Efficacy and safety of TMC125 (etravirine) in treatment-experienced HIV-1-infected patients in DUET-1: 24-week results from a randomised, double-blind, placebo-controlled trial

Impact of drug resistance-associated amino acid changes in HIV-1 subtype C on susceptibility to newer nonnucleoside reverse transcriptase inhibitors

The objective of this study was to assess the phenotypic susceptibility of HIV-1 subtype C isolates, with nonnucleoside reverse transcriptase inhibitor (NNRTI) resistance-associated amino acid changes, to newer NNRTIs. A panel of 52 site-directed mutants and 38 clinically derived HIV-1 subtype C clones was created, and the isolates were assessed for phenotypic susceptibility to etravirine (ETR), rilpivirine (RPV), efavirenz (EFV), and nevirapine (NVP) in an in vitro single-cycle phenotypic assay. The amino acid substitutions E138Q/R, Y181I/V, and M230L conferred high-level resistance to ETR, while K101P and Y181I/V conferred high-level resistance to RPV. Y181C, a major NNRTI resistance-associated amino acid substitution, caused decreased susceptibility to ETR and, to a lesser extent, RPV when combined with other mutations. These included N348I and T369I, amino acid changes in the connection domain that are not generally assessed during resistance testing. However, the prevalence of these genotypes among subtype C sequences was, in most cases, <1%. The more common EFV/NVP resistance-associated substitutions, such as K103N, V106M, and G190A, had no major impact on ETR or RPV susceptibility. The low-level resistance to RPV and ETR conferred by E138K was not significantly enhanced in the presence of M184V/I, unlike for EFV and NVP. Among patient samples, 97% were resistant to EFV and/or NVP, while only 24% and 16% were resistant to ETR and RPV, respectively. Overall, only a few, relatively rare NNRTI resistance-associated amino acid substitutions caused resistance to ETR and/or RPV in an HIV-1 subtype C background, suggesting that these newer NNRTIs would be effective in NVP/EFV-experienced HIV-1 subtype C-infected patients.

Current perspectives on HIV-1 antiretroviral drug resistance

Current advancements in antiretroviral therapy (ART) have turned HIV-1 infection into a chronic and manageable disease. However, treatment is only effective until HIV-1 develops resistance against the administered drugs. The most recent antiretroviral drugs have become superior at delaying the evolution of acquired drug resistance. In this review, the viral fitness and its correlation to HIV-1 mutation rates and drug resistance are discussed while emphasizing the concept of lethal mutagenesis as an alternative therapy. The development of resistance to the different classes of approved drugs and the importance of monitoring antiretroviral drug resistance are also summarized briefly.

Significant reduction in HIV virologic failure during a 15-year period in a setting with free healthcare access

BACKGROUND

Calendar trends in virologic failure (VF) among human immunodeficiency virus (HIV)-infected patients can help to evaluate the performance of healthcare systems and the need for new antiretroviral therapy (ART). We examined the time trend in the rate of VF beyond 6 months of ART between 1997 and 2011 in France.

METHODS

We included patients from the French Hospital Database on HIV who received at least 6 months of ART. VF was defined as 2 consecutive plasma HIV-RNA values >500 copies/mL or as 1 value >500 copies/mL followed by a treatment switch. We adjusted for patients' characteristics by fitting a multivariable generalized estimating equation logistic regression model with an exchangeable covariance matrix.

RESULTS

A total of 81 738 patients were enrolled, and median follow-up was 112.4 months. Median CD4 count was 333 cells/µL, and 23% of patients had HIV infection classified as Centers for Disease Control and Prevention stage C. Overall, 29.3% of patients received single/dual-drug ART initially, and 45.4% of patients experienced at least 1 episode of VF during follow-up. The percentage of patients with VF fell from 61.5% in 1997-1998 to 9.7% in 2009-2011 (P < .0001). Factors associated with the lower frequency of VF were recent calendar period, a higher contemporary CD4 cell count, and first-line regimens based on nonnucleoside reverse transcriptase inhibitors or integrase inhibitors.

CONCLUSIONS

The proportion of HIV-infected patients experiencing VF during routine care fell markedly between 1997 and 2009-2011, to only 9.7%. This was attributed to the advent of fully active and better-tolerated antiretroviral drugs, and to national guidelines recommending rapid management of VF after mid-2000.

The discovery and development of antiretroviral agents

Since the discovery of HIV as the causative agent of AIDS in 1983/1984, remarkable progress has been made in finding antiretroviral drugs (ARVs) that are effective against it. A major breakthrough occurred in 1996 when it was found that triple drug therapy (HAART) could durably suppress viral replication to minimal levels. It was then widely felt, however, that HAART was too expensive and complex for low- and middle-income countries, and so, with the exception of a few of these countries, such as Brazil, a massive scale-up did not begin until the WHO launched its '3 by 5' initiative and sizeable funding mechanisms, such as the Global Fund to Fight AIDS, TB and Malaria and the US President's Emergency Plan for AIDS Relief (PEPFAR), came into existence. A pivotal enabler of the scale-up was a steady lowering of drug prices through entry of generic antiretrovirals, competition between generic manufacturers and the making of volume commitments. The WHO Prequalification of Medicines Programme and the Expedited Review Provision of the US Food and Drug Administration have been important for the assurance of quality standards. Antiretroviral drug development by research-based pharmaceutical companies continues, with several important innovative products, such as long-acting agents, in the pipeline.

Drug resistance in non-B subtype HIV-1: impact of HIV-1 reverse transcriptase inhibitors

Human immunodeficiency virus (HIV) causes approximately 2.5 million new infections every year, and nearly 1.6 million patients succumb to HIV each year. Several factors, including cross-species transmission and error-prone replication have resulted in extraordinary genetic diversity of HIV groups. One of these groups, known as group M (main) contains nine subtypes (A-D, F-H and J-K) and causes ~95% of all HIV infections. Most reported data on susceptibility and resistance to anti-HIV therapies are from subtype B HIV infections, which are prevalent in developed countries but account for only ~12% of all global HIV infections, whereas non-B subtype HIV infections that account for ~88% of all HIV infections are prevalent primarily in low and middle-income countries. Although the treatments for subtype B infections are generally effective against non-B subtype infections, there are differences in response to therapies. Here, we review how polymorphisms, transmission efficiency of drug-resistant strains, and differences in genetic barrier for drug resistance can differentially alter the response to reverse transcriptase-targeting therapies in various subtypes.

