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Introduction: The specific physiological background induced by pregnancy leads to significant changes in maternal pharmacokinetics, suggesting potential variability in plasma concentrations of antiretrovirals. Pregnant HIV patients exposed to subtherapeutic doses, particularly in the last trimester of the pregnancy, have higher chances to transmit the infection to their children. Therefore, the therapeutic drug monitoring of antiretrovirals in HIV pregnant patients would be of great value., Objectives: This study aimed to develop and validate a sensitive liquid chromatograph tandem mass spectrometry (LC-MS/MS) method for simultaneous quantification of efavirenz, raltegravir, atazanavir, and ritonavir in dried blood spots (DBS) and plasma., Design and Methods: The analytes were extracted from the DBS punch and plasma with a mixture of methanol:zinc sulfate 200 mM (50:50, v/v) and 100 % methanol, respectively. For the chromatographic separation a Shim-pack® C18, 4.6 mm × 150 mm, 5 μm column was used. Detection was performed in a 3200-QTRAP® mass spectrometer, with a run time of 6 min., Results: The assay was linear in the range of 15-1,000 ng/mL for raltegravir, 50-10,000 ng/mL for both atazanavir and ritonavir, 50-5,000 ng/mL for efavirenz. Precision and accuracy at these concentrations were less than 15 % for all analytes. Raltegravir, atazanavir, and ritonavir were stable for seven days at 23 °C and 40 °C, whereas efavirenz was stable for twenty-four hours at the same conditions., Conclusions: The method was successfully applied to quantify efavirenz in DBS samples obtained from HIV-1 infected pregnant volunteers under antiretroviral therapy. The concentrations of efavirenz in DBS and plasma were comparable according to Passing-Bablok regression and Bland-Altman analysis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.)

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., Competing Interests: I have read the journal's policy and the authors of this manuscript have the following competing interests: ET has received honoraria as a speaker from Janssen. CJT and ÅM has received honoraria as speaker and/or scientific advisor from Gilead Sciences, and GlaxoSmithKline/ViiV. AT reports during the conduct of the study; personal fees from Gilead, personal fees from Janssen and personal fees from GSK /ViiV outside the submitted work. MG has received research grants from Gilead Sciences and Janssen-Cilag and honoraria as speaker and/or scientific advisor from Bristol-Myers Squibb, Gilead Sciences, GlaxoSmithKline/ViiV, Janssen-Cilag, and MSD. LMA has received an unrestricted research grant from Bristol Myers Squibb. For the remaining authors none were declared. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

We describe the design, synthesis and pharmacokinetic (PK) evaluation of a series of amino acid-based prodrugs of the HIV-1 protease inhibitor atazanavir (1) derivatized on the pharmacophoric secondary alcohol using a (carbonyl)oxyalkyl linker. Prodrugs of 1 incorporating simple (carbonyl)oxyalkyl-based linkers and a primary amine in the promoiety were found to exhibit low chemical stability. However, chemical stability was improved by modifying the primary amine moiety to a tertiary amine, resulting in a 2-fold enhancement of exposure in rats following oral dosing compared to dosing of the parent drug 1. Further refinement of the linker resulted in the discovery of 22 as a prodrug that delivered the parent 1 to rat plasma with a 5-fold higher AUC and 67-fold higher C 24 when compared to oral administration of the parent drug. The PK profile of 22 indicated that plasma levels of this prodrug were higher than that of the parent, providing a more sustained release of 1 in vivo., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Masson SAS. All rights reserved.)

