Effect of adherence as measured by MEMS, ritonavir boosting, and CYP3A5 genotype on atazanavir pharmacokinetics in treatment-naive HIV-infected patients

Pharmacokinetic Model of Tenofovir and Emtricitabine and Their Intracellular Metabolites in Patients in the ANRS 134-COPHAR 3 Trial Using Dose Records

Tenofovir (TFV) and emtricitabine (FTC) are part of the recommended highly active antiretroviral therapy (ART). Both molecules show a large interindividual pharmacokinetic (PK) variability. Here, we modeled the concentrations of plasma TFV and FTC and their intracellular metabolites (TFV diphosphate [TFV-DP] and FTC triphosphate [FTC-TP]) collected after 4 and 24 weeks of treatment in 34 patients from the ANRS 134-COPHAR 3 trial. These patients received daily (QD) atazanavir (300 mg), ritonavir (100 mg), and a fixed-dose combination of coformulated TFV disoproxil fumarate (300 mg) and FTC (200 mg). Dosing history was collected using a medication event monitoring system. A three-compartment model with absorption delay (Tlag) was selected to describe the PK of, respectively, TFV/TFV-DP and FTC/FTC-TP. TFV and FTC apparent clearances, 114 L/h (relative standard error [RSE] = 8%) and 18.1 L/h (RSE = 5%), respectively, were found to decrease with age. However, no significant association was found with the polymorphisms ABCC2 rs717620, ABCC4 rs1751034, and ABCB1 rs1045642. The model allows prediction of TFV-DP and FTC-TP concentrations at steady state with alternative regimens.

Will the Use of Pharmacogenetics Improve Treatment Efficiency in COVID-19?

The COVID-19 pandemic is associated with a global health crisis and the greatest challenge for scientists and doctors. The virus causes severe acute respiratory syndrome with an outcome that is fatal in more vulnerable populations. Due to the need to find an efficient treatment in a short time, there were several drugs that were repurposed or repositioned for COVID-19. There are many types of available COVID-19 therapies, including antiviral agents (remdesivir, lopinavir/ritonavir, oseltamivir), antibiotics (azithromycin), antiparasitics (chloroquine, hydroxychloroquine, ivermectin), and corticosteroids (dexamethasone). A combination of antivirals with various mechanisms of action may be more efficient. However, the use of some of these medicines can be related to the occurrence of adverse effects. Some promising drug candidates have been found to be ineffective in clinical trials. The knowledge of pharmacogenetic issues, which translate into variability in drug conversion from prodrug into drug, metabolism as well as transport, could help to predict treatment efficiency and the occurrence of adverse effects in patients. However, many drugs used for the treatment of COVID-19 have not undergone pharmacogenetic studies, perhaps as a result of the lack of time.

Pharmacogenetics-based population pharmacokinetic analysis for dose optimization of ritonavir-boosted atazanavir in Thai adult HIV-infected patients

BACKGROUND

This population pharmacokinetic-pharmacogenetic study aimed to investigate the optimal dose of RTV-boosted ATV (ATV/RTV) for Thai adult HIV-infected patients.

METHODS

A total of 1460 concentrations of ATV and RTV from 544 patients receiving an ATV/RTV-based regimen were analyzed. The CYP3A5 6986 A > G, ABCB1 3435 C > T, ABCB1 2677 G > T, SLCO1B1 521 T > C, and NR1I2 63396 C > T were genotyped. A population pharmacokinetic model was performed using a nonlinear mixed-effect model (NONMEM®). Monte Carlo simulations were conducted to compare the percentages of patients achieving the therapeutic range of ATV through concentrations (C_trough).

RESULTS

The apparent oral clearance of ATV (CL/F_ATV) without RTV was 7.69 L/h with interindividual variability (IIV) of 28.7%. Patients with CYP3A5 6986 GG had a 7.1% lower CL/F_ATV than those with AA or AG genotype. The CL/F_ATV decreased by 10.8% for females compared with males. Simulation results showed higher percentages (~70%) of patient receiving doses of 200/100 or 200/50 mg achieved the target ATV C_trough, while more patients (~40%) receiving a standard dose (300/100 mg) had ATV C_trough above this target.

CONCLUSIONS

Both CYP3A5 6986 A > G and female decreased CL/F_ATV in Thai HIV-infected patients. Simulations supported that the reduced dose of ATV/RTV was sufficient to achieve the target concentration for Thai population.

Pharmacogenomics and Pharmacogenetics: In Silico Prediction of Drug Effects in Treatments for Novel Coronavirus SARS-CoV2 Disease

The latest developments in precision medicine allow the modulation of therapeutic approaches in different pathologies on the basis of the specific molecular characterization of the patient. This review of the literature coupled with in silico analysis was to provide a selected screening of interactions between single-nucleotide polymorphisms (SNPs) and drugs (repurposed, investigational, and biological agents) showing efficacy and toxicityin counteracting Covid-19 infection. In silico analysis of genetic variants related to each drug was performed on such databases as PharmGKB, Ensembl Genome Browser, www.drugs.com, and SNPedia, with an extensive literature review of papers (to May 10, 2020) on Covid-19 treatments using Medline, Embase, International Pharmaceutical Abstracts, PharmGKB, and Google Scholar. The clinical relevance of SNPs, known as both drug targets and markers, considering genetic variations with known drug responses, and the therapeutic consequences are discussed. In the context of clinical treatment of Covid-19, including infection prevention, control measures, and supportive care, this review highlights the importance of a personalized approach in the final selection of therapy, which is probably essential in the management of the Covid-19 pandemic.

Antiretroviral Therapy Concentrations Differ in Gut vs. Lymph Node Tissues and Are Associated With HIV Viral Transcription by a Novel RT-ddPCR Assay

BACKGROUND

Most HIV-infected cells during antiretroviral therapy (ART) persist in lymphoid tissues. Studies disagree on whether suboptimal tissue ART concentrations contribute to ongoing HIV replication during viral suppression.

METHODS

We performed a cross-sectional study in virally-suppressed HIV+ participants measuring lymphoid tissue ART [darunavir (DRV), atazanavir (ATV), and raltegravir (RAL)] concentrations by LC-MS/MS assay. Tissue and plasma ART concentrations were used to estimate TPRs and drug-specific tissue:inhibitory concentration ratios (TICs). HIV DNA and sequentially produced HIV RNA transcripts were quantified from rectal biopsies using droplet digital PCR (ddPCR) assays.

