Efavirenz--still first-line king?

Current ARTs, Virologic Failure, and Implications for AIDS Management: A Systematic Review

Antiretroviral therapies (ARTs) have revolutionized the management of human immunodeficiency virus (HIV) infection, significantly improved patient outcomes, and reduced the mortality rate and incidence of acquired immunodeficiency syndrome (AIDS). However, despite the remarkable efficacy of ART, virologic failure remains a challenge in the long-term management of HIV-infected individuals. Virologic failure refers to the persistent detectable viral load in patients receiving ART, indicating an incomplete suppression of HIV replication. It can occur due to various factors, including poor medication adherence, drug resistance, suboptimal drug concentrations, drug interactions, and viral factors such as the emergence of drug-resistant strains. In recent years, extensive efforts have been made to understand and address virologic failure in order to optimize treatment outcomes. Strategies to prevent and manage virologic failure include improving treatment adherence through patient education, counselling, and supportive interventions. In addition, the regular monitoring of viral load and resistance testing enables the early detection of treatment failure and facilitates timely adjustments in ART regimens. Thus, the development of novel antiretroviral agents with improved potency, tolerability, and resistance profiles offers new options for patients experiencing virologic failure. However, new treatment options would also face virologic failure if not managed appropriately. A solution to virologic failure requires a comprehensive approach that combines individualized patient care, robust monitoring, and access to a range of antiretroviral drugs.

Comparison of Efavirenz and Doravirine Developmental Toxicity in an Embryo Animal Model

In the past, one of the most widely used non-nucleoside reverse transcriptase inhibitors (NNRTI) in first-line antiretroviral therapy (ART) of HIV infection was efavirenz (EFV), which is already used as a cost-effective treatment in developing countries due to its efficacy, tolerability, and availability. However, EFV also demonstrates several adverse effects, like hepatotoxicity, altered lipid profile, neuropsychological symptoms, and behavioral effects in children after in utero exposure. In 2018, another NNRTI, doravirine (DOR), was approved due to its similar efficacy but better safety profile. Preclinical safety studies demonstrated that DOR is not genotoxic and exhibits no developmental toxicity or effects on fertility in rats. Zebrafish (Danio rerio) embryos have been widely accepted as a vertebrate model for pharmacological and developmental studies. We used zebrafish embryos as an in vivo model to investigate the developmental toxicity of DOR compared to EFV. After exposure of the embryos to the drugs from the gastrula stage up to different developmental stages (30 embryos for each arm, in three independent experiments), we assessed their survival, morphology, hatching rate, apoptosis in the developing head, locomotion behavior, vasculature development, and neutral lipid distribution. Overall, DOR showed a better safety profile than EFV in our model. Therapeutic and supra-therapeutic doses of DOR induced very low mortality [survival rates: 92, 90, 88, 88, and 81% at 1, 5, 10, 25, and 50 μM, respectively, at 24 h post fecundation (hpf), and 88, 85, 88, 89, and 75% at the same doses, respectively, at 48 hpf] and mild morphological alterations compared to EFV exposure also in the sub-therapeutic ranges (survival rates: 80, 77, 69, 63, and 44% at 1, 5, 10, 25, and 50 μM, respectively, at 24 hpf and 72, 70, 63, 52, and 0% at the same doses, respectively, at 48 hpf). Further, DOR only slightly affected the hatching rate at supra-therapeutic doses (97, 98, 96, 87, and 83% at 1, 5, 10, 25, and 50 μM, respectively, at 72 hpf), while EFV already strongly reduced hatching at sub-therapeutic doses (83, 49, 11, 0, and 0% at 1, 5, 10, 25, and 50 μM, respectively, at the same time endpoint). Both DOR at therapeutic doses and most severely EFV at sub-therapeutic doses enhanced apoptosis in the developing head during crucial phases of embryo neurodevelopment and perturbed the locomotor behavior. Furthermore, EFV strongly affected angiogenesis and disturbed neutral lipid homeostasis even at sub-therapeutic doses compared to DOR at therapeutic concentrations. Our findings in zebrafish embryos add further data confirming the higher safety of DOR with respect to EFV regarding embryo development, neurogenesis, angiogenesis, and lipid metabolism. Further studies are needed to explore the molecular mechanisms underlying the better pharmacological safety profile of DOR, and further human studies are required to confirm these results in the zebrafish animal model.

Efficacy and safety of ainuovirine versus efavirenz combination therapies with lamivudine/tenofovir disoproxil fumarate for medication of treatment-naïve HIV-1-positive adults: week 48 results of a randomized controlled phase 3 clinical trial followed by an open-label setting until week 96

Background

Ainuovirine (ANV) is a new non-nucleoside reverse transcriptase inhibitor (NNRTI), which was initially synthesized in Korea and later further developed in both Korea and China.

