Rilpivirine versus efavirenz with tenofovir and emtricitabine in treatment-naive adults infected with HIV-1 (ECHO): a phase 3 randomised double-blind active-controlled trial

Metabolic and body composition effects of newer antiretrovirals in HIV-infected patients

In the absence of a cure, HIV-infected patients are being successfully treated with antiretroviral therapies (ART) and living longer. Indeed, an increasing number of HIV-infected patients are living beyond the age of 50 years, and in that regard, the use of ART has transformed HIV into a chronic medical condition. As more HIV-infected patients are virologically controlled and living longer, the trajectory of disease morbidity has shifted, however, primarily from opportunistic infections and immune dysfunction to metabolic complications. Evidence suggests that HIV-infected patients acquire significant metabolic risks, including lipodystrophic changes, subclinical atherosclerosis, and insulin resistance. The etiology of these metabolic complications specifically in HIV-infected patients is not entirely clear but may be related to a complex interaction between long-term consequences of infection and HIV itself, chronic use of antiretrovirals, and underlying inflammatory processes. Previous classes of ART, such as protease inhibitors (PIs) and reverse transcriptase inhibitors, have been implicated in altering fat redistribution and lipid and glucose homeostasis. Advances in drug development have introduced newer ART with strategies to target novel mechanisms of action and improve patient adherence with multi-class drug combinations. In this review, we will focus on these newer classes of ART, including selected entry inhibitors, integrase inhibitors, and multi-class drug combinations, and two newer PIs, and the potential of these newer agents to cause metabolic complications in HIV-infected patients. Taken together, further reduction of morbidity in HIV-infected patients will require increasing awareness of the deleterious metabolic complications of ART with subsequent management to mitigate these risks.

HIV-infected women in Europe: gender-specific needs and challenges

In collaboration with the Strong, HIV positive, Empowered Women (SHE) programme, an industry-funded initiative aimed at improving the quality of life of HIV-positive women, Antiviral Therapy has taken the excellent step to dedicate a Supplement Issue addressing the needs and challenges related to the care of women living in Europe. Included articles present the multiple facets of gender-specific issues and research gaps, ranging from HIV testing strategies to antiretroviral combination therapy, including long-term challenges associated with chronic HIV infection.

Lipid levels and changes in body fat distribution in treatment-naive, HIV-1-Infected adults treated with rilpivirine or Efavirenz for 96 weeks in the ECHO and THRIVE trials

BACKGROUND

Pooled ECHO/THRIVE lipid and body fat data are presented from the ECHO (Efficacy Comparison in Treatment-Naïve, HIV-Infected Subjects of TMC278 and Efavirenz) and THRIVE (TMC278 Against HIV, in a Once-Daily Regimen Versus Efavirenz) trials.

METHODS

We assessed the 96-week effects on lipids, adverse events (AEs), and body fat distribution (dual-energy x-ray absorptiometry) of rilpivirine (RPV) and EFV plus 2 nucleoside/nucleotide reverse transcriptase inhibitors (N[t]RTIs) in treatment-naive adults infected with human immunodeficiency virus type 1 (HIV-1).

RESULTS

Rilpivirine produced minimal changes in total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides. Compared with RPV, EFV significantly (P < .001) increased lipid levels. Decreases in the TC/HDL-C ratio were similar with RPV and EFV. Background N[t]RTI affected RPV-induced lipid changes; all levels increased with zidovudine/lamivudine (3TC) and abacavir/3TC (except triglycerides, which were unchanged). With emtricitabine/tenofovir, levels of HDL-C were increased, TC and LDL-C were unchanged, and triglycerides were decreased. With EFV, lipid levels increased in each N[t]RTI subgroup (except triglycerides were unchanged with abacavir/3TC). Fewer (P < .001) RPV-treated patients than EFV-treated patients had TC, LDL-C, and triglyceride levels above National Cholesterol Education Program cutoffs. More RPV- than EFV-treated patients had HDL-C values below these cutoffs (P = .02). Dyslipidemia AEs were less common with RPV than with EFV. Similar proportions of patients had a ≥10% decrease in limb fat (16% with RPV and 17% with EFV). Limb fat was significantly (P < .001) increased to a similar extent (by 12% with RPV and 11% with EFV). At week 96, patients receiving zidovudine/3TC had lost limb fat, and those receiving emtricitabine/tenofovir had gained it.

CONCLUSIONS

Over the course of 96 weeks, RPV-based therapy was associated with lower increases in lipid parameters and fewer dyslipidemia AEs than EFV-based treatment. Body fat distribution changes were similar between treatments. The N[t]RTI regimen affected lipid and body fat distribution changes.

HIV-associated lipodystrophy: impact of antiretroviral therapy

In the late 1990s, reports of unusual changes in body fat distribution named 'lipodystrophy' (LD) began to appear in HIV patients mitigating the enormous enthusiasm about improvement of survival and quality of life provided by the combinations of antiretroviral (ARV) drug classes, the so-called highly active antiretroviral therapy (HAART), which had just become available at that time. The objective of this paper is to critically review the literature on LD and to discuss the impact of newer ARV agents, namely atazanavir, darunavir and raltegravir, as well as strategies of the late HAART era, including single-tablet regimens and nucleoside-sparing regimens. Studies in which LD was measured by dual-energy x-ray absorptiometry or by abdominal computed tomography or magnetic resonance imaging scan only, were included. We were unable to identify studies depicting a negative impact of drugs or ARV regimens on limb fat loss. On the contrary, a few studies identified a negative impact of atazanavir/ritonavir or darunavir/ritonavir on trunk fat increase. It should be noted that this anthropometric measure is a poor instrument since it cannot distinguish between subcutaneous and visceral fat. We conclude that presumably the body fat changes currently observed in HIV-infected patients is the net result of competing phenomena: on one side the natural history of lipohypertrophy as a result of HIV and HAART impact, and on the other side the physiological body fat changes observed in the aging population.

Validation of a self-administered instrument to measure adherence to anticholinergic drugs in women with overactive bladder

AIM

To validate a self-administered instrument, the Medication Adherence Self-Report Inventory (MASRI) for measuring adherence to anti-cholinergic medication for overactive bladder (OAB).

