CAPRISA 004 tenofovir microbicide trial: no impact of tenofovir gel on the HIV transmission bottleneck

Chitosan-poly(ethylene oxide) nanofibrous mat as a vaginal platform for tenofovir disoproxyl fumarate - The effect of vaginal pH on drug carrier performance

In the present work, a solution blow spun nanofibrous mat comprised of chitosan (CS) and poly(ethylene oxide) (PEO) was obtained as vaginal platform for tenofovir disoproxil fumarate (TDF) to prevent sexually transmitted infections. Apart from physicochemical and mechanical analysis, the specific steps involved studies on nanofibrous mat mucoadhesive and swelling characteristics upon pH fluctuations over the physiological range. Physicochemical analysis showed uniform drug distribution within the CS/PEO mat volume and pointed toward physical interactions between the drug and polymers. TDF-loaded CS/PEO nanofibrous mat was shown potentially safe when evaluated by the MTT metabolic activity and JC-1 assays in human vaginal epithelial cells VK2-E6/E7. In vitro antiviral studies indicated inhibition efficacy of TDF-CS/PEO nanofibrous mat toward HSV-2 virus and proved the SBS process does not change the microbicidal activity of drug molecule. Fluctuations in the physiological vaginal pH range of 3.8 to 5.0 substantially affected mucoadhesive and swelling behavior of chitosan which in turn impacted drug dissolution rate from polymer carrier. The rate of permeation and accumulation of TDF in vaginal tissue differed in response to vaginal pH. Faster drug permeation assessed at pH 5.0 suggests that an increase in vaginal pH could improve TDF bioavailability at earlier time points.

Impact of Case Definitions on Efficacy Estimation in Clinical Trials-A Proof-of-Principle Based on Historical Examples

Efficacy estimations in clinical trials are based on case definitions. Commonly, they are a more or less complex set of conditions that have to be fulfilled in order to define a clinical case. In the simplest variant, such a case is identical with a single positive diagnostic test result. Frequently, however, case definitions are more complex. Further, their conditions often ignore the inherent logical structure of symptoms and disease: A symptom or a set of symptoms may be necessary but not sufficient for the unambiguous identification of a case. After describing the structure of case definitions and its impact on efficacy estimations, we exemplify this impact using data from two clinical trials dealing with the effectiveness of the vaginal application of tenofovir gel for the prevention of HIV infections and with the therapeutic effects of fecal transplantation on recurrent Clostridium difficile infections. We demonstrate that the diagnostic performance of case definitions affects efficacy estimations for interventions in clinical trials. The potential risk of bias and uncertainty is high, irrespective of the complexity of the case definition. Accordingly, case definitions in clinical trials should focus on specificity in order to avoid the risk of bias.

Rhodanine derivatives as potent anti-HIV and anti-HSV microbicides

Although highly active antiretroviral therapies (HAART) remarkably increased life expectancy of HIV positive people, the rate of novel HIV-1 infections worldwide still represent a major concern. In this context, pre-exposure prophylaxis (PrEP) approaches such as vaginal microbicide gels topically releasing antiretroviral drugs, showed to have a striking impact in limiting HIV-1 spread. Nevertheless, the co-presence of other genital infections, particularly those due to HSV-1 or 2, constitute a serious drawback that strongly limits the efficacy of PrEP approaches. For this reason, combinations of different compounds with mixed antiviral and antiretroviral activity are thoroughly investigated Here we report the synthesis and the biological evaluation of a novel series of rhodanine derivatives, which showed to inhibit both HIV-1 and HSV-1/2 replication at nanomolar concentration, and were found to be active also on acyclovir resistant HSV-2 strains. The compounds showed a considerable reduction of activity in presence of serum due to a high binding to serum albumin, as determined through in vitro ADME evaluations. However, the most promising compound of the series maintained a considerable activity in gel formulation, with an EC50 comparable to that obtained for the reference drug tenofovir. Moreover, the series of compounds showed pharmacokinetic properties suitable for topical formulation, thus suggesting that the novel rhodanine derivatives could represent effective agents to be used as dual anti HIV/HSV microbicides in PrEP approaches.

Brief Report: Selection of HIV-1 Variants With Higher Transmission Potential by 1% Tenofovir Gel Microbicide

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Background:

Women in the CAPRISA 004 trial assigned to use 1% tenofovir (TFV) microbicide gel, who became HIV-1 infected, had higher viral load set-point and slower antibody avidity maturation compared with placebo participants. We investigated whether TFV gel was selected for viruses with altered genetic characteristics.