Methods

A randomized, double-blind, double-dummy, positive parallel group, non-inferiority, phase 3 trial was conducted in 7 sites across China. Eligible HIV-1-positive antiretroviral therapy (ART)-naïve adults aged 18-65 years were randomly assigned in a 1:1 ratio to receive tenofovir disoproxil fumarate and lamivudine (TDF+3TC) in combination with either ANV (ANV group) or efavirenz (EFV group) for up to 48 weeks. Subsequently, participants in both groups received one of the two drug combinations according to their choice until week 96 in an observational study under an open-label setting. The primary endpoint was the proportion of participants achieving HIV RNA <50 copies/mL at week 48, with non-inferiority pre-specified at a margin of 10%. The secondary efficacy endpoints were logarithmic changes in HIV RNA, percentage of participants with HIV RNA levels ≤400 copies/mL and changes in the CD4 T-cell count after 48 and 96 weeks of treatment, as well as the percentage of participants with HIV RNA levels <50 copies/mL at 96 weeks of treatment. Safety endpoints were the incidence of adverse events and laboratory abnormalities evaluated according to the Division of AIDS criteria. This study was registered with the Chinese Clinical Trial Registry (Registration number: ChiCTR1800019041).

Findings

Between November 27, 2018 and March 11, 2021, a total of 826 participants were screened, and 630 were finally enrolled and randomly assigned (1:1) to either ANV (n = 315) or EFV (n = 315) groups. The mean age was 30.6 ± 9.4 years and most participants were male (94.6%). At week 48, 274 (87.0%) of 315 participants in the ANV group and 288 (91.7%) of 314 in the EFV group achieved HIV-1 RNA <50 copies/mL and non-inferiority was established (difference: -4.7%, 95% CI: -9.6 to 0.1%). In the period, 293 participants continued to take the ANV regimen and 287 switched from the EFV to the ANV regimen. During the open-label period, 92.5% (271/293) of participants in the continued ANV group and 95.1% (273/287) in the ANV to EFV transfer group remained virologically suppressed (HIV-1 RNA <50 copies/mL) at week 96 (p = 0.189). The incidence of NNRTI treatment-related adverse events (TEAEs) at week 48 was 67.6% in 315 participants in the ANV group, which was significantly lower than in 91.4% of 314 participants in the EFV group (p < 0.001). The most common TEAEs (weeks 0-48) were dizziness (10.5%) and dyslipidemia (22.2%) in the ANV group vs. 51.0% and 34.4% in the EFV group, respectively, followed by transaminase elevation (9.2% vs. 29.0%), γ-glutamyl transferase elevation (8.3% vs. 19.1%), and rash (7.9% vs. 18.8%) (all p < 0.001). After switching from EFV to ANV, TEAEs in the former EFV participants were significantly reduced in the following observational period of 48-96 weeks.

Interpretation

The week 48 results indicated that the efficacy of ANV was non-inferior to EFV when combined with two NRTIs. The per-protocol risk difference at week 48 for the primary endpoint also supported non-inferiority. TEAEs in ANV treated participants were less frequent with regard to liver toxicity, dyslipidemia, neuropsychiatric symptoms and rash compared to the EFV group during the first 48 weeks of therapy. The effects were maintained during the 48-96 weeks of therapy.

Funding

Jiangsu Aidea Pharmaceutical Co., Ltd.

CADD, AI and ML in drug discovery: A comprehensive review

Computer-aided drug design (CADD) is an emerging field that has drawn a lot of interest because of its potential to expedite and lower the cost of the drug development process. Drug discovery research is expensive and time-consuming, and it frequently took 10-15 years for a drug to be commercially available. CADD has significantly impacted this area of research. Further, the combination of CADD with Artificial Intelligence (AI), Machine Learning (ML), and Deep Learning (DL) technologies to handle enormous amounts of biological data has reduced the time and cost associated with the drug development process. This review will discuss how CADD, AI, ML, and DL approaches help identify drug candidates and various other steps of the drug discovery process. It will also provide a detailed overview of the different in silico tools used and how these approaches interact.

Efavirenz: History, Development and Future

Efavirenz (Sustiva^®) is a first-generation non-nucleoside reverse transcriptase inhibitor (NNRTI) used to treat human immunodeficiency virus (HIV) type 1 infection or to prevent the spread of HIV. In 1998, the FDA authorized efavirenz for the treatment of HIV-1 infection. Patients formerly required three 200 mg efavirenz capsules daily, which was rapidly updated to a 600 mg tablet that only required one tablet per day. However, when given 600 mg once daily, plasma efavirenz concentrations were linked not only to poor HIV suppression but also to toxicity. Clinical data suggested that the standard dose of efavirenz could be reduced without compromising its effectiveness, resulting in a reduction in side effects and making the drug more affordable. Therefore, ENCORE1 was performed to compare the efficiency and safeness of a reduced dose of efavirenz (400 mg) with the standard dose (600 mg) plus two NRTI in antiretroviral-naïve HIV-infected individuals. Nowadays, due to the emergence of integrase strand transfer inhibitors (INSTIs), some consider that it is time to stop using efavirenz as a first-line treatment on a global scale, in the parts of the world where that is possible. Efavirenz has been a primary first-line antiviral drug for more than 15 years. However, at this moment, the best use for efavirenz could be for pre-exposure prophylaxis (PrEP) and repurposing in medicine.

