Pharmacokinetics and Pharmacodynamics of the Non-Nucleoside Reverse-Transcriptase Inhibitor Etravirine in Treatment-Experienced HIV-1-Infected Patients

Is Routine Therapeutic Drug Monitoring of Anti-Retroviral Agents Warranted in Children Living with HIV?

OBJECTIVE

The utility of routine therapeutic drug monitoring (TDM) in children living with HIV has not been extensively studied. The purpose of this study was to assess this strategy.

METHODS

This was a single-center, prospective observational study of routine TDM for protease inhibitors (PIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs), and integrase strand transfer inhibitors (INSTIs) in children living with HIV who were receiving antiretroviral therapy (ART) between February and December 2014. Outcome measures included the proportion of serum antiretroviral (ARV) medication concentrations in the therapeutic range (target values extrapolated from adult data) and the effect of serum concentrations on virologic control, medication adherence, and toxicity.

RESULTS

Forty-eight children with a median age of 13 years (interquartile range, 3–18) were included. Median viral load (VL) and CD4% were <40 copies/mL (range, <40–124) and 37.4% (range, 8.4–47.9), respectively. Adherence was considered excellent in 95.8% of patients. Of the 50 serum trough concentrations (PI n = 19 [38%]; NNRTI n = 27 [54%]; INSTI n = 4 [8%]), 66% (n = 33) were in the therapeutic range, 12% (n = 6) were subtherapeutic, and 22% (n = 11) were supratherapeutic. There was no statistically significant correlation between serum ARV concentrations and patient demographics, VL, CD4%, or adherence. No clinically significant adverse events were noted. One dose adjustment was made for a subtherapeutic serum raltegravir concentration, likely attributable to interaction with ritonavir.

CONCLUSIONS

This study does not support routine TDM in healthy children living with HIV who are well controlled on antiretroviral medication regimens. A more targeted strategy, such as when adherence is questioned or when there are suspected drug interactions, may be more appropriate.

HIV, aging, and adherence: an update and future directions

PURPOSE OF REVIEW

To highlight recent data on antiretroviral adherence in older people living with HIV (PLWH), describe the most relevant pharmacokinetic antiretroviral studies, and identify critical research gaps in this population.

RECENT FINDINGS

Overall, studies have found that older PLWH are more likely to be adherent to antiretroviral therapy (ART). Although multiple methods to measure adherence are available (self-report, pharmacy refills, electronic device monitors, drug concentrations), there is currently no 'gold standard' adherence measure or sufficient evidence to suggest a preferred method in older patients. Recently, studies evaluating antiretroviral concentrations in hair and dried blood spots in older patients identified no major differences when compared with younger individuals. Similarly, although pharmacokinetic studies in older PLWH are scarce, most data reveal no significant pharmacokinetic differences in the aging population. Furthermore, no specific guidelines or treatment recommendations regarding ART dose modification or long-term toxicity in aging PLWH are available, mostly because of the exclusion of this population in clinical trials.

SUMMARY

How aging influences adherence and pharmacokinetics remains poorly understood. As the population of older PLWH increases, research focusing on adherence, toxicity, drug--drug interactions, and the influence of comorbidities is needed.

Clinical Pharmacokinetics and Pharmacodynamics of Etravirine: An Updated Review

Etravirine is a second-generation non-nucleoside reverse transcriptase inhibitor (NNRTI) for the treatment of human immunodeficiency virus type 1 infection. It is a potent inhibitor of HIV reverse transcriptase and retains activity against wild-type and most NNRTI-resistant HIV. The pharmacokinetic profile of etravirine and clinical data support twice-daily dosing, although once-daily dosing has been investigated in treatment-naïve and treatment-experienced persons. Despite similar pharmacokinetic and pharmacodynamic results compared with twice-daily dosing, larger studies are needed to fully support once-daily etravirine dosing in treatment-naïve individuals. Etravirine is reserved for use in third- or fourth-line antiretroviral treatment regimens, as recommended, for example, in treatment guidelines by the US Department of Health and Human Services-Guidelines for the Use of Antiretroviral Agents in Adults and Adolescents Living with HIV. Etravirine exhibits the potential for bi-directional drug-drug interactions with other antiretrovirals and concomitant medications through its interactions with cytochrome P450 (CYP) isozymes: CYP3A4, CYP2C9, and CYP2C19. This review summarizes the pharmacokinetic and pharmacodynamic parameters of etravirine, with particular attention to information on drug-drug interactions and use in special patient populations, including children/adolescents, women, persons with organ dysfunction, and during pregnancy.

Combining biorelevant in vitro and in silico tools to investigate the in vivo performance of the amorphous solid dispersion formulation of etravirine in the fed state

INTRODUCTION

In the development of bio-enabling formulations, innovative in vivo predictive tools to understand and predict the in vivo performance of such formulations are needed. Etravirine, a non-nucleoside reverse transcriptase inhibitor, is currently marketed as an amorphous solid dispersion (Intelence® tablets). The aims of this study were 1) to investigate and discuss the advantages of using biorelevant in vitro setups to simulate the in vivo performance of Intelence® 100 mg and 200 mg tablets in the fed state, 2) to build a Physiologically Based Pharmacokinetic (PBPK) model by combining experimental data and literature information with the commercially available in silico software Simcyp® Simulator V17.1 (Certara UK Ltd.), and 3) to discuss the challenges of predicting the in vivo performance of an amorphous solid dispersion and identify the parameters which influence the pharmacokinetics of etravirine most.

METHODS

Solubility, dissolution and transfer experiments were performed in various biorelevant media simulating the fasted and fed state environment in the gastrointestinal tract. An in silico PBPK model for etravirine in healthy volunteers was developed in the Simcyp® Simulator, using in vitro results and data available from the literature as input. The impact of pre- and post-absorptive parameters on the pharmacokinetics of etravirine was investigated by simulating various scenarios.

