Effects of etravirine alone and with ritonavir-boosted protease inhibitors on the pharmacokinetics of dolutegravir

Drug-drug interactions that alter the exposure of glucuronidated drugs: Scope, UDP-glucuronosyltransferase (UGT) enzyme selectivity, mechanisms (inhibition and induction), and clinical significance

Drug-drug interactions (DDIs) arising from the perturbation of drug metabolising enzyme activities represent both a clinical problem and a potential economic loss for the pharmaceutical industry. DDIs involving glucuronidated drugs have historically attracted little attention and there is a perception that interactions are of minor clinical relevance. This review critically examines the scope and aetiology of DDIs that result in altered exposure of glucuronidated drugs. Interaction mechanisms, namely inhibition and induction of UDP-glucuronosyltransferase (UGT) enzymes and the potential interplay with drug transporters, are reviewed in detail, as is the clinical significance of known DDIs. Altered victim drug exposure arising from modulation of UGT enzyme activities is relatively common and, notably, the incidence and importance of UGT induction as a DDI mechanism is greater than generally believed. Numerous DDIs are clinically relevant, resulting in either loss of efficacy or an increased risk of adverse effects, necessitating dose individualisation. Several generalisations relating to the likelihood of DDIs can be drawn from the known substrate and inhibitor selectivities of UGT enzymes, highlighting the importance of comprehensive reaction phenotyping studies at an early stage of drug development. Further, rigorous assessment of the DDI liability of new chemical entities that undergo glucuronidation to a significant extent has been recommended recently by regulatory guidance. Although evidence-based approaches exist for the in vitro characterisation of UGT enzyme inhibition and induction, the availability of drugs considered appropriate for use as 'probe' substrates in clinical DDI studies is limited and this should be research priority.

Comparative Clinical Pharmacokinetics and Pharmacodynamics of HIV-1 Integrase Strand Transfer Inhibitors: An Updated Review

Bictegravir, cabotegravir, dolutegravir, elvitegravir, and raltegravir are members of the latest class of antiretrovirals available to treat human immunodeficiency virus (HIV) infection, the integrase strand transfer inhibitors. Integrase strand transfer inhibitors are potent inhibitors of the HIV integrase enzyme with IC_90/95 values in the low nanogram per milliliter range and they retain antiviral activity against strains of HIV with acquired resistance to other classes of antiretrovirals. Each of the integrase strand transfer inhibitors have unique pharmacokinetic/pharmacodynamic properties, influencing their role in clinical use in specific subsets of patients. Cabotegravir, approved for use in Canada but not yet by the US Food and Drug Administration, is formulated in both oral and intramuscular formulations; the latter of which has shown efficacy as a long-acting extended-release formulation. Cabotegravir, raltegravir, and dolutegravir have minimal drug-drug interaction profiles, as their metabolism has minimal cytochrome P450 involvement. Conversely, elvitegravir metabolism occurs primarily via cytochrome P450 3A4 and requires pharmacokinetic boosting to achieve systemic exposures amenable to once-daily dosing. Bictegravir metabolism has similar contributions from both cytochrome P450 3A4 and uridine 5'-diphospho-glucuronosyltransferase 1A1. Bictegravir, dolutegravir, and raltegravir are recommended components of initial regimens for most people with HIV in the US adult and adolescent HIV treatment guidelines. This review summarizes and compares the pharmacokinetics and pharmacodynamics of the integrase strand transfer inhibitor agents, and describes specific pharmacokinetic considerations for persons with hepatic impairment, renal dysfunction, pregnancy, and co-infections.

PBPK Modeling as a Tool for Predicting and Understanding Intestinal Metabolism of Uridine 5'-Diphospho-glucuronosyltransferase Substrates

Uridine 5′-diphospho-glucuronosyltransferases (UGTs) are expressed in the small intestines, but prediction of first-pass extraction from the related metabolism is not well studied. This work assesses physiologically based pharmacokinetic (PBPK) modeling as a tool for predicting intestinal metabolism due to UGTs in the human gastrointestinal tract. Available data for intestinal UGT expression levels and in vitro approaches that can be used to predict intestinal metabolism of UGT substrates are reviewed. Human PBPK models for UGT substrates with varying extents of UGT-mediated intestinal metabolism (lorazepam, oxazepam, naloxone, zidovudine, cabotegravir, raltegravir, and dolutegravir) have demonstrated utility for predicting the extent of intestinal metabolism. Drug–drug interactions (DDIs) of UGT1A1 substrates dolutegravir and raltegravir with UGT1A1 inhibitor atazanavir have been simulated, and the role of intestinal metabolism in these clinical DDIs examined. Utility of an in silico tool for predicting substrate specificity for UGTs is discussed. Improved in vitro tools to study metabolism for UGT compounds, such as coculture models for low clearance compounds and better understanding of optimal conditions for in vitro studies, may provide an opportunity for improved in vitro–in vivo extrapolation (IVIVE) and prospective predictions. PBPK modeling shows promise as a useful tool for predicting intestinal metabolism for UGT substrates.

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.

Physiologically-Based Pharmacokinetic Modeling to Support the Clinical Management of Drug-Drug Interactions With Bictegravir

Bictegravir is equally metabolized by cytochrome P450 (CYP)3A and uridine diphosphate‐glucuronosyltransferase (UGT)1A1. Drug–drug interaction (DDI) studies were only conducted for strong inhibitors and inducers, leading to some uncertainty whether moderate perpetrators or multiple drug associations can be safely coadministered with bictegravir. We used physiologically‐based pharmacokinetic (PBPK) modeling to simulate DDI magnitudes of various scenarios to guide the clinical DDI management of bictegravir. Clinically observed DDI data for bictegravir coadministered with voriconazole, darunavir/cobicistat, atazanavir/cobicistat, and rifampicin were predicted within the 95% confidence interval of the PBPK model simulations. The area under the curve (AUC) ratio of the DDI divided by the control scenario was always predicted within 1.25‐fold of the clinically observed data, demonstrating the predictive capability of the used modeling approach. After the successful verification, various DDI scenarios with drug pairs and multiple concomitant drugs were simulated to analyze their effect on bictegravir exposure. Generally, our simulation results suggest that bictegravir should not be coadministered with strong CYP3A and UGT1A1 inhibitors and inducers (e.g., atazanavir, nilotinib, and rifampicin), but based on the present modeling results, bictegravir could be administered with moderate dual perpetrators (e.g., efavirenz). Importantly, the inducing effect of rifampicin on bictegravir was predicted to be reversed with the concomitant administration of a strong inhibitor such as ritonavir, resulting in a DDI magnitude within the efficacy and safety margin for bictegravir (0.5–2.4‐fold). In conclusion, the PBPK modeling strategy can effectively be used to guide the clinical management of DDIs for novel drugs with limited clinical experience, such as bictegravir.

Population pharmacokinetic modelling to quantify the magnitude of drug-drug interactions between amlodipine and antiretroviral drugs

PURPOSE

Drug-drug interactions (DDIs) with antiretroviral drugs (ARVs) represent an important issue in elderly people living with HIV (PLWH). Amlodipine is a commonly prescribed antihypertensive drug metabolized by CYP3A4, thus predisposed to a risk of DDIs. Guidance on the management of DDIs is mostly based on theoretical considerations derived from coadministration with other CYP3A4 inhibitors. This study aimed at characterizing the magnitude of DDIs between amlodipine and ARV drugs in order to establish dosing recommendations.

METHODS

A population pharmacokinetic analysis was developed using non-linear mixed effect modelling (NONMEM) and included 163 amlodipine concentrations from 55 PLWH. Various structural and error models were compared to characterize optimally the concentration-time profile of amlodipine. Demographic and clinical characteristics as well as comedications were tested as potential influential covariates. Model-based simulations were performed to compare amlodipine exposure (i.e. area under the curve, AUC) between coadministered ARV drugs.

