Influence of ABCC2 and ABCC4 polymorphisms on tenofovir plasma concentrations in Thai HIV-infected patients

Single-nucleotide polymorphisms in ABC drug transporters alter expression and circulating tenofovir in healthy South African women exposed to pre-exposure prophylaxis

Aim: We investigated if single-nucleotide polymorphisms (SNPs) in ATP-binding cassette (ABC) drug transporters alter gene expression and tenofovir disposition in South African women taking Truvada® for HIV prevention. Materials & methods: In 393 women, real-time PCR was used to determine the associations between six SNPs in ABC transporter genes, mRNA expression and circulating-tenofovir. Results: Univariable and multivariable analyses showed that CT and TT relative to CC genotypes for the ABCC4(3463C/T) SNP had significantly higher tenofovir levels. In contrast, the AA genotype for the ABCC4(4976A/G) SNP showed significantly less tenofovir, while mRNA expression was increased. Conclusion: SNPs in the ABCC4 gene may differentially affect gene expression and circulating tenofovir. Their impact may inform on low pre-exposure prophylaxis efficacy and discern effective drugs in clinical trials of African women enriched for certain genotypes.

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.

Fluorescence-based methods for studying activity and drug-drug interactions of hepatic solute carrier and ATP binding cassette proteins involved in ADME-Tox

In humans, approximately 70% of drugs are eliminated through the liver. This process is governed by the concerted action of membrane transporters and metabolic enzymes. Transporters mediating hepatocellular uptake of drugs belong to the SLC (Solute carrier) superfamily of transporters. Drug efflux either toward the portal vein or into the bile is mainly mediated by active transporters of the ABC (ATP Binding Cassette) family. Alteration in the function and/or expression of liver transporters due to mutations, disease conditions, or co-administration of drugs or food components can result in altered pharmacokinetics. On the other hand, drugs or food components interacting with liver transporters may also interfere with liver function (e.g., bile acid homeostasis) and may even cause liver toxicity. Accordingly, certain transporters of the liver should be investigated already at an early stage of drug development. Most frequently radioactive probes are applied in these drug-transporter interaction tests. However, fluorescent probes are cost-effective and sensitive alternatives to radioligands, and are gaining wider application in drug-transporter interaction tests. In our review, we summarize our current understanding about hepatocyte ABC and SLC transporters affected by drug interactions. We provide an update of the available fluorescent and fluorogenic/activable probes applicable in in vitro or in vivo testing of these ABC and SLC transporters, including near-infrared transporter probes especially suitable for in vivo imaging. Furthermore, our review gives a comprehensive overview of the available fluorescence-based methods, not directly relying on the transport of the probe, suitable for the investigation of hepatic ABC or SLC-type drug transporters.

Antiretroviral Levels in the Cerebrospinal Fluid: The Effect of Inflammation and Genetic Variants

Neurocognitive impairments are common in people living with HIV. Some conditions, such as chronic inflammation, astrocyte infection and an impaired blood-brain barrier (BBBi), along with host genetic variants in transporter genes, may affect antiretroviral (ARV) exposure in the cerebrospinal fluid (CSF). The aim of this study was to evaluate ARV CSF penetration according to compartmental inflammation, BBB permeability and single-nucleotide polymorphisms (SNPs) in drug transporter encoding genes. CSF neopterin (ELISA), plasma and CSF ARV concentrations (HPLC) and host genetic variants in ABCC2, HNF4α, SLCO1A2 and SLC22A6 (real-time PCR) were measured. Bi- and multivariate analyses were performed for single ARV and classes. We included 259 participants providing 405 paired plasma and CSF samples. CSF/plasma ratios (CPR) showed an increase for NRTIs and nevirapine with low penetrations for the majority of ARVs. At bi-variate analysis, several associations, including the effect of BBBi (emtricitabine, raltegravir), age (zidovudine and darunavir), and high CSF neopterin (NRTIs and border-line for PIs) were suggested. An association was found between genetic variants and integrase strand transfer (ABCC2 and HNF4α), non-nucleoside reverse transcriptase inhibitors (SLCO1A2), and protease inhibitors (SLC22A6). At multivariate analysis age, gender, BMI, and altered BBB were independent predictors of nucleoside reverse transcriptase CSF concentrations; age (for protease inhibitors) and body mass index and altered BBB (integrase strand transfer inhibitors) were also associated with ARV CSF exposure. We describe factors associated with CSF concentrations, showing that demographic, BBB integrity and, partially, genetic factors may be predictors of drug passage in the central nervous system.

