorylated form TFV-DP were detected in rectal tissue for 14 days after dosing, and the cumulative exposure of rectal tissue to TFV-DP was 100-fold greater than that in vaginal and cervical tissues. In contrast, the cumulative exposure of vaginal and cervical tissues to FTC was only 10- to 15-fold greater than that for rectal tissue. Despite high concentrations of the pro-drug FTC in vaginal and cervical tissues, its active form FTC-TP was detected for ≤2 days in these tissues. This study demonstrates that the penetration of different human mucosal tissues and their exposure to the pro-drugs TFV and FTC and their active metabolites TFV-DP and FTC-TP is wide ranging and dependent on the tissue type. These findings reinforce the fact that the success of PrEP will depend on selecting the correct ART that achieves a critical concentration and duration of exposure in vulnerable mucosal tissues. Continuing pharmacological investigations will be crucial for ensuring the success of PrEP and ultimately for preventing HIV transmission. A mainstay of strategies to prevent HIV-1 transmission is to use antiretroviral therapy (ART) for pre-exposure prophylaxis (PrEP). Critical to the design and interpretation of PrEP prevention trials is the ability to make accurate pharmacological measurements of ART drugs in human genital and colorectal mucosal tissues, the principal route of HIV transmission. Here, we evaluated two drugs that are preferentially used for PrEP: tenofovir (TFV) disoproxil fumarate (TDF) and emtricitabine (FTC). A single oral dose of TDF/FTC (Truvada) was administered to 15 healthy individuals. Over the next 14 days, TFV and FTC were measured in blood plasma and genital secretions using a sensitive assay (lower level of quantification, 0.1 ng/ml). The active intracellular phosphorylated metabolites of these drugs [TFV diphospate (TFV-DP) and FTC triphosphate (FTC-TP)] were measured in homogenates prepared from rectal, vaginal, and cervical tissues. TFV and FTC were detected in blood plasma 14 days after administration of a single dose. The area under the concentration-time curve from 24 hours to 14 days (AUC1–14d) for FTC in genital secretions was 27-fold greater than in blood plasma, whereas the AUC1–14d for TFV was only 2.5-fold greater in genital secretions than in blood plasma. In rectal tissue, TFV and TFV-DP concentrations were detectable for 14 days and were 100-fold higher than the concentrations in vaginal and cervical tissues. Vaginal and cervical tissue concentrations of FTC were 10- to 15-fold higher than in rectal tissue. Despite high concentrations of FTC in vaginal and cervical tissue, FTC-TP concentrations in all tissue types were detected for only 2 days after dose. The exposure to TFV, TFV-DP, FTC, and FTC-TP was wide ranging depending on the type of mucosal tissue. These results demonstrate the need for detailed pharmacological studies to improve the application of ART for PrEP to prevent transmission of HIV.

Atazanavir Plus Ritonavir or Efavirenz as Part of a 3-Drug Regimen for Initial Treatment of HIV-1: A Randomized Trial

BACKGROUND Limited data compare once-daily options for initial therapy for HIV-1. OBJECTIVE To compare time to virologic failure; first grade-3 or -4 sign, symptom, or laboratory abnormality (safety); and change or discontinuation of regimen (tolerability) for atazanavir plus ritonavir with efavirenz-containing initial therapy for HIV-1. DESIGN A randomized equivalence trial accrued from September 2005 to November 2007, with median follow-up of 138 weeks. Regimens were assigned by using a central computer, stratified by screening HIV-1 RNA level less than 100 000 copies/mL or 100 000 copies/mL or greater; blinding was known only to the site pharmacist. (ClinicalTrials.gov registration number: NCT00118898) SETTING 59 AIDS Clinical Trials Group sites in the United States and Puerto Rico. PATIENTS Antiretroviral-naive patients. INTERVENTION Open-label atazanavir plus ritonavir or efavirenz, each given with with placebo-controlled abacavir-lamivudine or tenofovir disoproxil fumarate (DF)-emtricitabine. MEASUREMENTS Primary outcomes were time to virologic failure, safety, and tolerability events. Secondary end points included proportion of patients with HIV-1 RNA level less than 50 copies/mL, emergence of drug resistance, changes in CD4 cell counts, calculated creatinine clearance, and lipid levels. RESULTS 463 eligible patients were randomly assigned to receive atazanavir plus ritonavir and 465 were assigned to receive efavirenz, both with abacavir-lamivudine; 322 (70%) and 324 (70%), respectively, completed follow-up. The respective numbers of participants in each group who received tenofovir DF-emtricitabine were 465 and 464; 342 (74%) and 343 (74%) completed follow-up. Primary efficacy was similar in the group that received atazanavir plus ritonavir and and the group that received efavirenz and did not differ according to whether abacavir-lamivudine or tenofovir DF-emtricitabine was also given. Hazard ratios for time to virologic failure were 1.13 (95% CI, 0.82 to 1.56) and 1.01 (CI, 0.70 to 1.46), respectively, although CIs did not meet prespecified criteria for equivalence. The time to safety (P = 0.048) and tolerability (P < 0.001) events was longer in persons given atazanavir plus ritonavir than in those given efavirenz with abacavir-lamivudine but not with tenofovir DF-emtricitabine. LIMITATIONS Neither HLA-B*5701 nor resistance testing was the standard of care when A5202 enrolled patients. The third drugs, atazanavir plus ritonavir and efavirenz, were open-label; the nucleoside reverse transcriptase inhibitors were prematurely unblinded in the high viral load stratum; and 32% of patients modified or discontinued treatment with their third drug. CONCLUSION Atazanavir plus ritonavir and efavirenz have similar antiviral activity when used with abacavir-lamivudine or tenofovir DF-emtricitabine. PRIMARY FUNDING SOURCE National Institutes of Health.