RESULTS

Amlodipine concentration-time profile was best described using a one-compartment model with first-order absorption and a lag-time. Amlodipine apparent clearance was influenced by both CYP3A4 inhibitors and efavirenz (CYP3A4 inducer). Model-based simulations revealed that amlodipine AUC increased by 96% when coadministered with CYP3A4 inhibitors, while efavirenz decreased drug exposure by 59%.

CONCLUSION

Coadministered ARV drugs significantly impact amlodipine disposition in PLWH. Clinicians should adjust amlodipine dosage accordingly, by halving the dosage in PLWH receiving ARV with inhibitory properties (mainly ritonavir-boosted darunavir), whereas they should double amlodipine doses when coadministering it with efavirenz, under appropriate monitoring of clinical response and tolerance.

Population pharmacokinetics of dolutegravir: influence of drug-drug interactions in a real-life setting

OBJECTIVES

Dolutegravir is widely prescribed owing to its potent antiviral activity, high genetic barrier and good tolerability. The aim of this study was to characterize dolutegravir's pharmacokinetic profile and variability in a real-life setting and to identify individual factors and co-medications affecting dolutegravir disposition.

METHODS

A population pharmacokinetic model was developed using NONMEM®. Relevant demographic factors, clinical factors and co-medications were tested as potential covariates. Simulations based on the final model served to compare expected dolutegravir concentrations under standard and alternative dosage regimens in the case of drug-drug interactions.

RESULTS

A total of 620 dolutegravir plasma concentrations were collected from 521 HIV-infected individuals under steady-state conditions. A one-compartment model with first-order absorption and elimination best characterized dolutegravir pharmacokinetics. Typical dolutegravir apparent clearance (CL/F) was 0.93 L/h with 32% between-subject variability, the apparent volume of distribution was 20.2 L and the absorption rate constant was fixed to 2.24 h-1. Older age, higher body weight and current smoking were associated with higher CL/F. Atazanavir co-administration decreased dolutegravir CL/F by 38%, while darunavir modestly increased CL/F by 14%. Rifampicin co-administration showed the largest impact on CL/F. Simulations suggest that average dolutegravir trough concentrations are 63% lower after 50 mg/12h with rifampicin compared with a standard dosage of 50 mg/24h without rifampicin. Average trough concentrations after 100 mg/24h and 100 mg/12h with rifampicin are 92% and 25% lower than the standard dosage without rifampicin, respectively.

CONCLUSIONS

Patients co-treated with dolutegravir and rifampicin might benefit from therapeutic drug monitoring and individualized dosage increase, up to 100 mg/12 h in some cases.

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.

Optimizing concentrations of concomitant antiretrovirals by reducing etravirine doses: two case reports of complex drug-drug interactions

We report the cases of two treatment-experienced HIV-infected patients with complex antiretroviral regimens that showed significant drug-drug interactions with etravirine. Unexpectedly high etravirine concentrations likely caused subtherapeutic levels of darunavir, elvitegravir and dolutegravir through concentration-dependent metabolic induction. Therapeutic drug monitoring allowed safe etravirine dose decreases to manage these interactions.

Dolutegravir Population Pharmacokinetics in a Real-Life Cohort of People Living With HIV Infection: A Covariate Analysis

BACKGROUND

There are growing concerns about dolutegravir (DTG)-related neuropsychiatric adverse events and about differences in the characteristics of people living with HIV infection (PLWH) potentially associated with higher risks of said side effects. Several studies have shown that DTG was stopped more frequently among women, older PLWH, and PLWH who initiated abacavir (ABC) at the same time. This study aimed to clarify the factors affecting the pharmacokinetics (PKs) of DTG in a real-life cohort of PLWH using a population PK approach.

METHODS

The model-building strategy was based on a previously published model developed from premarketing trials (1-compartment model with first-order absorption and a lag time). Sparse therapeutic drug monitoring data were obtained from a real-life cohort of 279 PLWH, and population PK analysis was performed using Monolix software. A stepwise covariate model-building strategy was used to evaluate any relevant effects of age, body weight, gender, total bilirubin, smoking status, formulations of DTG, morning versus evening dosing, backbone therapy, and other comedications including CYP/UGT inducers/inhibitors.

RESULTS

For a typical 70-kg PLWH, the apparent clearance (CL/F) and apparent volume of distribution (V/F) were 0.748 L/h and 14.6 L, respectively. Of the demographic factors evaluated, body weight was a significant covariate for CL/F and for V/F. Smokers had a 17% higher CL/F relative to nonsmokers. Both strong enzyme inhibitors (eg, atazanavir) and inducers (eg, rifampicin) had marked effects on DTG exposure, with potential clinical implications. Ritonavir-boosted darunavir was found to moderately increase clearance of DTG by 23%. No significant effect of ABC-based backbone therapy was observed on the PK parameters of DTG.

CONCLUSIONS

Our results did not support the hypothesis that ABC, by competing with the DTG metabolic pathway, may significantly increase DTG exposure leading to potential drug toxicity.

Lack of a Clinically Significant Pharmacokinetic Interaction between Etravirine and Raltegravir Using an Original Approach Based on Drug Metabolism, Protein Binding, and Penetration in Seminal Fluid: A Pharmacokinetic Substudy of the ANRS-163 ETRAL Study

STUDY OBJECTIVE

The ANRS163-ETRAL study showed that etravirine 200 mg/raltegravir 400 mg twice-daily dual therapy was highly effective in the treatment of human immunodeficiency virus (HIV)-infected patients older than 45 years, with virologic and therapeutic success rates at week 48 of 99.4% and 94.5%, respectively. The objective of this study was to determine whether a clinically significant pharmacokinetic interaction between etravirine and raltegravir exists by assessing steady-state total and unbound etravirine, raltegravir, and inactive raltegravir-glucuronide concentrations 12 hours after last intake (C_12h ) in blood plasma (BP) and seminal plasma (SP).

DESIGN

Pharmacokinetic analysis of data from the ANRS163-ETRAL study.

PATIENTS

One hundred forty-six HIV-1-infected patients (of the 165 patients included in the ANRS-163 ETRAL study) who were receiving etravirine 200 mg and raltegravir 400 mg twice daily.

MEASUREMENTS AND MAIN RESULTS

Blood was collected from all 146 patients at weeks 2-4, 12, 24, and 48, and semen was collected from 21 patients at week 48. The extent of BP and SP protein binding was determined by using ultrafiltration assay. Total and unbound etravirine, raltegravir, and raltegravir-glucuronide C_12h were determined by ultra high performance liquid chromatography coupled with tandem mass spectrometry and interpreted by using the in vitro calculated protein-bound 95% inhibitory concentration (PBIC₉₅ ) for wild-type (WT) HIV: etravirine (116 ng/ml) and raltegravir (15 ng/ml). Median (interquartile range [IQR]) total BP etravirine C_12h (536 ng/ml [376-719]) and raltegravir (278 ng/ml [97-690]) were adequate in 99% and 96% of patients, respectively. Median (IQR) SP:BP C_12h ratio and BP unbound fraction were etravirine 0.3 (0.2-0.5) and < 1%, respectively, raltegravir 1.8 (1.3-3.3) and 12%, respectively, and raltegravir-glucuronide 12.0 (6.5-17.7) and > 99%, respectively. The BP raltegravir metabolic ratio (raltegravir glucuronide:raltegravir ratio) was 1.7, suggesting only weak induction of raltegravir glucuronidation by etravirine. Only three patients had etravirine and raltegravir C_12h < PBIC₉₅ simultaneously.

