Week 96 efficacy and safety of rilpivirine in treatment-naive, HIV-1 patients in two Phase III randomized trials

Real-world effectiveness and tolerability of switching to doravirine-based antiretroviral therapy in people with HIV: a nationwide, matched, prospective cohort study

BACKGROUND

Currently, real-world data on doravirine are scarce. In a national prospective cohort, we assessed the effectiveness and tolerability of switching to doravirine-based antiretroviral therapy (ART) in people with HIV.

METHODS

We did a nationwide, matched, prospective cohort study of people with HIV without previous virological failure and stable for at least 12 months on non-doravirine-containing triple or dual ART switching to doravirine before Sept 1, 2020 (exposed group). Participants in the exposed group were matched 1:2 to individuals continuing stable non-doravirine-containing ART, on age, sex, HIV acquisition category, time since ART initiation, calendar time, pre-ART CD4-count, pre-ART plasma viral load (PVL) and anchor drug class before switching. The primary outcome was protocol-defined virological failure (PDVF; PVL of ≥200 copies per mL) in the intention-to-treat (ITT) population at week 104, with participants modifying their regimen or becoming lost to follow-up considered as PDVF (non-inferiority margin +5%). In contrast, in the on-treatment population, those who modified their regimen or became lost to follow-up were censored from that moment onwards. Tolerability was a secondary outcome.

FINDINGS

In total, 590 participants in the exposed group and 1180 participants in the unexposed group (of whom 55·3% used integrase strand transfer inhibitor-based regimens) were included. In the ITT analysis, PDVF occurred in 135 (22·9%) exposed participants and in 295 (25·0%) unexposed participants (risk difference -2·12%, upper limit of the one-sided 95% CI +1·40%). In the on-treatment analysis, 10 (2·2%) of 455 non-censored exposed participants and 26 (2·9%) of 885 non-censored unexposed participants had PDVF (risk difference -0·70%, upper limit of the one-sided 95% CI +0·73%). All exposed participants with a PVL of 200 copies or more per mL resuppressed without regimen modification: no confirmed virological failure (two consecutive PVLs of ≥200 copies per mL) was observed. 104 (17·6%) exposed participants and 211 (17·9%) unexposed participants modified their regimen. 73 (12.4%) exposed participants discontinued doravirine due to adverse events: abnormal dreams (1·7%) and insomnia (1·5%) were most common.

INTERPRETATION

Switching to doravirine in well suppressed people with HIV without previous virological failure was non-inferior compared with continuing non-doravirine-containing regimens after 2 years in a real-world setting.

FUNDING

None.

Recommendations for the use of antiretroviral therapy in adults living with human immunodeficiency virus in Singapore

ABSTRACT

Since the advent of combination antiretroviral therapy (ART), the mortality attributable to human immunodeficiency virus (HIV) infection has decreased by 80%. Newer antiretroviral agents are highly efficacious, have minimal side effects as compared to older drugs, and can be formulated as combination tablets to reduce patients' pill burden. Despite these advances, 680,000 people worldwide died of acquired immunodeficiency syndrome-related illnesses in 2020. The National ART and Monitoring Recommendations by the National HIV Programme have been created to guide physicians on the prescribing of ART based on the patients' needs. These recommendations are based on international guidelines and tailored to the local context and unique domestic considerations. We hoped that with the publication of these recommendations, the care of people living with HIV can be enhanced, bringing us closer to ending HIV in our lifetime.

Incidence of Diabetes Mellitus and Associated Factors in the Era of Antiretroviral Drugs With a Low Metabolic Toxicity Profile

Objective

The incidence of type 2 diabetes mellitus (T2DM) has risen dramatically. Among people living with HIV (PLHIV), chronic disease (now >15 cases/1000 in the general population worldwide) and long-term exposure to antiretroviral therapy (ART) can alter metabolic processes early, favoring insulin resistance and T2DM. We retrospectively studied the incidence of T2DM and associated factors in the Cohort of the Spanish AIDS Research Network, a prospective cohort of PLHIV enrolled at diagnosis and before initiation of ART.

Methods

PLHIV were aged >18 years and ART naive at inclusion. The incidence of new diagnoses of T2DM after initiation of ART (per 1000 person-years) was calculated. Predictors of a diagnosis of T2DM were identified by a Cox proportional hazards model adjusted for statistically significant and clinically relevant variables.

Results

Cumulative incidence was 5.9 (95% CI, 5.1-6.7) per 1000 person-years, increasing significantly in persons aged >50 years to 14.4 (95% CI, 10.4-19.3). Median time to diagnosis of T2DM was 27 months. Only age and higher education were significant. Interestingly, higher education was associated with a 33% reduction in the incidence of T2DM. Having received tenofovir disoproxil fumarate + (lamivudine or emtricitabine) + rilpivirine was almost significant as a protective factor (hazard ratio, 0.49; 95% CI, .24-1.01; P = .05).

Conclusions

The incidence of T2DM in PLHIV in Spain was high, especially in persons aged >50 years. Age was the factor most closely associated with onset, and educational level was the factor most associated with reduced risk. We highlight the lack of association between HIV-related factors and T2DM and show that, within nonnucleoside reverse transcriptase inhibitors, rilpivirine could prove more benign for metabolic comorbidities.

An evaluation of long-acting cabotegravir + rilpivirine for the treatment of virologically suppressed adults living with HIV

INTRODUCTION

HIV is a global disease that has seen significant improvements in care over the past decades. Despite improvements, treatments for maintaining suppression are complex for patients and include two to three oral medications. The approval of intramuscular cabotegravir (CAB) and rilpivirine (RPV) offers a new therapeutic modality with the opportunity of a longer dosing frequency. The data from recent trials including FLAIR and ATLAS have shown non-inferiority in treatment based on the current standard of care. This approval has the potential to simplify patient medication regimens, while maintaining virologic suppression in HIV-1 patients.

AREAS COVERED

Cabotegravir + rilpivirine's recent approval for the treatment of HIV and its significant impact it may have on people living with HIV.

EXPERT OPINION

Cabotegravir + rilpivirine is a long-acting injectable that can be used for patients who want to reduce the frequency antiretroviral administration. CAB+RPV allows for virologic suppression with monthly or less often administration, but comes with a significant price point, although injection site reactions may limit utility for many patients.

Switching efavirenz to rilpivirine in virologically suppressed adolescents with HIV: a multi-centre 48-week efficacy and safety study in Thailand

INTRODUCTION

Efavirenz (EFV) is commonly used for first-line antiretroviral therapy in children and adolescents with HIV, but is associated with neuropsychiatric and metabolic side effects. Rilpivirine (RPV) is better tolerated, and switching from EFV to RPV in virologically suppressed adults has been safe and efficacious, but data in adolescents are limited. Our primary objective was to describe the 48-week immunologic and virologic outcomes in virologically suppressed adolescents switching from EFV- to RPV-based antiretroviral therapy. Secondary objectives included assessment of neuropsychiatric adverse events, quality of life (QOL) and metabolic profiles while on RPV.

METHODS

We conducted an open-label, single-arm, multi-centre study in Thailand in virologically suppressed adolescents aged 12-18 years receiving EFV plus two nucleoside/tide reverse transcriptase inhibitors (NRTIs/NtRTI) for ≥3 months. Participants were switched to an RPV (25 mg) tablet once daily, with the same NRTIs. HIV RNA viral load, CD4 cell count, fasting total cholesterol (TC), triglyceride, glucose, neuropsychiatric adverse events, depression and QOL were assessed over 48 weeks. Data were collected between February 2016 and September 2018.

RESULTS

One hundred and two (52% male) adolescents were enrolled. Median age at entry was 15.5 years (IQR 14.4-17.0), median CD4 count was 664 cells/mm³ (29.9%); 58% were receiving tenofovir-DF and emtricitabine. At weeks 24 and 48, 96 (94.1%) and 94 (92.2%) participants were virologically suppressed, respectively, with no significant change in CD4 cell counts from baseline. Six (5.9%) participants experienced virologic failure, two of whom had RPV-associated mutations (K101E and Y181C) and a lamivudine-associated mutation (M184V/I). There were significant decreases in TC, triglyceride, high-density lipoprotein (HDL) and low-density lipoprotein (LDL) at weeks 24 and 48 and a significant increase in LDL/HDL ratio at week 48 compared to baseline. No substantial changes in EFV-related symptoms, depression score or health-related QOL were observed over time; however, there was significant improvement in performance-based assessments of executive function at week 24.

CONCLUSIONS

A high proportion of adolescents (>92%) remained virologically suppressed up to 48 weeks after switching from EFV to RPV along with no significant change in CD4 cell counts. RPV was well tolerated and associated with improvements in metabolic profiles and executive function.

