A Proof‐of‐Concept Study of Short‐Cycle Intermittent Antiretroviral Therapy with a Once‐Daily Regimen of Didanosine, Lamivudine, and Efavirenz for the Treatment of Chronic HIV Infection

D’un protocole de soin au succès d’un essai clinique

Les innovations pour traiter l’infection par le virus de l’immunodéficience humaine (VIH) n’ont pas cessé depuis les premières monothérapies et, en 1996, les premières trithérapies. L’une d’elles vient d’être validée par l’essai ANRS QUATUOR. Elle consiste à prendre deux fois moins de médicaments, en rendant le traitement intermittent. À la demande des patients non adhérents à sa prescription standard, Jacques Leibowitch a encadré cette pratique dès 2002, en s’appuyant sur une étude transgressant le dogme de l’adhésion stricte au traitement quotidien. Ce concept de traitement à temps partiel provenait des travaux du groupe d’Anthony Fauci, mais il le revisitera pour le pousser à son apogée avec la cohorte Iccarre. Son intention strictement thérapeutique s’inscrivit initialement dans le cadre du protocole de soin Iccarre qui, en 2020, comptait 96 patients, majoritairement en réduction médicamenteuse de 70 % grâce à l’ultra-intermittence thérapeutique. Il a posé les bases de l’essai contrôlé QUATUOR dont le résultat, récemment publié, montre la non infériorité des traitements intermittents à 4 jours/7 de médicaments par rapport au traitement standard.

Pharmacological data of a successful 4-days-a-week regimen in HIV antiretroviral therapy (ANRS 162-4D trial)

INTRODUCTION

Few data are available on plasma concentrations of antiretroviral therapy (ARV) during intermittent treatment.

OBJECTIVE

To compare plasma concentrations in OFF vs ON treatment periods at several time points during treatment.

METHODS

During a successful 48-week multicenter study (ANRS 162-4D trial) of 4 days with treatment (ON) followed by 3 days without treatment (OFF) in adults treated by two nucleoside analogues and a third agent belonging to a boosted protease-inhibitor (PI, darunavir [DRV], atazanavir [ATV], lopinavir [LPV]) or a non-nucleoside-reverse-transcriptase inhibitor (NNRTI, efavirenz [EFV], etravirine [ETR], rilpivirine [RPV]) conducted in 100 patients (96% success), we determined the plasma concentrations of ARV. Blood samples were collected for analysis at inclusion (W0, 7/7 strategy for all patients), W16 and W40 (ON) and at W4, W8, W12, W24, W32 and W48 (OFF).

RESULTS

A total of 866 samples was analysed. Plasma concentrations were not statistically lower after 4 days (ON) vs 7/7 days of treatment except for RPV (-30 ng/mL at 4/7, P = 0.003). Significant lower plasma concentrations were observed for OFF vs ON except for ETR (n = 5, P = 0.062). Overall, 87.1% of ON concentrations (ATV 92.1%, DRV 51.1%, LPV 62.5%, EFV 94.4%, ETR 100% and RPV 94.9%) and 21.8% of OFF concentrations (ATV 1.4%, DRV 0.0%, LPV 0.0%, EFV 16.0%, ETR 92.6% and RPV 39.0%) were above the theoretical limit of efficacy of the molecule. In the OFF period, 85.8% of PI concentrations were under the limit of quantification, while 98.0% of NNRTI concentrations were quantifiable.

CONCLUSION

Despite low/undetectable PI/NNRTI plasma concentrations in the OFF period, patients maintained an undetectable viral load. The mechanistic explanation should be investigated.

Effects on immune system and viral reservoir of a short-cycle antiretroviral therapy in virologically suppressed HIV-positive patients

BACKGROUND

Atripla dose reduction decreases subclinical toxicity and maintains viral suppression in HIV+ individuals but the virological efficacy and immunological safety of this strategy needs to be further confirmed.

METHODS

Virologically suppressed HIV-infected adults on Atripla once-daily were randomized 1 : 1 to reduce therapy to 3 days a week (3W, n = 30) or to maintain it unchanged (once-daily, n = 31). HIV-1 reservoir (total and integrated HIV-1 DNA in CD4 cells) and immunological cell activation (CD38 and HLA-DR), senescence (CD57 and CD28), apoptosis (annexinV) as well as T-naive, effector memory (TEM) (CCR7, CD45RA) and stem cell memory (TSCM) (CD954 and CD27) populations were measured at baseline, 24 and 48 weeks.

RESULTS

No differences on activation, senescence or apoptosis of both CD4 and CD8 T cells were observed on follow-up. Nave CD4 T-cell proportion showed a significant decrease in the 3W group (mean ± SD): 24.6 ± 13.7 vs. 20.5 ± 12.9 (P = 0.002). No differences in both plasma viral load and HIV reservoir were detected on follow-up. CD4 TSCM levels at 48 weeks correlated with basal integrated HIV-1 DNA in the 3W group but not in the once-daily group. A post hoc analysis of data prior to the study entry revealed a higher viral load zenith and a trend to lower CD4 nadir in 3W vs. once-daily group.

CONCLUSION

No significant immunological or viral changes were induced in the 3W group confirming the virological efficacy and immunogical safety of this strategy. In-depth virological and immunological analyses are useful in providing additional information in antiretroviral switching studies (Clinical Trials.gov: NCT01778413).

Four-days-a-week antiretroviral maintenance therapy in virologically controlled HIV-1-infected adults: the ANRS 162-4D trial

Background

Intermittent treatment could improve the convenience, tolerability and cost of ART, as well as patients' quality of life. We conducted a 48 week multicentre study of a 4-days-a-week antiretroviral regimen in adults with controlled HIV-1-RNA plasma viral load (VL).

Methods

Eligible patients were adults with VL < 50 copies/mL for at least 1 year on triple therapy with a ritonavir-boosted PI (PI/r) or an NNRTI. The study protocol consisted of the same regimen taken on four consecutive days per week followed by a 3 day drug interruption. The primary outcome was the proportion of participants remaining in the strategy with VL < 50 copies/mL up to week 48. The study was designed to show an observed success rate of > 90%, with a power of 87% and a 5% type 1 error. The study was registered with ClinicalTrials.gov (NCT02157311) and EudraCT (2014-000146-29).

Results

One hundred patients (82 men), median age 47 years (IQR 40-53), were included. They had been receiving ART for a median of 5.1 (IQR 2.9-9.3) years and had a median CD4 cell count of 665 (IQR 543-829) cells/mm3. The ongoing regimen included PI/r in 29 cases and NNRTI in 71 cases. At 48 weeks, 96% of participants (95% CI 90%-98%) had no failure while remaining on the 4-days-a-week regimen. Virological failure occurred in three participants, who all resumed daily treatment and became resuppressed. One participant stopped the strategy. No severe treatment-related events occurred.

Conclusions

Antiretroviral maintenance therapy 4 days a week was effective for 48 weeks in 96% of patients, leading to potential reduction of long-term toxicities, high adherence to the antiretroviral regimen and drug cost saving.

Weekends-off efavirenz-based antiretroviral therapy in HIV-infected children, adolescents, and young adults (BREATHER): a randomised, open-label, non-inferiority, phase 2/3 trial

BACKGROUND

For HIV-1-infected young people facing lifelong antiretroviral therapy (ART), short cycle therapy with long-acting drugs offers potential for drug-free weekends, less toxicity, and better quality-of-life. We aimed to compare short cycle therapy (5 days on, 2 days off ART) versus continuous therapy (continuous ART).

METHODS

In this open-label, non-inferiority trial (BREATHER), eligible participants were aged 8-24 years, were stable on first-line efavirenz with two nucleoside reverse transcriptase inhibitors, and had HIV-1 RNA viral load less than 50 copies per mL for 12 months or longer. Patients were randomly assigned (1:1) to remain on continuous therapy or change to short cycle therapy according to a computer-generated randomisation list, with permuted blocks of varying size, stratified by age and African versus non-African sites; the list was prepared by the trial statistician and randomisation was done via a web service accessed by site clinician or one of the three coordinating trials units. The primary outcome was the proportion of participants with confirmed viral load 50 copies per mL or higher at any time up to the 48 week assessment, estimated with the Kaplan-Meier method. The trial was powered to exclude a non-inferiority margin of 12%. Analyses were intention to treat. The trial was registered with EudraCT, number 2009-012947-40, ISRCTN, number 97755073, and CTA, number 27505/0005/001-0001.