Cost effectiveness of darunavir/ritonavir combination antiretroviral therapy for treatment-naive adults with HIV-1 infection in Canada

OBJECTIVE

The AntiRetroviral Therapy with TMC114 ExaMined In naive Subjects (ARTEMIS) clinical trial examined the efficacy and safety of two ritonavir-boosted protease inhibitors (PI/r), darunavir/r 800/100 mg once daily (QD) and lopinavir/r 800/200 mg daily, both used in combination with tenofovir disoproxil fumarate/emtricitabine. This study aimed to assess the cost effectiveness of the darunavir/r regimen compared with the lopinavir/r regimen in treatment-naive adults with HIV-1 infection in Canada.

METHODS

A Markov model with a 3-month cycle time and six CD4 cell-count-based health states (>500, 351-500, 201-500, 101-200, 51-100, and 0-50 cells/mm(3)) followed a cohort of treatment-naive adults with HIV-1 infection through initial darunavir/r or lopinavir/r combination therapy and a common set of subsequent regimens over the course of their remaining lifetimes. Population characteristics and transition probabilities were estimated from the ARTEMIS clinical trial and other trials. Costs (in 2014 Canadian dollars), utilities, and mortality were estimated from Canadian sources and published literature. Costs and health outcomes were discounted at 5% per year. One-way and probabilistic sensitivity analyses were performed, including a simple indirect comparison of the darunavir/r initial regimen with an atazanavir/r-based regimen.

RESULTS

In the base-case lifetime analysis, individuals receiving initial therapy with the darunavir/r regimen experienced 0.25 more quality-adjusted life-years (QALYs) with lower antiretroviral drug costs (-$14,246) and total costs (-$18,402) than individuals receiving the lopinavir/r regimen, indicating that darunavir/r dominated lopinavir/r. In an indirect comparison with an atazanavir/r-based regimen, the darunavir/r regimen remained the dominant choice, but with lower cost savings (-$2,303) and QALY gains (0.02). Results were robust to a wide range of other changes in input parameter values, population characteristics, and modeling assumptions. The probabilistic sensitivity analysis demonstrated that the darunavir/r regimen was cost effective compared with the lopinavir/r regimen in over 86% of simulations for willingness-to-pay thresholds between $0 and $100,000 per QALY gained.

CONCLUSIONS

Darunavir/r 800/100 mg QD may be a cost-effective PI/r component of initial antiretroviral therapy for treatment-naive adults with HIV-1 infection in Canada.

The emerging profile of cross-resistance among the nonnucleoside HIV-1 reverse transcriptase inhibitors

Nonnucleoside reverse transcriptase inhibitors (NNRTIs) are widely used to treat HIV-1-infected individuals; indeed most first-line antiretroviral therapies typically include one NNRTI in combination with two nucleoside analogs. In 2008, the next-generation NNRTI etravirine was approved for the treatment of HIV-infected antiretroviral therapy-experienced individuals, including those with prior NNRTI exposure. NNRTIs are also increasingly being included in strategies to prevent HIV-1 infection. For example: (1) nevirapine is used to prevent mother-to-child transmission; (2) the ASPIRE (MTN 020) study will test whether a vaginal ring containing dapivirine can prevent HIV-1 infection in women; (3) a microbicide gel formulation containing the urea-PETT derivative MIV-150 is in a phase I study to evaluate safety, pharmacokinetics, pharmacodynamics and acceptability; and (4) a long acting rilpivirine formulation is under-development for pre-exposure prophylaxis. Given their widespread use, particularly in resource-limited settings, as well as their low genetic barriers to resistance, there are concerns about overlapping resistance between the different NNRTIs. Consequently, a better understanding of the resistance and cross-resistance profiles among the NNRTI class is important for predicting response to treatment, and surveillance of transmitted drug-resistance.

Optimizing antiretroviral therapy for women living with HIV

PURPOSE OF REVIEW

This review considers the evidence available to guide clinicians in their choice of optimal antiretroviral therapy (ART) for women with HIV.

RECENT FINDINGS

Cohort and clinical trial data indicate that ART is as efficacious in women as men, although women are more likely to discontinue therapy, which compromises effectiveness. For many drugs, women have higher plasma levels than men, although whether this is secondary to differing metabolism in women or because on average women have a lower body mass than men is not clear. For many drugs, women experience more adverse events secondary to ART. Opinion on the use of efavirenz in pregnancy differs between countries. The average age of women with HIV is increasing. Although virological responses to ART are not affected by age, immunological responses may be poorer. Older women with HIV face issues such as neurocognitive impairment, early menopause, osteoporosis and polypharmacy, which will have the potential to impact on their use of ART.

SUMMARY

When planning ART regimes with women, clinicians need to be mindful of the woman's social situation and stage in the life course, as well as the scientific data on individual drug effectiveness according to sex.

Antiretroviral therapy: treatment-experienced individuals

Antiretroviral therapy (ART)-experienced individuals may choose to modify their regimens because of suboptimal virologic response, poor tolerability, convenience, or to minimize interactions with other medications or food. Constructing a new regimen for any of these reasons requires a thorough review of prior antiretroviral drug use and available drug resistance results. This article summarizes the strategies used in managing the ART-experienced individual who is considering a modification in therapy at the time of suboptimal virologic response or while virologically suppressed on a stable regimen.

French 2013 guidelines for antiretroviral therapy of HIV-1 infection in adults

Introduction

These guidelines are part of the French Experts’ recommendations for the management of people living with HIV/AIDS, which were made public and submitted to the French health authorities in September 2013. The objective was to provide updated recommendations for antiretroviral treatment (ART) of HIV-positive adults. Guidelines included the following topics: when to start, what to start, specific situations for the choice of the first session of antiretroviral therapy, optimization of antiretroviral therapy after virologic suppression, and management of virologic failure.

Methods

Ten members of the French HIV 2013 expert group were responsible for guidelines on ART. They systematically reviewed the most recent literature. The chairman of the subgroup was responsible for drafting the guidelines, which were subsequently discussed within, and finalized by the whole expert group to obtain a consensus. Recommendations were graded for strength and level of evidence using predefined criteria. Economic considerations were part of the decision-making process for selecting preferred first-line options. Potential conflicts of interest were actively managed throughout the whole process.