Setting:

The participants of the CAPRISA 004 trial (n = 28 TFV and 43 placebo) were from KwaZulu-Natal Province, South Africa and were infected with HIV-1 subtype C. After HIV-1 diagnosis, they were recruited into the CAPRISA 002 cohort.

Methods:

We analyzed gag sequences from the earliest time point post infection (within 3 months of estimated time of infection). Transmission index was measured using a model which predicts the likelihood of an amino acid to be transmitted. Phylogenetic distance from a regional consensus sequence was calculated from a maximum likelihood phylogenetic tree.

Results:

Transmission index and distance from the most common (consensus) sequence have been shown to be markers of transmission fitness. We found that viruses infecting TFV gel recipients were closer to the consensus sequence of regional strains (P = 0.003) and had higher transmission index (P = 0.01). The transmission index was weakly correlated with concomitant viral load (Spearman r = 0.22, P = 0.06).

Conclusion:

Decreased acquisition risk may have increased the barrier to infection therefore selecting for fitter, more consensus-like viruses. Such virus fitness effects will need to be considered for future pre-exposure prophylaxis and vaccine trials.

Layer-by-Layer Engineered Microbicide Drug Delivery System Targeting HIV-1 gp120: Physicochemical and Biological Properties

The purpose of this study was to engineer a model anti-HIV microbicide (tenofovir) drug delivery system targeting HIV-1 envelope glycoprotein gp120 (HIV-1 g120) for the prevention of HIV sexual transmission. HIV-1 g120 and mannose responsive particles (MRP) were prepared through the layer-by-layer coating of calcium carbonate (CaCO₃) with concanavalin A (Con A) and glycogen. MRP average particle size ranged from 881.7 ± 15.45 nm to 1130 ± 15.72 nm, depending on the number of Con A layers. Tenofovir encapsulation efficiency in CaCO₃ was 74.4% with drug loading of 16.3% (w/w). MRP was non-cytotoxic to Lactobacillus crispatus, human vaginal keratinocytes (VK2), and murine macrophage RAW 264.7 cells and did not induce any significant proinflammatory nitric oxide release. Overall, compared to control, no statistically significant increase in proinflammatory cytokine IL-1α, IL-1β, IL-6, MKC, IL-7, and interferon-γ-inducible protein 10 (IP10) levels was observed. Drug release profiles in the presence of methyl α-d-mannopyranoside and recombinant HIV-1 envelope glycoprotein gp120 followed Hixson-Crowell and Hopfenberg kinetic models, indicative of a surface-eroding system. The one Con A layer containing system was found to be the most sensitive (∼2-fold increase in drug release vs control SFS:VFS) at the lowest HIV gp120 concentration tested (25 μg/mL). Percent mucoadhesion, tested ex vivo on porcine vaginal tissue, ranged from 10% to 21%, depending on the number of Con A layers in the formulation. Collectively, these data suggested that the proposed HIV-1 g120 targeting, using MRP, potentially represent a safe and effective template for vaginal microbicide drug delivery, if future preclinical studies are conclusive.

Replication Capacity of Viruses from Acute Infection Drives HIV-1 Disease Progression

The viral genotype has been shown to play an important role in HIV pathogenesis following transmission. However, the viral phenotypic properties that contribute to disease progression remain unclear. Most studies have been limited to the evaluation of Gag function in the context of a recombinant virus backbone. Using this approach, important biological information may be lost, making the evaluation of viruses obtained during acute infection, representing the transmitted virus, a more biologically relevant model. Here, we evaluate the roles of viral infectivity and the replication capacity of viruses from acute infection in disease progression in women who seroconverted in the CAPRISA 004 tenofovir microbicide trial. We show that viral replication capacity, but not viral infectivity, correlates with the set point viral load (Spearman r = 0.346; P = 0.045) and that replication capacity (hazard ratio [HR] = 4.52; P = 0.01) can predict CD4 decline independently of the viral load (HR = 2.9; P = 0.004) or protective HLA alleles (HR = 0.61; P = 0.36). We further demonstrate that Gag-Pro is not the main driver of this association, suggesting that additional properties of the transmitted virus play a role in disease progression. Finally, we find that although viruses from the tenofovir arm were 2-fold less infectious, they replicated at rates similar to those of viruses from the placebo arm. This indicates that the use of tenofovir gel did not select for viral variants with higher replication capacity. Overall, this study supports a strong influence of the replication capacity in acute infection on disease progression, potentially driven by interaction of multiple genes rather than a dominant role of the major structural gene gagIMPORTANCE HIV disease progression is known to differ between individuals, and defining which fraction of this variation can be attributed to the virus is important both clinically and epidemiologically. In this study, we show that the replication capacity of viruses isolated during acute infection predicts subsequent disease progression and drives CD4 decline independently of the viral load. This provides further support for the hypothesis that the replication capacity of the transmitted virus determines the initial damage to the immune system, setting the pace for later disease progression. However, we did not find evidence that the major structural gene gag drives this correlation, highlighting the importance of other genes in determining disease progression.