RESULTS

In vitro experiments indicated a large effect of naturally occurring solubilizing agents on the solubility of etravirine. Interestingly, supersaturated concentrations of etravirine were observed over the entire duration of dissolution experiments on Intelence® tablets. Coupling the in vitro results with the PBPK model provided the opportunity to investigate two possible absorption scenarios, i.e. with or without implementation of precipitation. The results from the simulations suggested that a scenario in which etravirine does not precipitate is more representative of the in vivo data. On the post-absorptive side, it appears that the concentration dependency of the unbound fraction of etravirine in plasma has a significant effect on etravirine pharmacokinetics.

CONCLUSIONS

The present study underlines the importance of combining in vitro and in silico biopharmaceutical tools to advance our knowledge in the field of bio-enabling formulations. Future studies on other bio-enabling formulations can be used to further explore this approach to support rational formulation design as well as robust prediction of clinical outcomes.

Evaluation of Concomitant Antiretrovirals and CYP2C9/CYP2C19 Polymorphisms on the Pharmacokinetics of Etravirine

BACKGROUND

Etravirine is a non-nucleoside reverse transcriptase inhibitor indicated in combination with other antiretrovirals for treatment-experienced HIV patients ≥6 years of age. Etravirine is primarily metabolized by cytochrome P450 (CYP) 2C9, CYP2C19, and CYP3A. This analysis determined the impact of concomitant antiretrovirals and CYP2C9/CYP2C19 phenotype on the pharmacokinetics of etravirine.

METHODS

We used 4728 plasma concentrations from 817 adult subjects collected from four clinical studies to develop the population pharmacokinetic model. The presence of atazanavir/ritonavir, lopinavir/ritonavir, darunavir/ritonavir, tenofovir disoproxil fumarate, or enfuvirtide together with the CYP2C9 and CYP2C19 phenotype and other demographics were evaluated.

RESULTS

A one-compartment model with first-order input and a lag-time best described the data. Estimates of apparent total clearance (CL/F), apparent central volume of distribution (V _c/F), first-order absorption rate constant (k _a), and absorption lag-time were 41.7 L/h, 972 L, 1.16 h, and 1.32 h, respectively. Estimates of between-subject variability on CL/F, V _c/F, and relative bioavailability (F) were 39.4 %CV (percentage coefficient of variation), 35.9 %CV and 35.5 %CV, respectively. Between-occasion variability on F was estimated to be 30.0 %CV. CL/F increased non-linearly with body weight and creatinine clearance (CL_CR), and also varied based on CYP2C9/CYP2C19 phenotype.

CONCLUSIONS

In this analysis, body weight, CL_CR, and CYP2C9/CYP2C19 phenotype were found to describe some of the variability in CL/F. It was not possible to show an impact of concomitant antiretrovirals on the pharmacokinetics of etravirine for adults predominantly taking coadministered boosted protease inhibitors as a background antiretroviral regimen.

Pharmacokinetics of Darunavir/Ritonavir With Etravirine Both Twice Daily in Human Immunodeficiency Virus-Infected Adolescents and Young Adults

Data on the combination of darunavir/ritonavir and etravirine both given twice daily in adolescents/young adults are lacking. In this study, we assessed the pharmacokinetics of darunavir/ritonavir 600/100 mg with etravirine 200 mg twice daily in 36 treatment-experienced human immunodeficiency virus-infected adolescents and young adults and found that exposures were comparable to those reported in adults.

Pharmacokinetics and Pharmacokinetic/Pharmacodynamic Relationships of Etravirine in HIV-1-Infected, Treatment-Experienced Children and Adolescents in PIANO

PIANO (NCT00665847) investigated etravirine pharmacokinetics, efficacy, and safety in children and adolescents. Treatment-experienced, HIV-1-infected patients (≥6 to <18 years) received etravirine 5.2 mg/kg twice daily (maximum 200 mg twice daily) plus background antiretrovirals. A population pharmacokinetic model was developed, and etravirine C_0h and AUC_0-12h were estimated. Relationships among intrinsic/extrinsic factors and etravirine pharmacokinetics and pharmacokinetics with pharmacodynamics were assessed. The best model describing etravirine pharmacokinetics consisted of a single compartment with sequential zero- and first-order absorption following a lag time. Interindividual variability terms were included on clearance (CL/F) and the first-order input rate constant (KA). The final model estimates (coefficient of variation, %) for CL/F and KA were 46.3 (11) L/h and 1.07 (34) h^-1 , respectively. Overall, median (range) estimated etravirine C_0h and AUC_0-12h were 287 (2-2276) ng/mL and 4560 (62-28,865) ng · h/mL, respectively. Exposure was slightly lower in adolescents vs children. Sex and adherence did not affect etravirine pharmacokinetics. Factors significantly affecting etravirine exposure were body weight (higher with lower weight), race (lower in Asians than in white or black patients), and the use of certain HIV protease inhibitors. Virologic response (<50 copies/mL at week 48) was lower in the lowest etravirine AUC_0-12h quartile vs the upper 3 quartiles (41% vs 67% to 76%). Rash occurred more frequently in the highest quartile than in the lower 3 quartiles (52% versus 8% to 20%). Etravirine 5.2 mg/kg twice daily in treatment-experienced, HIV-1-infected children and adolescents provides comparable exposure to that in adults receiving etravirine 200 mg twice daily and is the recommended dose for children and adolescents.

Pharmacokinetics of Total and Unbound Etravirine in HIV-1-Infected Pregnant Women

BACKGROUND

Treatment of HIV-1-infected women during pregnancy protects maternal health and reduces the risk of perinatal transmission of HIV-1. However, physiologic changes that occur during pregnancy may affect drug pharmacokinetics. This phase IIIb, open-label study evaluated the effects of pregnancy on the pharmacokinetics of the nonnucleoside reverse transcriptase inhibitor etravirine.

METHODS

Eligible HIV-1-infected pregnant women (18-26 weeks gestation) on an individualized, highly active antiretroviral therapy regimen including etravirine 200 mg twice daily were enrolled. Blood samples to assess the pharmacokinetics of total and unbound etravirine were obtained at clinic visits during the second and third trimesters (24- to 28-weeks and 34- to 38-weeks gestation, respectively) and 6-12 weeks postpartum. At each time point, plasma concentrations were measured over 12 hours (12-hour time point was obtained before the second daily dose of etravirine); pharmacokinetic parameters were derived using noncompartmental analysis and were compared between pregnancy and postpartum using general linear models. Antiviral and immunologic response and safety were assessed at each visit.