Effect of polymorphisms in drug metabolism and transportation on plasma concentration of atorvastatin and its metabolites in patients with chronic kidney disease

Dyslipidemia due to renal insufficiency is a common complication in patients with chronic kidney diseases (CKD), and a major risk factor for the development of cardiovascular events. Atorvastatin (AT) is mainly used in the treatment of dyslipidemia in patients with CKD. However, response to the atorvastatin varies inter-individually in clinical applications. We examined the association between polymorphisms in genes involved in drug metabolism and transport, and plasma concentrations of atorvastatin and its metabolites (2-hydroxy atorvastatin (2-AT), 2-hydroxy atorvastatin lactone (2-ATL), 4-hydroxy atorvastatin (4-AT), 4-hydroxy atorvastatin lactone (4-ATL), atorvastatin lactone (ATL)) in kidney diseases patients. Genotypes were determined using TaqMan real time PCR in 212 CKD patients, treated with 20 mg of atorvastatin daily for 6 weeks. The steady state plasma concentrations of atorvastatin and its metabolites were quantified using ultraperformance liquid chromatography in combination with triple quadrupole mass spectrometry (UPLC-MS/MS). Univariate and multivariate analyses showed the variant in ABCC4 (rs3742106) was associated with decreased concentrations of AT and its metabolites (2-AT+2-ATL: β = -0.162, p = 0.028 in the dominant model; AT+2-AT+4-AT: β = -0.212, p = 0.028 in the genotype model), while patients carrying the variant allele ABCC4-rs868853 (β = 0.177, p = 0.011) or NR1I2-rs6785049 (β = 0.123, p = 0.044) had higher concentrations of 2-AT+2-ATL in plasma compared with homozygous wildtype carriers. Luciferase activity was enhanced in HepG2 cells harboring a construct expressing the rs3742106-T allele or the rs868853-G allele (p < 0.05 for each) compared with a construct expressing the rs3742106G or the rs868853-A allele. These findings suggest that two functional polymorphisms in the ABCC4 gene may affect transcriptional activity, thereby directly or indirectly affecting release of AT and its metabolites from hepatocytes into the circulation.

Risk Factors of Renal Tubular Dysfunction in Thai People Living with HIV Receiving Tenofovir Disoproxil Fumarate

Tenofovir disoproxil fumarate (TDF) associates with renal tubular dysfunction (RTD) in some people living with HIV (PLWH). We studied clinical and genetic factors associated with RTD in Thai PLWH receiving TDF. RTD was diagnosed in 13 of 65 (20%) patients. The median (interquartile range) age and CD4 cell counts were 43.8 (40.4-50.9) years and 554 (437-716) cells/mm³, respectively. The median duration of TDF use was 46.9 (31.5-54.1) months. Univariate logistic regression demonstrated body mass index (BMI), concomitant use of protease inhibitor (PI), hyperlipidemia, and homozygous C/C SNP rs1059751 of ABCC4 gene as predisposing factors of RTD. In multivariate model, concomitant use of PI [adjusted odds ratio (aOR) 11.39; 95% confidence interval (CI), 1.59- 81.56; P = 0.015], hyperlipidemia (aOR 8.59; 95% CI, 1.46-50.40; P = 0.017), and BMI (aOR 0.76; 95% CI, 0.59-0.98; P = 0.037) remained associated with RTD in patients receiving TDF. PLWH receiving TDF with the presence of these factors should be closely monitored for RTD.

