Intracellular accumulation of atazanavir/ritonavir according to plasma concentrations and OATP1B1, ABCB1 and PXR genetic polymorphisms

Role of Artificial Intelligence and Personalized Medicine in Enhancing HIV Management and Treatment Outcomes

The integration of artificial intelligence and personalized medicine is transforming HIV management by enhancing diagnostics, treatment optimization, and disease monitoring. Advances in machine learning, deep neural networks, and multi-omics data analysis enable precise prognostication, tailored antiretroviral therapy, and early detection of drug resistance. AI-driven models analyze vast genomic, proteomic, and clinical datasets to refine treatment strategies, predict disease progression, and pre-empt therapy failures. Additionally, AI-powered diagnostic tools, including deep learning imaging and natural language processing, improve screening accuracy, particularly in resource-limited settings. Despite these innovations, challenges such as data privacy, algorithmic bias, and the need for clinical validation remain. Successful integration of AI into HIV care requires robust regulatory frameworks, interdisciplinary collaboration, and equitable technology access. This review explores both the potential and limitations of AI in HIV management, emphasizing the need for ethical implementation and expanded research to maximize its impact. AI-driven approaches hold great promise for a more personalized, efficient, and effective future in HIV treatment and care.

Intracellular Penetration of Atazanavir, Ritonavir and Dolutegravir With Concomitant Rifampicin: A Dose Escalation Study

Ritonavir-boosted atazanavir is a victim of drug-drug interaction with rifampicin, a key component of antitubercular treatment. In a recent dose escalation clinical trial, we showed that increasing atazanavir/ritonavir to 300/100 mg b.i.d. compensates for reduced drug exposure in plasma due to rifampicin, but the intracellular effects remained unexplored. This sub-study investigated the intracellular penetration of atazanavir/ritonavir and dolutegravir into peripheral blood mononuclear cells (PBMC). Twenty-six healthy volunteers living with HIV, virologically suppressed, and taking atazanavir/ritonavir containing regimens were enrolled. The trial consisted of four sequential periods: PK1, participants were on atazanavir/ritonavir 300/100 mg q.d.; at PK2, rifampicin 600 mg q.d. and dolutegravir 50 mg b.i.d. were added (2 weeks); at PK3, atazanavir/ritonavir dose was increased to 300/100 mg b.i.d. (1 week); at PK4, rifampicin dose was doubled (1 week). Atazanavir, ritonavir, and dolutegravir were quantified in plasma and PBMC using LC-MS/MS methods to evaluate steady-state concentrations at the end of each period. Atazanavir/ritonavir dose escalation successfully restored intracellular concentrations comparable to those observed without rifampicin, with a geometric mean ratio of 0.99 (CI90 0.72-1.41) for atazanavir at PK3 compared with PK1. The intracellular concentration of dolutegravir increased significantly with atazanavir/ritonavir dose escalation, similar to plasma. Finally, further, increasing the rifampicin dose did not show an additional impact on atazanavir/ritonavir concentrations in PBMC. The study confirms that increasing the ATV/r dose can be an effective strategy for compensating rifampicin effects even at the intracellular level, supporting its use in clinical settings.

The Impact of Organic Anion-Transporting Polypeptide (OATP) Variants on the Side Effects of Direct-Acting Antivirals in Hepatitis C Patients