Long-term safety, tolerability and antiviral activity of rilpivirine in antiretroviral-naïve adolescents living with HIV-1, aged 12 to less than 18 years: Week 240 findings of a phase 2, open-label study, PAINT

This phase 2 study investigated long-term safety and efficacy of rilpivirine (RPV) plus two investigator-selected nucleos(t)ide reverse transcriptase inhibitors (NRTIs) in HIV-1-infected antiviral therapy-naive adolescents. Participants (≥12 to <18 years of age) were treated with RPV at 25 mg once daily (q.d.) plus 2 NRTIs and entered the treatment extension period for up to 240 weeks, with visits every 3 months. Long-term safety (analysis of adverse events [AEs] and laboratory results), efficacy (virologic response and outcome for patients with viral loads of <50 and <400 by time to loss of virologic response [TLOVR] and FDA Snapshot methods, as well as CD4⁺ cell count), and adherence (by pill count) for up to 240 weeks are presented. Twenty-four of 36 participants entered the treatment extension period, and 21 completed week 240. At week 240, a viral load of <50 copies/mL was achieved by 14/32 (43.8%) participants; virologic response by TLOVR was higher in participants with a baseline viral load of ≤100,000 copies/mL (48.0%) versus a viral load of >100,000 copies/mL (28.6%). By FDA Snapshot, a viral load of <50 copies/mL at week 240 was found in 53.1% (17/32) of participants with a baseline viral load of ≤100,000 copies/mL. Higher response was observed in participants with adherence of >95% and a baseline viral load of ≤100,000 copies/mL. Through week 240, 16/32 participants (50.0%) experienced virologic failure, including seven who developed treatment-emergent RPV resistance-associated mutations (RAMs [frequently E138K]): all 7 had ≥1 treatment-emergent NRTI RAM. No serious AEs after week 48, no discontinuations due to AEs between week 48 and week 240, and no new safety signals were observed. RPV did not affect pubertal development or adolescent growth. At the 5-year follow-up, efficacy was low in adolescents, particularly those with poor adherence and/or a high baseline viral load of >100,000 copies/mL. To limit the risk of virologic failure, RPV is restricted to patients with a baseline VL of ≤100,000 copies/mL in most countries. In addition, adequate treatment adherence to RPV treatment is imperative for long-term viral suppression and should be emphasized in the management of adolescents living with HIV. RPV exhibited a favorable long-term safety profile for adolescents living with HIV-1 with adequate adherence. (This study has been registered at ClinicalTrials.gov under identifier NCT00799864.)

Long-term safety and efficacy of rilpivirine in combination with nucleoside/nucleotide reverse transcriptase inhibitors in HIV-1 infected patients: 336-week rollover study of phase 2b and 3 clinical studies

Background

To evaluate the long-term safety and efficacy of rilpivirine (RPV), a non-nucleoside reverse transcriptase inhibitor (NNRTI), in combination with nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs) in human immunodeficiency virus (HIV)–infected patients.

Methods

RPV-treated HIV-infected patients from phase 2b or 3 studies rolled-over into this phase 3, open-label study and received RPV 25 mg once daily (QD) with choice of two NRTIs. Adverse events (AEs), plasma viral load, CD4+ cell count, and antiviral resistance were evaluated.

Results

Of the 482 patients treated, 437 (>90%) patients discontinued study treatment; 371 (77%) had switched to commercially available RPV, 14 (2.9%) discontinued due to AEs, and 6 (1.2%) had virologic failure. In this rollover study, patients were followed up to week 336, although data was limited beyond 288 weeks. Forty-five (9.3%) patients were still undergoing treatment at the time of data cut-off for the current analysis (8 February 2018). The most frequently reported AEs were pregnancy in 7 (1.5%) patients and syphilis in 5 (1.0%) patients. Grade 3–4 AEs were reported in 17 (3.5%) patients, and AEs possibly related to RPV in 23 (4.8%) patients. Over 288 weeks of treatment, 80.1% (95% CI: 74.9%; 84.3%) of patients maintained virologic suppression (HIV-1 RNA <50 copies/mL). The absolute CD4+ cell count increased over time until week 192 and remained constant thereafter.

Conclusions

RPV 25 mg QD in combination with an investigator-selected background regimen of two NRTIs demonstrated sustained long-term virologic suppression. The treatment was well-tolerated with no new safety findings.

Three-Drug Regimens Containing Integrase Inhibitor Show Good Efficacy and Safety in Treatment-Naive Patients With HIV-1: A Bayesian Analysis

Introduction: The extensive utilisation of antiretroviral therapy has greatly improved the survival rates of those infected with human immunodeficiency virus (HIV). The objective of this study was to compare 3-drug regimens containing non-nucleoside reverse transcriptase inhibitor with 3-drug regimens containing integrase inhibitor (INI) regarding efficacy and safety in treatment-naive HIV-1-infected adults at 48 and 96 weeks, respectively.

Methods: This study was a network meta-analysis using a Bayesian methodology. On January 8, 2020, we searched databases and other sources for randomized controlled trials conducted in treatment-naive HIV-1 adults and compared multiple 3-drug antiretroviral regimens containing INI, efavirenz (EFV), or rilpivirine (RPV). We extracted data on the following outcomes: virologic suppression, CD4⁺ cell recovery, discontinuations, deaths, adverse events, serious adverse events, deaths related to study drugs, and drug-related adverse events. We conducted calculations within a Bayesian framework using R software.

Results: The network contained 15 randomized controlled trials including 9,745 patients. For efficacy outcomes, regimens containing INI, especially dolutegravir (DTG), were generally superior to other regimens. For virologic suppression at 48 weeks, odds ratios (95% credible intervals) were 0.6 (0.43, 0.82) for EFV+ tenofovir disoproxil fumarate (TDF)+emtricitabine (FTC) versus DTG+ abacavir+ lamivudine (3TC) and 0.52 (0.36, 0.75) for EFV+TDF+FTC vs. DTG+TDF+FTC/3TC. For safety outcomes, regimens containing INI tended to be safer relative to regimens without INI. Outcomes associated with death were unsuitable for network meta-analysis due to low event rates.

Conclusion: 3-drug regimens containing INI demonstrate better efficacy and safety than those containing RPV or EFV.

Ibalizumab-uiyk as a bridge therapy for a patient with drug-resistant HIV-1 infection receiving chemotherapy: A case report

WHAT IS KNOWN AND OBJECTIVE

Treatment for diffuse large B-cell lymphoma (DLBCL) in persons with AIDS consists of chemotherapy alongside antiretroviral therapy (ART). To determine optimal HIV treatment, drug-drug interactions, toxic effects and ART resistance must be considered.

CASE DESCRIPTION

A 40-year-old man with drug-resistant HIV and DLBCL initiating chemotherapy which had drug interactions with his ART. During chemotherapy, darunavir/cobicistat was held and ibalizumab-uiyk was started to ensure he was on three active HIV medications.

WHAT IS NEW AND CONCLUSION

Ibalizumab-uiyk has no known drug-drug interactions and may be used as bridge therapy for patients with drug-resistant HIV undergoing chemotherapy.

The potential role of long-acting injectable cabotegravir-rilpivirine in the treatment of HIV in sub-Saharan Africa: a modelling analysis

BACKGROUND

The use of a combination of the integrase inhibitor, cabotegravir, and the non-nucleoside reverse transcriptase inhibitor, rilpivirine, in a long-acting injectable form is being considered as an antiretroviral treatment option for people with HIV in sub-Saharan Africa. We aimed to model the effects of injectable cabotegravir-rilpivirine to help to inform its potential effectiveness and cost-effectiveness under different possible policies for its introduction.

METHODS

We used an existing individual-based model of HIV to predict the effects of introducing monthly injections of cabotegravir-rilpivirine for people with HIV in low-income settings in sub-Saharan Africa. We evaluated policies in the context of 1000 setting scenarios that reflected characteristics of HIV epidemics and programmes in sub-Saharan Africa. We compared three policies for introduction of injectable cabotegravir-rilpivirine with continued use of dolutegravir-based oral regimens for: all individuals on antiretroviral therapy (ART); individuals with a recently measured viral load of more than 1000 copies per mL (signifying poor adherence to oral drugs, and often associated with drug resistance); and individuals with a recently measured viral load of less than 1000 copies per mL (a group with a lower prevalence of pre-existing drug resistance). We also did cost-effectiveness analysis, taking a health system perspective over a 10 year period, with 3% discounting of disability-adjusted life-years (DALYs) and costs. A cost-effectiveness threshold of US$500 per DALY averted was used to establish if a policy was cost-effective.

FINDINGS

In our model, all policies involving the introduction of injectable cabotegravir-rilpivirine were predicted to lead to an increased proportion of people with HIV on ART, increased viral load suppression, and decreased AIDS-related mortality, with lesser benefits in people with a recently measured viral load of less than 1000 copies per mL. Its introduction is also predicted to lead to increases in resistance to integrase inhibitors and non-nucleoside reverse transcriptase inhibitors if introduced in all people with HIV on ART or in those with a recently measured viral load of less than 1000 copies per mL, but to a lesser extent if introduced in people with more than 1000 copies per mL due to concentration of its use in people less adherent to oral therapy. Consistent with the effect on AIDS-related mortality, all approaches to the introduction of injectable cabotegravir-rilpivirine are predicted to avert DALYs. Assuming a cost of $120 per person per year, use of this regimen in people with a recently measured viral load of more than 1000 copies per mL was borderline cost-effective (median cost per DALY averted across setting scenarios $404). The other approaches considered for its use are unlikely to be cost-effective unless the cost per year of injectable cabotegravir-rilpivirine is considerably reduced.

INTERPRETATION

Our modelling suggests that injectable cabotegravir-rilpivirine offers potential benefits; however, to be a cost-effective option, its introduction might need to be carefully targeted to individuals with HIV who might otherwise have suboptimal adherence to ART. As data accumulate from trials and implementation studies, such findings can be incorporated into the model to better inform on the full consequences of policy alternatives.

FUNDING

Bill & Melinda Gates Foundation, including through the HIV Modelling Consortium (OPP1191655).

Once-daily Doravirine for Initial Treatment of Adults Living With Human Immunodeficiency Virus-1: An Integrated Safety Analysis

BACKGROUND

A prespecified integrated safety analysis was conducted for 3 doravirine (DOR) double-blind trials (Phase IIb: P007 [NCT01632345]; Phase III: DRIVE-FORWARD [NCT02275780] and DRIVE-AHEAD [NCT02403674]).