FINDINGS

Between April 1, 2011, and June 28, 2013, 199 participants from 11 countries worldwide were randomly assigned, 99 to the short cycle therapy and 100 to continuous therapy, and were followed up until the last patient reached 48 weeks. 105 (53%) were men, median age was 14 years (IQR 12-18), and median CD4 cell count was 735 cells per μL (IQR 576-968). Six (6%) patients assigned to the short cycle therapy versus seven (7%) assigned to continuous therapy had confirmed viral load 50 copies per mL or higher (difference -1·2%, 90% CI -7·3 to 4·9, non-inferiority shown). 13 grade 3 or 4 events occurred in the short cycle therapy group and 14 in the continuous therapy group (p=0·89). Two ART-related adverse events (one gynaecomastia and one spontaneous abortion) occurred in the short cycle therapy group compared with 14 (p=0·02) in the continuous therapy group (five lipodystrophy, two gynaecomastia, one suicidal ideation, one dizziness, one headache and syncope, one spontaneous abortion, one neutropenia, and two raised transaminases).

INTERPRETATION

Non-inferiority of maintaining virological suppression in children, adolescents, and young adults was shown for short cycle therapy versus continous therapy at 48 weeks, with similar resistance and a better safety profile. This short cycle therapy strategy is a viable option for adherent HIV-infected young people who are stable on efavirenz-based ART.

FUNDING

UK National Institute for Health Research Health Technology Assessment; UK Medical Research Council; European Commission; PENTA Foundation; INSERM SC10-US19, France.

Four days a week or less on appropriate anti-HIV drug combinations provided long-term optimal maintenance in 94 patients: the ICCARRE project

Short, intraweekly cycles of anti-HIV combinations have provided intermittent, effective therapy (on 48 patients) (1). The concept is now extended to 94 patients on treatment, 4 days per week or less, over a median of 2.7 discontinuous treatment years per patient. On suppressive combinations, 94 patients volunteered to treatment, 5 and 4 days per week, or reduced stepwise to 4, 3, 2, and 1 days per week in 94, 84, 66, and 12 patients, respectively, on various triple, standard, antiviral combinations, or nonregistered, quadruple, antiviral combinations. Ninety-four patients on treatment 4 days per week aggregated 165 intermittent treatment years; no viral breakthrough was observed over 87 average treatment weeks per patient, 63 of 94 having passed 2.5 intermittent treatment years on any of the antiviral combinations prescribed. On the hyperintermittent treatment of 3, 2, and 1 days per week, HIV RNA surged >50 copies, 4 weeks apart, in 18 instances (6.8 viral escapes/100 hyperdiscontinuous maintenance years). Viral escapes could have been a result of erratic adherence (EA) to regimen or follow-up (3 patients)--drug taken at half of the daily recommended dosage (8 patients) and/or overlooked archival-resistant HIVs from antecedent treatment failures (6 patients). Aside from the above circumstances, HIV unexpectedly rebounded in 3 patients on 2 days per week treatment and 1 patient on 1 day per week treatment, posting 2.2 intrinsic viral escapes/100 highly discontinuous treatment years. All 18 escapes were eventually reversed by 7 days per week salvage combinations, and 11 of 18 patients have been back for a second course of intermittent therapy, 4 days per week or less. Both cell-activation markers on the surface of T lymphocytes and cell-bound HIV DNA levels remained stable or declined. CD4/CD8 ratios rose to ≥1 in 35% of patients, whereas CD4 counts went ≥500/µl in 75%. These values were previously 7 and 40%, respectively, on 7 days per week therapy. In our aging, long, HIV-enduring, multitreated patient cohort, treatment 4 days per week and less over 421 intermittent treatment years reduced prescription medicines by 60%--equivalent to 3 drug-free/3 virus-free remission year per patient--actually sparing €3 million on just 94 patients at the cost of 2.2 intrinsic viral failure/100 hyperintermittent treatment years. At no risk of viral escape, maintenance therapy, 4 days per week, would quasiuniversally offer 40% cuts off of current overprescriptions.

Antiretroviral drugs for prevention of mother-to-child transmission: pharmacologic considerations for a public health approach

OBJECTIVE

Efavirenz-based antiretroviral therapy is recommended for prevention of mother-to-child transmission of HIV with two programmatic options: lifelong therapy for all women or treatment until cessation of breastfeeding. However, the risk of HIV resistance emerging after discontinuing efavirenz-based antiretroviral therapy is unclear. We review present knowledge surrounding the emergence of resistance after stopping efavirenz-based antiretroviral regimens.

DESIGN

An expert review.

METHODS

A literature review was conducted to identify studies assessing risk for emergence of efavirenz-related resistance following discontinuation of efavirenz-based antiretroviral regimens containing either lamivudine and zidovudine or tenofovir disoproxil fumarate and lamivudine. Discontinuation strategies including the use of 'pharmacologic tails' are discussed in the light of what is known about the pharmacology of the drugs.

RESULTS

We found no head-to-head comparisons between zidovudine, lamivudine and efavirenz and tenofovir disoproxil fumarate, lamivudine and efavirenz. The risk for HIV resistance exists, even with a 5-7 day tail of zidovudine and lamivudine. For tenofovir disoproxil fumarate, lamivudine and efavirenz, we found no clinical data to inform a recommendation for a tail.

CONCLUSION

In order to prevent emergence of resistance, a tail of at least 2 weeks in duration may be required when discontinuing efavirenz in a regimen containing zidovudine and lamivudine. Studies are needed to characterize the risk of resistance among women who discontinue tenofovir disoproxil fumarate, lamivudine and efavirenz.

On the role of resonance in drug failure under HIV treatment interruption

Background

The application of highly active antiretroviral therapy (HAART) against HIV can reduce and maintain viral load below detection limit in many patients. Continuous HAART, however, can have severe side effects. In this context, structured treatment interruptions (STI) were considered to be a promising strategy. However, using CD4 cell count to guide intermittent therapy starting and stopping points, the SMART study (strategies for management of antiretroviral therapy), revealed that STI were associated with increased risk of AIDS and other complications. Additionally, short-term periodic (e.g. one week on / one week off) interruption therapies have shown virus rebound exceeding a given “failure threshold”, without any evidence for the evolution of drug resistance. Currently, the only hypothesis explaining the failure of STI is the “resonance hypothesis”, which posits that treatment failure is due to a resonance effect between the drug treatment and the viral population. In the present study we used a mathematical model to analyse the parameters affecting the output of drug treatment interruption and the premises of the resonance hypothesis.

Methods

We used a population dynamic model of HIV infection. Simulations and analytical approximations of deterministic and stochastic versions of the model were studied.

Results and Conclusion

The present study examines the roles of the most important parameters affecting the viral rebound, responsible for drug failure. We related these findings to the resonance hypothesis, and showed that the degree of sustainability of damping oscillations present in the model after the acute phase is strongly linked to their amplitude, which determines the resonance level. Stochastic simulations of the same model even revealed sustained oscillations in virus population for small virus population sizes. Given that pronounced viral load oscillations have not been observed in HIV-1 patients, the link between oscillations and resonance level suggests that treatment failure due to a resonance effect is not plausible. Moreover, the failure threshold is attained before the virus population crosses the set point while growing. As the maximum virus population is reached even after the set point is crossed, the role of resonance effects in the context of treatment interruptions cannot explain drug failure.

A novel pharmacokinetic approach to predict virologic failure in HIV-1-infected paediatric patients

OBJECTIVE

The objective of this study was to develop in children an HIV dynamic model able to predict simultaneously the viral load and CD4 lymphocyte evolutions, and to take into account, through a composite inhibition score, the relative contribution of each drug of the combination efavirenz-didanosine-lamivudine and use this score as a predictor of treatment failure in a multidrug therapy.

DESIGN

Open phase II trial (BURKINAME - ANRS 12103) registered in the ClinicalTrials.gov database (http://clinicaltrials.gov) with the no. NCT00122538.

