Intracellular and plasma steady-state pharmacokinetics of raltegravir, darunavir, etravirine and ritonavir in heavily pre-treated HIV-infected patients

Investigation of etravirine uptake and distribution in single aortic endothelial cells in vitro using Raman imaging

Etravirine (ETV) is an antiretroviral agent that belongs to the class of non-nucleoside reverse transcriptase inhibitors. This study explores the uptake and distribution of ETV in human aortic endothelial cells (HAECs) using Raman spectroscopy combined with chemometrics. The distinctive chemical structure of ETV facilitates tracking of its uptake by observing the Raman band at 2225 cm-1 in the Raman-silent region. The perinuclear distribution pattern in HAECs depends on drug concentration and incubation time. The uptake of ETV is observed within 5 minutes at a concentration of 10 μM, as evidenced by Raman images. Lower ETV concentrations, reflective of those found in human plasma, are detectable in HAECs by applying chemometric methods to Raman spectra from the perinuclear region. The ETV accumulation process is crucial in advancing our understanding of the drug's impact on biochemical alterations within endothelial cells. Additionally, ETV emerges as a promising Raman reporter for marking subcellular compartments, leveraging the 2225 cm-1 band in the cellular Raman silent region. This research contributes valuable insights into the behavior of ETV at the subcellular level, shedding light on its potential applications and impact on subcellular dynamics.

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.

Everolimus Concentration in Saliva to Predict Stomatitis: A Feasibility Study in Patients with Cancer

BACKGROUND

Most patients with cancer treated with everolimus experience stomatitis, which seriously affects the quality of life. The salivary concentrations of everolimus may predict the incidence and severity of stomatitis. The authors aimed to examine whether it was feasible to quantify the everolimus concentration in saliva and subsequently use it to predict stomatitis.

METHODS

Saliva and whole blood samples were taken from patients with cancer, who were treated with everolimus in the dosage of either 10 mg once a day or 5 mg twice a day. Everolimus concentrations in saliva samples were measured by liquid chromatography-tandem mass spectrometry. A published population pharmacokinetic model was extended with the everolimus concentration in saliva to assess any association between everolimus in the blood and saliva. Subsequently, the association between the occurrence of stomatitis and the everolimus concentration in saliva was studied.

RESULTS

Eleven patients were included in this study; saliva samples were available from 10 patients, including 3 patients with low-grade stomatitis. Everolimus concentrations were more than 100-fold lower in saliva than in whole blood (accumulation ratio 0.00801 and relative standard error 32.5%). Interindividual variability (67.7%) and residual unexplained variability (84.0%) were high. The salivary concentration of everolimus tended to be higher in patients with stomatitis, 1 hour postdose ( P = 0.14).

CONCLUSIONS

Quantification of the everolimus concentration in saliva was feasible and revealed a nonsignificant correlation between everolimus concentration in the saliva and the occurrence of stomatitis. If future research proves this relationship to be significant, the everolimus concentration in the saliva may be used as an early predictor of stomatitis without invasive sampling. Thereby, in patients with high salivary everolimus concentrations, precautions can be taken to decrease the incidence and severity of stomatitis.

Quantitation of methotrexate polyglutamates in human whole blood, erythrocytes and leukocytes collected via venepuncture and volumetric absorptive micro-sampling: a green LC-MS/MS-based method

Low-dose methotrexate (MTX) plays a key role in treatment of rheumatoid arthritis. However, not all patients respond satisfactorily, and no therapeutic drug monitoring has been implemented in clinical practice, despite the fact that MTX therapy has now been available for decades. Analysis of individual intracellular MTX metabolites among rheumatoid arthritis (RA) patients is hampered by the low intracellular concentrations of MTX-PGs which require a highly sensitive method to quantify. Here, we present a rapid and highly sensitive LC (HILIC) MS/MS method with LLOQ 0.1 nM, 0.8 nmol/L for each metabolite of MTX-PG_1-5 and MTX-PG_6-7 respectively. Over a linear range of 0.1-100 nM, 0.8-100 nmol/L for each metabolite of MTX-PG_1-5 and MTX-PG_6-7, respectively, the inter- and intra- accuracy and precision were within 15% of the nominal value for all MTX metabolites. The presented assay was used to assess and compare MTX metabolite concentrations extracted from four different matrices: red blood cells, plasma, peripheral blood mononuclear cells, and whole blood that have been collected either using traditional venepuncture or volumetric absorptive micro-sampling (VAMS) sampling techniques. The presented method not only improves analyte coverage and sensitivity as compared to other published methods; it also improves the greenness.

Toward Consensus on Correct Interpretation of Protein Binding in Plasma and Other Biological Matrices for COVID-19 Therapeutic Development

The urgent global public health need presented by severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) has brought scientists from diverse backgrounds together in an unprecedented international effort to rapidly identify interventions. There is a pressing need to apply clinical pharmacology principles and this has already been recognized by several other groups. However, one area that warrants additional specific consideration relates to plasma and tissue protein binding that broadly influences pharmacokinetics and pharmacodynamics. The principles of free drug theory have been forged and applied across drug development but are not currently being routinely applied for SARS-CoV-2 antiviral drugs. Consideration of protein binding is of critical importance to candidate selection but requires correct interpretation, in a drug-specific manner, to avoid either underinterpretation or overinterpretation of its consequences. This paper represents a consensus from international researchers seeking to apply historical knowledge, which has underpinned highly successful antiviral drug development for other viruses, such as HIV and hepatitis C virus for decades.

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.