Results

ART should be initiated in any HIV-positive person, whatever his/her CD4 T-cell count, even when >500/mm³. The level of evidence of the individual benefit of ART in terms of mortality or progression to AIDS increases with decreasing CD4 cell count. Preferred initial regimens include two nucleoside reverse transcriptase inhibitors (tenofovir/emtricitabine or abacavir/lamivudine) plus a non-nucleoside reverse transcriptase inhibitor (efavirenz or rilpivirine), or a ritonavir-boosted protease inhibitor (atazanavir or darunavir). Raltegravir, lopinavir/r, and nevirapine are recommended as alternative third agents, with specific indications and restrictions. Specific situations such as HIV infection in women, primary HIV infection, severe immune suppression with or without identified opportunistic infection, and person who injects drugs are addressed. Options for optimization of ART once virologic suppression is achieved are discussed. Evaluation and management of virologic failure are described, the aim of any intervention in such situation being to reduce plasma viral load to <50 copies/ml.

Conclusion

These guidelines recommend that any HIV-positive individual should be treated with ART. This recommendation was issued both for the patient’s own sake and for promoting treatment as prevention.

Switching to an etravirine-containing regimen due to drug intolerance in clinical practice

BACKGROUND

Drug intolerance is one of the main reasons for switching antiretroviral therapy in HIV-infected patients. Etravirine (ETR) has demonstrated good tolerability in clinical trials and may be an option for patients who switch therapy due to adverse events.

METHODS

We retrospectively reviewed all patients who had switched to an ETR-containing regimen in our center due to side effects. Virological suppression, ETR discontinuation, and reasons for discontinuation were studied.

RESULTS

A total of 78 patients started treatment with ETR in our center due to previous regimen toxicity. Most of them were men (83.3%), and the median time of infection was 14 years (IQR, 6.5-20 years). HIV RNA was <35 copies/mL in 88.3% of patients, although 33% had archived non-nucleos(t)ide reverse transcriptase inhibitor (NNRTI) mutations that did not compromise ETR efficacy. Efavirenz was the drug most often replaced (38.5%), followed by atazanavir (20.5%) and lopinavir (6.4%). The fixed combination of Trizivir was changed in another 10.3% of patients. After a median follow-up of 14 months (IQR, 6-23), the rate of virologic suppression was 79.5% and 98.4% in intention-to-treat and on-treatment analysis, respectively. Seven patients discontinued treatment due to adverse events (3 gastrointestinal disturbances, 2 rashes, 1 swelling, and 1 neuropathy). ETR was combined with 2 nucleos(t)ide analogues in 75.4% of patients.

CONCLUSION

In HIV patients who report drug side effects, switching to an ETR-containing regimen is a safe strategy in terms of virological suppression and toxicity.

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.

Randomised study to assess the efficacy and safety of once-daily etravirine-based regimen as a switching strategy in HIV-infected patients receiving a protease inhibitor-containing regimen. Etraswitch study

Background

Etravirine (ETR) was approved for patients with virological failure and antiretroviral resistance mutations. It has also shown antiviral efficacy in antiretroviral-naïve patients. However, data on the switching from protease inhibitors (PI) to ETR are lacking.

Methods

HIV-1-infected patients with suppressed viral load (VL) during a PI-containing regimen (>12 months) and no previous virological failure were randomized to switch from the PI to ETR (400 mg/day, dissolved in water) (ETR group, n = 22) or to continue with the same regimen (control group, n = 21). Percentage of patients with VL≤50 copies/mL were assessed at week 48, as well as changes in CD4 T-cell counts and metabolic profile.

Results

We included 43 patients [72.9% male, 46.3 (42.2; 50.6) years]. Two patients receiving ETR (grade-1 diarrhea and voluntary discontinuation) and another in the control group (simplification) discontinued therapy early. No patients presented virological failure (two consecutive VL>50 copies/mL); treatment was successful in 95.2% of the control group and 90.9% of the ETR group (intention-to-treat analysis, missing = failure) (p = 0.58). CD4+ T-cell counts did not significantly vary [+49 cells/µL in the ETR group (p = 0.25) and −4 cells/µL in the control group (p = 0.71)]. The ETR group showed significant reductions in cholesterol (p<0.001), triglycerides (p = <0.001), and glycemia (p = 0.03) and higher satisfaction (0–10 scale) (p = 0.04). Trough plasma concentrations of ETR were similar to observed in studies using ETR twice daily.

Conclusion

Switch from a PI-based regimen to a once-daily combination based on ETR maintained undetectable VL during 48 weeks in virologically suppressed HIV-infected patients while lipid profile and patient satisfaction improved significantly.

Trial Registration

ClinicalTrials.gov NCT01034917

Dolutegravir in antiretroviral-experienced patients with raltegravir- and/or elvitegravir-resistant HIV-1: 24-week results of the phase III VIKING-3 study

BACKGROUND

The pilot phase IIb VIKING study suggested that dolutegravir (DTG), a human immunodeficiency virus (HIV) integrase inhibitor (INI), would be efficacious in INI-resistant patients at the 50 mg twice daily (BID) dose.

METHODS

VIKING-3 is a single-arm, open-label phase III study in which therapy-experienced adults with INI-resistant virus received DTG 50 mg BID while continuing their failing regimen (without raltegravir or elvitegravir) through day 7, after which the regimen was optimized with ≥1 fully active drug and DTG continued. The primary efficacy endpoints were the mean change from baseline in plasma HIV-1 RNA at day 8 and the proportion of subjects with HIV-1 RNA <50 c/mL at week 24.

RESULTS

Mean change in HIV-1 RNA at day 8 was -1.43 log10 c/mL, and 69% of subjects achieved <50 c/mL at week 24. Multivariate analyses demonstrated a strong association between baseline DTG susceptibility and response. Response was most reduced in subjects with Q148 + ≥2 resistance-associated mutations. DTG 50 mg BID had a low (3%) discontinuation rate due to adverse events, similar to INI-naive subjects receiving DTG 50 mg once daily.

CONCLUSIONS

DTG 50 mg BID-based therapy was effective in this highly treatment-experienced population with INI-resistant virus.

CLINICAL TRIALS REGISTRATION

www.clinicaltrials.gov (NCT01328041) and http://www.gsk-clinicalstudywww.gsk-clinicalstudyregister.com (112574).

Cost-effectiveness of newer antiretroviral drugs in treatment-experienced patients with multidrug-resistant HIV disease

OBJECTIVE

Newer antiretroviral drugs provide substantial benefits but are expensive. The cost-effectiveness of using antiretroviral drugs in combination for patients with multidrug-resistant HIV disease was determined.