METHODS

Prospective study in 131 women with OAB treated with fesoterodine. Adherence was measured at 8 and 12 weeks using an interviewer administered brief medication questionnaire (BMQ) that assesses barriers to adherence (criterion standard), the MASRI, and pill count. Construct, concurrent and discriminant validity of the MASRI was assessed. We hypothesized that women who were non-adherent as measured by the MASRI would be more likely to have a belief barrier than women who were adherent to medication.

RESULTS

Women diagnosed as non-adherent by the MASRI were more likely to report a belief barrier to taking medication as compared to adherent women at 8 weeks (80% vs. 38%, P < 0.001) and at 12 weeks (70% vs. 40%, P = 0.003). Significant correlations were noted between adherence rates measured by the MASRI and the BMQ at 8 weeks (r = 0.87, P < 0.001) and 12 weeks (r = 0.90, P < 0.001). Moderate correlation was noted between the adherence rate as measured by the MASRI and pill count at 8 weeks (r = 0.49, P = 0.02) but not at 12 weeks (r = 0.05, P = 0.87). The MASRI correctly identified 93% and 96% of non-adherent women at 8 and 12 weeks, respectively. Sensitivity, specificity, and positive likelihood ratio of the MASRI for predicting non-adherence was 91%, 82%, and 5.1 at 8 weeks and 90%, 85% and 6.1 at 12 weeks.

CONCLUSIONS

The MASRI is a valid self-administered tool for measuring adherence to anti-cholinergic medication in women with OAB.

Rilpivirine versus efavirenz with emtricitabine/tenofovir disoproxil fumarate in treatment-naïve HIV-1-infected patients with HIV-1 RNA ≤100,000 copies/mL: week 96 pooled ECHO/THRIVE subanalysis

The once daily, single-tablet regimen (STR) combining rilpivirine (RPV), emtricitabine (FTC), and tenofovir disoproxil fumarate (TDF) provides a simplified treatment option for antiretroviral therapy (ART)-naïve patients with baseline HIV-1 RNA (BLVL) of ≤100,000 copies/mL. The aim of this analysis is to compare long-term efficacy, safety, and tolerability of RPV+FTC/TDF vs. efavirenz (EFV)+FTC/TDF as individual components in subjects with BLVL ≤100,000 copies/mL. Week 96 efficacy and safety data from subjects with BLVL ≤100,000 copies/mL, who received daily RPV 25 mg or EFV 600 mg with FTC/TDF in the phase 3, randomized, double-blind, double-dummy, active-controlled, registrational trials ECHO and THRIVE, were analyzed. Virologic response was evaluated by intent-to-treat, time to loss of virological response (ITT-TLOVR), and Snapshot algorithms. Through Week 96, RPV+FTC/TDF demonstrated non-inferior efficacy to EFV+FTC/TDF (84% vs. 81%, respectively; ITT-TLOVR) in 543 subjects with BLVL ≤100,000 copies/mL, and overall rates of virologic failure (VF) were 5.9% vs. 2.4%, respectively. Resistance development was lower in Year 2 than Year 1. Subjects in both arms with suboptimal adherence (≤95%) had lower virologic responses (63% vs. 62%, respectively). Treatment with RPV+FTC/TDF was associated with significantly fewer treatment-related adverse events (AEs), grade 2-4 AEs, neurological and psychiatric AEs (including dizziness and abnormal dreams/nightmares), and rash. Additionally, grade 2-4 treatment-emergent laboratory abnormalities and grade 1-3 lipid abnormalities were significantly less common with RPV+FTC/TDF than EFV+FTC/TDF. RPV+FTC/TDF demonstrated non-inferior efficacy to EFV+FTC/TDF in ART-naïve subjects with BLVL ≤100,000 copies/mL and was associated with a higher rate of VF but a more favorable safety and tolerability profile through Week 96.

Antiretrovirals and the kidney in current clinical practice: renal pharmacokinetics, alterations of renal function and renal toxicity

Assessment of renal function in HIV-positive patients is of increasing importance in the context of ageing and associated comorbidities. Exposure to nephrotoxic medications is widespread, and several commonly used antiretroviral drugs have nephrotoxic potential. Moreover, specific antiretrovirals inhibit renal tubular transporters resulting in the potential for drug-drug interactions as well as increases in serum creatinine concentrations, which affect estimates of glomerular filtration rate in the absence of changes in actual glomerular filtration rate. This review explores the effects of antiretroviral therapy on the kidney and offers an understanding of mechanisms that lead to apparent and real changes in renal function.

Has the time come to abandon efavirenz for first-line antiretroviral therapy?

Efavirenz has been recommended as a preferred third agent together with two nucleos(t)ides for first-line combination antiretroviral therapy (ART) for >15 years. The availability of efavirenz in a fixed-dose combination makes it very attractive. However, because of (i) adverse events associated with efavirenz, (ii) a poorer overall efficacy of efavirenz compared with newer antiretrovirals, (iii) the ranking of efavirenz as FDA Pregnancy Category D and (iv) the relatively high prevalence of transmitted drug-resistance mutations, there is a need to reconsider the role of efavirenz in first-line ART. We review the available evidence that challenges efavirenz's current position in first-line HIV treatment guidelines. Apart from its animal teratogenic potential, and moderate neuropsychiatric adverse events associated with its use, efavirenz has recently been associated with an increased risk of suicidality when compared with other antiretroviral drugs. Most importantly, efavirenz has demonstrated overall inferior efficacy to various comparator drugs, which include rilpivirine, raltegravir and dolutegravir, in antiretroviral-naive patients. Furthermore, epidemiological data indicate that the prevalence of non-nucleoside reverse transcriptase inhibitor resistance has reached 5%-8% in various parts of the world, and minority transmitted non-nucleoside reverse transcriptase inhibitor resistance-associated mutations can have a negative impact on the outcome of first-line efavirenz-based ART. Based on considerations of efficacy, toxicity and resistance, it is time to reconsider the routine use of efavirenz in ART. This, of course, presupposes that other antiretrovirals will be available in place of efavirenz, and may not be applicable in certain developing country settings where this is not the case.

