Impact of UGT1A1 polymorphisms on Raltegravir and its glucuronide plasma concentrations in a cohort of HIV-1 infected patients

Drug-drug interactions in HIV-infected patients receiving chemotherapy

INTRODUCTION

Coadministration of antiretrovirals and anti-cancer medications may present many complex clinical scenarios. This is characterized by the potential for drug-drug interactions (DDIs) and the challenges that arise in patient management. In this article, we investigate the potential for DDIs between antiretrovirals, including protease inhibitors (PIs), non-nucleoside reverse transcriptase inhibitors, nucleoside reverse transcriptase inhibitors (NRTIs), integrase strand transfer inhibitors (INSTIs), and anti-cancer medications.

AREAS COVERED

PubMed, Google Scholar, and Clinicaltrials.gov were searched for relevant articles in April 2024. Our review highlights PIs and NNRTIs as particularly prone to DDIs with anticancer agents, with implications for efficacy and toxicity of concomitant cancer therapy. We explain the mechanisms for interactions, emphasizing the significance of pharmacokinetic effects and enzyme induction or inhibition. We discuss clinical challenges encountered in the management of patients receiving combined ART and cancer therapy regimens.

EXPERT OPINION

Data are lacking for potential DDIs between antiretroviral and anti-cancer agents. While some interactions are documented, others are theoretical and based on the pharmacokinetic properties of the medications. Awareness of these interactions, inter-collaborative care between healthcare providers, and standardized treatment guidelines are all crucial for achieving optimal treatment outcomes and ensuring the well-being of patients with HIV/AIDS and cancer comorbidities.

Comparison of Relative Activity versus Relative Expression Factors (RAF versus REF) in Predicting Glucuronidation Mediated Drug Clearance Using Recombinant UGTs

PURPOSE

Predicting the quantitative fraction of glucuronidation (fgluc) by individual UDP-glucuronosyltransferase enzymes (UGTs) is challenging due to the lack of selective inhibitors and inconsistent activity of recombinant UGT systems (rUGTs). Our study compares the relative expression versus activity factors (REF versus RAF) to predict fgluc based on rUGT data to human liver and intestinal microsomes (HLM and HIM).

METHODS

REF scalars were derived from a previous in-house proteomics study for eleven UGT enzymes (UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A9, UGT1A10, UGT2B4, UGT2B7, UGT2B10, UGT2B15, and UGT2B17), whereas RAF was calculated by measuring activities in rUGTs to microsomes of selective UGT probe substrates. Protein-normalized activity factor (pnAF) values were generated after correcting activity of individual UGTs to their corresponding protein abundance. The utility of REF and RAF in predicting fgluc was assessed for three UGT substrates-diclofenac, vorinostat, and raltegravir.

RESULTS

The REF values ranged from 0.02 to 1.75, RAF based on activity obtained in rUGTs to HLM/HIM were from 0.1 to 274. pnAF values were ~ 5 to 80-fold, except for UGT2B4 and UGT2B15, where pnAF was ~ 180 and > 1000, respectively. The results revealed confounding effect of differential specific activities (per pmol) of rUGTs in fgluc prediction.

CONCLUSION

The data suggest that the activity of UGT enzymes was significantly lower when compared to their activity in microsomes at the same absolute protein amount (pmol). Collectively, results of this study demonstrate poor and variable specific activity of different rUGTs (per pmol protein), as determined by pnAF values, which should be considered in fgluc scaling.

Liver Steatosis is Prevalent in Lean People With HIV and Associated With Exposure to Antiretroviral Treatment-A Cross-sectional Study

Background

Steatotic liver disease is suggested to have a higher prevalence and severity in people with HIV (PHIV), including in those with a normal body mass index (BMI). In this study, we used data from the 2000HIV cohort to (1) assess the prevalence of liver steatosis and fibrosis in lean versus overweight/obese PHIV and (2) assess associations in these subgroups between steatosis and fibrosis with traditional risk factors and HIV-specific characteristics.