This work strived to explore gastrointestinal (GI) dissolution, supersaturation and precipitation of the weakly basic drug atazanavir in humans under different 'real-life' intake conditions. The impact of GI pH and motility on these processes was thoroughly explored. In a cross-over study, atazanavir (Reyataz®) was orally administered to 5 healthy subjects with (i) a glass of water, (ii) a glass of Coca-Cola® and (iii) a glass of water under hypochlorhydric conditions (induced by concomitant intake of a proton-pump inhibitor (PPI)). After intake, GI fluids were aspirated from the stomach and the duodenum and, subsequently, analyzed for atazanavir. In parallel, blood samples were collected to assess systemic concentrations. In general, the results of this study revealed that the acidic gastric pH in combination with gastric residence time played a crucial role in the dissolution of atazanavir along the GI tract. After intake of atazanavir with a glass of water (i.e., reference condition), complete gastric dissolution was observed. After GI transfer, supersaturation was noticed for a limited amount of time (1.25 h). With respect to the Coca-Cola® condition, complete gastric dissolution was also observed. A delay in gastric emptying, highly likely caused by the caloric content (101 kcal), was responsible for delayed arrival of atazanavir into the upper small intestine, creating a longer time window of supersaturated concentrations in the duodenal segment (3.25 h) compared to the water condition. The longer period of supersaturated concentrations resulted in a slightly higher systemic exposure of atazanavir compared to the condition when atazanavir was taken with a glass of water. A remarkable observation was the creation (when the drug was given in the migrating motor complex (MMC) phase 2) or maintenance (when the drug was given in MMC phase 1) of a quiescent phase for up to 80 min. With respect to the PPI condition, negligible gastric and intestinal concentrations were observed, resulting in minimal systemic exposure for all subjects. It can be concluded that gastric pH and residence time play a pivotal role in the intestinal disposition of atazanavir in order to generate sufficiently high concentrations further down in the intestinal tract for a sufficient period of time, thus creating a beneficial driving force for intestinal absorption., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Background: Drug-drug interactions between orally administered antiretroviral therapy (ART) and hormones released from an intravaginal ring are not known. We hypothesised that ART containing either efavirenz or ritonavir-boosted atazanavir would alter plasma concentrations of vaginally administered etonogestrel and ethinylestradiol but that ART concentrations would be unchanged during use of an intravaginal ring., Methods: We did a parallel, three-group, pharmacokinetic evaluation at HIV clinics in Asia (two sites), South America (five), sub-Saharan Africa (three), and the USA (11) between Dec 30, 2014, and Sept 12, 2016. We enrolled women with HIV who were either ART-naive (control group; n=25), receiving efavirenz-based ART (n=25), or receiving atazanavir-ritonavir-based ART (n=24). Women receiving ART were required to be on the same regimen for at least 30 days, with 400 copies or less per mL of plasma HIV-1 RNA; women not receiving ART had CD4 counts of 350 cells per μL or less. We excluded participants who had a bilateral oophorectomy or conditions that were contraindicated in the intravaginal ring product labelling. An intravaginal ring releasing etonogestrel and ethinylestradiol was inserted at entry (day 0). Single plasma samples for hormone concentrations were collected on days 7, 14, and 21 after intravaginal ring insertion. The primary outcome was the plasma concentration of etonogestrel and ethinylestradiol on day 21. Etonogestrel and ethinylestradiol concentrations were compared between each ART group and the control group by geometric mean ratio (GMR) with 90% CIs and Wilcoxon rank-sum test. As secondary outcomes, efavirenz or ritonavir-boosted atazanavir concentrations were assessed by 8-h intensive pharmacokinetic sampling at entry before intravaginal ring insertion and before intravaginal ring removal on day 21. Antiretroviral areas under the concentration-time curve (AUC 0-8 h ) were compared before and after intravaginal ring insertion by GMR (90% CI) and Wilcoxon signed-rank test. This study is registered with ClinicalTrials.gov, number NCT01903031., Findings: Between Dec 30, 2014, and Sept 12, 2016, we enrolled 84 participants in the study; ten participants were excluded from the primary hormone analysis. 74 participants met the primary endpoint: 25 in the control group, 25 in the efavirenz group, and 24 in the atazanavir group. On day 21 of intravaginal ring use, participants receiving efavirenz had 79% lower etonogestrel (GMR 0·21, 90% CI 0·16-0·28; p<0·0001) and 59% lower ethinylestradiol (0·41, 0·32-0·52; p<0·0001) concentrations compared with the control group. By contrast, participants receiving ritonavir-boosted atazanavir had 71% higher etonogestrel (1·71, 1·37-2·14; p<0·0001), yet 38% lower ethinylestradiol (0·62, 0·49-0·79; p=0·0037) compared with the control group. The AUC 0-8 h of efavirenz or atazanavir did not differ between the groups., Interpretation: Hormone exposure was significantly lower when an intravaginal ring contraceptive was combined with efavirenz-based ART. Further studies designed to examine pharmacodynamic endpoints, such as ovulation, when intravaginal ring hormones are combined with efavirenz are warranted., Funding: National Institutes of Health, through the AIDS Clinical Trials Group and the International Maternal Pediatric Adolescent AIDS Clinical Trials Network, National Institute of Allergy and Infectious Diseases, Eunice Kennedy Shriver National Institute of Child Health and Human Development, and the National Institute of Mental Health., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Aim: To evaluate the influence of genetic polymorphisms on plasma trough concentrations of atazanavir (ATV) and ritonavir (RTV). Patients & methods: The concentration-to-dose ratios were compared between different genotype groups of CYP3A5 , ABCB1 , SLCO1B1  and NR1I2 in 490 patients. Multiple regression analysis was used to examine the association between genetic and clinical factors and log-transformed concentration-to-dose ratio of ATV and RTV. Results: Higher concentrations of ATV and RTV were significantly associated with CYP3A5 6986 GG and SLCO1B1 521 TC or CC. Female patients had significantly higher ATV plasma concentration than male patients. Conclusion: Genetic polymorphisms and gender are factors affecting the variability of ATV and RTV concentrations in the Thai population. Thus, genetic testing is worth considering when atazanavir + low dose ritonavir is prescribed.