Long-term efavirenz exposure induced neuroinflammation and cognitive deficits in C57BL/6 mice

Efavirenz (EFV) is a non-nucleoside reverse transcriptase inhibitor (NNRTI), which is widely used for anti-HIV-1. Evidences revealed that several central nervous system side effects could be observed in mice and patients with administration of EFV. However, the detailed mechanisms are still unknown. In this study, we investigated the effects of long-term EFV treatment on cognitive functions and the potential underlying mechanisms in mice. We maintained C57BL/6 mice aged 2 months with treatment containing 40 or 80 mg/kg/day EFV for 5 months, while control group treated with saline. The cognitive functions were evaluated by novel object recognition test, Barnes maze test and Morris water maze. The results showed significant short-term memory impairment in 40 and 80 mg/kg groups, and notable spatial learning and memory impairments in 80 mg/kg group, without any spontaneous activity alteration. Moreover, EFV induced impairments in dendritic integrity and synaptic plasticity in hippocampus. Furthermore, Significant increases were observed in the expression levels of pro-IL-1β, a similar tendency of TNF-α and phosphorylation of p65 of the 80 mg/kg group compared with control group. These results imply that long-term EFV treatment causes synaptic dysfunction resulting in cognitive deficits, which might be induced by the enhanced pro-inflammatory cytokines IL-1β and TNF-α via activating NF-κB pathway.

Inclusion Compound of Efavirenz and γ-Cyclodextrin: Solid State Studies and Effect on Solubility

Efavirenz is an antiretroviral drug of widespread use in the management of infections with human immunodeficiency virus type 1 (HIV-1). Efavirenz is also used in paediatrics, but due to its very poor aqueous solubility the liquid formulations available resort to oil-based excipients. In this report we describe the interaction of γ-cyclodextrin with efavirenz in solution and in the solid state. In aqueous solution, the preferential host–guest stoichiometry was determined by the continuous variation method using ¹H NMR, which indicated a 3:2 host-to-guest proportion. Following, the solid inclusion compound was prepared at different stoichiometries by co-dissolution and freeze-drying. Solid-state characterisation of the products using FT-IR, ¹³C{¹H} CP-MAS NMR, thermogravimetry, and X-ray powder diffraction has confirmed that the 3:2 stoichiometry is the adequate starting condition to isolate a solid inclusion compound in the pure form. The effect of γ-cyclodextrin on the solubility of efavirenz is studied by the isotherm method.

Recent Advancement in Nanotechnology-Based Drug Delivery System Against Viral Infections

In the last few decades, the exponential rise in the incidence of viral infections sets a global health emergency across the world. The biomimetic architecture, the ability to hijack host immune responses, continuous antigen shifting, and drafting are the major critical factors that are responsible for the unavailability of a concrete therapeutic regimen against viral infections. Further, inappropriate pharmacodynamic physicochemical and biological parameters such as low aqueous solubility, poor permeability, high affinity for plasm proteins, short biological half-lives, and fast elimination from the systemic circulation are the major critical factors that govern the suboptimal drug concentration at the target site that leads to the development of drug resistance. To address this issue, nanotechnology-based drug delivery approach is emerged as an altering method to attain the optimal drug concentration at the target site for a prolonged period by integrating the nanoengineering tools in the synthesis of nanoparticles. Nanodimensional configuration with enhanced permeability and retention effect, increased surface-area-to-volume ratio, provision for surface functionalization, etc., are the privileged aspects that make it an effective drug delivery system for dispensing the antiviral therapeutics. However, size, shape, charge, and surface topology of nanoparticles are the greater influential factors that determine target-specific drug delivery, optimum cellular uptake, degree of opsonization by the host immune cells, drug retention time, transcytosis, the extension of biological half-life, in vivo stability, and cytotoxicity. The review will enlighten the elaborative role of nanotechnology-based drug delivery and the major challenging aspect of clinical safety and efficacy.

Inhibition and induction of CYP enzymes in humans: an update

The cytochrome P450 (CYP) enzyme family is the most important enzyme system catalyzing the phase 1 metabolism of pharmaceuticals and other xenobiotics such as herbal remedies and toxic compounds in the environment. The inhibition and induction of CYPs are major mechanisms causing pharmacokinetic drug–drug interactions. This review presents a comprehensive update on the inhibitors and inducers of the specific CYP enzymes in humans. The focus is on the more recent human in vitro and in vivo findings since the publication of our previous review on this topic in 2008. In addition to the general presentation of inhibitory drugs and inducers of human CYP enzymes by drugs, herbal remedies, and toxic compounds, an in-depth view on tyrosine-kinase inhibitors and antiretroviral HIV medications as victims and perpetrators of drug–drug interactions is provided as examples of the current trends in the field. Also, a concise overview of the mechanisms of CYP induction is presented to aid the understanding of the induction phenomena.

The crosstalk between antiretrovirals pharmacology and HIV drug resistance

INTRODUCTION

The clinical development of antiretroviral drugs has been followed by a rapid and concomitant development of HIV drug resistance. The development and spread of HIV drug resistance is due on the one hand to the within-host intrinsic HIV evolutionary rate and on the other to the wide use of low genetic barrier antiretrovirals.