Exploration of Reduced Doses and Short-Cycle Therapy for Darunavir/Cobicistat in Patients with HIV Using Population Pharmacokinetic Modeling and Simulations

BACKGROUND AND OBJECTIVES

Protease inhibitors such as darunavir are an important therapeutic option in the anti-human immunodeficiency virus arsenal. Current dosage guidelines recommend using cobicistat- or ritonavir-boosted darunavir 800 mg every 24 h (q24h) in protease inhibitor-naïve patients, or ritonavir-boosted darunavir 600 mg q12h in experienced patients. However, darunavir displays a large, poorly characterized, inter-individual pharmacokinetic variability. The objectives of this study were to investigate the pharmacokinetics of darunavir and to elucidate the sources of its inter-individual variability using population pharmacokinetic modeling. Then, to determine the appropriateness of current treatment guidelines and the feasibility of alternative dosing regimens in a representative cohort of adult patients using simulations.

METHODS

Sparse pharmacokinetic samples were collected in 127 patients with human immunodeficiency virus type 1 infection, then supplemented with rich sampling data from a subset of 12 individuals. Data were analyzed using the nonlinear mixed-effects modeling software NONMEM. The effect of reduced doses (600 mg q24h and 400 mg q24h) or reduced frequency of administration (800 mg q24h for 5 days followed by 2 days of treatment interruption) was simulated.

RESULTS

Our model adequately described the pharmacokinetics of darunavir. Predictors of individual exposure were CYP3A5*3 and SLCO3A1 rs8027174 genotypes, sex, and alpha-1 acid glycoprotein level. No relationship was apparent between darunavir area under the curve and treatment efficacy or safety. For reduced dose regimens, darunavir concentrations remained above the protein binding-corrected EC₅₀ in the majority of subjects. More stringent pharmacokinetic targets were not reached in a significant proportion of patients.

CONCLUSIONS

These results add to the growing body of evidence that darunavir-based therapy could be simplified to reduce costs and toxicity, as well as to improve patient compliance. However, the heterogeneity in pharmacokinetic response should be considered when assessing whether individual patients could benefit from a particular regimen, for instance through the use of population pharmacokinetic models.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT03101644, date of registration: 5 April, 2017.

Computational screening for potential drug candidates against the SARS-CoV-2 main protease

Background: SARS-CoV-2 is the causal agent of the current coronavirus disease 2019 (COVID-19) pandemic. They are enveloped, positive-sense, single-stranded RNA viruses of the Coronaviridae family. Proteases of SARS-CoV-2 are necessary for viral replication, structural assembly, and pathogenicity. The approximately 33.8 kDa M pro protease of SARS-CoV-2 is a non-human homologue and is highly conserved among several coronaviruses, indicating that M pro could be a potential drug target for Coronaviruses. Methods: Herein, we performed computational ligand screening of four pharmacophores (OEW, remdesivir, hydroxychloroquine and N3) that are presumed to have positive effects against SARS-CoV-2 M pro protease (6LU7), and also screened 50,000 natural compounds from the ZINC Database dataset against this protease target. Results: We found 40 pharmacophore-like structures of natural compounds from diverse chemical classes that exhibited better affinity of docking as compared to the known ligands. The 11 best selected ligands, namely ZINC1845382, ZINC1875405, ZINC2092396, ZINC2104424, ZINC44018332, ZINC2101723, ZINC2094526, ZINC2094304, ZINC2104482, ZINC3984030, and ZINC1531664, are mainly classified as beta-carboline, alkaloids, and polyflavonoids, and all displayed interactions with dyad CYS145 and HIS41 from the protease pocket in a similar way as other known ligands. Conclusions: Our results suggest that these 11 molecules could be effective against SARS-CoV-2 protease and may be subsequently tested in vitro and in vivo to develop novel drugs against this virus.

Computational screening for potential drug candidates against the SARS-CoV-2 main protease

Background: SARS-CoV-2 is the causal agent of the current coronavirus disease 2019 (COVID-19) pandemic. They are enveloped, positive-sense, single-stranded RNA viruses of the Coronaviridae family. Proteases of SARS-CoV-2 are necessary for viral replication, structural assembly, and pathogenicity. The approximately 33.8 kDa M pro protease of SARS-CoV-2 is a non-human homologue and is highly conserved among several coronaviruses, indicating that M pro could be a potential drug target for Coronaviruses. Methods: Herein, we performed computational ligand screening of four pharmacophores (OEW, remdesivir, hydroxychloroquine and N3) that are presumed to have positive effects against SARS-CoV-2 M pro protease (6LU7), and also screened 50,000 natural compounds from the ZINC Database dataset against this protease target. Results: We found 40 pharmacophore-like structures of natural compounds from diverse chemical classes that exhibited better affinity of docking as compared to the known ligands. The 11 best selected ligands, namely ZINC1845382, ZINC1875405, ZINC2092396, ZINC2104424, ZINC44018332, ZINC2101723, ZINC2094526, ZINC2094304, ZINC2104482, ZINC3984030, and ZINC1531664, are mainly classified as beta-carboline, alkaloids, and polyflavonoids, and all displayed interactions with dyad CYS145 and HIS41 from the protease pocket in a similar way as other known ligands. Conclusions: Our results suggest that these 11 molecules could be effective against SARS-CoV-2 protease and may be subsequently tested in vitro and in vivo to develop novel drugs against this virus.