CONCLUSION

No clinically significant pharmacokinetic interaction between etravirine and raltegravir was detected. Total etravirine and raltegravir BP concentrations were adequate in most patients, favoring virologic efficacy and confirming good treatment adherence (> 95%), despite twice-daily administration. The long half-life of etravirine and higher unbound fraction SP of raltegravir (57%) ensured adequate concentrations of dual therapy in genital compartments. Our results indicate that etravirine and raltegravir have good, complementary pharmacokinetic profiles, suggesting that they could be used in a dual-treatment strategy.

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

INTRODUCTION

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

A Two-Way Steady-State Pharmacokinetic Interaction Study of Doravirine (MK-1439) and Dolutegravir

INTRODUCTION

Doravirine, a non-nucleoside reverse-transcriptase inhibitor in development for the treatment of patients with human immunodeficiency virus-1 infection, has potential to be used concomitantly in antiretroviral therapy with dolutegravir, an integrase strand transfer inhibitor. The pharmacokinetic interactions between these drugs were therefore assessed.

METHODS

Oral formulations of doravirine and dolutegravir were dosed both individually and concomitantly once daily in healthy adults. Twelve subjects (six were male), 23-42 years of age, were enrolled and 11 completed this phase I, open-label, three-period, fixed-sequence study per protocol; one subject was discontinued for a positive cotinine test at admission to period 2. In period 1, dolutegravir 50 mg was administered for 7 days. After a 7-day washout, doravirine 200 mg was dosed for 7 days in period 2, followed (without washout) by both doravirine and dolutegravir simultaneously for 7 days in period 3. Plasma samples were taken to determine dolutegravir and doravirine concentrations.

RESULTS

The steady-state concentration 24 h post-dose (C₂₄) of dolutegravir was not substantially altered by co-administration of doravirine multiple doses; area under the plasma concentration-time curve from dosing to 24 h post-dose (AUC_0-24), maximum concentration (C _max), and C₂₄ geometric mean ratios were 1.36, 1.43, and 1.27, respectively. The pharmacokinetics of doravirine was not affected by multiple doses of dolutegravir (geometric mean ratios: 1.00, 0.98, and 1.06 for AUC_0-24, C₂₄, and C _max, respectively). Both drugs were generally well tolerated.

CONCLUSION

The results of this study demonstrate that concomitant administration of doravirine and dolutegravir in healthy subjects causes no clinically significant alteration in the pharmacokinetic and safety profiles of the two drugs, thereby supporting further evaluation of co-administration of these agents for human immunodeficiency virus-1 treatment.

Dolutegravir plus rilpivirine dual therapy in treating HIV-1 infection

INTRODUCTION

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

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.

Dolutegravir plasma concentrations according to companion antiretroviral drug: unwanted drug interaction or desirable boosting effect?

BACKGROUND

Studies in healthy volunteers have shown that the recently approved HIV integrase inhibitor dolutegravir has limited drug-to-drug interaction profile. Here we carried out a pharmacokinetic survey in HIV-infected patients given dolutegravir as part of their antiretroviral therapy.

METHODS

Dolutegravir plasma trough concentrations were measured in 78 HIV-infected patients given the drug in combination with a protease inhibitor, a non-nucleoside reverse transcriptase inhibitor or abacavir/lamivudine. Drug concentrations were assessed by high performance liquid chromatography method with UV-detection.

RESULTS

All patients were given dolutegravir at 50 mg once daily, with median trough drug concentrations of 1,096 (664-2,356) ng/ml (interindividual coefficient of variation: 85.3%). Patients given dolutegravir with atazanavir had significantly higher drug concentrations compared with those given darunavir, rilpivirine or abacavir/lamivudine (2,399 [1,929-4,070] versus 738 [552-1,048], 603 [432-1,373] or 1,045 [856-1,115] ng/ml; P<0.001 for all comparisons). By multivariate analyses, only companion antiretroviral drug resulted in significant association with dolutegravir plasma trough concentrations (P=0.012).

CONCLUSIONS

Atazanavir coadministration significantly inhibited dolutegravir metabolism, ultimately resulting in a two- to fourfold increase in drug disposition compared with other antiretroviral drugs. This boosting effect of atazanavir could be used to optimize dolutegravir dosing in particular clinical settings.

Short Communication: Comparative Evaluation of Coformulated Injectable Combination Antiretroviral Therapy Regimens in Simian Immunodeficiency Virus-Infected Rhesus Macaques

The use of nonhuman primate (NHP) models to study persistent residual virus and viral eradication strategies in combination antiretroviral therapy (cART)-treated individuals requires regimens that effectively suppress SIV replication to clinically relevant levels in macaques. We developed and evaluated two novel cART regimens in SIVmac239-infected rhesus macaques: (1) a "triple regimen" containing the nucleo(s/t)ide reverse transcriptase inhibitors emtricitabine (FTC) and tenofovir disoproxil fumarate [TDF, prodrug of tenofovir (TFV, PMPA)] with the integrase strand transfer inhibitor dolutegravir (DTG) (n = 3), or (2) a "quad regimen" containing the same three drugs plus the protease inhibitor darunavir (DRV) (n = 3), with each regimen coformulated for convenient administration by a single daily subcutaneous injection. Plasma drug concentrations were consistent across animals within the triple and quad regimen-treated groups, although DTG levels were lower in the quad regimen animals. Time to achieve plasma viral loads stably <30 viral RNA copies/ml ranged from 12 to 20 weeks of treatment between animals, and viral loads <30 viral RNA copies/ml plasma were maintained through 40 weeks of follow-up on cART. Notably, although we show virologic suppression and development of viral resistance in a separate cohort of SIV-infected animals treated with oral DRV monotherapy, the addition of DRV in the quad regimen did not confer an apparent virologic benefit during early treatment, hence the quad regimen-treated animals were switched to the triple regimen after 4 weeks. This coformulated triple cART regimen can be safely, conveniently, and sustainably administered to durably suppress SIV replication to clinically relevant levels in rhesus macaques.

Clinical effectiveness of dolutegravir in the treatment of HIV/AIDS

Dolutegravir (DTG) is a second-generation integrase strand transfer inhibitor (INSTI), which has now been licensed to be used in different countries including the UK. Earlier studies have demonstrated that DTG when used with nucleoside backbone in treatment-naïve and - experienced patients has been well tolerated and demonstrated virological suppression comparable to other INSTIs and superiority against other first-line agents, including efavirenz and boosted protease inhibitors. Like other INSTIs, DTG uses separate metabolic pathways compared to other antiretrovirals and is a minor substrate for CYP-450. It does not appear to have a significant interaction with drugs, which uses the CYP-450 system. Nonetheless, it uses renal solute transporters that may potentially inhibit the transport of other drugs and can have an effect on the elimination of other drugs. However, the impact of this mechanism appears to be very minimal and insignificant clinically. The side effect profiles of DTG are similar to raltegravir and have been found to be well tolerated. DTG has a long plasma half-life and is suitable for once daily use without the need for a boosting agent. DTG has all the potential to be used as a first-line drug in combination with other nucleoside backbones, especially in the form of a single tablet in combination with abacavir and lamivudine. The purpose of this review article is to present the summary of the available key information about the clinical usefulness of DTG in the treatment of HIV infection.

Influence of nevirapine administration on the pharmacokinetics of dolutegravir in patients infected with HIV-1

OBJECTIVES

The metabolic pathways of dolutegravir and nevirapine suggest a potential pharmacokinetic interaction between these drugs. The objective of this study was to investigate the influence of nevirapine administration on the pharmacokinetics of dolutegravir in patients infected with HIV-1.