Efficacy of Tenofovir 1% Vaginal Gel in Reducing the Risk of HIV-1 and HSV-2 Infection

Human Immunodeficiency Virus (HIV) is a retrovirus that can result in rare opportunistic infections occurring in humans. The onset of these infections is known as Acquired Immune Deficiency Syndrome (AIDS). Sexual transmission is responsible for the majority of infections 1, resulting in transmission of HIV due to infected semen or vaginal and cervical secretions containing infected lymphocytes. HIV microbicides are formulations of chemical or biological agents that can be applied to the vagina or rectum with the intention of reducing the acquisition of HIV. Tenofovir is an NRTI that is phosphorylated by adenylate kinase to tenofovir diphosphate, which in turn competes with deoxyadeosine 5’-triphosphate for incorporation into newly synthesized HIV DNA. Once incorporated, tenofovir diphosphate results in chain termination, thus inhibiting viral replication. Tenofovir has been formulated into a range of vaginal formulations, such as rings, tablets gels and films. It has been shown to safe and effective in numerous animal models, while demonstrating safety and acceptability in numerous human trials. The most encouraging results came from the CAPRISA 004 clinical trial which demonstrated that a 1% Tenofovir vaginal gel reduced HIV infection by approximately 39%.

Neurological and psychiatric adverse effects of antiretroviral drugs

Antiretroviral drugs are associated with a variety of adverse effects on the central and peripheral nervous systems. The frequency and severity of neuropsychiatric adverse events is highly variable, with differences between the antiretroviral classes and amongst the individual drugs in each class. In the developing world, where the nucleoside reverse transcriptase inhibitor (NRTI) stavudine remains a commonly prescribed antiretroviral, peripheral neuropathy is an important complication of treatment. Importantly, this clinical entity is often difficult to distinguish from human immunodeficiency virus (HIV)-induced peripheral neuropathy. Several clinical trials have addressed the efficacy of various agents in the treatment of NRTI-induced neurotoxicity. NRTI-induced neurotoxicity is caused by inhibition of mitochondrial DNA polymerase. This mechanism is also responsible for the mitochondrial myopathy and lactic acidosis that occur with zidovudine. NRTIs, particularly zidovudine and abacavir, may also cause central nervous system (CNS) manifestations, including mania and psychosis. The non-nucleoside reverse transcriptase inhibitor (NNRTI) efavirenz is perhaps the antiretroviral most commonly associated with CNS toxicity, causing insomnia, irritability and vivid dreams. Recent studies have suggested that the risk of developing these adverse effects is increased in patients with various cytochrome P450 2B6 alleles. Protease inhibitors cause perioral paraesthesias and may indirectly increase the relative risk of stroke by promoting atherogenesis. HIV integrase inhibitors, C-C chemokine receptor type 5 (CCR5) inhibitors and fusion inhibitors rarely cause neuropsychiatric manifestations.

Early virologic response to abacavir/lamivudine and tenofovir/emtricitabine during ACTG A5202

BACKGROUND

ACTG A5202 randomized treatment-naïve individuals to tenofovir-emtricitabine (TDF/FTC) or abacavir-lamivudine (ABC/3TC) combined with efavirenz (EFV) or atazanavir/ritonavir (ATV/r). Individuals in the high screening viral load (VL) stratum (≥100,000 copies/mL) had increased rates of virologic failure with ABC/3TC.

OBJECTIVE

To compare regimen-specific early virologic response.

METHODS

Using Wilcoxon rank-sum tests, we compared regimen-specific VL changes from entry to week 4 in A5202 subjects (N = 1,813) and from entry to week 1, 2, and 4 in substudy subjects (n = 179). We evaluated associations between week 4 VL change and time to virologic failure with Cox proportional hazards models.

RESULTS

TDF/FTC and ABC/3TC produced similar week 4 VL declines in the entire study population and in the high VL stratum. EFV produced greater VL declines from baseline at week 4 than ATV/r (median -2.1 vs -1.9 log10 copies/mL; P < .001). In the substudy of subjects with week 1, 2, and 4 VL data, there was no difference in VL decline in individuals randomized to TDF/FTC versus ABC/3TC, but EFV resulted in greater VL decline from entry at each of these timepoints than ATV/r. Smaller week 4 VL decline was associated with increased risk of virologic failure.

CONCLUSIONS

Within all treatment arms, a less robust week 4 virologic response was associated with higher risk for subsequent virologic failure. However, between-regimen differences in week 4 VL declines did not parallel the previously reported differences in longer term virologic efficacy in A5202, suggesting that between-regimen differences in responses were not due to intrinsic differences in antiviral activity.

Change in vitamin D levels and risk of severe vitamin D deficiency over 48 weeks among HIV-1-infected, treatment-naive adults receiving rilpivirine or efavirenz in a Phase III trial (ECHO)

BACKGROUND

This analysis assessed changes in serum 25-hydroxyvitamin D (25[OH]D; the precursor form of active vitamin D) in antiretroviral-naive adults receiving rilpivirine or efavirenz over 48 weeks in a randomized, double-blind, Phase III trial (ECHO).

METHODS

ECHO included 690 patients randomized 1:1 to receive rilpivirine 25 mg once daily (n=346) or efavirenz 600 mg once daily (n=344), plus tenofovir disoproxil fumarate/emtricitabine. 25(OH)D was measured in stored serum samples collected at baseline, and weeks 24 and 48. Proportions of patients with optimal/sufficient (≥30 ng/ml), insufficient (21-29 ng/ml), deficient (10-20 ng/ml) and severely deficient (<10 ng/ml) 25(OH)D levels were determined. Data are presented for patients with paired baseline and week 48 25(OH)D data (rilpivirine, n=292; efavirenz, n=290).

RESULTS

After 48 weeks, mean 25(OH)D levels remained largely unchanged from baseline with rilpivirine (-0.2 ng/ml; P=0.57 versus no change), but were significantly reduced with efavirenz (-2.5 ng/ml; P<0.0001 versus no change). When adjusting for season of randomization and the combined variable of race (Black/African American, White/Caucasian, Asian, other race) and ethnicity (Hispanic or Latino and not Hispanic or not Latino), the conclusion about the treatment difference between the rilpivirine and efavirenz treatment groups remained valid. At baseline the proportion of patients with severe 25(OH)D deficiency was similar in both groups (5%) but was significantly lower with rilpivirine than efavirenz at week 48 (5% versus 9%, respectively; P=0.032). Furthermore, of the patients with 25(OH)D insufficiency/deficiency at baseline, the proportion who developed severe 25(OH)D deficiency at week 48 was significantly lower with rilpivirine than efavirenz (2% versus 8%, respectively; P=0.0079).