Methods

The 2000HIV study cohort comprises 1895 virally suppressed PHIV that were included between 2019 and 2021 in 4 HIV treatment centers in the Netherlands. The majority (58.5%) underwent vibration-controlled transient elastography for the assessment of liver steatosis and fibrosis. The prevalence of steatosis (controlled attenuation parameter ≥263 dB/m) and fibrosis (liver stiffness measurement ≥7.0 kPa) was estimated. Multiple factors including HIV characteristics and antiretroviral drugs were tested in a logistic regression model for association with steatosis and fibrosis. Analyses were performed separately for lean (Asian descent: BMI < 23 kg/m2, other descent: BMI < 25 kg/m2) and overweight/obese (other BMI) participants.

Results

Of 1050 PHIV including 505 lean and 545 overweight/obese PHIV, liver steatosis was observed in 37.7% of the overall study population, 19.7% of lean, and 54% of overweight/obese PHIV, whereas fibrosis was observed in 9.0% of the overall study population, 5.9% of lean, and 12.0% of overweight/obese PHIV.All associations with fibrosis and most associations with steatosis concerned metabolic factors such as type 2 diabetes mellitus (overall population: adjusted odds ratio [aOR] for steatosis: 2.3 [1.21-4.4], P = .011; aOR for fibrosis: 3.7 [1.82-7.53], P < .001). Furthermore, in lean PLHIV, liver steatosis was associated with CD4 and CD8 counts at enrollment, dual therapy, and history of treatment with raltegravir (aOR: 3.6 [1.53-8.47], P = .003), stavudine (aOR: 3.73 [1.69-8.2], P = .001), and indinavir (aOR: 3.86 [1.59-9.37], P = .003). These associations were not observed in overweight/obese PHIV.

Conclusions

Liver steatosis was highly prevalent, affecting approximately one-fifth of lean PHIV and half of overweight/obese PHIV. Fibrosis was observed in a minority. Both steatosis and fibrosis were associated with traditional metabolic risk factors. In addition, (prior) exposure to specific antiretroviral drugs was associated liver steatosis in lean, but not in overweight/obese PHIV. Implementing increased screening protocols could enhance the identification of steatotic liver disease in lean PHIV.

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.

ADME, Pharmacokinetic Scaling, Pharmacodynamic and Prediction of Human Dose and Regimen of Novel Antiviral Drugs

The search for new drugs is an extremely time-consuming and expensive endeavour. Much of that time and money go into generating predictive human pharmacokinetic profiles from preclinical efficacy and safety animal data. These pharmacokinetic profiles are used to prioritize or minimize the attrition at later stages of the drug discovery process. In the area of antiviral drug research, these pharmacokinetic profiles are equally important for the optimization, estimation of half-life, determination of effective dose, and dosing regimen, in humans. In this article we have highlighted three important aspects of these profiles. First, the impact of plasma protein binding on two primary pharmacokinetic parameters-volume of distribution and clearance. Second, interdependence of primary parameters on unbound fraction of the drug. Third, the ability to extrapolate human pharmacokinetic parameters and concentration time profiles from animal profiles.

Influence of UGT1A1 and SLC22A6 polymorphisms on the population pharmacokinetics and pharmacodynamics of raltegravir in HIV-infected adults: a NEAT001/ANRS143 sub-study

Using concentration-time data from the NEAT001/ARNS143 study (single sample at week 4 and 24), we determined raltegravir pharmacokinetic parameters using nonlinear mixed effects modelling (NONMEM v.7.3; 602 samples from 349 patients) and investigated the influence of demographics and SNPs (SLC22A6 and UGT1A1) on raltegravir pharmacokinetics and pharmacodynamics. Demographics and SNPs did not influence raltegravir pharmacokinetics and no significant pharmacokinetic/pharmacodynamic relationships were observed. At week 96, UGT1A1*28/*28 was associated with lower virological failure (p = 0.012), even after adjusting for baseline CD4 count (p = 0.048), but not when adjusted for baseline HIV-1 viral load (p = 0.082) or both (p = 0.089). This is the first study to our knowledge to assess the influence of SNPs on raltegravir pharmacodynamics. The lack of a pharmacokinetic/pharmacodynamic relationship is potentially an artefact of raltegravir's characteristic high inter and intra-patient variability and also suggesting single time point sampling schedules are inadequate to thoroughly assess the influence of SNPs on raltegravir pharmacokinetics.