Background Organic anion-transporting polypeptides (OATPs) are responsible for the cellular uptake of a broad range of endogenous compounds and xenobiotics in multiple tissues. The aim of our study was to determine whether variations in OATP1B1 and OATP1B3 affect the side effects experienced by hepatitis C patients treated with direct-acting antivirals (DAAs). Methods This study included 199 hepatitis C patients treated with DAAs. Ledipasvir/sofosbuvir or ombitasvir/paritaprevir/ritonavir ± dasabuvir and 162 control individuals without hepatitis C. Treatment-related side effects were recorded. The OATP1B1 gene variations c.388A>G and c.521T>C and the OATP1B3 gene variations c.334T>G and c.699G>A were analyzed via the polymerase chain reaction-restriction fragment length polymorphism method. Allele/genotype combinations of OATP1B1 and OATP1B3 haplotypes were evaluated. Results Side effects were observed in 53 (26.6%) of 199 hepatitis C patients. There were skin mucosal lesions in 19 patients (36%), fatigue in 18 patients (34%), pruritus in 11 patients (20.5%), and other in five patients (9.5%). There was a significant relationship between the c.334T>G variant and side effects (p = 0.030). The frequency distribution of the c.334T>G variant was in Hardy-Weinberg equilibrium. The frequencies of the patient group and the control group were 65.3% and 63%, respectively. We found a significant difference between the patient and control groups in terms of the haplotype ratios of c.388A>G and c.521T>C (p = 0.036). Conclusions We found a significant relationship between the c.334T>G variant in OATP1B3 and DAA-related side effects in hepatitis C patients.

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.

Pregnane X Receptor (PXR) Polymorphisms and Cancer Treatment

Pregnane X Receptor (PXR) belongs to the nuclear receptors' superfamily and mainly functions as a xenobiotic sensor activated by a variety of ligands. PXR is widely expressed in normal and malignant tissues. Drug metabolizing enzymes and transporters are also under PXR's regulation. Antineoplastic agents are of particular interest since cancer patients are characterized by significant intra-variability to treatment response and severe toxicities. Various PXR polymorphisms may alter the function of the protein and are linked with significant effects on the pharmacokinetics of chemotherapeutic agents and clinical outcome variability. The purpose of this review is to summarize the roles of PXR polymorphisms in the metabolism and pharmacokinetics of chemotherapeutic drugs. It is also expected that this review will highlight the importance of PXR polymorphisms in selection of chemotherapy, prediction of adverse effects and personalized medicine.

ABCB1, ABCG2, ABCC1, ABCC2, and ABCC3 drug transporter polymorphisms and their impact on drug bioavailability: what is our current understanding?

INTRODUCTION

Interindividual differences in drug response are a frequent clinical challenge partly due to variation in pharmacokinetics. ATP-binding cassette (ABC) transporters are crucial determinants of drug disposition. They are subject of gene regulation and drug-interaction; however, it is still under debate to which extend genetic variants in these transporters contribute to interindividual variability of a wide range of drugs.

AREAS COVERED

This review discusses the current literature on the impact of genetic variants in ABCB1, ABCG2 as well as ABCC1, ABCC2, and ABCC3 on pharmacokinetics and drug response. The aim was to evaluate if results from recent studies would increase the evidence for potential clinically relevant pharmacogenetic effects.

EXPERT OPINION

Although enormous efforts have been made to investigate effects of ABC transporter genotypes on drug pharmacokinetics and response, the majority of studies showed only weak if any associations. Despite few unique results, studies mostly failed to confirm earlier findings or still remained inconsistent. The impact of genetic variants on drug bioavailability is only minor and other factors regulating the transporter expression and function seem to be more critical. In our opinion, the findings on the so far investigated genetic variants in ABC efflux transporters are not suitable as predictive biomarkers.

Antiretroviral Treatment and Antihypertensive Therapy

The presence of hypertension among the population with human immunodeficiency virus (HIV) has become a new threat to the health and well-being of people living with this disease, in particular, among those who received antiretroviral therapy. The estimated prevalence of high blood pressure in HIV-infected patients is significantly higher than the rate observed in HIV-uninfected subjects. The approach to the HIV-positive patient requires the assessment of individual cardiovascular risk and its consideration when designing the individualized target. On the other hand, the numerous pharmacological interactions of antiretroviral (ARV) drugs are essential elements to take into account. Serum levels of any kind of antihypertensive drugs may be influenced by the coadministration of protease inhibitors, non-nucleoside reverse transcriptase inhibitor, or other antiretroviral. Similarly, plasma concentrations of antiretroviral drugs can be increased by the concomitant use of calcium channel blockers or diuretics. In this regard, the treatment of high blood pressure in HIV patients should be preferentially based on ACE inhibitors or thiazide/thiazide-like diuretics or their combination.

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.

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.