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.

Atazanavir Plus Ritonavir or Efavirenz as Part of a 3-Drug Regimen for Initial Treatment of HIV-1

Few studies have compared once-daily treatment regimens for HIV-1. This randomized trial in antiretroviral-naive patients with HIV-1 showed that a once-daily ritonavir-boosted protease inhibitor re...

Lopinavir/ritonavir induces the hepatic activity of cytochrome P450 enzymes CYP2C9, CYP2C19, and CYP1A2 but inhibits the hepatic and intestinal activity of CYP3A as measured by a phenotyping drug cocktail in healthy volunteers

Objective: The effect of lopinavir/ritonavir (LPV/r) administration on cytochrome P450 (CYP) enzyme activity was quantified using a phenotyping biomarker cocktail. Changes in CYP2C9, CYP2C19, CYP3A, CYP1A2, N-acetyltransferase-2 (NAT-2), and xanthine oxidase (XO) activities were evaluated using warfarin (WARF) + vitamin K, omeprazole (OMP), intravenous (IV) and oral (PO) midazolam (MDZ), and caffeine (CAF). Design: Open-label, multiple-dose, pharmacokinetic study in healthy volunteers. Methods: Subjects (n = 14) simultaneously received PO WARF 10 mg, vitamin K 10 mg, OMP 40 mg, CAF 2 mg/kg, and IV MDZ 0.025 mg/kg on days (D) 1 and 14, and PO MDZ 5 mg on D2 and D15. LPV/r (400/100 mg twice daily) was administered on D4-17. CYP2C9 and CYP2C19 activities were quantified by S-WARF AUC0-inf and OMP/5-hydroxy OMP ratio, respectively. CYP1A2, NAT-2, and XO activities were quantified by urinary CAF metabolite ratios. Hepatic and intestinal + hepatic CYP3A activities were quantified by IV (CL) and PO (CL/F) MDZ clearance, respectively. Results: After LPV/r therapy, CYP2C9, CYP2C19, and CYP1A2 activity increased by 29%, 100%, and 43% (P = 0.001, 0.046, and 0.001), respectively. No changes were seen in NAT-2 or XO activity. Hepatic and intestinal + hepatic CYP3A activity decreased by 77% (P < 0.001) and 92% (P = 0.001), respectively. Conclusion: LPV/r therapy results in modest induction of CYP1A2 and CYP2C9 and potent induction of CYP2C19 activity. Increasing doses of concomitant medications metabolized by these enzymes may be necessary. LPV/r inhibited intestinal CYP3A to a greater extent than hepatic CYP3A activity. Doses of concomitant CYP3A substrates should be reduced when combined with LPV/r, although intravenously administered compounds may require less of a relative dose reduction than orally administered compounds.