Prediction of Fetal Darunavir Exposure by Integrating Human Ex-Vivo Placental Transfer and Physiologically Based Pharmacokinetic Modeling

Background

Fetal antiretroviral exposure is usually derived from the cord-to-maternal concentration ratio. This static parameter does not provide information on the pharmacokinetics in utero, limiting the assessment of a fetal exposure–effect relationship.

Objective

The aim of this study was to incorporate placental transfer into a pregnancy physiologically based pharmacokinetic model to simulate and evaluate fetal darunavir exposure at term.

Methods

An existing and validated pregnancy physiologically based pharmacokinetic model of maternal darunavir/ritonavir exposure was extended with a feto-placental unit. To parameterize the model, we determined maternal-to-fetal and fetal-to-maternal darunavir/ritonavir placental clearance with an ex-vivo human cotyledon perfusion model. Simulated maternal and fetal pharmacokinetic profiles were compared with observed clinical data to qualify the model for simulation. Next, population fetal pharmacokinetic profiles were simulated for different maternal darunavir/ritonavir dosing regimens.

Results

An average (±standard deviation) maternal-to-fetal cotyledon clearance of 0.91 ± 0.11 mL/min and fetal-to-maternal clearance of 1.6 ± 0.3 mL/min was determined (n = 6 perfusions). Scaled placental transfer was integrated into the pregnancy physiologically based pharmacokinetic model. For darunavir 600/100 mg twice a day, the predicted fetal maximum plasma concentration, trough concentration, time to maximum plasma concentration, and half-life were 1.1, 0.57 mg/L, 3, and 21 h, respectively. This indicates that the fetal population trough concentration is higher or around the half-maximal effective darunavir concentration for a resistant virus (0.55 mg/L).

Conclusions

The results indicate that the population fetal exposure after oral maternal darunavir dosing is therapeutic and this may provide benefits to the prevention of mother-to-child transmission of human immunodeficiency virus. Moreover, this integrated approach provides a tool to prevent fetal toxicity or enhance the development of more selectively targeted fetal drug treatments.

Electronic supplementary material

The online version of this article (doi:10.1007/s40262-017-0583-8) contains supplementary material, which is available to authorized users.

An Expandable Mechanopharmaceutical Device (3): a Versatile Raman Spectral Cytometry Approach to Study the Drug Cargo Capacity of Individual Macrophages

PURPOSE

To improve cytometric phenotyping abilities and better understand cell populations with high interindividual variability, a novel Raman-based microanalysis was developed to characterize macrophages on the basis of chemical composition, specifically to measure and characterize intracellular drug distribution and phase separation in relation to endogenous cellular biomolecules.

METHODS

The microanalysis was developed for the commercially-available WiTec alpha300R confocal Raman microscope. Alveolar macrophages were isolated and incubated in the presence of pharmaceutical compounds nilotinib, chloroquine, or etravirine. A Raman data processing algorithm was specifically developed to acquire the Raman signals emitted from single-cells and calculate the signal contributions from each of the major molecular components present in cell samples.

RESULTS

Our methodology enabled analysis of the most abundant biochemicals present in typical eukaryotic cells and clearly identified "foamy" lipid-laden macrophages throughout cell populations, indicating feasibility for cellular lipid content analysis in the context of different diseases. Single-cell imaging revealed differences in intracellular distribution behavior for each drug; nilotinib underwent phase separation and self-aggregation while chloroquine and etravirine accumulated primarily via lipid partitioning.

CONCLUSIONS

This methodology establishes a versatile cytometric analysis of drug cargo loading in macrophages requiring small numbers of cells with foreseeable applications in toxicology, disease pathology, and drug discovery.

Physiologically Based Modelling of Darunavir/Ritonavir Pharmacokinetics During Pregnancy

Pregnant women are usually excluded from clinical trials. Physiologically based pharmacokinetic (PBPK) modelling may provide a method to predict pharmacokinetics in pregnant women, without the need to perform extensive in vivo clinical trials. Here, we used mechanistic modelling to delineate the potential impact of drug transporters on darunavir pharmacokinetics and to identify current knowledge gaps that limit accurate PBPK modelling of darunavir/ritonavir (darunavir/r) exposure in pregnancy. Simcyp (version 13.2) was used for PBPK modelling, using physicochemical and in vitro pharmacokinetic parameters of darunavir and ritonavir from the literature. The Michaelis-Menten constant (K m) and the maximum rate of metabolite formation (V max) for cytochrome P450 3A4-mediated darunavir biotransformation and inhibition by ritonavir were determined experimentally, while the contributions of hepatocyte influx and efflux transporters were assessed by sensitivity analysis. The simulations were compared with previously published clinical pharmacokinetic data. We found that use of a well-stirred liver model overestimated darunavir exposure substantially. A permeability-limited liver model, including hepatic uptake and efflux transporters and an efficient enterohepatic circulation step, resulted in an acceptable description of darunavir/r exposure. For the 600/100 mg darunavir/r twice-daily dose and the 800/100 mg once-daily dose, the estimated pharmacokinetic parameters were within a 2-fold range of the reported data. The predicted decreases in the area under the concentration-time curve (AUC) values during pregnancy for the twice- and once-daily doses were 27 and 41%, respectively, which were in line with the observed decreases of 17-22 and 33%. In conclusion, our data support a clinically relevant role of hepatic transporters in darunavir pharmacokinetics. By including them in our model, we successfully approximated the increase in darunavir exposure mediated by ritonavir co-administration and the decrease in darunavir exposure observed during pregnancy.