Pharmacogenomics of drug transporters for antiretroviral long-acting pre-exposure prophylaxis for HIV

The use of antiretrovirals (ARVs) as oral, topical, or long-acting pre-exposure prophylaxis (PrEP) has emerged as a promising strategy for HIV prevention. Clinical trials testing Truvada® [tenofovir disoproxil fumarate (TDF)/tenofovir (TFV) and emtricitabine (FTC)] as oral or topical PrEP in African women showed mixed results in preventing HIV infections. Since oral and topical PrEP effectiveness is dependent on adequate drug delivery and availability to sites of HIV infection such as the blood and female genital tract (FGT); host biological factors such as drug transporters have been implicated as key regulators of PrEP. Drug transporter expression levels and function have been identified as critical determinants of PrEP efficacy by regulating PrEP pharmacokinetics across various cells and tissues of the blood, renal tissues, FGT mucosal tissues and other immune cells targeted by HIV. In addition, biological factors such as genetic polymorphisms and genital inflammation also influence drug transporter expression levels and functionality. In this review, drug transporters and biological factors modulating drug transporter disposition are used to explain discrepancies observed in PrEP clinical trials. This review also provides insight at a pharmacological level of how these factors further increase the susceptibility of the FGT to HIV infections, subsequently contributing to ineffective PrEP interventions in African women.

Important roles of transporters in the pharmacokinetics of anti-viral nucleoside/nucleotide analogs

INTRODUCTION

Nucleoside analogs are an important class of antiviral agents. Due to the high hydrophilicity and limited membrane permeability of antiviral nucleoside/nucleotide analogs (AVNAs), transporters play critical roles in AVNA pharmacokinetics. Understanding the properties of these transporters is important to accelerate translational research for AVNAs.

AREAS COVERED

The roles of key transporters in the pharmacokinetics of 25 approved AVNAs were reviewed. Clinically relevant information that can be explained by the modulation of transporter functions is also highlighted.

EXPERT OPINION

Although the roles of transporters in the intestinal absorption and renal excretion of AVNAs have been well identified, more research is warranted to understand their roles in the distribution of AVNAs, especially to immune privileged compartments where treatment of viral infection is challenging. P-gp, MRP4, BCRP, and nucleoside transporters have shown extensive impacts in the disposition of AVNAs. It is highly recommended that the role of transporters should be investigated during the development of novel AVNAs. Clinically, co-administered inhibitors and genetic polymorphism of transporters are the two most frequently reported factors altering AVNA pharmacokinetics. Physiopathology conditions also regulate transporter activities, while their effects on pharmacokinetics need further exploration. Pharmacokinetic models could be useful for elucidating these complicated factors in clinical settings.

Pharmacokinetics of Tenofovir Alafenamide Fumarate and Tenofovir in the Chinese People: Effects of Non-Genetic Factors and Genetic Variations

Background

Tenofovir alafenamide fumarate (TAF) was approved for HBV treatment in China in 2018. Despite higher antiviral efficacy and less impact on renal function and bone mineral density, the pharmacokinetic profiles of TAF are highly variable. The objectives of this study were to investigate the pharmacokinetics of TAF in the Chinese population and explore the associations between TAF and genetic polymorphisms and non-genetic factors.

Patients and Methods

A total of 64 healthy Chinese subjects aged 18~65 years old were planned to enroll. According to the dietary intake status, the subjects were divided into two groups (n = 32 per group). The concentrations of TAF and tenofovir were measured by HPLC-MS/MS, and the single-nucleotide polymorphisms were analyzed by MALDI-TOF MS.