RESULTS

Tissue samples were collected in duplicate from 19 participants: 38 rectal, 8 ileal (4 RAL, 2 DRV, 2 ATV), and 6 lymph node (4 RAL, 2 DRV) samples. Overall, median TICs were higher for RAL than DRV or ATV (both P = 0.006). Median TICs were lower in lymph nodes vs. ileum (0.49 vs. 143, P = 0.028) or rectum (33, P = 0.019), and all ART levels were below target concentrations. Higher rectal TICs were associated with lower HIV RNA transcripts (read-through, long LTR, and Nef, P all < 0.026) and a lower long LTR RNA/long LTR DNA ratio (P = 0.021).

CONCLUSIONS

We observed higher tissue ART concentrations in ileum and rectum compared with lymph nodes. We observed higher HIV transcription in participants with lower rectal ART concentrations. These findings add to the limited data supporting the idea that viral transcription may be influenced by ART concentrations in lymphoid tissues. Further exploration of tissue pharmacokinetics is needed in future HIV eradication strategies.

Influence of CYP3A5 and SLCO1B1 polymorphisms on atazanavir/r concentrations in Thai HIV-infected patients

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.

Genetic influence of ABCG2, UGT1A1 and NR1I2 on dolutegravir plasma pharmacokinetics

Objectives

Dolutegravir has replaced efavirenz as first-line treatment in universal HIV guidelines. We sought to ascertain the contributory effect of SNPs in four key genes linked to dolutegravir disposition (UGT1A1, ABCG2, CYP3A and NR1I2) on plasma dolutegravir pharmacokinetics.

Methods

Paired pharmacogenetic/pharmacokinetic data from 93 subjects were analysed for association using multivariate linear regression.

Results

Co-occurring UGT1*28 and NR1I2 c.63396C&gt;T homozygosity was associated with a 79% increase in AUC0–24 (P = 0.001; 27% if analysed individually), whilst combined ABCG2 c.421C&gt;A and NR1I2 c.63396C&gt;T variants were associated with a 43% increase in Cmax (P = 0.002) and a 39% increase in AUC0–24 (P = 0.002). When analysed individually, homozygosity for the NR1I2 c.63396C&gt;T variant alleles was associated with a 28% increase in Cmax (P = 0.033) and homozygosity for the ABCG2 c.421C&gt;A variant alleles was associated with a 28% increase in Cmax (P = 0.047). The UGT1A1*28 (rs8175347) poor metabolizer status (*28/*28; *28/*37; *37/*37) was individually associated with a 27% increase in AUC0–24 (P = 0.020). The combination of UGT1A1*28 poor metabolizer and UGT1A1*6 intermediate metabolizer statuses correlated with a 43% increase in AUC0–24 (P = 0.023).

Conclusions

This study showed a pharmacogenetic association between dolutegravir pharmacokinetics and variants in the ABCG2, UGT1A1 and NR1I2 genes, particularly when combined. Further research is warranted to confirm these associations in population-specific studies and to investigate their putative relationship with dolutegravir pharmacodynamics.

Association of Pharmacogenetic Markers With Atazanavir Exposure in HIV-Infected Women

SORCS2 rs73208473 was recently associated with decreased atazanavir (ATV) concentration in the hair of women with seropositive HIV. Herein, we report on a pharmacogenetic study of women with seropositive HIV demonstrating a similar association between rs73208473 and dose-adjusted plasma ATV concentration in African Americans.

Tenofovir Plasma Concentration from Preexposure Prophylaxis at the Time of Potential HIV Exposure: a Population Pharmacokinetic Modeling and Simulation Study Involving Serodiscordant Couples in East Africa

The Partners Demonstration Project was a prospective, open-label, implementation science-driven study of preexposure prophylaxis (PrEP) among heterosexual HIV serodiscordant couples in Kenya and Uganda. Adherence data were collected using the Medication Event Monitoring System (MEMS), and time of sexual activity was collected using the mobile phone short message service (SMS). Two plasma samples were collected at a single study visit. We integrated adherence, pharmacokinetics, and SMS data using a population pharmacokinetic (PopPK) model to simulate tenofovir plasma concentrations from PrEP at the time of sexual activity. In the first stage of this analysis, we used data from the current study to update a prior PopPK model of tenofovir (TFV) developed with data from the Partners PrEP Study (a phase III clinical trial). The second stage involved simulating plasma concentrations at the time of sexual activity using empirical Bayes estimates (EBEs) derived from the final model. In addition, EBEs from a previously published parent metabolite model of TFV (MTN-001, an open-label 3-way crossover study in healthy women) was used to simulate tenofovir diphosphate (TFV-DP) concentrations. We estimated percent PrEP "coverage" as the number of reported sexual events during which simulated concentrations were above an a priori threshold concentrations associated with a high degree of protection from HIV infection: plasma TFV of >40 ng/ml and peripheral blood mononuclear cell (PBMC) TFV-DP concentration of >36 fmol/million cells. The levels of coverage were 72% for TFV and 81% for TFV-DP. These levels are consistent with a high degree of protection against HIV acquisition in this study of a pragmatic delivery model for antiretroviral-based HIV prevention.

Neurocognitive Impairment and Associated Genetic Aspects in HIV Infection

HIV enters the central nervous system (CNS) early after infection. HIV-associated neurocognitive disorders (HAND) remain a serious complication of HIV infection despite available antiretroviral therapy (ART). Neurocognitive deficits observed in HAND are heterogeneous, suggesting a variability in individuals' susceptibility or resiliency to the detrimental CNS effects of HIV infection. This chapter reviews primary host genomic changes (immune-related genes, genes implicated in cognitive changes in primary neurodegenerative diseases), epigenetic mechanisms, and genetic interactions with ART implicated in HIV progression or HAND/neurocognitive complications of HIV. Limitations of the current findings include diversity of the HAND phenotype and limited replication of findings across cohorts. Strategies to improve the precision of future (epi)genetic studies of neurocognitive consequences of HIV infection are offered.