METHODS

Forty-nine children aged from 2.5 to 15 years were administered once-daily dose of lamivudine, didanosine and efavirenz. The three drugs effect was then characterized by a composite inhibition score combining the effect of each drug, according to their site and mechanism of action and their relative contribution.

RESULTS

Efavirenz was the most potent antiretroviral and was responsible for 65% of the total effect, and then didanosine for 23% and lamivudine was the less potent with 12% of the total observed effect. An EC90 for efavirenz was determined (3.3 mg/l). AUC90 was estimated for lamivudine and didanosine: 8.4 and 1.5 mg h/l, respectively. The composite inhibition score was the best predictor of virologic failure compared with the concentrations of each drug taken independently [hazard ratio (HR) 0.6 per 10% increase, 95% confidence interval (CI) 0.41-0.88].

CONCLUSION

The relative contributions of three combined drugs were assessed on plasma viral load and CD4 lymphocyte count kinetics in HIV-1-infected children. Pharmacokinetics targets have been suggested for lamivudine and didanosine. A composite inhibition score has been determined to be a high predictor of treatment failure in a multidrug therapy.

Treatment simplification in HIV-infected adults as a strategy to prevent toxicity, improve adherence, quality of life and decrease healthcare costs

Since the advent of highly active antiretroviral therapy (HAART), the treatment of human immunodeficiency virus (HIV) infection has become more potent and better tolerated. While the current treatment regimens still have limitations, they are more effective, more convenient, and less toxic than regimens used in the early HAART era, and new agents, formulations and strategies continue to be developed. Simplification of therapy is an option for many patients currently being treated with antiretroviral therapy (ART). The main goals are to reduce pill burden, improve quality of life and enhance medication adherence, while minimizing short- and long-term toxicities, reducing the risk of virologic failure and maximizing cost-effectiveness. ART simplification strategies that are currently used or are under study include the use of once-daily regimens, less toxic drugs, fixed-dose coformulations and induction-maintenance approaches. Improved adherence and persistence have been observed with the adoption of some of these strategies. The role of regimen simplification has implications not only for individual patients, but also for health care policy. With increased interest in ART regimen simplification, it is critical to study not only implications for individual tolerability, toxicity, adherence, persistence and virologic efficacy, but also cost, scalability, and potential for dissemination and implementation, such that limited human and financial resources are optimally allocated for maximal efficiency, coverage and sustainability of global HIV/AIDS treatment.

Changes in lipids and lipoprotein particle concentrations after interruption of antiretroviral therapy

BACKGROUND

The effect of interruption of antiretroviral therapy (ART) on lipoprotein particle subclasses has not been studied. We examined short-term changes in lipids and lipoprotein particles among 332 HIV-infected individuals randomized to interrupt or continue ART in the "Strategies for Management of Antiretroviral Therapy" trial.

METHODS

Lipids and lipoprotein particles measured by nuclear magnetic resonance spectroscopy were compared between randomized groups at month 1; associations with inflammatory and coagulation markers (high sensitivity C-reactive protein; interleukin 6; amyloid A; amyloid P; D-dimer; prothrombin fragment 1 + 2) were assessed.

RESULTS

Compared with continuation of ART, treatment interruption resulted in substantial declines in total, low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol, and triglyceride, at month 1 but had little net effect on total/HDL cholesterol ratio [baseline-adjusted mean difference [95% confidence interval (CI)] interruption versus continuation arms: -0.10 (-0.59 to 0.38); P = 0.67]. ART interruption resulted in declines in total, large, and medium very low density lipoprotein (VLDL) particle concentrations (VLDL-p) and total and medium HDL-p. However, there was no change in small HDL-p [baseline-adjusted percentage difference between arms: -4.6% (-13.1%, +5.1% ); P = 0.35], small LDL-p [-5.0% (-16.9%, +8.6%); P = 0.45], or other LDL-p subclasses. Changes in lipid parameters on ART interruption did not differ according to baseline ART class (protease inhibitor versus non-nucleoside reverse transcriptase inhibitor) but were negatively associated both with changes in HIV viral load and with changes in inflammatory and coagulation markers, particularly D-dimer.

CONCLUSIONS

These results suggest that ART interruption does not favorably influence overall lipid profile: there was little net effect on total/HDL cholesterol ratio, and no change in small LDL-p or small HDL-p, the lipoprotein particle subclasses most consistently linked to coronary risk. Short-term declines in lipid parameters after ART interruption were not associated with class of ART and may be linked to increases in viral replication, inflammation and coagulation.

Is the recommended once-daily dose of lamivudine optimal in West African HIV-infected children?

We aimed in this study to describe lamivudine concentration-time courses in treatment-naïve children after once-daily administration, to study the effects of body weight and age on lamivudine pharmacokinetics, and to simulate an optimized administration scheme. For this purpose, lamivudine concentrations were measured in 49 children after at least 2 weeks of didanosine-lamivudine-efavirenz treatment. A total of 148 plasma lamivudine concentrations were measured, and a population pharmacokinetic model was developed with NONMEM. The influence of individual characteristics was tested using a likelihood ratio test. Children were divided into two groups, according to their pharmacokinetic parameters, thanks to tree regression analysis. For each patient, the area under the curve was derived from estimated individual pharmacokinetic parameters. Different once-daily doses were simulated in each group, to obtain the same exposure in children as the mean effective exposure in adults (8.9 mg/liter.h). A two-compartment model in which the slope of distribution is assumed to be equal to the absorption rate constant adequately described the data. Parameter estimates were standardized for a mean standard body weight using an allometric model. Children were then divided into 2 groups according to body weight: CL/F was significantly higher in children weighing less than 17 kg (1.12 liters/h/kg) than in children over 17 kg (0.95 liters/h/kg; P=0.01). The target mean AUC of 8.9 mg/liters.h was obtained with a 10-mg/kg once-daily lamivudine (3TC) dose for children below 17 kg; the recommended dose of 8 mg/kg seems to be sufficient in children weighing more than 17 kg. These assumptions should be prospectively confirmed.

A randomized, controlled, trial of short cycle intermittent compared to continuous antiretroviral therapy for the treatment of HIV infection in Uganda

BACKGROUND

Short cycle treatment interruption could reduce toxicity and drug costs and contribute to further expansion of antiretroviral therapy (ART) programs.

METHODS

A 72 week, non-inferiority trial enrolled one hundred forty six HIV positive persons receiving ART (CD4+ cell count > or =125 cells/mm(3) and HIV RNA plasma levels <50 copies/ml) in one of three arms: continuous, 7 days on/7 days off and 5 days on/2 days off treatment. Primary endpoint was ART treatment failure determined by plasma HIV RNA level, CD4+ cell count decrease, death attributed to study participation, or opportunistic infection.

RESULTS

Following enrollment of 32 participants, the 7 days on/7 days off arm was closed because of a failure rate of 31%. Six of 52 (11.5%) participants in the 5 days on/2 days off arm failed. Five had virologic failure and one participant had immunologic failure. Eleven of 51 (21.6%) participants in the continuous treatment arm failed. Nine had virologic failure with 1 death (lactic acidosis) and 1 clinical failure (extra-pulmonary TB). The upper 97.5% confidence boundary for the difference between the percent of non-failures in the 5 days on/2 days off arm (88.5% non-failure) compared to continuous treatment (78.4% non failure) was 4.8% which is well within the preset non-inferiority margin of 15%. No significant difference was found in time to failure in the 2 study arms (p = 0.39).

CONCLUSIONS

Short cycle 5 days on/2 days off intermittent ART was at least as effective as continuous therapy.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00339456.

