Pharmacokinetic interactions between etravirine and non-antiretroviral drugs

Clinical considerations and pharmacokinetic interactions between HIV and tuberculosis therapeutics

INTRODUCTION

Tuberculosis(TB) is a leading infectious diseases cause of mortality worldwide,especially for people living with human immunodeficiency virus(PLWH). Treating TB in PLWH can be challenging due to numerous druginteractions.

AREASCOVERED

Thisreview discusses drug interactions between antitubercular andantiretroviral drugs. Due to its clinical importance, initiation ofantiretroviral therapy in patients requiring TB treatment isdiscussed. Special focus is placed on the rifamycin class, as itaccounts for the majority of interactions. Clinically relevantguidance is provided on how to manage these interactions. Anadditional section on utilizing therapeutic drug monitoring (TDM) tooptimize drug exposure and minimize toxicities is included.

EXPERTOPINION

Antitubercularand antiretroviral coadministration can be successfully managed. TDMcan be used to optimize drug exposure and minimize toxicity risk. Asnew TB and HIV drugs are discovered, additional research will beneeded to assess for clinically relevant drug interactions.

Drug-drug interactions between COVID-19 therapeutics and antiretroviral treatment: the evidence to date

INTRODUCTION

With new effective treatments for SARS-CoV-2, patient outcomes have greatly improved. However, new medications bring a risk of drug interactions with other medications. People living with HIV (PLWH) are at particular risk for these interactions due to heightened risk of immunosuppression, polypharmacy, and overlap in affected organs. It is critical to identify drug interactions are a significant barrier to care for PLWH. Establishing a better understanding of the pharmacologic relationships between COVID-19 therapies and antiretrovirals will improve patient-centered care in COVID-19.

AREAS COVERED

Potential drug-drug interactions between Human Immunodeficiency Virus (HIV) and COVID-19 treatments are detailed and reviewed here. The mechanisms seen in these interactions include alterations in metabolic enzymes, drug transporters, pharmacoenhancement, and organ toxicities. We also review the limitations and solutions that can be used to combat drug-drug interactions between these two disease states.

EXPERT OPINION

While current drug interactions are relatively mild between HIV and COVID-19 therapies, improvements in identifying these beforehand must take place as new therapies are approved. Antiretroviral therapy (ART) is essential in PLWH and must be maintained when treating COVID-19. As advancements in care occur, there is the possibility that newly approved drugs may have additional unknown interactions.

Treatment of Tuberculosis and the Drug Interactions Associated With HIV-TB Co-Infection Treatment

Tuberculosis (TB) is a communicable disease that is a major source of illness, one of the ten causes of mortality worldwide, and the largest cause of death from a single infectious agent Mycobacterium tuberculosis. HIV infection and TB are a fatal combination, with each speeding up the progression of the other. Barriers to integrated treatment as well as safety concerns on the co-management of HIV- TB co-infection do exist. Many HIV TB co-infected people require concomitant anti-retroviral therapy (ART) and anti-TB medication, which increases survival but also introduces certain management issues, such as drug interactions, combined drug toxicities, and TB immune reconstitution inflammatory syndrome which has been reviewed here. In spite of considerable pharmacokinetic interactions between antiretrovirals and antitubercular drugs, when the pharmacological characteristics of drugs are known and appropriate combination regimens, dosing, and timing of initiation are used, adequate clinical response of both infections can be achieved with an acceptable safety profile. To avoid undesirable drug interactions and side effects in patients, anti TB treatment and ART must be closely monitored. To reduce TB-related mortality among HIV-TB co-infected patients, ART and ATT (Anti Tuberculosis Treatment) outcomes must improve. Clinical practise should prioritise strategies to promote adherence, such as reducing treatment duration, monitoring and treating adverse events, and improving treatment success rates, to reduce the mortality risk of HIV-TB co-infection.

Combined study of docking and molecular dynamics against DNV-3 SN1 protein by bixinoids

Dengue (DENV), Zica virus (ZIKV), and Chikungunya fever (CHIK) are tropical diseases that have caused a lot of problems in general worldwide. Transmitted by mosquitoes of the species Aedes aegypti and albopictus, they have not been completely eradicated in the country, and their proliferation has only increased in the Northeast region. Within the structure of the virus, it is possible to verify the presence of glycoprotein SN1, which is responsible for its replication. If this macromolecule is inhibited using a specific or complex linker, it can interrupt its replication activity. An alternative to this problem has been using structures derived from natural products that have pharmacological properties. A dynamic and molecular docking combined study used computational simulation in the four isomeric forms of bixin against the SN1 protein. The Z,E-bixin and E,E-bixin isomers, both with affinity energy -6.7 and -6.5 Kcal/mol, presented the best results. Thus, bixin and its isomers, found in annatto seeds, maybe an initial proposal in the search for prototype compounds to study to fight this lethal virus in the future.Communicated by Ramaswamy H. Sarma.

HIV in pregnancy: Mother-to-child transmission, pharmacotherapy, and toxicity

An estimated 1.3 million pregnant women were living with HIV in 2018. HIV infection is associated with adverse pregnancy outcomes and all HIV-positive pregnant women, regardless of their clinical stage, should receive a combination of antiretroviral drugs to suppress maternal viral load and prevent vertical fetal infection. Although antiretroviral treatment in pregnant women has undoubtedly minimized mother-to-child transmission of HIV, several uncertainties remain. For example, while pregnancy is accompanied by changes in pharmacokinetic parameters, relevant data from clinical studies are lacking. Similarly, long-term adverse effects of exposure to antiretrovirals on fetuses have not been studied in detail. Here, we review current knowledge on HIV effects on the placenta and developing fetus, recommended antiretroviral regimens, and pharmacokinetic considerations with particular focus on placental transport. We also discuss recent advances in antiretroviral research and potential effects of antiretroviral treatment on placental/fetal development and programming.

Clinical Pharmacokinetics and Pharmacodynamics of Etravirine: An Updated Review

Etravirine is a second-generation non-nucleoside reverse transcriptase inhibitor (NNRTI) for the treatment of human immunodeficiency virus type 1 infection. It is a potent inhibitor of HIV reverse transcriptase and retains activity against wild-type and most NNRTI-resistant HIV. The pharmacokinetic profile of etravirine and clinical data support twice-daily dosing, although once-daily dosing has been investigated in treatment-naïve and treatment-experienced persons. Despite similar pharmacokinetic and pharmacodynamic results compared with twice-daily dosing, larger studies are needed to fully support once-daily etravirine dosing in treatment-naïve individuals. Etravirine is reserved for use in third- or fourth-line antiretroviral treatment regimens, as recommended, for example, in treatment guidelines by the US Department of Health and Human Services-Guidelines for the Use of Antiretroviral Agents in Adults and Adolescents Living with HIV. Etravirine exhibits the potential for bi-directional drug-drug interactions with other antiretrovirals and concomitant medications through its interactions with cytochrome P450 (CYP) isozymes: CYP3A4, CYP2C9, and CYP2C19. This review summarizes the pharmacokinetic and pharmacodynamic parameters of etravirine, with particular attention to information on drug-drug interactions and use in special patient populations, including children/adolescents, women, persons with organ dysfunction, and during pregnancy.