CONCLUSIONS

Rilpivirine had little effect on 25(OH)D, whereas efavirenz resulted in a significant reduction in 25(OH)D levels and an increase in the risk of severe 25(OH)D deficiency.

Metabolic disease in HIV infection

The treatment of metabolic disease is becoming an increasingly important component of the long-term management of patients with well controlled HIV on antiretroviral therapy (ART). Metabolic diseases probably develop at the intersection of traditional risk factors (such as obesity, tobacco use, and genetic predisposition) and HIV-specific and ART-specific contributors (including chronic inflammation and immune activation). This Review discusses present knowledge on adipose tissue dysfunction, insulin-glucose homoeostasis, lipid disturbances, and cardiovascular disease risk in people with HIV on ART. Although new antiretroviral drugs are believed to induce fewer short-term metabolic perturbations than do older drugs, the long-term effects of these drugs are not fully understood. Additionally, patients remain at increased risk of cardiovascular disease and other metabolic comorbidities. Research and treatment should focus on selection of ART that is both virologically effective and has minimum metabolic effects, minimisation of traditional risk factors for metabolic disease, and development of novel therapies to treat metabolic disease in patients with HIV, including use of anti-inflammatory and immunomodulatory drugs.

Antiviral Agents☆

Antiviral agents are drugs approved in the USA by the Food and Drug Administration (FDA) for the treatment or control of viral infections. Available antiviral agents mainly target stages in the viral life cycle. The target stages in the viral life cycle are; viral attachment to host cell, uncoating, synthesis of viral mRNA, translation of mRNA, replication of viral RNA and DNA, maturation of new viral proteins, budding, release of newly synthesized virus, and free virus in body fluids.

Two important factors that can limit the utility of antiviral drugs are toxicity and the development of resistance to the antiviral agent by the virus. In addition, host phenotypic behaviors toward antiviral drugs because of either genomic or epigenetic factors could limit the efficacy of an antiviral agent in an individual. This article summarizes the most relevant pharmacologic and clinical properties of current antiviral agents, and targets for novel antiviral agents.

Single-tablet regimens in HIV: does it really make a difference?

OBJECTIVES

Review of the available data on the currently available single-tablet regimens (STRs), from the analysis of efficacy and safety to the key points of value in terms of adherence, quality of life and pharmacoeconomic evaluation.

METHODS

For this narrative review, literature searches have been performed in PubMed, IndexRevMed and Cochrane, using the search terms HIV, single-tablet, one-pill, single dose, fixed-dose, and STR. These have been reviewed and complemented with the most recent publications of interest.

RESULTS

Fixed-dose combinations are a significant advance in antiretroviral treatment simplification, contributing to an increase in compliance with complex chronic therapies, thus improving patients' quality of life. Reducing the number of pills and daily doses is associated with higher adherence and better quality of life. As a fixed-dose combination tablet given once daily, EFV/FTC/TDF was the first available STR combining efficacy, tolerability and convenience, with the simplest dosing schedule and smallest numbers of pills of any ART combination therapy. The RPV/FTC/TDF is a next-generation NNRTI-based STR, a once daily complete ART regimen for the treatment of HIV-1 infection. Recently the combination of EVG/COBI/FTC/TDF was also approved by the European Commission, and is the first integrase inhibitor-based STR. Receiving antiretroviral therapy as once daily STR is associated with both clinical and economic benefits, which confirms previous research.

CONCLUSIONS

The associated benefits of STRs provide a valid strategy for the treatment of HIV-infected patients.

In vitro characterization of MK-1439, a novel HIV-1 nonnucleoside reverse transcriptase inhibitor

Nonnucleoside reverse transcriptase inhibitors (NNRTIs) are a mainstay of therapy for treating human immunodeficiency type 1 virus (HIV-1)-infected patients. MK-1439 is a novel NNRTI with a 50% inhibitory concentration (IC50) of 12, 9.7, and 9.7 nM against the wild type (WT) and K103N and Y181C reverse transcriptase (RT) mutants, respectively, in a biochemical assay. Selectivity and cytotoxicity studies confirmed that MK-1439 is a highly specific NNRTI with minimum off-target activities. In the presence of 50% normal human serum (NHS), MK-1439 showed excellent potency in suppressing the replication of WT virus, with a 95% effective concentration (EC95) of 20 nM, as well as K103N, Y181C, and K103N/Y181C mutant viruses with EC95 of 43, 27, and 55 nM, respectively. MK-1439 exhibited similar antiviral activities against 10 different HIV-1 subtype viruses (a total of 93 viruses). In addition, the susceptibility of a broader array of clinical NNRTI-associated mutant viruses (a total of 96 viruses) to MK-1439 and other benchmark NNRTIs was investigated. The results showed that the mutant profile of MK-1439 was superior overall to that of efavirenz (EFV) and comparable to that of etravirine (ETR) and rilpivirine (RPV). Furthermore, E138K, Y181C, and K101E mutant viruses that are associated with ETR and RPV were susceptible to MK-1439 with a fold change (FC) of <3. A two-drug in vitro combination study indicated that MK-1439 acts nonantagonistically in the antiviral activity with each of 18 FDA-licensed drugs for HIV infection. Taken together, these in vitro data suggest that MK-1439 possesses the desired properties for further development as a new antiviral agent.

Advances in antiretroviral therapy

PURPOSE OF REVIEW

To review recent data about advances in ART.

RECENT FINDINGS

In the last 2 years, clinical trials have demonstrated the safety and efficacy of three integrase transfer inhibitors [raltegravir (RAL), elvitegravir (EVG) and dolutegravir (DTG)], one new nonnucleoside reverse transcriptase inhibitor [rilpivirine (RIL)] and a new extended release formulation of nevirapine in antiretroviral-naive and experienced patients. Cobicistat (COBI), a new pharmacologic enhancer without antiretroviral activity has been studied as a booster of EVG and atazanavir (ATV). Two new single-pill fixed-dose combinations (FDCs) have been approved by regulatory agencies: RIL/tenofovir (TDF) difumarate/emtricitabine and elvitegravir/COBI/TDF difumarate/emtricitabine. A new prodrug of TDF is going to be evaluated in phase III clinical trials with the goal of showing less bone and renal toxicity. Ongoing trials are evaluating the use of nucleoside sparing regimens in antiretroviral-naive patients. Generic formulations of multiple antiretrovirals would become available in the immediate future. The efficacy and price reduction associated with generic antiretrovirals remains to be elucidated.