Quantification of darunavir and etravirine in human peripheral blood mononuclear cells using high performance liquid chromatography tandem mass spectrometry (LC-MS/MS), clinical application in a cohort of 110 HIV-1 infected patients and evidence of a potential drug-drug interaction

OBJECTIVES

To describe the validation of a sensitive high performance liquid chromatography tandem mass spectrometry (LC-MS/MS) method allowing the simultaneous quantification of darunavir (DRV) and etravirine (ETR) in peripheral blood mononuclear cells (PBMCs) and its application in a cohort of HIV-1 infected patients.

METHODS

Blood samples were obtained from 110 patients. PMBCs were isolated using density gradient centrifugation. Drug extraction from PBMCs was performed with a 60:40 methanol-water (MeOH-H2O) solution containing deuterated IS (DRV-d9 and ETR-d8). The chromatographic separation was performed on a RP18 XBridge™ column.

RESULTS

The geometric mean (GM) of cell associated concentration ([DRV]CC) and plasmatic concentration ([DRV]plasma) were 360.5ng/mL (CI95%:294.5-441.2) and 1733ng/mL (CI95%:1486-2021), respectively. A geometric mean intracellular (IC)/plasma ratio (GMR) of 0.21 (CI95%:0.18-0.24) was calculated. Adjusted for dose/body surface area and post-intake time, a statistically significant correlation was observed between [DRV]Plasma and the eGFR (p=0.002) and between [DRV]Plasma and the concomitant use of ETR (p=0.038). For the 10 patients receiving ETR in addition to DRV, the GM of [ETR]Plasma (available for 8 out of 10 patients) and [ETR]CC were 492.3ng/mL and 2951ng/mL respectively. The GMR of ETR was 7.6 (CI95%: 3.61-13.83).

CONCLUSIONS

A handy and sensitive high performance LC-MS/MS method allowing the simultaneous quantification of DRV and ETR in PBMCs has been described and successfully applied in the largest cohort of DRV-treated patients reported to date. ETR accumulates more efficiently in PBMCs compared to DRV. We have also highlighted a possible impact of ETR on DRV plasma concentrations requiring further investigations.

Drug transporters in tissues and cells relevant to sexual transmission of HIV: Implications for drug delivery

Efflux and uptake transporters of drugs are key regulators of the pharmacokinetics of many antiretroviral drugs. A growing body of literature has revealed the expression and functionality of multiple transporters in female genital tract (FGT), colorectal tissue, and immune cells. Drug transporters could play a significant role in the efficacy of preventative strategies for HIV-1 acquisition. Pre-exposure prophylaxis (PrEP) is a promising strategy, which utilizes topically (vaginally or rectally), orally or other systemically administered antiretroviral drugs to prevent the sexual transmission of HIV to receptive partners. The drug concentration in the receptive mucosal tissues and target immune cells for HIV is critical for PrEP effectiveness. Hence, there is an emerging interest in utilizing transporter information to explain tissue disposition patterns of PrEP drugs, to interpret inter-individual variability in PrEP drug pharmacokinetics and effectiveness, and to improve tissue drug exposure through modulation of the cervicovaginal, colorectal, or immune cell transporters. In this review, the existing literature on transporter expression, functionality and regulation in the transmission-related tissues and cells is summarized. In addition, the relevance of transporter function for drug delivery and strategies that could exploit transporters for increased drug concentration at target locales is discussed. The overall goal is to facilitate an understanding of drug transporters for PrEP optimization.

Does Once-Daily Raltegravir Have Any Role in the Antiretroviral Treatment?

Administering raltegravir once daily would make adherence to antiretroviral treatment easier, especially if the concomitant drugs are also administered once daily. We report our experience on the use of raltegravir, both once- and twice-daily.Retrospective review of HIV-infected patients on treatment with raltegravir 800 mg once or 400 mg twice a day plus 2 analogs. Patients were classified as group A (subjects switched to raltegravir due to adverse events on a previous regimen or drug-drug interactions) and group B (subjects who restarted antiretroviral treatment after a previous drop-out). The primary clinical endpoint was the percentage of subjects with virological suppression after 96 weeks. Treatment's effectiveness (noncomplete/missing equals failure) was also evaluated. Pharmacokinetic study was performed in unselected patients. Plasma raltegravir concentrations were determined by high-performance liquid chromatography coupled with mass spectrometry.A total of 133 patients were included in the study (74 and 59 on raltegravir once- and twice-daily). There were only 4 virological failures in the entire cohort during the follow-up. Thus, the Kaplan-Meier estimation of efficacy by on-treatment analysis was 96.3% (CI95, 92.8-99.8) at week 96, independently of the dosing regimen and of the raltegravir concentrations. Similar exposures to raltegravir based on AUC0-τ, but higher Cmax and significantly lower Ctrough were observed when raltegravir was given once daily compared with 400 mg twice daily. In fact, 14 out of 56 Ctrough concentrations (25%) from patients taking raltegravir once daily were below the IC95 of wild-type HIV-1 clinical isolates while only 2 samples from patients receiving 400 mg twice a day were below this value, although no relationship between Ctrough and efficacy was found. The main limitations of the study are that the raltegravir dosing regimen was not randomized and more than 50% of the patients were virologically suppressed at baseline.Regimens comprising raltegravir 800 mg once daily plus 2 nucleos(t)ide reverse transcriptase inhibitors can be an efficacious and safe option, particularly in virologically suppressed patients and those with a viral load <100,000 copies/mL.

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.