RESULTS

Etravirine pharmacokinetic profiles were available for 13 of 15 enrolled women. Exposure to total etravirine was generally higher during pregnancy compared with 6-12 weeks postpartum (1.2- to 1.4-fold); the differences were less pronounced for unbound (pharmacodynamically active) etravirine. Virologic response was generally preserved throughout the study, and no perinatal transmission was observed. Etravirine was generally safe and well tolerated.

CONCLUSIONS

Etravirine 200 mg twice daily, as part of individualized combination antiretroviral therapy, may be a treatment option for HIV-1-infected pregnant women.

Etravirine combined with antiretrovirals other than darunavir/ritonavir for HIV-1-infected, treatment-experienced adults: Week 48 results of a phase IV trial

Objective:

VIOLIN (TMC125IFD3002; NCT01422330) evaluated the safety, tolerability, and pharmacokinetics of etravirine with antiretrovirals other than darunavir/ritonavir in HIV-1-infected patients.

Methods:

In a 48-week, phase IV, single-arm, multicenter study, patients on prior antiretroviral therapy (⩾8 weeks) who needed to change regimen for virologic failure (viral load ⩾ 500 copies/mL) or simplification/adverse events (viral load < 50 copies/mL) received etravirine 200 mg bid with ⩾1 other active antiretroviral, excluding darunavir/ritonavir or only nucleoside/tide reverse transcriptase inhibitors.

Results:

Of 211 treated patients, 73% (n = 155) had baseline viral load ⩾ 50 copies/mL and 27% (n = 56) had baseline viral load < 50 copies/mL. Protease inhibitors were the most common background antiretrovirals (83%). Diarrhea was the most frequent adverse event (17%). Serious adverse events (no rash) occurred in 5% of patients; none were etravirine related. Overall, median etravirine AUC_12h was 5390 ng h/mL and C_0h was 353 ng/mL (N = 199). Week 48 virologic response rates (viral load < 50 copies/mL; Food and Drug Administration Snapshot algorithm) were 48% (74/155) (baseline viral load ⩾ 50 copies/mL) and 75% (42/56) (baseline viral load < 50 copies/mL). Virologic failure rates were 42% and 13%, respectively. The most frequently emerging etravirine resistance-associated mutations in virologic failures were Y181C, E138A, and M230L. Virologic response rates for patients with baseline viral load ⩾ 50 copies/mL were 38% (30/79) (non-adherent) versus 64% (44/69) (adherent subset).

Conclusion:

Etravirine 200 mg bid in combination with antiretrovirals other than darunavir/ritonavir was well tolerated in the studied treatment-experienced HIV-1-infected population. The overall etravirine safety and tolerability profile and pharmacokinetics (specifically in those patients who were adherent) were similar to those previously observed for etravirine in HIV-1-infected adults. The relatively high level of non-adherence, also observed in the pharmacokinetic assessments, negatively impacted virologic response, especially in patients with ⩾50 copies/mL at baseline.

Etravirine Pharmacokinetics in HIV-Infected Pregnant Women

Background: The study goal was to describe etravirine pharmacokinetics during pregnancy and postpartum in HIV-infected women.

Methods: IMPAACT P1026s and PANNA are on-going, non-randomized, open-label, parallel-group, multi-center phase-IV prospective studies in HIV-infected pregnant women. Intensive steady-state 12-h pharmacokinetic profiles were performed from 2nd trimester through postpartum. Etravirine was measured at two labs using validated ultra performance liquid chromatography (detection limits: 0.020 and 0.026 mcg/mL).

Results: Fifteen women took etravirine 200 mg twice-daily. Etravirine AUC_0–12 was higher in the 3rd trimester compared to paired postpartum data by 34% (median 8.3 vs. 5.3 mcg*h/mL, p = 0.068). Etravirine apparent oral clearance was significantly lower in the 3rd trimester of pregnancy compared to paired postpartum data by 52% (median 24 vs. 38 L/h, p = 0.025). The median ratio of cord blood to maternal plasma concentration at delivery was 0.52 (range: 0.19–4.25) and no perinatal transmission occurred.

Conclusion: Etravirine apparent oral clearance is reduced and exposure increased during the third trimester of pregnancy. Based on prior dose-ranging and safety data, no dose adjustment is necessary for maternal health but the effects of etravirine in utero are unknown. Maternal health and infant outcomes should be closely monitored until further infant safety data are available.

Clinical Trial registration: The IMPAACT protocol P1026s and PANNA study are registered at ClinicalTrials.gov under NCT00042289 and NCT00825929.

Model-Based Once-Daily Darunavir/Ritonavir Dosing Recommendations in Pediatric HIV-1-Infected Patients Aged ≥3 to <12 Years

An existing population pharmacokinetic model of darunavir in adults was updated using pediatric data from two studies evaluating weight-based, once-daily dosing of darunavir/ritonavir (ARIEL, NCT00919854 and DIONE, NCT00915655). The model was then used to provide once-daily dosing recommendations for darunavir/ritonavir in pediatric patients aged ≥3 to <12 years. The final model comprised two compartments with first-order absorption and apparent clearance dependent on the concentration of α1-acid glycoprotein. The recommended darunavir/ritonavir once-daily dosing regimens in children aged ≥3 to <12 years are: 35/7 mg/kg from 10 to <15 kg, 600/100 mg from 15 to <30 kg, 675/100 mg from 30 to <40 kg, and 800/100 mg for ≥40 kg. These doses should result in exposures similar to the adult exposure after treatment with darunavir/ritonavir 800/100 mg once daily, while minimizing pill burden and allowing a switch from suspension to tablet(s) as early as possible.

Liver toxicity and risk of discontinuation in HIV/hepatitis C virus-coinfected patients receiving an etravirine-containing antiretroviral regimen: influence of liver fibrosis

OBJECTIVES

The aim of the study was to establish the risk of liver toxicity in HIV/hepatitis C virus (HCV)-coinfected patients receiving etravirine, according to the degree of liver fibrosis.