PATIENTS AND METHODS

This study was an investigator-initiated trial registered at ClinicalTrials.gov under identifier NCT02067767. Dolutegravir (50 mg once daily) was added to the antiretroviral regimen (400 mg of nevirapine once daily + 600/300 mg of abacavir/lamivudine once daily) in 10 adult patients for 5 days. After discontinuation of nevirapine, the combination of dolutegravir + abacavir/lamivudine was continued. Full pharmacokinetic profiles were assessed on the day of nevirapine discontinuation and 2 weeks after discontinuation of nevirapine. The pharmacokinetic parameters of dolutegravir were calculated by non-compartmental analysis. The log-transformed values of these parameters were compared between periods with and without nevirapine co-administration.

RESULTS

The co-administration of nevirapine led to a significant decrease (P < 0.05) in the area under the plasma concentration-time curve for dolutegravir from the time the dose was administered until the end of the dosing interval (-19%, P = 0.011), as well as decreases in trough plasma concentration (-34%, P = 0.018) and terminal half-life (-15%, P = 0.039), and a significant increase (P < 0.05) in apparent oral clearance for dolutegravir (+23%, P = 0.011).

CONCLUSIONS

The decrease in dolutegravir exposure in combination with nevirapine suggests that the metabolism of dolutegravir is induced by nevirapine. According to therapeutic drug monitoring for dolutegravir, some patients may need a higher dose than 50 mg of dolutegravir once daily to maintain the therapeutic plasma concentration throughout the dosing interval.

Dolutegravir - a review of the pharmacology, efficacy, and safety in the treatment of HIV

Dolutegravir is the newest integrase strand transfer inhibitor to be approved for the treatment of human immunodeficiency virus (HIV) infection. Dolutegravir is equivalent or superior to existing treatment regimens in both treatment-naïve and treatment-experienced patients including those with previous raltegravir or elvitegravir failure. The consistent efficacy coupled with excellent tolerability and infrequent drug–drug interactions makes the co-formulation of dolutegravir with two nucleotide reverse-transcriptase inhibitors an attractive treatment option. This review summarizes the pharmacokinetics, adverse event profile, and efficacy of dolutegravir in the treatment of HIV.

Clinical pharmacokinetics and pharmacodynamics of dolutegravir used as a single tablet regimen for the treatment of HIV-1 infection

INTRODUCTION

With the introduction of the coformulated dolutegravir, abacavir and lamivudine , a new single tablet regimen (STR) is made available for the use in treatment-naive and treatment-experienced HIV-infected patients. This drug combination is the fourth STR that will be positioned next to the STRs with efavirenz, rilpivirine or elvitegravir as third agents, respectively.

AREAS COVERED

The objective of this review is to provide an overview of the efficacy and safety of the combined dolutegravir/abacavir/lamivudine coformulation. The review will focus on dolutegravir and includes both published data as well as data presented at recent major international HIV/AIDS conferences.

EXPERT OPINION

The dolutegravir/abacavir/lamivudine regimen is highly effective in achieving sustained suppression of HIV-1 RNA plasma concentrations. The STR has a favorable safety profile and a low potential for drug interactions, which will contribute to a prominent role in therapy. As this STR contains abacavir as backbone component, the use requires patients to be HLA-B*5701 negative, with good hepatic function. Other first-line treatment combinations are preferred for patients with hepatitis B co-infection or with a high cardiovascular risk.

Disposition and metabolism of cabotegravir: a comparison of biotransformation and excretion between different species and routes of administration in humans

1.  Cabotegravir [(3S,11aR)-N-[(2,4-difluorophenyl)methyl]-6-hydroxy-3-methyl-5,7-dioxo-2,3,5,7,11,11a-hexahydro[1,3]oxazolo[3,2-a]pyrido[1,2-d]pyrazine-8-carboxamide] is an HIV-1 integrase inhibitor under development as a tablet for both oral lead-in therapy and long-acting (LA) injectable for intramuscular dosing. 2. Metabolism, pharmacokinetics and excretion were investigated in healthy human subjects who received either a single oral dose (28.2 mg) of [(14)C]cabotegravir in a mass balance study, or LA formulations of unlabeled cabotegravir (200-800 mg), intramuscularly or subcutaneously, in a separate study. Metabolism, distribution and excretion of [(14)C]cabotegravir were also investigated in mice, rats and monkeys. 3. Recovery of radioactivity in humans represented a mean total of 85.3% of the dose, including 26.8% in the urine. The mean apparent terminal phase half-life was similar for both cabotegravir and radioactivity, 39 h compared to 41 h. 4. Following oral, intramuscular and subcutaneous administration, cabotegravir was the major component in plasma and the glucuronic acid conjugate (M1) represented the predominant component in urine. Cabotegravir was present in bile along with its major metabolite (M1). 5. The primary metabolite of [(14)C]cabotegravir in mouse, rat and monkey was the same as that in human. In vitro phenotyping experiments demonstrated that cabotegravir was metabolized by UDP-glucuronosyltransferase (UGT) 1A1 and UGT1A9.

Dolutegravir: a review of its use in the management of HIV-1 infection in adolescents and adults

Dolutegravir (Tivicay(®)) is a new-generation HIV-1 integrase strand transfer inhibitor recently approved in the EU and Japan for the treatment of HIV-1 infection in adolescents and adults in combination with other antiretroviral drugs. It is suitable for once-daily administration and achieves therapeutic concentrations without the need for pharmacokinetic boosting. It has a high barrier to resistance and is generally active against viral strains resistant to first-generation integrase inhibitors. In well-designed clinical trials in treatment-naive or treatment-experienced, integrase inhibitor-naive patients, dolutegravir-based combinations were shown to be noninferior or superior to raltegravir-based combinations, an efavirenz-based combination and ritonavir-boosted darunavir-based combinations with respect to virological suppression (plasma HIV-1 RNA <50 copies/mL) at week 48. Dolutegravir was also effective in a high proportion of patients failing on raltegravir- or elvitegravir-based therapy as a result of integrase resistance mutations. Dolutegravir was generally well tolerated, with the vast majority of adverse events being mild or moderate in intensity; serious adverse events were uncommon. Therefore, dolutegravir is an important new addition to the expanding list of antiretroviral drugs for treating HIV-1 infection in adults and adolescents.

Dolutegravir-based antiretroviral therapy in a severely overweight child with a multidrug-resistant human immunodeficiency virus infection. A case report and review

The management of multidrug-resistant human immunodeficiency virus (MDR HIV) infections in children is particularly challenging due to the lack of experience with new drugs. Dolutegravir, combined with an optimized antiretroviral background therapy, is promising for the treatment of MDR HIV and has been approved recently for adults and adolescents. Data for children are extremely limited. We describe the efficacy, safety and plasmatic levels of a dolutegravir-based, complex active antiretroviral treatment regimen in a severely overweight 11-year-old child infected with an MDR HIV strain.

The role of dolutegravir in the management of HIV infection

Dolutegravir is the most recent integrase strand transfer inhibitor approved for HIV-1 infection in both treatment-naïve and experienced patients. As a tricyclic carbamoyl pyridone analog, dolutegravir is rapidly absorbed and distributes through the cerebrospinal fluid. It is hepatically metabolized by uridine diphosphate glucuronosyl transferase 1A1; no inhibition or induction of cytochrome P450 enzymes is noted. As a substrate of CYP 3A4, dolutegravir is affected by rifampin, efavirenz, tipranavir/ritonavir, fosamprenavir/ritonavir, and dose increase is required. Dolutegravir inhibits the organic cation transporter 2, resulting in decreased creatinine clearance with no apparent decrease in renal function. Other adverse effects are minimal but include diarrhea, headache, and nausea. Clinical trials in treatment-naïve and experienced patients are ongoing and will be presented in this text.