METHODS

DOR (100 mg) arms from these trials were compared with darunavir plus ritonavir (DRV+r) in DRIVE-FORWARD and efavirenz (EFV) in P007 and DRIVE-AHEAD. Background therapies were emtricitabine/tenofovir disoproxil fumarate (FTC/TDF) in P007; abacavir/lamivudine (ABC/3TC) or FTC/TDF in DRIVE-FORWARD; and 3TC/TDF for DOR and FTC/TDF for EFV in DRIVE-AHEAD. The primary endpoint was the proportion of participants discontinuing due to adverse events (AEs) through Week 48.

RESULTS

Discontinuation rates due to AEs were similar for participants on DOR and DRV+r (2.5% vs 3.1%, respectively) and lower for those on DOR than for those on EFV (2.5% vs 6.6%, respectively). Rates of drug-related AEs for DOR, DRV+r, and EFV were 30.9%, 32.1%, and 61.4%, respectively. In an analysis of DOR versus EFV, the treatment difference for discontinuations due to AEs was -3.4%, favoring DOR (95% confidence interval -6.2 to -0.8; P = .012). Fewer participants experienced neuropsychiatric AEs on DOR than on EFV (25.0% vs 55.9%, respectively), and fewer experienced diarrhea on DOR than on DRV+r (12.4% vs 22.5%, respectively). Changes from baseline in most lipid parameters also favored DOR.

CONCLUSIONS

At Week 48, DOR at 100 mg had a favorable safety profile compared with EFV or DRV+r and a favorable tolerability profile compared with EFV.

CLINICAL TRIALS REGISTRATION

NCT01632345; NCT02275780 and NCT02403674.

Demographic and clinical factors associated with immune reconstitution in HIV/HBV co-infected and HIV mono-infected patients: a retrospective cohort study

OBJECTIVES

To describe the clinical characteristics and factors associated with CD4 T-cell count and CD4/CD8 ratio restoration in HIV mono-infected and HIV/HBV co-infected individuals, and to explore liver and renal functional changes in both groups.

METHODS

A retrospective cohort study was performed including 356 HIV/HBV co-infected and 716 HIV mono-infected participants who initiated antiretroviral therapy (ART) during 2013-2017 in Beijing Youan Hospital, China. Demographic and clinical characteristics were compared between the two groups, using χ² and Mann-Whitney non-parametric tests. Bivariate and multivariate Cox regression models were used to test their association.

RESULTS

Baseline HIV viral load and ART regimen were found to be significantly associated with CD4 T-cell restoration among HIV-infected participants, whereas baseline HIV viral load was the only significant factor associated with CD4 T-cell restoration in HIV/HBV co-infected participants. The final model showed that baseline HIV viral load and ART regimen were significantly associated with CD4/CD8 ratio restoration among HIV-infected participants, while baseline HIV viral load was the significant factor. Liver and renal functions were similar at the endpoint (P > 0.05).

CONCLUSIONS

Baseline HIV viral load count was found to be the key factor affecting immune restoration in both HIV and HIV/HBV individuals. Future multi-wave prospective studies are needed to clarify the potential biological mechanism.

Switching protease inhibitors to rilpivirine in HIV-positive individuals with complete viral suppression and without prior HIV drug resistance in a resource-limited setting: a randomized controlled trial

Introduction

Prior to the availability of rilpivirine (RPV), patients who could not tolerate efavirenz and nevirapine (NVP) were treated with protease inhibitor (PI)‐based antiretroviral therapy (ART). Dyslipidaemia and other metabolic complications are commonly associated with PI use. This study aimed to compare the efficacy and adverse events between switching from PI‐based to RPV‐based regimen, versus continuing PI‐based regimens in HIV‐positive individuals with complete viral suppression.

Methods

A randomized controlled trial was conducted in HIV‐positive individuals receiving PI‐based regimens with undetectable HIV RNA and without prior HIV drug resistance. Patients were enrolled between July and December 2017 in a university medical centre in Bangkok, Thailand. They were randomized to switch from PIs to RPV (switch group) or continue ritonavir‐boosted PI (control group). Primary endpoint was the proportion of patients with undetectable HIV RNA at 48 weeks. Changes in CD4 cell counts, lipid profiles and adverse events were also analysed.

Results and discussion

A total of 84 patients were enrolled, 42 in each group. Mean age was 47.7 years and 53.6% were males. At 48 weeks, 95.2% of patients in the switch group and 92.9% of control group had maintained undetectable HIV RNA (difference rate 2.4%; 95% CI, −9.6 to 14.7). Means of CD4 cell counts were 611 and 641 cells/mm³ in switch and control groups respectively (p = 0.632). Mean changes in lipid profiles (switch vs. control groups) were: total cholesterol, −12.5 versus + 12.2 (p = 0.024); LDL, −3.4 versus + 6.2 (p = 0.040); HDL, +1.6 versus + 1.9 (p = 0.887); and triglycerides, −82.6 versus − 24.4 mg/dL (p = 0.031). The mean changes of glucose and eGFR were similar (p > 0.05) between the two groups. The mean change of ALT was significantly greater in switch group (18.2 vs. 4.0 U/L, p = 0.017). One patient in switch group had anorexia and elevated ALT at 14 weeks and completely recovered after RPV discontinuation.

Conclusions

Switching PIs to RPV, in patients with complete viral suppression and without prior HIV drug resistance, sustains viral suppression and yields better lipid profiles. This finding supports its use as switching therapy in patients receiving PI‐based regimens due to intolerance to efavirenz and NVP and previous alternatives limited to PI in resource‐limited settings.

Pediatric Antiretroviral Therapy

Human immunodeficiency virus (HIV) is one of the most serious pediatric infectious diseases, affecting around 3 million children and adolescents worldwide. Lifelong antiretroviral treatment (ART) provides multiple benefits including sustained virologic suppression, restoration and preservation of immune function, decreased morbidity and mortality, and improved quality of life. However, access to ART, particularly among neonates and young infants, continues to be challenging due to limited number of suitable formulations and limited access to pediatric ARV drug. Moreover, children and adolescents living with HIV may experience long-term HIV- and ART-associated comorbidities including cardiovascular, renal, neurological, and metabolic complications. We provide an overview of currently available formulations, dosing, and safety considerations for pediatric antiretroviral drugs by drug classes and according to the three age groups including neonates, children, and adolescents.

Antiretroviral Therapy-Associated Metabolic Complications: Review of the Recent Studies

The extensive utilization of antiretroviral therapy (ART) has successfully improved human immunodeficiency virus (HIV)-associated complications. The incidence of opportunistic infections is decreased by the viral load suppression and the CD4 count promotion. However, metabolic complications, commonly bone demineralization, lipodystrophy, and lactic acidosis, are arising following the adaptation of long-term ART. The events are not drug-specific, but the severity and incidence individually vary depending upon classes of drugs. Such concerning occurrences may lead to discontinuation of current therapy or switching to another regimen with fewer adverse effects. The purpose of this review is to demonstrate the common metabolic abnormalities associated with each class of widely used ART in people living with HIV (PLHIV). Electronic databases such as PubMed, ScienceDirect, Scopus, Google Scholar, SciFinder, and Web of Science were used for the literature search. A better understanding of ART-associated metabolic adverse effects is helpful in various clinical settings so that therapists may optimize treatments in this population.

Durability of different initial regimens in HIV-infected patients starting antiretroviral therapy with CD4+ counts <200 cells/mm3 and HIV-RNA >5 log10 copies/mL

OBJECTIVES

Our aim was to investigate the durability of different initial regimens in patients starting ART with CD4+ counts <200 cells/mm3 and HIV-RNA >5 log10 copies/mL.

METHODS

This was a retrospective study of HIV-infected patients prospectively followed in the ICONA cohort. Those who started ART with boosted protease inhibitors (bPIs), NNRTIs or integrase strand transfer inhibitors (InSTIs), with CD4+ <200 cells/mm3 and HIV-RNA >5 log10 copies/mL, were included. The primary endpoint was treatment failure (TF), a composite endpoint defined as virological failure (VF, first of two consecutive HIV-RNA >50 copies/mL after 6 months of treatment), discontinuation of class of the anchor drug or death. Independent associations were investigated by Poisson regression analysis in a model including age, gender, mode of HIV transmission, CDC stage, HCV and HBV co-infection, pre-treatment HIV-RNA, CD4+ count and CD4+/CD8+ ratio, ongoing opportunistic disease, fibrosis FIB-4 index, estimated glomerular filtration rate, haemoglobin, platelets, neutrophils, calendar year of ART initiation, anchor drug class (treatment group) and nucleos(t)ide backbone.

RESULTS

A total of 1195 patients fulfilled the inclusion criteria: 696 started ART with a bPI, 315 with an InSTI and 184 with an NNRTI. During 2759 person-years of follow up, 642 patients experienced TF. Starting ART with bPIs [adjusted incidence rate ratio (aIRR) (95% CI) 1.62 (1.29-2.03) versus starting with NNRTIs; P < 0.001] and starting ART with InSTIs [aIRR (95% CI) 0.68 (0.48-0.96) versus starting with NNRTIs; P = 0.03] were independently associated with TF.

CONCLUSIONS

In patients starting ART with <200 CD4+ cells/mm3 and >5 log10 HIV-RNA copies/mL, the durability of regimens based on InSTIs was longer than that of NNRTI- and bPI-based regimens.

