Dissimilarities in the metabolism of antiretroviral drugs used in HIV pre-exposure prophylaxis in colon and vagina tissues

Consensus recommendations for use of long-acting antiretroviral medications in the treatment and prevention of HIV-1: Endorsed by the American Academy of HIV Medicine, American College of Clinical Pharmacy, Canadian HIV and Viral Hepatitis Pharmacists Network, European AIDS Clinical Society, and Society of Infectious Diseases Pharmacists

Five long-acting (LA) antiretrovirals (ARVs) are currently available in a limited number of countries worldwide for HIV-1 prevention or treatment-cabotegravir, rilpivirine, lenacapavir, ibalizumab, and dapivirine. Implementing use of LA ARVs into routine clinical practice requires significant changes to the current framework of HIV-1 prevention, treatment, and service provision. Given the novelty, complexity, and interdisciplinary requirements needed to safely and optimally utilize LA ARVs, consensus recommendations on the use of LA ARVs will assist clinicians in optimizing use of these agents. The purpose of these recommendations is to provide guidance for the clinical use of LA ARVs for HIV-1 treatment and prevention. In addition, future areas of research are also identified and discussed.

Investigating the Contribution of Drug-Metabolizing Enzymes in Drug-Drug Interactions of Dapivirine and Miconazole

Dapivirine (DPV) is a potent NNRTI used to prevent the sexual transmission of HIV. In a phase 1 trial (IPM 028), the concomitant use of a DPV vaginal ring and an antifungal miconazole (MIC) vaginal capsule was found to increase the systemic exposure to DPV in women, suggesting a potential for drug-drug interactions. This study's objective was to investigate the mechanism of DPV-MIC interactions using drug-metabolizing enzymes (DMEs; CYPs and UGTs) that are locally expressed in the female reproductive tract (FRT). In vitro studies were performed to evaluate the metabolism of DPV and its inhibition and induction potential with DMEs. In addition, the impact of MIC on DPV metabolism and the inhibitory potential of DPV with DMEs were studied. Our findings suggest that DPV is a substrate of CYP1A1 and CYP3A4 enzymes and that MIC significantly decreased the DPV metabolism by inhibiting these two enzymes. DPV demonstrated potent inhibition of CYP1A1 and moderate/weak inhibition of the six CYP and eight UGT enzymes evaluated. MIC showed potent/moderate inhibition of seven CYP enzymes and weak/no inhibition of eight UGT enzymes. The combination of DPV and MIC showed potent inhibition of seven CYP enzymes (1A1, 1A2, 1B1, 2B6, 2C8, 2C19, and 3A4) and four UGT enzymes (1A3, 1A6, 1A9, and 2B7). DPV was not an inducer of CYP1A2, CYP2B6, and CYP3A4 enzymes in primary human hepatocytes. Therefore, the increased systemic concentrations of DPV observed in IPM 028 were likely due to the reduced metabolism of DPV because of CYP1A1 and CYP3A4 enzymes inhibition by MIC in the FRT.

Environmental Pollutants, Mucosal Barriers, and Pathogen Susceptibility; The Case for Aflatoxin B1 as a Risk Factor for HIV Transmission and Pathogenesis

HIV transmission risk is dependent on the infectivity of the HIV+ partner and personal susceptibility risk factors of the HIV- partner. The mucosal barrier, as the internal gatekeeper between environment and self, concentrates and modulates the internalization of ingested pathogens and pollutants. In this review, we summarize the localized effects of HIV and dietary toxin aflatoxin B1 (AFB1), a common pollutant in high HIV burden regions, e.g., at the mucosal barrier, and evidence for pollutant-viral interactions. We compiled literature on HIV and AFB1 geographic occurrences, mechanisms of action, related co-exposures, personal risk factors, and HIV key determinants of health. AFB1 exposure and HIV sexual transmission hotspots geographically co-localize in many low-income countries. AFB1 distributes to sexual mucosal tissues generating inflammation, microbiome changes and a reduction of mucosal barrier integrity, effects that are risk factors for increasing HIV susceptibility. AFB1 exposure has a positive correlation to HIV viral load, a risk factor for increasing the infectivity of the HIV+ partner. The AFB1 exposure and metabolism generates inflammation that recruits HIV susceptible cells and generates chemokine/cytokine activation in tissues exposed to HIV. Although circumstantial, the available evidence makes a compelling case for studies of AFB1 exposure as a risk factor for HIV transmission, and a modifiable new component for combination HIV prevention efforts.