Designing Out PXR Activity on Drug Discovery Projects: A Review of Structure-Based Methods, Empirical and Computational Approaches

This perspective discusses the role of pregnane xenobiotic receptor (PXR) in drug discovery and the impact of its activation on CYP3A4 induction. The use of structural biology to reduce PXR activity on drug discovery projects has become more common in recent years. Analysis of this work highlights several important molecular interactions, and the resultant structural modifications to reduce PXR activity are summarized. The computational approaches undertaken to support the design of new drugs devoid of PXR activation potential are also discussed. Finally, the SAR of empirical design strategies to reduce PXR activity is reviewed, and the key SAR transformations are discussed and summarized. In conclusion, this perspective demonstrates that PXR activity can be greatly diminished or negated on active drug discovery projects with the knowledge now available. This perspective should be useful to anyone who seeks to reduce PXR activity on a drug discovery project.

Novel Phenethylamines and Their Potential Interactions With Prescription Drugs: A Systematic Critical Review

BACKGROUND

The novel phenethylamines 4-fluoroamphetamine (4-FA) and 2,5-dimethoxy-4-bromophenethylamine (2C-B) fall in the top 10 most used new psychoactive substances (NPSs) among high-risk substance users. Various phenethylamines and NPS are also highly used in populations with mental disorders, depression, or attention deficit hyperactivity disorder (ADHD). Moreover, NPS use is highly prevalent among men and women with risky sexual behavior. Considering these specific populations and their frequent concurrent use of drugs, such as antidepressants, ADHD medication, and antiretrovirals, reports on potential interactions between these drugs, and phenethylamines 4-FA and 2C-B, were reviewed.

METHODS

The authors performed a systematic literature review on 4-FA and 2C-B interactions with antidepressants (citalopram, fluoxetine, fluvoxamine, paroxetine, sertraline, duloxetine, bupropion, venlafaxine, phenelzine, moclobemide, and tranylcypromine), ADHD medications (atomoxetine, dexamphetamine, methylphenidate, and modafinil), and antiretrovirals.

RESULTS

Limited literature exists on the pharmacokinetics and drug-drug interactions of 2C-B and 4-FA. Only one case report indicated a possible interaction between 4-FA and ADHD medication. Although pharmacokinetic interactions between 4-FA and prescription drugs remain speculative, their pharmacodynamic points toward interactions between 4-FA and ADHD medication and antidepressants. The pharmacokinetic and pharmacodynamic profile of 2C-B also points toward such interactions, between 2C-B and prescription drugs such as antidepressants and ADHD medication.

CONCLUSIONS

A drug-drug (phenethylamine-prescription drug) interaction potential is anticipated, mainly involving monoamine oxidases for 2C-B and 4-FA, with monoamine transporters being more specific to 4-FA.

Pharmacogenomics of Antiretroviral Drug Metabolism and Transport

Antiretroviral therapy has markedly reduced morbidity and mortality for persons living with human immunodeficiency virus (HIV). Individual tailoring of antiretroviral regimens has the potential to further improve the long-term management of HIV through the mitigation of treatment failure and drug-induced toxicities. While the mechanisms underlying anti-HIV drug adverse outcomes are multifactorial, the application of drug-specific pharmacogenomic knowledge is required in order to move toward the personalization of HIV therapy. Thus, detailed understanding of the metabolism and transport of antiretrovirals and the influence of genetics on these pathways is important. To this end, this review provides an up-to-date overview of the metabolism of anti-HIV therapeutics and the impact of genetic variation in drug metabolism and transport on the treatment of HIV. Future perspectives on and current challenges in pursuing personalized HIV treatment are also discussed.

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.

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

INTRODUCTION

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

AREAS COVERED

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

EXPERT OPINION

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

Drug Interactions of Psychiatric and COVID-19 Medications

INTRODUCTION

Coronavirus disease 2019 (COVID-19) has become a pandemic with 1771514 cases identified in the world and 70029 cases in Iran until April 12, 2020. The co-prescription of psychotropics with COVID-19 medication is not uncommon. Healthcare providers should be familiar with many Potential Drug-Drug Interactions (DDIs) between COVID-19 therapeutic agents and psychotropic drugs based on cytochrome P450 metabolism. This review comprehensively summarizes the current literature on DDIs between antiretroviral drugs and chloroquine/hydroxychloroquine, and psychotropics, including antidepressants, antipsychotics, mood stabilizers, and anxiolytics.

METHODS

Medical databases, including Google Scholar, PubMed, Web of Science, and Scopus were searched to identify studies in English with keywords related to psychiatric disorders, medications used in the treatment of psychiatric disorders and COVID-19 medications.

RESULTS

There is a great potential for DDIs between psychiatric and COVID-19 medications ranging from interactions that are not clinically apparent (minor) to those that produce life-threatening adverse drug reactions, or loss of treatment efficacy. The majority of interactions are pharmacokinetic interactions via the cytochrome P450 enzyme system.

CONCLUSION

DDIs are a major concern in the comorbidity of psychiatric disorders and COVID-19 infection resulting in the alteration of expected therapeutic outcomes. The risk of toxicity or lack of efficacy may occur due to a higher or lower plasma concentration of medications. However, psychiatric medication can be safely used in combination with COVID-19 pharmacotherapy with either a wise selection of medication with the least possibility of interaction or careful patient monitoring and management.

Safety implications of combined antiretroviral and anti-tuberculosis drugs

Introduction: Antiretroviral and anti-tuberculosis (TB) drugs are often co-administered in people living with HIV (PLWH). Early initiation of antiretroviral therapy (ART) during TB treatment improves survival in patients with advanced HIV disease. However, safety concerns related to clinically significant changes in drug exposure resulting from drug-drug interactions, development of overlapping toxicities and specific challenges related to co-administration during pregnancy represent barriers to successful combined treatment for HIV and TB.Areas covered: Pharmacokinetic interactions of different classes of ART when combined with anti-TB drugs used for sensitive-, drug-resistant (DR) and latent TB are discussed. Overlapping drug toxicities, implications of immune reconstitution inflammatory syndrome (IRIS), safety in pregnancy and research gaps are also explored.Expert opinion: New antiretroviral and anti-tuberculosis drugs have been recently introduced and international guidelines updated. A number of effective molecules and clinical data are now available to build treatment regimens for PLWH with latent or active TB. Adopting a systematic approach that also takes into account the need for individualized variations based on the available evidence is the key to successfully integrate ART and TB treatment and improve treatment outcomes.

Drug-drug interactions and clinical considerations with co-administration of antiretrovirals and psychotropic drugs

Psychotropic medications are frequently co-prescribed with antiretroviral therapy (ART), owing to a high prevalence of psychiatric illness within the population living with HIV, as well as a 7-fold increased risk of HIV infection among patients with psychiatric illness. While ART has been notoriously associated with a multitude of pharmacokinetic drug interactions involving the cytochrome P450 enzyme system, the magnitude and clinical impact of these interactions with psychotropics may range from negligible effects on plasma concentrations to life-threatening torsades de pointes or respiratory depression. This comprehensive review summarizes the currently available information regarding drug-drug interactions between antiretrovirals and pharmacologic agents utilized in the treatment of psychiatric disorders-antidepressants, stimulants, antipsychotics, anxiolytics, mood stabilizers, and treatments for opioid use disorder and alcohol use disorder-and provides recommendations for their management. Additionally, overlapping toxicities between antiretrovirals and the psychotropic classes are highlighted. Knowledge of the interaction and adverse effect potential of specific antiretrovirals and psychotropics will allow clinicians to make informed prescribing decisions to better promote the health and wellness of this high-risk population.