Intracellular antiviral activity of low-dose ritonavir in boosted protease inhibitor regimens

Protease inhibitors are largely used for the treatment of HIV infection in combination with other antiretroviral drugs. Their improved pharmacokinetic profiles can be achieved through the concomitant administration of low doses of ritonavir (RTV), a protease inhibitor currently used as a booster, increasing the exposure of companion drugs. Since ritonavir-boosted regimens are associated with long-term adverse events, cobicistat, a CYP3A4 inhibitor without antiviral activity, has been developed. Recently, high intracellular concentrations of ritonavir in lymphocytes and monocytes were reported even when ritonavir was administered at low doses, so we aimed to compare its theoretical antiviral activity with those of the associated protease inhibitors. Intracellular concentrations of ritonavir and different protease inhibitors were determined through the same method. Inhibitory constants were obtained from the literature. The study enrolled 103 patients receiving different boosted protease inhibitors, darunavir-ritonavir 600 and 100 mg twice daily and 800 and 100 mg once daily (n = 22 and 4, respectively), atazanavir-ritonavir 300 and 100 mg once daily (n = 40), lopinavir-ritonavir 400 and 100 mg twice daily (n = 21), or tipranavir-ritonavir 500 and 200 mg twice daily (n = 16). According to the observed concentrations, we calculated the ratios between the intracellular concentrations of ritonavir and those of the companion protease inhibitor and between the theoretical viral protease reaction speeds with each drug, with and without ritonavir. The median ratios were 4.04 and 0.63 for darunavir-ritonavir twice daily, 2.49 and 0.74 for darunavir-ritonavir once daily, 0.42 and 0.74 for atazanavir-ritonavir, 0.57 and 0.95 for lopinavir-ritonavir, and 0.19 and 0.84 for tipranavir-ritonavir, respectively. Therefore, the antiviral effect of ritonavir was less than that of the concomitant protease inhibitors but, importantly, mostly with darunavir. Thus, further in vitro and in vivo studies of the RTV antiviral effect are warranted.

Pharmacokinetics of darunavir in fixed-dose combination with cobicistat compared with coadministration of darunavir and ritonavir as single agents in healthy volunteers

This study compared the bioavailability of two candidate fixed-dose combinations (FDCs: G003 and G004) of darunavir/cobicistat 800/150 mg with that of darunavir 800 mg and ritonavir 100 mg coadministered as single agents. Short-term safety and tolerability of the FDC formulations were also assessed. This open-label trial included 36 healthy volunteers and assessed steady-state pharmacokinetics of darunavir over 3 randomized, 10-day treatment sequences, under fed conditions. Blood samples for determination of plasma concentrations of darunavir and cobicistat or ritonavir were taken over 24 hours on day 10 and analyzed by liquid-chromatography tandem mass-spectroscopy. Darunavir AUC24h following administration of the FDCs (G003: 74,780 ng ∙ h/mL and G004: 76,490 ng ∙ h/mL) was comparable to that following darunavir/ritonavir (78,410 ng ∙ h/mL), as was Cmax (6,666 and 6,917 ng/mL versus 6,973 ng/mL, respectively). Modestly lower C0h (1,504 and 1,478 ng/mL versus 2,015 ng/mL) and Cmin (1,167 and 1,224 ng/mL versus 1,540 ng/mL) values were seen with the FDCs. Short-term tolerability of the FDCs was comparable to that of darunavir/ritonavir when administered as single agents. The most common adverse events reported were headache, gastrointestinal upset, or rash. Cobicistat is an effective pharmacoenhancer of darunavir when administered as an FDC. Short-term administration of darunavir/ritonavir or darunavir/cobicistat was generally well tolerated.

Measurement of plasma and intracellular concentrations of raltegravir in patients with HIV infection

Paired plasma and intracellular samples were obtained from 12 HIV-infected adults taking raltegravir twice daily (b.i.d.), and after switching to once daily. With b.i.d. dosing, no plasma trough concentrations were below the IC95, in contrast to 33% for once daily dosing. Fifty percent of the once daily group had intracellular trough concentrations below the inhibitory concentration 95 (IC95), 25% in the b.i.d. group. Lower plasma and intracellular concentrations may contribute to inferior virologic suppression rates observed with once daily raltegravir dosing.

A novel ultrasensitive LC-MS/MS assay for quantification of intracellular raltegravir in human cell extracts

An assay using ultrahigh pressure liquid chromatography and mass spectrometry detection was developed and validated for measurement of the HIV integrase inhibitor raltegravir (MK-0518) in human cell extracts. The assay is designed to utilize 200 μl of 70% MeOH cell extract derived from human peripheral blood mononuclear cells or human tissue samples. The assay is linear over a range from 0.0023 to 9.2 ng ml(-1). The average %CV (SD/Mean)*100 and %deviation ((observed-target)/target)*100 were less than 20% at the lower limit of quantification and less than 15% over the range of the curve. This assay is an accurate and highly sensitive method for determining raltegravir concentrations in cellular extracts with a lower limit 40 to over 100-fold lower than other methods in the literature. We also present a new processing method where a rapid spin through oil produced a significant increase in apparent intracellular raltegravir concentration compared with conventional processing.

Intracellular and plasma pharmacokinetics of 400 mg of etravirine once daily versus 200 mg of etravirine twice daily in HIV-infected patients

OBJECTIVES

To compare intracellular and plasma etravirine concentrations when etravirine was given at 200 mg/12 h versus 400 mg/24 h and to evaluate whether the results would support once-daily dosing.