Metabolism of Long-Acting Rilpivirine After Intramuscular Injection: HIV Prevention Trials Network Study 076 (HPTN 076)

A long-acting injectable formulation of rilpivirine (RPV), a non-nucleoside reverse transcriptase inhibitor, is currently under investigation for use in human immunodeficiency virus (HIV) maintenance therapy. We previously characterized RPV metabolism after oral dosing and identified seven metabolites: four metabolites resulting from mono- or dioxygenation of the 2,6-dimethylphenyl ring itself or either of the two methyl groups located on that ring, one N-linked RPV glucuronide conjugate, and two O-linked RPV glucuronides produced via glucuronidation of mono- and dihydroxymethyl metabolites. However, as is true for most drugs, the metabolism of RPV after injection has yet to be reported. The phase II clinical trial HPTN 076 enrolled 136 HIV-uninfected women and investigated the safety and acceptability of long-acting injectable RPV for use in HIV pre-exposure prophylaxis. Through the analysis of plasma samples from 80 of these participants in the active product arm of the study, we were able to detect 2 metabolites after intramuscular injection of long-acting RPV, 2-hydroxymethyl-RPV, and RPV N-glucuronide. Of the total of 80 individuals, 72 participants exhibited detectable levels of 2-hydroxymethyl-RPV in plasma samples whereas RPV N-glucuronide was detectable in plasma samples of 78 participants. In addition, RPV N-glucuronide was detectable in rectal fluid, cervicovaginal fluid, and vaginal tissue. To investigate potential genetic variation in genes encoding enzymes relevant to RPV metabolism, we isolated genomic DNA and performed next-generation sequencing of CYP3A4, CYP3A5, UGT1A1 and UGT1A4. From these analyses, four missense variants were detected for CYP3A4 whereas one missense variant and one frameshift variant were detected for CYP3A5. A total of eight missense variants of UGT1A4 were detected, whereas two variants were detected for UGT1A1; however, these variants did not appear to account for the observed interindividual variability in metabolite levels. These findings provide insight into the metabolism of long-acting RPV and contribute to an overall understanding of metabolism after oral dosing versus injection. ClinicalTrials.gov Identifier: NCT02165202.

Endogenous Hormones and Antiretroviral Exposure in Plasma, Cervicovaginal Fluid, and Upper-Layer Packed Cells of Malawian Women Living with HIV

Overlap in metabolism pathways of endogenous female sex hormones and antiretroviral drugs may lead to altered exposure to these compounds. In a family planning clinic in Lilongwe, Malawi, blood, blood cell, and cervicovaginal fluid (CVF) samples from seventy-three HIV positive Malawian women taken in follicular and luteal menstrual phases were assessed for estradiol and progesterone by chemiluminescent immunoassay, and for antiretroviral concentration by liquid chromatography-mass spectrometry. In both follicular and luteal phases, estradiol concentrations were lower in women receiving efavirenz compared with women on non-efavirenz regimens or no antiretroviral therapy (p < .01). Serum estradiol was moderately and negatively correlated with efavirenz plasma (r = -0.36, p < .001) and CVF (r = -0.50, p < .001) concentrations. Serum estradiol was a significant predictor of efavirenz CVF concentrations even after adjusting for efavirenz plasma concentrations (p = .02). In upper-layer packed cells (ULPCs), tenofovir diphosphate (TFVdp) concentrations were similar between follicular and luteal phases and were not correlated with estradiol or progesterone concentrations. Tenofovir concentrations in CVF were not associated with menstrual cycle or serum hormone concentrations. In CVF and plasma, efavirenz concentrations were negatively correlated with serum estradiol concentrations, suggesting a modulatory effect of estradiol on efavirenz metabolism and/or transport processes, and/or an effect of efavirenz on the metabolism of estradiol. Differences in CVF persisted even after adjusting for plasma concentrations, suggesting a mechanism specific to the female genital compartment separate from absorption or hepatic metabolism. In contrast, TFVdp concentrations in ULPC were not influenced by endogenous estradiol or progesterone concentrations.

