Brief Report: Pharmacokinetics of Bictegravir and Tenofovir in Combination With Darunavir/Cobicistat in Treatment-Experienced Persons With HIV.

BACKGROUND: Bictegravir coformulated with emtricitabine and tenofovir alafenamide as a fixed-dose combination (BIC/FTC/TAF 50/200/25 mg) is recommended as an initial regimen in patients who are antiretroviral (ARV)-naïve or virologically suppressed on a stable ARV regimen. However, no real-world pharmacokinetic (PK) data are available in treatment-experienced patients with antiretroviral resistance receiving BIC/FTC/TAF plus a boosted protease inhibitor. SETTING/METHODS: This prospective, single-center, nonrandomized pharmacokinetic study enrolled adult treatment-experienced persons with HIV and creatinine clearance >30 mL/min receiving BIC/FTC/TAF + DRV/c as part of routine clinical care. Steady-state PK profiles of BIC, TAF, tenofovir (TFV), and DRV after daily dosing of BIC/FTC/TAF + darunavir/cobicistat (DRV/c) were obtained with samples at predose and 0.5, 1, 2, and 4 hours postdose. The AUC0-24 at steady state was extrapolated by imputing C0 for C24 for each participant (AUC0-tau,exp). RESULTS: Nine participants were enrolled with a median age of 59 years (range 54-67) and median number of years on ART of 19 (range 5.8-30). The median (interquartile range [IQR]) BIC AUC0-tau,exp and Cmax values were 128.9 µg*h/mL (78.1-159.5) and 6.9 µg/mL (5.1-9.8), respectively. The median (IQR) TAF AUC0-tau,exp and Cmax values were 0.376 µg*h/mL (0.199-0.430) and 0.276 µg/mL (0.149-0.543), respectively. Predose concentrations of TFV and DRV were comparable with historical data. CONCLUSION: Treatment-experienced persons with HIV receiving BIC/FTC/TAF + darunavir/cobicistat (DRV/c) had BIC exposures (AUC0-tau) that were increased by approximately 26% compared with historical PK data. Although TAF exposures were substantially increased, plasma TFV was only modestly higher. These results suggest that BIC/TAF/FTC + DRV/c is a viable antiviral regimen option for treatment-experienced persons.

Higher plasma drug levels in elderly people living with HIV treated with darunavir.

BACKGROUND: The proportion of elderly people living with HIV-1 (PLHIV) is rising. In older patients, comorbidities and concomitant medications are more frequent, increasing the risk of potential drug-drug interactions (PDDIs). Data on the pharmacokinetics of ART in individuals aged ≥ 65 years of age are scarce. We compared plasma drug levels of ART, PDDIs, and side-effects in PLHIV aged ≥ 65 years of age, with controls ≤ 49 years of age. METHODS: Patients ≥ 65 years of age and controls ≤ 49 years of age, all of whom were on stable treatment with atazanavir (ATV), darunavir (DRV), or efavirenz (EFV) were included cross-sectionally. Plasma drug levels of ART were analyzed, comorbidities, concomitant medication, adherence, and side-effects recorded, and PDDIs analyzed using drug interactions databases. RESULTS: Between 2013 and 2015, we included 100 individuals ≥ 65 years of age (study group) and 99 controls (≤ 49 years of age). Steady-state DRV concentrations were significantly higher in the study group than in the control group (p = 0.047). In the ATV group there was a trend towards a significant difference (p = 0.056). No significant differences were found in the EFV arm. The DRV arm had a higher frequency of reported side-effects than the ATV and EFV arms in the study group (36.7% vs. 0% and 23.8% respectively (p = 0.014), with significant differences between DRV vs. ATV, and EFV vs. ATV). CONCLUSIONS: Higher steady-state plasma levels of DRV and ATV (but not EFV) were found in PLHIV aged ≥ 65 years of age, compared to controls ≤ 49 years of age.

Safety of hydroxychloroquine and darunavir or lopinavir in COVID-19 infection.