METHODS

A prospective cohort study of 211 HIV-infected patients initiating an etravirine-containing regimen was carried out. HCV coinfection was defined as a positive HCV RNA test, and baseline liver fibrosis was assessed by transient elastography. Hepatotoxicity was defined as clinical symptoms, or an aspartate aminotransferase (AST) or alanine aminotransferase (ALT) value > 5-fold higher than the upper limit of normal if baseline values were normal, or 3.5-fold higher if values were altered at baseline.

RESULTS

Overall, 145 patients (69%) were HCV coinfected, with a lower nadir (165 versus 220 cells/μL, respectively; p = 0.03) and baseline (374 versus 498 cells/μL, respectively; p = 0.04) CD4 count than monoinfected patients. Etravirine was mainly used with two nucleoside reverse transcriptase inhibitors (129; 61%) or with a boosted protease inhibitor (PI) (28%), with no significant differences according to HCV serostatus. Transient elastography in 117 patients (81%) showed a median (range) stiffness value of 8.25 (3.5-69) kPa, with fibrosis stage 1 in 43 patients (37%) and fibrosis stage 4 in 28 patients (24%). During an accumulated follow-up time of 449.3 patient-years (median 548 days), only one patient with advanced fibrosis (50.8 kPa) had grade 3-4 liver toxicity (0.7%). Transaminases changed slightly, with no significant differences compared with baseline fibrosis, and nine and six patients had grade 1 and 2 transaminase increases, respectively. Also, HCV coinfection was not associated with a higher risk of discontinuation (25% discontinued versus 21% of monoinfected patients; p = 0.39, log-rank test) or virological failure (8% versus 12%, respectively; p = 0.4).

CONCLUSIONS

Our data suggest that etravirine is a safe option for HIV/HCV-coinfected patients, including those with significant liver fibrosis.

Ageing with HIV: a multidisciplinary review

INTRODUCTION

After the introduction of highly active antiretroviral treatment, the course of HIV infection turned into a chronic disease and most of HIV-positive patients will soon be over 50 years old.

MATERIAL AND METHODS

This paper reviews the multiple aspects that physicians have to face while taking care of HIV-positive ageing patients including the definitions of frailty and the prevalence and risk factors of concomitant diseases. From a therapeutic point of view pharmacokinetic changes and antiretroviral-specific toxicities associated with ageing are discussed; finally therapeutic approaches to frailty are reviewed both in HIV-positive and negative patients.

CONCLUSION AND DISCUSSION

We conclude by suggesting that the combined use of drugs with the least toxicity potential and the promotion of healthy behaviours (including appropriate nutrition and exercise) might be the best practice for ageing HIV-positive subjects.

Antiretroviral blood levels in HIV/HCV-coinfected patients with cirrhosis after liver transplant: a report of three cases

Since the introduction of combined antiretroviral therapy, human immunodeficiency virus (HIV) infection is no longer a contraindication for solid organ transplantation. In HIV/hepatitis C virus (HCV)-coinfected patients undergoing liver transplantation, HCV-related cirrhosis, drug-drug interactions, and calcineurin inhibitors-related toxicity affect clinical outcomes. Therapeutic drug monitoring can be useful to assess antiretroviral over- or underexposure in this cohort. We report the clinical characteristics along with antiretroviral trough levels of maraviroc, darunavir, and etravirine in 3 HIV/HCV-coinfected liver transplant recipients who developed post-transplant liver cirrhosis.

Pharmacokinetics of Etravirine Combined with Atazanavir/Ritonavir and a Nucleoside Reverse Transcriptase Inhibitor in Antiretroviral Treatment-Experienced, HIV-1-Infected Patients

Objectives. TEACH (NCT00896051) was a randomized, open-label, two-arm Phase II trial to investigate the pharmacokinetic interaction between etravirine and atazanavir/ritonavir and safety and efficacy in treatment-experienced, HIV-1-infected patients. Methods. After a two-week lead-in of two nucleoside reverse transcriptase inhibitors (NRTIs) and atazanavir/ritonavir 300/100 mg, 44 patients received etravirine 200 mg bid with one NRTI, plus atazanavir/ritonavir 300/100 mg or 400/100 mg qd (n = 22 each group) over 48 weeks. Results. At steady-state etravirine with atazanavir/ritonavir 300/100 mg qd or 400/100 mg qd decreased atazanavir C min⁡ by 18% and 9%, respectively, with no change in AUC24 h or C max⁡ versus atazanavir/ritonavir 300/100 mg qd alone (Day -1). Etravirine AUC12 h was 24% higher and 16% lower with atazanavir/ritonavir 300/100 or 400/100 mg qd, respectively, versus historical controls. At Week 48, no significant differences were seen between the atazanavir/ritonavir groups in discontinuations due to adverse events (9.1% each group) and other safety parameters, the proportion of patients with viral load <50 copies/mL (intent-to-treat population, noncompleter = failure) (50.0%, atazanavir/ritonavir 300/100 mg qd versus 45.5%, 400/100 mg qd), and virologic failures (31.8% versus 27.3%, resp.). Conclusions. Etravirine 200 mg bid can be combined with atazanavir/ritonavir 300/100 mg qd and an NRTI in HIV-1-infected, treatment-experienced patients without dose adjustment.

Etravirine in treatment-experienced, HIV-1-infected children and adolescents: 48-week safety, efficacy and resistance analysis of the phase II PIANO study

OBJECTIVES

PIANO (Paediatric study of Intelence As an NNRTI Option; TMC125-C213; NCT00665847) assessed the safety/tolerability, antiviral activity and pharmacokinetics of etravirine plus an optimized background regimen (OBR) in treatment-experienced, HIV-1-infected children (≥ 6 to < 12 years) and adolescents (≥ 12 to < 18 years) over 48 weeks.

METHODS

In a phase II, open-label, single-arm study, 101 treatment-experienced patients (41 children; 60 adolescents) with screening viral load (VL) ≥ 500 HIV-1 RNA copies/mL received etravirine 5.2 mg/kg (maximum dose 200 mg) twice a day (bid) plus OBR.