Drug Interactions with Gender-Affirming Hormone Therapy: Focus on Antiretrovirals and Direct Acting Antivirals

INTRODUCTION

Gender-affirming care may include hormonal therapy to attain desired health outcomes in transgender (trans) individuals. To provide safe, affirming medical care for trans patients, health care providers must identify and manage drug-drug interactions (DDIs) between gender affirming hormonal therapy (GAHT) and other medication therapies.

AREAS COVERED

This review summarizes available data on DDIs between GAHT and antiretrovirals (ARVs) or hepatitis C direct acting antivirals (DAAs). Potential pharmacokinetic and pharmacodynamic DDIs are predicted based on GAHT, ARV, and DAA pharmacology and adverse event profiles. Clinical management strategies are discussed.

EXPERT OPINION

GAHT may be involved in pharmacokinetic and/or pharmacodynamic DDIs. Certain ARV classes (non-nucleoside reverse transcriptase inhibitors, protease inhibitors) may alter GAHT disposition, whereas selected ARVs (unboosted integrase inhibitors, doravirine, or rilpivirine) may have less impact on GAHT. DAAs may interact with GAHT, but the clinical relevance is unclear. ARV- and/or DAA-associated side effects (including depression, cardiovascular disease, hyperlipidemia) are important to consider in the clinical management of trans patients. Clinicians must evaluate potential DDIs and overlapping side effects between ARVs, DAAs and GAHT when providing care for trans patients.

Current and emerging non-nucleoside reverse transcriptase inhibitors (NNRTIs) for HIV-1 treatment

Introduction: Non-nucleoside reverse transcriptase inhibitors (NNRTIs) are essential components of highly active antiretroviral therapy against HIV-1 infections. Here, we provide a comprehensive overview of approved and emerging NNRTIs. Areas covered: This review covers the latest trend of NNRTIs regarding their pharmacodynamics, pharmacokinetics, mechanisms of drug action, drug resistance as well as new applications such as two-drug regimens and long-acting formulations. Expert opinion: Since the first NNRTI, nevirapine, was approved in 1996, antiviral drug discovery led to the approval of seven NNRTIs, including nevirapine, delavirdine (discontinued), etravirine, elsulfavirine, efavirenz, rilpivirine, and doravirine. The latter three compounds with favorable pharmacodynamic profiles and minimal adverse effects are often combined with one integrase inhibitor or two NRTIs in once-daily fixed-dose tablets. NNRTI-anchored regimens have been approved as initial therapies in treatment-naïve patients (efficacy: 72% to 86%) or maintaining therapies in virologically-suppressed patients (efficacy: 91% to 95%). Future development of NNRTIs includes: (i) better resistance and cross-resistance profiles; (ii) reduction of drug burden by optimizing two-drug or three-drug combinations; and (iii) improvement of patient adherence by novel long-acting formulations with weekly or monthly administration. Overall, NNRTIs play an important role in the management of HIV-1 infections, especially in resource-limited countries.

Impact of Human Immunodeficiency Virus Type 1 Minority Variants on the Virus Response to a Rilpivirine-Based First-line Regimen

Background

Minority resistant variants of human immunodeficiency virus type 1 (HIV-1) could influence the virological response to treatment based on nonnucleoside reverse transcriptase inhibitors (NNRTIs). Data on minority rilpivirine-resistant variants are scarce. This study used next-generation sequencing (NGS) to identify patients harboring minority resistant variants to nucleos(t)ide reverse transcriptase inhibitors and NNRTIs and to assess their influence on the virological response (VR).

Methods

All the subjects, 541 HIV-1-infected patients started a first-line regimen containing rilpivirine. VR was defined as a HIV-1 RNA load <50 copies/mL at month 6 with continued suppression at month 12. NGS was performed at baseline (retrospectively) on the 454 GS-FLX platform (Roche).

Results

NGS revealed resistance-associated mutations accounting for 1% to <5% of variants in 17.2% of samples, for 5%-20% in 5.7% of samples, and for >20% in 29% of samples. We identified 43 (8.8%) and 36 (7.4%) patients who harbored rilpivirine-resistant variants with a 1% sensitivity threshold according to the French National Agency for Research on AIDS and Viral Hepatitis and Stanford algorithms, respectively. The VR was 96.9% at month 12. Detection of minority rilpivirine resistant variants was not associated with virological failure (VF). Multivariate analysis indicated that VF at month 12 was associated with a CD4 count <250 cells/µL at baseline, a slower decrease in viral load at month 3, and rilpivirine resistance at baseline using the Stanford algorithm with a 20% threshold.

Conclusions

Minority resistant variants had no impact on the VR of treatment-naive patients to a rilpivirine-based regimen.

Evaluating cabotegravir/rilpivirine long-acting, injectable in the treatment of HIV infection: emerging data and therapeutic potential

Cabotegravir and rilpivirine long-acting injectable antiretroviral therapy for the treatment of HIV-1 infection brings promise of a new mode of delivery and potential solutions to some problems of oral therapy, but also new challenges and unanswered questions. Adding to the increasing body of evidence for newer two-drug combinations, phase II and phase III trial data to date demonstrate cabotegravir and rilpivirine combination injectable therapy to be non-inferior to selected oral triple-therapy alternatives. Most importantly, this therapy is reported to be acceptable to individuals taking the 4-weekly or 8-weekly injections, despite frequent injection-site reactions. Key outstanding questions include management of missed or delayed dosing, drug interactions and management of virological failure, as well as the efficacy of cabotegravir and rilpivirine in all HIV-1 subtypes. We describe clinical evidence to date and efficacy and challenges in selected populations, including women; those with prior virological failure; individuals with a history of difficulty adhering to oral therapy and individuals with co-infections. We await real-world data and longer-term evidence while moving forward to this new era of antiretroviral therapy.

Switching at Low HIV-1 RNA into Fixed Dose Combinations: TDF/FTC/RPV is non-inferior to TDF/FTC/EFV in first-line suppressed patients living with HIV

BACKGROUND

In low- and middle-income countries (LMICs), a substantial unmet need for affordable single-tablet regimen (STR) options remains. Rilpivirine (RPV, TMC278) is formulated in a low-cost STR with tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC).

OBJECTIVES

Switching at Low HIV-1 RNA into Fixed Dose Combinations (SALIF) compared RPV with efavirenz (EFV), both as STRs with TDF and FTC, in maintaining virologic suppression.

METHODS

SALIF was a phase 3b, randomised, open-label, non-inferiority study in virologically suppressed adults (HIV-1 RNA < 50 copies/mL) on non-nucleoside reverse transcriptase inhibitor (NNRTI)-based first-line antiretroviral therapy (ART) in Cameroon, Kenya, Senegal, South Africa, Uganda and Thailand. Patients (N = 426), stratified by NNRTI use, were randomised 1:1 to receive TDF/FTC/RPV (300/200/25 mg qd) or TDF/FTC/EFV (300/200/600 mg qd). Primary endpoint was proportion of patients with virologic suppression (HIV-1 RNA < 400 copies/mL) at week 48 (intent-to-treat, modified Food and Drug Administration Snapshot, 10% non-inferiority margin).

RESULTS

Patients received TDF/FTC/RPV (n = 213) or TDF/FTC/EFV (n = 211). At week 48, virologic suppression was maintained in 200/213 (93.9%) patients in the RPV arm and 203/211 (96.2%) in the EFV arm (difference -2.3%; 95% confidence interval: -6.4, +1.8), demonstrating non-inferiority of TDF/FTC/RPV. One patient in each arm experienced virologic failure without treatment-emergent resistance. Twenty-seven patients discontinued prematurely (8.0% RPV vs. 4.7% EFV), the most frequent reasons being adverse events (3.3% vs. 0.5%, respectively), site closure (1.9% vs. 0.5%), loss to follow-up (0.9% vs. 1.4%) and consent withdrawal (0.9% vs. 1.4%).

CONCLUSION

In adults with suppressed viral load on first-line NNRTI-based ART in LMICs, switching to an STR of TDF/FTC/RPV was non-inferior to TDF/FTC/EFV in maintaining high rates of viral suppression with a comparable tolerability profile.

Two Coselected Distal Mutations in HIV-1 Reverse Transcriptase (RT) Alter Susceptibility to Nonnucleoside RT Inhibitors and Nucleoside Analogs

Although antiretroviral therapy (ART) is highly successful, drug-resistant variants can arise that blunt the efficacy of ART. New inhibitors that are broadly effective against known drug-resistant variants are needed, although such compounds might select for novel resistance mutations that affect the sensitivity of the virus to other compounds. Compound 13 selects for resistance mutations that differ from traditional NNRTI resistance mutations. These mutations cause increased sensitivity to NRTIs, such as AZT.

Two mutations, G112D and M230I, were selected in the reverse transcriptase (RT) of human immunodeficiency virus type 1 (HIV-1) by a novel nonnucleoside reverse transcriptase inhibitor (NNRTI). G112D is located near the HIV-1 polymerase active site; M230I is located near the hydrophobic region where NNRTIs bind. Thus, M230I could directly interfere with NNRTI binding but G112D could not. Biochemical and virological assays were performed to analyze the effects of these mutations individually and in combination. M230I alone caused a reduction in susceptibility to NNRTIs, while G112D alone did not. The G112D/M230I double mutant was less susceptible to NNRTIs than was M230I alone. In contrast, both mutations affected the ability of RT to incorporate nucleoside analogs. We suggest that the mutations interact with each other via the bound nucleic acid substrate; the nucleic acid forms part of the polymerase active site, which is near G112D. The positioning of the nucleic acid is influenced by its interactions with the “primer grip” region and could be influenced by the M230I mutation.