Results

All the enrolled participants (18–35 years) completed the clinical trial study. Similar to the results reported in other ethnic populations, the pharmacokinetic profiles of TAF and tenofovir were highly variable in the Chinese people, and the HFHC diet can significantly increase the systemic exposure of TAF. We determined both HFHC diet and rs7311358 (SLCO1B3) genotypes were independently associated with TAF AUC_0-t, while HFHC diet, age and rs3740066 (ABCC2) variants were predictive of t_1/2 of tenofovir (P < 0.05). The subjects with the AA genotype in rs7311358 had significantly higher TAF AUC_0-t values (1.15 times) than those with a G allele, and the t_1/2 of tenofovir in the rs3740066 TT genotype group was 1.23 times longer than that of CC genotype group. Furthermore, there was a trend of higher TAF AUC and shorter tenofovir t_1/2 for the rs2032582 (ABCB1) T allele and rs3742106 (ABCC4) CC variant, respectively, although not statistically significant in the multiple linear regression analysis.

Conclusion

This study provided new evidence to suggest a critical link between both genetic and non-genetic factors and TAF pharmacokinetics in the Chinese people.

ABCC4 single-nucleotide polymorphisms as markers of tenofovir disoproxil fumarate-induced kidney impairment

Recently, the use of antiretroviral drug tenofovir disoproxil fumarate (TDF) is increased, thanks to the new co-formulation with doravirine, the availability of booster-free regimens, and its advantageous lipid-lowering effect. The aim of our study was to identify genetic markers that contribute to assess the risk of TDF-related renal toxicity. We have retrospectively investigated, in 179 HIV positive patients treated with TDF, the association between the main variants in ABCC2, ABCC4, and ABCC10 genes and four safety endpoints, three clinically relevant as renal outcomes and a higher tenofovir plasma concentration. In patients with an annual eGFR decline >5 mL/min/1.73 m² a difference in genotype frequencies was observed for ABCC10 c.1875 + 526 G>A (3 subjects AA vs. 44 GG + GA, p = 0.045). In patients with an eGFR decrement >25%, plus a decline in GFR category and TDF discontinuation, a difference was observed for ABCC4 c.*38T>G (35 subjects TG + GG vs. 18 TT, p = 0.052). At univariate analysis OR was 1.39 [(95% CI 1.00-1.96) p = 0.054] and at multivariate analysis OR was 1.49 [(95% CI 1.00-2.22) p = 0.049]. The stronger associations were found between the tenofovir accumulation and ABCC4 c.*38T>G and c.3348G>A: the percentage of these patients was higher in the TG + GG (p = 0.011) and in the AA (p = 0.004) genotype, respectively. The logistic regression analysis confirmed these significant relationships. No significant association was observed in patients with eGFR < 60 mL/min/1.73m² and with the studied ABCC2 polymorphisms. Our results show a major role for a combined determination of ABCC4/ABCC10 variants as an indicator of tenofovir toxicity in the clinical practice.

Genetic Associations with Weight Gain among South Africans who Initiated Dolutegravir-Containing and Tenofovir-Containing Regimens

BACKGROUND

Excessive weight gain affects some HIV-positive individuals prescribed dolutegravir-containing regimens. Mechanisms underlying such weight gain are unknown.

SETTING

Data and DNA from antiretroviral therapy-naïve participants who were randomized to initiate dolutegravir with emtricitabine plus either tenofovir alafenamide (TAF) or tenofovir disoproxil fumarate (TDF) in the ADVANCE study (NCT03122262) were used to characterize associations between human genetic polymorphisms and magnitude of weight gain.

METHODS

Associations with percent weight gain from baseline to week 48 were assessed using multivariable linear regression models. Primary analyses a priori considered 59 polymorphisms and 10 genes of potential relevance to dolutegravir, TAF, or TDF pharmacokinetics. We also explored genome-wide associations.