RESULTS

Sixty-seven per cent of patients had previously used efavirenz or nevirapine. At week 48, the most common treatment-related grade ≥ 2 adverse event (AE) was rash (13%); 12% experienced grade 3 AEs. Only two grade 4 AEs occurred (both thrombocytopaenia, not etravirine related). At week 48, 56% of patients (68% children; 48% adolescents) achieved a virological response (VL<50 copies/mL; intent-to-treat, noncompleter=failure). Factors predictive of response were adherence > 95%, male sex, low baseline etravirine weighted genotypic score and high etravirine trough concentration (C0h ). Seventy-six patients (75%) completed the trial; most discontinuations occurred because of protocol noncompliance or AEs (8% each). Sixty-five per cent of patients were > 95% adherent by questionnaire and 39% by pill count. Forty-one patients experienced virological failure (VF; time-to-loss-of-virological-response non-VF-censored algorithm) (29 nonresponders; 12 rebounders). Of 30 patients with VF with paired baseline/endpoint genotypes, 18 (60%) developed nonnucleoside reverse transcriptase inhibitor (NNRTI) mutations, most commonly Y181C. Mean etravirine area under the plasma concentration-time curve over 12 h (AUC0-12h ; 5216 ng h/mL) and C0h (346 ng/mL) were comparable to adult target values.

CONCLUSIONS

Results with etravirine 5.2 mg/kg bid (with OBR) in this treatment-experienced paediatric population and etravirine 200 mg bid in treatment-experienced adults were comparable. Etravirine is an NNRTI option for treatment-experienced paediatric patients.

Caring for women living with HIV: gaps in the evidence

Introduction

In the management of HIV, women and men generally undergo the same treatment pathway, with gender differences being given limited consideration. This is in spite of accumulating evidence that there are a number of potential differences between women and men which may affect response to treatment, pharmacokinetics, toxicities and coping. There are also notable psychological, behavioural, social and structural factors that may have a unique impact on women living with HIV (WLWH). Despite our increasing knowledge of HIV and advances in treatment, there are significant gaps in the data relating specifically to women. One of the factors contributing to this situation is the under-representation of women in all aspects of HIV clinical research. Furthermore, there are clinical issues unique to women, including gynaecologic and breast diseases, menopause-related factors, contraception and other topics related to women's and sexual health.

Methods

Using scoping review methodology, articles from the literature from 1980 to 2012 were identified using appropriate MeSH headings reflecting the clinical status of WLWH, particularly in the areas of clinical management, sexual health, emotional wellbeing and treatment access. Titles and abstracts were scanned to determine whether they were relevant to non-reproductive health in WLWH, and papers meeting inclusion criteria were reviewed.

Results

This review summarizes our current knowledge of the clinical status of WLWH, particularly in the areas of clinical management, sexual health, emotional wellbeing and treatment access. It suggests that there are a number of gender differences in disease and treatment outcomes, and distinct women-specific issues, such as menopause and co-morbidities, that pose significant challenges to the care of WLWH.

Conclusions

Based on a review of this evidence, outstanding questions and areas where further studies are required to determine gender differences in the efficacy and safety of treatment and other clinical and psychological issues specifically affecting WLWH have been identified. Well-controlled and adequately powered clinical studies are essential to help provide answers to these questions and to contribute to activities aimed at improving the health and wellbeing of WLWH.

Assessment of Maraviroc Exposure-Response Relationship at 48 Weeks in Treatment-Experienced HIV-1-Infected Patients in the MOTIVATE Studies

Efficacy exposure–response relationships of the CCR5 antagonist maraviroc were evaluated across two phase III clinical trials. This post-hoc analysis used 48-week efficacy data from 841 treatment-experienced patients infected with CCR5-tropic human immunodeficiency virus type 1 (HIV-1), identified by the enhanced sensitivity Trofile assay. Probability of treatment success (viral RNA <50 copies/ml) was modeled using generalized additive logistic regression, testing exposure, clinical, and virologic variables. Prognostic factors for treatment success (in decreasing order of Akaike information criterion (AIC) change) were: maraviroc treatment, high-weighted overall susceptibility to background treatment, absence of an undetectable maraviroc concentration, high baseline CD4 count (BCD4), low viral load (VL), race (other than black), absence of non-R5 baseline tropism (BTRP), and absence of fosamprenavir (FPV). No concentration–response relationship was found with treatment (maraviroc vs. placebo) and presence/absence of undetectable maraviroc concentration (adherence marker) in the model. The maraviroc doses studied (300 or 150 mg with potent CYP3A4 inhibitors once (q.d.)/twice daily (b.i.d.)) deliver concentrations near the top of the concentration–response curve.

Pharmacokinetic interaction between etravirine or darunavir/ritonavir and artemether/lumefantrine in healthy volunteers: a two-panel, two-way, two-period, randomized trial

OBJECTIVES

Etravirine is a substrate and inducer of cytochrome P450 (CYP) 3A and a substrate and inhibitor of CYP2C9 and CYPC2C19. Darunavir/ritonavir is a substrate and inhibitor of CYP3A. Artemether and lumefantrine are primarily metabolized by CYP3A; artemether is also metabolized to a lesser extent by CYP2B6, CYP2C9 and CYP2C19. Artemether has an active metabolite, dihydroartemisinin. The objective was to investigate pharmacokinetic interactions between darunavir/ritonavir or etravirine and arthemether/lumefrantrine.

METHODS

This single-centre, randomized, two-way, two-period cross-over study included 33 healthy volunteers. In panel 1, 17 healthy volunteers received two treatments (A and B) in random order, with a washout period of 4 weeks between treatments: treatment A: artemether/lumefantrine 80/480 mg alone, in a 3-day course; treatment B: etravirine 200 mg twice a day (bid) for 21 days with artemether/lumefantrine 80/480 mg from day 8 (a 3-day treatment course). In panel 2, another 16 healthy volunteers received two treatments, similar to those in panel 1 but instead of etravirine, darunavir/ritonavir 600/100 mg bid was given.