DESIGN

A cohort state-transition model was built representing treatment-experienced patients with low CD4 counts, high viral load levels, and multidrug-resistant virus. The effectiveness of newer drugs (those approved in 2005 or later) was estimated from published randomized trials. Other parameters were estimated from a randomized trial and from the literature. The model had a lifetime time horizon and used the perspective of an ideal insurer in the United States. The interventions were combination antiretroviral therapy, consisting of 2 newer drugs and 1 conventional drug, compared with 3 conventional drugs. Outcome measures were life-years, quality-adjusted life-years (QALYs), costs, and incremental cost-effectiveness.

RESULTS

Substituting newer antiretroviral drugs increased expected survival by 3.9 years in advanced HIV disease. The incremental cost-effectiveness ratio of newer, compared with conventional, antiretroviral drugs was $75,556/QALY gained. Sensitivity analyses showed that substituting only one newer antiretroviral drug cost $54,559 to $68,732/QALY, depending on assumptions about efficacy. Substituting 3 newer drugs cost $105,956 to $117,477/QALY. Cost-effectiveness ratios were higher if conventional drugs were not discontinued.

CONCLUSIONS

In treatment-experienced patients with advanced HIV disease, use of newer antiretroviral agents can be cost-effective, given a cost-effectiveness threshold in the range of $50,000 to $75,000 per QALY gained. Newer antiretroviral agents should be used in carefully selected patients for whom less expensive options are clearly inferior.

[Consensus Statement by GeSIDA/National AIDS Plan Secretariat on antiretroviral treatment in adults infected by the human immunodeficiency virus (Updated January 2013)]

OBJECTIVE

This consensus document is an update of combined antiretroviral therapy (cART) guidelines for HIV-1 infected adult patients.

METHODS

To formulate these recommendations a panel composed of members of the GeSIDA/National AIDS Plan Secretariat (Grupo de Estudio de Sida and the Secretaría del Plan Nacional sobre el Sida) reviewed the efficacy and safety advances in clinical trials, cohort and pharmacokinetic studies published in medical journals (PubMed and Embase) or presented in medical scientific meetings. The strength of the recommendations and the evidence which support them are based on a modification of the criteria of Infectious Diseases Society of America.

RESULTS

cART is recommended in patients with symptoms of HIV infection, in pregnant women, in serodiscordant couples with high risk of transmission, in hepatitisB co-infection requiring treatment, and in HIV nephropathy. cART is recommended in asymptomatic patients if CD4 is <500cells/μl. If CD4 are >500cells/μl cART should be considered in the case of chronic hepatitisC, cirrhosis, high cardiovascular risk, plasma viral load >100.000 copies/ml, proportion of CD4 cells <14%, neurocognitive deficits, and in people aged >55years. The objective of cART is to achieve an undetectable viral load. The first cART should include 2 reverse transcriptase inhibitors (RTI) nucleoside analogs and a third drug (a non-analog RTI, a ritonavir boosted protease inhibitor, or an integrase inhibitor). The panel has consensually selected some drug combinations, for the first cART and specific criteria for cART in acute HIV infection, in tuberculosis and other HIV related opportunistic infections, for the women and in pregnancy, in hepatitisB or C co-infection, in HIV-2 infection, and in post-exposure prophylaxis.

CONCLUSIONS

These new guidelines update previous recommendations related to first cART (when to begin and what drugs should be used), how to monitor, and what to do in case of viral failure or adverse drug reactions. cART specific criteria in comorbid patients and special situations are similarly updated.

Dual therapy with etravirine plus raltegravir for virologically suppressed HIV-infected patients: a pilot study

BACKGROUND

Clinical use of protease inhibitors (PIs) and nucleoside reverse transcriptase inhibitors (NRTIs) may be hampered by toxicity, interactions or resistance issues. Simple and effective antiretroviral regimens avoiding both drug classes may be needed for selected patients.

METHODS

This was a prospective cohort study. Virologically suppressed patients on PI or NRTI regimens, with problems of tolerability, safety concerns due to comorbidities or risk of drug interactions for both PIs and NRTIs, were given the opportunity to switch their regimen to etravirine plus raltegravir. Patients were required not to have prior virological failure to raltegravir and if there was prior non-nucleoside reverse transcriptase inhibitor (NNRTI) virological failure, only patients in whom efficacy of etravirine could be anticipated through the Stanford Drug Resistance Database were included. Follow-up was scheduled for at least 48 weeks, unless the patient was lost to follow-up or discontinued therapy.

RESULTS

Twenty-five patients were included. Their median age was 54 years; they had a median of 16 years on antiretroviral therapy and a median of nine previous regimens; 21 (84%) patients had previous virological failure; and 15 (60%) patients had a genotypic test that showed three or more NRTI mutations in 9 (36%), four or more PI mutations in 11 (44%) and at least one NNRTI mutation in 8 (32%) patients. At 48 weeks efficacy was 84% (95% CI 65.3%-93.6%) by intent-to-treat analysis and 91.3% (95% CI 73.2%-97.6%) by per-protocol analysis. One (4%) patient died, two (8%) discontinued due to intolerance and one (4%) experienced virological failure. The CD4/CD8 ratio and plasma lipids improved.

CONCLUSIONS

Dual therapy with etravirine plus raltegravir was well tolerated and maintained durable viral suppression in selected virologically suppressed patients for whom both PI and NRTI therapy was challenging.

Non-nucleoside reverse transcriptase inhibitors: a review on pharmacokinetics, pharmacodynamics, safety and tolerability

INTRODUCTION

Human immunodeficiency virus (HIV) type-1 non-nucleoside and nucleoside reverse transcriptase inhibitors (NNRTIs) are key drugs of highly active antiretroviral therapy (HAART) in the clinical management of acquired immune deficiency syndrome (AIDS)/HIV infection.

DISCUSSION

First-generation NNRTIs, nevirapine (NVP), delavirdine (DLV) and efavirenz (EFV) are drugs with a low genetic barrier and poor resistance profile, which has led to the development of new generations of NNRTIs. Second-generation NNRTIs, etravirine (ETR) and rilpivirine (RPV) have been approved by the Food and Drug Administration and European Union, and the next generation of drugs is currently being clinically developed. This review describes recent clinical data, pharmacokinetics, metabolism, pharmacodynamics, safety and tolerability of commercialized NNRTIs, including the effects of sex, race and age differences on pharmacokinetics and safety. Moreover, it summarizes the characteristics of next-generation NNRTIs: lersivirine, GSK 2248761, RDEA806, BILR 355 BS, calanolide A, MK-4965, MK-1439 and MK-6186.