IMPORTANCE Although antiretroviral therapy (ART) is highly successful, drug-resistant variants can arise that blunt the efficacy of ART. New inhibitors that are broadly effective against known drug-resistant variants are needed, although such compounds might select for novel resistance mutations that affect the sensitivity of the virus to other compounds. Compound 13 selects for resistance mutations that differ from traditional NNRTI resistance mutations. These mutations cause increased sensitivity to NRTIs, such as AZT.

Efficacy and improvement of lipid profile after switching to rilpivirine in resource limited setting: real life clinical practice

Background

Long-term success of cART is possible if the regimen is convenient and less-toxic. This study assessed the efficacy and safety of switching from a first-line NNRTI or boosted PI-based regimens to RPV-based regimens among virologically suppressed participants in resource-limited setting (RLS).

Methods

This is a prospective cohort study. Participants with plasma HIV-RNA < 50 copies/mL receiving cART were switched from a PI- or NNRTI-based, to a RPV-based regimen between January 2011 and April 2018. The primary endpoint was the proportion of patients with plasma HIV-1 RNA level < 50 copies/mL after 12 months of RPV. The secondary endpoint was the virological response at 24 months and safety endpoint (change in lipid profiles and kidney function from baseline to 12 months).

Results

A total of 320 participants were enrolled into the study. The rationale for switching to RPV was based on toxicity of the current regimen (57%) or desire to simplify cART (41%). Totally, 177 (55%) and 143 (45%) participants were on NNRTI and boosted PI, respectively, prior to switching to RPV. After 12 months, 298 (93%) participants maintained virological suppression. There were significant improvements in the lipid parameters: TC (− 21 (IQR − 47 to 1) mg/dL; p < 0.001), LDL (− 14 (IQR − 37 to 11) mg/dL; p < 0.001) and TG (− 22 (IQR − 74 to 10) mg/dL; p < 0.001). Also, there was a small but statistically significant decrease in eGFR (− 4.3 (IQR − 12 to 1.1) mL/min per 1.73m2; p < 0.001).

Conclusions

In RLS where integrase inhibitors are not affordable, RPV-based regimens are a good alternative option for PLHIV who cannot tolerate first-line NNRTI or boosted PI regimen, without prior NNRTI/PI resistance.

Trial registration HIV-NAT 006 cohort, clinical trial number: NCT00411983

Adherence to HIV treatment regimens: systematic literature review and meta-analysis

BACKGROUND

Antiretroviral therapy (ART), when taken consistently, reduces morbidity and mortality associated with human immunodeficiency virus and viral transmission. Suboptimal treatment adherence is associated with regimen complexity and high tablet burden. Single-tablet regimens (STRs) provide a complete treatment regimen in a single tablet. This study examined the relationship between STRs (vs multiple-tablet regimens [MTRs]), treatment adherence, and viral suppression.

METHODS

A systematic review was conducted to identify studies investigating at least one of the following: (1) STR/MTR use and adherence; (2) levels of adherence and viral suppression; and (3) STR/MTR use and viral suppression. Meta-analysis was performed to assess the relationship between STR vs MTR use and adherence in observational settings at ≥95% and ≥90% adherence thresholds.

RESULTS

In total, 29 studies were identified across the three objectives; two studies were relevant for all objectives. STRs were associated with higher treatment adherence than MTRs in 10/11 observational studies: a 63% greater likelihood of achieving ≥95% adherence (95% CI=1.52-1.74; P<0.001) and a 43% increase in the likelihood of achieving ≥90% adherence (95% CI=1.21-1.69; P<0.001). Higher adherence rates were associated with higher levels of viral suppression in 13/18 studies. Results were mixed in five studies investigating the association between STR or MTR use and viral suppression.

CONCLUSION

Although the direct effect of STRs vs MTRs on viral suppression remains unclear, this study provided a quantitative estimate of the relationship between STRs and ART adherence, demonstrating that STRs are associated with significantly higher ART adherence levels at 95% and 90% thresholds. Findings from the systematic review showed that improved adherence results in an increased likelihood of achieving viral suppression in observational settings. Future research should utilize similar measures for adherence and evaluate viral suppression to improve assessment of the relationship between pill burden, adherence, and viral suppression.

Prevalence of Human Immunodeficiency Virus-1 Integrase Strand Transfer Inhibitor Resistance in British Columbia, Canada Between 2009 and 2016: A Longitudinal Analysis

Background

Integrase strand transfer inhibitors (INSTIs) are highly efficacious and well tolerated antiretrovirals with fewer adverse side-effects relative to other classes of antiretrovirals. The use of INSTIs raltegravir, elvitegravir, and dolutegravir has increased dramatically over recent years. However, there is limited information about the evolution and prevalence of INSTI resistance mutations in clinical human immunodeficiency virus populations.

Methods

Human immunodeficiency virus-1-positive individuals ≥19 years were included if they received ≥1 dispensed prescription of antiretroviral therapy (ART) in British Columbia between 2009 and 2016 (N = 9358). Physician-ordered drug resistance tests were analyzed and protease inhibitor (PI), reverse-transcriptase inhibitor (RT), and INSTI resistance were defined as having ≥1 sample with a combined, cumulative score ≥30 by Stanford HIV Drug Resistance Algorithm version 7.0.1.

Results

Although most ART-treated individuals were tested for PI and RT resistance, INSTI resistance testing lagged behind the uptake of INSTIs among INSTI-treated individuals (11% in 2009; 34% in 2016). The prevalence of INSTI resistance was relatively low, but it increased from 1 to 7 per 1000 ART-treated individuals between 2009 and 2016 (P < .0001, R² = 0.98). Integrase strand transfer inhibitor resistance mutations increased at integrase codons 66, 97, 140, 148, 155, and 263.

Conclusions

The prevalence of INSTI resistance remains low compared with PI and RT resistance in ART-treated populations but is expanding with increased INSTI use.

Prevalence and Patterns of Antiretroviral Therapy Prescription in the United States

Background:

The use of Antiretroviral Therapy (ART) in HIV-infected persons has proven to be effective in the reduction of risk of disease progression and prevention of HIV transmission.

Objective:

U.S. Antiretroviral Therapy (ART) guidelines specify recommended initial, alternative initial, and not-recommended regimens, but data on ART prescribing practices and real-world effectiveness are sparse.

Methods:

Nationally representative annual cross sectional survey of HIV-infected adults receiving medical care in the United States, 2009-2012 data cycles. Using data from 18,095 participants, we assessed percentages prescribed ART regimens based on medical record documentation and the associations between ART regimens and viral suppression (most recent viral load test <200 copies/ml in past year) and ART-related side effects.

Results:

Among HIV-infected adults receiving medical care in the United States, 91.8% were prescribed ART; median time since ART initiation to interview date was 9.8 years. The percentage prescribed ART was significantly higher in 2012 compared to 2009 (92.7% vs 88.7%; p < 0.001). Of those prescribed ART, 51.6% were prescribed recommended initial regimens, 6.1% alternative initial regimens, 29.0% not-recommended as initial regimens, and 13.4% other regimens. Overall, 79.5% achieved viral suppression and 15.7% reported side effects. Of those prescribed ART and initiated ART in the past year, 80.5% were prescribed recommended initial regimens.

Conclusion:

Among persons prescribed ART, the majority were prescribed recommended initial regimens. Monitoring of ART use should be continued to provide ongoing assessments of ART effectiveness and tolerability in the United States.

Dolutegravir-rilpivirine: first 2-drug regimen for HIV-positive adults

INTRODUCTION

New strategies for HIV treatment are being investigated to reduce drug-exposure, toxicities, and costs. Dolutegravir (DTG) 50 mg/rilpivirine (RPV) 25 mg was approved in November 2017 by FDA and in May 2018 by the European Medicines Agency (EMA). It is indicated as a complete regimen for HIV-1 infected adults with undetectable plasmatic HIV-RNA for at least 6 months on their current HIV treatment combination. Its approval was based on the data of two randomized, multicenter, non-inferiority trials (SWORD-1 and SWORD-2). Areas covered: We reviewed data from literature about DTG and RPV. We mainly focused on the efficacy and on the safety of this new dual therapy. Its impact on renal function, its bone and cardiovascular profile, its reservoir penetration and its role on inflammation were also evaluated. Expert commentary: Dual therapies may be an attractive alternative to standard triple regimens in terms of tolerability and simplicity. Long-term efficacy of DTG and RPV dual regimen need to be confirmed, where only the extensive use of this new treatment and a longer follow-up will give us the answers.

Acute kidney injury in HIV-infected patients: a critical review

Acute kidney injury (AKI) is characterized by a rapid decline of renal function associated with worse outcomes. The purpose of the authors is to perform a critical review of the incidence, risk factors, pathogenesis and outcome of AKI in HIV-infected patients. Human immunodeficiency virus (HIV)-infected patients have an increased risk of developing AKI, to which contribute both HIV-dependent and HIV-independent factors as well as the nephrotoxicity of drugs used. The increased risk of AKI in HIV-infected patients and its negative impact on prognosis highlights the need for identification of patients at risk, creation of prevention strategies and management. HIV-infected patients have an increased risk of developing AKI, to which both HIV-dependent and HIV-independent factors contribute, as well as the nephrotoxicity of drugs used. The increased risk of AKI in HIV-infected patients and its negative impact on prognosis highlight the need for identification of patients at risk, creation of prevention strategies and management.