A Genome-Wide Association Study Identifies a Candidate Gene Associated With Atazanavir Exposure Measured in Hair

Hair provides a direct measure of long-term exposure of atazanavir (ATV). We report the results of the first genome-wide association study (GWAS) of ATV exposure measured in hair in an observational cohort representative of US women living with HIV; the Women's Interagency HIV Study. Approximately 14.1 million single nucleotide polymorphisms (SNPs) were analyzed in linear regression-based GWAS, with replication, adjusted for nongenetic predictors collected under conditions of actual use of ATV in 398 participants. Lastly, the PharmGKB database was used to identify pharmacogene associations with ATV exposure. The rs73208473, within intron 1 of SORCS2, resulted in a 0.46-fold decrease in ATV exposure, with the strongest association (P = 1.71×10-8 ) in GWAS. A priori pharmacogene screening did not identify additional variants statistically significantly associated with ATV exposure, including those previously published in ATV plasma candidate pharmacogene studies. The findings demonstrate the potential value of pharmacogenomic GWAS in ethnically diverse populations under conditions of actual use.

Pharmacogenetic associations with cytochrome P450 in antiretroviral therapy: what does the future hold?

INTRODUCTION

Several antiretroviral drugs used to treat infection with the human immunodeficiency virus (HIV) are substrates of enzymes belonging to the cytochrome P450 (CYP) superfamily, which are polymorphically expressed. It may therefore be useful to take into account the genetic variation in these enzymes to predict the likelihood of anti-HIV treatment success, toxicity and the potential for drug-drug interactions. Areas covered: In this manuscript, the authors discuss the current state of knowledge regarding pharmacogenetic associations between CYP and all major antiretrovirals, as well as the importance of these associations. Expert opinion: While many pharmacogenetic associations for CYP have been described in the literature, replication studies are sometimes lacking. The implementation of this knowledge in clinical practice also remains difficult. Further efforts are required both to expand this field of knowledge and to enable its use in everyday clinical practice.

A novel statistical method for assessing effective adherence to medication and calculating optimal drug dosages

OBJECTIVE

We derive a novel model-based metric for effective adherence to medication, and validate it using data from the INhaler Compliance Assessment device (INCATM). This technique employs dose timing data to estimate the threshold drug concentration needed to maintain optimal health.

METHODS

The parameters of the model are optimised against patient outcome data using maximum likelihood methods. The model is fitted and validated by secondary analysis of two independent datasets from two remote-monitoring studies of adherence, conducted through clinical research centres of 5 Irish hospitals. Training data came from a cohort of asthma patients (~ 47,000 samples from 218 patients). Validation data is from a cohort of 204 patients with COPD recorded between 2014 and 2016.

RESULTS

The time above threshold measure is strongly predictive of adverse events (exacerbations) in COPD patients (Odds Ratio of exacerbation = 0.52 per SD increase in adherence, 95% Confidence Interval [0.34-0.79]). This compares well with the best known previous method, the Area Under the dose-time Curve (AUC) (Odds Ratio = 0.69, 95% Confidence Interval [0.48-0.99]). In addition, the fitted value of the dose threshold (0.56 of prescribed dosage) suggests that prescribed doses may be unnecessarily high given good adherence.

CONCLUSIONS

The resulting metric accounts for missed doses, dose-timing errors, and errors in inhaler technique, and provides enhanced predictive validity in comparison to previously used measures. In addition, the method allows us to estimate the correct dosage required to achieve the effect of the medication using the patients' own adherence data and outcomes. The adherence score does depend not on sex or other demographic factors suggesting that effective adherence is driven by individual behavioural factors.

Precision medicine for HIV: where are we?

To date, antiretroviral therapy is highly effective in HIV-affected patients, but the individualization of such a life-long therapy may be advised. This review briefly summarizes the main factors involved in the potential personalization of antiretroviral treatment. Relevant articles in English were identified by PubMed and recent congresses’ abstracts. Foremost influences concerning pharmacodynamics, therapeutic drug monitoring, pharmacogenetics, comorbidities, immune recovery and viral characteristics affecting the healthcare of HIV-positive patients are listed here. Furthermore, pharmacoeconomic aspects are mentioned. Applying pharmacokinetic and pharmacogenetic knowledge may be informative and guide the better choice of treatment in order to achieve long-term efficacy and avoid adverse events. Randomized investigations of the clinical relevance of tailored antiretroviral regimens are needed in order to obtain a better management of HIV/AIDS-affected patients.

Comparison of Population Pharmacokinetics Based on Steady-State Assumption Versus Electronically Monitored Adherence to Lopinavir, Atazanavir, Efavirenz, and Etravirine: A Retrospective Study

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.

Genetic Polymorphisms Affecting the Pharmacokinetics of Antiretroviral Drugs

BACKGROUND

Antiretroviral treatment is highly effective in enhancing HIV-positive patients' survival and quality of life. Despite an increased tolerability in recent years, a substantial amount of patients experience side effects. Antiretrovirals' efficacy and tolerability have been associated with plasma concentrations and single nucleotide polymorphisms in selected genes involved in drug disposition.

OBJECTIVE

Our aim was to review the current knowledge in genetic polymorphisms affecting plasma, intracellular or compartmental concentrations of antiretrovirals.

METHODS

A search of the PubMed database was conducted to identify relevant articles, using the following terms: 'pharmacogenetics' or 'pharmacogenomics' or 'single nucleotide polymorphisms' or 'genetic/allelic variants' and 'pharmacokinetics' or 'concentrations' and 'HIV' or 'antiretroviral'. Abstracts from the main HIV conferences during 2015 and 2016 were also searched using the same keywords. Abstracts were manually checked and, if relevant, full papers were obtained. Only articles published in English were selected.

RESULTS

Several genetic polymorphisms in genes coding enzymes involved in drug metabolism (cytochrome P450 isoenzymes and uridine diphosphate glucuronosyltransferases) and transport (P-glycoprotein, anionic and cationic transporters, other transporters), as well as nuclear receptors (pregnane X receptor and the constitutive androstane receptor), have been associated with concentrations of antiretrovirals. The extent of such influence, the conflicting data, and the potential clinical relevance are discussed in the main section of this article.

CONCLUSION

Genetic polymorphisms may affect antiretroviral disposition, as well as both efficacy and toxicity. Despite a large amount of data, such precious knowledge has seldom been applied in patients. Studies on the clinical relevance and cost effectiveness of tailoring antiretroviral regimens to patients' genetic assets are lacking, but their importance may grow with the increasing age and complexity of persons living with HIV/AIDS.