HIV Integrase Inhibitor Pharmacogenetics: An Exploratory Study

BACKGROUND AND OBJECTIVES

Integrase strand transfer inhibitors (INSTIs), dolutegravir, elvitegravir, and raltegravir, have become integral in the treatment of HIV, with close monitoring of continued efficacy and tolerability. As side effect occurrence varies among subjects receiving these drugs, we sought to perform an exploratory analysis examining the role of several single-nucleotide polymorphisms (SNPs) on drug concentration changes, selected clinical outcomes, and the occurrence of subject-reported adverse events.

METHODS

Adults (aged ≥ 18 years) receiving INSTI-based regimens for treatment of HIV were recruited and genotyped with an iPLEX ADME PGx Pro v1.0 Panel. Multiple linear or logistic regression with covariates [age, sex, BMI, regimen (in the across-regimen group), regimen duration, and baseline variables (for continuous parameters)] was used to detect significant (p < 0.05) association of selected clinical data with genetic variants within the study population.

RESULTS

In a sample (n = 88) with a median age of 52.5 years (IQR 45.7-57.2) being predominately Caucasian (88.6%) and male (86.4%), this exploratory study discovered several associations between variables and SNPs, when using INSTIs. Abnormal dream occurrence was statistically different (p = 0.028) between regimens. Additionally, several SNPs were found to be associated with adverse event profiles primarily when all regimens were grouped together.

CONCLUSION

The associations found in this study point to a need for further assessment, within the population living with HIV, of factors contributing to unfavorable subject outcomes. These exploratory findings require confirmation in larger studies, which then may investigate pharmacogenetic mechanisms.

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.

No difference in effectiveness of treatment simplification to boosted or unboosted atazanavir plus lamivudine in virologically suppressed in HIV-1-infected patients

Background

Simplification strategies of antiretroviral treatment represent effective tools for the reduction of drug-induced toxicity, resistance mutations in case of virological failure and costs.

Objectives

To assess the effectiveness of simplification to atazanavir/ritonavir (ATV_rtv) or unboosted atazanavir (ATV₄₀₀) plus lamivudine, and if low plasma or intracellular ATV C_trough influence virological outcomes.

Methods

Ambispective observational study in patients with undetectable HIV-RNA who were switched to ATV_rtv or ATV₄₀₀ plus lamivudine once daily. Previous virological failures (VF) were allowed if the resistance tests showed major resistance mutation neither to ATV nor to lamivudine. VF was defined as two consecutive plasma HIV-RNA >200 copies/mL. Effectiveness was assessed by intention-to-treat and on-treatment analyses. Plasma and intracellular ATV C_trough were measured by LC-MS/MS.

Result

A total of 246 patients were included. At week 48, the Kaplan–Meier estimation of efficacy within the ATV_rtv and ATV₄₀₀ groups were 85.9% [95% confidence interval, (CI₉₅), 80.3–91.4%] versus 87.6% (CI₉₅, 80.1–94.1%) by intention-to-treat analysis (p = 0.684), and 97.7% (CI₉₅, 95.2–100%) versus 98.8% (CI₉₅, 97.0–100%) by on-treatment analysis (p = 0.546), respectively. Plasma and intracellular C_trough were significantly higher with ATV_rtv than with ATV₄₀₀ (geometric mean (GM), 318.3 vs. 605.9 ng/mL; p = 0.013) and (811.3 vs. 2659.2 ng/mL; p = 0.001), respectively. Only 14 patients had plasma C_trough below the suggested effective concentration for ATV (150 ng/mL). No relationship between plasma or intracellular C_trough and VF or blips were found.

Conclusion

Boosted or unboosted ATV plus lamivudine is effective and safe, and the lower plasma C_trough observed with ATV₄₀₀ do not compromise the effectiveness of these simplification regimens in long-term virologically suppressed HIV-1-infected patients.

Pharmacokinetic Changes during Pregnancy According to Genetic Variants: a Prospective Study in HIV-Infected Patients Receiving Atazanavir-Ritonavir

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.