SUMMARY

In the last 2 years, the antiretroviral armamentarium has been significantly expanded by the advent of the integrase transfer inhibitors RAL, EVG and DTG, by a new nonnucleoside reverse transcriptase inhibitor, RIL and by two new single-pill FDCs.

[Safety profile of rilpivirine: general and neuropsychiatric tolerability, safety in patients with hepatitis B or C viruses, and lipid profile]

Currently available data on the safety and tolerability of rilpivirine come from the product information document, a phase IIb, dose-finding clinical trial (TMC278-C204), the phase III ECHO and THRIVE clinical trials, and the preliminary data from the STaR and SPIRIT clinical trials, with a total of 1,728 patients. The comparator has usually been efavirenz. All studies have found a lower incidence and severity of neuropsychiatric adverse effects, a better lipid profile, and a lower number of patients with subclinical transaminase elevation in patients treated with rilpivirine. However, because of the relatively low number of patients coinfected with hepatitis B or C virus, definitive conclusions cannot be drawn. Similarly, experience in patients with mild or moderate liver failure is limited and there are no safety data in patients with advanced liver failure.

Dolutegravir plus abacavir-lamivudine for the treatment of HIV-1 infection

BACKGROUND

Dolutegravir (S/GSK1349572), a once-daily, unboosted integrase inhibitor, was recently approved in the United States for the treatment of human immunodeficiency virus type 1 (HIV-1) infection in combination with other antiretroviral agents. Dolutegravir, in combination with abacavir-lamivudine, may provide a simplified regimen.

METHODS

We conducted a randomized, double-blind, phase 3 study involving adult participants who had not received previous therapy for HIV-1 infection and who had an HIV-1 RNA level of 1000 copies per milliliter or more. Participants were randomly assigned to dolutegravir at a dose of 50 mg plus abacavir-lamivudine once daily (DTG-ABC-3TC group) or combination therapy with efavirenz-tenofovir disoproxil fumarate (DF)-emtricitabine once daily (EFV-TDF-FTC group). The primary end point was the proportion of participants with an HIV-1 RNA level of less than 50 copies per milliliter at week 48. Secondary end points included the time to viral suppression, the change from baseline in CD4+ T-cell count, safety, and viral resistance.

RESULTS

A total of 833 participants received at least one dose of study drug. At week 48, the proportion of participants with an HIV-1 RNA level of less than 50 copies per milliliter was significantly higher in the DTG-ABC-3TC group than in the EFV-TDF-FTC group (88% vs. 81%, P=0.003), thus meeting the criterion for superiority. The DTG-ABC-3TC group had a shorter median time to viral suppression than did the EFV-TDF-FTC group (28 vs. 84 days, P<0.001), as well as greater increases in CD4+ T-cell count (267 vs. 208 per cubic millimeter, P<0.001). The proportion of participants who discontinued therapy owing to adverse events was lower in the DTG-ABC-3TC group than in the EFV-TDF-FTC group (2% vs. 10%); rash and neuropsychiatric events (including abnormal dreams, anxiety, dizziness, and somnolence) were significantly more common in the EFV-TDF-FTC group, whereas insomnia was reported more frequently in the DTG-ABC-3TC group. No participants in the DTG-ABC-3TC group had detectable antiviral resistance; one tenofovir DF-associated mutation and four efavirenz-associated mutations were detected in participants with virologic failure in the EFV-TDF-FTC group.

CONCLUSIONS

Dolutegravir plus abacavir-lamivudine had a better safety profile and was more effective through 48 weeks than the regimen with efavirenz-tenofovir DF-emtricitabine. (Funded by ViiV Healthcare; SINGLE ClinicalTrials.gov number, NCT01263015 .).

[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.

Economic evaluation of initial antiretroviral therapy for HIV-infected patients: an update of Italian guidelines

Introduction

Highly active antiretroviral therapy (HAART) has allowed many HIV-infected patients to enjoy longer survival and a better quality of life. We performed an economic analysis to estimate the cost-effectiveness of HAART regimens in Italy for managing HIV-naïve infected patients with a viral load below 100,000 copies/mL.

Patients and methods

The population considered in the model consisted of adult subjects with an HIV viral load below 100,000 copies/mL who received antiretroviral HAART treatment for the first time, according to the Italian National Guidelines with recommendation grade A1. The incremental cost-effectiveness analysis of quality-adjusted life years (QALYs) was carried out by means of a Markov model. Both the outcomes (QALYs) and the costs were discounted by 3.5%. The time horizon adopted in the model was 10 years. The point of view of the analysis was that of the Italian national health service.

Results

The tenofovir (TDF)/emtricitabine (FTC)/rilpivirine (RPV) single-tablet regimen (STR) (€7,417.00) revealed the lowest mean treatment cost. TDF/FTC + raltegravir (RAL) showed a better quality of life (0.906 QALY/year), followed by TDF/FTC/RPV (STR; 0.900 QALY/year), TDF/FTC + RPV (multipill regimen) (0.889 QALY/year), and TDF/FTC + atazanavir (ATV/r) (0.886 QALY/year). TDF/FTC/RPV (STR) appeared to be the most cost-effective therapeutic choice (€13,655.00), followed by TDF/FTC + RPV (multipill regimen) (€15,803.00), and TDF/FTC + efavirenz (EFV) (€16,181.00). The sensitivity analysis on the main variables confirmed the validity of the base case scenario.

Conclusion

STR (TDF/FTC/RPV) is the most cost-effective treatment strategy compared with the other therapeutic regimens recommended by the Italian guidelines for the treatment of naïve patients with a viral load <100,000 copies/mL. The inclusion of adverse-event management of HIV-infected patients affects the cost-effectiveness ratio of all HAART regimens.