AREAS COVERED

We searched PubMed and Embase on 31 January 2020, for studies reporting antiretroviral resistance and pharmacology. In this review, we assessed the molecular target and mechanism of drug resistance development of the different antiretroviral classes focusing on the currently approved antiretroviral drugs. Then, we assessed the main pharmacokinetic/pharmacodynamic of the antiretrovirals. Finally, we retraced the history of antiretroviral treatment and its interconnection with antiretroviral worldwide resistance development both in , and middle-income countries in the perspective of 90-90-90 World Health Organization target.

EXPERT OPINION

Drug resistance development is an invariably evolutionary driven phenomenon, which challenge the 90-90-90 target. In high-income countries, the antiretroviral drug resistance seems to be stable since the last decade. On the contrary, multi-intervention strategies comprehensive of broad availability of high genetic barrier regimens should be implemented in resource-limited setting to curb the rise of drug resistance.

Recent Advances in Drug Delivery Strategies for Improved Therapeutic Efficacy of Efavirenz

BACKGROUND

Efavirenz, an anti-HIV agent, has a noticeable place in the HAART regimen for the treatment and maintenance therapy of AIDS. However, its poor water solubility accounts for hindered absorption and bio-distribution upon administration. This results in its low and variable bioavailability. To circumvent these limitations, various novel formulations of Efavirenz have been investigated in order to mitigate its drawbacks and draw out its maximum therapeutic effect.

METHODS

Numerous formulations explored to overcome the drawbacks of Efavirenz include modified/ controlled-release tablets, solid dispersions, polymeric nanoparticles, dendrimers, surface-engineered nanoparticles and various other nanoformulations. Moreover, combinatorial formulations of Efavirenz with other Anti-HIV drugs have also been reported to overcome the problem of Drug-Resistance.

RESULTS

The nanoformulation based strategies, owing to their ability to provide controlled release profile and targeted drug delivery were found to augment bioavailability, therapeutic efficacy and reduce the side effects of the Efavirenz.

CONCLUSION

This review pivots around the challenges and recent advances in the delivery of Efavirenz with particular emphasis on novel formulations including its patents.

Induction of DNA damage and apoptosis in human leukemia cells by efavirenz

As part of the efforts to drug repurposing, some HIV drugs have recently been identified to exert anticancer effects. Selected nucleoside analogues of nucleosidic reverse-transcriptase inhibitors (NRTIs) have been shown to interfere with RNA transcription of HI viruses as well as with the replication of DNA in cancer cells. Non-nucleosidic reverse transcriptase inhibitors (NNRTIs) are believed to have less effects on human DNA replication and, thus, on cancer cell proliferation. Assessment of the effect of the NNRTI efavirenz in human cancer cells, however, revealed a high sensitivity of leukemia cells to this agent at pharmacologically relevant concentrations of less than 10 µg/ml. Cell death induced by efavirenz was caused by apoptosis, as shown by FACScan analysis (Annexin binding) and western blot analysis (cleavage of caspases and PARP). Western blot analyses also revealed a pronounced activation and phosphorylation of the DNA damage marker proteins p53, chk2 and H2AX, indicating DNA replication and genomic integrity as primary targets of efavirenz in leukemia cells.

Efavirenz Causes Oxidative Stress, Endoplasmic Reticulum Stress, and Autophagy in Endothelial Cells

The non-nucleoside reverse transcriptase inhibitor efavirenz is a widely prescribed antiretroviral drug used in combined antiretroviral therapy. Despite being an essential and life-saving medication, the required lifelong use of HIV drugs has been associated with a variety of adverse effects, including disturbances in lipid metabolism and increased cardiovascular risk. Efavirenz belongs to those HIV drugs for which cardiovascular and endothelial dysfunctions have been reported. It is here shown that elevated concentrations of efavirenz can inhibit endothelial meshwork formation on extracellular matrix gels by normal and immortalized human umbilical vein cells. This inhibition was associated with an increase in oxidative stress markers, endoplasmic reticulum (ER) stress markers, and autophagy. Induction of ER stress occurred at pharmacologically relevant concentrations of efavirenz and resulted in reduced proliferation and cell viability of endothelial cells, which worsened in the presence of elevated efavirenz concentrations. In combination with the HIV protease inhibitor nelfinavir, both oxidative stress and ER stress became elevated in endothelial cells. These data indicate that pharmacologically relevant concentrations of efavirenz can impair cell viability of endothelial cells and that these effects may be aggravated by either elevated concentrations of efavirenz or by a combined use of efavirenz with other oxidative stress-inducing medications.

Antiviral Drugs

Viruses are major pathogenic agents causing a variety of serious diseases in humans, other animals, and plants.

Drugs that combat viral infections are called antiviral drugs. There are no effective antiviral drugs for many viral infections. However, there are several drugs for influenza, a couple of drugs for herpesviruses, and some new antiviral drugs for treatment of HIV and hepatitis C infections.

The arsenal of antivirals is complex. As of March 2014, it consists of approximately 50 drugs approved by the FDA, approximately half of which are directed against HIV. Antiviral drug creation strategies are focused on two different approaches: targeting the viruses themselves or targeting host cell factors.

Direct virus-targeting antiviral drugs include attachment inhibitors, entry inhibitors, uncoating inhibitors, protease inhibitors, polymerase inhibitors, nucleoside and nucleotide reverse transcriptase inhibitors, nonnucleoside reverse-transcriptase inhibitors, and integrase inhibitors.