Pharmacokinetics of HIV therapies in pregnant patients: an update

INTRODUCTION

Mother-to-child transmission (MTCT) of HIV is thought to account for over 90% of new pediatric infections, and is associated with poor maternal and fetal outcomes. As such ensuring further reduction in MTCT is a priority in HIV treatment and prevention programs.

AREAS COVERED

This review aims to provide a comprehensive update on the pharmacokinetics of recently approved antiretroviral drugs and novel drug formulations and delivery systems. Alongside recent recommendations for dose adjustments, and an overview of the implications of co-infections on the pharmacokinetics of antiretrovirals relevant to pregnant HIV positive patients. Additionally, potential opportunities to progress pharmacokinetic research of new treatments in this population are highlighted.

EXPERT OPINION

In order to improve our understanding of how to provide safe and effective treatment to HIV positive pregnant women, further work is required to enable their inclusion in early stages of clinical trials. Incentives must be created for this research, in the form of additional investment by key stakeholders and regulatory agencies. Furthermore, as the incidence of MTCT is reduced globally there is a need to conduct long-term pharmacovigilance studies in uninfected children exposed to HIV and antiretrovirals in utero, in order to determine the safest and most effective antiretroviral therapies.

Rational Design of a Multipurpose Bioadhesive Vaginal Film for Co-Delivery of Dapivirine and Levonorgestrel

Human immunodeficiency virus (HIV) infection and unintended pregnancy, which can lead to life-threatening complications, are two major burdens for female reproductive health. To address these pressing health issues, multipurpose prevention technologies (MPTs) are proposed to deliver two or more drugs simultaneously. MPTs could offer several benefits for users such as improved convenience, increased effectiveness, reduced cost, and decreased environmental burden. Here, we report the development, and in vitro and in vivo assessment of a bioadhesive vaginal film as a coitally-independent MPT dosage form for delivering dapivirine (DPV) and levonorgestrel (LNG) to prevent HIV infection and unintended pregnancy, respectively. After confirming the feasibility of bioadhesive film use for weekly drug delivery in vivo through colpophotography and MRI evaluation, the pharmacokinetics (PK) of DPV/LNG single entity and combination bioadhesive films was investigated in pigtailed macaques (n = 5). Both drugs from single entity or combination films were able to provide sustained drug release in vivo. The combination film showed lower local tissue clearance for DPV and exhibited significantly increased plasma concentration for LNG as compared to the single entity film. This proof-of-concept study demonstrates the ability of this novel bioadhesive film platform to deliver LNG and DPV simultaneously as an MPT product for the prevention of HIV infection and unintended pregnancy.

Rilpivirine Plasma and Cervicovaginal Concentrations in Women During Pregnancy and Postpartum

BACKGROUND

Concentrations of antiretrovirals in the genital tract play a key role in preexposure prophylaxis. This study aims to describe rilpivirine (Edurant) concentrations in the genital tract in pregnant and postpartum women.

METHODS

International Maternal Pediatric Adolescent AIDS Clinical Trials Protocol P1026s is an ongoing, prospective study of antiretroviral pharmacokinetics in HIV-infected pregnant women that include a cohort receiving rilpivirine combination regimen. Intensive pharmacokinetics evaluations were performed at steady state during the second and third trimester, and postpartum. Plasma and directly aspirated cervicovaginal fluid (CVF) samples were collected at 4 time points around an observed dose and measured using high-performance liquid chromatography with ultraviolet detection, [plasma; lower limit of quantification (LLQ) = 10 ng/mL] or liquid chromatography-tandem mass spectrometry (CVF; LLQ = 1 ng/mL).