Dolutegravir: An Integrase Strand Transfer Inhibitor for the Treatment of Human Immunodeficiency Virus 1 in Adults

Objective: To review the efficacy, safety, pharmacokinetics, pharmacodynamics, administration, drug interactions, and cost of dolutegravir (Tivicay), a third in class integrase strand transfer inhibitor (INSTI), for the treatment of human immunodeficiency virus (HIV-1) in adults. Data Sources: MEDLINE, International Pharmaceutical Abstracts, ClinicalTrials.gov, and Google Scholar searches (January 2000 to May 2014) were conducted for articles published in English and limited to human subjects, using the key words antiretroviral drugs, HIV integrase strand transfer inhibitors, dolutegravir, DTG, and S/GSK1349572. Study Selection and Data Extraction: Following MEDLINE, International Pharmaceutical Abstracts, ClinicalTrials.gov, and Google Scholar searches, 6 clinical trials were identified and included in this review. Phase III/IV studies evaluating the safety and efficacy of dolutegravir in humans were selected and evaluated. Data Synthesis: In treatment naïve and experienced patients dolutegravir was noninferior to raltegravir at suppressing viral load when added to background therapy. Abacavir/lamivudine/dolutegravir was noninferior to efavirenz/emtricitabine/tenofovir disoproxil fumarate and darunavir/ritonavir plus background therapy at suppressing viral load. In patients with multiple-class antiretroviral resistance at baseline, dolutegravir decreased HIV RNA by 1.4 log10 copies/mL at day 8, 63% of patients had achieved virologic suppression at week 8, and retained potency in treatment-experienced INSTI-resistant patients up to week 48 or 96 of follow-up. Conclusion: Dolutegravir is a safe, effective, and well-tolerated treatment option for adults with HIV-1, even in the setting of resistance to other antiretrovirals.

Dolutegravir: a new HIV integrase inhibitor for the treatment of HIV infection

ABSTRACT 

Dolutegravir is a second-generation HIV integrase strand transfer inhibitor (INSTI) and the most recent antiretroviral approved for treatment of HIV-1 infection. Dolutegravir in combination with two nucleoside reverse transcriptase inhibitors is one of the preferred regimens recommended by the Department of Health and Human Services HIV treatment guidelines for treatment-naive adults and adolescents. This recommendation is based on clinical trial data where dolutegravir demonstrated superiority compared with guideline preferred regimens containing efavirenz and ritonavir-boosted darunavir and noninferiority compared with first-generation INSTI, raltegravir. Dolutegravir also demonstrated superiority when compared with raltegravir in treatment-experienced, integrase-naive patients and clinical efficacy in patients with resistance to first-generation INSTIs. Overall, dolutegravir has demonstrated excellent tolerability, limited drug interactions, minimal drug resistance and once-daily dosing for treatment-naive patients.

Evaluation of dolutegravir safety for the treatment of HIV-1

INTRODUCTION

Dolutegravir (DGV) is the newest integrase inhibitor approved for the treatment of HIV-1 infection in both treatment-naive and experienced adults and adolescents. This article reviews the safety of DGV for the treatment of HIV-1 infection.

AREAS COVERED

The PubMed database was searched using the keywords 'DGV' and 'HIV'. In addition, conference proceedings from Conference on Retroviruses and Opportunistic Infections, International AIDS Society and European AIDS Clinical Society meetings were searched for presentations on DGV clinical studies.

EXPERT OPINION

DGV has demonstrated a favorable safety profile and is well tolerated for the treatment of HIV-1 infection. Unlike raltegravir, DGV can be given once daily, and unlike elvitegravir, it does not require pharmacologic boosting to achieve consistent blood levels.

Successful antiretroviral therapy by using unusual antiretroviral combinations in heavily pre-treated patients: two case reports

In the context of HIV-infected patients with several past antiretroviral therapies and multiple failures, it is possible to be faced with viruses resistant to all drug classes. We report on two HIV-1 infected patients in which the historical genotype showed mutations against all the major drug classes and in which viral suppression has been obtained by non-conventional antiretroviral therapy regimens, including the combination of darunavir at high dosage (800 mg bid), dolutegravir (50 mg bid) and a third agent, i.e. enfuvirtide in the first case and etravirine in the second one.

Dolutegravir: a new option for HIV treatment

ABSTRACT: 

The need for new strategies for treating HIV-1 infection has led to the development of a number of new drugs. The aim of this article is to review the latest results of clinical trials of dolutegravir, an integrase inhibitor whose efficacy, tolerability and safety have been confirmed in treatment-naive and treatment-experienced patients. The findings, together with its high genetic barrier and limited interactions with other drugs, indicate that dolutegravir will play an important role in the future treatment of HIV infection.

Effects of enzyme inducers efavirenz and tipranavir/ritonavir on the pharmacokinetics of the HIV integrase inhibitor dolutegravir

PURPOSE

Dolutegravir (DTG) is an unboosted, integrase inhibitor for the treatment of HIV infection. Two studies evaluated the effects of efavirenz (EFV) and tipranavir/ritonavir (TPV/r) on DTG pharmacokinetics (PK) in healthy subjects.

METHODS

The first study was an open-label crossover where 12 subjects received DTG 50 mg every 24 hours (q24h) for 5 days, followed by DTG 50 mg and EFV 600 mg q24h for 14 days. The second study was an open-label crossover where 18 subjects received DTG 50 mg q24h for 5 days followed by TPV/r 500/200 mg every 12 hours (q12h) for 7 days and then DTG 50 mg q24h and TPV/r 500/200 mg q12h for a further 5 days. Safety assessments and serial PK samples were collected. Non-compartmental PK analysis and geometric mean ratios and 90% confidence intervals were generated.

RESULTS

The combination of DTG with EFV or TPV/r was generally well tolerated. Four subjects discontinued the TPV/r study due to increases in alanine aminotransferase that were considered related to TPV/r. Co-administration with EFV resulted in decreases of 57, 39 and 75% in DTG AUC(0-τ), Cmax and Cτ, respectively. Co-administration with TPV/r resulted in decreases of 59, 46 and 76% in DTG AUC(0-τ), Cmax and Cτ, respectively.

CONCLUSIONS

Given the reductions in exposure and PK/pharmacodynamic relationships in phase II/III trials, DTG should be given at an increased dose of 50 mg twice daily when co-administered with EFV or TPV/r, and alternative regimens without inducers should be considered in integrase inhibitor-resistant patients.

Dolutegravir, the Second-Generation of Integrase Strand Transfer Inhibitors (INSTIs) for the Treatment of HIV

The integrase strand transfer inhibitors (INSTIs) are the newest antiretroviral class in the HIV treatment armamentarium. Dolutegravir (DTG) is the only second-generation INSTI with FDA approval (2013). It has potential advantages in comparison to first-generation INSTI’s, including unboosted daily dosing, limited cross resistance with raltegravir and elvitegravir, and a high barrier to resistance. Clinical trials have evaluated DTG as a 50-mg daily dose in both treatment-naïve and treatment-experienced, INSTI-naïve participants. In those treatment-naïve participants with baseline viral load <100,000 copies/mL, DTG combined with abacavir and lamivudine was non-inferior and superior to fixed-dose combination emtricitabine/tenofovir/efavirenz. DTG was also superior to the protease inhibitor regimen darunavir/ritonavir in treatment-naïve participants regardless of baseline viral load. Among treatment-experienced patients naïve to INSTI, DTG (50 mg daily) demonstrated both non-inferiority and superiority when compared to the first-generation INSTI raltegravir (400 mg twice daily) regardless of the background regimen. No phenotypically significant DTG resistance has been demonstrated in INSTI-naïve participant trials. The VIKING trials evaluated DTG’s ability to treat persons with HIV with prior INSTI exposure. VIKING demonstrated twice-daily DTG was more efficacious than daily dosing when treating participants receiving and failing first-generation INSTI regimens. DTG maintained potency against single mutations from any of the three major INSTI pathways (Y143, H155, Q148); however, the Q148 mutation with two or more additional mutations significantly reduced its potency. The long-acting formulation of DTG, GSK1265744LA, is the next innovation in this second-generation INSTI class, holding promise for the future of HIV prevention and treatment.