Comparison of 48-week efficacies of elvitegravir/cobicistat/emtricitabine/tenofovir alafenamide and nucleoside/nucleotide reverse transcriptase inhibitor-sparing regimens: a systematic review and network meta-analysis

OBJECTIVES

To compare nucleoside/nucleotide reverse transcriptase inhibitor (NRTI)-sparing regimens with tenofovir alafenamide (TAF)-based combinations in HIV-1-infected adults, we performed a network meta-analysis (NMA) to provide estimates of relative efficacy for these two regimens.

METHODS

A systematic literature review (SLR) was performed to identify phase 3/4 randomized controlled clinical trials evaluating the efficacy of commonly used combination antiretroviral therapy (cART) including an NRTI backbone or that of commonly used NRTI-sparing regimens. A Bayesian random-effect model was used to compare virological suppression rates at 48 weeks for NRTI-sparing regimens and elvitegravir/cobicistat/emtricitabine/TAF (E/C/F/TAF).

RESULTS

Twenty-three studies in treatment-naïve patients identified by the SLR were included in the NMA, including four studies assessing NRTI-sparing regimens. In treatment-naïve patients, the probability of achieving virological suppression at 48 weeks was between 40% and 60% higher with E/C/F/TAF than with NRTI-sparing strategies. The credible interval vs. darunavir/ritonavir (DVR/r) + raltegravir (RAL) and LPV/r monotherapy did not include 1. In the subgroup of naïve patients with viral load < 100 000 HIV-1 RNA copies/mL, a credible difference was found between NRTI-sparing treatments and E/C/F/TAF. Studies in treatment-experienced patients were too heterogeneous to allow for an NMA.

CONCLUSIONS

The NMA results suggest that E/C/F/TAF represents a more effective option than NRTI-sparing regimens in terms of 48-week efficacy in treatment-naïve patients. Furthermore, TAF pharmacological properties, as well as tolerability results in clinical studies, suggest a safety profile similar to that of NRTI-sparing regimens. Thus, the E/C/F/TAF combination might represent a more appropriate option than NRTI-sparing regimens for initiation of antiretroviral therapy in treatment-naïve HIV-infected patients.

First-line antiretroviral therapy with efavirenz plus tenofovir disiproxil fumarate/emtricitabine or rilpivirine plus tenofovir disiproxil fumarate/emtricitabine: a durability comparison

OBJECTIVES

The aim of this study was to compare the durabilities of efavirenz (EFV) and rilpivirine (RPV) in combination with tenofovir/emtricitabine (TDF/FTC) in first-line regimens.

METHODS

A multicentre prospective and observational study was carried out. We included all patients participating in the Italian Cohort Naive Antiretrovirals (ICONA) Foundation Study who started first-line combination antiretroviral therapy (cART) with TDF/FTC in combination with RPV or EFV, with a baseline viral load < 100 000 HIV-1 RNA copies/mL. Survival analyses using Kaplan-Meier (KM) curves and Cox regression with time-fixed covariates at baseline were employed.

RESULTS

Overall, 1490 ART-naïve patients were included in the study, of whom 704 were initiating their first cART with EFV and 786 with RPV. Patients treated with EFV, compared with those on RPV, were older [median 36 (interquartile range (IQR) 30-43) years vs. 33 (IQR 27-39) years, respectively; P < 0.001], were more frequently at Centers for Disease Control and Prevention (CDC) stage C (3.1% vs. 1.4%, respectively; P = 0.024), and had a lower median baseline CD4 count [340 (IQR 257-421) cells/μL vs. 447 (IQR 347-580) cells/μL, respectively; P < 0.001] and a higher median viral load [4.38 (IQR 3.92-4.74) log10 copies/mL vs. 4.23 (IQR 3.81-4.59) log10 copies/mL, respectively], (P = 0.004). A total of 343 patients discontinued at least one drug of those included in the first cART regimen, more often EFV (26%) than RPV (13%), by 2 years (P < 0.0001). After adjustment, patients treated with EFV were more likely to discontinue at least one drug for any cause [relative hazard (RH) 4.09; 95% confidence interval (CI) 2.89-5.80], for toxicity (RH 2.23; 95% CI 1.05-4.73) for intolerance (RH 5.17; 95% CI 2.66-10.07) and for proactive switch (RH 10.96; 95% CI 3.17-37.87) than those starting RPV.

CONCLUSIONS

In our nonrandomized comparison, RPV was better tolerated, less toxic and showed longer durability than EFV, without a significant difference in rates of discontinuation because of failures.

Novel Antiretroviral Drugs in Patients with Renal Impairment: Clinical and Pharmacokinetic Considerations

Highly active antiretroviral therapy (HAART) has dramatically increased the survival of HIV-infected patients from Western countries reducing the incidence of opportunistic infections and AIDS-related malignancies, and improving the patients' quality of life compared with the pre-HAART era. HIV is thus now considered in the West as a chronic disease, with the majority of HIV-infected patients successfully reaching an optimal immune and virological outcome a few months after starting HAART. However, this switch from acute to chronic disease has been accompanied by an increased incidence of chronic kidney disease (CKD), reported in up to 60% of HIV-infected patients. Tenofovir disoproxil fumarate (TDF) is considered to play a significant role in the development of CKD in these patients. It has been proposed that tenofovir alafenamide (TAF), a prodrug formulation able to providing lower systemic and renal drug exposure, could potentially contribute to reduce the development of CKD in HAART-treated patients. On the other hand, the pharmacokinetics of some components of HAART can be significantly altered in HIV-infected patients developing CKD. TDF- or TAF-based antiretroviral regimens should be avoided in patients with a creatinine clearance of less than 50 or 30 mL/min, respectively. This review focuses on the pharmacokinetic changes of novel antiretroviral drugs in HIV-infected patients with renal impairment or requiring renal replacement therapy, and provides some suggestions on how to change drug doses in these clinical settings.

Renal effects of non-tenofovir antiretroviral therapy in patients living with HIV

A review of literature published regarding non-tenofovir antiretroviral agents causing renal adverse effects was conducted. The literature involving renal adverse effects and antiretroviral therapy is most robust with protease inhibitors, specifically atazanavir and indinavir, and includes reports of crystalluria, leukocyturia, nephritis, nephrolithiasis, nephropathy and urolithiasis. Several case reports describe potential nephropathy (including Fanconi syndrome) secondary to administration of abacavir, didanosine, lamivudine and stavudine. Case reports documented renal events such as acute renal failure, nephritis, proteinuria and renal stones with efavirenz administration. Regarding rilpivirine, a small increase of serum creatinine levels (SCr) was found in clinical trials; however, the clinical significance and impact on actual renal function is unknown. The integrase strand transfer inhibitors and enfuvirtide have a relatively safe renal profile, although studies have shown dolutegravir and raltegravir cause mild elevations in SCr without an impact on actual renal function. This is similar to the reaction observed with cobicistat, the pharmacokinetic enhancer frequently given with elvitegravir.

Nanotechnologies for early diagnosis, in situ disease monitoring, and prevention

Nanotechnology is an enabling technology with great potential for applications in stem cell research and regenerative medicine. Fluorescent nanodiamond (FND), an inherently biocompatible and nontoxic nanoparticle, is well suited for such applications. We had developed a prospective isolation method using CD157, CD45, and CD54 to obtain lung stem cells. Labeling of CD45⁻CD54⁺CD157⁺ cells with FNDs did not eliminate their abilities for self-renewal and differentiation. The FND labeling in combination with cell sorting, fluorescence lifetime imaging microscopy, and immunostaining identified transplanted stem cells allowed tracking of their engraftment and regenerative capabilities with single-cell resolution. Time-gated fluorescence (TGF) imaging in mouse tissue sections indicated that they reside preferentially at the bronchoalveolar junctions of lungs, especially in naphthalene-injured mice. Our results presented in Subchapter 1.1 demonstrate not only the remarkable homing capacity and regenerative potential of the isolated stem cells, but also the ability of finding rare lung stem cells in vivo using FNDs.

The topical use of antiretroviral-based microbicides, namely of a dapivirine ring, has been recently shown to partially prevent transmission of HIV through the vaginal route. Among different formulation approaches, nanotechnology tools and principles have been used for the development of tentative vaginal and rectal microbicide products. Subchapter 1.2 provides an overview of antiretroviral drug nanocarriers as novel microbicide candidates and discusses recent and relevant research on the topic. Furthermore, advances in developing vaginal delivery platforms for the administration of promising antiretroviral drug nanocarriers are reviewed. Although mostly dedicated to the discussion of nanosystems for vaginal use, the development of rectal nanomicrobicides is also addressed.

Infectious diseases are currently responsible for over 8 million deaths per year. Efficient treatments require accurate recognition of pathogens at low concentrations, which in the case of blood infection (septicemia) can go as low as 1 mL^–1. Detecting and quantifying bacteria at such low concentrations is challenging and typically demands cultures of large samples of blood (∼1 mL) extending over 24–72 h. This delay seriously compromises the health of patients and is largely responsible for the death toll of bacterial infections. Recent advances in nanoscience, spectroscopy, plasmonics, and microfluidics allow for the development of optical devices capable of monitoring minute amounts of analytes in liquid samples. In Subchapter 1.3 we critically discuss these recent developments that will, in the future, enable the multiplex identification and quantification of microorganisms directly on their biological matrix with unprecedented speed, low cost, and sensitivity.