Intrahepatic Sampling for the Elucidation of Antiviral Clinical Pharmacology

Although the importance of the liver in clinical pharmacology is widely recognized, little is known in humans concerning its function in vivo at the hepatocyte level and how pharmacological functions are altered in the setting of advanced liver disease. Several recent proof-of-principle studies with first-generation DAAs have demonstrated the feasibility of serial liver sampling for pharmacological studies. These studies have begun to describe the liver-to-plasma concentration ratio and how this ratio is altered in the setting of advanced liver disease. These data are particularly relevant to individuals with substance-use disorders because many have advanced liver disease as a consequence of long-standing viral hepatitis infection or continued use of hepatotoxins such as alcohol. Future research should attempt to develop standardized and reproducible methods to assess liver drug concentration, complex drug interactions, and pharmacogenomics in humans to permit elucidation of the clinical pharmacology within the liver.

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.

Genetic variations of the xenoreceptors NR1I2 and NR1I3 and their effect on drug disposition and response variability

NR1I2 (PXR) and NR1I3 (CAR) are nuclear receptors that are classified as xenoreceptors. Upon activation by various xenobiotics, including marketed drugs, they regulate the transcription level of major drug-metabolizing enzymes and transporters and facilitate the elimination of xenobiotics from the body. The modulation of the activity of these two xenoreceptors by various ligands is a major source of pharmacokinetic variability of environmental origin. NR1I2 and NR1I3 genetic polymorphisms can affect the pharmacokinetics and therapeutic response to many drugs, such as irinotecan, tacrolimus and atazanavir. This review provides an overview of NR1I2 and NR1I3 pharmacogenetic studies in various therapeutic fields (oncology, immunomodulation and infectiology) and discusses the implementation of NR1I2 and NR1I3 genetic polymorphism testing in the clinical routine.

Effects of Polymorphisms in NR1H4, NR1I2, SLCO1B1, and ABCG2 on the Pharmacokinetics of Rosuvastatin in Healthy Chinese Volunteers

The nuclear receptors (NR)-farnesoid X receptor (FXR, NR1H4) and pregnane X receptor (PXR, NR1I2)-have important effects on the expression of genes related to the pharmacokinetics (PKs) of rosuvastatin. This study was designed to investigate whether the genetic variants in drug disposition genes (SLCO1B1 and ABCG2) combined with their upstream regulators (NR1H4 and NR1I2) would affect the PKs of rosuvastatin in a Chinese population. Sixty-one healthy male volunteers were enrolled and the plasma concentrations of rosuvastatin were measured using the liquid chromatographic-tandem mass spectrometry/MS method. All subjects were analyzed and grouped according to the genotypes of NR1H4, NR1I2, SLCO1B1, and ABCG2. The exposure of rosuvastatin was higher in subjects carrying the SLCO1B1 521C or ABCG2 421A allele compared with noncarriers. No association was observed of single-nucleotide polymorphisms in NR1H4 or NR1I2 genes with the PKs of rosuvastatin. After adjusting for the 421C>A and 521T>C variants, the Cmax in subjects with NR1I2 63396TT wild type were about 2-fold of those of NR1I2 mutant type (63396CC and CT) (10.7 vs. 20.4 ng/mL, P = 0.023), whereas no significant differences were observed for other parameters. Polymorphisms investigated in the genes of NR1H4 and NR1I2 seemed to play no significant role in the disposition of rosuvastatin.

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.

Role of vitamin D pathway gene polymorphisms on rifampicin plasma and intracellular pharmacokinetics

AIM

We retrospectively evaluate the pharmacogenetic role of single nucleotide polymorphisms involved in rifampicin transport (SLCO1B1, MDR1 and PXR genes) and vitamin D (VDR, CYP24A1 and CYP27B1 genes) metabolism and activity on drug plasma and intracellular concentrations.

PATIENTS & METHODS

Rifampicin C_max and C_trough were measured at weeks 2 and 4 using Ultra-Performance Liquid Chromatography-tandem mass spectroscopy methods. Allelic discrimination was performed by real-time polymerase chain reaction.