RESULTS

Among the 314 (92%) of 340 dolutegravir recipients who were successfully genotyped, 160 (47%) and 154 (45%) were randomized to TAF/emtricitabine and TDF/emtricitabine, respectively. In target gene analyses, the lowest P-values for the dolutegravir and tenofovir groups were ABCG2 rs4148149 (P = 7.0 × 10-4) and ABCC10 rs67861980 (P = 1.0 × 10-2), respectively, which were not significant after correction for multiple testing. In genome-wide analyses, the lowest P-values were rs7590091 in TMEM163 (P = 3.7 × 10-8) for dolutegravir, rs17137701 in LOC105379130 (P = 6.4 × 10-8) for TAF, and rs76771105 in LOC105371716 (P = 9.7 × 10-8) for TDF.

CONCLUSIONS

Among South African participants in a randomized clinical trial of dolutegravir plus either TAF/emtricitabine or TDF/emtricitabine, we identified several potential genetic associations with weight gain. Only TMEM163 rs7590091 withstood correction for multiple testing. These associations warrant replication in other cohorts.

Pharmacogenetics of tenofovir and emtricitabine penetration into cerebrospinal fluid

BACKGROUND

Blood-cerebrospinal fluid (CSF) barrier transporters affect the influx and efflux of drugs. The antiretrovirals tenofovir and emtricitabine may be substrates of blood-brain barrier (BBB) and blood-CSF barrier transporters, but data are limited regarding the pharmacogenetics and pharmacokinetics of their central nervous system (CNS) penetration.

OBJECTIVES

We investigated genetic polymorphisms associated with CSF disposition of tenofovir and emtricitabine.

METHOD

We collected paired plasma and CSF samples from 47 HIV-positive black South African adults who were virologically suppressed on efavirenz, tenofovir and emtricitabine. We considered 1846 single-nucleotide polymorphisms from seven relevant transporter genes (ABCC5, ABCG2, ABCB1, SLCO2B1, SCLO1A2, SLCO1B1 and ABCC4) and 782 met a linkage disequilibrium (LD)-pruning threshold.

RESULTS

The geometric mean (95% confidence interval [CI]) values for tenofovir and emtricitabine CSF-to-plasma concentration ratios were 0.023 (0.021-0.026) and 0.528 (0.460-0.605), respectively. In linear regression models, the lowest p-value for association with the tenofovir CSF-to-plasma ratio was ABCB1 rs1989830 (p = 1.2 × 10-3) and for emtricitabine, it was ABCC5 rs11921035 (p = 1.4 × 10-3). None withstood correction for multiple testing.

CONCLUSION

No genetic polymorphisms were associated with plasma, CSF concentrations or CSF-to-plasma ratios for either tenofovir or emtricitabine.

Pharmacogenomics with red cells: a model to study protein variants of drug transporter genes

The PharmacoScan pharmacogenomics platform screens for variation in genes that affect drug absorption, distribution, metabolism, elimination, immune adverse reactions and targets. Among the 1,191 genes tested on the platform, 12 genes are expressed in the red cell membrane: ABCC1, ABCC4, ABCC5, ABCG2, CFTR, SLC16A1, SLC19A1, SLC29A1, ATP7A, CYP4F3, EPHX1 and FLOT1. These genes represent 5 ATP-binding cassette proteins, 3 solute carrier proteins, 1 ATP transport protein and 3 genes associated with drug metabolism and adverse drug reactions. Only ABCG2 and SLC29A1 encode blood group systems, JR and AUG, respectively. We propose red cells as an ex vivo model system to study the effect of heritable variants in genes encoding the transport proteins on the pharmacokinetics of drugs. Altered pharmacodynamics in red cells could also cause adverse reactions, such as haemolysis, hitherto unexplained by other mechanisms.

Pharmacokinetics of nucleoside/nucleotide reverse transcriptase inhibitors for the treatment and prevention of HIV infection

INTRODUCTION

Despite dramatic increases in new drugs and regimens, a combination of two nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs) remains the backbone of many regimens to treat HIV.

AREA COVERED

This article summarizes the pharmacokinetic characteristics of approved NRTIs that are currently in the international treatment and prevention guidelines.