Getting to the Heart of the Matter: A Review of Drug Interactions Between HIV Antiretrovirals and Cardiology Medications

The past 20 years have seen remarkable advances in the treatment of HIV such that most people diagnosed with HIV today can live long, healthy lives by taking antiretrovirals which are usually life-long. Advancements in antiretroviral therapy include the availability of well tolerated, single tablet regimens that are associated with a lower risk of drug-drug interactions. Despite this, many people living with HIV infection might be taking antiretroviral agents that are associated with significant drug-drug interactions. Because HIV infection itself is associated with cardiovascular complications and this population is living longer, concomitant use of antiretrovirals and medications to treat cardiovascular-related diseases is often required. For this reason, it is imperative that clinicians are aware of the potential for clinically significant drug-drug interactions between antiretroviral agents and cardiac medications as well as the useful HIV drug interaction resources that might provide guidance. Available data on significant interactions are summarized and suggested guidance regarding management is discussed.

HIV status and type of coronary stent placed in patients presenting with ST-elevation myocardial infarction

BACKGROUND

Drug-eluting stents (DES) outperform bare-metal stents (BMS) in reducing target vessel revascularization following a percutaneous coronary intervention (PCI). Little is known about the types of stents placed in HIV-positive patients presenting with ST-segment elevation myocardial infarctions (STEMIs).

METHODS

We used the 2003-2013 National Inpatient Sample to identify adults of 18 years or older presenting with STEMI. We evaluated differences in stent type placed following STEMIs on the basis of HIV status. Temporal trends in the use of PCI, DES, and BMS were studied on the basis of HIV status.

RESULTS

Of 1 695 947 patients with STEMI, 5887 (0.3%) were HIV-positive patients. Following STEMIs, HIV-positive patients were equally likely to have PCI compared with HIV-negative patients [adjusted odds ratio (AOR): 1.04, 95% confidence interval (CI): 0.89-1.21, P=0.63]. However, HIV-positive patients were less likely to have DES (AOR: 0.83, 95% CI: 0.73-0.94, P=0.003) and more likely to have BMS (AOR: 1.26, 95% CI: 1.11-1.45, P=0.001). Over the 11-year period observed, there were increases in PCI following STEMIs in both HIV-positive and HIV-negative patients (all Ptrend<0.001). There were significant increases in the use of DES in HIV-negative patients [adjusted odds ratio (AOR) per year: 1.07, 95% CI: 1.06-1.09, Ptrend<0.001] and significant decreases in the use of BMS (AOR per year: 0.93, 95% CI: 0.92-0.94, Ptrend<0.001). Significant trends showing changed practice patterns in the use of DES and BMS among HIV-positive patients were not observed.

CONCLUSION

Over a decade, there were significant increases in the use of PCI following STEMIs in both HIV-negative and HIV-positive patients. Although HIV-positive patients presenting with STEMIs were as likely as HIV-negative patients to undergo PCI, they were less likely to be treated with DES and more likely to receive BMS. Highlighting these observations will hopefully bring renewed attention to best practices for all STEMI patients.

Evaluation of Concomitant Antiretrovirals and CYP2C9/CYP2C19 Polymorphisms on the Pharmacokinetics of Etravirine

BACKGROUND

Etravirine is a non-nucleoside reverse transcriptase inhibitor indicated in combination with other antiretrovirals for treatment-experienced HIV patients ≥6 years of age. Etravirine is primarily metabolized by cytochrome P450 (CYP) 2C9, CYP2C19, and CYP3A. This analysis determined the impact of concomitant antiretrovirals and CYP2C9/CYP2C19 phenotype on the pharmacokinetics of etravirine.

METHODS

We used 4728 plasma concentrations from 817 adult subjects collected from four clinical studies to develop the population pharmacokinetic model. The presence of atazanavir/ritonavir, lopinavir/ritonavir, darunavir/ritonavir, tenofovir disoproxil fumarate, or enfuvirtide together with the CYP2C9 and CYP2C19 phenotype and other demographics were evaluated.

RESULTS

A one-compartment model with first-order input and a lag-time best described the data. Estimates of apparent total clearance (CL/F), apparent central volume of distribution (V _c/F), first-order absorption rate constant (k _a), and absorption lag-time were 41.7 L/h, 972 L, 1.16 h, and 1.32 h, respectively. Estimates of between-subject variability on CL/F, V _c/F, and relative bioavailability (F) were 39.4 %CV (percentage coefficient of variation), 35.9 %CV and 35.5 %CV, respectively. Between-occasion variability on F was estimated to be 30.0 %CV. CL/F increased non-linearly with body weight and creatinine clearance (CL_CR), and also varied based on CYP2C9/CYP2C19 phenotype.

CONCLUSIONS

In this analysis, body weight, CL_CR, and CYP2C9/CYP2C19 phenotype were found to describe some of the variability in CL/F. It was not possible to show an impact of concomitant antiretrovirals on the pharmacokinetics of etravirine for adults predominantly taking coadministered boosted protease inhibitors as a background antiretroviral regimen.

Recommendations for Managing Drug-Drug Interactions with Statins and HIV Medications

The discovery of antiretroviral therapy (ART) for the treatment of human immunodeficiency virus (HIV) has enabled individuals to live longer. As a result, HIV is now often considered a chronic condition. However, as a result of the increase in longevity or the HIV treatment modalities themselves, individuals with HIV are at high risk for the development of atherosclerotic cardiovascular disease. Therefore, these patients should be optimized with pharmacologic therapy to lower their cardiovascular risk through the addition of statin therapy to their regimen. Unfortunately, many medications utilized to treat HIV interact with this class of agents, making prescribing of statin therapy in these patients challenging. While several classes of ARTs do not pose an increased risk of drug-drug interactions with statins, HIV treatment often requires several combinations of medications, enhancing the complexity and drug-drug interaction risk. Clinicians should be aware of interactions with statins and ART and carefully review the degree and clinical significance of each particular medication. With this understanding, the appropriate statin as well as statin dose can be selected in order to optimize the treatment of this patient population, while minimizing the potential risk of adverse effects.

Addressing Antiretroviral Therapy-Associated Drug-Drug Interactions in Patients Requiring Treatment for Opportunistic Infections in Low-Income and Resource-Limited Settings

An increasing number of human immunodeficiency virus (HIV)-infected patients are achieving virologic suppression on antiretroviral therapy (ART) limiting the use of primary and secondary antimicrobial prophylaxis. However, in low-income and resource-limited settings, half of those infected with HIV are unaware of their diagnosis, and fewer than 50% of patients on ART achieve virologic suppression. Management of comorbidities and opportunistic infections among patients on ART may lead to inevitable drug-drug interactions (DDIs) and even toxicities. Elderly patients, individuals with multiple comorbidities, those receiving complex ART, and patients living in low-income settings experience higher rates of DDIs. Management of these cytochrome P450-mediated, nonmediated, and drug transport system DDIs is critical in HIV-infected patients, particularly those in resource-limited settings with few options for ART. This article critically analyzes and provides recommendations to manage significant DDIs and drug toxicities in HIV-infected patients receiving ART.