RESULTS

Twenty-four patients were enrolled. At week 2, OATP1B1 521TT and CYP27B1 +2838CC/CT considering plasma and BsmIAA for intraperipheral blood mononuclear cells C_max, remained in regression analysis. Concerning week 4, TaqITC/CC and CYP24A1 22776CT/TT were retained in plasma C_max regression model.

CONCLUSION

This study confirms the role of SLCO1B1 and it suggests the involvement of vitamin D pathway gene polymorphisms in rifampicin pharmacokinetics.

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.

Is the unbound concentration of atazanavir of interest in therapeutic drug monitoring?

To date, therapeutic drug monitoring (TDM) is carried out with antiretrovirals and is usually based on total concentrations (C_t ). However, for some patients, TDM does not reflect efficacy or the avoidance of toxicity as is the case for atazanavir (ATV), a HIV protease inhibitor. As the unbound concentration (C_u ) is the pharmacological active form, the aim of the study was to evaluate the value of C_u and the unbound fraction (f_u , f_u = C_u /C_t ) for the TDM of ATV. The variability of C_u and the corresponding f_u of ATV was explored in 43 patients treated with ATV for an average of 13.5 months. C_u was determined by coupling ultrafiltration and liquid chromatography. As ATV is highly bound to alpha-1 acid glycoprotein (AAG), the correlation between f_u and AAG was also evaluated. The viral load was monitored to evaluate the patients' virologic response, while total plasma bilirubin and unconjugated plasma bilirubin were used as biomarkers of ATV toxicity. Median trough C_u and C_t were 37.9 μg/L (Interquartile range (IQR) 20.6-94.9 μg/L) and 628.6 μg/L (IQR 362.7-1078.1 μg/L), respectively. f_u , C_u and C_t showed high variability, but the f_u variability was not correlated with the AAG level. The unbound concentration and fraction were unrelated to the virologic response (P = 0.21 and P = 0.65 for C_u and f_u , respectively) nor to the unconjugated bilirubin (Pearson correlation coefficient (ρ), ρ = 0.22; P = 0.17 for C_u ). Neither total nor unbound concentrations of ATV fully explained hyperbilirubinaemia or virologic failure. From this study, we conclude that unbound ATV did not appear to be more relevant than C_t .

Effects of quercetin on pharmacokinetics of cefprozil in Chinese-Han male volunteers

1. The primary objective of this study was to evaluate the effects of quercetin on the pharmacokinetics of cefprozil. The secondary objective was to evaluate the safety of the combined use of cefprozil and quercetin. 2. An open-label, two-period, crossover phase I trial among 24 Han Chinese male subjects was conducted. Participants were given 500 mg of quercetin orally once daily for 15 d followed by single dose of cefprozil (500 mg) on day 15. Serum concentrations of cefprozil were then measured in all participants on day 15. A 15-d washout period was then assigned after which a 500 mg dose of cefprozil was administered and measured in the serum on day 36. 3. All subjects completed the trial, and no serious adverse events were reported. We measured mean serum concentrations of cefprozil in the presence and absence of quercetin in all participants. The maximum serum concentration of cefprozil in the presence of quercetin was 8.18 ug/ml (95% CI: 7.55-8.81) versus a maximum cefprozil concentration of 8.35 ug/ml (95% CI: 7.51-9.19) in the absence of quercetin. We conclude that the concurrent use of quercetin has no substantial effect on serum concentrations of orally administered cefprozil. 4. Co-administration of quercetin showed no statistically significant effects on the pharmacokinetics of cefprozil in healthy Chinese subjects.

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.