CONCLUSIONS

This review presents a wide description of NNRTIs, providing useful information for researchers interested in this field, both in clinical use and in research.

Non-nucleoside reverse transcriptase inhibitor (NNRTI) cross-resistance: implications for preclinical evaluation of novel NNRTIs and clinical genotypic resistance testing

OBJECTIVES

The introduction of two new non-nucleoside reverse transcriptase inhibitors (NNRTIs) in the past 5 years and the identification of novel NNRTI-associated mutations have made it necessary to reassess the extent of phenotypic NNRTI cross-resistance.

METHODS

We analysed a dataset containing 1975, 1967, 519 and 187 genotype-phenotype correlations for nevirapine, efavirenz, etravirine and rilpivirine, respectively. We used linear regression to estimate the effects of RT mutations on susceptibility to each of these NNRTIs.

RESULTS

Sixteen mutations at 10 positions were significantly associated with the greatest contribution to reduced phenotypic susceptibility (≥10-fold) to one or more NNRTIs, including: 14 mutations at six positions for nevirapine (K101P, K103N/S, V106A/M, Y181C/I/V, Y188C/L and G190A/E/Q/S); 10 mutations at six positions for efavirenz (L100I, K101P, K103N, V106M, Y188C/L and G190A/E/Q/S); 5 mutations at four positions for etravirine (K101P, Y181I/V, G190E and F227C); and 6 mutations at five positions for rilpivirine (L100I, K101P, Y181I/V, G190E and F227C). G190E, a mutation that causes high-level nevirapine and efavirenz resistance, also markedly reduced susceptibility to etravirine and rilpivirine. K101H, E138G, V179F and M230L mutations, associated with reduced susceptibility to etravirine and rilpivirine, were also associated with reduced susceptibility to nevirapine and/or efavirenz.

CONCLUSIONS

The identification of novel cross-resistance patterns among approved NNRTIs illustrates the need for a systematic approach for testing novel NNRTIs against clinical virus isolates with major NNRTI-resistance mutations and for testing older NNRTIs against virus isolates with mutations identified during the evaluation of a novel NNRTI.

Genetic barrier to the development of resistance to rilpivirine and etravirine between HIV-1 subtypes CRF02_AG and B

OBJECTIVES

It has been demonstrated for some drugs that the genetic barrier, defined as the number of genetic transitions and/or transversions needed to produce a resistance mutation, can differ between HIV-1 subtypes. We aimed to assess differences in the genetic barrier for the evolution of resistance to the second-generation non-nucleoside reverse transcriptase inhibitors etravirine and rilpivirine in subtypes B and CRF02_AG in antiretroviral-naive patients.

METHODS

An analysis was undertaken of 25 substitutions associated with etravirine and rilpivirine resistance at 12 amino acid positions in 267 nucleotide sequences (136 HIV-1 B and 131 HIV-1 CRF02_AG subtypes) of the reverse transcriptase gene.

RESULTS

The majority (7/12) of amino acid positions studied were conserved between the two HIV-1 subtypes, leading to a similar genetic barrier. Different predominant codons between the subtypes were observed in 5/12 positions (90, 98, 179, 181 and 227), with an effect on the calculated genetic barrier only at the V179D and V179F codons (2.5 versus 3.5 for V179D, and 2.5 versus 5 for V179F, respectively, for subtype B versus subtype CRF02_AG).

CONCLUSIONS

The majority of amino acids involved in etravirine and rilpivirine resistance showed a high degree of conservation of the predominant codon between the B and CRF02_AG subtypes. For rilpivirine, the genetic barrier was the same between the two subtypes. Nevertheless, subtype CRF02_AG showed a higher genetic barrier to acquiring mutations V179D and V179F (mutations associated with resistance to etravirine) compared with subtype B, suggesting that it would be more difficult to produce resistance to etravirine in the CRF02_AG subtype than the B subtype.

Lopinavir/ritonavir versus darunavir plus ritonavir for HIV infection: a cost-effectiveness analysis for the United States

BACKGROUND

The ARTEMIS trial compared first-line antiretroviral therapy (ART) with lopinavir/ritonavir (LPV/r) to darunavir plus ritonavir (DRV + RTV) for HIV-1-infected subjects. In order to fully assess the implications of this study, economic modelling extrapolating over a longer term is required.

OBJECTIVE

The aim of this study was to simulate the course of HIV and its management, including the multiple factors known to be of importance in ART.

METHODS

A comprehensive discrete event simulation was created to represent, as realistically as possible, ART management and HIV outcomes. The model was focused on patients for whom clinicians believed that LPV/r or DRV + RTV were good options as a first regimen. Prognosis was determined by the impact of initial treatment on baseline CD4+ T-cell count and viral load, adherence, virological suppression/failure/rebound, acquired resistance mutations, and ensuing treatment changes. Inputs were taken from trial data (ARTEMIS), literature and, where necessary, stated assumptions. Clinical measures included AIDS events, side effects, time on sequential therapies, cardiovascular events, and expected life-years lost as a result of HIV infection. The model underwent face, technical and partial predictive validation. Treatment-naive individuals similar to those in the ARTEMIS trial were modelled over a lifetime, and outcomes with first-line DRV + RTV were compared with those with LPV/r, both paired with tenofovir and emtricitabine. Up to three regimen changes were permitted. Drug prices were based on wholesale acquisition cost. Outcomes were lifetime healthcare costs (in 2011 US dollars) from the US healthcare system perspective and quality-adjusted life-years (QALYs) (discounted at 3 % per annum).

RESULTS

Choice of LPV/r over DRV + RTV as initial ART resulted in nearly identical clinical outcomes, but distinctly different economic consequences. Starting with an LPV/r regimen potentially results in approximately US$25,000 discounted lifetime savings. Accumulated QALYs for LPV/r and DRV + RTV were 12.130 and 12.083, respectively (a 19-day difference). In sensitivity analyses, net monetary benefit ranged from US$12,000 to US$31,000, favouring LPV/r (base case US$27,762).

CONCLUSIONS

A comprehensive simulation of lifetime course of HIV in the USA indicated that using LPV/r as first-line therapy compared with DRV + RTV may result in cost savings, with similar clinical outcomes.