Background: Cotrimoxazole (TMP-SMX) is concomitantly used as a primary prophylaxis of opportunistic infections with antiretroviral agents, such as Atazanavir (ATV). Results from an ex vivo study showed changes in intestinal absorption of ATV when rats were pretreated with TMP-SMX. The objective of this in vivo study is to determine the effect of TMP-SMX on the pharmacokinetics of ATV in rats. We also studied changes in gut microbiota induced by TMP-SMX., Methods: We used the non-compartment analysis to compare the pharmacokinetics of ATV in a parallel group of rats treated with a low or therapeutic dose of TMP-SMX for nine days to untreated control rats. Gut microbiota was characterized using qPCR and High Throughput Sequencing of 16S rDNA., Results: Rats treated with TMP-SMX showed a much broader exposure to ATV compared to the control group (AUC0-8h (ng.mL-1.h), 25975.9±4048.7 versus 2587.6±546.9, p=0.001). The main observation regarding the gut microbiota was a lower proportion of enterobacteria related to the administration of TMP-SMX. Moreover, the Total Gastrointestinal Transit Time (TGTT) was longer in the TMP-SMX treated group., Conclusion: Concomitant administration of TMP-SMX and ATV significantly increased ATV exposure in rats. This increase could be the result of a prolonged TGTT leading to an increase in the intestinal residence time of ATV favoring its absorption. Gut microbiota changes induced by TMP-SMX could be at the origin of this prolonged TGTT. If demonstrated in humans, this potential interaction could be accompanied by an increase in the adverse effects of ATV., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Background: Cotrimoxazole is the main antibiotic used in primary prophylaxis for opportunistic infections in advanced HIV infection. This drug can inhibit one of the metabolic pathways of atazanavir (ATV), such as the cytochromes P450 (CYP) 2C8/2C9 and could interfere with its safety and efficacy., Objective: We studied the drug-drug interaction (DDI) between cotrimoxazole and ATV by using therapeutic drug monitoring (TDM) and pharmacovigilance (PV) approaches., Methods: We compared a group of patients treated with cotrimoxazole and receiving an ATV-based regimen to controls. This historical cohort analysis used data from Dat'AIDS in HIV-infected patients who had at least two lowest plasma concentrations (C-trough) of ATV during their outpatient follow-up. Likewise, we used the international pharmacovigilance data from VigiBase to evaluate the notifications of hyperbilirubinemia reported with ATV., Results: In the TDM analysis, the two groups of patients (treated with cotrimoxazole and controls) were almost homogeneous concerning the main baseline features. After at least six months of ATVbased regimen, there was no significant difference in the safety threshold of the ATV C-trough [with an adjusted odds ratio (aOR) of 1.4 (95% CI: 0.5 - 4.4)] compared to controls. We observed similar results with the efficacy thresholds of ATV C-trough. Regarding the PV analysis, there was no difference in hyperbilirubinemia occurring with ATV when cotrimoxazole was concomitant, with an adjusted reporting odds ratio (aROR) of 0.9 (95% CI: 0.6 to 1.2)., Conclusion: This study showed a relevant concomitant use between Cotrimoxazole and ATV based on TDM and PV approaches., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Drug-combination nanoparticles (DcNPs) administered subcutaneously represent a potential long-acting lymphatic-targeting treatment for HIV infection. The DcNP containing lopinavir (LPV)-ritonavir (RTV)-tenofovir (TFV), Targeted-Long-Acting-Antiretroviral-Therapy product candidate 101 (TLC-ART 101), has shown to provide long-acting lymphocyte-targeting performance in nonhuman primates. To extend the TLC-ART platform, we replaced TLC-ART 101 LPV with second-generation protease inhibitor, atazanavir (ATV). Pharmacokinetics of the ATV-RTV-TFV DcNP was assessed in macaques, in comparison to the equivalent free drug formulation and to the TLC-ART 101. After single subcutaneous administration of the DcNP formulation, ATV, RTV, and TFV concentrations were sustained in plasma for up to 14 days, and in peripheral blood mononuclear cells for 8 to 14 days, compared with 1 to 2 days in those macaques treated with free drug combination. By 1 week, lymph node mononuclear cells showed significant levels for all 3 drugs from DcNPs, whereas the free controls were undetectable. Compared with TLC-ART 101, the ATV-RTV-TFV DcNP exhibited similar lymphocyte-targeted long-acting features for all 3 drugs and similar pharmacokinetics for RTV and TFV, whereas some pharmacokinetic differences were observed for ATV versus LPV. The present study demonstrated the flexibility of the TLC-ART's DcNP platform to include different antiretroviral combinations that produce targeted long-acting effects on both plasma and cells., (Copyright © 2018 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.)