Protease inhibitors (darunavir, atazanavir, and ritonavir), viral DNA polymerase inhibitors (acyclovir, valacyclovir, valganciclovir, and tenofovir), and an integrase inhibitor (raltegravir) are included in the list of Top 200 Drugs by sales for the 2010s.

Use of in vitro to in vivo extrapolation to predict the optimal strategy for patients switching from efavirenz to maraviroc or nevirapine

BACKGROUND AND OBJECTIVES

In clinical practice, antiretroviral regimens are often interrupted or modified for intolerance and toxicity. The objective of this study was to develop an in vitro to in vivo extrapolation (IVIVE) approach to describe the interaction when efavirenz is switched to either maraviroc or nevirapine and to test different switching scenarios to identify the best strategy.

METHODS

In vitro data describing the chemical and absorption, tissue distribution, metabolism and excretion (ADME) characteristics of efavirenz, maraviroc and nevirapine were obtained from the literature, and used to simulate plasma exposures of these drugs using the Simcyp Population-Based Simulator. The predicted maraviroc and nevirapine exposures were compared with data from clinical studies evaluating their exposures following a switch from efavirenz.

RESULTS

Model predictions for maraviroc and nevirapine exposure were in agreement with observed data. The simulations suggest that the waning efavirenz induction effect following discontinuation necessitated increasing maraviroc to 600 mg twice daily for 1 week after efavirenz cessation. Alternatively, adequate exposure of maraviroc was shown with a dose of 450 mg for 2 weeks. Efavirenz waning induction did not affect nevirapine exposure.

CONCLUSION

IVIVE modelling successfully predicted patient drug exposure. This modelling technique is able to inform the design of clinical studies, and allows assessment of pragmatic dosing strategies under complex therapeutic scenarios.

Organic carbamates in drug design and medicinal chemistry

The carbamate group is a key structural motif in many approved drugs and prodrugs. There is an increasing use of carbamates in medicinal chemistry and many derivatives are specifically designed to make drug-target interactions through their carbamate moiety. In this Perspective, we present properties and stabilities of carbamates, reagents and chemical methodologies for the synthesis of carbamates, and recent applications of carbamates in drug design and medicinal chemistry.

Is there a need to increase the dose of efavirenz during concomitant rifampicin-based antituberculosis therapy in sub-Saharan Africa? The HIV-TB pharmagene study

AIMS

The current HIV treatment guidelines are inconsistent about the need for weight-based efavirenz dose adjustment during rifampicin containing antituberculosis (anti-TB) cotreatment. We investigated effect of rifampicin-based anti-TB cotreatment on plasma efavirenz exposure and treatment outcome, considering effect of CYP2B6 genotype and bodyweight.

PATIENTS & METHODS

HIV-only (arm 1, n = 285) or TB-HIV (arm 2, n = 208) coinfected patients were enrolled and received efavirenz-based ART alone or with rifampicin-based anti-TB therapy, respectively. Plasma efavirenz concentrations at 4th and 16th weeks, viral load and CD4 cell count at 24th and 48th weeks were determined.

RESULTS

The mean plasma efavirenz concentration at weeks 4 (p = 0.03) and 16 (p = 0.08) was inconsistently higher in arm 2 than arm 1, mainly in CYP2B6*6 carriers. Effect of bodyweight on efavirenz pharmacokinetics was significant only in arm 1, but not in arm 2. Proportion of patients with nondetectable viral load (≤50 copies/ml) at week 24 was higher in arm 1 than arm 2 patients (91.0 vs 76.3%; p = 0.002), but no significant difference was observed at week 48 (89.5 vs 87.8%; p = 0.22).

CONCLUSION

Rifampicin-based anti-TB cotreatment has no significant influence on long-term efavirenz plasma exposure and efficacy. Hence, there is no need to increase the dose of efavirenz during concomitant rifampicin-based anti-TB cotreatment in the sub-Saharan African population.

Pharmacogenetics of pregnancy-induced changes in efavirenz pharmacokinetics

Pregnancy-induced physiological changes alter many drugs' pharmacokinetics. We investigated pregnancy-induced changes in efavirenz pharmacokinetics in 25 pregnant and 19 different postpartum women stratified from 211 HIV-positive women in whom a preliminary pharmacogenetic study had been undertaken. Despite significant changes in CL/F during pregnancy (42.6% increase; P = 0.023), median (range) Cmin was 1,000 ng/mL (429-5,190) with no significant change in Cmax (P = 0.072). However, when stratified for CYP2B6 516G>T (rs3745274) genotype, efavirenz AUC0-24 , Cmax and Cmin were 50.6% (P = 0.0013), 17.2% (P = 0.14), and 61.6% (P = 0.0027) lower during pregnancy (n = 8) compared with postpartum (n = 6) in 516G homozygotes, with values of 25,900 ng.h/mL (21,700-32,600), 2,640 ng/mL (1,260-3,490), and 592 ng/mL (429-917), respectively, and CL/F was 100% higher (P = 0.0013). No changes were apparent in CYP2B6 516 heterozygotes (14 pregnant vs. 7 postpartum). The clinical implications of these findings warrant further investigation.