Pharmacokinetics and pharmacodynamics of boosted once-daily darunavir

The ability to dose antiretroviral agents once daily simplifies the often complex therapeutic regimens required for the successful treatment of HIV infection. Thus, once-daily dosing can lead to improved patient adherence to medication and, consequently, sustained virological suppression and reduction in the risk of emergence of drug resistance. Several trials have evaluated once-daily darunavir/ritonavir in combination with other antiretrovirals (ARTEMIS and ODIN trials) or as monotherapy (MONET, MONOI and PROTEA trials) in HIV-1-infected adults. Data from ARTEMIS and ODIN demonstrate non-inferiority of once-daily darunavir/ritonavir against a comparator and, together with pharmacokinetic data, have established the suitability of once-daily darunavir/ritonavir for treatment-naive and treatment-experienced patients with no darunavir resistance-associated mutations. The findings of ARTEMIS and ODIN have led to recent updates to treatment guidelines, whereby once-daily darunavir/ritonavir, given with other antiretrovirals, is now a preferred treatment option for antiretroviral-naive adult patients and a simplified treatment option for antiretroviral-experienced adults who have no darunavir resistance-associated mutations. Once-daily dosing with darunavir/ritonavir is an option for treatment-naive and for treatment-experienced paediatric patients with no darunavir resistance-associated mutations based on the findings of the DIONE trial and ARIEL substudy. This article reviews the pharmacokinetics, efficacy, safety and tolerability of once-daily boosted darunavir. The feasibility of darunavir/ritonavir monotherapy as a treatment approach for some patients is also discussed. Finally, data on a fixed-dose combination of 800/150 mg of darunavir/cobicistat once daily are presented, showing comparable darunavir bioavailability to that obtained with 800/100 mg of darunavir/ritonavir once daily.

Clinical pharmacokinetic, pharmacodynamic and drug-interaction profile of the integrase inhibitor dolutegravir

Dolutegravir is a second-generation integrase strand transfer inhibitor (INSTI) currently under review by the US Food and Drug Administration for marketing approval. The in vitro, protein-adjusted 90 % inhibitory concentration (IC90) of dolutegravir for wild-type virus is 0.064 μg/ml, and it retains in vitro anti-HIV 1 activity across a broad range of viral phenotypes that are known to confer resistance to the currently marketed INSTIs, raltegravir and elvitegravir. Dolutegravir has a terminal elimination half-life of 13-14 h and maintains concentrations over the in vitro, protein-adjusted IC90 for more than 30 h following a single dose. Additionally, dolutegravir has low inter-subject variability compared with raltegravir and elvitegravir. A plasma exposure-response relationship has been well described, with antiviral activity strongly correlating with trough concentrations. Phase III trials have assessed the antiviral activity of dolutegravir compared with efavirenz and raltegravir in antiretroviral (ARV)-naive patients and found that dolutegravir achieved more rapid and sustained virologic suppression in both instances. Additionally, studies of dolutegravir activity in patients with known INSTI-resistant mutations have been favourable, indicating that dolutegravir retains activity in a variety of INSTI-resistant phenotypes. Much like currently marketed INSTIs, dolutegravir is very well tolerated. Because dolutegravir inhibits the renal transporter organic cation transporter 2, reduced tubular secretion of creatinine leads to non-progressive increases in serum creatinine. These serum creatinine increases have not been associated with a decreased glomerular filtration rate or progressive renal impairment. Dolutegravir's major and minor metabolic pathways are uridine diphosphate glucuronosyltransferase 1A1 and cytochrome P450 (CYP)-3A4, respectively, and it neither induces nor inhibits CYP isoenzymes. Thus dolutegravir has a modest drug interaction profile. However, antacids significantly decrease dolutegravir plasma exposure and should be separated by 2 h before, or 6 h after, a dolutegravir dose. In summary, dolutegravir is the first of the second-generation INSTIs and exhibits a predictable pharmacokinetic profile and a well-defined exposure-response relationship. Dolutegravir retains activity despite the presence of some class-resistant mutations and achieves rapid and sustained virologic suppression in ARV-naive and ARV-experienced patients. Clinically, dolutegravir is poised to become a commonly used component of antiretroviral regimens.

Dolutegravir: first global approval

Dolutegravir, an orally administered HIV-1 integrase strand transfer inhibitor (INSTI), is under development by ViiV Healthcare. Like other drugs belonging in the INSTI class of antiretroviral agents, dolutegravir binds to the integrase site of HIV-1 and blocks the strand transfer integration step, thereby preventing the replication of HIV-1. Dolutegravir is being developed as an unboosted once-daily therapy for use in combination with other antiretroviral agents for the treatment of both treatment-naïve and treatment-experienced patients with HIV-1 infection. Dolutegravir has been approved in the USA for the treatment of HIV-1 infection in combination with other antiretroviral agents and has been filed for approval in the EU and Canada. Phase III development is underway in North America, Europe, South Africa, South America, Australia and Taiwan. This article summarizes the milestones in the development of dolutegravir leading to this first approval for the treatment of HIV-1 infection in both therapy-naïve and -experienced patients.

Dolutegravir

Each month, subscribers to The Formulary Monograph Service receive 5 to 6 well-documented monographs on drugs that are newly released or are in late phase 3 trials. The monographs are targeted to Pharmacy & Therapeutics Committees. Subscribers also receive monthly 1-page summary monographs on agents that are useful for agendas and pharmacy/nursing in-services. A comprehensive target drug utilization evaluation/medication use evaluation (DUE/MUE) is also provided each month. With a subscription, the monographs are sent in print and are also available on-line. Monographs can be customized to meet the needs of a facility. A drug class review is now published monthly with The Formulary Monograph Service. Through the cooperation of The Formulary, Hospital Pharmacy publishes selected reviews in this column. For more information about The Formulary Monograph Service, call The Formulary at 800-322-4349. The February 2014 monograph topics are sofosbuvir, simeprevir capsules, ibrutinib, hydrocodone extended-release capsules, and eslicarbazepine. The DUE/MUE is on sofosbuvir.

Dolutegravir: a new integrase strand transfer inhibitor for the treatment of HIV

The first two integrase strand transfer inhibitors (INSTIs) approved for treatment of patients infected with human immunodeficiency virus (HIV) were raltegravir and elvitegravir. Both raltegravir and elvitegravir are now guideline-preferred agents as part of an antiretroviral regimen for treatment-naive patients. However, raltegravir is dosed twice/day. Elvitegravir is available in a single-tablet regimen and dosed once/day because it is administered with the pharmacokinetic booster cobicistat, a potent CYP3A4 inhibitor that can lead to clinically significant drug-drug interactions. In addition, raltegravir and elvitegravir have a low genetic barrier to resistance and are associated with cross-resistance. Dolutegravir is a new-generation INSTI administered once/day without a pharmacokinetic booster and can be coformulated in a single-tablet regimen. Phase III studies have demonstrated the efficacy and safety of dolutegravir for treatment-naive and treatment-experienced patients. Compared with other INSTIs, dolutegravir has a higher genetic barrier to resistance. Dolutegravir was approved by the U.S. Food and Drug Administration in August 2013 and joins raltegravir and elvitegravir as guideline-preferred agents for the management for HIV-infected treatment-naive patients.