Atazanavir-ritonavir concentrations change over time during pregnancy in HIV-positive patients; the impact of genetic variants is unknown. Twenty patients were enrolled in this study; plasma and intracellular concentrations of antiretrovirals were measured, in addition to single-nucleotide polymorphisms in transport-related genes. Linear logistic regression showed that genetic variants in organic-anion-transporter-1B1- and pregnane-X-receptor-encoding genes affected third-trimester atazanavir exposure. In this prospective study, genetic variants partially explained the observed interpatient variability in third-trimester exposure to antiretrovirals., (Copyright © 2018 American Society for Microbiology.)

Background/purpose: Treatment response to switch regimens containing unboosted atazanavir and tenofovir disoproxil fumarate (TDF)/lamivudine guided by therapeutic drug monitoring in human immunodeficiency virus-infected patients is rarely investigated., Methods: Consecutive patients with plasma human immunodeficiency virus RNA load < 200 copies/mL switching to unboosted atazanavir plus zidovudine-lamivudine (coformulated), abacavir-lamivudine (coformulated), or TDF/lamivudine > 3 months were included for determinations of treatment response, plasma atazanavir concentrations, and single-nucleotide polymorphisms of MDR1, PXR, and UGT1A1 genes from 2010 to 2014. Treatment failure was defined as either discontinuation of atazanavir for any reason or plasma viral load ≥ 200 copies/mL within 96 weeks., Results: During the study period, 128 patients switched to unboosted atazanavir with TDF/lamivudine (TDF group) and 186 patients switched to unboosted atazanavir with two other nucleoside reverse-transcriptase inhibitors (non-TDF group). There were no statistically significant differences in the distributions of single-nucleotide polymorphisms of MDR1 (2677 and 3435), PXR genotypes (63396), and UGT1A1*28 between the two groups. Recommended plasma atazanavir concentrations were achieved in 83.5% and 64.9% of the TDF group and non-TDF group, respectively (p < 0.01). After a median follow-up duration of 96.0 weeks, treatment failure occurred in 19 (14.9%) and 34 (18.3%) patients in the TDF group and non-TDF group, respectively (p = 0.60). Low-level viremia (40-200 copies/mL) before switch (adjusted hazard ratio, 2.12; 95% confidence interval, 1.12-4.01) and without therapeutic drug monitoring (adjusted hazard ratio, 2.08; 95% confidence interval, 1.16-3.73) were risk factors for treatment failure., Conclusion: Switch to unboosted atazanavir with TDF/lamivudine achieves a similar treatment response to that with two other nucleoside reverse-transcriptase inhibitors in patients achieving virological suppression with the guidance of therapeutic drug monitoring., (Copyright © 2016. Published by Elsevier B.V.)