Prevalence of etravirine (ETR)-RAMs at NNRTI failure and predictors of resistance to ETR in a large Italian resistance database (ARCA)

The prevalence of drug resistance associated with the failure of non-nucleoside reverse transcriptase inhibitor (NNRTI)-based regimens and the predictors of resistance to Etravirine (ETR) were assessed in 2854 subjects: 39 < 18 (paediatric) and 2815 ≥ 18 (adult) years old. These subjects failed to respond to their current NNRTI treatment, were three-class experienced and had been exposed to NNRTI for ≥3 months. A total of 1827 adult (64.9%) and 32 paediatric subjects (82.1%) harboured the virus with at least one ETR mutation. V179I, Y181C and G190A were the most frequent mutations in both groups. A significantly increased risk of ETR resistance with all three algorithms (Monogram (MGR) >3, Tibotec (TBT) >2 and enhanced MGR (ENH) ≥4) emerged in the paediatric population. Multivariate analysis revealed an increased risk of developing TBT >2 for NNRTI exposure, ENH ≥4 for NNRTI and EFV exposure in paediatric subjects; NVP exposure and higher (≥3.5 log10) HIV-RNA values for all three algorithms in adult subjects, whereas CD4 ≥ 200/μL appeared to be protective. The risk of being ETR resistant was more than doubled for paediatric vs. adult subjects, probably due to a more extensive use of NNRTI and an incomplete virological control.

Effect of mutations at position E138 in HIV-1 reverse transcriptase and their interactions with the M184I mutation on defining patterns of resistance to nonnucleoside reverse transcriptase inhibitors rilpivirine and etravirine

Impacts of mutations at position E138 (A/G/K/Q/R/V) alone or in combination with M184I in HIV-1 reverse transcriptase (RT) were investigated. We also determined why E138K is the most prevalent nonnucleoside reverse transcriptase inhibitor mutation in patients failing rilpivirine (RPV) therapy. Recombinant RT enzymes and viruses containing each of the above-mentioned mutations were generated, and drug susceptibility was assayed. Each of the E138A/G/K/Q/R mutations, alone or in combination with M184I, resulted in decreased susceptibility to RPV and etravirine (ETR). The maximum decrease in susceptibility to RPV was observed for E138/R/Q/G by both recombinant RT assay and cell-based assays. E138Q/R-containing enzymes and viruses also showed the most marked decrease in susceptibility to ETR by both assays. The addition of M184I to the E138 mutations did not significantly change the levels of diminution in drug susceptibility. These findings indicate that E138R caused the highest level of loss of susceptibility to both RPV and ETR, and, accordingly, E138R should be recognized as an ETR resistance-associated mutation. The E138K/Q/R mutations can compensate for M184I in regard to both enzymatic fitness and viral replication capacity. The favored emergence of E138K over other mutations at position E138, together with M184I, is not due to an advantage in either the level of drug resistance or viral replication capacity but may reflect the fact that E138R and E138Q require two distinct mutations to occur, one of which is a disfavorable G-to-C mutation, whereas E138K requires only a single favorable G-to-A hypermutation. Of course, other factors may also affect the concept of barrier to resistance.

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.

A cohort study of treatment-experienced HIV-1-infected patients treated with raltegravir: factors associated with virological response and mutations selected at failure

This study aimed to identify factors associated with virological response (VR) to raltegravir (RAL)-containing regimens in 468 treatment-experienced but integrase inhibitor-naive HIV-1 patients receiving a RAL-containing regimen. VR was defined at Month 6 (M6) as HIV-1 RNA viral load (VL) <50 copies/mL. The impacts on VR of baseline integrase mutations, VL, CD4 count, genotypic sensitivity score for nucleoside reverse transcriptase inhibitors, non-nucleoside reverse transcriptase inhibitors and protease inhibitors, and the number of new antiretrovirals used for the first time associated with RAL were investigated. For patients with VL >50 copies/mL at M6, integrase mutations selected were characterised. Median baseline VL was 4.2 log(10)copies/mL (IQR 3.3-4.9 log(10) copies/mL) and CD4 count was 219 cells/mm(3) (IQR 96-368 cells/mm(3)). At M6, 71% of patients were responders. In multivariate analysis, baseline VL and CD4 count and ≥ 2 new antiretrovirals among darunavir, etravirine, maraviroc and enfuvirtide were associated with VR to RAL. Neither HIV-1 subtype nor baseline integrase polymorphisms were associated with VR to RAL. Among 63 failing patients at M6, selection of ≥ 1 change in the integrase gene was observed in 49 (77.8%), and 27/63 (42.9%) were considered as RAL-associated resistance mutations. Factors independently associated with the occurrence of ≥ 1 RAL-associated resistance mutation were VL at failure >3 log(10) and having no new drugs associated with RAL. RAL showed great potency in treatment-experienced patients. The number of new drugs associated with RAL was an important factor associated with VR. HIV-1 subtype and baseline integrase polymorphisms do not influence the RAL VR.

Closing the door to human immunodeficiency virus

The pandemic of human immunodeficiency virus type one (HIV-1), the major etiologic agent of acquired immunodeficiency disease (AIDS), has led to over 33 million people living with the virus, among which 18 million are women and children. Until now, there is neither an effective vaccine nor a therapeutic cure despite over 30 years of efforts. Although the Thai RV144 vaccine trial has demonstrated an efficacy of 31.2%, an effective vaccine will likely rely on a breakthrough discovery of immunogens to elicit broadly reactive neutralizing antibodies, which may take years to achieve. Therefore, there is an urgency of exploring other prophylactic strategies. Recently, antiretroviral treatment as prevention is an exciting area of progress in HIV-1 research. Although effective, the implementation of such strategy faces great financial, political and social challenges in heavily affected regions such as developing countries where drug resistant viruses have already been found with growing incidence. Activating latently infected cells for therapeutic cure is another area of challenge. Since it is greatly difficult to eradicate HIV-1 after the establishment of viral latency, it is necessary to investigate strategies that may close the door to HIV-1. Here, we review studies on non-vaccine strategies in targeting viral entry, which may have critical implications for HIV-1 prevention.

Rilpivirine in treatment-naive patients: what did we learn from the THRIVE and ECHO studies?

Rilpivirine is a new non-nucleoside reverse transcriptase inhibitor with potent activity against HIV-1. The THRIVE and ECHO studies are multinational, randomized, placebo-controlled, double-blinded clinical trials that evaluated the efficacy of rilpivirine once daily versus efavirenz once daily in initial antiretroviral regimen for treatment-naive patients. At week 48 of treatment, rilpivirine was noninferior to efavirenz by the intention-to-treat time-to-loss-of-virologic-response. Of note, patients treated with rilpivirine had a higher rate of virologic failure whereas those treated with efavirenz had a higher rate of adverse events-associated discontinuation. The lower response among patients on rilpivirine compared with efavirenz was observed when pretreated plasma viral load was >100,000 copies/ml. Rilpivirine improved tolerability versus efavirenz particularly for dizziness, abnormal dream, rash and dyslipidemia. Patients with rilpivirine-associated mutations had a likelihood for reduced susceptibility to other non-nucleoside reverse transcriptase inhibitors, especially etravirine, in subsequent antiretroviral regimens. Rilpivirine is contraindicated for use with proton-pump inhibitors.