RESULTS

A total of 24 women were included in the analysis. For all time points combined, median (interquartile range) rilpivirine concentrations were 70 ng/mL (23-121) in CVF and 92 ng/mL (49-147) in plasma. The CVF to plasma AUC(0-4) ratios were significantly higher in the second (0.90, 90% CI: 0.61 to 1.46) and third trimesters of pregnancy compared with postpartum (0.40, 90% CI: 0.19 to 0.87). Three of 189 (1.6%) plasma samples in 2 women were below the LLQ and the corresponding CVF concentrations. Seventeen additional CVF concentrations (10.6%) were below LLQ in 13 participants. No major safety concerns were noted.

CONCLUSIONS

Rilpivirine concentrations were higher in the CVF during pregnancy compared with postpartum. CVF Rilpivirine is likely to achieve inhibitory concentrations effective for preventing peripartum HIV transmission.

Pharmacology of Antiretrovirals in the Female Genital Tract for HIV Prevention

Preexposure prophylaxis (PrEP) is a powerful tool that, as part of a comprehensive prevention package, has potential to significantly impact the HIV epidemic. PrEP effectiveness is believed to be dependent on the exposure and efficacy of antiretrovirals at the site of HIV transmission. Clinical trial results as well as modeling and simulation indicate the threshold of adherence required for PrEP efficacy of emtricitabine/tenofovir disoproxil fumarate may differ between sites of HIV transmission with less forgiveness for missed doses in women exposed through genital tissue compared to people exposed through colorectal tissue. This suggests a role for local and host factors to influence mucosal pharmacology. Here we review the mucosal pharmacology of antiretrovirals in the female genital tract and explore potential determinants of PrEP efficacy. Host factors such as inflammation, coinfections, hormonal status, and the vaginal microbiome will be explored as well as the role of drug-metabolizing enzymes and transporters in regulating local drug exposure. The use of preclinical and early clinical models to predict clinical effectiveness is also discussed.

Physiologically-based pharmacokinetic model of vaginally administered dapivirine ring and film formulations

AIMS

A physiologically-based pharmacokinetic (PBPK) model of the vaginal space was developed with the aim of predicting concentrations in the vaginal and cervical space. These predictions can be used to optimize the probability of success of vaginally administered dapivirine (DPV) for HIV prevention. We focus on vaginal delivery using either a ring or film.

METHODS

A PBPK model describing the physiological structure of the vaginal tissue and fluid was defined mathematically and implemented in MATLAB. Literature reviews provided estimates for relevant physiological and physiochemical parameters. Drug concentration-time profiles were simulated in luminal fluids, vaginal tissue and plasma after administration of ring or film. Patient data were extracted from published clinical trials and used to test model predictions.

RESULTS

The DPV ring simulations tested the two dosing regimens and predicted PK profiles and area under the curve of luminal fluids (29 079 and 33 067 mg h l-1 in groups A and B, respectively) and plasma (0.177 and 0.211 mg h l-1 ) closely matched those reported (within one standard deviation). While the DPV film study reported drug concentration at only one time point per patient, our simulated profiles pass through reported concentration range.

CONCLUSIONS

HIV is a major public health issue and vaginal microbicides have the potential to provide a crucial, female-controlled option for protection. The PBPK model successfully simulated realistic representations of drug PK. It provides a reliable, inexpensive and accessible platform where potential effectiveness of new compounds and the robustness of treatment modalities for pre-exposure prophylaxis can be evaluated.

Brief Report: Dapivirine Vaginal Ring Use Does Not Diminish the Effectiveness of Hormonal Contraception

OBJECTIVE

To evaluate the potential for a clinically relevant drug-drug interaction with concomitant use of a dapivirine vaginal ring, a novel antiretroviral-based HIV-1 prevention strategy, and hormonal contraception by examining contraceptive efficacies with and without dapivirine ring use.

DESIGN

A secondary analysis of women participating in MTN-020/ASPIRE, a randomized, double-blind, placebo-controlled trial of the dapivirine vaginal ring for HIV-1 prevention.