Pharmacokinetics and Pharmacokinetic/Pharmacodynamic Relationships of Etravirine in HIV-1-Infected, Treatment-Experienced Children and Adolescents in PIANO

PIANO (NCT00665847) investigated etravirine pharmacokinetics, efficacy, and safety in children and adolescents. Treatment-experienced, HIV-1-infected patients (≥6 to <18 years) received etravirine 5.2 mg/kg twice daily (maximum 200 mg twice daily) plus background antiretrovirals. A population pharmacokinetic model was developed, and etravirine C_0h and AUC_0-12h were estimated. Relationships among intrinsic/extrinsic factors and etravirine pharmacokinetics and pharmacokinetics with pharmacodynamics were assessed. The best model describing etravirine pharmacokinetics consisted of a single compartment with sequential zero- and first-order absorption following a lag time. Interindividual variability terms were included on clearance (CL/F) and the first-order input rate constant (KA). The final model estimates (coefficient of variation, %) for CL/F and KA were 46.3 (11) L/h and 1.07 (34) h^-1 , respectively. Overall, median (range) estimated etravirine C_0h and AUC_0-12h were 287 (2-2276) ng/mL and 4560 (62-28,865) ng · h/mL, respectively. Exposure was slightly lower in adolescents vs children. Sex and adherence did not affect etravirine pharmacokinetics. Factors significantly affecting etravirine exposure were body weight (higher with lower weight), race (lower in Asians than in white or black patients), and the use of certain HIV protease inhibitors. Virologic response (<50 copies/mL at week 48) was lower in the lowest etravirine AUC_0-12h quartile vs the upper 3 quartiles (41% vs 67% to 76%). Rash occurred more frequently in the highest quartile than in the lower 3 quartiles (52% versus 8% to 20%). Etravirine 5.2 mg/kg twice daily in treatment-experienced, HIV-1-infected children and adolescents provides comparable exposure to that in adults receiving etravirine 200 mg twice daily and is the recommended dose for children and adolescents.

Dual Raltegravir-Etravirine Combination as Maintenance Regimen in Virologically Suppressed HIV-1-Infected Patients

Nucleoside reverse transcriptase inhibitor (NRTI)- and protease inhibitor (PI)-sparing antiretroviral regimens may be useful in selected human immune deficiency virus (HIV)-infected patients with resistance or intolerance to these drug classes. This was an observational prospective study of patients on suppressive antiretroviral therapy containing two NRTIs plus one ritonavir-boosted PI who switched to a dual regimen containing raltegravir plus etravirine. Patients were required not to have prior virological failure to raltegravir and to have efficacy of etravirine shown through the genotypic resistance assay in case of prior non-nucleoside reverse transcriptase inhibitor (NNRTI) virological failure. As a whole, 38 patients were enrolled. The mean duration of current regimen was 4.3 years, and the reason for simplification was toxicity in 29 patients and resistance to NRTIs in 9 patients. After switching, the percentage of patients with HIV RNA <20 copies/ml at week 48 was 81.6% in the intent-to-treat-exposed analysis. The switch led to a significant reduction in the mean serum triglyceride levels (-81.2 mg/dl), in the mean total cholesterol levels (-44.3 mg/dl), and in the prevalence of tubular proteinuria (-30.2%), with a significant increase in the mean phosphoremia (+0.52 mg/dl) and in both mean lumbar and femoral neck bone mineral density (+6.5% and +4.7%, respectively). Two patients (5.2%) had virological failure due to suboptimal adherence, and five subjects (13.1%) discontinued treatment due to adverse events. In our study, simplification to the dual-therapy raltegravir plus etravirine was associated with a good efficacy and tolerability, in addition to a favorable effect on kidney, bone, and serum lipids.

Critical Review: What Dose of Rifabutin Is Recommended With Antiretroviral Therapy?

Since the advent of combination antiretroviral therapy to successfully treat HIV infection, drug-drug interactions (DDIs) have become a significant problem as many antiretrovirals (ARVs) are metabolized in the liver. Antituberculous therapy traditionally includes rifamycins, particularly rifampicin. Rifabutin (RBT) has shown similar efficacy as rifampicin but induces CYP3A4 to a lesser degree and is less likely to have DDIs with ARVs. We identified 14 DDI pharmacokinetic studies on HIV monoinfected and HIV-tuberculosis coinfected individuals, and the remaining studies were healthy volunteer studies. Although RBT may be coadministered with most nonnucleoside reverse transcriptase inhibitors, identifying the optimal dose with ritonavir-boosted or cobicistat-boosted protease inhibitors is challenging because of concern about adverse effects with increased RBT exposure. Limited healthy volunteer studies on other ARV drug classes and RBT suggest that dose modification may be unnecessary. The paucity of data assessing clinical tuberculosis endpoints concurrently with RBT and ARV pharmacokinetics limits evidence-based recommendations on the optimal dose of RBT within available ARV drug classes.

The pharmacological challenges of treating tuberculosis and HIV coinfections

INTRODUCTION

Tuberculosis (TB) is the most prevalent opportunistic infection among HIV patients, and the leading cause of death among HIV patients worldwide. Simultaneous treatment of both diseases is recommended by current guidelines, but can be challenging due to the potential for drug-drug interactions, overlapping toxicities, difficulty adhering to medications, and an increased risk for immune reconstitution inflammatory syndrome (IRIS). Clinical manifestations of TB can also vary between HIV-infected patients and uninfected patients, which can increase the risk for delayed diagnosis. Areas covered: Topics covered in this review include the following: the inter-related pathophysiology of HIV and TB; clinical manifestations and diagnosis; drug-drug interactions, particularly the rifamycins with the antiretrovirals; IRIS presentation and treatment, as well as a discussion on overlapping toxicity between the two disease states. Expert commentary: The complexity of managing these two disease states simultaneously requires a multidisciplinary approach to care and dedicated resources. If properly funded, TB/HIV co-infection will continue to decline over the coming years.

Current trends and intricacies in the management of HIV-associated pulmonary tuberculosis

Human immunodeficiency virus (HIV) epidemic has undoubtedly increased the incidence of tuberculosis (TB) globally, posing a formidable global health challenge affecting 1.2 million cases. Pulmonary TB assumes utmost significance in the programmatic perspective as it is readily transmissible as well as easily diagnosable. HIV complicates every aspect of pulmonary tuberculosis from diagnosis to treatment, demanding a different approach to effectively tackle both the diseases. In order to control these converging epidemics, it is important to diagnose early, initiate appropriate therapy for both infections, prevent transmission and administer preventive therapy. Liquid culture methods and nucleic acid amplification tests for TB confirmation have replaced conventional solid media, enabling quicker and simultaneous detection of mycobacterium and its drug sensitivity profile Unique problems posed by the syndemic include Acquired rifampicin resistance, drug-drug interactions, malabsorption of drugs and immune reconstitution inflammatory syndrome or paradoxical reaction that complicate dual and concomitant therapy. While the antiretroviral therapy armamentarium is constantly reinforced by discovery of newer and safer drugs every year, only a few drugs for anti tuberculosis treatment have successfully emerged. These include bedaquiline, delamanid and pretomanid which have entered phase III B trials and are also available through conditional access national programmes. The current guidelines by WHO to start Antiretroviral therapy irrespective of CD4+ cell count based on benefits cited by recent trials could go a long way in preventing various complications caused by the deadly duo. This review provides a consolidated gist of the advancements, concepts and updates that have emerged in the management of HIV-associated pulmonary TB for maximizing efficacy, offering latest solutions for tackling drug-drug interactions and remedial measures for immune reconstitution inflammatory syndrome.