Optimization of diarylazines as anti-HIV agents with dramatically enhanced solubility

Non-nucleoside inhibitors of HIV-1 reverse transcriptase are reported that have ca. 100-fold greater solubility than the structurally related drugs etravirine and rilpivirine, while retaining high anti-viral activity. The solubility enhancements come from strategic placement of a morpholinylalkoxy substituent in the entrance channel of the NNRTI binding site. Compound 4d shows low-nanomolar activity similar to etravirine towards wild-type HIV-1 and key viral variants.

Extension into the entrance channel of HIV-1 reverse transcriptase--crystallography and enhanced solubility

Non-nucleoside inhibitors of HIV-1 reverse transcriptase (HIV-RT) are reported that feature extension into the entrance channel near Glu138. Complexes of the parent anilinylpyrimidine 1 and the morpholinoethoxy analog 2j with HIV-RT have received crystallographic characterization confirming the designs. Measurement of aqueous solubilities of 2j, 2k, the parent triazene 2a, and other NNRTIs demonstrate profound benefits for addition of the morpholinyl substituent.

Rilpivirine inhibits drug transporters ABCB1, SLC22A1, and SLC22A2 in vitro

Rilpivirine is a nonnucleoside reverse transcriptase inhibitor approved for treatment of HIV-1 infection in antiretroviral-naive adult patients. Potential interactions with drug transporters have not been fully investigated. Transport by and inhibition of drug transporters by rilpivirine were analyzed to further understand the mechanisms governing rilpivirine exposure and determine the potential for transporter-mediated drug-drug interactions. The ability of rilpivirine to inhibit or be transported by ABCB1 was determined using ABCB1-overexpressing CEMVBL100 cells and Caco-2 cell monolayers. The Xenopus laevis oocyte heterologous protein expression system was used to clarify if rilpivirine was either transported by or inhibited the function of influx transporters SLCO1A2, SLCO1B1, SLCO1B3, SLC22A2, SLC22A6, and SLC22A8. The ability of rilpivirine to inhibit or be transported by SLC22A1 was determined using SLC22A1-expressing KCL22 cells. Rilpivirine showed higher accumulation in SLC22A1-overexpressing KCL22 cells than control cells (27% increase, P = 0.03) and inhibited the functionality of SLC22A1 and SLC22A2 transport with 50% inhibitory concentrations (IC50s) of 28.5 μM and 5.13 μM, respectively. Inhibition of ABCB1-mediated digoxin transport was determined for rilpivirine, which inhibited digoxin transport in the B-to-A direction with an IC50 of 4.48 μM. The maximum rilpivirine concentration in plasma in patients following a standard 25-mg dosing regimen is around 0.43 μM, lower than that necessary to substantially inhibit ABCB1, SLC22A1, or SLC22A2 in vitro. However, these data indicate that SLC22A1 may contribute to variability in rilpivirine exposure and that interactions of rilpivirine with substrates of SLC22A1, SLC22A2, or ABCB1 may be possible.

Week 96 analysis of rilpivirine or efavirenz in HIV-1-infected patients with baseline viral load ≤ 100 000 copies/mL in the pooled ECHO and THRIVE phase 3, randomized, double-blind trials

OBJECTIVES

These 96-week, ECHO/THRIVE pooled analyses evaluated data for antiretroviral treatment-naïve, HIV-1-infected adults with viral load (VL) ≤ 100 000 HIV-1 RNA copies/mL receiving rilpivirine or efavirenz.

METHODS

ECHO and THRIVE were phase 3, randomized, double-blind trials. Patients received rilpivirine 25 mg once daily (qd) or efavirenz 600 mg qd, with a fixed (ECHO) or investigator-chosen (THRIVE) nucleoside/tide reverse transcriptase inhibitor (N[t]RTI) background regimen. Response rate (the percentage of patients with VL < 50 copies/mL, using an intent-to-treat-population, time-to-loss-of-virological-response algorithm), virological failure (VF), resistance development, safety and tolerability were evaluated.

RESULTS

Baseline characteristics were comparable between the rilpivirine (n = 368) and efavirenz (n = 329) groups. At week 96, response rates [84% for rilpivirine vs. 80% for efavirenz; difference 4.0%; 95% confidence interval (CI) -1.7% to 9.7%] and incidences of VF for the resistance analysis (VFres) (8% for rilpivirine vs. 6% for efavirenz; P = 0.46) were similar in the two groups. Among patients with VFres , a comparable proportion in each group developed nonnucleoside reverse transcriptase inhibitor (NNRTI) resistance-associated mutations (RAMs). Among those with VFres , more patients in the rilpivirine group than in the efavirenz group developed N[t]RTI RAMs, mostly M184I/V. The mean (95% CI) CD4 cell count increased from baseline to week 96 by 224 (208-240) cells/μL in the rilpivirine group and by 206 (188-225) cells/μL in the efavirenz group. Treatment-related grade 2-4 overall adverse events, any rash and dizziness were less frequent for rilpivirine than for efavirenz (P < 0.0001).

CONCLUSIONS

Rilpivirine demonstrated antiviral efficacy similar to that of efavirenz in antiretroviral treatment-naïve adults with baseline VL ≤ 100 000 copies/mL over 96 weeks. Frequencies of VFres and emergent NNRTI RAMs in each group were similar. More patients with VFres in the rilpivirine group than in the efavirenz group developed N[t]RTI RAMs (mostly M184I/V). Rilpivirine had a more favourable safety/tolerability profile than efavirenz.

[Analysis of costs and cost-effectiveness of preferred GESIDA/National AIDS Plan regimens for initial antiretroviral therapy in human immunodeficiency virus infected adult patients in 2013]

INTRODUCTION

The GESIDA and National AIDS Plan panel of experts have proposed "preferred regimens" of antiretroviral treatment (ART) as initial therapy in HIV infected patients for 2013. The objective of this study is to evaluate the costs and effectiveness of initiating treatment with these "preferred regimens".

METHODS

An economic assessment of costs and effectiveness (cost/effectiveness) was performed using decision tree analysis models. Effectiveness was defined as the probability of having viral load <50copies/mL at week48, in an intention-to-treat analysis. Cost of initiating treatment with an ART regime was defined as the costs of ART and its consequences (adverse effects, changes of ART regime and drug resistance analyses) during the first 48weeks. The perspective of the analysis is that of the National Health System was applied, only taking into account differential direct costs: ART (official prices), management of adverse effects, resistance studies, and determination of HLA B*5701. The setting is Spain and the costs are those of 2013. A sensitivity deterministic analysis was performed, constructing three scenarios for each regimen: baseline, most favourable, and most unfavourable cases.