Didanosine population pharmacokinetics in West African human immunodeficiency virus-infected children administered once-daily tablets in relation to efficacy after one year of treatment

Our objective was to study didanosine pharmacokinetics in children after the administration of tablets, the only formulation available in Burkina Faso for which data are missing, and to establish relationships between doses, plasma drug concentrations, and treatment effects (efficacy/toxicity). Didanosine concentrations were measured for 40 children after 2 weeks and for 9 children after 2 to 5 months of treatment with a didanosine-lamivudine-efavirenz combination. A population pharmacokinetic model was developed with NONMEM. The link between the maximal concentration of the drug in plasma (Cmax), the area under the concentration-time curve (AUC), and the decrease in human immunodeficiency virus (HIV) type 1 RNA levels after 12 months of treatment was evaluated. The threshold AUC that improved efficacy was determined by the use of a Wilcoxon test for HIV RNA, and an optimized dosing schedule was simulated. Didanosine pharmacokinetics was best described by a one-compartment model with first-order absorption and elimination. The apparent clearance and volume of distribution were higher for tablets, probably due to a lower bioavailability with tablets than with pediatric powder. The decrease in the viral load after 12 months of treatment was significantly correlated with the didanosine AUC and Cmax (P < or = 0.02) during the first weeks of treatment. An AUC of >0.60 mg/liter x h was significantly linked to a greater decrease in the viral load (a decrease of 3 log10 versus 2.4 log10 copies/ml; P = 0.03) than that with a lower AUC. A didanosine dose of 360 mg/m2 administered as tablets should be a more appropriate dose than 240 mg/m2 to improve efficacy for these children. However, data on adverse events with this dosage are missing.

Evaluation of the pathogenesis of decreasing CD4(+) T cell counts in human immunodeficiency virus type 1-infected patients receiving successfully suppressive antiretroviral therapy

Most human immunodeficiency virus (HIV)-infected individuals experience increases in peripheral CD4(+) T cell counts with suppressive antiretroviral therapy (ART) that achieves plasma HIV RNA levels that are less than the limit of detection. However, some individuals experience decreasing CD4(+) T cell counts despite suppression of plasma viremia. We evaluated 4 patients with a history of CD4(+) T cell decline despite successfully suppressive ART, from a median of 719 cells/mm(3) (range, 360-1141 cells/mm(3)) to 227 cells/mm(3) (range, 174-311 cells/mm(3)) over a period of 18-24 months; 3 of the patients were receiving tenofovir and didanosine, which may have contributed to this decrease. There was no evidence of HIV replication, nor of antiretroviral drug resistance in the blood or lymphoid tissue, or increased proliferation or decreased thymic production of naive CD4(+) T cells. All 4 patients had significant fibrosis of the T cell zone of lymphoid tissue, which appeared to be an important factor in the failure to reconstitute T cells.

Is the recommended dose of efavirenz optimal in young West African human immunodeficiency virus-infected children?

We aimed in this study to describe efavirenz concentration-time courses in treatment-naïve children after once-daily administration to study the effects of age and body weight on efavirenz pharmacokinetics and to test relationships between doses, plasma concentrations, and efficacy. For this purpose, efavirenz concentrations in 48 children were measured after 2 weeks of didanosine-lamivudine-efavirenz treatment, and samples were available for 9/48 children between months 2 and 5 of treatment. Efavirenz concentrations in 200 plasma specimens were measured using a validated high-performance liquid chromatography method. A population pharmacokinetic model was developed with NONMEM. The influence of individual characteristics was tested using a likelihood ratio test. The estimated minimal and maximal concentrations of efavirenz in plasma (Cmin and Cmax, respectively) and the area under the concentration-time curve (AUC) were correlated to the decrease in human immunodeficiency virus type 1 RNA levels after 3 months of treatment. The threshold Cmin (and AUC) that improved efficacy was determined. The target minimal concentration of 4 mg/liter was considered for toxicity. An optimized dosing schedule that would place the highest percentage of children in the interval of effective and nontoxic concentrations was simulated. The pharmacokinetics of efavirenz was best described by a one-compartment model with first-order absorption and elimination. The mean apparent clearance and volume of distribution for efavirenz were 0.211 liter/h/kg and 4.48 liters/kg, respectively. Clearance decreased significantly with age. When the recommended doses were given to 46 of the 48 children, 19% (44% of children weighing less than 15 kg) had C(min)s below 1 mg/liter. A significantly higher percentage of children with C(min)s of >1.1 mg/liter or AUCs of >51 mg/liter x h than of children with lower values had viral load decreases greater than 2 log10 copies/ml after 3 months of treatment. Therefore, to optimize the percentage of children with C(min)s between 1.1 and 4 mg/liter, children should receive the following once-daily efavirenz doses: 25 mg/kg of body weight from 2 to 6 years, 15 mg/kg from 6 to 10 years, and 10 mg/kg from 10 to 15 years. These assumptions should be prospectively confirmed.

Short-cycle therapy in adolescents after continuous therapy with established viral suppression: the impact on viral load suppression

This was a proof-of-principle study to evaluate the impact of short cycle therapy (SCT; 4 days on/3 days off) in adolescents and young adults with good viral suppression on a protease inhibitor-based antiretroviral regimen. Subjects were recruited by the Adolescent Trials Network for HIV/AIDS Interventions and the Pediatric AIDS Clinical Trials Group. Subjects were infected either through perinatal/early childhood transmission or later via risk behaviors. All subjects were required to have at least 6 months of documented viral suppression below 400 copies/ml plus a preentry value below 200 copies/ml and an entry CD4+ T cell count above 350 cells/mm3. Of the 32 subjects enrolled, 12 (37.5%) had confirmed viral load rebound >400 copies, with 18 subjects (56%) coming off for any reason. The majority of subjects resuppressed when placed back onto continuous therapy using the same agents. Although no difference was found in virologic rebound rates between the early and later transmission groups, those infected early in life had higher rates of coming off SCT for any reason. There was no impact of SCT on the CD4+ T cell counts in those who remained on study or those who came off SCT for any reason. Subjects demonstrated good adherence to the SCT regimen. This study suggests that further evaluation of SCT may be warranted in some groups of adolescents and young adults infected with HIV.

Simplification Strategies to Reduce Antiretroviral drug Exposure: Progress and Prospects

Current US guidelines for initial therapy of HIV type-1 (HIV-1) infection recommend daily, lifelong treatment with a combination of three antiretroviral drugs consisting of two nucleoside analogue reverse transcriptase inhibitors and a non-nucleoside reverse transcriptase inhibitor or a protease inhibitor. Although this approach has been successful in reducing morbidity and mortality from HIV-1 infection, concerns remain about adverse events from chronic drug exposure, the requirement for daily medication adherence, the risk of HIV-1 drug resistance and high treatment costs. The availability of antiretrovirals that are coformulated and dosed once daily have reduced pill burden and have simplified dosing schedules, but have not lowered drug exposure or cost. These limitations have stimulated research into drug-sparing strategies including intermittent therapy and simplified maintenance regimens. Randomized clinical trials have shown greater mortality with intermittent therapy compared with continuous therapy leading to rejection of this strategy. Pilot studies of simplified maintenance therapy with a ritonavir-boosted protease inhibitor alone have shown more promise, although concerns remain. This article reviews progress in the simplification of antiretroviral therapy, recent clinical trial results and prospects for the future.

Detection of nonnucleoside reverse-transcriptase inhibitor-resistant HIV-1 after discontinuation of virologically suppressive antiretroviral therapy

Using standard and ultrasensitive techniques, we detected nonnucleoside reverse-transcriptase inhibitor-associated resistance mutations in 11 (20%) of 54 subjects who discontinued virologically suppressive nonnucleoside reverse-transcriptase inhibitor-containing antiretroviral therapy. Resistance was detected in 45% and 14% of subjects with a baseline human immunodeficiency virus type 1 RNA level of 51-400 copies/mL and <or=50 copies/mL, respectively. Mutations remained detectable for at least 48 weeks in some subjects.

[Longitudinal study on adherence, treatment satisfaction, and effectiveness of once-daily versus twice-daily antiretroviral therapy in a Spanish cohort of HIV-infected patients (CUVA study)]

INTRODUCTION

Adherence is essential for successful antiretroviral therapy (ART), but complex dosing schedules compromise the adherence to and efficacy of this treatment. Once-daily (QD) ART simplifies treatment by lowering the dosing frequency and pill burden. The aim of this study, performed when QD regimens were still limited, was to determine the degree of adherence and patient satisfaction of QD dosing versus twice-daily dosing (BID) of ART.

METHODS

Non-interventional, multicenter, longitudinal study, including initial (I), simplification (S), and rescue (R) therapies. Medical visits were performed at baseline, and at 3 and 6 months. A validated, structured questionnaire was used to assess adherence, and a visual analogical scale applied by independent observers was used to assess satisfaction.