Population pharmacokinetics and dose optimisation of ritonavir-boosted atazanavir in Thai HIV-infected patients

There is evidence that Thai patients receiving standard doses of ritonavir (RTV)-boosted atazanavir (ATV/r) have high exposure to atazanavir (ATV) leading to a higher risk of toxicity. A lower dose of ATV/r may provide adequate exposure in this population. However, pharmacokinetic data on ATV/r in Thai patients required for dose adjustment are limited. This study aimed to develop a population pharmacokinetic model of ATV/r and to determine the influence of patient characteristics on ATV pharmacokinetics. Monte Carlo simulations were performed to estimate the proportion of patients achieving target ATV trough concentration (C_trough) with the standard ATV/r dose of 300/100 mg and a low dose of 200/100 mg once daily (OD). A total of 127 Thai HIV-infected patients were included in this study. One random blood sample was collected to determine ATV and RTV concentrations at each clinic visit from 100 patients. Intensive data from 27 patients enrolled in previous studies were also included. Data were analysed using the non-linear mixed-effects modelling approach. A one-compartment model with first-order absorption and elimination and absorption lag time best described the data. The population mean clearance of ATV/r was 4.93 L/h in female patients and was 28.7% higher in male patients. Simulation results showed a higher proportion of patients achieving ATV C_trough within the target range with ATV/r 200/100 mg compared with 300/100 mg. The 200/100 mg OD dose of ATV/r provides adequate ATV exposure in Thai HIV-infected patients. Therefore, a lower dose of ATV/r should be considered for Thai and Asian populations.

Population Pharmacokinetics of Tenofovir in HIV-1-Uninfected Members of Serodiscordant Couples and Effect of Dose Reporting Methods

Antiretroviral preexposure prophylaxis (PrEP) with once-daily dosing of tenofovir and tenofovir-emtricitabine was shown to be effective for preventing HIV-1 infection in individuals who had HIV-1-seropositive partners (the Partners PrEP Study). We developed a population pharmacokinetic model for tenofovir and investigated the impacts of different dose reporting methods. Dosing information was collected as patient-reported dosing information (PRDI) from 404 subjects (corresponding to 1,280 drug concentration records) from the main trial and electronic monitoring-based adherence data collected from 211 subjects (corresponding to 327 drug concentration records) in an ancillary adherence study. Model development was conducted with NONMEM (7.2), using PRDI with a steady-state assumption or using PRDI replaced with electronic monitoring records where available. A two-compartment model with first-order absorption was the best model in both modeling approaches, with the need for an absorption lag time when electronic monitoring-based dosing records were included in the analysis. Age, body weight, and creatinine clearance were significant covariates on clearance, but only creatinine clearance was retained in the final models per stepwise selection. Sex was not a significant covariate on clearance. Tenofovir population pharmacokinetic parameter estimates and the precisions of the parameters from the two final models were comparable with the point estimates of the parameters, differing from 0% to 35%, and bootstrap confidence intervals widely overlapped. These findings indicate that PRDI was sufficient for population pharmacokinetic model development in this study, with a high level of adherence per multiple measures.

Pharmacogenetics of unboosted atazanavir in HIV-infected individuals in resource-limited settings: a sub-study of the AIDS Clinical Trials Group (ACTG) PEARLS study (NWCS 342)

OBJECTIVES

The multinational PEARLS (ACTG A5175) study, conducted mainly in resource-limited settings, identified an increased treatment failure rate among HIV-infected individuals randomized to once-daily unboosted atazanavir, didanosine-EC, and emtricitabine compared with efavirenz-based regimens. We evaluated associations between selected human genetic polymorphisms and atazanavir pharmacokinetics in PEARLS.

METHODS

Polymorphisms in CYP3A5, ABCB1, SLCO1B1 and NR1I2 were genotyped in PEARLS participants randomized to atazanavir plus didanosine-EC plus emtricitabine in Peru, South Africa and the USA, who also consented to genetic analysis. Non-linear mixed-effects population pharmacokinetic modelling was used to predict atazanavir oral clearance (CL/F) and concentration at 24 h (C24). Atazanavir mono-oxidation metabolites M1 and M2 were quantified from the same single-point plasma sample used to quantify the parent drug. Data were log10 transformed for statistical analysis using unpaired t-tests and one-way ANOVA and are presented as geometric mean (95% CI).

RESULTS

Eighty-four HIV-infected participants were genotyped, including 44 Black Africans or African Americans and 28 women. Median age was 34 years. We identified 56 CYP3A5 expressers and 28 non-expressers. Atazanavir CL/F and C24 did not differ between CYP3A5 expressers and non-expressers: 13.2 (12.1-14.4) versus 12.7 L/h (11.7-13.9), P = 0.61, and 75.3 (46.1-123.0) versus 130.9 ng/mL (86.9-197.2), P = 0.14, respectively. M1/atazanavir and M2/atazanavir ratios were higher in expressers than in non-expressers: 0.0083 (0.0074-0.0094) versus 0.0063 (0.0053-0.0075), P = 0.008, and 0.0065 (0.0057-0.0073) versus 0.0050 (0.0042-0.0061), P = 0.02, respectively.

CONCLUSIONS

Expression of CYP3A5 appears to be associated with increased M1 and M2 atazanavir metabolite formation, without significantly affecting parent compound pharmacokinetics.

Opioid Use and Storage Patterns by Patients after Hospital Discharge following Surgery

INTRODUCTION

Opioid-based analgesic therapy represents a cornerstone of pain management after surgery. The recent rise in opioid sales and opioid overdoses suggests it is important to maximize the safety of opioid prescribing after surgery. Given that patients may live with other family members in the home, safe storage and appropriate disposal of excess opioids after hospital discharge are necessary to prevent unintended secondary exposures. Identifying characteristics of patients who are likely to be prescribed excess opioids after surgery may enable more targeted prescription practices and safety interventions. Our study aimed to elucidate patient-reported opioid use patterns and modes of home storage of opioids among patients discharged home after Cesarean section (C-section) and thoracic surgery. Specifically, we sought to identify characteristics of patients who reported using about half or more versus less of the opioids prescribed to them for use after hospital discharge.