BACKGROUND: Combination therapy with hydroxychloroquine and darunavir/ritonavir or lopinavir/ritonavir has been suggested as an approach to improve the outcome of patients with moderate/severe COVID-19 infection. OBJECTIVES: To examine the safety of combination therapy with hydroxychloroquine and darunavir/ritonavir or lopinavir/ritonavir. METHODS: This was an observational cohort study of patients hospitalized for COVID-19 pneumonia treated with hydroxychloroquine and darunavir/ritonavir or lopinavir/ritonavir. Clinical evaluations, electrocardiograms and the pharmacokinetics of hydroxychloroquine, darunavir and lopinavir were examined according to clinical practice and guidelines. RESULTS: Twenty-one patients received hydroxychloroquine with lopinavir/ritonavir (median age 68 years; 10 males) and 25 received hydroxychloroquine with darunavir/ritonavir (median age 71 years; 15 males). During treatment, eight patients (17.4%) developed ECG abnormalities. Ten patients discontinued treatment, including seven for ECG abnormalities a median of 5 (range 2-6) days after starting treatment. All ECG abnormalities reversed 1-2 days after interrupting treatment. Four patients died within 14 days. ECG abnormalities were significantly associated with age over 70 years, coexisting conditions (such as hypertension, chronic cardiovascular disease and kidney failure) and initial potential drug interactions, but not with the hydroxychloroquine concentration. CONCLUSIONS: Of the patients with COVID-19 who received hydroxychloroquine with lopinavir or darunavir, 17% had ECG abnormalities, mainly related to age or in those with a history of cardiovascular disease.

Optimal sampling strategies for darunavir and external validation of the underlying population pharmacokinetic model.

PURPOSE: A variety of diagnostic methods are available to validate the performance of population pharmacokinetic models. Internal validation, which applies these methods to the model building dataset and to additional data generated through Monte Carlo simulations, is often sufficient, but external validation, which requires a new dataset, is considered a more rigorous approach, especially if the model is to be used for predictive purposes. Our first objective was to validate a previously published population pharmacokinetic model of darunavir, an HIV protease inhibitor boosted with ritonavir or cobicistat. Our second objective was to use this model to derive optimal sampling strategies that maximize the amount of information collected with as few pharmacokinetic samples as possible. METHODS: A validation dataset comprising 164 sparsely sampled individuals using ritonavir-boosted darunavir was used for validation. Standard plots of predictions and residuals, NPDE, visual predictive check, and bootstrapping were applied to both the validation set and the combined learning/validation set in NONMEM to assess model performance. D-optimal designs for darunavir were then calculated in PopED and further evaluated in NONMEM through simulations. RESULTS: External validation confirmed model robustness and accuracy in most scenarios but also highlighted several limitations. The best one-, two-, and three-point sampling strategies were determined to be pre-dose (0 h); 0 and 4 h; and 1, 4, and 19 h, respectively. A combination of samples at 0, 1, and 4 h was comparable to the optimal three-point strategy. These could be used to reliably estimate individual pharmacokinetic parameters, although with fewer samples, precision decreased and the number of outliers increased significantly. CONCLUSIONS: Optimal sampling strategies derived from this model could be used in clinical practice to enhance therapeutic drug monitoring or to conduct additional pharmacokinetic studies.

Low plasmatic concentration of intensified antiretroviral therapy in a pregnant woman: a case report.

BACKGROUND: Identifying the most appropriate antiretroviral regimen for pregnant women with Human Immunodeficiency Virus (HIV-1) infection can be challenging, mainly due to pregnancy-related physiological alterations which can significantly reduce maternal drug plasma concentration. We would like to report our experience as it consists of an unusual case of low plasmatic concentration of antiretroviral drugs despite regimen intensification in a HIV-positive pregnant woman. It also underlines the need for accurate monitoring and treatment adjustment in pregnant women with Human Immunodeficiency Virus (HIV). CASE PRESENTATION: A 26-year-old Brazilian woman with HIV-1 infection attending our out-patient clinic presented with low plasmatic concentration of antiretroviral drugs and persistent detectable viral load despite regimen intensification during pregnancy. Trough plasma concentrations of dolutegravir and darunavir were measured by validated liquid chromatography-mass spectrometry. At 23 weeks of gestation it showed a lower value than expected in non-pregnant adults, compared to a normal level of plasma concentration measured at 10 weeks after delivery. Our patient and the baby had no regimen-related adverse effects. CONCLUSIONS: Physiological changes during pregnancy can affect pharmacokinetics and reduce a mother's bioavailability of antiretroviral drugs, potentially altering their pharmacological activity. A personalized treatment and a careful follow-up are hence mandatory for this key population.