RESULTS

From May to December 2002, 978 patients were recruited. Average pill burden was 5 in QD vs. 6.1 in BID regimens. Undetectable viral load was achieved at 6 months in 83.7% (I), 87.5% (S), and 57.4% (R) of patients, with no significant differences between QD and BID. Adherence and satisfaction with ART were both significantly better in QD vs. BID regimens: 61.4% vs. 53.2% (P < .05) and 54.4% vs. 41.2% (P < .05), respectively. Multivariate analysis revealed the following variables to account for 1) Adherence to ART (OR; 95% CI): treatment satisfaction (1.53, 1.30-1.80), family support (1.25, 0.98-1.61), years of HIV infection (0.97, 0.94-1.003) and intravenous drug use (0.83, 0.70-0.99); 2) Satisfaction with ART: simplification group (1.70, 1.22-2.34), QD therapy (1.33, 1.13-1.56), years of HIV infection (0.95, 0.93-0.98), and CDC stage C (0.85, 0.73-1.01); and 3) Undetectable viral load: naive group (5.08, 3.14-8.22) and adherence (1.57, 1.13-2.17).

CONCLUSION

QD antiretroviral schedules appear to be as effective as BID regimens, with better adherence and treatment satisfaction. This may positively affect treatment efficacy at long-term.

Not all missed doses are the same: sustained NNRTI treatment interruptions predict HIV rebound at low-to-moderate adherence levels

BACKGROUND

While the relationship between average adherence to HIV potent antiretroviral therapy is well defined, the relationship between patterns of adherence within adherence strata has not been investigated. We examined medication event monitoring system (MEMS) defined adherence patterns and their relation to subsequent virologic rebound.

METHODS AND RESULTS

We selected subjects with at least 3-months of previous virologic suppression on a non-nucleoside reverse transcriptase inhibitor (NNRTI)-based regimen from two prospective cohorts in France and North America. We assessed the risk of virologic rebound, defined as HIV RNA of >400 copies/mL according to several MEMS adherence measurements. Seventy two subjects were studied, five of them experienced virologic rebound. Subjects with and without virologic rebound had similar baseline characteristics including treatment durations, regimen (efavirenz vs nevirapine), and dosing schedule. Each 10% increase in average adherence decreased the risk of virologic rebound (OR = 0.56; 95% confidence interval (CI) [0.37, 0.81], P<0.002). Each additional consecutive day off therapy for the longest treatment interruption (OR = 1.34; 95%CI [1.15, 1.68], P<0.0001) and each additional treatment interruption for more than 2 days (OR = 1.38; 95%CI [1.13, 1.77], P<0.002) increased the risk of virologic rebound. In those with low-to-moderate adherence (i.e. <80%), treatment interruption duration (16.2 days versus 6.1 days in the control group, P<0.02), but not average adherence (53.1% vs 55.9%, respectively, P = 0.65) was significantly associated with virologic rebound.

CONCLUSIONS

Sustained treatment interruption may pose a greater risk of virologic rebound on NNRTI therapy than the same number of interspersed missed doses at low-to-moderate adherence.

Metabolic and immune activation effects of treatment interruption in chronic HIV-1 infection: implications for cardiovascular risk

Background

Concern about costs and antiretroviral therapy (ART)-associated toxicities led to the consideration of CD4 driven strategies for the management of HIV. That approach was evaluated in the SMART trial that reported an unexpected increase of cardiovascular events after treatment interruption (TI). Our goal was to evaluate fasting metabolic changes associated with interruption of antiretroviral therapy and relate them to changes of immune activation markers and cardiovascular risk.

Methodology

ACTG 5102 enrolled 47 HIV-1-infected subjects on stable ART, with <200 HIV RNA copies/mL and CD4 cell count ≥500 cells/µL. Subjects were randomly assigned to continue ART for 18 weeks with or without 3 cycles of interleukin-2 (IL-2) (cycle = 4.5 million IU sc BID x 5 days every 8 weeks). After 18 weeks ART was discontinued in all subjects until the CD4 cell count dropped below 350 cells/µL. Glucose and lipid parameters were evaluated every 8 weeks initially and at weeks 2, 4, 8 and every 8 weeks after TI. Immune activation was evaluated by flow-cytometry and soluble TNFR2 levels.

Principal Findings

By week 8 of TI, levels of total cholesterol (TC) (median (Q1, Q3) (−0.73 (−1.19, −0.18) mmol/L, p<0.0001), LDL, HDL cholesterol (−0.36(−0.73,−0.03)mmol/L, p = 0.0007 and −0.05(−0.26,0.03), p = 0.0033, respectively) and triglycerides decreased (−0.40 (−0.84, 0.07) mmol/L, p = 0.005). However the TC/HDL ratio remained unchanged (−0.09 (−1.2, 0.5), p = 0.2). Glucose and insulin levels did not change (p = 0.6 and 0.8, respectively). After TI there was marked increase in immune activation (CD8+/HLA-DR+/CD38+ cells, 34% (13, 43), p<0.0001) and soluble TNFR2 (1089 ng/L (−189, 1655), p = 0.0008) coinciding with the rebound of HIV viremia.

Conclusions

Our data suggests that interrupting antiretroviral therapy does not reduce cardiovascular disease (CVD) risk, as the improvements in lipid parameters are modest and overshadowed by the decreased HDL levels. Increased immune cell activation and systemic inflammatory responses associated with recrudescent HIV viremia may provide a more cogent explanation for the increased cardiovascular risk associated with treatment interruption and HIV infection.

Trial Registration

ClinicalTrials.gov NCT00015704

Virological outcome after structured interruption of antiretroviral therapy for human immunodeficiency virus infection is associated with the functional profile of virus-specific CD8+ T cells

A clear understanding of the antiviral effects of CD8(+) T cells in the context of chronic human immunodeficiency virus (HIV) infection is critical for the development of prophylactic vaccines and therapeutics designed to support T-cell-mediated immunity. However, defining the potential correlates of effective CD8(+) T-cell immunity has proven difficult; notably, comprehensive analyses have demonstrated that the size and shape of the CD8(+) T-cell response are not necessarily indicative of efficacy determined by measures of plasma viral load. Here, we conducted a detailed quantitative and qualitative analysis of CD8(+) T-cell responses to autologous virus in a cohort of six HIV-infected individuals with a history of structured interruption of antiretroviral therapy (ART) (SIT). The magnitude and breadth of the HIV-specific response did not, by themselves, explain the changes observed in plasma virus levels after the cessation of ART. Furthermore, mutational escape from targeted epitopes could not account for the differential virological outcomes in this cohort. However, the functionality of HIV-specific CD8(+) T-cell populations upon antigen encounter, determined by the simultaneous and independent measurement of five CD8(+) T-cell functions (degranulation and gamma interferon, macrophage inflammatory protein 1beta, tumor necrosis factor alpha, and interleukin-2 levels) reflected the emergent level of plasma virus, with multiple functions being elicited in those individuals with lower levels of viremia after SIT. These data show that the quality of the HIV-specific CD8(+) T-cell response, rather than the quantity, is associated with the dynamics of viral replication in the absence of ART and suggest that the effects of SIT can be assessed by measuring the functional profile of HIV-specific CD8(+) T cells.

Effect of twice-daily nevirapine on adherence in HIV-1-infected patients: a randomized controlled study

OBJECTIVE

For optimal adherence, once-daily dosing is best. Whether this applies to antiretroviral therapy is unknown. We thus aimed to determine the effect of once-daily dosing on adherence to nevirapine.

DESIGN

A three-phase (3-month observational, 4-month randomized, 5-month interventional) open-label, clinical trial at four French academic medical centres during 2005-2006 among 62 chronically HIV-1-infected subjects with long-lasting viral suppression under a twice-a-day nevirapine-based antiretroviral combination.

METHODS

Adherence was measured using electronic monitoring devices and validated by sequential plasma drug levels. Participants were randomly assigned to switch to nevirapine 400 mg once-daily (n = 31) or continue nevirapine 200 mg twice-a-day (n = 31). After the randomized phase, participants had an opportunity to choose their antiretroviral dosage. Primary outcome was the mean percentage of adherence.