Maraviroc observational study: the impact of expanded resistance testing and clinical considerations for antiretroviral regimen selection in treatment-experienced patients

Maraviroc (MVC) use has trailed that of other post-2006 antiretroviral therapy (ART) options for treatment-experienced patients. We explored the impact of free tropism testing on MVC utilization in our cohort and explored barriers to MVC utilization. The Maraviroc Outcomes Study (MOS) is an investigator-initiated industry-sponsored trial where consecutive ART-experienced patients receiving routine care with viral loads ≥1,000 copies/ml, and whose provider requested resistance testing and received standardized resistance testing (SRT; phenotype, genotype, coreceptor/tropism). Sociodemographic, clinical, and ART characteristics of those receiving SRT were compared to a historical cohort (HC). Subsequently, providers were surveyed regarding factors influencing selection of salvage ART therapy. The HC (n=165) had resistance testing 7/08-9/09, while prospective SRT (n=83) patients were enrolled 9/09-8/10. In the HC, 92% had genotypes, 2% had tropism assays, and 62% (n=102) changed ART after resistance testing (raltegravir 37%, etravirine 25%, darunavir 24%, MVC 1%). In the SRT cohort, 57% (n=48) changed regimens after standardized resistance testing (darunavir 48%, raltegravir 40%, and etravirine 19%). CCR5-tropic virus was identified in 43% of the SRT group, and MVC was used in 10% [or 20% of R5 tropic patients who underwent a subsequent regimen change (n=25)], a statistically significant (p=0.01) increase in utilization. The factors most strongly influencing utilization were unique patient circumstances (60%), clinical experience (55%), and potential side effects (40%). The addition of routine tropism testing to genotypic/phenotypic testing was associated with increased MVC utilization, raising the possibility that tropism testing may present a barrier to MVC use; however, additional barriers exist, and merit further evaluation.

The Need for Development of New HIV-1 Reverse Transcriptase and Integrase Inhibitors in the Aftermath of Antiviral Drug Resistance

The use of highly active antiretroviral therapy (HAART) involves combinations of drugs to achieve maximal virological response and reduce the potential for the emergence of antiviral resistance. There are two broad classes of reverse transcriptase inhibitors, the nucleoside reverse transcriptase inhibitors (NRTIs) and nonnucleoside reverse transcriptase inhibitors (NNRTIs). Since the first classes of such compounds were developed, viral resistance against them has necessitated the continuous development of novel compounds within each class. This paper considers the NRTIs and NNRTIs currently in both preclinical and clinical development or approved for second line therapy and describes the patterns of resistance associated with their use, as well as the underlying mechanisms that have been described. Due to reasons of both affordability and availability, some reverse transcriptase inhibitors with low genetic barrier are more commonly used in resource-limited settings. Their use results to the emergence of specific patterns of antiviral resistance and so may require specific actions to preserve therapeutic options for patients in such settings. More recently, the advent of integrase strand transfer inhibitors represents another major step forward toward control of HIV infection, but these compounds are also susceptible to problems of HIV drug resistance.

Mean cost of a first combination antiretroviral therapy in HIV-infected patients in France, and determinants of expensive drugs prescription

To estimate the cost of the first combination antiretroviral drug therapy (cART) in HIV-infected patients and to determine factors associated with expensive prescriptions, 1698 patients starting cART between September 2002 and September 2007 were selected from the Dat'AIDS cohort. A multivariate linear regression model was used to assess associations between the cost of first cART and patient characteristics, clinical centre and cART adequacy. At cART initiation, the median age was 39 years, median CD4 count was 223 cells/mm3, median viral load (VL) was 5.2 log copies/mL and 18.3% presented with AIDS. cART was concordant with the French guidelines in 88.7%. The mean cost of cART varied from €26.69/day/person in 2002-2003 to €32.23 in 2006-2007 ( P < 0.0001), cost was associated with previous AIDS diagnosis (€31.83/day/person) versus (29.49; P < 0.0001), baseline VL > 5 log copies/mL (€30.99/day/person) versus (28.33; P < 0.0001) and centre. cART regimen not concordant with guidelines were more expensive (€38.31/day/person) versus (29.07; P < 0.0001). After adjusting for the year of initiation, the previous AIDS diagnosis, VL and recommended cART regimen, differences were still found between centres (from €27.81/day/person) to (33.12; P < 0.0001). Cost should be considered when choosing a first cART regimen, especially when considering clinically equivalent regimens.

Drug resistance in HIV-1

PURPOSE OF THE REVIEW

Changing antiretroviral regimens and the introduction of new antiretroviral drugs have altered drug resistance patterns in human immunodeficiency virus type 1 (HIV-1). This review summarizes recent information on antiretroviral drug resistance.

RECENT FINDINGS

As tenofovir and abacavir have replaced zidovudine and stavudine in antiretroviral regimens, thymidine analog resistance mutations have become less common in patients failing antiretroviral therapy in developed countries. Similarly, the near universal use of ritonavir-boosted protease inhibitors (PI) in place of unboosted PIs has made the selection of PI resistance mutations uncommon in patients failing a first-line or second-line PI regimen. The challenge of treating patients with multidrug-resistant HIV-1 has largely been addressed by the advent of newer PIs, second-generation non-nucleoside reverse transcriptase inhibitors and drugs in novel classes, including integrase inhibitors and CCR5 antagonists. Resistance to these newer agents can emerge, however, resulting in the appearance of novel drug resistance mutations in the HIV-1 polymerase, integrase and envelope genes.

SUMMARY

New drugs make possible the effective treatment of multidrug-resistant HIV-1, but the activity of these drugs may be limited by the appearance of novel drug resistance mutations.