METHODS

Use of a highly effective method of contraception was an eligibility criterion for study participation. Urine pregnancy tests were performed monthly. Pregnancy incidence by arm was calculated separately for each hormonal contraceptive method and compared using an Andersen-Gill proportional hazards model stratified by site and censored at HIV-1 infection.

RESULTS

Of 2629 women enrolled, 2310 women returned for follow-up and reported using a hormonal contraceptive method at any point during study participation (1139 in the dapivirine arm and 1171 in the placebo arm). Pregnancy incidence in the dapivirine arm versus placebo among women using injectable depot medroxyprogesterone acetate was 0.43% vs. 0.54%, among women using injectable norethisterone enanthate was 1.15% vs. 0%, among women using hormonal implants was 0.22% vs. 0.69%, and among women using oral contraceptive pills was 32.26% vs. 28.01%. Pregnancy incidence did not differ by study arm for any of the hormonal contraceptive methods.

CONCLUSIONS

Use of the dapivirine ring does not reduce the effectiveness of hormonal contraceptives for pregnancy prevention. Oral contraceptive pill use was associated with high pregnancy incidence, potentially because of poor pill adherence. Injectable and implantable methods were highly effective in preventing pregnancy.

Targeted microbicides for preventing sexual HIV transmission

Sexual transmission remains one of the most significant hurdles in the fight against HIV infection. The use of vaginal or rectal microbicides has been proposed for topical pre-exposure prophylaxis but available results from clinical trials of candidate products have been, at best, less than optimal. While waiting for the first product to get regulatory approval, novel approaches are being explored in order to enhance efficacy, as well as to assure safety. Strategies involving specific delivery of antiviral agents to key players involved in the early steps of sexual transmission have the potential to help achieving such purposes. Engineering systems that allow targeting cells, tissues or other biological structures of interest may provide a way to modulate local pharmacokinetics of promising microbicide molecules and, thus, maximize protection. This concise review discusses the identification and use of potential targets for such purpose, while detailing on several examples of targeted systems engineered as potential microbicide candidates. Furthermore, remaining challenges and hints for future work in the field of targeted microbicides are addressed.

Will dapivirine redeem the promises of anti-HIV microbicides? Overview of product design and clinical testing

Microbicides are being developed in order to prevent sexual transmission of HIV. Dapivirine, a non-nucleoside reverse transcriptase inhibitor, is one of the leading drug candidates in the field, currently being tested in various dosage forms, namely vaginal rings, gels, and films. In particular, a ring allowing sustained drug release for 1month is in an advanced stage of clinical testing. Two parallel phase III clinical trials are underway in sub-Saharan Africa and results are expected to be released in early 2016. This article overviews the development of dapivirine and its multiple products as potential microbicides, with particular emphasis being placed on clinical evaluation. Also, critical aspects regarding regulatory approval, manufacturing, distribution, and access are discussed.

Comparative Expression Analysis of Cytochrome P450 1A1, Cytochrome P450 1B1 and Nuclear Receptors in the Female Genital and Colorectal Tissues of Human and Pigtailed Macaque

This manuscript summarizes our recent progress in examine the CYP1A1 and CYP1B1 as well as a number of nuclear receptors in the female genital and colorectal tissues of human and pigtailed macaque. Understanding the nuclear receptor mediated regulation of CYP1A1 and 1B1 expression in these tissues is necessary for identifying cancer risk factors and developing CYP1A1/1B1-targeted anti-cancer therapeutics. However, there is a lack of systematic and comparative analysis of the expression profile of CYP1A1, 1B1 and NRs in the female genital and colorectal tissues of human and clinically relevant animal models. The current study aims to fill this gap. We found CYP1A1, CYP1B1 and a number of nuclear receptors were expressed in the female genital and colorectal tissues of human and macaque. However, the mRNA level and protein localization of these CYP enzymes and NRs depended on the type of tissue examined.