METHODS

For this cohort study, we developed a survey on quality of analgesia following hospital discharge, amounts of opioids taken relative to the amount prescribed, reasons for not taking all prescribed medications, and storage and disposal methods for leftover opioids. Adult patients, who had C-section or thoracic surgery at a tertiary academic medical center, were given a web-based self-administered survey after discharge. Descriptive statistics (means and standard deviations, proportions) were used to describe the study sample and survey results. Comparisons between patients who reported taking about half or more versus less of the opioids prescribed to them for use after hospital discharge were made using unpaired t-tests, Mann-Whitney tests, and Chi-square tests as appropriate.

RESULTS

The majority (53%) of respondents after C-section (N = 30) reported taking either no or very few (less than 5) prescribed opioid pills; 83% reported taking half or less; and 17% of women, reported taking all or nearly all (5 or fewer pills left over) of their opioid prescription. In a cohort of patients after thoracic surgery (n = 31) 45% reported taking either no or very few (5 or less) prescribed opioid pills; 71% reported taking half or less; and 29% of patients reported taking all or nearly all (5 or fewer pills left over) of their opioid prescription. In both cohorts, use of opioids while hospitalized was higher in the group reporting using about half or more of prescribed opioids after discharge. Leftover opioids were stored in an unlocked location in 77% and 73% of cases following C-section and thoracic surgery, respectively.

CONCLUSION

Our findings from surveys in two distinct patient populations at a single academic medical center suggest that current opioid prescribing practices for pain management at hospital discharge following Cesarean section and thoracic surgery may not account for individual patients' analgesic requirements. Excess opioid pills are commonly stored in unsecured locations and represent a potential source for non-medical opioid use and associated morbidity and mortality in patients and their families. Research to develop goal-directed and patient-centered post-discharge opioid prescription practices and encourage opioid safety practices after surgery is needed.

Bayesian population modeling of drug dosing adherence

Adherence is a frequent contributing factor to variations in drug concentrations and efficacy. The purpose of this work was to develop an integrated population model to describe variation in adherence, dose-timing deviations, overdosing and persistence to dosing regimens. The hybrid Markov chain-von Mises method for modeling adherence in individual subjects was extended to the population setting using a Bayesian approach. Four integrated population models for overall adherence, the two-state Markov chain transition parameters, dose-timing deviations, overdosing and persistence were formulated and critically compared. The Markov chain-Monte Carlo algorithm was used for identifying distribution parameters and for simulations. The model was challenged with medication event monitoring system data for 207 hypertension patients. The four Bayesian models demonstrated good mixing and convergence characteristics. The distributions of adherence, dose-timing deviations, overdosing and persistence were markedly non-normal and diverse. The models varied in complexity and the method used to incorporate inter-dependence with the preceding dose in the two-state Markov chain. The model that incorporated a cooperativity term for inter-dependence and a hyperbolic parameterization of the transition matrix probabilities was identified as the preferred model over the alternatives. The simulated probability densities from the model satisfactorily fit the observed probability distributions of adherence, dose-timing deviations, overdosing and persistence parameters in the sample patients. The model also adequately described the median and observed quartiles for these parameters. The Bayesian model for adherence provides a parsimonious, yet integrated, description of adherence in populations. It may find potential applications in clinical trial simulations and pharmacokinetic-pharmacodynamic modeling.

Successful pharmacogenetics-based optimization of unboosted atazanavir plasma exposure in HIV-positive patients: a randomized, controlled, pilot study (the REYAGEN study)

BACKGROUND

Atazanavir without ritonavir, despite efficacy and tolerability, shows low plasma concentrations that warrant optimization.

METHODS

In a randomized, controlled, pilot trial, stable HIV-positive patients on atazanavir/ritonavir (with tenofovir/emtricitabine) were switched to atazanavir. In the standard-dose arm, atazanavir was administered as 400 mg once daily, while according to patients' genetics (PXR, ABCB1 and SLCO1B1), in the pharmacogenetic arm: patients with unfavourable genotypes received 200 mg of atazanavir twice daily. EudraCT number: 2009-014216-35.

RESULTS

Eighty patients were enrolled with balanced baseline characteristics. The average atazanavir exposure was 253 ng/mL (150-542) in the pharmacogenetic arm versus 111 ng/mL (64-190) in the standard-dose arm (P < 0.001); 28 patients in the pharmacogenetic arm (75.7%) had atazanavir exposure >150 ng/mL versus 14 patients (38.9%) in the standard-dose arm (P = 0.001). Immunovirological and laboratory parameters had a favourable outcome throughout the study with non-significant differences between study arms.

CONCLUSIONS

Atazanavir plasma exposure is higher when the schedule is chosen according to the patient's genetic profile.

Medication Routines and Adherence Among Hypertensive African Americans

Poor adherence to prescribed medication regimens remains an important challenge preventing successful treatment of cardiovascular diseases such as hypertension. While studies have documented differences in the time of day or weekday vs weekend on medication adherence, no study has examined whether having a medication-taking routine contributes to increased medication adherence. The purpose of this study was to: (1) identify patients' sociodemographic factors associated with consistent medication-taking routine; (2) examine associations between medication-taking consistency, medication adherence, and blood pressure (BP) control. The study included black patients with hypertension (n = 190; 22 men and 168 women; age, mean±standard deviation 54 ± 12.08 years) who completed a practice-based randomized controlled trial. Findings showed that medication-taking consistency was significantly associated with better medication adherence (F = 9.54, P = .002). Associations with the consistency index were not statistically significant for diastolic BP control (odds ratio, 1.319; 95% confidence interval, 0.410-4.246; P = .642) and systolic BP control (odds ratio, 0.621; 95% confidence interval, 0.195-1.974; P = .419).

Development and application of an aggregate adherence metric derived from population pharmacokinetics to inform clinical trial enrichment

Nonadherence to prescribed medication is a common barrier to effective treatment, and current options to determine adherence are limited. This study describes development of an aggregate adherence measure based on population pharmacokinetics (PK), and its comparison to a subjective questionnaire, the Morisky 8-item medication adherence scale (MMAS8), in a trial of psychiatric patients on stable doses of oral aripiprazole. A comprehensive model was first built using plasma drug concentration data from 24 clinical studies comprising 448 patients with over 13,500 observations. Application of this model to independent patient profiles for a given drug-dosing regimen were used to generate the primary aggregate adherence metric, a ratio of observed versus expected plasma exposures at steady-state. Although the metric is capable of comparing relative adherence across groups, simulations showed that the metric is not sufficiently sensitive as an individual diagnostic in all cases. There were no trends observed between results from calculated aggregate adherence metrics and total scores from MMAS8 in a single-visit clinical trial of 47 patients with bipolar 1 disorder or schizophrenia who were on stable doses of aripiprazole, although a strong association was observed for one MMAS8 question. The range of the metric calculated for patients was between 0.16 and 3.15. The described approach of a novel “reverse” application of population PK to quantify relative adherence with an aggregate measure may be influential for both clinical and pharmacometric communities.