Pharmacokinetic modelling of darunavir/ritonavir dose reduction (800/100 to 400/100 mg once daily) in a darunavir/ritonavir-containing regimen in virologically suppressed HIV-infected patients: ANRS 165 DARULIGHT sub-study.

Background: In the ANRS 165 DARULIGHT study (NCT02384967) carried out in HIV-infected patients, the use of a darunavir/ritonavir-containing regimen with a switch to a reduced dose of darunavir maintained virological efficacy (≤50 copies/mL) for 48 weeks with a good safety profile. Objectives: To assess the total and unbound blood plasma pharmacokinetics of darunavir and associated antiretrovirals, and their penetration into semen before and after dose reduction. Patients and methods: Patients receiving a darunavir/ritonavir (800/100 mg q24h)-containing regimen for >6 months with plasma HIV-RNA ≤50 copies/mL for >12 months were switched to 400/100 mg darunavir/ritonavir q24h at week 0. A 24 h intensive pharmacokinetic blood sampling and a trough seminal sampling were performed before (week 0) and after (week 12) dose reduction. Individual pharmacokinetic parameter estimates were obtained using non-linear mixed-effect modelling for darunavir/ritonavir in blood plasma and used to test for bioequivalence, whereas darunavir/ritonavir in seminal plasma and NRTIs were analysed using a non-compartmental approach. Results and conclusions: Fifteen patients completed the intensive pharmacokinetic analysis. There was no significant decrease in total and unbound darunavir blood plasma exposure despite a 50% decrease in darunavir daily dose from 800 to 400 mg (AUC0-24 = 65 563 versus 52 518 ng·h/mL; P = 0.25). A decrease in apparent oral clearance (CL/F) of both darunavir and ritonavir at week 12 suggests a modification of the initial darunavir/ritonavir daily dose balance (800/100 to 400/100 mg), in favour of a reduced inducer effect of darunavir on cytochrome P450 and efflux transporters compared with the standard dose.

Darunavir concentration in PBMCs may be a better indicator of drug exposure in HIV patients.

PURPOSE: The clinical efficacies of some antiretroviral drugs are known to not depend on its concentration in blood. To establish a method of dosage adjustment for darunavir (DRV) based on pharmacokinetic theory, we analyzed the correlation between DRV levels in peripheral blood mononuclear cells (PBMCs) and plasma. METHODS: The concentrations of DRV and ritonavir (RTV) in plasma and PBMCs of 31 samples obtained from 19 patients were analyzed. An in vitro kinetic study using MOLT-4 cells was performed to assess the contribution of RTV to the intracellular accumulation of DRV. RESULTS: DRV levels in PBMCs varied between 7.91 and 29.36 ng/106 cells (CV 37.5%), while those in plasma were greater. No significant correlation was found between the trough level of DRV in plasma and that in PBMCs (p = 0.575). The inter-day difference in DRV levels in PBMCs seemed smaller than that in plasma (- 41.6-23.0% vs - 83.3-109.1%). In the in vitro study, the elimination half-life of cellular efflux of DRV was 15.7 h in the absence of RTV and extended to 47.6 h in the presence of RTV. CONCLUSIONS: We found a poor correlation between intracellular DRV and plasma DRV levels in patients receiving highly active antiretroviral therapy. The efflux rate of DRV from cells was slow; therefore, the concentration of DRV in PBMCs may reflect average exposure to the drug and clinical efficacy.

HPLC Estimation, Ex vivo Everted Sac Permeability and In Vivo Pharmacokinetic Studies of Darunavir.