EXPERT OPINION

Compared to other NRTIs, tenofovir alafenamide fumarate (TAF) is more advantageous in terms of potency and safety. It is therefore a preferred choice in combination with emtricitabine (FTC) in most HIV treatment guidelines. The efficacy of the two-drug combination of NRTI/Integrase strand-transfer inhibitor, i.e. lamivudine/dolutegravir has been approved as an option for initial therapy. This regimen however has some limitations in patients with HBV coinfection. The two NRTI combinations tenofovir disproxil fumarate (TDF)/FTC and TAF/FTC have also been approved for pre-exposure prophylaxis (PrEP). Interestingly, a promising long-acting nucleoside reverse transcriptase translocation inhibitor, islatravir, formulated for implant was well tolerated and remained effective for up to a year, suggesting its potential as a single agent for PrEP. In the next decade, it remains to be seen whether NRTI-based regimens will remain the backbone of preferred ART regimens, or if the treatment will eventually move toward NRTI-sparing regimens to avoid long-term NRTI-toxicity.

Pharmacogenetic determinants of kidney-associated urinary and serum abnormalities in antiretroviral-treated HIV-positive patients

Tenofovir disoproxyl fumarate (TDF) has been associated with renal tubular abnormalities, phosphaturia and proteinuria (retinol binding protein, RBP, loss): vitamin D (VD) and PTH affect these markers. Aim was to understand if some single nucleotide polymorphisms (SNPs) were predictors of renal abnormalities in an Italian cohort of HIV-affected patients. DNA was analyzed through real-time PCR, urinary RBP corrected by creatinine (uRBP/Cr). The majority of patients received TDF. Abnormal uRBP/Cr was more frequent in TDF recipients: eGFR <90 mL/min and TDF were predictors in the whole cohort, whereas eGFR <90 mL/min, TDF concentrations and CYP24A1-3999TT in TDF-treated patients. Phosphate levels were higher low VD level patients: age <50 years, CYP27B1 + 2838CC genotype and non-European ancestry were predictors. PTH levels were border-line higher in TDF patients: non-European ancestry, females, TDF, VD levels < 30 ng/mL and SLC28A2-124CT/TT and ABCC2-24CC were predictors. For the first time, SNPs were associated with PTH, phosphate, calcium and tubular dysfunction in HIV-infected patients.

Multidrug resistance-associated protein 4 in pharmacology: Overview of its contribution to pharmacokinetics, pharmacodynamics and pharmacogenetics

MRP4 is an ABC membrane transporter involved in clinical outcomes as it is located in many tissues that manages the transport and the elimination of many drugs. This review explores the implication of MRP4 in clinical pharmacology and the importance of its genetic variability. Although there is no specific recommendation regarding the study of MRP4 in drug development, it should be considered when drugs are eliminated by the kidney or liver or when drug-drug interactions are expected.

Tenofovir-associated kidney disease in Africans: a systematic review

BACKGROUND

Data on chronic kidney disease development in HIV infection is important towards building a comprehensive knowledge of HIV, ageing and polypharmacy in Africa. Several previous studies on tenofovir-associated kidney disease in Africa have shown conflicting results. This review summarises what is known about the development of kidney disease in HIV-positive African patients on tenofovir disoproxil fumarate (TDF)-containing ART. We set out to document the occurrence of kidney disease in HIV-positive Africans on TDF-containing ART in population-based studies and to evaluate the renal safety of TDF in Africans.

METHODS

We conducted a systemic review using published studies which were identified through a computerized search of original research using the Medline/PubMed database, EMBASE, EBM Reviews, Proquest Google Scholar and Global Health reported from inception until 5 October 2017. Two reviewers independently abstracted the data and performed quality assessment of the included studies. We screened 595 articles and included 31 in the qualitative analysis performed.