An Intravaginal Ring for the Simultaneous Delivery of an HIV-1 Maturation Inhibitor and Reverse-Transcriptase Inhibitor for Prophylaxis of HIV Transmission

Nucleocapsid 7 (NCp7) inhibitors have been investigated extensively for their role in impeding the function of HIV-1 replication machinery and their ability to directly inactivate the virus. A class of NCp7 zinc finger inhibitors, S-acyl-2-mercaptobenzamide thioesters (SAMTs), was investigated for topical drug delivery. SAMTs are inherently unstable because of their hydrolytically labile thioester bond, thus requiring formulation approaches that can lend stability. We describe the delivery of N-[2-(3,4,5-trimethoxybenzoylthio)benzoyl]-β-alaninamide (SAMT-10), as a single agent antiretroviral (ARV) therapeutic and in combination with the HIV-1 reverse-transcriptase inhibitor pyrimidinedione IQP-0528, from a hydrophobic polyether urethane (PEU) intravaginal ring (IVR) for a month. The physicochemical stability of the ARV-loaded IVRs was confirmed after 3 months at 40°C/75% relative humidity. In vitro, 25 ± 3 mg/IVR of SAMT-10 and 86 ± 13 mg/IVR of IQP-0528 were released. No degradation of the hydrolytically labile SAMT-10 was observed within the matrix. The combination of ARVs had synergistic antiviral activity when tested in in vitro cell-based assays. Toxicological evaluations performed on an organotypic EpiVaginal(™) tissue model demonstrated a lack of formulation toxicity. Overall, SAMT-10 and IQP-0528 were formulated in a stable PEU IVR for sustained release. Our findings support the need for further preclinical evaluation. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 104:3426-3439, 2015.

HIV disease progression in seroconvertors from the CAPRISA 004 tenofovir gel pre-exposure prophylaxis trial

BACKGROUND

Although antiretroviral pre-exposure prophylaxis prevents HIV acquisition, it is not known if it alters HIV disease progression. This study assesses whether tenofovir gel impacted on disease progression among CAPRISA 004 microbicide trial seroconvertors.

METHODS

Eighty-three seroconvertors from the tenofovir and placebo gel arms of the CAPRISA 004 trial were monitored prospectively for a minimum of 2 years by CD4 count and viral load (VL). Linear mixed models were fitted to HIV VL, and log rank test was used to compare time to reach CD4 counts of <350 cells per microliter.

RESULTS

Median 2-week postinfection VL was 4.74 and 4.45 log copies per milliliter in women assigned to tenofovir gel (n = 32) and placebo gel (n = 51) (P = 0.189). Corresponding 12-month postinfection VLs were 4.24 and 3.70 log copies per milliliter (P = 0.016). After adjusting for clinical and behavioral characteristics and protective HLA alleles, mean VLs within the first 2 years were 4.51 and 4.02 log copies per milliliter in women from the tenofovir and placebo arms (P = 0.013). Among women with vaginal tenofovir measurements, mean VLs were 4.53 and 4.60 log copies per milliliter in those with detectable versus undetectable levels (P = 0.840). Overall mean CD4 counts were 463 and 514 cells per microliter in women assigned to tenofovir and placebo (P = 0.290). Thirty-two women (38.6%) reached CD4 counts of <350 cells per microliter at median 9.4 months postinfection, 13 (40.6%) from the tenofovir and 19 (37.3%) from the placebo arms (P = 0.786).

CONCLUSIONS

Tenofovir gel had no impact on postinfection CD4 counts or the rate of CD4 decline. Although seroconvertors from the tenofovir arm experienced higher VLs, this did not result in a need for earlier antiretroviral therapy.