Darunavir ethanolate (DRV) is an efficient protease inhibitor (PI) used in the treatment of human immunodeficiency virus (HIV) type-1 patients. An isocratic reversed-phase HPLC method was developed to monitor concentration of darunavir in in vitro intestinal fluid samples in everted sac absorption model in the presence of bioenhancers, viz., piperine, quercetin, naringenin. The method was validated and successfully applied to everted sac and pharmacokinetic studies in rats. The absorption profiles of DRV and apparent permeability coefficients were determined. The proposed method was found to be simple, rapid, robust and selective and was applied for continuous ex vivo monitoring of DRV in everted sac absorption studies. Of the three bioenhancers screened at different concentrations, piperine caused highest and significant 1.5-fold increase in apparent permeability of DRV across everted sac tissue. Further, co-administration of piperine significantly increased the maximum plasma concentration of DRV by 1.18-fold confirming the enhancement in its absorption.

Drug-Drug Interactions Between PA-824 and Darunavir Based on Pharmacokinetics in Rats by LC-MS-MS.

Currently, patients with co-infection with HIV and tuberculosis are treated with more than one drug. PA-824 a new chemical entity and a member of a class of compounds known as nitroimidazo-oxazines, has significant antituberculosis activity and a unique mechanism of action. Darunavir (PrezistaTM) is a new protease inhibitor of HIV-1. A simple, sensitive and rapid LC-MS-MS method has been developed and validated for simultaneous determination of PA-824 and darunavir. Chromatographic separation was achieved on Agilent Eclipse plus C18 column (100 mm × 2.1 mm, 3.5 µm) using gradient elution of acetonitrile-water (90:10, v/v) with fast gradient elution at a flow rate of 0.6 mL/min and run time of 4.5 min. The mass spectrometer was run in positive electrospray ionization mode using multiple reaction monitoring to monitor the mass transitions. The method was validated for accuracy, precision, linearity, range, selectivity, lower limit of quantification, recovery and matrix effect. All validation parameters met the acceptance criteria according to regulatory guidelines. The method had been successfully applied to a pharmacokinetic study of fixed dose administration of PA-824, darunavir and their combination in rats. The results indicated that when co-administration of darunavir could decrease the amount of PA-824 in vivo and extend the elimination half-life.

Pharmacokinetics and pharmacodynamics of the nucleoside sparing dual regimen containing rilpivirine plus darunavir/ritonavir in treatment-naïve HIV-1-infected individuals.

BACKGROUND: We aimed at investigating the antiviral activity and the pharmacokinetics of the dual antiretroviral (ARV) combination of rilpivirine plus darunavir/ritonavir 25/800/100 mg once-daily in naïve HIV-1-infected individuals (NHII) with different baseline viral loads. SETTINGS: Pharmacokinetic/pharmacodynamics study in ARV-naïve HIV-infected individuals. METHODS: The primary endpoint was the number of NHII with HIV-RNA < 40 copies/mL at week 48. Secondary endpoints included rilpivirine/darunavir/ritonavir pharmacokinetics, HIV-RNA decay, and changes in ECG QT interval. RESULTS: Thirty-six individuals were enrolled, 18 with a baseline viral load < 100,000 copies/mL (group A) and 18 with a baseline viral load > 100,000 copies/mL (group B). All but 1 (HIV-RNA = 63 copies/mL) subjects achieved viral load < 50 copies/mL by week 36, and all at week 48. Median (range) HIV-RNA reduction (Log10 copies/mL) was 1.3 (0.6-1.9) over the first week, with no differences between groups A and B. Geometric mean and 95%CI rilpivirine Cmax, Ctrough, AUC were 183 (165-239), 114 (104-109) ng/mL, 2966 (2704-3820) ng h/mL. No QTcF interval changes were recorded. CONCLUSIONS: rilpivirine/darunavir/ritonavir could be efficacious, with limited short-term toxicity in ARV-naïve patients. Although rilpivirine was co-administered with ritonavir, its exposure was within ranges measured during phase III trials.

Pharmacokinetics of darunavir/cobicistat and etravirine alone and co-administered in HIV-infected patients.