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., (© The Author 2017. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

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., (© The Author 2017. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

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.

Aims: The aim of the present study was to develop a simultaneous population pharmacokinetic model for atazanavir (ATV) incorporating the effect of ritonavir (RTV) on clearance to predict ATV concentrations under different dosing regimens in HIV-1-infected patients., Methods: A Cross-sectional study was carried out in 83 HIV-1-infected adults taking ATV 400 mg or ATV 300 mg/RTV 100 mg once daily. Demographic and clinical characteristics were registered and blood samples collected to measure drug concentrations. A population pharmacokinetic model was constructed using nonlinear mixed-effects modelling and used to simulate six dosing scenarios., Results: The selected one-compartmental model described the pharmacokinetics of RTV and ATV simultaneously, showing exponential, direct inhibition of ATV clearance according to the RTV plasma concentration, which explained 17.5% of the variability. A mean RTV plasma concentration of 0.63 mg l -1 predicted an 18% decrease in ATV clearance. The percentages of patients with an end-of-dose-interval concentration of ATV below or above the minimum and maximum target concentrations of 0.15 mg l -1 and 0.85 mg l -1 favoured the selection of the simulated ATV/RTV once-daily regimens (ATV 400 mg, ATV 300 mg/RTV 100 mg, ATV 300 mg/RTV 50 mg, ATV 200/RTV 100 mg) over the unboosted twice-daily regimens (ATV 300 mg, ATV 200 mg)., Conclusions: A one-compartment simultaneous model can describe the pharmacokinetics of RTV and ATV, including the effect of RTV plasma concentrations on ATV clearance. This model is promising for predicting individuals' ATV concentrations in clinical scenarios, and supports further clinical trials of once-daily doses of ATV 300 mg/RTV 50 mg or ATV 200 mg/RTV 100 mg to confirm efficacy and safety., (© 2016 The British Pharmacological Society.)

Raltegravir is a human immunodeficiency virus (HIV)-1 integrase strand transfer inhibitor currently marketed at a dose of 400 mg twice-daily (b.i.d.). Raltegravir 1200 mg once-daily (q.d.) (investigational q.d. formulation of 2 × 600 mg tablets; q.d. RAL) was found to be generally well tolerated and non-inferior to the marketed 400 mg b.i.d. dose at 48 weeks in a phase 3 trial. Since raltegravir is eliminated mainly by metabolism via a uridine diphosphate glucuronosyltransferase (UGT) 1A1-mediated glucuronidation pathway, co-administration of UGT1A1 inhibitors may increase the plasma levels of q.d. RAL. To assess this potential, the drug interaction of 1200 mg raltegravir using atazanavir, a known UGT1A1 inhibitor, was studied. An open-label, randomized, 2-period, fixed-sequence phase 1 study was performed in adult healthy male and female (non-childbearing potential) subjects ≥ 19 and ≤ 55 years of age, with a body mass index (BMI) ≥ 18.5 and ≤ 32.0 kg/m 2 . Subjects (n = 14) received a single oral dose of 1200 mg raltegravir in period 1. After a washout period of at least 7 days, the subjects received oral doses of 400 mg atazanavir q.d. for 9 consecutive days, with a single oral dose of 1200 mg raltegravir co-administered on day 7 of period 2. Serial blood samples were collected for 72 h following raltegravir dosing and analysed using a validated bioanalytical method to quantify raltegravir plasma concentrations. Co-administration with atazanavir yielded GMRs (90% CIs) for raltegravir AUC 0-∞ , C max and C 24 of 1.67 (1.34, 2.10), 1.16 (1.01, 1.33) and 1.26 (1.08, 1.46), respectively. There was no effect of raltegravir on serum total bilirubin. In contrast, atazanavir increased the mean bilirubin by up to 200%, an effect that was preserved in the atazanavir/raltegravir treatment group. Administration of single q.d. RAL alone and co-administered with multiple oral doses of atazanavir were generally well tolerated in healthy subjects. The results show that atazanavir increased the PK exposure of raltegravir; therefore, co-administration of atazanavir with raltegravir q.d. is not recommended. Copyright © 2016 John Wiley & Sons, Ltd., (Copyright © 2016 John Wiley & Sons, Ltd.)