Cytochrome P450 (CYP) 1A1 and CYP1B1 activate hormonal and environmental procarcinogens, and are associated with carcinogenesis in female genital and colorectal tissues. Understanding the nuclear receptor (NR) mediated regulation of CYP expression in these tissues is necessary for identifying cancer risk factors and developing CYP1A1/1B1-targeted anti-cancer therapeutics. The study aims to analyze the expression profile of CYP1A1, 1B1 and NRs in the female genital and colorectal tissues of human and pigtailed macaques. We found that compared to the liver, human CYP1A1 mRNA level in the genital and colorectal tissues was significantly lower, while the CYP1B1 level was significantly higher. CYP1A1 protein was mainly localized in the plasma membrane of the uterine and endocervical epithelial cells. The CYP1B1 protein was concentrated in the nucleus of genital and colorectal tissues. Fourteen NRs in the genital tract and 12 NRs in colorectal tissue were expressed at levels similar to or higher than the liver. The expression and localization of CYP1A1, CYP1B1, and NRs in macaque tissues were usually comparable to those of human tissues. In addition, menopause did not significantly alter the ectocervical mRNA levels of CYP1A1, CYP1B1, or NRs.

Distinct Pharmacodynamic Activity of Rilpivirine in Ectocervical and Colonic Explant Tissue

A long-acting injectable form of rilpivirine (RPV) is being evaluated in clinical trials for the prevention of HIV infection. Preclinical testing was undertaken to define RPV pharmacokinetic (PK) and pharmacodynamic (PD) activities in ectocervical and colonic tissue treated in vitro Tenfold dilutions of RPV were added to the basolateral medium of polarized ectocervical and colonic explant tissues. To half the explants, HIV-1BaL was applied to the apical tissue surface. After culture overnight, all the explants were washed and the RPV in the explants not exposed to HIV was quantified using a validated liquid chromatography-mass spectrometry assay. For efficacy, explants exposed to HIV remained in culture, and supernatants were collected to assess viral replication using a p24 enzyme-linked immunosorbent assay. The data were log10 transformed, and PK/PD correlations were determined using GraphPad Prism and SigmaPlot software. The application of RPV to the basolateral medium at 10 μM and 1 μM was effective in protecting ectocervical and colonic tissues, respectively, from HIV infection. When the RPV in paired ectocervical and colonic explant tissues was quantified, significant inverse linear correlations (P < 0.001) between p24 and RPV concentrations were obtained; more viral replication was noted at lower drug levels. Using a maximum effect model, RPV concentrations of 271 nM in ectocervical tissue and 45 nM in colonic tissue were needed to achieve a 90% effective concentration (EC90). These data demonstrate that RPV can suppress HIV infection in mucosal tissue but that higher levels of RPV are needed in female genital tract tissue than in gastrointestinal tract tissue for protection.

Broadly Neutralizing Anti-HIV Antibodies Prevent HIV Infection of Mucosal Tissue Ex Vivo

Broadly neutralizing monoclonal antibodies (nAbs) specific for HIV are being investigated for use in HIV prevention. Due to their ability to inhibit HIV attachment to and entry into target cells, nAbs may be suitable for use as topical HIV microbicides. As such, they would present an alternative intervention for individuals who may not benefit from using antiretroviral-based products for HIV prevention. We theorize that nAbs can inhibit viral transmission through mucosal tissue, thus reducing the incidence of HIV infection. The efficacy of the PG9, PG16, VRC01, and 4E10 antibodies was evaluated in an ex vivo human model of mucosal HIV transmission. nAbs reduced HIV transmission, causing 1.5- to 2-log10 reductions in HIV replication in ectocervical tissues and ≈3-log10 reductions in HIV replication in colonic tissues over 21 days. These antibodies demonstrated greater potency in colonic tissues, with a 50-fold higher dose being required to reduce transmission in ectocervical tissues. Importantly, nAbs retained their potency and reduced viral transmission in the presence of whole semen. No changes in tissue viability or immune activation were observed in colonic or ectocervical tissue after nAb exposure. Our data suggest that topically applied nAbs are safe and effective against HIV infection of mucosal tissue and support further development of nAbs as a topical microbicide that could be used for anal as well as vaginal protection.