RESULTS

Overall, 28 of the 33 volunteers completed the study. Co-administration of etravirine reduced the area under the plasma concentration-time curve (AUC) of artemether [by 38%; 90% confidence interval (CI) 0.48-0.80], dihydroartemisinin (by 15%; 90% CI 0.75-0.97) and lumefantrine (by 13%; 90% CI 0.77-0.98) at steady state. Co-administration of darunavir/ritonavir reduced the AUC of artemether (by 16%; 90% CI 0.69-1.02) and dihydroartemisinin (by 18%; 90% CI 0.74-0.91) but increased lumefantrine (2.75-fold; 90% CI 2.46-3.08) at steady state. Co-administration of artemether/lumefantrine had no effect on etravirine, darunavir or ritonavir AUC. No drug-related serious adverse events were reported during the study.

CONCLUSIONS

Co-administration of etravirine with artemether/lumefantrine may lower the antimalarial activity of artemether and should therefore be used with caution. Darunavir/ritonavir can be co-administered with artemether/lumefantrine without dose adjustment but should be used with caution.

Pharmacogenetics-based population pharmacokinetic analysis of etravirine in HIV-1 infected individuals

OBJECTIVES

Etravirine (ETV) is metabolized by cytochrome P450 (CYP) 3A, 2C9, and 2C19. Metabolites are glucuronidated by uridine diphosphate glucuronosyltransferases (UGT). To identify the potential impact of genetic and non-genetic factors involved in ETV metabolism, we carried out a two-step pharmacogenetics-based population pharmacokinetic study in HIV-1 infected individuals.

MATERIALS AND METHODS

The study population included 144 individuals contributing 289 ETV plasma concentrations and four individuals contributing 23 ETV plasma concentrations collected in a rich sampling design. Genetic variants [n=125 single-nucleotide polymorphisms (SNPs)] in 34 genes with a predicted role in ETV metabolism were selected. A first step population pharmacokinetic model included non-genetic and known genetic factors (seven SNPs in CYP2C, one SNP in CYP3A5) as covariates. Post-hoc individual ETV clearance (CL) was used in a second (discovery) step, in which the effect of the remaining 98 SNPs in CYP3A, P450 cytochrome oxidoreductase (POR), nuclear receptor genes, and UGTs was investigated.

RESULTS

A one-compartment model with zero-order absorption best characterized ETV pharmacokinetics. The average ETV CL was 41 (l/h) (CV 51.1%), the volume of distribution was 1325 l, and the mean absorption time was 1.2 h. The administration of darunavir/ritonavir or tenofovir was the only non-genetic covariate influencing ETV CL significantly, resulting in a 40% [95% confidence interval (CI): 13-69%] and a 42% (95% CI: 17-68%) increase in ETV CL, respectively. Carriers of rs4244285 (CYP2C19*2) had 23% (8-38%) lower ETV CL. Co-administered antiretroviral agents and genetic factors explained 16% of the variance in ETV concentrations. None of the SNPs in the discovery step influenced ETV CL.

CONCLUSION

ETV concentrations are highly variable, and co-administered antiretroviral agents and genetic factors explained only a modest part of the interindividual variability in ETV elimination. Opposing effects of interacting drugs effectively abrogate genetic influences on ETV CL, and vice-versa.

Etravirine for the treatment of HIV/AIDS

INTRODUCTION

Etravirine (TMC125) is an orally administered second-generation non-nucleoside reverse transcriptase inhibitor (NNRTI) that is approved in treatment-experienced patients as addition to an optimized background therapy (OBT).

AREAS COVERED

A Medline search was conducted of Phase II - IV clinical trials, as well as a review of abstracts from major HIV and infectious disease conferences from 2010 - 2013, involving etravirine.

EXPERT OPINION

Etravirine is a well-tolerated NNRTI with a good safety profile and a higher genetic barrier for resistance compared to first-generation NNRTIs. Rash is a potential side effect but remains mostly mild to moderate. The necessity of taking it twice daily with food (200 mg bid.), potential pharmacokinetic interactions and low concentrations in the central nervous system (CNS) represent limitations. The efficacy of once daily etravirine (400 mg qid.) and the use in treatment modification/simplification strategies requires further research. Despite its favorable profile, etravirine is currently not sufficiently investigated nor approved for use in treatment-naïve patients which should be balanced against its potential as a backup NNRTI and the broad cross-resistance conferred by etravirine failure to other NNRTIs. Etravirine should be avoided following treatment failure with regimens containing rilpivirine, another second-generation NNRTI.

Clinical pharmacokinetics of antiretroviral drugs in older persons

INTRODUCTION

Combination antiretroviral therapy has enabled HIV-infected persons to reach older ages in high numbers. Hepatic and renal changes that normally occur with advancing age occur earlier and with higher incidence in HIV-infected individuals. A limited number of prospective controlled studies have demonstrated small reductions (17 to 41%) in lopinavir, atazanavir and lamivudine clearance in older versus younger adults. A much larger number of retrospective studies in adults (age range ∼ 20 to 60 years), including all antiretroviral drugs, have evaluated age as a covariate for pharmacokinetics. Most studies did not detect substantial associations between drug exposures and age.

AREAS COVERED

This review summarizes antiretroviral drug pharmacokinetics in older persons. The authors review articles from PubMed (search terms: elderly, antiretroviral, pharmacokinetics) in addition to the bibliographies of those selected.

EXPERT OPINION

The evidence to date does not support major pharmacokinetic changes in adults between ∼ 20 and 60 years of age. However, additional prospective, well-controlled studies are needed in more persons > 60 years, including those with frailty and comorbidities, with assessment of unbound drug clearance, and incorporation of adherence, pharmacogenetics and concomitant medications. Until then, guidelines for drug-drug interactions and dosing in renal and hepatic impairment should be followed in older HIV-infected individuals.

HIV nonnucleoside reverse transcriptase inhibitors and trimethoprim-sulfamethoxazole inhibit plasmodium liver stages

BACKGROUND

Although nonnucleoside reverse transcriptase inhibitors (NNRTIs) are usually part of first-line treatment regimens for human immunodeficiency virus (HIV), their activity on Plasmodium liver stages remains unexplored. Additionally, trimethoprim-sulfamethoxazole (TMP-SMX), used for opportunistic infection prophylaxis in HIV-exposed infants and HIV-infected patients, reduces clinical episodes of malaria; however, TMP-SMX effect on Plasmodium liver stages requires further study.