HIV protease inhibitor use in pediatrics is challenging due to the poor palatability and/or toxicity of concomitant low-dose ritonavir. Atazanavir without ritonavir (unboosted) is not recommended for patients with prior virologic failure, a common problem for perinatally-infected adolescents. Atazanavir 400 mg once-daily provided suboptimal exposure. Higher unboosted doses or splitting the daily dose to twice-daily warrants investigation in this treatment-experienced population., Competing Interests: The authors have no conflicts of interest or funding to disclose.

Background: Population pharmacokinetic (PopPK) analyses often rely on steady state and full adherence to prescribed dosage regimen assumptions from data gathered during therapeutic drug monitoring (TDM). Nonadherence is common in chronic diseases such as HIV. This study evaluates the impact of adherence measurement by electronic monitoring on PopPK parameter estimation and individual concentration profile predictions, and also the influence of adherence issues on the clinical interpretation of a concentration measurement., Methods: Published PopPK models for lopinavir, atazanavir, efavirenz, and etravirine were applied to estimate PK parameters and individual concentrations in 140 HIV patients taking part in a medication adherence program using 2 dosing data sets. The first set included the last dose reported by the patient with steady-state and full adherence assumptions; the second set used detailed electronic dosing history. PopPK parameter estimates and individual predictions were compared between the 2 dosing entries., Results: Clearance estimates and likewise predicted concentrations did not markedly differ between the 2 dosing histories. However, certain patterns of nonadherence such as sparse missed doses or consecutive missed doses lead to suboptimal drug exposure. The interpretation based on self-reported information would have concluded on a wrongly appropriate individual exposure., Conclusions: PopPK analysis assuming steady state with full adherence produced similar results to those based on detailed electronic dosing history reconciled with patients' allegations. Self-reported last dose intake appeared reliable for concentration predictions and therapeutic drug monitoring interpretation for most patients followed at the medication adherence program. Yet, clinicians should be aware that concentration predictions based on self-reported last dose intake might be overestimated in case of undetected patterns of nonadherence, increasing the risk of forthcoming therapeutic failure.

In the treatment of HIV infection, a combination of anti-HIV drugs is commonly used in highly active antiretroviral therapy (HAART). One such combination recommended for clinical therapy consists of the two HIV protease inhibitors atazanavir and ritonavir and the HIV nucleotide reverse transcriptase inhibitor tenofovir. The detection of plasma and cell drug concentrations provides an assessment of actual drug exposure and patient compliance. We thus developed a simple, efficient, and sensitive method to simultaneously extract and detect these three drugs in plasma and peripheral blood mononuclear cells. The use of a liquid-liquid extraction followed by protein precipitation provided a simple process, yielding a high recovery rate for all three drugs in plasma (>92%) and in cells (>86%). The liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay was able to detect 0.01, 0.25, and 2.5 pg (2, 50, and 500 pg/ml, respectively) in 5 μl for atazanavir, ritonavir, and tenofovir, respectively. Validation of the method exhibited high precision and accuracy. This method was subsequently applied to a primate study to determine the concentrations of all three drugs in both plasma and cell samples. This validated method can be useful for an evaluation of drug concentrations in biological samples in an efficient and sensitive manner., (Copyright © 2015, American Society for Microbiology. All Rights Reserved.)