Objectives: To determine the effect of etravirine on the pharmacokinetics of darunavir/cobicistat and vice versa. Safety and tolerability of this combination were also evaluated. Methods: Open-label, fixed-sequence trial in two cohorts of HIV-infected patients on therapy with darunavir/cobicistat 800/150 mg once daily (DRV cohort; n = 15) or etravirine 400 mg once daily (ETR cohort; n = 15). Etravirine or darunavir/cobicistat were added on days 1-14 and 1-7 in participants in the DRV or ETR cohort, respectively. Full pharmacokinetic profiles were obtained on days 0 and 14 in the DRV cohort, and on days 0 and 7 in the ETR cohort. Darunavir, cobicistat and etravirine pharmacokinetic parameters [AUC0-24, Cmax and trough concentrations in plasma (C24)] were calculated for each individual by non-compartmental analysis and were compared using linear mixed-effects models. Adverse events and HIV-1 RNA in plasma were monitored. Results: Etravirine co-administration decreased cobicistat AUC0-24, Cmax and C24 by 30%, 14% and 66%, respectively. Although darunavir AUC0-24 and Cmax were unchanged by etravirine, darunavir C24 was 56% lower for darunavir/cobicistat co-administered with etravirine relative to darunavir/cobicistat alone. Etravirine pharmacokinetics were unchanged by darunavir/cobicistat. Treatments were well tolerated, and HIV-1 RNA remained undetectable in all participants. Conclusions: Although etravirine pharmacokinetics was unchanged by darunavir/cobicistat, there was a significant decrease in cobicistat exposure and in darunavir C24 when darunavir/cobicistat was co-administered with etravirine. Boosting darunavir with ritonavir instead of with cobicistat may be preferred if darunavir is to be combined with etravirine in clinical practice.

Food intake and darunavir plasma concentrations in people living with HIV in an outpatient setting.

AIMS: Patients receiving darunavir are advised to take it concomitantly with food. The objectives of the present cross-sectional study were to evaluate the actual concomitant food intake of patients visiting an HIV outpatient clinic. METHODS: Sixty participants treated with darunavir/ritonavir once daily were subjected to a food recall questionnaire concerning their last concomitant food intake with darunavir. Darunavir trough concentrations were calculated. RESULTS: The median food intake was 507 (0-2707) kcal; protein intake, 20 (0-221)g; carbohydrate intake, 62 (0-267)g; fat intake: 14 (0-143)g; and dietary fibre: 4 (0-30)g. Twenty-five patients (42%) ingested their drug with between-meal snacks. No relationship was found between food intake and trough concentrations. CONCLUSIONS: Clear advice on the optimal caloric intake is needed, to avoid high caloric intake in patients who already have an increased risk of cardiovascular disease due to their HIV infection.

Physiologically Based Pharmacokinetic Modeling for Predicting the Effect of Intrinsic and Extrinsic Factors on Darunavir or Lopinavir Exposure Coadministered With Ritonavir.

Management of comorbidities and medications is complex in HIV-1-infected patients. The overall objective of this project was to develop separate physiologically based pharmacokinetic (PBPK) substrate models for the protease inhibitors darunavir and lopinavir. These protease inhibitors are used in the treatment of HIV infection. Both darunavir and lopinavir are coadministered with another medication that inhibits cytochrome (CYP) 3A. The current project focused on PBPK modeling for darunavir and lopinavir coadministered with ritonavir. Darunavir and lopinavir PBPK models that accounted for ritonavir CYP3A inhibition effects (linked PBPK models) were developed. The linked PBPK models were then used to predict the effect on darunavir or lopinavir exposure from CYP modulators. In the next step, the predicted effect of hepatic impairment was evaluated. Additional exploratory analyses predicted CYP3A inhibition effects on darunavir or lopinavir exposure in simulated hepatically impaired subjects. The linked PBPK models reasonably predicted darunavir or lopinavir exposure based on simulations with CYP inhibitors or inducers. Exploratory simulations using the linked darunavir or lopinavir PBPK models indicated CYP3A inhibition may further increase darunavir or lopinavir exposure in patients with hepatic impairment.

Darunavir concentrations in CSF of HIV-infected individuals when boosted with cobicistat versus ritonavir.