RESULTS

Fifty-two patients qualified for electronic data analysis. During the randomized phase, the mean adherence rate was non-significantly superior by 0.5% in once-daily versus twice-a-day dosing (P = 0.68), adjusting for previous twice-a-day adherence rate (P < 0.0001). Once-daily group increased days without dose [odds ratio (OR) 1.7; 95% confidence interval (CI) 1.0, 2.8; P = 0.04], adjusting for previous drug interruptions (P < 0.0001). In the longitudinal analysis, once-daily dosing was significantly associated with at least two consecutive days without dose (OR 4.4; 95% CI 1.9, 10.3; P < 0.001).

CONCLUSION

Changing from twice to once-daily nevirapine does not improve adherence. Supporting continuous adherence to antiretroviral therapy in the 'once-a-day era' remains a challenge, even if more potent regimens can achieve viral suppression at lower adherence levels.

Didanosine enteric-coated capsule: current role in patients with HIV-1 infection

Didanosine, which is a synthetic nucleoside analogue intracellularly phosphorylated to the active metabolite, inhibits the activity of HIV-1 reverse transcriptase by competing with the natural substrate. Currently, didanosine is mainly provided as an enteric-coated capsule. In vitro, the molecule is active against laboratory strains and clinical isolates of HIV-1 in resting and activated T cells and monocyte/macrophages. Didanosine may select for resistance mutations that may render the drug inactive against the virus; L74V and K65R remain as the main didanosine-related mutations. In vitro, phenotypic susceptibility to didanosine was decreased beyond a defined fold change clinical cut-off (1.7), and it is considered that genotypic resistance exists when five thymidine-associated mutations or four plus M184V are present. In vivo, clinical studies have shown that didanosine retains significant antiviral activity in patients who have up to five nucleoside analogue mutations at baseline. Didanosine is useful in patients with no previous therapy, as well as in experienced patients in whom one or more antiretroviral regimens has failed.Enteric-coated didanosine is taken once daily, its co-administration with food has been recently evaluated and a reduction of the efficacy of the antiretroviral treatment was not observed. Administered with lamivudine (or emtricitabine), it can be considered a good alternative for use in the nucleoside analogue backbone included in combination therapies for antiretroviral-naive patients. Didanosine could be used in initial treatments for patients intolerant of zidovudine, abacavir or tenofovir. It can be included in once-daily combination regimens, which are more convenient and patient friendly.Prospective, observational and open-label studies, as well as clinical trials (with durations between 24 and 96 weeks), have demonstrated the safety and efficacy of didanosine plus lamivudine (or emtricitabine) plus efavirenz (or nevirapine) in previously untreated HIV-1-infected patients. The administration of didanosine to treatment-experienced patients has been evaluated in two different contexts: patients in whom previous therapies have failed (rescue therapy) and those with controlled viraemia who are switched to a didanosine-containing regimen for simplification.Adverse events associated with the administration of didanosine have been well known since the initial clinical trials with the drug. Gastrointestinal intolerance, peripheral neuropathy and hyperamylasaemia/pancreatitis were the most frequently reported. In the highly active antiretroviral therapy (HAART) era, the rate of adverse events has decreased. The tolerability of didanosine has been clearly improved with the development of the enteric-coated capsule. Severe manifestations of mitochondrial toxicity, including lactic acidosis and abnormal fat distribution, are rare complications, and occur most frequently when didanosine is used in combination with stavudine.

The role of compartment penetration in PI-monotherapy: the Atazanavir-Ritonavir Monomaintenance (ATARITMO) Trial

OBJECTIVES

To limit exposure to anti-HIV drugs and minimize risk of long-term side effects, studies have looked at the possibility of simplified maintenance strategies. Ritonavir-boosted protease-inhibitor (PI)-monotherapies are an attractive alternative, but limited compartmental penetration of PI remains a concern.

DESIGN

Non-comparative 24-week pilot study.

METHOD

Ritonavir-boosted atazanavir (ATV/r) monotherapy administered to fully suppressed patients (>3 month HIV RNA < 50 copies/ml). Plasma was obtained every 4 weeks and cerebrospinal fluid (CSF) and semen at W24.

RESULTS

Two patients (7%) failed ATV/r monotherapy. One patient was subsequently identified as a protocol violator since he had a previous history of treatment failure under indinavir. The second patient deliberately decided to stop treatment after W20. Excluding failing patients, individual measurements of HIV RNA in patients having occasional viral 'blips' was found in five patients. At W24, 3/20 patients had elevated viral loads in CSF (HIV RNA > 100 copies/ml), and 2/15 in semen, despite viral suppression in plasma (< 50 copies/ml). Samples with elevated HIV RNA (> 500 copies/ml) in CSF were all wild type. The mean ATV drug concentration ratio (CSF/blood, n = 22) was 0.9%. Indicators of altered immune activation (CD8CD38 C-reactive protein) remained unchanged.

CONCLUSION

This study supports previous results indicating the potential use of PI-based mono-maintenance therapies. However, our results in CSF cautions against the uncontrolled use of PI-based monotherapies.

The Role of Adherence to Antiretroviral Therapy in the Management of HIV Infection

Despite multiple studies demonstrating the relation between the success of highly active antiretroviral therapy (HAART) and adherence, inadequate adherence continues to be one of the most frequent reasons for poor treatment outcomes and/or lack of sustained treatment benefits. Interventions targeting patient-related social and psychologic barriers to adherence and issues related to mental health and substance abuse and access to health care may ameliorate their negative impact on adherence. Specific drug-related factors that influence adherence such as pill burden, dosing frequency, food requirements, and acute tolerability and safety concerns, however, are further issues that must be considered to optimize adherence. Fortunately, the availability of once-daily and coformulated agents with simple dosing requirements may help to improve adherence, and thereby make the difference between success and failure of HAART for some patients. A better understanding of adherence and its determinants and how to define specific goals in a given clinical setting are keys for clinicians to become more effective partners with patients in the achievement and maintenance of long-term virologic suppression and, more importantly, long-term health.

A randomised control trial of structured interrupted generic antiretroviral therapy versus continuous therapy in HIV-infected individuals in Southern India

This randomised control trial, conducted in Chennai, India, compared structured interrupted therapy (SIT) and continuous therapy (CT) in relation to immunologic and virologic outcomes, adverse events (AEs) and cost of therapy. ART-naïve adult HIV1-infected participants with CD4 counts 50-350 cells/mm(3), and plasma viral load (PVL)>5000 copies/mL were enrolled and placed on Indian-manufactured generic ART: zidovudine(AZT)/stavudine(d4T)+lamivudine(3TC)+efavirenz(EFV). After at least six months of continuous therapy, subjects were randomised to SIT (one-week-on/one-week-off cycles) or CT. The primary end-point was the proportion of subjects maintaining CD4>200 cells/mm(3) at six and 12 months after randomisation. Secondary end-points were effective viral suppression (PVL<400 copies/mL), AEs and cost. All analyses used intention-to-treat methodology. Of 40 participants (69% male; mean age 36+/-7; median baseline CD4 and PVL: 162 cell/mm(3)and 259,000 copies/mL), 17 were randomised to SIT and 18 to CT. At randomisation, median CD4s for SIT and CT were 378 cells/mm(3) and 357 cells/mm(3), respectively. All participants had PVL<400 copies/mL at time of randomisation. Median CD4 six months after randomisation was 498 cells/mm(3) and 417 cells/mm(3) for SIT and CT respectively. All participants had CD4>200 cells/mm(3). One participant on CT and two on SIT had sustained PVL>400 copies/mL. There were no serious AEs or deaths. Structured interrupted therapy cost was half of CT. Structured interrupted therapy was effective at maintaining CD4 above 200 cells/mm(3). Adverse events were comparable in both groups, with 50% reduction in cost for SIT. Further research on such strategies may benefit resource-constrained settings.