RESULTS

In the baseline case scenario, the cost of initiating treatment ranges from 6,747euros for TDF/FTC+NVP to 12,059euros for TDF/FTC+RAL. The effectiveness ranges between 0.66 for ABC/3TC+LPV/r and ABC/3TC+ATV/r, and 0.87 for TDF/FTC+RAL and ABC/3TC+RAL. Effectiveness, in terms of cost/effectiveness, varies between 8,396euros and 13,930euros per responder at 48weeks, for TDF/FTC/RPV and TDF/FTC+RAL, respectively.

CONCLUSIONS

Taking ART at official prices, the most effective regimen was TDF/FTC/RPV, followed by the rest of non-nucleoside containing regimens. The sensitivity analysis confirms the robustness of these findings.

Human biotransformation of the nonnucleoside reverse transcriptase inhibitor rilpivirine and a cross-species metabolism comparison

Rilpivirine is a nonnucleoside reverse transcriptase inhibitor used to treat HIV-1. In the present study, the pathways responsible for the biotransformation of rilpivirine were defined. Using human liver microsomes, the formation of two mono- and two dioxygenated metabolites were detected via ultra high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Mass spectral analysis of the products suggested that these metabolites resulted from oxygenation of the 2,6-dimethylphenyl ring and methyl groups of rilpivirine. Chemical inhibition studies and cDNA-expressed cytochrome P450 (CYP) assays indicated that oxygenations were catalyzed primarily by CYP3A4 and CYP3A5. Glucuronide conjugates of rilpivirine and a monomethylhydroxylated metabolite of rilpivirine were also detected and were found to be formed by UDP-glucuronosyltransferases (UGTs) UGT1A4 and UGT1A1, respectively. All metabolites that were identified in vitro were detectable in vivo. Further, targeted UHPLC-MS/MS-based in vivo metabolomics screening revealed that rilpivirine treatment versus efavirenz treatment may result in differential levels of endogenous metabolites, including tyrosine, homocysteine, and adenosine. Rilpivirine biotransformation was also assessed across species using liver microsomes isolated from a range of mammals, and the metabolite profile identified using human liver microsomes was largely conserved for both oxidative and glucuronide metabolite formation. These studies provide novel insight into the metabolism of rilpivirine and the potential differential effects of rilpivirine- and efavirenz-containing antiretroviral regimens on the endogenous metabolome.

The next therapeutic challenge in HIV: polypharmacy

With the adoption of combination antiretroviral therapy (ART), most HIV-infected individuals in care are on five or more medications and at risk of harm from polypharmacy, a risk that likely increases with number of medications, age, and physiologic frailty. Established harms of polypharmacy include decreased medication adherence and increased serious adverse drug events, including organ system injury, hospitalization, geriatric syndromes (falls, fractures, and cognitive decline) and mortality. The literature on polypharmacy among those with HIV infection is limited, and the literature on polypharmacy among non-HIV patients requires adaptation to the special issues facing those on chronic ART. First, those aging with HIV infection often initiate ART in their 3rd or 4th decade of life and are expected to remain on ART for the rest of their lives. Second, those with HIV may be at higher risk for age-associated comorbid disease, further increasing their risk of polypharmacy. Third, those with HIV may have an enhanced susceptibility to harm from polypharmacy due to decreased organ system reserve, chronic inflammation, and ongoing immune dysfunction. Finally, because ART is life-extending, nonadherence to ART is particularly concerning. After reviewing the relevant literature, we propose an adapted framework with which to address polypharmacy among those on lifelong ART and suggest areas for future work.

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.

Deficient reporting and interpretation of non-inferiority randomized clinical trials in HIV patients: a systematic review

OBJECTIVES

Non-inferiority (NI) randomized clinical trials (RCTs) commonly evaluate efficacy of new antiretroviral (ARV) drugs in human immunodeficiency virus (HIV) patients. Their reporting and interpretation have not been systematically evaluated. We evaluated the reporting of NI RCTs in HIV patients according to the CONSORT statement and assessed the degree of misinterpretation of RCTs when NI was inconclusive or not established.

DESIGN

Systematic review.

METHODS

PubMed, Web of Science, and Scopus were reviewed until December 2011. Selection and extraction was performed independently by three reviewers.

RESULTS

Of the 42 RCTs (n = 21,919; range 41-3,316) selected, 23 were in ARV-naïve and 19 in ARV-experienced patients. Twenty-seven (64%) RCTs provided information about prior RCTs of the active comparator, and 37 (88%) used 2-sided CIs. Two thirds of trials used a NI margin between 10 and 12%, although only 12 explained the method to determine it. Blinding was used in 9 studies only. The main conclusion was based on both intention-to-treat (ITT) and per protocol (PP) analyses in 5 trials, on PP analysis only in 4 studies, and on ITT only in 31 studies. Eleven of 16 studies with NI inconclusive or not established highlighted NI or equivalence, and distracted readers with positive secondary results.

CONCLUSIONS

There is poor reporting and interpretation of NI RCTs performed in HIV patients. Maximizing the reporting of the method of NI margin determination, use of blinding and both ITT and PP analyses, and interpreting negative NI according to actual primary findings will improve the understanding of results and their translation into clinical practice.

Update on rilpivirine: a new potent non-nucleoside reverse transcriptase inhibitor (NNRTI) of HIV replication

INTRODUCTION

A combination of antiretroviral drugs (ARVs) is necessary to achieve sustained virologic suppression of HIV viral load (< 50 copies/mL). Rilpivirine (RPV) is a potent new non-nucleoside reverse transcriptase inhibitor (NNRTI) that has the potential to be part of effective ARV combinations. Here, we review currently available data on RPV from the standpoint of virologic suppression and efficacy, drug-drug interactions safety, and resistance.

AREAS COVERED

This review presents data on the results of clinical trials involving RPV. The topics considered include antiviral potency, dosing, clinical utility, drug resistance, toxicity profile, and pharmacokinetics.