Objectives: Cobicistat and ritonavir have different inhibitory profiles for drug transporters that could impact the distribution of co-administered drugs. We compared darunavir concentrations in CSF when boosted by cobicistat versus ritonavir relative to plasma concentrations and with WT HIV-1 IC50 and IC90. Methods: An open, single-arm, sequential clinical trial (NCT02503462) where paired CSF and blood samples were taken from seven HIV-infected patients presenting with HIV-associated neurocognitive disorders (HAND) and treated with a darunavir/ritonavir (800/100 mg) once-daily regimen. Ritonavir was subsequently replaced by cobicistat and paired CSF and blood samples were obtained from the same patients after treatment with the darunavir/cobicistat (800/150 mg) once-daily regimen. Darunavir concentrations at the end of the dosing interval were quantified by LC-MS/MS. Results: The median (IQR) darunavir concentrations in CSF with ritonavir and cobicistat boosting were 16.4 ng/mL (8.6-20.3) and 15.9 ng/mL (6.7-31.6), respectively (P = 0.58). The median (IQR) darunavir CSF:plasma ratios with ritonavir and cobicistat boosting were 0.007 (0.006-0.012) and 0.011 (0.007-0.015), respectively (P = 0.16). Darunavir concentrations in CSF exceeded the darunavir IC50 and IC90 by a median of 9.2- and 6.7-fold with ritonavir boosting, and by 8.9- and 6.5-fold with cobicistat boosting, respectively. All patients had darunavir CSF concentrations above the target inhibitory concentrations and remained virologically suppressed in the CSF and plasma. Conclusions: This small study shows that cobicistat and ritonavir give comparable effective darunavir concentrations in CSF, thus suggesting that these boosters can be used interchangeably in once-daily darunavir regimens.

Plasma and saliva concentrations of abacavir, tenofovir, darunavir, and raltegravir in HIV-1-infected patients
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OBJECTIVE: We studied the relationships between plasma and saliva concentrations of antiretroviral drugs to explore whether saliva can be used for therapeutic drug monitoring (TDM). METHODS: Abacavir (ABC), tenofovir (TFV), darunavir (DRV), and raltegravir (RAL) in plasma and saliva from 30 HIV-1-infected patients were quantified using liquid chromatography-tandem mass spectrometry. RESULTS: Mean saliva-to-plasma concentration ratios were 0.623 (ABC), 0.024 (TFV), 0.065 (DRV), and 0.0135 (RAL), which agree with the plasma protein binding rates except TFV. Significant correlations were evident between saliva and plasma concentrations of ABC, DRV, and RAL. CONCLUSIONS: This study suggests that plasma concentrations of ABC, DRV, and RAL can be estimated from their saliva concentrations and that the saliva concentration of some antiretroviral drugs reflects the unbound drug concentration in plasma.
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The effect of veno-venous ECMO on the pharmacokinetics of Ritonavir, Darunavir, Tenofovir and Lamivudine.

INTRODUCTION: To our knowledge, there is no published data on the pharmacokinetic (PK) profile of antiretroviral (ART) drugs on patients undergoing extracorporeal membrane oxygenation (ECMO) therapy. We present PK analyses of Ritonavir, Darunavir, Lamivudine and Tenofovir in a patient with HIV who required veno-venous ECMO (VV ECMO). METHODS: Plasma concentrations for Ritonavir, Darunavir, Tenofovir and Lamivudine were obtained while the patient was on ECMO following pre-emptive dose adjustments. Published population PK models were used to simulate plasma concentration profiles for the drugs. The population prediction and the observed plasma concentrations were then overlaid with the expected drug profiles using the individual Bayesian post-hoc parameter estimates. RESULTS: Following dose adjustments, the PK profiles of Ritonavir, Darunavir and Tenofovir fell within the expected range and appeared similar to the population prediction, although slightly different for Ritonavir. The observed data for Lamivudine and its PK profile were completely different from the data available in the literature. CONCLUSIONS: To our knowledge, this is the first study reporting the PK profile of ART drugs during ECMO therapy. Based on our results, dose adjustment of ART drugs while on VV ECMO may be advisable. Further study of the PK profile of Lamivudine is required.