Role of Genetic Polymorphisms in Drug-Metabolizing Enzyme-Mediated Toxicity and Pharmacokinetic Resistance to Anti-Cancer Agents: A Review on the Pharmacogenomics Aspect

The inter-individual differences in cancer susceptibility are somehow correlated with the genetic differences that are caused by the polymorphisms. These genetic variations in drug-metabolizing enzymes/drug-inactivating enzymes may negatively or positively affect the pharmacokinetic profile of chemotherapeutic agents that eventually lead to pharmacokinetic resistance and toxicity against anti-cancer drugs. For instance, the CYP1B1*3 allele is associated with CYP1B1 overexpression and consequent resistance to a variety of taxanes and platins, while 496T>G is associated with lower levels of dihydropyrimidine dehydrogenase, which results in severe toxicities related to 5-fluorouracil. In this context, a pharmacogenomics approach can be applied to ascertain the role of the genetic make-up in a person's response to any drug. This approach collectively utilizes pharmacology and genomics to develop effective and safe medications that are devoid of resistance problems. In addition, recently reported genomics studies revealed the impact of many single nucleotide polymorphisms in tumors. These studies emphasized the importance of single nucleotide polymorphisms in drug-metabolizing enzymes on the effect of anti-tumor drugs. In this review, we discuss the pharmacogenomics aspect of polymorphisms in detail to provide an insight into the genetic manipulations in drug-metabolizing enzymes that are responsible for pharmacokinetic resistance or toxicity against well-known anti-cancer drugs. Special emphasis is placed on different deleterious single nucleotide polymorphisms and their effect on pharmacokinetic resistance. The information provided in this report may be beneficial to researchers, especially those who are working in the field of biotechnology and human genetics, in rationally manipulating the genetic information of patients with cancer who are undergoing chemotherapy to avoid the problem of pharmacokinetic resistance/toxicity associated with drug-metabolizing enzymes.

Safety and efficacy of pharmacotherapy containing INSTIs and chemotherapy drugs in people living with HIV and concomitant colorectal cancer

BACKGROUND

Previous clinical data have shown that raltegravir-based antiretroviral therapy (ART) with fewer drug-drug interactions (DDIs) and adverse events (AEs) is a good regimen in patients with HIV infection who need cancer chemotherapy. There are currently few data on ART regimens that include Integrase inhibitors (INSTIs) other than RAL among this patient subgroup.

METHODS

We evaluated the safety and efficacy of different kinds of INSTI-based regimens among patients with HIV and concomitant colorectal cancer (CRC) who received antineoplastic agents.

RESULTS

From January 2020 to November 2021, 66 patients were enrolled. The patients were divided into three groups: 20 patients treated with dolutegravir (DTG)/lamivudine (3TC)/tenofovir (TDF) (group I), 24 patients treated with DTG/albuvirtide (ABT) (group II), and 22 patients treated with bictegravir (BIC)/tenofovir alafenamide (TAF)/emtricitabine (FTC) (group III). The majority of AEs during treatment were of grade 1-2. Treatment-related AEs of grade 3-4 occurred in 6 patients (9.09%), and no grade 5 AEs occurred. The most common AEs were nausea (100%) and neutrophils (84.85%) attributed to anticancer agents, and there was no significant difference in the incidence of these AEs among the three groups (P > 0.05). Viral load rebound was not observed among pretreated patients during chemotherapy. The viral load of untreated patients who started their ART concomitant with chemotherapy almost decreased to the lower limit of detection 6 months after ART initiation (only one patient in group III had a viral load of 102 copies/ml). At the 6th month, the CD4 count in group I decreased significantly from baseline (P < 0.05). However, the change in CD4 count was not significant in group II (P = 0.457) or group III (P = 0.748).

CONCLUSIONS

DTG- or BIC-containing regimens are good options for patients with HIV and concomitant CRC.