METHODS

We characterized NNRTI and TMP-SMX effects on Plasmodium liver stages in vivo using Plasmodium yoelii. On the basis of these results, we conducted in vitro studies assessing TMP-SMX effects on the rodent parasites P. yoelii and Plasmodium berghei and on the human malaria parasite Plasmodium falciparum.

RESULTS

Our data showed NNRTI treatment modestly reduced P. yoelii liver stage parasite burden and minimally extended prepatent period. TMP-SMX administration significantly reduced liver stage parasite burden, preventing development of patent parasitemia in vivo. TMP-SMX inhibited development of rodent and P. falciparum liver stage parasites in vitro.

CONCLUSIONS

NNRTIs modestly affect liver stage Plasmodium parasites, whereas TMP-SMX prevents patent parasitemia. Because drugs that inhibit liver stages target parasites when they are present in lower numbers, these results may have implications for eradication efforts. Understanding HIV drug effects on Plasmodium liver stages will aid in optimizing treatment regimens for HIV-exposed and HIV-infected infected patients in malaria-endemic areas.

Biotransformation of the antiretroviral drug etravirine: metabolite identification, reaction phenotyping, and characterization of autoinduction of cytochrome P450-dependent metabolism

Etravirine (ETR) is a second-generation non-nucleoside reverse transcriptase inhibitor prescribed for the treatment of HIV-1. By using human liver microsomes (HLMs), cDNA-expressed cytochromes P450 (P450s), and UDP-glucuronosyltransferases (UGTs), the routes of ETR metabolism were defined. Incubations with cDNA-expressed P450 isozymes and chemical inhibition studies using HLMs indicated that CYP2C19 is primarily responsible for the formation of both the major monohydroxylated and dihydroxylated metabolites of ETR. Tandem mass spectrometry suggested that these metabolites were produced via monomethylhydroxylation and dimethylhydroxylation of the dimethylbenzonitrile moiety. Formation of these monohydroxy and dihydroxy metabolites was decreased by 75 and 100%, respectively, in assays performed using HLMs that were genotyped as homozygous for the loss-of-function CYP2C19*2 allele compared with formation by HLMs genotyped as CYP2C19*1/*1. Two monohydroxylated metabolites of lower abundance were formed by CYP3A4, and interestingly, although CYP2C9 showed no activity toward the parent compound, this enzyme appeared to act in concert with CYP3A4 to form two minor dihydroxylated products of ETR. UGT1A3 and UGT1A8 were demonstrated to glucuronidate a CYP3A4-dependent monohydroxylated product. In addition, treatment of primary human hepatocytes with ETR resulted in 3.2-, 5.2-, 11.8-, and 17.9-fold increases in CYP3A4 mRNA levels 6, 12, 24, and 72 h after treatment. The presence of the pregnane X receptor antagonist sulforaphane blocked the ETR-mediated increase in CYP3A4 mRNA expression. Taken together, these data suggest that ETR and ETR metabolites are substrates of CYP2C19, CYP3A4, CYP2C9, UGT1A3, and UGT1A8 and that ETR is a PXR-dependent modulator of CYP3A4 mRNA levels.

Pharmacokinetics and Pharmacodynamics of Darunavir and Etravirine in HIV-1-Infected, Treatment-Experienced Patients in the Gender, Race, and Clinical Experience (GRACE) Trial

Objectives. Evaluation of pharmacokinetics and pharmacodynamics of darunavir and etravirine among HIV-1-infected, treatment-experienced adults from GRACE, by sex and race. Methods. Patients received darunavir/ritonavir 600/100mg twice daily plus other antiretrovirals, which could include etravirine 200mg twice daily. Population pharmacokinetics for darunavir and etravirine were determined over 48 weeks and relationships assessed with virologic response and safety. Rich sampling for darunavir, etravirine, and ritonavir was collected in a substudy at weeks 4, 24, and 48. Results. Pharmacokinetics were estimated in 376 patients for darunavir and 190 patients for etravirine. Median darunavir AUC(12h) and C(0h) were 60,642ng·h/mL and 3624ng/mL, respectively; and for etravirine were 4183ng · h/mL and 280ng/mL, respectively. There were no differences in darunavir or etravirine AUC(12h) or C(0h) by sex or race. Age, body weight, or use of etravirine did not affect darunavir exposure. No relationships were seen between darunavir pharmacokinetics and efficacy or safety. Patients with etravirine exposure in the lowest quartile generally had lower response rates. Rich sampling showed no time-dependent relationship for darunavir, etravirine, or ritonavir exposure over 48 weeks. Conclusions. Population pharmacokinetics showed no relevant differences in darunavir or etravirine exposure by assessed covariates. Lower etravirine exposures were associated with lower response rates.

Pharmacokinetics and short-term safety and tolerability of etravirine in treatment-experienced HIV-1-infected children and adolescents

OBJECTIVES

To evaluate the pharmacokinetics, weight-based dose selection and short-term safety and tolerability of etravirine in HIV-1-infected children and adolescents.

DESIGN

Phase I, nonrandomized, open-label study in two stages.

METHODS

Children and adolescents aged at least 6 years to 17 years or less on a stable lopinavir/ritonavir-based antiretroviral regimen with HIV-1 RNA plasma viral load less than 50 copies/ml were enrolled. In both stages, etravirine (4 mg/kg twice daily in stage I, 5.2 mg/kg twice daily in stage II), added to the existing antiretroviral regimen, was administered for 7 days followed by a morning dose and 12-h pharmacokinetic assessment on day 8. Pharmacokinetic parameters were determined using noncompartmental analysis. Data were compared with those previously established in HIV-1-infected adults on a similar etravirine (200 mg twice daily) combination antiretroviral regimen.

RESULTS

Twenty-one patients were recruited to each stage; 19 and 20 had evaluable pharmacokinetics in stages I and II, respectively. Mean (SD) maximum plasma concentrations in stages I and II were 495 (453) and 757 ng/ml (680), respectively; area under the plasma concentration-time curve over 12 h was 4050 (3602) and 6141 ng h/ml (5586), respectively. Statistical/qualitative comparisons showed comparable exposures with adults in stage II; however, the upper 90% confidence interval fell outside the predefined range. Plasma viral load remained undetectable on day 8 in all patients, and etravirine was well tolerated at both doses.