Radiolabeled nanoparticles (NPs) are finding an increasing interest in a broad range of biomedical applications. They may be used to detect and characterize diseases, to deliver relevant therapeutics, and to study the pharmacokinetic/pharmacodynamic parameters of nanomaterials. The use of radiotracer techniques in the research of novel NPs offers many advantages, but there are still some limitations. The binding of radionuclides to NPs has to be irreversible to prevent their escape to other tissues or organs. Due to the short half-lives of radionuclides, the manufacturing process is time limited and difficult, and there is also a risk of contamination. Subchapter 1.4 presents the main selection criteria for radionuclides and applicable radiolabeling procedures used for the radiolabeling of various NPs. Also, an overview of different types of NPs that have so far been labeled with radionuclides is presented.

Dolutegravir plus rilpivirine dual therapy in treating HIV-1 infection

INTRODUCTION

The HIV-infected population is aging and comorbidities and polypharmacological regimens are increasing. To reduce toxicity and drug burden researchers are evaluating the efficacy, safety and durability of dual therapies as a switch option in subjects who have achieved stable virologic suppression. Initially effective dual combinations relied on protease inhibitors but when dolutegravir, the first integrase inhibitor to display a high genetic barrier, became commercially available, many physicians began to use it in a variety of dual regimens, generating several observational cohorts. Areas covered: This review covers the most recent data from observational cohorts and randomized clinical trials concerning the switch to the dual combination of dolutegravir plus rilpivirine and the reasons that lead to consider this option. Also, viral failures, due to poor adherence or to other factors, and drug resistance are investigated. Articles which are searchable on MEDLINE/PubMed and from the main national/international congresses in the field of HIV therapy are reviewed. Expert opinion: The observation period for this regimen is getting longer and data showing its efficacy in maintaining HIV-1 RNA < 50 copies/mL are now consolidated. Metabolic data suggest some benefit in the lipid profile, improvement in bone mineral density and reduced bone reabsorption.

Key Factors Influencing the Emergence of Human Immunodeficiency Virus Drug Resistance in Low- and Middle-Income Countries

The emergence and spread of human immunodeficiency virus (HIV) drug resistance from antiretroviral roll-out programs remain a threat to long-term control of the HIV-AIDS epidemic in low- and middle-income countries (LMICs). The patterns of drug resistance and factors driving emergence of resistance are complex and multifactorial. The key drivers of drug resistance in LMICs are reviewed here, and recommendations are made to limit their influence on antiretroviral therapy efficacy.

Moving forward with treatment options for HIV-infected children

INTRODUCTION

Current international guidelines recommend to treat all HIV-1 infected patients regardless of CD4 cell count. Despite the remarkable worldwide progress for universal access to antiretroviral during the last decade, the pediatric population remains fragile due to lack of randomized studies, inappropriate antiretroviral formulations, adherence difficulties, drug toxicity and development of resistance.

AREAS COVERED

This review summarizes the latest recommendations and advances for the treatment of HIV-infected children and highlights the potential complications of a lifelong antiretroviral treatment initiated early in life.

EXPERT OPINION

International guidelines recommend to start combination antiretroviral therapy (cART) as fast as possible in all children diagnosed with HIV-1. The principal goal is to improve survival and reduce mortality as well as rapidly decrease HIV reservoirs. This remains a challenge in resource-limited settings were diagnostic tools and treatment access may be limited. Different new strategies are in the pipeline such as immunotherapy in combination with very early cART initiation to seek remission or functional cure. For the time being and awaiting for long term remission or cure, there is a need for further pharmacokinetics studies, more pediatric formulations with improved palatability and implementation of randomized trials for the newer antiretroviral drugs.

MDR1 and BCRP Transporter-Mediated Drug-Drug Interaction between Rilpivirine and Abacavir and Effect on Intestinal Absorption

Rilpivirine (TMC278) is a highly potent nonnucleoside reverse transcriptase inhibitor (NNRTI) representing an effective component of combination antiretroviral therapy (cART) in the treatment of HIV-positive patients. Many antiretroviral drugs commonly used in cART are substrates of ATP-binding cassette (ABC) and/or solute carrier (SLC) drug transporters and, therefore, are prone to pharmacokinetic drug-drug interactions (DDIs). The aim of our study was to evaluate rilpivirine interactions with abacavir and lamivudine on selected ABC and SLC transporters in vitro and assess its importance for pharmacokinetics in vivo Using accumulation assays in MDCK cells overexpressing selected ABC or SLC drug transporters, we revealed rilpivirine as a potent inhibitor of MDR1 and BCRP, but not MRP2, OCT1, OCT2, or MATE1. Subsequent transport experiments across monolayers of MDCKII-MDR1, MDCKII-BCRP, and Caco-2 cells demonstrated that rilpivirine inhibits MDR1- and BCRP-mediated efflux of abacavir and increases its transmembrane transport. In vivo experiments in male Wistar rats confirmed inhibition of MDR1/BCRP in the small intestine, leading to a significant increase in oral bioavailability of abacavir. In conclusion, rilpivirine inhibits MDR1 and BCRP transporters and may affect pharmacokinetic behavior of concomitantly administered substrates of these transporters, such as abacavir.

Pharmacokinetic drug evaluation of dolutegravir plus rilpivirine for the treatment of HIV

INTRODUCTION

The search for simple, potent, metabolic-friendly and nucleoside/nucleotide sparing antiretroviral regimens has led clinical investigators to move steps towards dual therapies. Among these the association of rilpivirine and dolutegravir is emerging as a twin randomized clinical trial (SWORD1&2) and at least three observational cohort describe it as a safe and highly effective regimen for switch from other therapies Areas covered: We review the evidence supporting the use of dolutegravir plus rilpivirine for the treatment of HIV in virologically suppressed patients taking other antiretroviral regimens. The reasons for the switch in clinical practice may range from simplification to tolerability/toxicity issues, to the prevention of future metabolic damage, to predicted drug-drug interactions when treatment of HCV co-infection is planned. Articles searchable on MEDLINE/PubMed and from the main international congresses in the field of HIV therapy were reviewed to provide context for use of dolutegravir plus rilpivirine Expert opinion: This treatment is highly effective in maintaining HIV-1 RNA <50 copies/mL. Although the studies up to date requested patient to switch to drugs they had no experience of, a predictable 'radical change' effect did not impact negatively on the results. Further data from these studies may help elucidate the possible advantage in terms of safety and metabolic effect in the next few months.

3-Year efficacy and durability of simplification to single tablet regimens: a comparison between co-formulated efavirenz/emtricitabine/tenofovir and rilpivirine/emtricitabine/tenofovir

BACKGROUND

Few data are available about efficacy and durability of simplification from multi-tablet antiretroviral regimens to co-formulated efavirenz (EFV)/emtricitabine (FTC)/tenofovir (TDF) versus rilpivirine (RPV)/FTC/TDF in virologically suppressed HIV-1-infected patients.

METHODS

We retrospectively analysed HIV-infected patients with HIV RNA <50 copies/ml switching to co-formulated EFV/FTC/TDF or RPV/FTC/TDF at five Italian centres. Patients were followed from time of switch until regimen discontinuation or a maximum of 3-years follow-up. Time to treatment discontinuation (TD) and virological failure (VF; defined as two consecutive HIV RNA >50 copies/ml or a single determination >1,000 copies/ml) and their predictors were investigated.

RESULTS

1,560 patients were reviewed of which 1,097 (70%) switched to EFV/FTC/TDF and 463 (30%) to RPV/FTC/TDF. During follow-up, VF and TD occurred in 44 (4%) and 242 (22%) patients in EFV/FTC/TDF and in 29 (6%) and 50 (11%) patients in RPV/FTC/TDF, respectively. The 3-year estimated probability of remaining free from VF was 96.2% with EFV/FTC/TDF versus 92.7% with RPV/FTC/TDF (P=0.003). At multivariate analysis, regimen type (EFV/FTC/TDF versus RPV/FTC/TDF aHR 0.24; P=0.004) and time of virological suppression (aHR 0.85; P=0.048) were the only independent predictors of VF. The estimated 3-year probability of remaining free from TD was 77.4% with EFV/FTC/TDF versus 88.4% with RPV/FTC/TDF (P=0.001). Predictors of TD were female sex, switching from PI-based regimens, older age, shorter time of virological suppression and regimen type (EFV/FTC/TDF versus RPV/FTC/TDF aHR 2.48; P<0.001). RPV/FTC/TDF showed a safer lipid profile and a greater increase in creatinine.

CONCLUSIONS

Both regimens showed good safety and efficacy in this real-life setting, although switch to RPV/FTC/TDF seemed better tolerated while EFV/FTC/TDF was associated with a lower probability of VF.

Adult antiretroviral therapy guidelines 2017

These guidelines are intended as an update to those published in the Southern African Journal of HIV Medicine in 2014 and the update on when to initiate antiretroviral therapy in 2015. Since the release of the previous guidelines, the scale-up of antiretroviral therapy (ART) in southern Africa has continued. New antiretroviral drugs have become available with improved efficacy, safety and robustness. The guidelines are intended for countries in the southern African region, which vary between lower and middle income.

Novel approaches to HIV therapy

There are approximately 35 million people infected by human immunodeficiency virus (HIV), with an estimated 2 million incident infections annually across the globe. While HIV infection was initially associated with high rates of morbidity and mortality, advances in therapy have transformed it into a chronic and manageable disease. In addition, there is very strong evidence that those on antiretroviral therapy are much less likely to transmit infection to their partners. The success rates for maintaining viral suppression in treated patients has dramatically increased owing to the development of agents that are potent and well tolerated and can often be co-formulated into single pills for simplification. This review will outline advances in treatment over the last several years as well as new strategies that may shift the existing treatment paradigm in the near future.