Antiretroviral treatment in HIV-1 infected pediatric patients: focus on efavirenz

Efavirenz is a non-nucleoside reverse transcriptase inhibitor (NNRTI), used for the treatment of human immunodeficiency virus (HIV)-1 infection. Approved by the US Food and Drug Administration in 1998, its indication was recently extended to include children as young as 3 months of age. The World Health Organization and many national guidelines consider efavirenz to be the preferred NNRTI for first-line treatment of children over the age of 3 years. Clinical outcomes of patients on three-drug antiretroviral regimens which include efavirenz are as good as or better than those for patients on all other currently approved HIV medications. Efavirenz is dosed once daily and has pediatric-friendly formulations. It is usually well tolerated, with central nervous system side effects being of greatest concern. Efavirenz increases the risk of neural tube defects in nonhuman primates and therefore its use during the first trimester of pregnancy is limited in some settings. With minimal interactions with antituberculous drugs, efavirenz is preferred for use among patients with HIV/tuberculosis coinfection. Efavirenz can be rendered inactive by a single point mutation in the reverse transcriptase enzyme. Newer NNRTI drugs such as etravirine, not yet approved for use in children under the age of 6 years, may maintain their activity following development of efavirenz resistance. This review highlights key points from the existing literature regarding the use of efavirenz in children and suggests directions for future investigation.

Plasma concentrations, efficacy and safety of efavirenz in HIV-infected adults treated for tuberculosis in Cambodia (ANRS 1295-CIPRA KH001 CAMELIA trial)

OBJECTIVE

To assess efavirenz plasma concentrations and their association with treatment efficacy and tolerance of efavirenz 600 mg daily in HIV-tuberculosis co-infected patients.

METHODS

HIV-infected adults with CD4+ T cell count ≤ 200/mm(3) received standard 6-month tuberculosis treatment and antiretroviral therapy including a daily-dose of 600 mg of efavirenz, irrespective of their body weight. Mid-dose blood samples were drawn both on tuberculosis treatment (week +2 and week +6 after antiretroviral therapy initiation, and week 22 of follow-up) and off tuberculosis treatment (week 50 of follow-up). Considered therapeutic range was 1,000 to 4,000 ng/mL. Multivariate analysis was performed to evaluate the association between efavirenz concentration below 1,000 ng/mL and virological failure. Linear regression was used to test the association between efavirenz exposure and CD4+ T cell gain. Severe side effects potentially related to efavirenz were described and their association with efavirenz exposure was tested by multivariate analysis.

RESULTS

Efavirenz plasma concentrations were available in 540 patients. Median [interquartile range] efavirenz concentrations were 2,674 ng/mL [1,690-4,533], 2,667 ng/mL [1,753-4,494] and 2,799 ng/mL [1,804-4,744] at week +2, week +6, week 22, respectively, and 2,766 ng/mL [1,941-3,976] at week 50. Efavirenz concentrations were lower at week 50 (off rifampicin) compared to week 22 (on rifampicin) (p<0.001). Late attendance to study visit and low hemoglobinemia were the only factors associated with an increased risk of efavirenz concentration below 1,000 ng/mL. Efavirenz concentration below 1,000 ng/mL was not associated with treatment failure. Efavirenz concentration above 4,000 ng/mL was associated with higher risk of central nervous system side effects (p<0.001) and of hepatotoxicity (p<0.001).

CONCLUSION

Body weight and tuberculosis treatment were not associated with low efavirenz concentrations or treatment failure, supporting the 600 mg daily-dose of efavirenz in HIV-tuberculosis co-infected patients. High efavirenz concentrations were related to a higher risk of central nervous system side effects and hepatotoxicity.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01300481.

The HIV antiretroviral drug efavirenz has LSD-like properties

Anecdotal reports have surfaced concerning misuse of the HIV antiretroviral medication efavirenz ((4S)-6-chloro-4-(2-cyclopropylethynyl)-4-(trifluoromethyl)-2,4-dihydro-1H-3,1-benzoxazin-2-one) by HIV patients and non-infected teens who crush the pills and smoke the powder for its psychoactive effects. Molecular profiling of the receptor pharmacology of efavirenz pinpointed interactions with multiple established sites of action for other known drugs of abuse including catecholamine and indolamine transporters, and GABAA and 5-HT(2A) receptors. In rodents, interaction with the 5-HT(2A) receptor, a primary site of action of lysergic acid diethylamine (LSD), appears to dominate efavirenz's behavioral profile. Both LSD and efavirenz reduce ambulation in a novel open-field environment. Efavirenz occasions drug-lever responding in rats discriminating LSD from saline, and this effect is abolished by selective blockade of the 5-HT(2A) receptor. Similar to LSD, efavirenz induces head-twitch responses in wild-type, but not in 5-HT(2A)-knockout, mice. Despite having GABAA-potentiating effects (like benzodiazepines and barbiturates), and interactions with dopamine transporter, serotonin transporter, and vesicular monoamine transporter 2 (like cocaine and methamphetamine), efavirenz fails to maintain responding in rats that self-administer cocaine, and it fails to produce a conditioned place preference. Although its molecular pharmacology is multifarious, efavirenz's prevailing behavioral effect in rodents is consistent with LSD-like activity mediated via the 5-HT(2A) receptor. This finding correlates, in part, with the subjective experiences in humans who abuse efavirenz and with specific dose-dependent adverse neuropsychiatric events, such as hallucinations and night terrors, reported by HIV patients taking it as a medication.