Pharmacokinetic interaction between raltegravir and rifampicin in an infant with HIV exposed to active TB: a case report

We report a case of an infant with HIV receiving raltegravir granules for oral suspension and rifampicin-based TB prophylaxis. Raltegravir trough levels remained subtherapeutic and viral load increased during concurrent rifampicin therapy despite using double-dosed raltegravir. Even after rifampicin therapy, a higher dose was needed. This highlights the importance of therapeutic drug monitoring and dose adjustments of raltegravir in infants with rifampicin as comedication.

UGT1A1 Gene Polymorphism Contributes as a Risk Factor for Lung Cancer: A Pilot Study with Patients from the Amazon

Lung cancer is one of the most frequent neoplasms in the world. Because it is a complex disease, its formation occurs in several stages, stemming from interactions between environmental risk factors, such as smoking, and individual genetic susceptibility. Our objective was to investigate associations between a UGT1A1 gene polymorphism (rs8175347) and lung cancer risk in an Amazonian population. This is a pilot study, case-controlled study, which included 276 individuals with cancer and without cancer. The samples were analyzed for polymorphisms of the UGT1A1 gene (rs8175347) and genotyped in PCR, followed by fragment analysis in which we applied a previously developed set of informative ancestral markers. We used logistic regression to identify differences in allelic and genotypic frequencies between individuals. Individuals with the TA7 allele have an increased chance of developing lung adenocarcinoma (p = 0.035; OR: 2.57), as well as those with related genotypes of reduced or low enzymatic activity: TA6/7, TA5/7, and TA7/7 (p = 0.048; OR: 8.41). Individuals with homozygous TA7/7 have an increased chance of developing squamous cell carcinoma of the lung (p = 0.015; OR: 4.08). Polymorphism in the UGT1A1 gene (rs8175347) may contribute as a risk factor for adenocarcinoma and lung squamous cell carcinoma in the population of the Amazon region.

When special populations intersect with drug-drug interactions: Application of physiologically-based pharmacokinetic modeling in pregnant populations

Pregnancy results in significant physiological changes that vary across trimesters and into the postpartum period, and may result in altered disposition of endogenous substances and drug pharmacokinetics. Pregnancy represents a unique special population where physiologically-based pharmacokinetic modeling (PBPK) is well suited to mechanistically explore pharmacokinetics and dosing paradigms without subjecting pregnant women or their fetuses to extensive clinical studies. A critical review of applications of pregnancy PBPK models (pPBPK) was conducted to understand its current status for prediction of drug exposure in pregnant populations and to identify areas of further expansion. Evaluation of existing pPBPK modeling efforts highlighted improved understanding of cytochrome P450 (CYP)-mediated changes during pregnancy and identified knowledge gaps for non-CYP enzymes and the physiological changes of the postpartum period. Examples of the application of pPBPK beyond simple dose regimen recommendations are limited, particularly for prediction of drug-drug interactions (DDI) or differences between genotypes for polymorphic drug metabolizing enzymes. A raltegravir pPBPK model implementing UGT1A1 induction during the second and third trimesters of pregnancy was developed in the current work and verified against clinical data. Subsequently, the model was used to explore UGT1A1-related DDI risk with atazanavir and rifampicin along with the effect of enzyme genotype on raltegravir apparent clearance. Simulations of pregnancy-related induction of UGT1A1 either exacerbated UGT1A1 induction by rifampicin or negated atazanavir UGT1A1 inhibition. This example illustrated the advantages of pPBPK modeling for mechanistic evaluation of complex interplays of pregnancy- and drug-related effects in support of model-informed approaches in drug development.