Adherence to generic reverse transcriptase inhibitor-based antiretroviral medication at a Tertiary Center in North India

At least 95% adherence to medications is required for sustained response to antiretroviral therapy (ART). In resource constraint restrained settings it is not possible to use electronic methods to determine adherence. We determined adherence during the previous 4 weeks by the recall method in 200 patients (138 males) receiving generic triple drug reverse transcriptase inhibitor-based antiretroviral medications. They were administered a uniform questionnaire to determine the number of time they forgot or were unable to take their medications and the reasons thereof. One hundred and fifty received two and 50 took three pills daily. One hundred and forty-seven did not miss any dose. Fifty-three (26.5%) missed at least one dose during the preceding 4 weeks. Thirty-one took treatment on and off. Seven missed a dose in the preceding 3 days, nine more between the last 3 and 7 days, and six from 1 to 4 weeks. The major reasons for non-adherence were financial constraints, forgetting to take the medication, drug toxicity, lack of access to the drug, fear of getting immune to the benefit of the drug, and to avoid adverse effects. Non-adherence in 26.5% individuals could be an additional factor that can increase the risk of drug resistance.

Structured treatment interruptions with tenofovir monotherapy for simian immunodeficiency virus-infected newborn macaques

We demonstrated previously that prolonged tenofovir treatment of infant macaques, starting early during infection with virulent simian immunodeficiency virus (SIVmac251), can lead to persistently low or undetectable viremia even after the emergence of mutants with reduced in vitro susceptibility to tenofovir as a result of a K65R mutation in reverse transcriptase; this control of viremia was demonstrated to be mediated by the generation of effective antiviral immune responses. To determine whether structured treatment interruptions (STI) can induce similar immunologic control of viremia, eight newborn macaques were infected with highly virulent SIVmac251 and started on a tenofovir STI regimen 5 days later. Treatment was withdrawn permanently at 33 weeks of age. All animals receiving STI fared much better than 22 untreated SIVmac251-infected infant macaques. However, there was a high variability among animals in the viral RNA set point after complete drug withdrawal, and none of the animals was able to achieve long-term immunologic suppression of viremia to persistently low levels. Early immunologic and viral markers in blood (including the detection of the K65R mutation) were not predictive of the viral RNA set point after drug withdrawal. These results, which reflect the complex interactions between drug resistance mutations, viral virulence, and drug- and immune-mediated inhibition of virus replication, highlight the difficulties associated with trying to develop STI regimens with predictable efficacy for clinical practice.

Predictive factors of treatment interruption duration in a cohort of HIV-1 infected patients with CD4 count greater than 350 cells per mm3

OBJECTIVE

To determine predictive factors of treatment interruption (TI) duration within a cohort of HIV-1 infected patients having stopped their treatment with CD4 above 350 cells per mm(3).

DESIGN

Data were collected from computerized medical records. Patients were selected if they were HIV-1 positive, 18 years of age or older, and had stopped their treatment between January 1st, 1999 and July 1st, 2003, with CD4 count above 350 cells per mm(3). The study period was censored on October 1st, 2003. Patients were assessed every 3 months from inclusion to censure. A survival analysis using the Cox proportional hazard model was performed.

RESULTS

One hundred eighty-five patients were included. The median duration of TI was 43 weeks. Sixty-three patients remained off-treatment at censure. In the multivariate analysis, TI duration was shorter if CD4 nadir was below 250 cells per mm(3) before TI (relative hazard, 2.10), age superior to 40 (relative hazard, 1.72), viral load higher than 2.3 log.copies per ml (relative hazard, 1.52), and CDC class C (relative hazard, 1.78) at TI. Neither CD4 cell count at TI, numbers of treatments, nor duration of treatment and infection before TI were independent predictive factors of early treatment resumption (TR).

CONCLUSION

Some clinical and biological data may be used as predictive factors of early TR. Our results can have implications on future therapeutic strategies, in which the goal of therapy is to maintain CD4 cell count above a predetermined threshold using cycles of therapy followed by prolonged interruption according to CD4 count.

Role of parametric resonance in virological failure during HIV treatment interruption therapy

We present a novel hypothesis that could explain virological failure to structured treatment interruptions (STI). We analysed a classic mathematical model of HIV within-host viral dynamics and found that non-linear parametric resonance occurs when STI are added to the model; resonance is observed as virological failure. We simulated clinical trial data and calculated patient-specific resonant spectra. We gained two important insights. First, within an STI trial, patients who begin with similar viral loads can be expected to show very different virological responses as a result of resonance. Second, and more importantly, virological failure is not simply due to STI or patients' characteristics; instead it is the result of complex interaction between STI and the patient's viral dynamics. Hence, our analyses show that no universal regimen with periodic interruptions will be effective for all patients.

Pharmacogenetics of plasma efavirenz exposure after treatment discontinuation: an Adult AIDS Clinical Trials Group Study

BACKGROUND

Efavirenz has a long plasma half-life and a low genetic barrier to resistance. Simultaneously stopping treatment with all agents in efavirenz-containing regimens may result in functional efavirenz monotherapy that selects for drug-resistant human immunodeficiency virus type 1. Lower plasma efavirenz clearance is associated with a cytochrome P450 2B6 gene (CYP2B6) polymorphism (516G-->T) that is more frequent among African American individuals than among European American individuals.

METHODS

We characterized relationships between this polymorphism and predicted plasma efavirenz concentration-time profiles after discontinuation of therapy with use of data obtained from subjects receiving therapy. Pharmacokinetic parameters were estimated using population-based methods. Concentrations after discontinuation of therapy were predicted from subject-specific estimates. RESULTS. Median estimated efavirenz half-lives were 23, 27, and 48 h for patients with CYP2B6 position 516 GG (78 patients), GT (60), and TT (14) genotypes, respectively (P<.001). After therapy was stopped, plasma efavirenz concentrations in patients with GG, GT, and TT genotypes were predicted to exceed 46.7 ng/mL (the estimated protein-adjusted 95% inhibitory concentration for wild-type virus) for a median of 5.8 days (interquartile range [IQR], 4.4-8.3 days), 7.0 days (IQR, 5.0-8.0 days), and 14 days (IQR, 11.1-21.2 days), respectively (P<.001). Plasma efavirenz levels were predicted to exceed 46.7 ng/mL for >21 days in 5% of subjects with GG genotype, 5% of subjects with GT genotype, and 29% of subjects with TT genotype.

CONCLUSIONS

The CYP2B6 position 516 TT genotype or a prolonged measured elimination half-life may predict increased risk of developing drug resistance among patients who discontinue efavirenz-containing regimens. This has implications for strategies to safely discontinue antiretroviral regimens while avoiding the emergence of drug resistance.

Discontinuation of antiretroviral therapy in patients with chronic HIV infection: clinical, virologic, and immunologic consequences

To investigate the clinical, virologic and immunologic consequences of planned treatment interruptions in chronically HIV-infected patients. One hundred forty-one patients with undetectable viral load for at least 6 months and CD4+ T cells count greater than 500 per microliter were recruited. Their antiretroviral therapy was stopped and clinical, analytic, virologic, and immunologic data were recorded at baseline, during discontinuation, and after restarting treatment. Viral load rebound after discontinuation in 137 (97%) patients, and was similar to prehighly active antiretroviral therapy (HAART) levels. A rapid decrease in CD4+ T-cell count (median, 240 cells per microliter), was observed in the first 3 months in all patients, with pronounced differences between them. After a median follow-up of 36 months, 45.5% patients were still without therapy. Factors related to a more severe decline were a prior lower CD4+ T nadir (<200 cells per microliter) before starting HAART, a greater increase (>500 cells per microliter) with it, a higher CD4+ T-cell count before interruption (>800 cells per microliter) and a higher viral load rebound after it. The increase in CD4+ T-cell counts after reinitiation was slower than the decline and only 55% of patients have regained the preinterruption levels at 12 months of follow- up. Twelve infectious events were registered. Treatment failure related to drug resistance was observed in two patients. Planned treatment interruptions may be safe in selected patients with previous CD4+ T cell nadir greater than 200 cells per microliter and pre-HAART VL less than 55.000 copies per milliliter, but should be not recommended in patients with the prognostic factors related to a rapid decline described in this study. Furthermore, there is a considerable concern about the development of drug resistance and the possibility of an incomplete immune reconstitution after the treatment interruption in some patients.