Efficacy and Tolerability of 3 Nonnucleoside Reverse Transcriptase Inhibitor–Sparing Antiretroviral Regimens for Treatment-Naive Volunteers Infected With HIV-1: A Randomized, Controlled Equivalence Trial

Background Non-nucleoside reverse transcriptase (NNRTI) inhibitor-based antiretroviral therapy is not suitable for all treatment-naive HIV-infected persons.BACKGROUND Nonnucleoside reverse transcriptase inhibitor-based antiretroviral therapy is not suitable for all treatment-naive HIV-infected persons. OBJECTIVE To evaluate 3 nonnucleoside reverse transcriptase inhibitor-sparing initial antiretroviral regimens to show equivalence for virologic efficacy and tolerability. DESIGN A phase 3, open-label study randomized in a 1:1:1 ratio with follow-up for at least 96 weeks. (ClinicalTrials.gov: NCT00811954). SETTING 57 sites in the United States and Puerto Rico. PATIENTS Treatment-naive persons aged 18 years or older with HIV-1 RNA levels greater than 1000 copies/mL without resistance to nucleoside reverse transcriptase inhibitors or protease inhibitors. INTERVENTION Atazanavir, 300 mg/d, with ritonavir, 100 mg/d; raltegravir, 400 mg twice daily; or darunavir, 800 mg/d, with ritonavir, 100 mg/d, plus combination emtricitabine, 200 mg/d, and tenofovir disoproxil fumarate, 300 mg/d. MEASUREMENTS Virologic failure, defined as a confirmed HIV-1 RNA level greater than 1000 copies/mL at or after 16 weeks and before 24 weeks or greater than 200 copies/mL at or after 24 weeks, and tolerability failure, defined as discontinuation of atazanavir, raltegravir, or darunavir for toxicity. A secondary end point was a combination of virologic efficacy and tolerability. RESULTS Among 1809 participants, all pairwise comparisons of incidence of virologic failure over 96 weeks showed equivalence within a margin of equivalence defined as -10% to 10%. Raltegravir and ritonavir-boosted darunavir were equivalent for tolerability, whereas ritonavir-boosted atazanavir resulted in a 12.7% and 9.2% higher incidence of tolerability discontinuation than raltegravir and ritonavir-boosted darunavir, respectively, primarily because of hyperbilirubinemia. For combined virologic efficacy and tolerability, ritonavir-boosted darunavir was superior to ritonavir-boosted atazanavir, and raltegravir was superior to both protease inhibitors. Antiretroviral resistance at the time of virologic failure was rare but more frequent with raltegravir. LIMITATION The trial was open-label, and ritonavir was not provided. CONCLUSION Over 2 years, all 3 regimens attained high and equivalent rates of virologic control. Tolerability of regimens containing raltegravir or ritonavir-boosted darunavir was superior to that of the ritonavir-boosted atazanavir regimen. PRIMARY FUNDING SOURCE National Institute of Allergy and Infectious Diseases.

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.

Antiviral activity and safety of 873140, a novel CCR5 antagonist, during short-term monotherapy in HIV-infected adults.

Objective:873140 is a spirodiketopiperazine CCR5 antagonist with prolonged receptor binding and potent antiviral activity in vitro. This study evaluated plasma HIV RNA, safety, and pharmacokinetics following short-term monotherapy in HIV-infected adults. Design:Double-blind, randomized, placebo-controlled multi-center trial. Methods:Treatment-naive or experienced HIV-infected subjects with R5-tropic virus, CD4 cell count nadir > 200 × 106 cells/l, viral load > 5000 copies/ml and not receiving antiretroviral therapy for the preceding 12 weeks were enrolled. Forty subjects were randomized to one of four cohorts (200 mg QD, 200 mg BID, 400 mg QD, 600 mg BID) with 10 subjects (eight active, two placebo) in each cohort, and received treatment for 10 days. Serial HIV RNA, pharmacokinetics, and safety evaluations were performed through day 24. Results:Of the 40 subjects, 21 were treatment-experienced; 35 were male, 20 were non-white, and eight were coinfected with hepatitis C virus. Median baseline HIV RNA ranged from 4.26log10 to 4.46 log10. 873140 was generally well tolerated with no drug-related discontinuations. The most common adverse events were grade 1 gastrointestinal complaints that generally resolved within 1–3 days on therapy. No clinically significant abnormalities were observed on electrocardiogram or in laboratory parameters. Mean log changes in HIV RNA at nadir, and the percentage of subjects with > 1 log10 decrease were −0.12 (0%) for placebo, −0.46 (17%) for 200 mg once daily, −1.23 (75%) for 200 mg twice daily, −1.03 (63%) for 400 mg once daily, and −1.66 (100%) for 600 mg twice daily. An Emax relationship was observed between the area under the 873140 plasma concentration–time curve and change in HIV RNA. Conclusions:873140 demonstrated potent antiretroviral activity and was well tolerated. These results support further evaluation in Phase 2b/3 studies.

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.