METHODS

This was an open-label sequential study in which eight patients on protease inhibitor (PI)-sparing regimens containing etravirine were included. Full pharmacokinetic profiles were performed while on 200 mg of etravirine/12 h and after switching to 400 mg of etravirine/24 h. Intracellular and plasma levels were determined by liquid chromatography coupled with mass spectrometry. Pharmacokinetic parameters were calculated by non-compartmental analysis and compared by geometric mean ratios (GMRs) using 200 mg of etravirine/12 h as the reference group.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01121809.

RESULTS

The geometric mean (GM) for etravirine AUC(0-τ) (5602 versus 5076 ng · h/mL, GMR 0.91), C(max) (403 versus 495 ng/mL, GMR 1.23) and C(min) (139 versus 102 ng/mL, GMR 0.74) were similar with both dosing schedules at the intracellular level. In plasma, the GMRs for AUC(0-τ), C(max) and C(min) were 1.31, 1.76 and 0.99, respectively. The mean intracellular penetration, evaluated as intracellular and plasma AUC(0-τ) ratios, was 81% when etravirine was dosed twice daily and 56% with once-daily dosing.

CONCLUSIONS

Our results show that intracellular etravirine levels were similar with both dosing regimens in patients with PI-sparing regimens, while etravirine plasma AUC(0-τ) and C(max) were 30% and 76% higher with the once-daily regimen, respectively. Thus, a once-daily dosing regimen is supported not only by plasma etravirine pharmacokinetic profiles but also by intracellular levels.

Plasma and intracellular pharmacokinetics of darunavir/ritonavir once daily and raltegravir once and twice daily in HIV-infected individuals

OBJECTIVES

To investigate the pharmacokinetics of darunavir/ritonavir and raltegravir, in HIV-infected subjects, in both plasma and at the intracellular (IC) site of action.

METHODS

HIV-infected patients on antiretroviral therapy received raltegravir 400 mg twice daily for 21 days (period 1); darunavir/ritonavir 800/100 mg once daily was added for 14 days (period 2), and patients were randomized to continue raltegravir twice daily (group 1) or to switch to 800 mg once daily (group 2), then they all stopped raltegravir intake and continued darunavir/ritonavir once daily for 14 days (period 3). Drug concentrations in plasma and cells (peripheral blood mononuclear cell) were measured, and differences in geometric mean ratios (GMR) and 90% confidence intervals (CI) between period 2 versus period 3 and period 2 versus period 1 were assessed.

RESULTS

Twenty-four patients completed the study. Group 1 GMR (90% CI) of darunavir area under the curve (AUC) with and without raltegravir was 1.24 (1.13 to 1.45) for plasma and 1.24 (1.07 to 1.73) for cells and for group 2 was 1.14 (1.07 to 1.24) and 1.03 (0.94 to 1.16). GMR (90% CI) of raltegravir AUC without and with darunavir/ritonavir (plasma and cells) for group 1 was 0.90 (0.73 to 1.44) and 1.02 (0.81 to 1.67) and for group 2 was 1.21 (1.03 to 1.77) and 1.27 (1.07 to 1.94). Geometric mean IC to plasma AUC ratios were 5.3 and 4.9 for darunavir in groups 1 and 2 when darunavir/ritonavir was given alone and 4.9 and 5.6 for raltegravir when given alone. These ratios were not altered by the coadministered drug.

CONCLUSIONS

No remarkable interactions between darunavir/ritonavir and raltegravir in plasma or cells were seen. Raltegravir IC concentrations are higher than previously reported; the difference being due to modified cell isolation procedures that reduced drug loss caused by washing.

A sensitive liquid chromatography coupled with mass spectrometry method for the intracellular and plasma quantification of raltegravir after solid-phase extraction

INTRODUCTION

Liquid chromatography coupled with mass spectrometry for the quantification of raltegravir in human plasma and peripheral blood mononuclear cells has been developed.

METHODS

Sample preparations were based on a fully automated solid-phase extraction process. Mass spectrometric data were acquired in a single-ion monitoring method. Raltegravir and quinoxaline, the internal standard, were well separated in a gradient mode over 15 min.

KEY FINDINGS

Validation study exhibited excellent linearity, with good intra- and inter-day precision and accuracy.

CONCLUSIONS

The assay was successfully applied to the raltegravir quantification in HIV-infected patients.

Efficacy of Tat-conjugated ritonavir-loaded nanoparticles in reducing HIV-1 replication in monocyte-derived macrophages and cytocompatibility with macrophages and human neurons

Human immunodeficiency virus (HIV)-1 targets mononuclear phagocytes (MP), which disseminate infection to organs such as brain, spleen and lymph. Thus MP, which include microglia, tissue macrophages and infiltrating monocyte-derived macrophages (MDM), are important target of anti-HIV-1 drug therapy. Most of the currently used antiretroviral drugs are effective in reducing viral loadin the periphery but cannot effectively eradicate infection from tissue reservoirs such as brain MP. HIV-1 infection of the central nervous system can lead to a wide variety of HIV-1-associated neurocognitive disorders. In this study, we demonstrate that ritonavir-loaded nanoparticles (RNPs) are effective in inhibiting HIV-1 infection of MDM. Reduced infection is observed in multiple read-out systems including reduction of cytopathic effects, HIV-1 p24 protein secretion and production of progeny virions. Furthermore, the RNPs retained antiretroviral efficacy after being removed from MDM cultures. As HIV-1-infected cells in the brain are likely to survive for a long period of time, both acute and chronic infection paradigms were evaluated. Tat-peptide-conjugated RNPs (Tat-RNP) were effective in both short-term and long-term HIV-1-infected MDM. Importantly, we confirm that delivery of RNPs, both with and without Tat-peptide conjugation, is toxic neither to MDM nor to neural cells, which may be bystander targets of the nanoformulations. In conclusion, Tat-NPs could be a safe and effective way of delivering anti-HIV-1 drugs for controlling viral replication occurring within brain MP.