Heme oxygenase-1-derived bilirubin counteracts HIV protease inhibitor-mediated endothelial cell dysfunction

The use of HIV protease inhibitors (PIs) has extended the duration and quality of life for HIV-positive individuals. However there is increasing concern that this antiviral therapy may promote premature cardiovascular disease by impairing endothelial cell (EC) function. In the present study, we investigated the effect of HIV PIs on EC function and determined if the enzyme heme oxygenase (HO-1) influences the biological action of these drugs. We found that three distinct PIs, including ritonavir, atazanavir, and lopinavir, stimulated the expression of HO-1 protein and mRNA. The induction of HO-1 was associated with an increase in NF-E2-related factor-2 (Nrf2) activity and reactive oxygen species (ROS). PIs also stimulated HO-1 promoter activity and this was prevented by mutating the antioxidant responsive element or by overexpressing dominant-negative Nrf2. In addition, the PI-mediated induction of HO-1 was abolished by N-acetyl-l-cysteine and rotenone. Furthermore, PIs blocked EC proliferation and migration and stimulated the expression of intercellular adhesion molecule-1 and the adhesion of monocytes on ECs. Inhibition of HO-1 activity or expression potentiated the anti-proliferative and inflammatory actions of PIs which was reversed by bilirubin but not carbon monoxide. Alternatively, adenovirus-mediated overexpression of HO-1 attenuated the growth-inhibitory and inflammatory effect of PIs. In contrast, blocking HO-1 activity failed to modify the anti-migratory effect of the PIs. Thus, induction of HO-1 via the ROS-Nrf2 pathway in human ECs counteracts the anti-proliferative and inflammatory actions of PIs by generating bilirubin. Therapeutic approaches targeting HO-1 may provide a novel approach in preventing EC dysfunction and vascular disease in HIV-infected patients undergoing antiretroviral therapy.

Antiretroviral drug transporters and metabolic enzymes in human testicular tissue: potential contribution to HIV-1 sanctuary site

OBJECTIVES

The testes are a potential viral sanctuary site for HIV-1 infection. Our study aims to provide insight into the expression and localization of key drug transporters and metabolic enzymes relevant to ART in this tissue compartment.

METHODS

We characterized gene and protein expression of 12 representative drug transporters and two metabolic enzymes in testicular tissue samples obtained from uninfected (n = 8) and virally suppressed HIV-1-infected subjects on ART (n = 5) and quantified antiretroviral drug concentrations in plasma and testicular tissues using LC/MS/MS from HIV-1-infected subjects.

RESULTS

Our data demonstrate that key ABC drug transporters (permeability glycoprotein, multidrug-resistance protein 1, 2 and 4, and breast cancer resistance protein), solute carrier transporters (organic anion transporting polypeptides 1B1 and 2B1, organic anion transporter 1, concentrative nucleoside transporter 1, equilibrative nucleoside transporter 2) and cytochrome P450 metabolic enzymes (CYP3A4 and CYP2D6) previously shown to interact with many commonly used antiretroviral drugs are expressed at the mRNA and protein level in the testes of both subject groups and localize primarily at the blood-testis barrier, with no significant differences between the two groups. Furthermore, we observed that PIs known to be substrates for ATP-binding cassette membrane transporters, displayed variable testicular tissue penetration, with darunavir concentrations falling below therapeutic values. In contrast, the NRTIs emtricitabine, lamivudine and tenofovir displayed favourable tissue penetration, reaching concentrations comparable to plasma levels. We also demonstrated that nuclear receptors, peroxisome proliferator-activated receptors α and γ exhibited higher gene expression in the testicular tissue compared with pregnane X receptor and constitutive androstane receptor, suggesting a potential regulatory pathway governing drug transporter and metabolic enzyme expression in this tissue compartment.

CONCLUSIONS

Our data suggest the testes are a complex pharmacological compartment that can restrict the distribution of certain antiretroviral drugs and potentially contribute to HIV-1 persistence.

Can antiretroviral therapy be tailored to each human immunodeficiency virus-infected individual? Role of pharmacogenomics