Integrated therapy for HIV and tuberculosis

Tuberculosis (TB) has been the most common opportunistic infection and cause of mortality among HIV-infected patients, especially in resource-limited countries. Clinical manifestations of TB vary and depend on the degree of immunodeficiency. Sputum microscopy and culture with drug-susceptibility testing are recommended as a standard method for diagnosing active TB. TB-related mortality in HIV-infected patients is high especially during the first few months of treatment. Integrated therapy of both HIV and TB is feasible and efficient to control the diseases and yield better survival. Randomized clinical trials have shown that early initiation of antiretroviral therapy (ART) improves survival of HIV-infected patients with TB. A delay in initiating ART is common among patients referred from TB to HIV separate clinics and this delay may be associated with increased mortality risk. Integration of care for both HIV and TB using a single facility and a single healthcare provider to deliver care for both diseases is a successful model. For TB treatment, HIV-infected patients should receive at least the same regimens and duration of TB treatment as HIV-uninfected patients. Currently, a 2-month initial intensive phase of isoniazid, rifampin, pyrazinamide, and ethambutol, followed by 4 months of continuation phase of isoniazid and rifampin is considered as the standard treatment of drug-susceptible TB. ART should be initiated in all HIV-infected patients with TB, irrespective of CD4 cell count. The optimal timing to initiate ART is within the first 8 weeks of starting antituberculous treatment and within the first 2 weeks for patients who have CD4 cell counts <50 cells/mm(3). Non-nucleoside reverse transcriptase inhibitor (NNRTI)-based ART remains a first-line regimen for HIV-infected patients with TB in resource-limited settings. Although a standard dose of both efavirenz and nevirapine can be used, efavirenz is preferred because of more favorable treatment outcomes. In the settings where raltegravir is accessible, doubling the dose to 800 mg twice daily is recommended. Adverse reactions to either antituberculous or antiretroviral drugs, as well as immune reconstitution inflammatory syndrome, are common in patients receiving integrated therapy. Early recognition and appropriate management of these consequences can reinforce the successful integrated therapy in HIV-infected patients with TB.

Pharmacokinetic interaction between etravirine or rilpivirine and telaprevir in healthy volunteers: A randomized, two-way crossover trial

Coinfection with human immunodeficiency virus (HIV) and hepatitis C virus (HCV) may require treatment with an HIV non-nucleoside reverse transcriptase inhibitor (NNRTI), for example, rilpivirine or etravirine, and an HCV direct-acting antiviral drug such as telaprevir. In a two-panel, two-way, crossover study, healthy volunteers were randomized to receive etravirine 200 mg twice daily ± telaprevir 750 mg every 8 hours or rilpivirine 25 mg once daily ± telaprevir 750 mg every 8 hours. Pharmacokinetic assessments were conducted for each drug at steady-state when given alone and when coadministered; statistical analyses were least-square means with 90% confidence intervals. Telaprevir minimum plasma concentration (Cmin), maximum plasma concentration (Cmax), and area under the concentration-time curve (AUC) decreased 25%, 10%, and 16%, respectively, when coadministered with etravirine and 11%, 3%, and 5%, respectively, when coadministered with rilpivirine. Telaprevir did not affect etravirine pharmacokinetics, but increased rilpivirine Cmin, Cmax, and AUC by 93%, 49%, and 78%, respectively. Both combinations were generally well tolerated. The small decrease in telaprevir exposure when coadministered with etravirine is unlikely to be clinically relevant. The interaction between telaprevir and rilpivirine is not likely to be clinically relevant under most circumstances. No dose adjustments are deemed necessary when they are coadministered.

Pharmacological interactions between rifampicin and antiretroviral drugs: challenges and research priorities for resource-limited settings

Coadministration of antituberculosis and antiretroviral therapy is often inevitable in high-burden countries where tuberculosis (TB) is the most common opportunistic infection associated with HIV/AIDS. Concurrent use of rifampicin and many antiretroviral drugs is complicated by pharmacokinetic drug-drug interactions. Rifampicin is a very potent enzyme inducer, which can result in subtherapeutic antiretroviral drug concentrations. In addition, TB drugs and antiretroviral drugs have additive (pharmacodynamic) interactions as reflected in overlapping adverse effect profiles. This review provides an overview of the pharmacological interactions between rifampicin-based TB treatment and antiretroviral drugs in adults living in resource-limited settings. Major progress has been made to evaluate the interactions between TB drugs and antiretroviral therapy; however, burning questions remain concerning nevirapine and efavirenz effectiveness during rifampicin-based TB treatment, treatment options for TB-HIV-coinfected patients with nonnucleoside reverse transcriptase inhibitor resistance or intolerance, and exact treatment or dosing schedules for vulnerable patients including children and pregnant women. The current research priorities can be addressed by maximizing the use of already existing data, creating new data by conducting clinical trials and prospective observational studies and to engage a lobby to make currently unavailable drugs available to those most in need.

Treatment optimization in patients co-infected with HIV and Mycobacterium tuberculosis infections: focus on drug-drug interactions with rifamycins

Tuberculosis (TB) and HIV continue to be two of the major causes of morbidity and mortality in the world, and together are responsible for the death of millions of people every year. There is overwhelming evidence to recommend that patients with TB and HIV co-infection should receive concomitant therapy of both conditions regardless of the CD4 cell count level. The principles for treatment of active TB disease in HIV-infected patients are the same as in HIV-uninfected patients. However, concomitant treatment of both conditions is complex, mainly due to significant drug-drug interactions between TB and HIV drugs. Rifamycins are potent inducers of the cytochrome P450 (CYP) pathway, leading to reduced (frequently sub-therapeutic) plasma concentrations of some classes of antiretrovirals. Rifampicin is also an inducer of the uridine diphosphate glucuronosyltransferase (UGT) 1A1 enzymes and interferes with drugs, such as integrase inhibitors, that are metabolized by this metabolic pathway. Rifampicin is also an inducer of the adenosine triphosphate (ATP) binding cassette transporter P-glycoprotein, which may also lead to decreased bioavailability of concomitantly administered antiretrovirals. On the other side, rifabutin concentrations are affected by the antiretrovirals that induce or inhibit CYP enzymes. In this review, the pharmacokinetic interactions, and the relevant clinical consequences, of the rifamycins-rifampicin, rifabutin, and rifapentine-with antiretroviral drugs are reviewed and discussed. A rifampicin-based antitubercular regimen and an efavirenz-based antiretroviral regimen is the first choice for treatment of TB/HIV co-infected patients. Rifabutin is the preferred rifamycin to use in HIV-infected patients on a protease inhibitor-based regimen; however, the dose of rifabutin needs to be reduced to 150 mg daily. More information is required to select optimal treatment regimens for TB/HIV co-infected patients whenever efavirenz cannot be used and rifabutin is not available. Despite significant pharmacokinetic interactions between antiretrovirals and antitubercular drugs, adequate clinical response of both infections can be achieved with an acceptable safety profile when the pharmacological characteristics of drugs are known, and appropriate combination regimens, dosing, and timing of initiation are used. However, more clinical research is needed for newer drugs, such as rifapentine and the recently introduced integrase inhibitor antiretrovirals, and for specific population groups, such as children, pregnant women, and patients affected by multidrug-resistant TB.

Efficacy and pharmacokinetics of the combination of etravirine plus raltegravir as novel dual antiretroviral maintenance regimen in HIV-infected patients

Novel combination antiretroviral regimens may be needed for selected HIV-infected patients with toxicity or resistance. We evaluated prospectively 25 virologically suppressed patients, largely pretreated (15.6 years on therapy) with antiretroviral drug toxicity (n=19) or interactions (n=9, mainly with chemotherapy against non-Hodgkin lymphoma or anti-HCV therapy), who switched to a dual therapy with etravirine (ETR) plus raltegravir (RAL). Patients were required not to have prior virological failure or resistance to both drugs. After a median follow up of 722 days (473-1088: 53.3 patients-year), there were no cases of transient virological replication or failure. Only 1 patient left therapy at day 10 due to a grade 2 rash, and therefore efficacy by intent-to-treat analysis was 96% at 48 weeks. There were no cases of liver toxicity grade 3-4, and total cholesterol (TC) and triglycerides (TG) levels decrease significantly after initiation (TC, -17 mg/dl; p=0.01; TG, -42 mg/dl; p=0.01), as well as the TC/High density lipoprotein-cholesterol ratio (from 4.35 to 4.28). Geometric mean plasma trough level of RAL was 166 ng/ml (IQR, 40-249), well above the inhibitory concentration 90 (IC(90)). In conclusion, a novel dual therapy with ETR plus RAL is effective and well tolerated, and it could be an option to maintain durable viral suppression in hard-to-treat HIV-infected patients.