Pharmacokinetic modeling of plasma and intracellular concentrations of raltegravir in healthy volunteers

Raltegravir is a potent inhibitor of HIV integrase. Persistently high intracellular concentrations of raltegravir may explain sustained efficacy despite high pharmacokinetic variability. We performed a pharmacokinetic study of healthy volunteers. Paired blood samples for plasma and peripheral blood mononuclear cells (PBMCs) were collected predose and 4, 8, 12, 24, and 48 h after a single 400-mg dose of raltegravir. Samples of plasma only were collected more frequently. Raltegravir concentrations were determined using liquid chromatography-mass spectrometry. The lower limits of quantitation for plasma and PBMC lysate raltegravir were 2 nmol/liter and 0.225 nmol/liter, respectively. Noncompartmental analyses were performed using WinNonLin. Population pharmacokinetic analysis was performed using NONMEM. Six male subjects were included in the study; their median weight was 67.4 kg, and their median age was 33.5 years. The geometric mean (GM) (95% confidence interval shown in parentheses) maximum concentration of drug (C(max)), area under the concentration-time curve from 0 to 12 h (AUC(0-12)), and area under the concentration-time curve from 0 h to infinity (AUC(0-∞)) for raltegravir in plasma were 2,246 (1,175 to 4,294) nM, 10,776 (5,770 to 20,126) nM · h, and 13,119 (7,235 to 23,788) nM · h, respectively. The apparent plasma raltegravir half-life was 7.8 (5.5 to 11.3) h. GM intracellular raltegravir C(max), AUC(0-12), and AUC(0-∞) were 383 (114 to 1,281) nM, 2,073 (683 to 6,290) nM · h, and 2,435 (808 to 7,337) nM · h (95% confidence interval shown in parentheses). The apparent intracellular raltegravir half-life was 4.5 (3.3 to 6.0) h. Intracellular/plasma ratios were stable for each patient without significant time-related trends over 48 h. Population pharmacokinetic modeling yielded an intracellular-to-plasma partitioning ratio of 11.2% with a relative standard error of 35%. The results suggest that there is no intracellular accumulation or persistence of raltegravir in PBMCs.

Clinical evaluation of the determination of plasma concentrations of darunavir, etravirine, raltegravir and ritonavir in dried blood spot samples

Background: Measurement of drug levels in plasma is currently the gold standard for pharmacological studies. However, venous sampling is not feasible in some populations (e.g., neonates) or may be difficult in certain situations, such as nonhospital-based settings. Dried blood spots (DBS) can be obtained by a simple fingerprick and the subsequent collection of blood on a filter card, allowing patient-friendly sample collection in non-hospital-based settings. Despite these advantages, thus far no clinical evaluation has been performed for the use of DBS concentrations as surrogates for plasma levels. Our purpose was to clinically evaluate DBS sampling for the determination of plasma concentrations for the novel antiretroviral drugs etravirine, darunavir/ritonavir and raltegravir. Results: DBS concentrations were measured in 11 HIV-infected patients using LC–MS/MS. DBS concentrations were proportional to plasma concentrations. All drug concentrations were higher in DBS than in plasma samples. The plasma:DBS ratio and the respective relative standard error of estimate (RSE) of darunavir, etravirine, raltegravir and ritonavir were 0.632 (4.97% RSE), 0.523 (4.84% RSE), 0.617 (14.9% RSE) and 0.592 (2.99% RSE), respectively. Hematocrit did not explain variability in our study. Conclusions: DBS are reproducibly correlated to plasma levels and can be used for monitoring antiretroviral drug exposure in HIV-infected patients.

Cell disposition of raltegravir and newer antiretrovirals in HIV-infected patients: high inter-individual variability in raltegravir cellular penetration

OBJECTIVES

The site of pharmacological activity of raltegravir is intracellular. Our aim was to determine the extent of raltegravir cellular penetration and whether raltegravir total plasma concentration (C(tot)) predicts cellular concentration (C(cell)).

METHODS

Open-label, prospective, pharmacokinetic study on HIV-infected patients on a stable raltegravir-containing regimen. Plasma and peripheral blood mononuclear cells were simultaneously collected during a 12 h dosing interval after drug intake. C(tot) and C(cell) of raltegravir, darunavir, etravirine, maraviroc and ritonavir were measured by liquid chromatography coupled to tandem mass spectrometry after protein precipitation. Longitudinal mixed effects analysis was applied to the C(cell)/C(tot) ratio.

RESULTS

Ten HIV-infected patients were included. The geometric mean (GM) raltegravir total plasma maximum concentration (C(max)), minimum concentration (C(min)) and area under the time-concentration curve from 0-12 h (AUC(0-12)) were 1068 ng/mL, 51.1 ng/mL and 4171 ng·h/mL, respectively. GM raltegravir cellular C(max), C(min) and AUC(0-12) were 27.5 ng/mL, 2.9 ng/mL and 165 ng·h/mL, respectively. Raltegravir C(cell) corresponded to 5.3% of C(tot) measured simultaneously. Both concentrations fluctuate in parallel, with C(cell)/C(tot) ratios remaining fairly constant for each patient without a significant time-related trend over the dosing interval. The AUC(cell)/AUC(tot) GM ratios for raltegravir, darunavir and etravirine were 0.039, 0.14 and 1.55, respectively.