Retrospective analysis of suspending HAART in selected patients with controlled HIV replication

We sought to determine the consequences of stopping highly active antiretroviral therapy (HAART) in a group of 41 HIV-infected individuals with undetectable HIV viral loads and CD4+ counts greater than 500 cells per microliter for 6 months or more. Clinical and laboratory parameters were monitored, as was the time to HAART reinitiation. Three months after HAART interruption, the median CD4+ count declined by 162 cells per microliter and HIV viral load increased by 24,000 copies per milliliter. Over the next year, CD4+ counts continued to decrease by an average of 11 cells per microliter per 3-month intervals. In contrast, HIV viral loads remained stable over the same period. Five of 7 patients (71%) with elevated cholesterol levels and 6 of 13 patients (46%) with elevated triglyceride levels had these values normalize after stopping HAART. After a median of 21 months follow-up, 26 of 41 patients (63%) have restarted HAART. Patients with Centers for Disease Control (CDC) HIV/AIDS C classification were more likely to restart HAART than those with A or B classification (p = 0.008). Reasons for HAART restart included clinical events in 8 patients. Fifteen patients restarted HAART for immunologic reasons: CD4+ count less than 300 cells per microliter (n = 7); HIV viral load greater than 55,000 copies per milliliter (n = 3); or both (n = 5). Three patients restarted HAART because of personal preference. Within 4 months, all 26 patients who restarted HAART achieved HIV viral loads less than 50 copies per milliliter. Although patients were able to rapidly achieve nondetectable HIV viral loads after restarting HAART, the inability to foresee clinical events among 8 patients (20%) is disconcerting. We advise caution before HAART interruption, particularly for those patients with a preceding history of significant HIV-related complications.

Structured intermittent therapy with seven-day cycles of HAART for chronic HIV infection: a pilot study in São Paulo, Brazil

In the last 6 years, an impressive impact of the highly active antiretroviral therapy (HAART) on survival and morbidity in HIV-1-infected individuals has been attained. However, their prolonged use may induce metabolic adverse effects such as lipodistrophy, hypertension, diabetes mellitus, osteopenia and hyperlipidemia. Recently, new strategies such as short-cycle structured intermittent therapy (SIT; 7 days without therapy followed by 7 days with HAART) have been suggested. We tested this strategy in seven (four women and three men; mean of age 39 of years) HIV-positive individuals, all of whom had CD4+ T cell counts greater than 500 cells/mm3 and undetectable plasma viral load for at least 2 years. Our results indicated no opportunistic diseases or CD4 cell count decrease over a mean follow-up of 26 months. No plasma viral replication was detected in five of seven cases. There was a decrease in triglyceride levels to normal range (not statistically significant), but no modification of cholesterol levels. Thus, we recommend a larger clinical trial to determine if SIT is cost effective in developing countries.

Interrupting highly active antiretroviral therapy in patients with HIV

Scheduled treatment interruptions are preplanned interruptions of antiretroviral treatment, which may be directed by time (e.g., cycles of 8 weeks on treatment and 8 weeks off treatment); the concentration of CD4+ lymphocytes (the CD4 count); HIV-1 RNA concentration (viral load); or other factors. This review covers the rationale of scheduled treatment interruptions and the different strategies that have been explored. It examines the issue of autovaccination, resistance and other risks and benefits. Scheduled-treatment-interruption studies in three populations are discussed: patients who initiated highly active antiretroviral therapy during acute HIV infection; patients with successfully treated chronic HIV infection; and patients with highly active antiretroviral therapy failure.

Knowledge of structured treatment interruption and adherence to antiretroviral therapy

We conducted a survey of 106 HIV-infected patients on antiretroviral therapy at a community hospital in Lancaster, Pennsylvania, to determine the extent of patient knowledge and attitudes about structured treatment interruption (STI) and whether these were factors in adherence to antiretroviral regimens. Thirty-six percent of patients possessed knowledge of STI as a treatment option and four patients reported that they had stopped taking antiretroviral therapy without specific recommendation from their physician based on information they had heard or read about STI. There was no difference in median adherence based on whether a patient was aware of STI, however, in the group who had heard of STI, attitude that STI is very beneficial was correlated with greater adherence to medication. More than one third of HIV-infected patients on antiretroviral therapy possessed knowledge of STI, and this knowledge affected adherence to antiretroviral regimens. Providers caring for HIV-infected patients should routinely inquire about patient knowledge of STI as another factor in assessing adherence to antiretroviral therapy.

A Prospective, Randomized Trial of Structured Treatment Interruption for Patients with Chronic HIV Type 1 Infection

BACKGROUND

Structured treatment interruption was evaluated in 74 patients who had been pretreated with antiretrovirals, consisting of 2 nucleoside reverse-transcriptase inhibitors (NRTIs) for 1 year followed by 3 years of highly active antiretroviral therapy containing a protease inhibitor.

METHODS

Patients with a CD4 cell count of > or =350 cells/microL and a plasma viral load of <50 copies/mL were randomized to 3 therapy arms: (1) continuous therapy, (2) CD4 cell count-guided theory, and (3) week-on/week-off (WOWO) therapy. The efficacy and safety of structured treatment interruption and antiretroviral use were evaluated in human immunodeficiency type 1 (HIV-1)-infected patients. The study end points were percentage of patients who developed AIDS or who died and a CD4 cell count of > or =350 cells/microL. Intergroup differences were analyzed using analysis of variance and Kruskal-Wallis tests.

RESULTS

Baseline characteristics at the start of the structured treatment interruption were similar. At week 48, no patient had died, and 1 patient in the WOWO group had an AIDS-defining condition. The proportions of patients with a CD4 cell count of > or =350 cells/microL were 100%, 87%, and 96% in treatment arms 1, 2, and 3, respectively. The percentages of weeks of antiretroviral use were 100%, 41.1%, and 69.8% in arms 1, 2, and 3, respectively. The adverse events were not significantly different among arms (P=.27). Thirty-one percent of patients in the WOWO group experienced virological failure.

CONCLUSION

WOWO therapy maintained a CD4 cell count of > or =350 cells/microL in almost all patients but was associated with high virological failures rates (possibly resulting from previous dual-NRTI therapy), indicating that this strategy is less useful. Receipt of CD4 cell count-guided therapy resulted in comparable clinical outcomes to continuous therapy and may save antiretroviral-associated costs, but this needs to be confirmed by a larger trial.

Similar adherence rates favor different virologic outcomes for patients treated with nonnucleoside analogues or protease inhibitors

BACKGROUND

This prospective study verified the effect of adherence on the risk of virologic failure.

METHODS

At enrollment in the study, a total of 543 patients who were following a steady (duration, >or=6 months) and effective (viral load, <50 human immunodeficiency virus [HIV] RNA copies/mL) regimen of highly active antiretroviral therapy (HAART) completed a self-reported questionnaire derived from the Adult AIDS Clinical Trials Group Adherence Follow-up Questionnaire. Patients were followed up for the subsequent 6 months to document virologic failure, which was defined as 2 consecutive viral load measurements of >500 HIV RNA copies/mL.

RESULTS

Only the type of treatment and the adherence rate at baseline were significantly associated with the virologic end point. Among patients who reported an adherence rate of <or=75%, the rate of virologic failure was 17.4%; this rate decreased to 12.2% for patients whose adherence rate was 76%-85%, to 4.3% for patients whose adherence rate was 86%-95%, and to 2.4% for patients whose adherence rate was >95%. When analysis was adjusted according to the type of regimen received, patients who were receiving protease inhibitor (PI)-based HAART and who had an adherence rate of up to 85% had a virologic failure rate of >20%, whereas, only for patients who were receiving nonnucleoside reverse-transcriptase inhibitor (NNRTI)-based HAART and who had an adherence rate of <or=75%, the virologic failure rate was >10%. For the comparison of NNRTI-treated patients and PI-treated patients with an adherence rate of 75%-95%, the odds ratio was 0.157 (95% confidence interval, 0.029-0.852). The number of pills and daily doses received correlated with the reported adherence rate.

CONCLUSIONS

Patients receiving NNRTIs report a higher rate of adherence than do patients receiving PIs. Adherence is significantly influenced by the number of pills and daily doses received. Low adherence is a major determinant of virologic failure; however, different therapies have different cutoff values for adherence that determine a significant increment of risk.