Pharmacogenetics refers to the effect of single nucleotide polymorphisms (SNPs) within human genes on drug therapy outcome. Its study might help clinicians to increase the efficacy of antiretroviral drugs by improving their pharmacokinetics and pharmacodynamics and by decreasing their side effects. HLAB*5701 genotyping to avoid the abacavir-associated hypersensitivity reaction (HSR) is a cost-effective diagnostic tool, with a 100% of negative predictive value, and, therefore, it has been included in the guidelines for treatment of human immunodeficiency virus (HIV) infection. HALDRB*0101 associates with nevirapine-induced HSR. CYP2B6 SNPs modify efavirenz plasma levels and their genotyping help decreasing its central nervous system, hepatic and HSR toxicities. Cytokines SNPs might influence the development of drug-associated lipodystrophy. APOA5, APOB, APOC3 and APOE SNPs modify lipids plasma levels and might influence the coronary artery disease risk of HIV-infected individuals receiving antiretroviral therapy. UGT1A1*28 and ABCB1 (MDR1) 3435C > T SNPs modify atazanavir plasma levels and enhance hyperbilirubinemia. Much more effort needs to be still devoted to complete large prospective studies with multiple SNPs genotyping in order to reveal more clues about the role played by host genetics in antiretroviral drug efficacy and toxicity.

UPLC-MS/MS method with automated on-line SPE for the isomer-specific quantification of the first-generation anti-HCV protease inhibitors in peripheral blood mononuclear cells

HCV infection affects over 170 million people worldwide. The current standard for treatment of genotype 1 infection is the association of the first generation protease inhibitors boceprevir or telaprevir to ribavirin and peginterferon α. Although the response rate has been improved with these new drugs, some pharmacokinetic/pharmacodinamic issues emerged in the past years. To date, some analytical methods are available for the quantification of these drugs in plasma; however, the real active concentrations of the two drugs are those in hepatocytes. Being the withdrawal of hepatocytes too invasive, in this work we aimed to develop and validate a chromatographic method coupled with tandem mass spectrometry capable of quantifying boceprevir and telaprevir isomers in peripheral blood mononuclear cells, used as an "in-vivo" cellular model of compartmentalization. The method used an on-line solid phase extraction protocol based on the new OSM(®) platform and was fully validated following FDA guidelines. This method showed mean intra- and inter-day inaccuracy and imprecision both lower than 15%, high and stable recovery and contained matrix effect, with a run time of 6min, comprehensive of SPE extraction. The method was then applied on 35 real samples from patients treated with boceprevir or telaprevir, with good analytical performances, thus assessing its eligibility for a possible future routine use. Peculiar pharmacokinetic data have been observed, suggesting the usefulness of investigating intracellular pharmacokinetics of these drugs. Further studies will be required to test the correlation of intracellular concentrations with effectiveness and toxicity of triple therapy.

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.

A UPLC-MS-MS method for the simultaneous quantification of first-line antituberculars in plasma and in PBMCs

OBJECTIVES

TB is currently the second cause of death among patients affected with infectious diseases. Quantification of drug levels in plasma and in cells where Mycobacterium tuberculosis persists and grows may be useful in understanding the appropriateness of dosage regimens. We report a new and fully validated chromatographic method to quantify first-line antituberculars in plasma and PBMCs. The method was used for plasma and cell quantification of antituberculars in patients undergoing treatment with standard oral therapy.

METHODS

Ethambutol, isoniazid, pyrazinamide and rifampicin were extracted from plasma and PBMCs using two separate and optimized procedures; analysis was performed using UPLC coupled with a mass-mass detector system (UPLC-MS-MS). Antitubercular levels in patients were assayed at the end of the dosing interval (C trough) and 2 h post-dose (C max).

RESULTS

The method was accurate and precise. Recovery and the matrix effect were reproducible. While rifampicin intracellular concentrations were similar to plasma values (median intra-PBMC C max = 7503 ng/mL versus median plasma C max = 6505 ng/mL), isoniazid and pyrazinamide intracellular concentrations were lower than plasma values (median intra-PBMC C max = 12 ng/mL versus median plasma C max = 3258 ng/mL for isoniazid and median intra-PBMC C max = 2364 ng/mL versus median plasma C max = 26 988 ng/mL for pyrazinamide) and ethambutol intracellular concentrations were significantly higher than plasma values (median intra-PBMC C max = 73 334 ng/mL versus median plasma C max = 2244 ng/mL).

CONCLUSIONS

The method was suitable for both therapeutic drug monitoring and for pharmacokinetic analysis. Should the clinical usefulness of measuring antitubercular drug intracellular concentrations be confirmed, this method could be useful to enhance the clinical application of intra-PBMC evaluation.