The effect of malnutrition on the pharmacokinetics and virologic outcomes of lopinavir, efavirenz and nevirapine in food insecure HIV-infected children in Tororo, Uganda

BACKGROUND

Malnutrition may impact the pharmacokinetics (PKs) of antiretroviral medications and virologic responses in HIV-infected children. The authors therefore evaluated the PK of nevirapine (NVP), efavirenz (EFV) and lopinavir (LPV) in associations with nutritional status in a cohort of HIV-infected Ugandan children.

METHODS

Sparse dried blood spot samples from Ugandan children were used to estimate plasma concentrations. Historical PK data from children from 3 resource-rich countries (RRC) were utilized to develop the PK models.

RESULTS

Concentrations in 330 dried blood spot from 163 Ugandan children aged 0.7-7 years were analyzed in reference to plasma PK data (1189 samples) from 204 children from RRC aged 0.5-12 years. Among Ugandan children, 48% was malnourished (underweight, thin or stunted). Compared to RRC, Ugandan children exhibited reduced bioavailability of EFV and LPV; 11% (P=0.045) and 18% (P=0.008), respectively. In contrast, NVP bioavailability was 46% higher in Ugandan children (P<0.001) with a trend toward greater bioavailability when malnourished. Children receiving LPV, EFV or NVP had comparable risk of virologic failure. Among children on NVP, low height and weight for age Z scores were associated with reduced risk of virologic failure (P=0.034, P=0.068, respectively).

CONCLUSIONS

Ugandan children demonstrated lower EFV and LPV and higher NVP exposure compared to children in RRC, perhaps reflecting the consequence of malnutrition on bioavailability. In children receiving NVP, the relation between exposure, malnutrition and outcome turned out to be marginally significant. Further investigations are warranted using more intensive PK measurements and adequate adherence assessments, to further assess causes of virologic failure in Ugandan children.

Projected inhibition of platelet aggregation with ticagrelor twice daily vs. clopidogrel once daily based on patient adherence data (the TWICE project)

AIM

Twice daily dosing is often perceived as inferior to once daily dosing due to a higher likelihood of missing a dose. However, more important is the extent to which drug action is maintained when doses are delayed or missed. We compared the estimated inhibition of platelet aggregation (eIPA) for ticagrelor twice daily and clopidogrel once daily, based on their pharmacokinetic/ pharmacodynamic relationships and patient dosing history data.

METHODS

Drug dosing histories of 5014 patients prescribed cardiovascular medications (primarily antihypertensive medicines) were extracted from an electronically compiled dosing history database. eIPA levels were simulated for 677 twice daily and 677 once daily dosing histories over a 30 day period, based on published onset/offset models for ticagrelor and clopidogrel IPA characteristics.

RESULTS

While many patients treated twice daily missed at least one dose in 30 days, only 25.7% missed two consecutive doses. By comparison, 46.8% of patients treated once daily missed at least one dose. Simulations based on patient adherence over time showed that the average mean eIPA for ticagrelor twice daily remained significantly higher than for clopidogrel once daily (81.1% vs. 55.0%, P < 0.001). Ticagrelor twice daily patients had an eIPA below 10% for 0.20% of the 30 day period compared with 2.05% for clopidogrel once daily (P = 0.0001).

CONCLUSIONS

The projected level of platelet inhibition remained higher for ticagrelor twice daily than clopidogrel once daily, mainly due to the higher eIPA level achieved with ticagrelor and the relatively low likelihood of missing two consecutive twice daily doses. This modelling and simulation study suggests a therapeutic benefit of ticagrelor over clopidogrel when taking into account the most common dosing omissions.

Population pharmacokinetics of tenofovir and tenofovir-diphosphate in healthy women

The objective of this analysis was to develop and qualify a population pharmacokinetic model describing plasma tenofovir (TFV) concentrations and tenofovir‐diphosphate (TFV‐DP) concentrations in peripheral blood mononuclear cell (PBMC) in healthy women volunteers from the MTN‐001 clinical trial, an open label 3‐way crossover study of oral tenofovir disoproxil fumarate 300 mg tablet, TFV 1% vaginal gel, or both. TFV pharmacokinetics were best described by a 2‐compartment, first‐order absorption/elimination model with absorption lag time. TFV was linked to PBMC TFV‐DP by first‐order uptake with first‐order elimination. An adherence adjustment was included to account for nonadherence by explicitly modeling a bioavailability parameter on the previous day's dose. The final model included weight as a covariate on central compartment volume (V_c) with estimates as follows: absorption rate constant (Ka) 9.79 h⁻¹, absorption lag time 0.5 hours, V_c 385.71–2.16*(73‐WT(kg)), and apparent TFV clearance of 56.7 L/h ((K20 + K24)*V_c). TFV‐DP's half‐life was 53.3 hours. All diagnostic plots and bootstrap confidence intervals were acceptable. Model validation was conducted using simulations compared to data from the MTN‐001 oral + vaginal period and other clinical trial data. The resulting model closely predicted the disposition of TFV and TFV‐DP when compared to healthy participant data from another clinical trial.

Sex differences in atazanavir pharmacokinetics and associations with time to clinical events: AIDS Clinical Trials Group Study A5202

OBJECTIVES

It is uncertain whether HIV-1 antiretroviral exposure and clinical response varies between males and females or different race/ethnic groups. We describe ritonavir-enhanced atazanavir pharmacokinetics in relation to virological failure, safety and tolerability in treatment-naive individuals to investigate potential differences.