In vitro and in vivo activities of AIC292, a novel HIV-1 nonnucleoside reverse transcriptase inhibitor

Nonnucleoside reverse transcriptase inhibitors (NNRTIs) are important and frequently used elements of highly active antiretroviral therapy (HAART) for the treatment of human immunodeficiency virus type 1 (HIV-1) infection. However, the development of drug resistance, as well as the side effects of existing drugs, defines a medical need for novel NNRTIs with excellent tolerability, improved activity against NNRTI-resistant viruses, and a low barrier to resistance. Within the chemical class of diarylpyrazole-[imidazolidinone]-carboxamides, AIC292 was identified as a promising novel HIV-1 NNRTI and has successfully completed single-dose clinical phase I studies. Here, we report on the antiviral activity of AIC292, evaluated in vitro against wild-type and NNRTI-resistant HIV-1 isolates and in vivo using an engineered mouse xenograft model. AIC292 inhibited wild-type HIV-1 laboratory strains at low nanomolar concentrations, was well tolerated in different cell lines, and showed excellent selectivity in a lead profiling screen. In addition, activity of AIC292 could be demonstrated against a broad panel of wild-type HIV-1 group M and group O clinical isolates. AIC292 also retained activity against viruses harboring NNRTI resistance-associated mutations (RAMs), including the most prevalent variants, K103N, Y181C, and G190A. Interestingly, viruses bearing the L100I RAM were hypersusceptible to AIC292. Two-drug combination assays showed no antagonistic interactions between AIC292 and representative marketed HIV drugs with regard to antiviral activity. Furthermore, AIC292 displayed potent antiviral in vivo efficacy in a mouse xenograft model when applied once daily. Taken together, these data show that AIC292 represents a molecule with the antiviral properties of a novel NNRTI for the treatment of HIV-1 infection.

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

INTRODUCTION

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

DISCUSSION

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

CONCLUSIONS

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

Use of a physiologically-based pharmacokinetic model to simulate artemether dose adjustment for overcoming the drug-drug interaction with efavirenz

Purpose

To treat malaria, HIV-infected patients normally receive artemether (80 mg twice daily) concurrently with antiretroviral therapy and drug-drug interactions can potentially occur. Artemether is a substrate of CYP3A4 and CYP2B6, antiretrovirals such as efavirenz induce these enzymes and have the potential to reduce artemether pharmacokinetic exposure. The aim of this study was to develop an in vitro in vivo extrapolation (IVIVE) approach to model the interaction between efavirenz and artemether. Artemether dose adjustments were then simulated in order to predict optimal dosing in co-infected patients and inform future interaction study design.

Methods

In vitro data describing the chemical properties, absorption, distribution, metabolism and elimination of efavirenz and artemether were obtained from published literature and included in a physiologically based pharmacokinetic model (PBPK) to predict drug disposition simulating virtual clinical trials. Administration of efavirenz and artemether, alone or in combination, were simulated to mirror previous clinical studies and facilitate validation of the model and realistic interpretation of the simulation. Efavirenz (600 mg once daily) was administered to 50 virtual subjects for 14 days. This was followed by concomitant administration of artemether (80 mg eight hourly) for the first two doses and 80 mg (twice daily) for another two days.

Results

Simulated pharmacokinetics and the drug-drug interaction were in concordance with available clinical data. Efavirenz induced first pass metabolism and hepatic clearance, reducing artemether C_max by 60% and AUC by 80%. Dose increases of artemether, to correct for the interaction, were simulated and a dose of 240 mg was predicted to be sufficient to overcome the interaction and allow therapeutic plasma concentrations of artemether.

Conclusions

The model presented here provides a rational platform to inform the design for a clinical drug interaction study that may save time and resource while the optimal dose is determined empirically. Wider application of IVIVE could help researchers gain a better understanding of the molecular mechanisms underpinning variability in drug disposition.

Biowaiver monographs for immediate release solid oral dosage forms: efavirenz

Literature data pertaining to the decision to allow a waiver of in vivo bioequivalence testing for the approval of immediate-release (IR) solid oral dosage forms containing efavirenz as the only active pharmaceutical ingredient (API) are reviewed. Because of lack of conclusive data about efavirenz's permeability and its failure to comply with the "high solubility" criteria according to the Biopharmaceutics Classification System (BCS), the API can be classified as BCS Class II/IV. In line with the solubility characteristics, the innovator product does not meet the dissolution criteria for a "rapidly dissolving product." Furthermore, product variations containing commonly used excipients or in the manufacturing process have been reported to impact the rate and extent of efavirenz absorption. Despite its wide therapeutic index, subtherapeutic levels of efavirenz can lead to treatment failure and also facilitate the emergence of efavirenz-resistant mutants. For all these reasons, a biowaiver for IR solid oral dosage forms containing efavirenz as the sole API is not scientifically justified for reformulated or multisource drug products.