RESULTS

A total of 106 406 patients (of whom 66,681 were on Tenofovir) were involved in these 31 studies with sample sizes ranging from 30 to 62,230. Duration on tenofovir-containing ART ranged from those initiating ART at baseline to those who received TDF for up to 9 years. All but one of the studies involved only patients 16 years and older. The studies had differing definitions of kidney dysfunction and were of variable study design quality. The documented outcomes had substantial discrepancies across the studies, most likely due to methodological differences, study size and disparate outcome definitions.

CONCLUSIONS

Our review identified studies in Africans reporting statistically significant renal function decline associated with TDF use but the clinical significance of this effect was not enough to contraindicate its continued use in ART regimens. Consistent with studies in other populations, patients are at greater risk if they have pre-existing renal disease and are more advanced in age. More research is needed on paediatric populations under 16 years of age. Trial registration This review was registered on Prospero (registration number CRD42018078717).

Reduced Kidney Function in Tenofovir Disoproxil Fumarate Based Regimen and Associated Factors: A Hospital Based Prospective Observational Study in Ethiopian Patients

Purpose

Tenofovir disoproxil fumarate (TDF), a drug broadly used in combination antiretroviral therapy, is associated with renal dysfunction but the prevalence varied from country to country and it is not known in Ethiopia. The objectives of this study were to assess the prevalence of renal dysfunction and risk factors associated with it and the mean change in estimated glomerular filtration rate in human immunodeficiency virus infected patients receiving TDF based antiretroviral regimen at Tikur Anbessa Specialized Hospital.

Method

It was a hospital based prospective cohort study. The study participants were treatment naïve HIV infected patients initiating TDF containing combination antiretroviral therapy or switched to it because of adverse events. Multivariable logistic analysis was used to identify variables which have significant association.

Result

A total of 63 study participants were studied, 16 (25.4%) of whom had fall in eGFR greater than 25% relative to baseline. Only age greater than 50 years, baseline CD4 count less than 200 cells/mm³, and baseline proteinuria were significantly associated with renal dysfunction in multivariable logistic regression. There was -8.4 ml/min/1.73m² mean change in estimated glomerular filtration rate relative to baseline at six months of study.

Conclusion

The renal dysfunction (defined as decline in eGFR greater than 25%) was found in a quarter of the study population. The long term impact and the clinical implication of it are not clear. Future prospective study is required with large sample size and long duration to ascertain the prevalence of decline greater than 25% in estimated glomerular filtration rate and its progression to chronic kidney disease.

Tenofovir disoproxil fumarate discontinuation for renal outcomes: any room for treatment personalization?

Tenofovir disoproxil fumarate (TDF) is a very effective antiviral drug that has been associated with tubular dysfunction. The aim of this study was to analyze the demographic, pharmacokinetic, and pharmacogenetic variables associated with TDF discontinuation for renal outcomes in stable HIV-positive patients using multivariable analyses. Three hundred and four patients were included (73% male, with median age and eCrCl of 45.3 years and 90.9 mL/min, respectively). After a median follow-up of 28.3 months, 27 patients discontinued TDF for renal adverse events [persistent urinary abnormalities (n = 21) or eCrCl < 60 mL/min (n = 6)] providing an incidence of 3.77 events per 100 patient-year. The probability of TDF discontinuation was higher with several features (male gender, older age, not Caucasians ancestry, absence of intravenous drug abuse, protease inhibitors, previous indinavir, HCV-positivity, lower CD4 cell count, detectable HIV-RNA, lower eCrCl, spot-urine proteinuria) and higher tenofovir concentrations but not genetic variants. Tenofovir plasma concentrations were prognostic of TDF discontinuation for renal adverse events suggesting that dose-adjustment may be warranted for long-term safety.