CONCLUSIONS

Raltegravir C(cell) correlated with C(tot) (r = 0.86). Raltegravir penetration into cells is low overall (∼5% of plasma levels), with distinct raltegravir cellular penetration varying by as much as 15-fold between patients. The importance of this finding in the context of development of resistance to integrase inhibitors needs to be further investigated.

Inhibition of Feline leukemia virus replication by the integrase inhibitor Raltegravir

The oncogenic gammaretrovirus Feline leukemia virus (FeLV) has been the leading cause of death among domestic cats until the introduction of efficient diagnostics and vaccines in the late 1980s. So far, no efficient treatment for viremic animals is available. Hence, use of the FeLV model to evaluate antiretroviral therapies applied to HIV is a timely task. The efficacy of the integrase inhibitor Raltegravir, which is widely used for the treatment of HIV in humans, has been assessed in vitro for the FeLV-A/Glasgow-1 strain. EC(50) values for FeLV-A inhibition in feline cell lines are in the range of that observed for HIV and xenotropic murine leukemia virus-related gammaretrovirus. Therefore, Raltegravir may be a potential therapeutical agent for felids with progressive FeLV infection.

Evaluation of the mean corpuscular volume of peripheral blood mononuclear cells of HIV patients by a coulter counter to determine intracellular drug concentrations

The mean corpuscular volume (MCV) of peripheral blood mononuclear cells (PBMCs) was determined by Coulter Counter, and data were used to calculate the intracellular drug concentrations. A total of 574 PBMC samples were collected from 190 patients. The MCV was 282.9 fl (minimum, 207.0; maximum, 354.6), with a standard deviation of 8.8%. Previous reports have often used a fixed value of 400 fl for the MCV, which may result in artificially low estimates of the intracellular concentrations of antivirals.

Clinical pharmacology profile of raltegravir, an HIV-1 integrase strand transfer inhibitor

Raltegravir is an HIV-1 integrase inhibitor approved to treat HIV infection in adults in combination with other antiretrovirals. Data from healthy volunteers demonstrate that raltegravir is rapidly absorbed with a mean half-life of approximately 7 to 12 hours, with steady state achieved in approximately 2 days. Raltegravir is characterized by both high intra- and interindividual variabilities, although neither gender, race, age, body mass index, food intake, nor renal or hepatic insufficiency has a clinically meaningful effect on raltegravir pharmacokinetics. Raltegravir lacks activity as a perpetrator of drug-drug interactions and demonstrates a low propensity to be subject to drug-drug interactions. Raltegravir is metabolized primarily by UGT1A1 and is not affected by P450 inhibitors or inducers. Inhibitors of UGT1A1 (eg, atazanavir) can increase plasma concentrations of raltegravir, although this increase has not been found to be clinically meaningful. Likewise, inducers of UGT1A1 (eg, rifampin) can reduce plasma concentrations of raltegravir, and the clinical significance of this reduction is being investigated in ongoing clinical studies. Raltegravir demonstrates favorable clinical pharmacology and a drug interaction profile that permits administration to a wide, demographically diverse patient population and coadministration with many other therapeutic agents, including antiretroviral agents and supportive medications, without restrictions or dose adjustment.

Plasma and intracellular (peripheral blood mononuclear cells) pharmacokinetics of once-daily raltegravir (800 milligrams) in HIV-infected patients

The aim of this study was to evaluate the plasma and intracellular pharmacokinetics of raltegravir in HIV-infected patients receiving once-daily raltegravir. Five HIV-infected patients on stable therapy with lopinavir-ritonavir monotherapy whose HIV-1 RNA load was <50 copies/ml were included in this open-label, pilot study. Raltegravir was added to the antiretroviral regimen at a dose of 800 mg once daily from days 0 to 10. On day 10, a full pharmacokinetic profile was obtained for each participant. Raltegravir concentrations in plasma and peripheral blood mononuclear cells (PBMCs) were determined by high-performance liquid chromatography with a fluorescence detector and by liquid chromatography-tandem mass spectrometry (LC-MS/MS), respectively. The values of the raltegravir pharmacokinetic parameters in plasma and PBMCs were calculated by noncompartmental analysis. Raltegravir was well tolerated, and all participants completed the study. No differences in the times to the maximum concentration of raltegravir in plasma or the raltegravir half-lives were observed between plasma and PBMCs. The geometric mean raltegravir maximum concentration, the concentration at the end of the dosing interval, and the area under the concentration-time curve during the dose interval in plasma versus PBMCs were 2,640 ng/ml (range, 887 to 10,605 ng/ml) versus 199 ng/ml (range, 82 to 857 ng/ml) (geometric mean ratio [GMR], 13.30; 95% confidence interval [CI], 3.11 to 56.89; P = 0.003); 89 ng/ml (range, 51 to 200 ng/ml) versus 7 ng/ml (range, 2 to 15 ng/ml) (GMR, 13.21; 95% CI, 3.94 to 44.26; P = 0.001); and 12,200 ng·h/ml (range, 5,152 to 30,130 ng·h/ml) versus 909 ng·h/ml (range, 499 to 2,189 ng·h/ml) (GMR, 13.43; 95% CI, 5.13 to 35.16; P < 0.001), respectively. Raltegravir does not accumulate in PBMCs, with intracellular concentrations being about 1/10 of the concentrations in plasma. Despite once-daily dosing, mean raltegravir concentrations at the end of the dosing interval in plasma and PBMCs exceeded the reported protein-binding-adjusted 95% inhibitory concentration (IC(95)) and IC(50) for wild-type viral strains, respectively.