Management of tuberculosis and latent tuberculosis infection in human immunodeficiency virus-infected persons

The syndemic of human immunodeficiency virus (HIV)/tuberculosis (TB) co-infection has grown as a result of the considerable sociogeographic overlaps between the two epidemics. The situation is particularly worrisome in countries with high or intermediate TB burden against the background of a variable HIV epidemic state. Early diagnosis of TB disease in an HIV-infected person is paramount but suffers from lack of sensitive and specific diagnostic tools. Enhanced symptom screening is currently advocated, and the wide application of affordable molecular diagnostics is urgently needed. Treatment of TB/HIV co-infection involves the concurrent use of standard antiretrovirals and antimycobacterials during which harmful drug interaction may occur. The pharmacokinetic interaction between rifamycin and antiretrovirals is a case in point, requiring dosage adjustment and preferential use of rifabutin, if available. Early initiation of antiretroviral therapy is indicated, preferably at 2 weeks after starting TB treatment for patients with a CD4 of <50 cells/μL. Development of TB-immune reconstitution inflammatory syndrome (TB-IRIS) is however more frequent with early antiretroviral therapy. The diagnosis of TB-IRIS is another clinical challenge, and cautious use of corticosteroids is suggested to improve clinical outcome. As a preventive measure against active TB disease, the screening for latent TB infection should be widely practiced, followed by at least 6-9 months of isoniazid treatment. To date tuberculin skin test remains the only diagnostic tool in high TB burden countries. The role of alternative tests, for example, interferon-γ release assay, would need to be better defined for clinical application.

Clinical and virological efficacy of etravirine plus two active Nucleos(t)ide analogs in an heterogeneous HIV-infected population

Etravirine (ETV) is recommended in combination with a boosted protease inhibitor plus an optimized background regimen for salvage therapy, but there is limited experience with its use in combination with two nucleos(t)ide reverse-transcriptase inhibitors (NRTIs). This multicenter study aimed to assess the efficacy of this combination in two scenarios: group A) subjects without virologic failure on or no experience with non-nucleoside reverse-transcriptase inhibitors (NNRTIs) switched due to adverse events and group B) subjects switched after a virologic failure on an efavirenz- or nevirapine-based regimen. The primary endpoint was efficacy at 52 weeks analysed by intention-to-treat. Virologic failure was defined as the inability to suppress plasma HIV-RNA to <50 copies/mL after 24 weeks on treatment, or a confirmed viral load >200 copies/mL in patients who had previously achieved a viral suppression or had an undetectable viral load at inclusion. Two hundred eighty seven patients were included. Treatment efficacy rates in group A and B were 88.0% (CI_95, 83.9–92.1%) and 77.4% (CI₉₅, 65.0–89.7%), respectively; the rates reached 97.2% (CI₉₅, 95.1–99.3%) and 90.5% (CI₉₅, 81.7–99.3), by on-treatment analysis. The once-a-day ETV treatment was as effective as the twice daily dosing regimen. Grade 1–2 adverse events were observed motivating a treatment switch in 4.2% of the subjects. In conclusion, ETV (once- or twice daily) plus two analogs is a suitable, well-tolerated combination both as a switching strategy and after failure with first generation NNRTIs, ensuring full drug activity.

Trial registration

ClinicalTrials.gov NCT01437241

Drug Interactions Between Antiplatelet or Novel Oral Anticoagulant Medications and Antiretroviral Medications

Objective: To review potential drug interactions between antiretroviral (ARV) medications and antiplatelets or novel oral anticoagulants (NOACs). Data Sources: A literature search of MEDLINE, PubMed, EMBASE, International Pharmaceutical Abstracts, and Google Scholar was performed using the search terms (1) clopidogrel or ticagrelor or prasugrel, (2) dabigatran or rivaroxaban or apixaban, and (3) antiretrovirals. Study Selection and Data Extraction: Any English language study or case report describing a drug interaction between an ARV and an antiplatelet or NOAC was included. Additional information was taken from pharmacokinetic studies of individual agents alone or information from similar drug interactions. Results: Two studies were identified through the literature search: one reporting an in vivo interaction between ritonavir and prasugrel and the other an in vitro interaction between efavirenz and clopidogrel. A case report describing a drug interaction between nevirapine and rivaroxaban was also located. Information from pharmacokinetic studies and from similar drug interactions allowed for a comprehensive review of potential drug interactions. Conclusions: There are potential drug interactions between ARVs, antiplatelet agents or NOACs. Management of these interactions may include selecting ARVs with a lower potential for drug interactions or choosing antiplatelet agents or NOACs least likely to interact with ARVs. With protease inhibitors or cobicistat, clopidogrel and dabigatran do not appear to have clinically significant interactions. Nonnucleoside reverse transcriptase inhibitors have a low potential for interactions with prasugrel and dabigatran. Clinically significant drug interactions are unlikely to occur between antiplatelet agents or NOACs and nucleoside reverse transcriptase inhibitors raltegravir, dolutegravir, or maraviroc.

[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.

PXR antagonists and implication in drug metabolism

Adopted orphan nuclear receptor (NR), pregnane X receptor (PXR), plays a central role in the regulation of xeno- and endobiotic metabolism. Since the discovery of the functional role of PXR in 1998, there is evolving evidence for the role of PXR agonists in abrogating metabolic pathophysiology (e.g., cholestasis, hypercholesterolemia, and inflammation). However, more recently, it is clear that PXR is also an important mediator of adverse xeno- (e.g., enhances acetaminophen toxicity) and endobiotic (e.g., hepatic steatosis) metabolic phenotypes. Moreover, in cancer therapeutics, PXR activation can induce drug resistance, and there is growing evidence for tissue-specific enhancement of the malignant phenotype. Thus, in these instances, there may be a role for PXR antagonists. However, as opposed to the discovery efforts for PXR agonists, there are only a few antagonists described. The mode of action of these antagonists (e.g., sulforaphane) remains less clear. Our laboratory efforts have focused on this question. Since the original discovery of azoles analogs as PXR antagonists, we have preliminarily defined an important PXR antagonist pharmacophore and developed less-toxic PXR antagonists. In this review, we describe our published and unpublished findings on recent structure-function studies involving the azole chemical scaffold. Further work in the future is needed to fully define potent, more-selective PXR antagonists that may be useful in clinical application.

Pharmacogenetics-based population pharmacokinetic analysis of etravirine in HIV-1 infected individuals

OBJECTIVES

Etravirine (ETV) is metabolized by cytochrome P450 (CYP) 3A, 2C9, and 2C19. Metabolites are glucuronidated by uridine diphosphate glucuronosyltransferases (UGT). To identify the potential impact of genetic and non-genetic factors involved in ETV metabolism, we carried out a two-step pharmacogenetics-based population pharmacokinetic study in HIV-1 infected individuals.