Identification of Novel UGT1A1 Variants Including UGT1A1 454C>A through the Genotyping of Healthy Participants of the HPTN 077 Study

Cabotegravir (CAB) is an integrase strand-transfer inhibitor of HIV that has proven effective for HIV treatment and prevention in a long-acting injectable formulation, typically preceded by an oral formulation lead-in phase. Previous in vitro studies have demonstrated that CAB is primarily metabolized via glucuronidation by uridine diphosphate glucuronosyltransferase (UGT) 1A1 and 1A9. In this study, we performed next-generation sequencing of genomic DNA isolated from the HPTN 077 participants to explore the variants within UGT1A1 and UGT1A9. Additionally, to enable correlation of UGT1A1 and UGT1A9 genotypes with plasma CAB-glucuronide levels, we quantified glucuronidated CAB following both oral administration of CAB and intramuscular injection of long-acting CAB. From these studies, 48 previously unreported variants of UGT1A1 and UGT1A9 were detected. Notably, 5/68 individuals carried a UGT1A1 454C>A variant that resulted in amino acid substitution P152T, and the use of in silico tools predicted a deleterious effect of the P152T substitution. Thus, the impact of this mutant on a range of UGT1A1 substrates was tested using a COS-7 cell-based assay. The glucuronide conjugates of CAB, dolutegravir, and raltegravir, were not formed in the COS-7 cells expressing the UGT1A1 P152T mutant. Further, formation of glucuronides of raloxifene and 7-ethyl-10-hydroxycamptothecin were reduced in the cells expressing the UGT1A1 P152T mutant. Using the same approach, we tested the activities of two UGT1A9 mutants, UGT1A9 H217Y and UGT1A9 R464G, and found that these mutations were tolerated and decreased function, respectively. These data provide insight into previously unreported genetic variants of UGT1A1 and UGT1A9.

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.

Effect of Pregnancy on Unbound Raltegravir Concentrations in the ANRS 160 RalFe Trial

A population pharmacokinetic model was developed to explore the pharmacokinetics modification of unbound raltegravir during pregnancy. The RalFe ANRS160 study was a nonrandomized, open-label, multicenter trial enrolling HIV-infected pregnant women receiving a combined antiretroviral regimen containing 400 mg raltegravir twice daily. Biological samples were collected during the third trimester of pregnancy (between 30 and 37 weeks of gestational age) and at postpartum (4 to 6 weeks after delivery). A population pharmacokinetic model was developed with Monolix software. A total of 360 plasma samples were collected from 43 women during pregnancy and postpartum. The unbound raltegravir was described by a one-compartment model with a transit compartment with first-order absorption, evolving to bound raltegravir (by a linear binding to albumin) or metabolism to RAL-glucuronide or to a first-order elimination, with a circadian rhythm. During pregnancy, the absorption was decreased and delayed and the raltegravir elimination clearance and glucuronidation increased by 37%. Median total and unbound area under the curve from 0 to 12 h significantly decreased by 36% and 27% during pregnancy. Median total trough concentration (C _trough) decreased significantly in the evening (28%); however, the median total C _trough in the morning, unbound C _trough in the morning, and unbound C _trough in the evening showed a nonsignificant decrease of 16%, 1%, and 15%, respectively, during pregnancy compared to the postpartum period. This is the first study reporting the pharmacokinetics of unbound raltegravir during pregnancy. As unbound C _trough did not significantly decrease during the third trimester, the pregnancy effect on raltegravir unbound concentrations was not considered clinically relevant. (This study has been registered at ClinicalTrials.gov under identifier NCT02099474.).

Determination of raltegravir and raltegravir glucuronide in human plasma and urine by LC-MS/MS with application in a maternal-fetal pharmacokinetic study

Raltegravir (RAL) is a HIV-integrase inhibitor recommended for treatment of HIV type 1 infection during pregnancy. The elimination of RAL to RAL glucuronide (RAL GLU) is mediated primarily by UDP glucuronosyltransferase 1A1 (UGT1A1). The present study shows the development and validation of 4 different methods for the analysis of RAL and RAL GLU in plasma and in urine samples. The methods were applied to evaluate the maternal-fetal pharmacokinetics of RAL and RAL GLU in a HIV-infected pregnant woman receiving RAL 400 mg twice daily. The sample preparation for RAL and RAL GLU analysis in 25 μL plasma and 100 μL diluted urine (10-fold with water containing 0.1% formic acid) were carried out by protein precipitation procedure. RAL and RAL GLU generate similar product mass fragments and require separation in the chromatographic system, so a suitable resolution was achieved for unchanged RAL and RAL GLU employing Ascentis Express C18 (75 × 4.6 mm, 2.7 μm) for both plasma and urine samples. The methods showed linearities at the ranges of 0.1-13.5 μg/mL RAL and 0.15-19.5 μg/mL RAL GLU in urine and 10-2000 ng/mL RAL and 2.5-800 RAL GLU in plasma. Precise and accurate evaluation showed coefficients of variation and relative errors ≤ 15%. The methods have been successfully applied in a maternal-fetal pharmacokinetic study.