A European multicientre study on the comparison of HIV-1 viral loads between VERIS HIV-1 Assay and Roche COBAS® TAQMAN® HIV-1 test, Abbott RealTime HIV-1 Assay, and Siemens VERSANT HIV-1 Assay

BACKGROUND

Viral load monitoring is essential for patients under treatment for HIV. Beckman Coulter has developed the VERIS HIV-1 Assay for use on the novel, automated DxN VERIS Molecular Diagnostics System.^¥ OBJECTIVES: Evaluation of the clinical performance of the new quantitative VERIS HIV-1 Assay at multiple EU laboratories.

STUDY DESIGN

Method comparison with the VERIS HIV-1 Assay was performed with 415 specimens at 5 sites tested with COBAS^® AmpliPrep/COBAS^® TaqMan^® HIV-1 Test, v2.0, 169 specimens at 3 sites tested with RealTime HIV-1 Assay, and 202 specimens from 2 sites tested with VERSANT HIV-1 Assay. Patient monitoring sample results from 4 sites were also compared.

RESULTS

Bland-Altman analysis showed the average bias between VERIS HIV-1 Assay and COBAS HIV-1 Test, RealTime HIV-1 Assay, and VERSANT HIV-1 Assay to be 0.28, 0.39, and 0.61 log₁₀ cp/mL, respectively. Bias at low end levels below 1000cp/mL showed predicted bias to be <0.3 log₁₀ cp/mL for VERIS HIV-1 Assay versus COBAS HIV-1 Test and RealTime HIV-1 Assay, and <0.5 log₁₀cp/mL versus VERSANT HIV-1 Assay. Analysis on 174 specimens tested with the 0.175mL volume VERIS HIV-1 Assay and COBAS HIV-1 Test showed average bias of 0.39 log₁₀cp/mL. Patient monitoring results using VERIS HIV-1 Assay demonstrated similar viral load trends over time to all comparators.

CONCLUSIONS

The VERIS HIV-1 Assay for use on the DxN VERIS System demonstrated comparable clinical performance to COBAS^® HIV-1 Test, RealTime HIV-1 Assay, and VERSANT HIV-1 Assay.

Factors associated with pre-treatment HIV RNA: application for the use of abacavir and rilpivirine as the first-line regimen for HIV-infected patients in resource-limited settings

Background

Abacavir and rilpivirine are alternative antiretroviral drugs for treatment-naïve HIV-infected patients. However, both drugs are only recommended for the patients who have pre-treatment HIV RNA <100,000 copies/mL. In resource-limited settings, pre-treatment HIV RNA is not routinely performed and not widely available. The aims of this study are to determine factors associated with pre-treatment HIV RNA <100,000 copies/mL and to construct a model to predict this outcome.

Methods

HIV-infected adults enrolled in the TREAT Asia HIV Observational Database were eligible if they had an HIV RNA measurement documented at the time of ART initiation. The dataset was randomly split into a derivation data set (75% of patients) and a validation data set (25%). Factors associated with pre-treatment HIV RNA <100,000 copies/mL were evaluated by logistic regression adjusted for study site. A prediction model and prediction scores were created.

Results

A total of 2592 patients were enrolled for the analysis. Median [interquartile range (IQR)] age was 35.8 (29.9–42.5) years; CD4 count was 147 (50–248) cells/mm³; and pre-treatment HIV RNA was 100,000 (34,045–301,075) copies/mL. Factors associated with pre-treatment HIV RNA <100,000 copies/mL were age <30 years [OR 1.40 vs. 41–50 years; 95% confidence interval (CI) 1.10–1.80, p = 0.01], body mass index >30 kg/m² (OR 2.4 vs. <18.5 kg/m²; 95% CI 1.1–5.1, p = 0.02), anemia (OR 1.70; 95% CI 1.40–2.10, p < 0.01), CD4 count >350 cells/mm³ (OR 3.9 vs. <100 cells/mm³; 95% CI 2.0–4.1, p < 0.01), total lymphocyte count >2000 cells/mm³ (OR 1.7 vs. <1000 cells/mm³; 95% CI 1.3–2.3, p < 0.01), and no prior AIDS-defining illness (OR 1.8; 95% CI 1.5–2.3, p < 0.01). Receiver-operator characteristic (ROC) analysis yielded area under the curve of 0.70 (95% CI 0.67–0.72) among derivation patients and 0.69 (95% CI 0.65–0.74) among validation patients. A cut off score >25 yielded the sensitivity of 46.7%, specificity of 79.1%, positive predictive value of 67.7%, and negative predictive value of 61.2% for prediction of pre-treatment HIV RNA <100,000 copies/mL among derivation patients.

Conclusion

A model prediction for pre-treatment HIV RNA <100,000 copies/mL produced an area under the ROC curve of 0.70. A larger sample size for prediction model development as well as for model validation is warranted.

Multicenter study of skin rashes and hepatotoxicity in antiretroviral-naïve HIV-positive patients receiving non-nucleoside reverse-transcriptase inhibitor plus nucleoside reverse-transcriptase inhibitors in Taiwan

OBJECTIVES

Two nucleos(t)ide reverse-transcriptase inhibitors (NRTIs) plus 1 non-NRTI (nNRTI) remain the preferred or alternative combination antiretroviral therapy (cART) for antiretroviral-naive HIV-positive patients in Taiwan. The three most commonly used nNRTIs are nevirapine (NVP), efavirenz (EFV) and rilpivirine (RPV). This study aimed to determine the incidences of hepatotoxicity and skin rashes within 4 weeks of initiation of cART containing 1 nNRTI plus 2 NRTIs.

METHODS

Between June, 2012 and November, 2015, all antiretroviral-naive HIV-positive adult patients initiating nNRTI-containing cART at 8 designated hospitals for HIV care were included in this retrospective observational study. According to the national HIV treatment guidelines, patients were assessed at baseline, 2 and 4 weeks of cART initiation, and subsequently every 8 to 12 weeks. Plasma HIV RNA load, CD4 cell count and aminotransferases were determined. The toxicity grading scale of the Division of AIDS (DAIDS) 2014 was used for reporting clinical and laboratory adverse events.

RESULTS

During the 3.5-year study period, 2,341 patients initiated nNRTI-containing cART: NVP in 629 patients, EFV 1,363 patients, and RPV 349 patients. Rash of any grade occurred in 14.1% (n = 331) of the patients. In multiple logistic regression analysis, baseline CD4 cell counts (per 100-cell/μl increase, adjusted odds ratio [AOR], 1.125; 95% confidence interval [95% CI], 1.031-1.228) and use of NVP (AOR, 2.443; 95% CI, 1.816-3.286) (compared with efavirenz) were independently associated with the development of skin rashes. Among the 1,455 patients (62.2%) with aminotransferase data both at baseline and week 4, 72 (4.9%) developed grade 2 or greater hepatotoxicity. In multiple logistic regression analysis, presence of antibody for hepatitis C virus (HCV) (AOR, 2.865; 95% CI, 1.439-5.704) or hepatitis B surface antigen (AOR, 2.397; 95% CI, 1.150-4.997), and development of skin rashes (AOR, 2.811; 95% CI, 1.051-7.521) were independently associated with the development of hepatotoxicity.

CONCLUSIONS

The baseline CD4 cell counts and use of NVP were associated with increased risk of skin rashes, while hepatotoxicity was independently associated with HCV or hepatitis B virus coinfection, and development of skin rashes in antiretroviral-naïve HIV-positive Taiwanese patients within 4 weeks of initiation of nNRTI-containing regimens.

Population Pharmacokinetics and Pharmacogenetics Analysis of Rilpivirine in HIV-1-Infected Individuals

Rilpivirine (RPV), the latest nonnucleoside reverse transcriptase inhibitor active against HIV-1, is prescribed in a standard dosage of 25 mg once a day in combination with emtricitabine (FTC) and tenofovir disoproxil fumarate (TDF). The aim of this observational study was to characterize the RPV pharmacokinetic profile, to quantify interpatient variability, and to identify potential factors that could influence drug exposure. RPV concentration data were collected from HIV-infected patients as part of routine therapeutic drug monitoring performed in our center (Laboratory of Clinical Pharmacology). A population pharmacokinetic analysis was performed with NONMEM by comparing various structural models. The influence of demographic and clinical covariates, as well as frequent genetic polymorphisms in 5 genes (CYP3A4*22, CYP3A5*3, CYP2C19*2, CYP2C19*17, UGT1A1*28, and UGT1A4*2), on RPV elimination was explored. A total of 325 plasma concentration measurements were obtained from 249 HIV-positive patients. Plasma concentrations ranged from 12 to 255 ng/ml. A one-compartment model with zero-order absorption best characterized RPV pharmacokinetics. The average RPV clearance (CL) was 11.7 liters/h, the average volume of distribution was 401 liters, and the mean absorption time was 4 h. The interinterindividual variability (IIV) for CL was estimated to be 33%. None of the available demographic or genetic covariates showed any influence on RPV pharmacokinetics, but 29% of the patients were predicted to present minimal concentrations below the recently identified target cutoff value of 50 ng/ml. The variability in RPV pharmacokinetics appears to be lower than that for most other antiretroviral drugs. However, under the standard regimen of 25 mg daily, a significant number of patients might be underdosed. It remains to be investigated whether the underexposure has an impact on the development of resistance while patients are on maintenance therapy.