Cost-Effectiveness of Antiretroviral Therapy for Multidrug-Resistant HIV: Past, Present, and Future

In the early years of the highly active antiretroviral therapy (HAART) era, HIV with resistance to two or more agents in different antiretroviral classes posed a significant clinical challenge. Multidrug-resistant (MDR) HIV was an important cause of treatment failure, morbidity, and mortality. Treatment options at the time were limited; multiple drug regimens with or without enfuvirtide were used with some success but proved to be difficult to sustain for reasons of tolerability, toxicity, and cost. Starting in 2006, data began to emerge supporting the use of new drugs from the original antiretroviral classes (tipranavir, darunavir, and etravirine) and drugs from new classes (raltegravir and maraviroc) for the treatment of MDR HIV. Their availability has enabled patients with MDR HIV to achieve full and durable viral suppression with more compact and cost-effective regimens including at least two and often three fully active agents. The emergence of drug-resistant HIV is expected to continue to become less frequent in the future, driven by improvements in the convenience, tolerability, efficacy, and durability of first-line HAART regimens. To continue this trend, the optimal rollout of HAART in both rich and resource-limited settings will require careful planning and strategic use of antiretroviral drugs and monitoring technologies.

Etravirine: a guide to its use in treatment-experienced pediatric patients with HIV-1 infection in the US

Etravirine (Intelence®), an oral next-generation non-nucleoside reverse transcriptase inhibitor (NNRTI), is approved for the treatment of HIV-1 infection in treatment-experienced patients. In the US, the approved use of etravirine in patients who have evidence of viral replication and harbor HIV-1 strains resistant to other antiretroviral agents has recently been expanded to include pediatric patients aged ≥ 6 to <18 years. At 24 and 48 weeks in an open-label trial, etravirine 5.2 mg/kg twice daily (maximum dosage 200 mg twice daily) plus an optimized background therapy regimen achieved complete viral response (defined as HIV-1 RNA <50 copies/mL) in approximately half of treatment-experienced children and adolescents with HIV-1 infection and evidence of viral replication, and had an acceptable tolerability profile.

Antiviral drug resistance and the need for development of new HIV-1 reverse transcriptase inhibitors

Highly active antiretroviral therapy (HAART) consists of a combination of drugs to achieve maximal virological response and reduce the potential for the emergence of antiviral resistance. Despite being the first antivirals described to be effective against HIV, reverse transcriptase inhibitors remain the cornerstone of HAART. There are two broad classes of reverse transcriptase inhibitor, the nucleoside reverse transcriptase inhibitors (NRTIs) and nonnucleoside reverse transcriptase inhibitors (NNRTIs). Since the first such compounds were developed, viral resistance to them has inevitably been described; this necessitates the continuous development of novel compounds within each class. In this review, we consider the NRTIs and NNRTIs currently in both preclinical and clinical development or approved for second-line therapy and describe the patterns of resistance associated with their use as well as the underlying mechanisms that have been described. Due to reasons of both affordability and availability, some reverse transcriptase inhibitors with a low genetic barrier are more commonly used in resource-limited settings. Their use results in the emergence of specific patterns of antiviral resistance and so may require specific actions to preserve therapeutic options for patients in such settings.

Optimizing background therapy in treatment-experienced HIV-1 patients by rules-based algorithms and bioinformatics

In HIV-1-infected patients with extensive drug resistance, the optimization of background antiretroviral therapy is essential when changing drugs after treatment failure. The genotypic sensitivity score (GSS) and phenotypic sensitivity score (PSS), determined by rules-based algorithms, are employed to predict which drugs to select in a background therapy in order to receive the best treatment response when a new drug will be used, both in investigational trials of new agents and in clinical care. However, the outcome of the GSS/PSS approach for the purpose of assessing antiretroviral efficacy in patients with multiresistance has become more problematic, despite improvements such as drug potency weighting and adding information on treatment history. Bioinformatics-based methods are more recent attractive alternatives that have demonstrated equal or better precision compared with rules-based algorithms. This review aims to discuss the usefulness of GSS/PSS and bioinformatics, respectively, for the optimization of anti-HIV background therapy in heavily treatment-experienced patients.

Minority variants associated with resistance to HIV-1 nonnucleoside reverse transcriptase inhibitors during primary infection

BACKGROUND

Recent data suggest that subjects harbouring low-frequency variants of HIV that are resistant to non-nucleoside reverse-transcriptase inhibitors (NNRTI) could suffer virological failure when treated with NNRTI-based therapy. Rilpivirine, a second-generation NNRTI, will be used in first-line regimen therapy, but the prevalence of minority variants that are resistant to rilpivirine is unknown.

OBJECTIVES

We evaluated the presence of low-frequency NNRTI resistance associated mutations (RAMs) in 27 patients with a primary HIV-1 infection.

STUDY DESIGN

We performed genotypic resistance test at baseline and used ultradeep pyrosequencing (UDPS) to detect minority RAMs.

RESULTS

Bulk genotyping identified NNRTI-resistant RAMs in 3/27 (11%) patients while UDPS identified NNRTI-resistant RAMs in 10/27 (37%) patients. The 11 RAMs not detected by bulk sequencing were A98G (n=2), L100I (n=3), K101E (n=2), V106I (n=3) and E138G (n=1). The prevalence of these minority variants was 0.34-18.26%. The absolute copy numbers of minority resistant variants were 3.21-5.53 log copies/mL. CRF02 harboured more minority resistant variants than subtypes B (P<0.05). Four samples (15%) had a major rilpivirine resistant mutation (E138G, K101E and E138A), 3 of which were detected by UDPS.

CONCLUSION

In these primary HIV infected patients, as regards to the detection of RAMs at the cut-off level>15-25% of the virus population, the concordance between bulk genotypic and UDPS was perfect. UDPS detected additional major NNRTI-resistant mutations, including rilpivirine resistant variants. Further studies are needed to assess the impact of these minority variants on treatment efficacy.

NNRTIs: pharmacological data

One of the choice criteria for antiretroviral therapy, once the viral load is controlled, is long-term treatment safety. Safety, despite similarities in each therapeutic class, can differ significantly from one agent to another, according to their respective pharmacokinetic and pharmacodynamic properties. We reviewed data on two very well-known NNRTIs, efavirenz and nevirapine, in this context. The pharmacokinetic properties of both agents are presented along with their impact on residual viremia and viral reservoirs, as well as their clinical consequences. The implications for the penetration of these antiretroviral drugs in the CNS and in female and male genital tracts are also discussed. Pharmacogenetics could become an interesting tool. Finally, the availability of new NNRTIs has recently boosted this therapeutic class, even if their long-term properties remain to be assessed. The consideration of all this data stresses the importance of communication among clinicians, virologists, and pharmacologists before choosing a treatment.