Natural polyphenols: potential in the prevention of sexually transmitted viral infections

Sexually transmitted viral infections represent a major public health concern due to lack of effective prevention strategies. Efforts are ongoing to develop modalities that can enable simultaneous prevention of multiple sexually transmitted infections. In the present review, we discuss the potential of natural polyphenols to prevent sexually transmitted viral infections. The review gives an account of various in vitro and in vivo studies carried out on epigallocatechin gallate, theaflavins (black tea polyphenols), resveratrol, genistein and curcumin to highlight their potential to prevent sexually transmitted infections caused by HIV (human immunodeficiency virus), HSV (herpes simplex virus) and HPV (human papilloma virus).

Drug transporter gene expression in human colorectal tissue and cell lines: modulation with antiretrovirals for microbicide optimization

OBJECTIVES

The objectives of this study were to comprehensively assess mRNA expression of 84 drug transporters in human colorectal biopsies and six representative cell lines, and to investigate the alteration of drug transporter gene expression after exposure to three candidate microbicidal antiretroviral (ARV) drugs (tenofovir, darunavir and dapivirine) in the colorectal epithelium. The outcome of the objectives informs development of optimal ARV-based microbicidal formulations for prevention of HIV-1 infection.

METHODS

Drug transporter mRNA expression was quantified from colorectal biopsies and cell lines by quantitative real-time PCR. Relative mRNA expression was quantified in Caco-2 cells and colorectal explants after induction with ARVs. Data were analysed using Pearson's product moment correlation (r), hierarchical clustering and principal component analysis (PCA).

RESULTS

Expression of 58 of the 84 transporters was documented in colorectal biopsies, with genes for CNT2, P-glycoprotein (P-gp) and MRP3 showing the highest expression. No difference was noted between individual subjects when analysed by age, gender or anatomical site (rectum or recto-sigmoid) (r = 0.95-0.99). High expression of P-gp and CNT2 proteins was confirmed by immunohistochemical staining. Similarity between colorectal tissue and cell-line drug transporter gene expression was variable (r = 0.64-0.84). PCA showed distinct clustering of human colorectal biopsy samples, with the Caco-2 cells defined as the best surrogate system. Induction of Caco-2 cell lines with ARV drugs suggests that darunavir-based microbicides incorporating tenofovir may result in drug-drug interactions likely to affect distribution of individual drugs to sub-epithelial target cells.

CONCLUSIONS

These findings will help optimize complex formulations of rectal microbicides to realize their full potential as an effective approach for pre-exposure prophylaxis against HIV-1 infection.

Pharmacodynamic Activity of Dapivirine and Maraviroc Single Entity and Combination Topical Gels for HIV-1 Prevention

PURPOSE

Dapivirine (DPV), a non-nucleoside reverse transcriptase inhibitor, and maraviroc (MVC), a CCR5 antagonist, were formulated into aqueous gels designed to prevent mucosal HIV transmission.

METHODS

0.05% DPV, 0.1% MVC, 0.05% DPV/0.1% MVC and placebo gels were evaluated for pH, viscosity, osmolality, and in vitro release. In vitro assays and mucosal tissues were used to evaluate anti-HIV activity. Viability (Lactobacilli only) and epithelial integrity in cell lines and mucosal tissues defined safety.

RESULTS

The gels were acidic and viscous. DPV gel had an osmolality of 893 mOsm/kg while the other gels had an osmolality of <100 mOsm/kg. MVC release was similar from the single and combination gels (~5 μg/cm(2)/min(1/2)), while DPV release was 10-fold less from the single as compared to the combination gel (0.4331 μg/cm(2)/min(1/2)). Titrations of the gels showed 10-fold more drug was needed to protect ectocervical than colonic tissue. The combination gel showed ~10- and 100-fold improved activity as compared to DPV and MVC gel, respectively. All gels were safe.

CONCLUSIONS

The DPV/MVC gel showed a benefit blocking HIV infection of mucosal tissue compared to the single entity gels. Combination products with drugs affecting unique steps in the viral replication cycle would be advantageous for HIV prevention.