METHODS

Plasma samples were collected from participants in AIDS Clinical Trials Group Study A5202 for measurement of antiretroviral concentrations. Individual estimates of apparent oral clearance of atazanavir (L/h) were calculated from a one-compartment model and divided into tertiles as slow (<7), middle (7 to <9; reference group) and fast (≥9). Associations between atazanavir clearance and clinical outcomes were estimated with a hazard ratio (HR) from Cox proportional hazards models. Interactions between atazanavir clearance and sex, race/ethnicity and NRTIs were investigated for each of the outcomes.

RESULTS

Among 786 participants, average atazanavir clearance was slower in females (n = 131) than males (n = 655). Atazanavir clearance was associated with time to virological failure (P = 0.053) and this relationship differed significantly by sex (P = 0.003). Females in the fast atazanavir clearance group had shorter time to virological failure (HR 3.49; 95% CI 1.24-9.84) compared with the middle (reference) atazanavir clearance group. Among males, the slow atazanavir clearance group had a higher risk of virological failure (HR 2.10; 95% CI 1.16-3.77).

CONCLUSIONS

Atazanavir clearance differed by sex. Females with fast clearance and males with slow clearance had increased risk of virological failure.

Relative contributions of cytochrome CYP3A4 versus CYP3A5 for CYP3A-cleared drugs assessed in vitro using a CYP3A4-selective inactivator (CYP3cide)

Metabolism by cytochrome P4503A (CYP3A) is the most prevalent clearance pathway for drugs. Designation of metabolism by CYP3A commonly refers to the potential contribution by one or both of two enzymes, CYP3A4 and CYP3A5. The metabolic turnover of 32 drugs known to be largely metabolized by CYP3A was examined in human liver microsomes (HLMs) from CYP3A5 expressers (*1/*1 genotype) and nonexpressers (*3/*3 genotype) in the presence and absence of ketoconazole and CYP3cide (a selective CYP3A4 inactivator) to calculate the contribution of CYP3A5 to metabolism. Drugs with the highest contribution of CYP3A5 included atazanavir, vincristine, midazolam, vardenafil, otenabant, verapamil, and tacrolimus, whereas 17 of the 32 tested showed negligible CYP3A5 contribution. For specific reactions in HLMs from *1/*1 donors, CYP3A5 contributes 55% and 44% to midazolam 1'- and 4-hydroxylation, 16% to testosterone 6β-hydroxylation, 56% and 19% to alprazolam 1'- and 4-hydroxylation, 10% to tamoxifen N-demethylation, and 58% to atazanavir p-hydroxylation. Comparison of the in vitro observations to clinical pharmacokinetic data showed only a weak relationship between estimated contribution by CYP3A5 and impact of CYP3A5 genotype on oral clearance, in large part because of the scatter in clinical data and the low numbers of study subjects used in CYP3A5 pharmacogenetics studies. These data should be useful in guiding which drugs should be evaluated for differences in pharmacokinetics and metabolism between subjects expressing CYP3A5 and those who do not express this enzyme.

What puts heart failure patients at risk for poor medication adherence?

BACKGROUND

Medication nonadherence is a major cause of hospitalization in patients with heart failure (HF), which contributes enormously to health care costs. We previously found, using the World Health Organization adherence dimensions, that condition and patient level factors predicted nonadherence in HF. In this study, we assessed a wider variety of condition and patient factors and interactions to improve our ability to identify those at risk for hospitalization.

MATERIALS AND METHODS

Medication adherence was measured electronically over the course of 6 months, using the Medication Event Monitoring System (MEMS). A total of 242 HF patients completed the study, and usable MEMS data were available for 218 (90.1%). Participants were primarily white (68.3%), male (64.2%), and retired (44.5%). Education ranged from 8-29 years (mean, 14.0 years; standard deviation, 2.9 years). Ages ranged from 30-89 years (mean, 62.8 years; standard deviation, 11.6 years). Analyses used adaptive methods based on heuristic searches controlled by cross-validation scores. First, individual patient adherence patterns over time were used to categorize patients in poor versus better adherence types. Then, risk factors for poor adherence were identified. Finally, an effective model for predicting poor adherence was identified based on identified risk factors and possible pairwise interactions between them.

RESULTS

A total of 63 (28.9%) patients had poor adherence. Three interaction risk factors for poor adherence were identified: a higher number of comorbid conditions with a higher total number of daily medicines, older age with poorer global sleep quality, and fewer months since diagnosis of HF with poorer global sleep quality. Patients had between zero and three risk factors. The odds for poor adherence increased by 2.6 times with a unit increase in the number of risk factors (odds ratio, 2.62; 95% confidence interval, 1.78-3.86; P<0.001).

CONCLUSION

Newly diagnosed, older HF patients with comorbid conditions, polypharmacy, and poor sleep are at risk for poor medication adherence. Interventions addressing these specific barriers are needed.

Estimation of tenofovir's population pharmacokinetic parameters without reliable dosing histories and application to tracing dosing history using simulation strategies

The objectives of this analysis were to develop a population pharmacokinetic model (PPK) for tenofovir without using potentially unreliable patient reported dosing records and to retrace patient dosing history using pharmacokinetic simulations conditioned on protocol design constraints to assess patient adherence. MTN-001 is a multi-center, open label, 3-way cross over study comparing oral, vaginal and combination (oral and vaginal) administration of tenofovir in healthy women. It was reported that self-reported adherence in this study was high (94%), but serum concentrations indicated only 64% of participants used tablets consistently. A method based on superposition was applied to develop the population PPK considering only observable clinic visit dosing information. A two compartment model described the data well and the parameters agree with the literature reported values. Race was not a significant covariate on clearance. Retracing of the dosing history with 3-past dose resolution was not successful. Trial simulations with full adherence assumption predict a median Cmin of 68 ng/mL, which is in agreement with literature reports. Non-adherence at 25% resulted in 37-51% reduction in Cmin using one coin and two coin models, respectively. Population analyses should consider some method of correction for non-adherence to avoid biased estimates.