Lersivirine, a nonnucleoside reverse transcriptase inhibitor with activity against drug-resistant human immunodeficiency virus type 1

The nonnucleoside reverse transcriptase inhibitors (NNRTIs) are key components of highly active antiretroviral therapy (HAART) for the treatment of human immunodeficiency virus type 1 (HIV-1). A major problem with the first approved NNRTIs was the emergence of mutations in the HIV-1 reverse transcriptase (RT), in particular K103N and Y181C, which led to resistance to the entire class. We adopted an iterative strategy to synthesize and test small molecule inhibitors from a chemical series of pyrazoles against wild-type (wt) RT and the most prevalent NNRTI-resistant mutants. The emerging candidate, lersivirine (UK-453,061), binds the RT enzyme in a novel way (resulting in a unique resistance profile), inhibits over 60% of viruses bearing key RT mutations, with 50% effective concentrations (EC(50)s) within 10-fold of those for wt viruses, and has excellent selectivity against a range of human targets. Altogether lersivirine is a highly potent and selective NNRTI, with excellent efficacy against NNRTI-resistant viruses.

Inhibition of mitochondrial function by efavirenz increases lipid content in hepatic cells

Efavirenz (EFV) is a non-nucleoside reverse transcriptase inhibitor (NNRTI) widely used in human immunodeficiency virus (HIV) infection therapy. It has been associated with hepatotoxic effects and alterations in lipid and body fat composition. Given the importance of the liver in lipid regulation, we have evaluated the effects of clinically used concentrations of EFV on the mitochondria and lipid metabolism of human hepatic cells in vitro. Mitochondrial function was rapidly undermined by EFV to an extent that varied with the concentration employed; in particular, respiration and intracellular adenosine triphosphate (ATP) levels were reduced whereas reactive oxygen species (ROS) production increased. Results in isolated mitochondria suggest that the mechanism responsible for these actions was a specific inhibition of complex I of the respiratory chain. The reduction in energy production triggered a compensatory mechanism mediated by the enzyme adenosine monophosphate-activated protein kinase (AMPK), the master switch of cellular bioenergetics. Fluorescence and nuclear magnetic resonance demonstrated a rapid intracellular increase of neutral lipids, usually in the form of droplets. This was prevented by the AMPK inhibitor compound C and by removal of fatty acids from the culture medium. These effects were not reproduced by Nevirapine, another NNRTI. EFV is clinically coadministered with two nucleoside reverse transcriptase inhibitors. Evaluation of one of the most common combination, EFV/Lamivudine/Abacavir, revealed that the effects of EFV on ROS production were enhanced.

CONCLUSION

Clinical concentrations of EFV induce bioenergetic stress in hepatic cells by acutely inhibiting mitochondrial function. This new mechanism of mitochondrial interference leads to an accumulation of lipids in the cytoplasm that is mediated by activation of AMPK.

Safety and efficacy of raltegravir-based versus efavirenz-based combination therapy in treatment-naive patients with HIV-1 infection: a multicentre, double-blind randomised controlled trial

BACKGROUND

Use of raltegravir with optimum background therapy is effective and well tolerated in treatment-experienced patients with multidrug-resistant HIV-1 infection. We compared the safety and efficacy of raltegravir with efavirenz as part of combination antiretroviral therapy for treatment-naive patients.

METHODS

Patients from 67 study centres on five continents were enrolled between Sept 14, 2006, and June 5, 2008. Eligible patients were infected with HIV-1, had viral RNA (vRNA) concentration of more than 5000 copies per mL, and no baseline resistance to efavirenz, tenofovir, or emtricitabine. Patients were randomly allocated by interactive voice response system in a 1:1 ratio (double-blind) to receive 400 mg oral raltegravir twice daily or 600 mg oral efavirenz once daily, in combination with tenofovir and emtricitabine. The primary efficacy endpoint was achievement of a vRNA concentration of less than 50 copies per mL at week 48. The primary analysis was per protocol. The margin of non-inferiority was 12%. This study is registered with ClinicalTrials.gov, number NCT00369941.

FINDINGS

566 patients were enrolled and randomly allocated to treatment, of whom 281 received raltegravir, 282 received efavirenz, and three were never treated. At baseline, 297 (53%) patients had more than 100 000 vRNA copies per mL and 267 (47%) had CD4 counts of 200 cells per microL or less. The main analysis (with non-completion counted as failure) showed that 86.1% (n=241 patients) of the raltegravir group and 81.9% (n=230) of the efavirenz group achieved the primary endpoint (difference 4.2%, 95% CI -1.9 to 10.3). The time to achieve such viral suppression was shorter for patients on raltegravir than on efavirenz (log-rank test p<0.0001). Significantly fewer drug-related clinical adverse events occurred in patients on raltegravir (n=124 [44.1%]) than those on efavirenz (n=217 [77.0%]; difference -32.8%, 95% CI -40.2 to -25.0, p<0.0001). Serious drug-related clinical adverse events occurred in less than 2% of patients in each drug group.

INTERPRETATION

Raltegravir-based combination treatment had rapid and potent antiretroviral activity, which was non-inferior to that of efavirenz at week 48. Raltegravir is a well tolerated alternative to efavirenz as part of a combination regimen against HIV-1 in treatment-naive patients.

FUNDING

Merck.