Once-daily atazanavir/cobicistat and darunavir/cobicistat exposure over 72 h post-dose in plasma, urine and saliva: contribution to drug pharmacokinetic knowledge.

Background: We investigated the pharmacokinetics (PK) of atazanavir/cobicistat and darunavir/cobicistat once daily over 72 h following drug intake cessation in plasma, saliva and urine. Methods: Healthy volunteers received a fixed-dose combination of 300/150 mg of atazanavir/cobicistat once daily for 10 days, followed by a 10 day washout period and then a fixed-dose combination of 800/150 mg of darunavir/cobicistat once daily for 10 days. Full PK profiles were assessed for each phase for 72 h following day 10 and parameters determined to the last measurable concentration in plasma, saliva and urine by non-compartmental methods. Results: Sixteen subjects completed the study. Geometric mean (GM) terminal elimination half-life values to 72 h of atazanavir and darunavir were 6.77 and 6.35 h, respectively. All subjects had atazanavir concentrations above the suggested minimum effective concentration of 150 ng/mL 24 h post-dose and 14/16 subjects had concentrations higher than this target at 30 h post-dose (GM of 759 and 407 ng/mL, respectively). Thirteen out of 16 subjects had darunavir concentrations higher than the target of 550 ng/mL at 24 h post-dose and 5/16 subjects had concentrations higher than the target at 30 h post-dose (GM of 1033 and 382 ng/mL, respectively). Cobicistat half-life to 72 h was 4.21 h with atazanavir and 3.62 h with darunavir. GM values 24 h after the observed dose ( C 24 ) for atazanavir and darunavir were 141 and 43 ng/mL, respectively, in saliva and 24857 and 11878 ng/mL, respectively, in urine. Concentration decay in saliva/urine mirrored plasma concentrations for both drugs. Conclusions: Different concentration decay patterns were seen for atazanavir and darunavir, which may be partially explained by cobicistat half-life (longer with atazanavir than darunavir). For the first time, we also measured drug PK forgiveness in saliva and urine, which represent easier markers of adherence.

Therapeutic drug monitoring of boosted PIs in HIV-positive patients: undetectable plasma concentrations and risk of virological failure.

Background: Therapeutic drug monitoring (TDM) of antiretroviral drugs is performed in selected HIV-positive patients. The aim of this study was to estimate the prevalence of undetectable plasma concentrations of ritonavir and boosted PIs and to evaluate the association between those and the 48 week risk of virological failure. Methods: A TDM registry study and a retrospective follow-up study were conducted. Plasma concentrations were measured through validated methods. According to PI and ritonavir concentrations, patients were stratified as adherent, partially non-adherent or non-adherent. Virological outcome was evaluated 48 weeks afterwards. Results: The TDM registry study included 2468 samples collected from 723 patients (68.1% male, median age 43.5 years). Eighty-seven samples (3.5%, 74 patients) and 68 samples (2.8%, 52 patients) were in the partially non-adherent and non-adherent groups, respectively; more patients on atazanavir/ritonavir (7.9%) versus darunavir/ritonavir (2% twice daily and 1.9% once daily) and lopinavir/ritonavir (1.5%; P < 0.001) were observed in the partially non-adherent group. Two hundred and ninety patients were included in the follow-up study (64.1% male, median age 40 years). Patients in the adherent group had a higher chance of viral control [81.9% (167/204)] versus the partially non-adherent group and the non-adherent group [71.7% (33/46) and 53.1% (17/32), respectively; P  =   0.001]. Based on multivariate analysis, baseline HIV RNA >50 copies/mL ( P < 0.001), genotypic susceptibility score ≤2 ( P = 0.001), lower nadir CD4 cell count ( P = 0.003) and not being in the adherent group ( P = 0.029) were independent predictors of HIV RNA >50 copies/mL at 48 weeks. Conclusions: The measurement of PI and ritonavir plasma levels can uncover incomplete compliance with treatment; TDM may represent a useful tool for identifying patients in need of adherence-promoting interventions.

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.