CONCLUSION

Etravirine 5.2 mg/kg was well tolerated in this study and this dose was selected for further investigation in clinical trials.

Acceptable plasma concentrations of raltegravir and etravirine when administered by gastrostomy tube in a patient with advanced multidrug-resistant human immunodeficiency virus infection

STUDY OBJECTIVE

To determine whether the absorption of four antiretroviral agents-raltegravir, etravirine, emtricitabine, and tenofovir-is compromised when administered by gastrostomy tube.

DESIGN

Pharmacokinetic analysis.

SETTING

University medical center.

PATIENT

A 52-year-old African-American man coinfected with advanced multidrug-resistant human immunodeficiency virus (HIV) and chronic hepatitis B, who was receiving treatment with raltegravir, etravirine, emtricitabine, and tenofovir, and developed ulcerative esophagitis with perforation, requiring a gastrostomy tube.

MEASUREMENTS AND MAIN RESULTS

Due to the patient's esophageal perforations, all nutrition and drug therapy had to be provided by gastrostomy tube. As his antiretroviral regimen of raltegravir, etravirine, and emtricitabine-tenofovir was not available in liquid or powder formulations, the oral tablets were crushed or dispersed and mixed with water, then administered by gastrostomy tube. To ensure that the absorption of the drugs was sufficient for antiretroviral response, plasma samples were collected at 2 hours and 12 hours after dosing, and drug concentrations were quantitated by using validated assays. The 2- and 12-hour postdose plasma concentrations were 1220 and 446 ng/ml for raltegravir, 212 and 274 ng/ml for etravirine, 1148 and 164 ng/ml for emtricitabine, and 320 and 94 ng/ml for tenofovir, respectively. The patient's plasma concentrations were then compared with those in published pharmacokinetic studies of oral regimens administered to HIV-infected persons and healthy volunteers. Overall, the plasma concentrations of the antiretrovirals administered by gastrostomy tube were similar to published values. No drug toxicities were observed in this patient.

CONCLUSION

These pharmacokinetic data suggest that absorption of raltegravir, etravirine, emtricitabine, and tenofovir was not compromised when the drugs were administered by gastrostomy tube. These findings provide a basis for further investigation of the pharmacokinetics, safety, tolerance, and antiretroviral response to raltegravir, etravirine, and emtricitabine-tenofovir when the oral route of administration is not possible.

Pharmacokinetic interactions between etravirine and non-antiretroviral drugs

Etravirine (formerly TMC125) is a non-nucleoside reverse transcriptase inhibitor (NNRTI) with activity against wild-type and NNRTI-resistant strains of HIV-1. Etravirine has been approved in several countries for use as part of highly active antiretroviral therapy in treatment-experienced patients. In vivo, etravirine is a substrate for, and weak inducer of, the hepatic cytochrome P450 (CYP) isoenzyme 3A4 and a substrate and weak inhibitor of CYP2C9 and CYP2C19. Etravirine is also a weak inhibitor of P-glycoprotein. An extensive drug-drug interaction programme in HIV-negative subjects has been carried out to assess the potential for pharmacokinetic interactions between etravirine and a variety of non-antiretroviral drugs. Effects of atorvastatin, clarithromycin, methadone, omeprazole, oral contraceptives, paroxetine, ranitidine and sildenafil on the pharmacokinetic disposition of etravirine were of no clinical relevance. Likewise, etravirine had no clinically significant effect on the pharmacokinetics of fluconazole, methadone, oral contraceptives, paroxetine or voriconazole. No clinically relevant interactions are expected between etravirine and azithromycin or ribavirin, therefore, etravirine can be combined with these agents without dose adjustment. Fluconazole and voriconazole increased etravirine exposure 1.9- and 1.4-fold, respectively, in healthy subjects, however, no increase in the incidence of adverse effects was observed in patients receiving etravirine and fluconazole during clinical trials, therefore, etravirine can be combined with these antifungals although caution is advised. Digoxin plasma exposure was slightly increased when co-administered with etravirine. No dose adjustments of digoxin are needed when used in combination with etravirine, however, it is recommended that digoxin levels should be monitored. Caution should be exercised in combining rifabutin with etravirine in the presence of certain boosted HIV protease inhibitors due to the risk of decreased exposure to etravirine. Although adjustments to the dose of clarithromycin are unnecessary for the treatment of most infections, the use of an alternative macrolide (e.g. azithromycin) is recommended for the treatment of Mycobacterium avium complex infection since the overall activity of clarithromycin against this pathogen may be altered when co-administered with etravirine. Dosage adjustments based on clinical response are recommended for clopidogrel, HMG-CoA reductase inhibitors (e.g. atorvastatin) and for phosphodiesterase type-5 inhibitors (e.g. sildenafil) because changes in the exposure of these medications in the presence of co-administered etravirine may occur. When co-administered with etravirine, a dose reduction or alternative to diazepam is recommended. When combining etravirine with warfarin, the international normalized ratio (INR) should be monitored. Systemic dexamethasone should be co-administered with caution, or an alternative to dexamethasone be found as dexamethasone induces CYP3A4. Caution is also warranted when co-administering etravirine with some antiarrhythmics, calcineurin inhibitors (e.g. ciclosporin) and antidepressants (e.g. citalopram). Co-administration of etravirine with some antiepileptics (e.g. carbamazepine and phenytoin), rifampicin (rifampin), rifapentine or preparations containing St John's wort (Hypericum perforatum) is currently not recommended as these are potent inducers of CYP3A and/or CYP2C and may potentially decrease etravirine exposure. Antiepileptics that are less likely to interact based on their known pharmacological properties include gabapentin, lamotrigine, levetiracetam and pregabalin. Overall, pharmacokinetic and clinical data show etravirine to be well tolerated and generally safe when given in combination with non-antiretroviral agents, with minimal clinically significant drug interactions and no need for dosage adjustments of etravirine in any of the cases, or of the non-antiretroviral agent in the majority of cases studied.