Antibody Maturation in Women Who Acquire HIV Infection While Using Antiretroviral Preexposure Prophylaxis

The CAPRISA 004 preexposure prophylaxis (PrEP) randomized trial demonstrated that women who used a vaginal gel containing the antiretroviral drug tenofovir (TFV) had a 39% lower risk of acquiring human immunodeficiency virus (HIV). It is not known whether topical TFV alters the antibody response to breakthrough HIV infection. In this study, antibody maturation was evaluated using 3 serologic assays: the BED capture enzyme immunoassay (CEIA), the Bio-Plex (Luminex) assay, and the Bio-Rad avidity assay. Tests were performed using serum samples collected 3, 6, 9, 12, 24, 36, 48, and >48 months after seroconversion from 95 women in the CAPRISA 004 trial (35 in the TFV gel arm and 60 in the placebo arm). For the BED CEIA and Luminex assay, linear mixed effects models were used to examine test results by study arm. Cox proportional hazard analysis was used to examine time to avidity cutoff. Anti-HIV antibody titers did not differ between study arms. Women assigned to TFV gel demonstrated slower antibody avidity maturation, as determined by the Bio-Rad (P = .04) and gp120 Bio-Plex (P = .028) assays. Women who were assigned to receive topical TFV but became infected had slower antibody avidity maturation, with potential implications for diagnosis and antibody-based incidence assays as access to antiretroviral therapy-based PrEP is increased.

Development of methods for cross-sectional HIV incidence estimation in a large, community randomized trial

Background

Accurate methods of HIV incidence determination are critically needed to monitor the epidemic and determine the population level impact of prevention trials. One such trial, Project Accept, a Phase III, community-randomized trial, evaluated the impact of enhanced, community-based voluntary counseling and testing on population-level HIV incidence. The primary endpoint of the trial was based on a single, cross-sectional, post-intervention HIV incidence assessment.

Methods and Findings

Test performance of HIV incidence determination was evaluated for 403 multi-assay algorithms [MAAs] that included the BED capture immunoassay [BED-CEIA] alone, an avidity assay alone, and combinations of these assays at different cutoff values with and without CD4 and viral load testing on samples from seven African cohorts (5,325 samples from 3,436 individuals with known duration of HIV infection [1 month to >10 years]). The mean window period (average time individuals appear positive for a given algorithm) and performance in estimating an incidence estimate (in terms of bias and variance) of these MAAs were evaluated in three simulated epidemic scenarios (stable, emerging and waning). The power of different test methods to detect a 35% reduction in incidence in the matched communities of Project Accept was also assessed. A MAA was identified that included BED-CEIA, the avidity assay, CD4 cell count, and viral load that had a window period of 259 days, accurately estimated HIV incidence in all three epidemic settings and provided sufficient power to detect an intervention effect in Project Accept.

Conclusions

In a Southern African setting, HIV incidence estimates and intervention effects can be accurately estimated from cross-sectional surveys using a MAA. The improved accuracy in cross-sectional incidence testing that a MAA provides is a powerful tool for HIV surveillance and program evaluation.

Intravaginal ring eluting tenofovir disoproxil fumarate completely protects macaques from multiple vaginal simian-HIV challenges

Topical preexposure prophylaxis interrupts HIV transmission at the site of mucosal exposure. Intermittently dosed vaginal gels containing the HIV-1 reverse transcriptase inhibitor tenofovir protected pigtailed macaques depending on the timing of viral challenge relative to gel application. However, modest or no protection was observed in clinical trials. Intravaginal rings (IVRs) may improve efficacy by providing long-term sustained drug delivery leading to constant mucosal antiretroviral concentrations and enhancing adherence. Although a few IVRs have entered the clinical pipeline, 100% efficacy in a repeated macaque vaginal challenge model has not been achieved. Here we describe a reservoir IVR technology that delivers the tenofovir prodrug tenofovir disoproxil fumarate (TDF) continuously over 28 d. With four monthly ring changes in this repeated challenge model, TDF IVRs generated reproducible and protective drug levels. All TDF IVR-treated macaques (n = 6) remained seronegative and simian-HIV RNA negative after 16 weekly vaginal exposures to 50 tissue culture infectious dose SHIV162p3. In contrast, 11/12 control macaques became infected, with a median of four exposures assuming an eclipse of 7 d from infection to virus RNA detection. Protection was associated with tenofovir levels in vaginal fluid [mean 1.8 × 10(5) ng/mL (range 1.1 × 10(4) to 6.6 × 10(5) ng/mL)] and ex vivo antiviral activity of cervicovaginal lavage samples. These observations support further advancement of TDF IVRs as well as the concept that extended duration drug delivery devices delivering topical antiretrovirals could be effective tools in preventing the sexual transmission of HIV in humans.