Pharmacokinetics of lopinavir/ritonavir and efavirenz in food insecure HIV-infected pregnant and breastfeeding women in Tororo, Uganda

Pregnancy and food insecurity may impact antiretroviral (ART) pharmacokinetics (PK), adherence and response. We sought to quantify and characterize the PK of lopinavir/ritonavir (LPV/r) and efavirenz (EFV) by pregnancy and nutritional status among HIV-infected women in Tororo, Uganda. In 2011, 62/225 ante-partum/post-partum single dried blood spot samples DBS and 43 post-partum hair samples for LPV/r were derived from 116 women, 51/194 ante-/post-partum DBS and 53 post-partum hair samples for EFV from 105 women. Eighty percent of Ugandan participants were severely food insecure, 26% lost weight ante-partum, and median BMI post-partum was only 20.2 kg/m(2) . Rich PK-data of normally nourished (pregnant) women and healthy Ugandans established prior information. Overall, drug exposure was reduced (LPV -33%, EFV -15%, ritonavir -17%) compared to well-nourished controls (P < 0.001), attributable to decreased bioavailability. Pregnancy increased LPV/r clearance 68% (P < 0.001), whereas EFV clearance remained unchanged. Hair concentrations correlated with plasma-exposure (P < 0.001), explaining 29% PK-variability. In conclusion, pregnancy and food insecurity were associated with lower ART exposures in this cohort of predominantly underweight women, compared to well-nourished women. Much variability in plasma-exposure was quantified using hair concentrations. Addressing malnutrition as well as ART-PK in this setting should be a priority.

Dynamical models of biomarkers and clinical progression for personalized medicine: the HIV context

Mechanistic models, based on ordinary differential equation systems, can exhibit very good predictive abilities that will be useful to build treatment monitoring strategies. In this review, we present the potential and the limitations of such models for guiding treatment (monitoring and optimizing) in HIV-infected patients. In the context of antiretroviral therapy, several biological processes should be considered in addition to the interaction between viruses and the host immune system: the mechanisms of action of the drugs, their pharmacokinetics and pharmacodynamics, as well as the viral and host characteristics. Another important aspect to take into account is clinical progression, although its implementation in such modelling approaches is not easy. Finally, the control theory and the use of intrinsic properties of mechanistic models make them very relevant for dynamic treatment adaptation. Their implementation would nevertheless require their evaluation through clinical trials.

Clinical pharmacokinetics of antiretroviral drugs in older persons

INTRODUCTION

Combination antiretroviral therapy has enabled HIV-infected persons to reach older ages in high numbers. Hepatic and renal changes that normally occur with advancing age occur earlier and with higher incidence in HIV-infected individuals. A limited number of prospective controlled studies have demonstrated small reductions (17 to 41%) in lopinavir, atazanavir and lamivudine clearance in older versus younger adults. A much larger number of retrospective studies in adults (age range ∼ 20 to 60 years), including all antiretroviral drugs, have evaluated age as a covariate for pharmacokinetics. Most studies did not detect substantial associations between drug exposures and age.

AREAS COVERED

This review summarizes antiretroviral drug pharmacokinetics in older persons. The authors review articles from PubMed (search terms: elderly, antiretroviral, pharmacokinetics) in addition to the bibliographies of those selected.

EXPERT OPINION

The evidence to date does not support major pharmacokinetic changes in adults between ∼ 20 and 60 years of age. However, additional prospective, well-controlled studies are needed in more persons > 60 years, including those with frailty and comorbidities, with assessment of unbound drug clearance, and incorporation of adherence, pharmacogenetics and concomitant medications. Until then, guidelines for drug-drug interactions and dosing in renal and hepatic impairment should be followed in older HIV-infected individuals.

Adherence profiles and therapeutic responses of treatment-naive HIV-infected patients starting boosted atazanavir-based therapy in the ANRS 134-COPHAR 3 trial

The adherence profile of HIV-infected patients predicts the therapeutic outcome, in particular during the early phase of antiretroviral therapy (ART). We conducted a prospective observational multicenter trial monitoring adherence and virological and immunological parameters over the initial 6 months of treatment. Thirty-five subjects were starting a treatment regimen including atazanavir, ritonavir, and emtricitabine-tenofovir. Adherence was assessed using self-completed questionnaires, announced pill counts, and the medication event monitoring system (MEMS) for each drug. Three MEMS measures were defined: the percentages of doses taken, days with the correct dosing, and doses taken on time (± 3 h). Dynamic virological suppression (DVS) was defined as a reduction in the plasma HIV-RNA level of >1 log10 per month or <40 copies/ml. The cumulative treatment time was 5,526 days. A high level of adherence was observed. The MEMS-defined adherence for correct dosing (-0.68% per 4-week period, P < 0.03) and timing compliance (-1.60% per 4-week period, P < 0.003) decreased significantly over time. The MEMS-defined adherence data were concordant with the pill counts during the trial but not with the data from the questionnaires. The median [range] percentages of doses taken (100% [50 to 102]), days with the correct dosing (95% [41 to 100]), and doses taken on time (86% [32 to 100]) were significantly associated with DVS in separate models. Among these three measures, the percentage of doses taken on time had the greatest ability to predict DVS. Timing compliance should be supported to optimize DVS during the early phase of treatment by once-daily boosted protease inhibitor-based ART. (This study has been registered at ClinicalTrials.gov under registration no. NCT00528060.).

External validation of the bilirubin-atazanavir nomogram for assessment of atazanavir plasma exposure in HIV-1-infected patients

Atazanavir increases plasma bilirubin levels in a concentration-dependent manner. Due to less costly and readily available assays, bilirubin has been proposed as a marker of atazanavir exposure. In this work, a previously developed nomogram for detection of suboptimal atazanavir exposure is validated against external patient populations. The bilirubin nomogram was validated against 311 matching bilirubin and atazanavir samples from 166 HIV-1-infected Norwegian, French, and Italian patients on a ritonavir-boosted regimen. In addition, the nomogram was evaluated in 56 Italian patients on an unboosted regimen. The predictive properties of the nomogram were validated against observed atazanavir plasma concentrations. The use of the nomogram to detect non-adherence was also investigated by simulation. The bilirubin nomogram predicted suboptimal exposure in the patient populations on a ritonavir-boosted regimen with a negative predictive value of 97% (95% CI 95–100). The bilirubin nomogram and monitoring of atazanavir concentrations had similar predictive properties for detecting non-adherence based on simulations. Although both methods performed adequately during a period of non-adherence, they had lower predictive power to detect past non-adherence episodes. Using the bilirubin nomogram for detection of suboptimal atazanavir exposure in patients on a ritonavir-boosted regimen is a rapid and cost-effective alternative to routine measurements of the actual atazanavir exposure in plasma. Its application may be useful in clinical settings if atazanavir concentrations are not available.