Many active pharmaceutical ingredients (APIs) exhibit a highly variable pharmacokinetic (PK) profile. This behavior may be attributable to pre-absorptive, absorptive and/or post-absorptive factors. Pre-absorptive factors are those related to dosage form disintegration, drug dissolution, supersaturation, precipitation and gastric emptying. Absorptive factors are involved with drug absorption and efflux mechanisms, while drug distribution and clearance are post-absorptive factors. This study aimed to investigate the relative influence of the aforementioned parameters on the pharmacokinetic profile of atazanavir, a poorly soluble weakly basic compound with highly variable pharmacokinetics. The pre-absorptive behavior of the drug was examined by applying biorelevant in vitro tests to reflect upper gastrointestinal behavior in the fasted and fed states. The in vitro results were implemented, along with permeability and post-absorptive data obtained from the literature, into physiologically based pharmacokinetic (PBPK) models. Sensitivity analysis of the resulting plasma profiles revealed that the pharmacokinetic profile of atazanavir is affected by an array of factors rather than one standout factor. According to the in silico model, pre-absorptive and absorptive factors had less impact on atazanavir bioavailability compared to post-absorptive parameters, although active drug efflux and extraction appear to account for the sub-proportional pharmacokinetic response to lower atazanavir doses in the fasted state. From the PBPK models it was concluded that further enhancement of the formulation would bring little improvement in the pharmacokinetic response to atazanavir. This approach may prove useful in assessing the potential benefits of formulation enhancement of other existing drug products on the market., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Introduction: Ritonavir-boosted atazanavir (ATV/r) is a relatively well tolerated antiretroviral drug. However, side effects including hyperbilirubinemia, dyslipidemia, nephrolithiasis and cholelithiasis have been reported in the medium and long term. Unboosted ATV may be selected for some patients because it has fewer gastrointestinal adverse effects, less hyperbilirubinemia and less impact on lipid profiles., Methods: We investigated the distribution of ATV plasma trough concentrations according to drug dosage and the potential relationship between ATV plasma trough concentrations and drug-related adverse events in a consecutive series of 240 HIV-infected patients treated with ATV/r 300/100 mg (68%) or ATV 400 mg (32%)., Results: 43.9% of patients treated with ATV/r 300/100 mg had ATV concentrations exceeding the upper therapeutic threshold. A significant and direct association has been observed between the severity of hyperbilirubinemia and ATV plasma trough concentrations (ATV concentrations: 271 [77-555], 548 [206-902], 793 [440-1164], 768 [494-1527] and 1491 [1122-1798] ng/mL in patients with grade 0, 1, 2, 3 and 4 hyperbilirubinemia, respectively). In an exploratory analysis we found that patients with dyslipidemia or nephrolitiasis had ATV concentrations significantly higher (582 [266-1148], and 1098 [631-1238] ng/mL, respectively) (p<0.001), as compared with patients with no ATV-related complications (218 [77-541] ng/mL)., Conclusions: A significant proportion of patients treated with the conventional dosage of ATV (300/100) had plasma concentrations exceeding the upper therapeutic threshold. These patients that are at high risk to experience ATV-related complications may benefit from TDM-driven adjustments in ATV dosage with potential advantages in terms of costs and toxicity.

Background: Emerging evidence shows that standard atazanavir (ATV) dosages are associated with considerable interindividual variability in plasma drug concentrations. Given the potential impact of ATV exposure on clinical outcome, in this retrospective study we sought to assess demographic and clinical factors influencing ATV plasma concentrations in a large cohort of HIV-infected patients., Methods: HIV-infected patients treated with ATV for at least 3 months and with at least one assessment of ATV trough concentrations were enrolled. Blood trough samples were collected from all patients immediately before the next drug intake. Plasma ATV and ritonavir concentrations were quantified by a validated chromatographic method coupled with tandem mass spectrometric detection. Univariate and multivariate regression analyses were performed using ATV plasma concentrations as the dependent variable, with demographic and clinical characteristics as the independent ones., Results: A total of 273 HIV-infected adult patients were included in the present study. Factors significantly associated with increased ATV concentrations by univariate analysis were ATV dosage, number of concomitant drugs, ritonavir or statin use. However, with multivariate regression analysis, the only factors independently and significantly associated with ATV concentrations were ritonavir use (r=0.291, P<0.0001) and concomitant rosuvastatin therapy (r=0.315, P<0.0001)., Conclusions: We found that patients on ATV/ritonavir given rosuvastatin concomitantly have ATV concentrations that exceed the upper therapeutic threshold of 800 ng/ml known to be associated with a high risk of experiencing ATV-related side effects. In agreement with previous findings we confirmed the lack of association between other demographic and clinical characteristics such as age, gender, body weight and ATV exposure.