No evidence for selection of HIV-1 with enhanced gag-protease or Nef function among breakthrough infections in the CAPRISA 004 tenofovir microbicide trial

Background

Use of antiretroviral-based microbicides for HIV-1 prophylaxis could introduce a transmission barrier that inadvertently facilitates the selection of fitter viral variants among incident infections. To investigate this, we assessed the in vitro function of gag-protease and nef sequences from participants who acquired HIV-1 during the CAPRISA 004 1% tenofovir microbicide gel trial.

Methods and Results

We isolated the earliest available gag-protease and nef gene sequences from 83 individuals and examined their in vitro function using recombinant viral replication capacity assays and surface protein downregulation assays, respectively. No major phylogenetic clustering and no significant differences in gag-protease or nef function were observed in participants who received tenofovir gel versus placebo gel prophylaxis.

Conclusion

Results indicate that the partial protective effects of 1% tenofovir gel use in the CAPRISA 004 trial were not offset by selection of transmitted/early HIV-1 variants with enhanced Gag-Protease or Nef fitness.

Recommendations for the follow-up of study participants with breakthrough HIV infections during HIV/AIDS biomedical prevention studies

OBJECTIVE

To facilitate collection of cumulative data on longitudinal HIV disease outcomes during HIV prevention studies by developing recommendations for follow-up of the relatively few study participants with breakthrough infections.

DESIGN

We formed a working group to compare and contrast the various approaches taken in recent HIV prevention trials, to summarize the advantages and disadvantages associated with each, and to explore the feasibility of developing protocols for the long-term follow-up of seroconverters.

METHODS

We reviewed study designs, objectives, and assessments in 15 interventional studies that followed HIV seroconverters. Protocol team members joined discussions of the various approaches and developed recommendations.

RESULTS

Most HIV prevention clinical trials share a core set of objectives, including the description/comparison of virological, immunological, and clinical course of HIV, and sometimes a comparison of preseroconversion and postseroconversion behavior. Long-term follow-up of seroconverters can be conducted in separate studies if the transition from parent protocol is effectively managed.

CONCLUSION

We recommend the development of harmonized seroconverter protocols. Although specific research questions in the postseroconversion period may differ depending on prevention modality, harmonizing key evaluations would create an opportunity to ask overarching questions that inform the prevention field with respect to design and implementation of future combination prevention studies. Follow-up immediately postseroconversion should be conducted in the parent protocol before roll over into a follow-up protocol. Development of specimen repositories with ample volumes for future assays, standardized definitions of infection, diagnosis and seroconversion dates, and harmonization of study objectives and sample collections at key time points are important.

From the laboratory to clinical trials and back again: lessons learned from HIV prevention trials

PROBLEM

Inadequate, irrelevant, or inappropriate timing of biological specimen collection during clinical trials is a cause for delay in understanding and explaining correlates of protection and/or effectiveness, particularly at the portal of entry in the context of sexual HIV transmission and its prevention.

METHODS

We present examples of HIV prevention trials to illustrate the impact of preplanned versus unplanned laboratory science program on the interpretation of trial results and advancement of the field.

RESULTS

Of the five completed pre-exposure prophylaxis trials, only two announced main outcome results simultaneously with data on correlates of drug-related effectiveness. In four of the vaccine trials completed, the only one that showed a protective effect presented data on protection correlates significantly later.

CONCLUSION

Clinical trials must preplan collaborative immunophysiological research and prioritize biological specimen collection and storage for enhancement of research on correlates of protection. Similarly appropriate specimens should be prioritized for pathogenesis research.

Microbicides: still a long road to success

The development of efficient microbicides, the topically applied compounds that protect uninfected individuals from acquiring HIV-1, is a promising strategy to contain HIV-1 epidemics. Such microbicides should of course possess anti-HIV-1 activity, but they should also act against other genital pathogens, which facilitate HIV-1 transmission. The new trend in microbicide strategy is to use drugs currently used in HIV-1 therapy. The success of this strategy is mixed so far and is impaired by our limited knowledge of the basic mechanisms of HIV-1 transmission as well as by the inadequacy of the systems in which microbicides are tested in preclinical studies.