A sensitive HPLC-MS/MS method for the determination of dolutegravir in human plasma

A sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) assay was developed and validated to facilitate the assessment of clinical pharmacokinetics of dolutegravir (DTG) in plasma samples. This work describes an assay system requiring only a 20μL aliquot of human plasma that is subjected to a simple acetonitrile protein precipitation containing a stably labeled isotope of DTG used as an internal standard. Chromatography was performed on an XBridge C18, 2.1mm×50mm, reversed phase analytical column, using a 60:40 acetonitrile/water mobile phase containing 0.1% formic acid. Detection of the analyte and internal standard was achieved by ESI positive ionization tandem mass spectrometry. The precursor/product transitions (m/z) monitored were 420.1/136.0 and 428.1/283.1 for DTG and DTG-IS, respectively. The dynamic range of this assay extends from 5 to 10,000ng/mL, with a mean coefficient of determination (r, mean±SD) of 0.9996±0.0003. The mean precision values for calibration standards ranged from 0.7 to 4.1%, while accuracy values were 98.3 to 102.0%. Validation results demonstrated high accuracy (≤6.5% deviation) and high precision (≤9.1% CV) for the quality control samples. This assay system provides an accurate, precise, and sensitive method for DTG quantitation and was successfully applied to clinical research samples as part of a phase I/II pediatric clinical trial.

Dolutegravir, a Second-Generation Integrase Inhibitor for the Treatment of HIV-1 Infection

Objective: To review the pharmacology, safety, and efficacy of dolutegravir, an integrase strand-transfer inhibitor (INSTI), and to discuss its role in the treatment of HIV-1-infected patients. Data Sources: PubMed articles indexed through August 2013 were identified using the search terms S/GSK1349572, dolutegravir, and integrase inhibitor. Information was also identified from the package insert, cited publication references, professional meeting abstracts, and the ClinicalTrials.gov registry. Study Selection and Data Extraction: English language articleswere selected for evaluation, with preference given to safety, efficacy, and pharmacokinetic studies conducted in HIV-1-infected patients. Data Synthesis: Dolutegravir is a new INSTI approved for combination treatment in HIV-1-infected adults and adolescent children. Four phase 3 studies provide the basis for current labeling in antiretroviral-naïve and antiretroviral-experienced adults. Results from these studies demonstrate that dolutegravir is noninferior in efficacy to raltegravir in antiretroviral-naïve patients and superior in antiretroviral-experienced patients. Superiority to efavirenz and darunavir/ritonavir was also demonstrated in antiretroviral-naïve patients. Dolutegravir is well tolerated, exhibits low potential for drug-drug interactions, and has a long serum half-life, allowing it to be administered once-daily in patients without preexisting INSTI resistance. Twice-daily administration is recommended in patients with known or suspected resistance mutations to first-generation INSTIs. Mild elevations in serum creatinine occur following dolutegravir initiation from inhibition of renal organic cation transporter 2 but do not reflect changes in glomerular filtration. Conclusions: Dolutegravir is the first second-generation INSTI and exhibits several advantages over current integrase inhibitors and other preferred antiretrovirals. Long-term efficacy and safety are needed to define dolutegravir's role in treatment.

Integrase Strand Transfer Inhibitors in HIV Therapy

HIV drug resistance has been one of the major obstacles to HIV eradication and has contributed to the need for the constant development of new antiretroviral drugs over the past 25 years. With the recent approval of dolutegravir for human therapy by the U.S. Food and Drug Administration, health practitioners may soon have access to three integrase strand transfer inhibitors to treat individuals living with HIV. Here, we review the use of raltegravir, elvitegravir, and dolutegravir for use in first- and second-line HIV treatment regimens and the issue of HIV resistance against integrase inhibitors.

Lack of pharmacokinetic interaction between rilpivirine and integrase inhibitors dolutegravir and GSK1265744

Dolutegravir (DTG) and GSK1265744 are HIV integrase inhibitors (INIs) in clinical development. The oral formulation of rilpivirine (RPV), a nonnucleoside reverse transcriptase inhibitor (NNRTI), has been approved for treatment-naive HIV infection. Long-acting depot injections of GSK1265744 and RPV are also being developed. This study evaluated the potential for drug interactions between RPV and these INIs. This phase 1, open-label, two-cohort, three-period, single-sequence crossover study evaluated oral coadministration of RPV with DTG or GSK1265744. Healthy subjects received DTG (50 mg every 24 h for 5 days) or GSK1265744 (30 mg every 24 h for 12 days) in period 1 followed by a washout, RPV (25 mg every 24 h for 11 or 12 days) in period 2, immediately followed by RPV (25 mg every 24 h) plus DTG (50 mg every 24 h) for 5 days or GSK1265744 (30 mg every 24 h) for 12 days in period 3. Steady-state pharmacokinetic (PK) parameters were estimated using noncompartmental analysis of data collected on the last day of each period. The combinations of RPV and DTG (n = 16) and of RPV and GSK1265744 (n = 11) were well tolerated; no grade 3 or 4 adverse events (AEs) or AE-related discontinuations were observed. The 90% confidence intervals for the area under the curve from time zero until the end of the dosage interval [AUC0-τ] and maximum concentration of drug in serum (Cmax) geometric mean ratios were within 0.8 to 1.25. Following administration of DTG + RPV, DTG and RPV Cτ increased by 22% and 21%, respectively. Following administration of GSK1265744 + RPV, RPV Cτ decreased 8%. DTG and GSK1265744 can be administered with RPV without dosage adjustment for either agent. These results support coadministration of RPV with DTG or GSK1265744 as either oral or long-acting depot injection regimens. (This study has been registered at ClinicalTrials.gov under registration no. NCT01467531.).

Dolutegravir versus raltegravir in antiretroviral-experienced, integrase-inhibitor-naive adults with HIV: week 48 results from the randomised, double-blind, non-inferiority SAILING study

BACKGROUND

Dolutegravir (GSK1349572), a once-daily HIV integrase inhibitor, has shown potent antiviral response and a favourable safety profile. We evaluated safety, efficacy, and emergent resistance in antiretroviral-experienced, integrase-inhibitor-naive adults with HIV-1 with at least two-class drug resistance.

METHODS

ING111762 (SAILING) is a 48 week, phase 3, randomised, double-blind, active-controlled, non-inferiority study that began in October, 2010. Eligible patients had two consecutive plasma HIV-1 RNA assessments of 400 copies per mL or higher (unless >1000 copies per mL at screening), resistance to two or more classes of antiretroviral drugs, and had one to two fully active drugs for background therapy. Participants were randomly assigned (1:1) to once-daily dolutegravir 50 mg or twice-daily raltegravir 400 mg, with investigator-selected background therapy. Matching placebo was given, and study sites were masked to treatment assignment. The primary endpoint was the proportion of patients with plasma HIV-1 RNA less than 50 copies per mL at week 48, evaluated in all participants randomly assigned to treatment groups who received at least one dose of study drug, excluding participants at one site with violations of good clinical practice. Non-inferiority was prespecified with a 12% margin; if non-inferiority was established, then superiority would be tested per a prespecified sequential testing procedure. A key prespecified secondary endpoint was the proportion of patients with treatment-emergent integrase-inhibitor resistance. The trial is registered at ClinicalTrials.gov, NCT01231516.