MATERIALS AND METHODS

The study population included 144 individuals contributing 289 ETV plasma concentrations and four individuals contributing 23 ETV plasma concentrations collected in a rich sampling design. Genetic variants [n=125 single-nucleotide polymorphisms (SNPs)] in 34 genes with a predicted role in ETV metabolism were selected. A first step population pharmacokinetic model included non-genetic and known genetic factors (seven SNPs in CYP2C, one SNP in CYP3A5) as covariates. Post-hoc individual ETV clearance (CL) was used in a second (discovery) step, in which the effect of the remaining 98 SNPs in CYP3A, P450 cytochrome oxidoreductase (POR), nuclear receptor genes, and UGTs was investigated.

RESULTS

A one-compartment model with zero-order absorption best characterized ETV pharmacokinetics. The average ETV CL was 41 (l/h) (CV 51.1%), the volume of distribution was 1325 l, and the mean absorption time was 1.2 h. The administration of darunavir/ritonavir or tenofovir was the only non-genetic covariate influencing ETV CL significantly, resulting in a 40% [95% confidence interval (CI): 13-69%] and a 42% (95% CI: 17-68%) increase in ETV CL, respectively. Carriers of rs4244285 (CYP2C19*2) had 23% (8-38%) lower ETV CL. Co-administered antiretroviral agents and genetic factors explained 16% of the variance in ETV concentrations. None of the SNPs in the discovery step influenced ETV CL.

CONCLUSION

ETV concentrations are highly variable, and co-administered antiretroviral agents and genetic factors explained only a modest part of the interindividual variability in ETV elimination. Opposing effects of interacting drugs effectively abrogate genetic influences on ETV CL, and vice-versa.

Etravirine for the treatment of HIV/AIDS

INTRODUCTION

Etravirine (TMC125) is an orally administered second-generation non-nucleoside reverse transcriptase inhibitor (NNRTI) that is approved in treatment-experienced patients as addition to an optimized background therapy (OBT).

AREAS COVERED

A Medline search was conducted of Phase II - IV clinical trials, as well as a review of abstracts from major HIV and infectious disease conferences from 2010 - 2013, involving etravirine.

EXPERT OPINION

Etravirine is a well-tolerated NNRTI with a good safety profile and a higher genetic barrier for resistance compared to first-generation NNRTIs. Rash is a potential side effect but remains mostly mild to moderate. The necessity of taking it twice daily with food (200 mg bid.), potential pharmacokinetic interactions and low concentrations in the central nervous system (CNS) represent limitations. The efficacy of once daily etravirine (400 mg qid.) and the use in treatment modification/simplification strategies requires further research. Despite its favorable profile, etravirine is currently not sufficiently investigated nor approved for use in treatment-naïve patients which should be balanced against its potential as a backup NNRTI and the broad cross-resistance conferred by etravirine failure to other NNRTIs. Etravirine should be avoided following treatment failure with regimens containing rilpivirine, another second-generation NNRTI.

Effects of etravirine on the pharmacokinetics and pharmacodynamics of warfarin in rats

BACKGROUND AND PURPOSE

Warfarin is often used with etravirine (ETV) to prevent HIV-related thromboembolic events. As both warfarin and ETV bind to plasma proteins and are metabolized by hepatic cytochrome P450s, they are likely to interact. Hence, we evaluated the effect of ETV on the pharmacokinetics and blood clotting time of racemic warfarin in rats.

EXPERIMENTAL APPROACH

Two groups of male Sprague-Dawley rats, in which the jugular vein had been cannulated, were studied. The control group (n = 10) received 1 mg·kg(-1) racemic warfarin i.v., and the test group (n = 13) 1 mg·kg(-1) of racemic warfarin followed by 25 mg·kg(-1) ETV i.v. Serial blood samples were collected for up to 144 h and the blood clotting time (calculated as international normalized ratio [INR]) measured in blood plasma at each sample point. Plasma concentrations of R-warfarin, S-warfarin, R-7-hydroxywarfarin and S-7-hydroxywarfarin were measured by a LC/MS/MS method using a chiral lux cellulose-1 column. Pharmacokinetic parameters were analysed using non-compartmental methods.

KEY RESULTS

ETV significantly increased, by threefold, the systemic clearance and volume of distribution of S-warfarin, but not those of R-warfarin. ETV decreased the total AUC of warfarin, but had no effect on its elimination half-life. ETV also increased the systemic clearance of both R-7-hydroxywarfarin and S-7-hydroxywarfarin but only increased the volume of distribution of R-7-hydroxywarfarin. Interestingly, the effect of warfarin on blood clotting time (INR) was significantly increased in the presence of etravirine.

CONCLUSION AND IMPLICATIONS

Our data suggest that etravirine may potentiate the anticoagulant effect of warfarin and this could have clinical significance.

[The Spanish AIDS Study Group and Spanish National AIDS Plan (GESIDA/Secretaría del Plan Nacional sobre el Sida) recommendations for the treatment of tuberculosis in HIV-infected individuals (Updated January 2013)]

This consensus document was prepared by an expert panel of the Grupo de Estudio de Sida (GESIDA [Spanish AIDS Study Group]) and the Plan Nacional sobre el Sida (PNS [Spanish National AIDS Plan]). The document updates current guidelines on the treatment of tuberculosis (TB) in HIV-infected individuals contained in the guidelines on the treatment of opportunistic infections published by GESIDA and PNS in 2008. The document aims to facilitate the management and treatment of HIV-infected patients with TB in Spain, and includes specific sections and recommendations on the treatment of drug-sensitive TB, multidrug-resistant TB, and extensively drug-resistant TB, in this population. The consensus guidelines also make recommendations on the treatment of HIV-infected patients with TB in special situations, such as chronic liver disease, pregnancy, kidney failure, and transplantation. Recommendations are made on the timing and initial regimens of antiretroviral therapy in patients with TB, and on immune reconstitution syndrome in HIV-infected patients with TB who are receiving antiretroviral therapy. The document does not cover the diagnosis of TB, diagnosis/treatment of latent TB, or treatment of TB in children. The quality of the evidence was evaluated and the recommendations graded using the approach of the Grading of Recommendations Assessment, Development and Evaluation Working Group.

Review of drug interactions with telaprevir and antiretrovirals

HCV infection is a major cause of mortality worldwide. HCV-related deaths also represent a leading cause of mortality in HIV-coinfected individuals. Telaprevir is an NS3/4A protease inhibitor approved for the treatment of chronic HCV genotype 1 infection in adults in combination with pegylated interferon and ribavirin. Telaprevir-based treatment has been shown to increase rates of sustained viral response in HCV genotype-1-monoinfected patients, and studies in HCV-HIV-coinfected patients are ongoing. Drug-drug interactions of telaprevir with antiretroviral drugs were investigated in a series of studies in healthy subjects. This review summarizes the results of interaction studies with low-dose ritonavir, ritonavir-boosted HIV protease inhibitors (atazanavir, darunavir, fosamprenavir and lopinavir), efavirenz, etravirine, rilpivirine, tenofovir disoproxil fumarate and raltegravir.

Etravirine in CSF is highly protein bound

OBJECTIVES

Etravirine has high affinity for plasma drug-binding proteins, such as albumin and α1-acid glycoprotein, which limits the amount of unbound etravirine available to enter the CNS. The objective of this study was to compare total and unbound etravirine concentrations in CSF with plasma concentrations and the in vitro median inhibitory concentration (IC50) for wild-type HIV (0.9 ng/mL).

METHODS

Total and bound etravirine concentrations were measured in 17 CSF and plasma pairs by isotope-dilution liquid chromatography tandem mass spectroscopy, radioligand displacement and ultracentrifugation. Unbound etravirine concentrations were calculated from the bound fraction. The dynamic range of the assay was 7.8-2000 (plasma) and 0.78-200 (CSF) ng/mL.