Mechanistic Assessment of Extrahepatic Contributions to Glucuronidation of Integrase Strand Transfer Inhibitors

Integrase strand transfer inhibitor (INSTI)-based regimens dominate initial human immunodeficiency virus treatment. Most INSTIs are metabolized predominantly via UDP-glucuronosyltransferases (UGTs). For drugs predominantly metabolized by UGTs, including INSTIs, in vitro data recovered from human liver microsomes (HLMs) alone often underpredict human oral clearance. While several factors may contribute, extrahepatic glucuronidation may contribute to this underprediction. Thus, we comprehensively characterized the kinetics for the glucuronidation of INSTIs (cabotegravir, dolutegravir, and raltegravir) using pooled human microsomal preparations from liver (HLMs), intestine (HIMs), and kidney (HKMs) tissues; human embryonic kidney 293 cells expressing individual UGTs; and recombinant UGTs. In vitro glucuronidation of cabotegravir (HLMs≈HKMs>>>HIMs), dolutegravir (HLMs>HIMs>>HKMs), and raltegravir (HLMs>HKMs>> HIMs) occurred in hepatic and extrahepatic tissues. The kinetic data from expression systems suggested the major enzymes in each tissue: hepatic UGT1A9 > UGT1A1 (dolutegravir and raltegravir) and UGT1A1 (cabotegravir), intestinal UGT1A3 > UGT1A8 > UGT1A1 (dolutegravir) and UGT1A8 > UGT1A1 (raltegravir), and renal UGT1A9 (dolutegravir and raltegravir). Enzymes catalyzing cabotegravir glucuronidation in the kidney and intestine could not be identified unequivocally. Using data from dolutegravir glucuronidation as a prototype, a "bottom-up" physiologically based pharmacokinetic model was developed in a stepwise approach and predicted dolutegravir oral clearance within 4.5-fold (hepatic data only), 2-fold (hepatic and intestinal data), and 32% (hepatic, intestinal, and renal data). These results suggest clinically meaningful glucuronidation of dolutegravir in tissues other than the liver. Incorporation of additional novel mechanistic and physiologic underpinnings of dolutegravir metabolism along with in silico approaches appears to be a powerful tool to accurately predict the clearance of dolutegravir from in vitro data.

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.

The clinical pharmacology of integrase inhibitors

Introduction: Treatment of HIV infection has consistently evolved in the last three decades. A steady improvement in efficacy tolerability, safety, and practical aspects of treatment intake has made HIV infection much easier to manage over the long term, and in optimal treatment conditions the life expectancy of persons living with HIV infection now approaches the values of the general population. The last category of antiretrovirals to be fully developed for clinical use is the one of strand-transfer integrase inhibitors (INSTIs). Areas covered: In this review, the evolution of the knowledge on INSTIs use in the clinical setting is reviewed, analyzed, and interpreted. Emphasis is placed on the properties possibly accounting for several superiority results achieved by INSTIs in non-inferiority designed comparative clinical trials, which led to their inclusion as first line options in all versions of HIV therapeutic guidelines. Expert commentary: Some unprecedented clinical-pharmacological properties of INSTIs, such as their rapid and sustained action against HIV replication, the optimal tolerability and safety profile and a clinically proven robust genetic barrier are the main factors justifying the successful clinical use of INSTIs. Based on these unique features, novel INSTIs-based treatment modalities are being developed, including the reduction of antiretroviral regimens to two drugs only.