FINDINGS

Analysis included 715 patients (354 dolutegravir; 361 raltegravir). At week 48, 251 (71%) patients on dolutegravir had HIV-1 RNA less than 50 copies per mL versus 230 (64%) patients on raltegravir (adjusted difference 7·4%, 95% CI 0·7 to 14·2); superiority of dolutegravir versus raltegravir was then concluded (p=0·03). Significantly fewer patients had virological failure with treatment-emergent integrase-inhibitor resistance on dolutegravir (four vs 17 patients; adjusted difference -3·7%, 95% CI -6·1 to -1·2; p=0·003). Adverse event frequencies were similar across groups; the most commonly reported events for dolutegravir versus raltegravir were diarrhoea (71 [20%] vs 64 [18%] patients), upper respiratory tract infection (38 [11%] vs 29 [8%]), and headache (33 [9%] vs 31 [9%]). Safety events leading to discontinuation were infrequent in both groups (nine [3%] dolutegravir, 14 [4%] raltegravir).

INTERPRETATION

Once-daily dolutegravir, in combination with up to two other antiretroviral drugs, is well tolerated with greater virological effect compared with twice-daily raltegravir in this treatment-experienced patient group.

FUNDING

ViiV Healthcare.

Once-daily dolutegravir versus raltegravir in antiretroviral-naive adults with HIV-1 infection: 48 week results from the randomised, double-blind, non-inferiority SPRING-2 study

BACKGROUND

Dolutegravir (S/GSK1349572) is a once-daily HIV integrase inhibitor with potent antiviral activity and a favourable safety profile. We compared dolutegravir with HIV integrase inhibitor raltegravir, as initial treatment for adults with HIV-1.

METHODS

SPRING-2 is a 96 week, phase 3, randomised, double-blind, active-controlled, non-inferiority study that began on Oct 19, 2010, at 100 sites in Canada, USA, Australia, and Europe. Treatment-naive adults (aged ≥ 18 years) with HIV-1 infection and HIV-1 RNA concentrations of 1000 copies per mL or greater were randomly assigned (1:1) via a computer-generated randomisation sequence to receive either dolutegravir (50 mg once daily) or raltegravir (400 mg twice daily). Study drugs were given with coformulated tenofovir/emtricitabine or abacavir/lamivudine. Randomisation was stratified by screening HIV-1 RNA (≤ 100,000 copies per mL or >100,000 copies per mL) and nucleoside reverse transcriptase inhibitor backbone. Investigators were not masked to HIV-1 RNA results before randomisation. The primary endpoint was the proportion of participants with HIV-1 RNA less than 50 copies per mL at 48 weeks, with a 10% non-inferiority margin. Main secondary endpoints were changes from baseline in CD4 cell counts, incidence and severity of adverse events, changes in laboratory parameters, and genotypic or phenotypic evidence of resistance. Our primary analysis was by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT01227824.

FINDINGS

411 patients were randomly allocated to receive dolutegravir and 411 to receive raltegravir and received at least one dose of study drug. At 48 weeks, 361 (88%) patients in the dolutegravir group achieved an HIV-1 RNA value of less than 50 copies per mL compared with 351 (85%) in the raltegravir group (adjusted difference 2·5%; 95% CI -2·2 to 7·1). Adverse events were similar between treatment groups. The most common events were nausea (59 [14%] patients in the dolutegravir group vs 53 [13%] in the raltegravir group), headache (51 [12%] vs 48 [12%]), nasopharyngitis (46 [11%] vs 48 [12%]), and diarrhoea (47 [11%] in each group). Few patients had drug-related serious adverse events (three [<1%] vs five [1%]), and few had adverse events leading to discontinuation (ten [2%] vs seven [2%] in each group). CD4 cell counts increased from baseline to week 48 in both treatment groups by a median of 230 cells per μL. Rates of graded laboratory toxic effects were similar. We noted no evidence of treatment-emergent resistance in patients with virological failure on dolutegravir, whereas of the patients with virologic failure who received raltegravir, one (6%) had integrase treatment-emergent resistance and four (21%) had nucleoside reverse transcriptase inhibitors treatment-emergent resistance.

INTERPRETATION

The non-inferior efficacy and similar safety profile of dolutegravir compared with raltegravir means that if approved, combination treatment with once-daily dolutegravir and fixed-dose nucleoside reverse transcriptase inhibitors would be an effective new option for treatment of HIV-1 in treatment-naive patients.

FUNDING

ViiV Healthcare.

Potential benefit of dolutegravir once daily: efficacy and safety

The viral integrase enzyme has recently emerged as a primary alternative target to block HIV-1 replication, and integrase inhibitors are considered a pivotal new class of antiretroviral drugs. Dolutegravir is an investigational next-generation integrase inhibitor showing some novel and intriguing characteristics, ie, it has a favorable pharmacokinetic profile with a prolonged intracellular half-life, rendering feasible once-daily dosing without the need for ritonavir boosting and without regard to meals. Moreover, dolutegravir is primarily metabolized via uridine diphosphate glucuronosyltranferase 1A1, with a minor component of the cytochrome P450 3A4 isoform, thereby limiting drug–drug interactions. Furthermore, its metabolic profile enables coadministration with most of the other available antiretroviral agents without dose adjustment. Recent findings also demonstrate that dolutegravir has significant activity against HIV-1 isolates with resistance mutations associated with raltegravir and/or elvitegravir. The attributes of once-daily administration and the potential to treat integrase inhibitor-resistant viruses make dolutegravir an interesting and promising investigational drug. In this review, the main concerns about the efficacy and safety of dolutegravir as well as its resistance profile are explored by analysis of currently available data from preclinical and clinical studies.

HIV Drug Resistance and the Advent of Integrase Inhibitors

This review focuses on the topic of HIV integrase inhibitors that are potent antiretroviral drugs that efficiently decrease viral load in patients. However, emergence of resistance mutations against this new class of drugs represents a threat to their long-term efficacy. Here, we provide new information about the most recent mutations identified and other mutations that confer resistance to several integrase inhibitors, such as new resistance mutations-for example, G118R, R263K, and S153Y-that have been identified through in vitro selection studies with second-generation integrase strand transfer inhibitors (INSTIs). These add to the three main resistance pathways involving mutations at positions Y143, N155, and Q148. Deep sequencing, structural modeling, and biochemical analyses are methods that currently help in the understanding of the mechanisms of resistance conferred by these mutations. Although the new resistance mutations appear to confer only low levels of cross-resistance to second-generation drugs, the Q148 pathway with numerous secondary mutations has the potential to significantly decrease susceptibility to all drugs of the INSTI family of compounds.

Resistance to HIV integrase inhibitors

PURPOSE OF REVIEW

HIV integrase inhibitors are potent antiretroviral drugs that efficiently decrease viral load in patients. Emergence of resistance mutations against this new class of drugs represents a threat to their long-term efficacy. The purpose of this review is to provide new information about the most recent mutations identified and other mutations that confer resistance to several integrase inhibitors.

RECENT FINDINGS

New resistance mutations, such as G118R, R263K and S153Y, have been recently identified through in-vitro selection studies with second-generation integrase strand-transfer inhibitors (INSTIs). These add to the three main resistance pathways involving mutations at positions Y143, N155 and Q148. Structural modeling, biochemical analyses and deep sequencing are methods that currently help in the understanding of the mechanisms of resistance conferred by these mutations. Although these new resistance mutations appear to confer only low levels of cross-resistance to second-generation drugs, the Q148 pathway with numerous secondary mutations has the potential to significantly decrease susceptibility to all drugs of the INSTI family.

SUMMARY

Recent mutations selected in vitro with second-generation INSTIs suggest the existence of low levels of cross-resistance between these drugs and first-generation compounds. In clinical practice, the emergence of mutations at position Q148 should be monitored whenever possible. More datasets are needed to assess the long-term efficacy of second-generation INSTIs in patients failing older INSTIs such as raltegravir and elvitegravir.