RESULTS

Subjects were mostly middle-aged (median 43 years) white (78%) men (89%). All CSF etravirine concentrations were above the limit of quantification. Total and unbound median etravirine concentrations in CSF were 9.5 (IQR 6.4, 26.4) and 0.13 (IQR 0.08, 0.27) ng/mL, respectively. Etravirine was 96% (IQR 94.5, 97.2) protein bound in plasma and 98.4% (IQR 97.8, 98.8) in CSF. Total etravirine in CSF was 4.3% (IQR 3, 5.9) of total and 101% (IQR 76, 160) of unbound etravirine in plasma. There were no significant correlations between unbound etravirine concentrations and concentrations of albumin in plasma or CSF. Unbound etravirine concentrations in CSF did not reach the wild-type IC50 in any of the specimens.

CONCLUSIONS

Unbound etravirine may not achieve optimal concentrations to inhibit HIV replication in the CNS.

Effects of etravirine on the pharmacokinetics of the integrase inhibitor S/GSK1265744

HIV integrase inhibitors such as raltegravir and elvitegravir halt HIV progression, but treatment-emergent resistance and cross-resistance have been observed. The nonnucleoside reverse transcriptase inhibitor etravirine (ETR) may be used in combination with integrase inhibitors in patients with drug resistance. This single-center, open-label, two-period, single-sequence crossover study evaluated the effects of ETR coadministration on the pharmacokinetic profile of S/GSK1265744, an investigational integrase inhibitor in phase 2 studies. Healthy subjects received 30 mg of S/GSK1265744 alone once daily for 10 days (period 1) and in combination with 200 mg of ETR twice daily for 14 days (period 2). Serial plasma samples for pharmacokinetic analyses were collected on day 10 during period 1 and on day 14 during period 2. All treatments were well tolerated. Etravirine had no effects on S/GSK1265744 geometric mean ratios of the area under the curve from time zero until the end of the dosing interval (1.01; 90% confidence interval [CI], 0.956 to 1.06), of the maximum observed plasma concentration (1.04; 90% CI, 0.987 to 1.09), or of the plasma concentration at the end of the dosing interval (0.999; 90% CI, 0.942 to 1.06). Etravirine pharmacokinetics (PK) parameters observed following coadministration with S/GSK1265744 were in the range of historical values reported for ETR alone in healthy subjects. These results indicate that 30 mg of S/GSK1265744 for 10 days as monotherapy followed by an additional 14 days in combination with ETR was well tolerated in healthy subjects and that no dose adjustment of S/GSK1265744 is required when it is coadministered with ETR.

Important Drug-Drug Interactions in HIV-Infected Persons on Antiretroviral Therapy: An Update on New Interactions Between HIV and Non-HIV Drugs

Advances in antiretroviral therapy have turned HIV into a chronic, manageable disease. Patients often require treatment for co-morbid conditions as well as HIV, and consequently, pharmacokinetic interactions between antiretrovirals (ARVs) and other drug classes are an increasing concern. Protease inhibitors and non-nucleoside reverse transcriptase inhibitors are involved in the CYP450 or other transporter systems, and may be associated with higher risk of clinically significant drug interactions. One reverse transcriptase inhibitor, abacavir, has demonstrated weak inhibition of CYP3A4, 2D6 and 2C9 in vitro, but is not associated with any clinically significant interactions involving the CYP450 system. The integrase inhibitor raltegravir is not involved in the CYP450 system, and may be a suitable option to use when trying to minimize interactions with other drug classes. This review summarizes recently published data on clinically significant drug interactions between ARVs and other drug classes including antineoplastics, immunosuppressant transplant drugs, directly acting antivirals for hepatitis C, antifungals, antimalarials, corticosteroids, psychotropics, hormonal contraceptives, anticoagulants, drugs for pulmonary hypertension, and herbal products. In situations of suspected or potential interactions, close monitoring is warranted, and dose adjustments or substitutions may be required.

Drug-drug interactions between antiretroviral and immunosuppressive agents in HIV-infected patients after solid organ transplantation: a review

Since the introduction of combination antiretroviral therapy (cART) resulting in the prolonged survival of HIV-infected patients, HIV infection is no longer considered to be a contraindication for solid organ transplantation (SOT). The combined management of antiretroviral and immunosuppressive therapy proved to be extremely challenging, as witnessed by high rates of allograft rejection and drug toxicity, but the profound drug-drug interactions between immunosuppressants and cART, especially protease inhibitors (PIs) also play an important role. Caution and frequent drug level monitoring of calcineurin inhibitors, such as tacrolimus are necessary when PIs are (re)introduced or withdrawn in HIV-infected recipients. Furthermore, the pharmacokinetics of glucocorticoids and mTOR inhibitors are seriously affected by PIs. With the introduction of integrase inhibitors, CCR5-antagonists and fusion inhibitors which cause significantly less pharmacokinetic interactions, have minor overlapping toxicity, and offer the advantage of pharmacodynamic synergy, it is time to revaluate what may be considered the optimal antiretroviral regimen in SOT recipients. In this review we provide a brief overview of the recent success of SOT in the HIV population, and an update on the pharmacokinetic and pharmacodynamic interactions between currently available cART and immunosuppressants in HIV-infected patients, who underwent SOT.

Effect of rifampin and rifabutin on the pharmacokinetics of lersivirine and effect of lersivirine on the pharmacokinetics of rifabutin and 25-O-desacetyl-rifabutin in healthy subjects

Lersivirine is a nonnucleoside reverse transcriptase inhibitor (NNRTI) with a unique resistance profile exhibiting potent antiviral activity against wild-type HIV and several clinically relevant NNRTI-resistant strains. Lersivirine, a weak inducer of the cytochrome P450 (CYP) enzyme CYP3A4, is metabolized by CYP3A4 and UDP glucuronosyltransferase 2B7 (UGT2B7). Two open, randomized, two-way (study 1; study A5271008) or three-way (study 2; study A5271043) crossover phase I studies were carried out under steady-state conditions in healthy subjects. Study 1 (n = 17) investigated the effect of oral rifampin on the pharmacokinetics (PKs) of lersivirine. Study 2 (n = 18) investigated the effect of oral rifabutin on the PKs of lersivirine and the effect of lersivirine on the PKs of rifabutin and its active metabolite, 25-O-desacetyl-rifabutin. Coadministration with rifampin decreased the profile of the lersivirine area under the plasma concentration-time curve from time zero to 24 h postdose (AUC(24)), maximum plasma concentration (C(max)), and plasma concentration observed at 24 h postdose (C(24)) by 85% (90% confidence interval [CI], 83, 87), 83% (90% CI, 79, 85), and 92% (90% CI, 89, 94), respectively, versus the values for lersivirine alone. Coadministration with rifabutin decreased the lersivirine AUC(24), C(max), and C(24) by 34% (90% CI, 29, 39), 25% (90% CI, 16, 33), and 58% (90% CI, 52, 64), respectively, compared with the values for lersivirine alone. Neither the rifabutin concentration profile nor overall exposure was affected following coadministration with lersivirine. Lersivirine and rifabutin reduced the 25-O-desacetyl-rifabutin AUC(24) by 27% (90% CI, 21, 32) and C(max) by 27% (90% CI, 19, 34). Lersivirine should not be coadministered with rifampin, which is a potent inducer of CYP3A4, UGT2B7, and P-glycoprotein activity and thus substantially lowers lersivirine exposure. No dose adjustment of rifabutin is necessary in the presence of lersivirine; an upward dose adjustment of lersivirine may be warranted when it is coadministered with rifabutin.