EXPERT OPINION

RPV is a potent new addition to the antiretroviral family of drugs for use in combination therapy in previously untreated HIV-infected patients. However, caution needs to be exercised in administration of RPV to patients who initiated therapy with viral loads > 100,000 viral RNA copies/mL.

A validated assay by liquid chromatography-tandem mass spectrometry for the simultaneous quantification of elvitegravir and rilpivirine in HIV positive patients

Because of the large variability in the pharmacokinetics of anti-HIV drugs, therapeutic drug monitoring in patients may contribute to optimize the overall efficacy and safety of antiretroviral therapy. An LC-MS/MS method for the simultaneous assay in plasma of the novel antiretroviral agents rilpivirine (RPV) and elvitegravir (EVG) has been developed to that endeavor. Plasma samples (100 μL) extraction is performed by protein precipitation with acetonitrile, and the supernatant is subsequently diluted 1:1 with 20-mM ammonium acetate/MeOH 50:50. After reverse-phase chromatography, quantification of RPV and EVG, using matrix-matched calibration samples, is performed by electrospray ionization-triple quadrupole mass spectrometry by selected reaction monitoring detection using the positive mode. The stable isotopic-labeled compounds RPV-(13) C6 and EVG-D6 were used as internal standards. The method was validated according to FDA recommendations, including assessment of extraction yield, matrix effects variability (<6.4%), as well as EVG and RPV short and long-term stability in plasma. Calibration curves were validated over the clinically relevant concentrations ranging from 5 to 2500 ng/ml for RPV and from 50 to 5000 ng/ml for EVG. The method is precise (inter-day CV%: 3-6.3%) and accurate (3.8-7.2%). Plasma samples were found to be stable (<15%) in all considered conditions (RT/48 h, +4°C/48 h, -20°C/3 months and 60°C/1 h). Selected metabolite profiles analysis in patients' samples revealed the presence of EVG glucuronide, that was well separated from parent EVG, allowing to exclude potential interferences through the in-source dissociation of glucuronide to parent drug. This new, rapid and robust LCMS/MS assay for the simultaneous quantification of plasma concentrations of these two major new anti-HIV drugs EVG and RPV offers an efficient analytical tool for clinical pharmacokinetics studies and routine therapeutic drug monitoring service.

Resistance to the most recent protease and non-nucleoside reverse transcriptase inhibitors across HIV-1 non-B subtypes

OBJECTIVES

Limited data are available on resistance to etravirine, rilpivirine, darunavir and tipranavir in patients infected with HIV-1 non-B subtypes, in which natural polymorphisms at certain positions could influence the barrier and/or pathways to drug resistance.

METHODS

FASTA format sequences from the reverse transcriptase and protease genes recorded within the Spanish Drug Resistance database (ResRIS) were examined.

RESULTS

From 8272 genotypes derived from 5930 different HIV-1 patients included in ResRIS, 5276 genotypes had complete treatment information. Overall, 85% were from antiretroviral-experienced subjects and 7.5% belonged to HIV-1 non-B subtypes: CRF02_AG, C, F and G being the most prevalent variants. For etravirine, only G190A was more prevalent in B than non-B subtypes, whereas V90I and V179E were more frequent in non-B than B subtypes. For rilpivirine, V108I and Y188I were more frequent in B than non-B subtypes, whereas V90I was more prevalent in non-B subtypes. Despite these differences, the overall prevalence of resistance did not differ significantly when comparing etravirine or rilpivirine in B versus non-B subtypes (11.3% versus 7.4%, P = 0.13, and 10.5% versus 7.4%, P = 0.23, respectively). Despite more frequent natural polymorphisms in non-B than B subtypes at tipranavir resistance positions, the prevalence of tipranavir resistance was greater in B than non-B subtypes (11% versus 4.3%, P = 0.004), reflecting a greater antiretroviral exposure in the former. Darunavir resistance did not differ significantly when comparing B and non-B subtypes (5.8% versus 5.5%, P = 0.998).

CONCLUSIONS

The rate of resistance to the most recently approved protease and non-nucleoside reverse transcriptase inhibitors is low in antiretroviral-experienced patients, regardless of the HIV-1 subtype.

New therapeutic landscape of NNRTIs for treatment of HIV: a look at recent data

INTRODUCTION

A key objective with highly active antiretroviral therapy for the treatment of HIV infection has been the optimization of antiretroviral drug combinations for individual patients.

AREAS COVERED

Overall, non-nucleoside reverse transcriptase inhibitor (NNRTI)-based regimens (in combination with two nucleoside reverse transcriptase inhibitors (NRTIs)) have become mainstays for initial ARV regimens. Early NNRTIs, efavirenz and nevirapine, are similarly efficacious, but differ according to their toxicity profiles. Newer NNRTIs, rilpivirine and etravirine are also efficacious. Etravirine was designed to overcome common first-line NNRTI resistance mutations, and serves as a second line agent.

EXPERT OPINION

As a class, NNRTIs are key components of ARV regimens. Currently, there are 3 NNRTIs that may be used in first-line regimens, and one in second-line regimens. ARV regimen optimization depends on matching individual drug efficacy, safety, resistance, and toxicity profiles to particular patients. Once-daily dosing options are essential to treatment simplification strategies, which have been shown to enhance regimen compliance and durabiltiy. These are especially important due to the low genetic barrier to resistance generally associated with NNRTIs. As newer drugs are introduced, especially as part of once-daily, single-tablet regimens, this will expand the number of convenient and efficacious treatment options available.

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.

HIV-1 reverse transcriptase and antiviral drug resistance. Part 2

Structures of RT and its complexes combined with biochemical and clinical data help in illuminating the molecular mechanisms of different drug-resistance mutations. The NRTI drugs that are used in combinations have different primary mutation sites. RT mutations that confer resistance to one drug can be hypersensitive to another RT drug. Structure of an RT-DNA-nevirapine complex revealed how NNRTI binding forbids RT from forming a polymerase competent complex. Collective knowledge about various mechanisms of drug resistance by RT has broader implications for understanding and targeting drug resistance in general. In Part 1, we discussed the role of RT in developing HIV-1 drug resistance, structural and functional states of RT, and the nucleoside/nucleotide analog (NRTI) and non-nucleoside (NNRTI) drugs used in treating HIV-1 infections. In this part, we discuss structural understanding of various mechanisms by which RT confers antiviral drug resistance.