Formulation and delivery of anti-HIV rectal microbicides: advances and challenges

Men and women engaged in unprotected receptive anal intercourse (RAI) are at higher risk of acquiring HIV from infected partners. The implementation of preventive strategies is urgent and rectal microbicides may be a useful tool in reducing the sexual transmission of HIV. However, pre-clinical and first clinical trials have been able to identify limitations of candidate products, mostly related with safety issues, which can in turn enhance viral infection. Indeed, the development of suitable formulations for the rectal delivery of promising antiretroviral drugs is not an easy task, and has been mostly based on products specifically intended for vaginal delivery, but these have been shown to provide sub-optimal outcomes when administered rectally. Research and development in the rectal microbicide field are now charting their own path and important information is now available. In particular, specific formulation requirements of rectal microbicide products that need to be met have just recently been acknowledged despite additional work being still required. Desirable rectal microbicide product features regarding characteristics such as pH, osmolality, excipients, dosage forms, volume to be administered and the need for applicator use have been studied and defined in recent years, and specific guidance is now possible. This review provides a synopsis of the field of rectal microbicides, namely past and ongoing clinical studies, and details on formulation and drug delivery issues regarding the specific development of rectal microbicide products. Also, future work, as required for the advancement of the field, is discussed.

HIV pre-exposure prophylaxis: mucosal tissue drug distribution of RT inhibitor Tenofovir and entry inhibitor Maraviroc in a humanized mouse model

Pre-exposure prophylaxis (PrEP) strategies utilizing anti-retroviral drugs show considerable promise for HIV prevention. However there is insufficient pharmacokinetic (PK) data on drug concentrations required for protection at the relevant mucosal tissues where the infection is initiated. Here we evaluated the utility of a humanized mouse model to derive PK data on two leading drugs, the RT inhibitor Tenofovir (TFV) and CCR5 inhibitor Maraviroc (MVC). Following oral dosing, both the drugs and the intracellular active TFV-diphosphate could be detected in vaginal, rectal and intestinal tissues. The drug exposures (AUC₂₄ h) were found to be higher in vaginal tissue compared to plasma with even higher levels detected in rectal and intestinal tissues. The overall trends of drug concentrations seen in humanized mice reflect those seen in the human thus establishing the utility of this model complementing the present non-human primate (NHP) models for future pre-clinical evaluations of promising HIV PrEP drug candidates.

Pharmacokinetics and preliminary safety study of pod-intravaginal rings delivering antiretroviral combinations for HIV prophylaxis in a macaque model

Preexposure prophylaxis using oral regimens involving the HIV nucleoside reverse transcriptase inhibitors tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC) demonstrated efficacy in three clinical trials. Adherence was determined to be a key parameter for success. Incorporation of the TDF-FTC combination into intravaginal rings (IVRs) for sustained mucosal delivery could increase product adherence and efficacy compared with those of oral and vaginal gel formulations. A novel pod-IVR technology capable of delivering multiple drugs is described; this constitutes the first report of an IVR delivering TDF and FTC, as well as a triple-combination IVR delivering TDF, FTC, and the entry inhibitor maraviroc (MVC). The pharmacokinetics and preliminary local safety of the two combination pod-IVRs were evaluated in the pig-tailed macaque model. The devices exhibited sustained release at controlled rates over the 28-day study period. Median steady-state drug levels in vaginal tissues in the TDF-FTC group were 30 μg g(-1) (tenofovir [TFV], in vivo hydrolysis product of TDF) and 500 μg g(-1) (FTC) and in the TDF-FTC-MVC group were 10 μg g(-1) (TFV), 150 μg g(-1) (FTC), and 20 μg g(-1) (MVC). No adverse events were observed, and there were no toxicological findings. Mild-to-moderate increases in inflammatory infiltrates were observed in the vaginal tissues of some animals in both the presence and the absence of the IVRs. The IVRs did not disturb the vaginal microbiota, and levels of proinflammatory cytokines remained stable throughout the study. Pod-IVR candidates based on the TDF-FTC combination have potential for the prevention of vaginal HIV acquisition and merit clinical investigation.