Intestinal and hepatic drug transporters: pharmacokinetic, pathophysiological, and pharmacogenetic roles

The efficacy and safety of pharmacotherapies are determined by the complex processes involved in the interactions between drugs with the human body, including pharmacokinetic aspects. Among pharmacokinetic factors, it has been recognized that drug transporters play critical roles for absorption, distribution and excretion of drugs, regulating the membrane transport of drugs. The vast amounts of information on drug transporters collected in the past 20 years have been organized according to biochemical, molecular, genetic, and clinical analyses. Novel technologies, public databases, and regulatory guidelines have advanced the use of such information in drug development and clinical practice. In this review, we selected some clinically important drug transporters expressed in the intestine and liver, and introduced the research history and current knowledge of their pharmacokinetic, pathophysiological, and pharmacogenetic implications.

Establishment of an expression platform of OATP1B1 388GG and 521CC genetic polymorphism and the therapeutic effect of tamoxifen in MCF-7 cells

The present study was designed to evaluate the gene polymorphisms of organic anion transporting polypeptide 1B1 (OATP1B1) in predicting the therapeutic efficacy of tamoxifen (TAM) for MCF-7. Established plasmids OATP1Bl wild-type 388GG and 521CC were transfected into MCF-7 cells and used to determine whether the gene polymorphisms affected the therapeutic efficacy of TAM for MCF-7. The established plasmids pcDNA3.1(-)-OATP1B1 wild-type 388GG and 521CC were digested by restriction enzymes and analyzed by gene sequencing. The gene polymorphisms of OATP1Bl in MCF-7 breast cancer cells were examined by RT-PCR and western blot analysis. The results showed that the mutations of OATP1B1 388GG and 521CC led to a decrease of the inhibition and apoptotic rates of MCF-7 cells, albeit not significantly compared to the OATP1B1 group. The G₀/G₁ phase length ratio was reduced, and the S and G₂M phases were increased in the OATP1B1 388GG and 521CC groups, although not significantly compared to the OATP1B1 group. The mutations of OATP1B1 388GG and 521CC inhibited the activity of OATP1B1 protein, restrained the turnover capacity of OATP1B1 and reduced the entrance of TAM into MCF-7 cells, resulting in weakened efficacy of TAM in the treatment of breast cancer.

An UPLC-MS/MS method coupled with automated on-line SPE for quantification of tacrolimus in peripheral blood mononuclear cells

BACKGROUND

Tacrolimus is an immunosuppressor used to treat patients undergoing liver transplantation. TDM of hematic tacrolimus by liquid chromatography became standard practice, but it does not necessarily reflect its concentration at its active site. Our aim was to validate a new method for tacrolimus quantification into target cells (peripheral blood mononuclear cells, PBMCs) and testing it on 100 real samples from 37 pediatric patients.

METHODS

PBMCs were collected using cell-preparation-tubes; cells number and MCV were evaluated. Tacrolimus was quantified using UPLC-MS/MS coupled with a new automated on-line SPE platform. Chromatographic run was performed on an Acquity UPLC(®) BEH C18 1.7 μm (2.1 mm × 50 mm) column for 5 min, with a gradient of water and methanol (both with 2 mM/L ammonium acetate and 1 mL/L formic acid). XBridge(®) C8 10 μm (1 mm × 10 mm) SPE cartridges were used. The internal standard was 6,7-dimethyl-2,3-di(2-pyridyl)quinoxaline.

RESULTS

Full validation following FDA guidelines was performed: the method showed high sensitivity and specificity (LLOQ of 0.010 ng; LLOD of 0.005 ng). Intra- and inter-day imprecision and inaccuracy were <15%. A positive and stable matrix effect was observed, with a good recovery for tacrolimus. All drug amounts in real samples resulted within the calibration range and calibration curves were linear (r(2)=0.998). Concentrations from each patient were standardized using their evaluated MCV: intra-PBMCs concentration was meanly 12.7 times higher than the hematic one.

CONCLUSION

This method might be eligible and useful for a clinical routine use, giving more reliable data on drug concentration at the active site.