Pharmacogenetics of Antiretroviral Drug Response and Pharmacokinetic Variations in Indigenous South African Populations

Interindividual and interethnic differences in response to antiretroviral drugs (ARVs) are influenced by genetic variation. The few genomic studies conducted among African-Americans and African ethnic groups do not reflect the extensive genetic diversity within African populations. ARVs are widely used in Africa. Therefore, genomic characterization of African populations is required before genotype-guided dosing becomes possible. The aim of this study was to determine and report on the frequency of genetic variants in genes implicated in metabolism and transport of ARVs in South African populations. The study comprised 48 self-reported South African Colored (SAC) and 296 self-reported Black African (BA) individuals. Allele and genotype frequency distributions for 93 variants contributing to metabolism and transport of ARVs were compared between groups, and other global populations. Fifty-three variants had significant differences in allele and genotype frequencies when comparing SAC and BA groups. Thirteen of these have strong clinical annotations, affecting efavirenz and tenofovir pharmacokinetics. This study provides a summary of the genetic variation within genes implicated in metabolism and transport of ARVs in indigenous South African populations. The observed differences between indigenous population groups, and between these groups and global populations, demonstrate that data generated from specific African populations cannot be used to infer genetic diversity within other populations on the continent. These results highlight the need for comprehensive characterization of genetic variation within indigenous African populations, and the clinical utility of these variants in ARV dosing for global precision medicine. Population pharmacogenetics is a nascent field of global health and warrants further research and education.

A LC/MS/MS method for determination of tenofovir in human plasma and its application to toxicity monitoring

Tenofovir disoproxil fumarate is a pro-drug of the active metabolite tenofovir widely used against the HIV1, HIV2, and Hepatitis B virus. Several studies have been conducted and found kidney injury associated with tenofovir exposure. High tenofovir plasma concentration correlated with kidney injury in tenofovir-exposed patients. The present study developed and validated a simple and cost-effective LC/MS/MS method to determine tenofovir level in human plasma. A small plasma volume of 80 μl is utilized for the sample preparation. The samples were separated by Luna C18 (100 mm × 2.0 mm, 3 μm) using gradient elution with a mobile phase consisting of water (containing 0.1% formic acid) and acetonitrile (90:10, v/v). The detection was achieved through multiple reaction monitoring using positive ionization mode on the triple quadrupole mass spectrometer with a run time of 10 min. The monitoring transitions were set at m/z 288.0 → 176.1 and 136.1 for tenofovir and m/z 226.1 → 152.0 for acyclovir (as the internal standard). This standard curve was linear from 10 to 640 ng/ml, with the lower limit of quantification of 10 ng/ml. The inter- and intra-day precision results were less than 12.3% and their accuracies were within the acceptable range of 84.9-113.1%. The validated method was successfully applied to the study of tenofovir induced kidney injury in HIV-1 infected patients taking 300 mg once daily for more than 4 weeks.

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.

Pharmacogenetic Analysis of the Model-Based Pharmacokinetics of Five Anti-HIV Drugs: How Does This Influence the Effect of Aging?

Analysis of aging and pharmacogenetics (PGx) on antiretroviral pharmacokinetics (PKs) could inform precision dosing for older human HIV‐infected patients. Seventy‐four participants receiving either atazanavir/ritonavir (ATV/RTV) or efavirenz (EFV) with tenofovir/emtricitabine (TFV/FTC) provided PK and PGx information. Aging‐PGx‐PK association and interaction analyses were conducted using one‐way analysis of variance (ANOVA), multiple linear regression, and Random Forest ensemble methods. Our analyses associated unbound ATV disposition with multidrug resistance protein (MRP)4, RTV with P‐glycoprotein (P‐gp), and EFV with cytochrome P450 (CYP)2B6 and MRP4 genetic variants. The clearance and cellular distribution of TFV were associated with P‐gp, MRP2, and concentrative nucleoside transporters (CNTs), and FTC parameters were associated with organic cation transporters (OCTs) and MRP2 genetic variants. Notably, p16^INK4a expression, a cellular aging marker, predicted EFV and FTC PK when genetic factors were adjusted. Both age and p16^INK4a expression interacted with PGx on ATV and TFV disposition, implying potential dose adjustment based on aging may depend on genetic background.

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.

Pharmacogenetics-based population pharmacokinetic analysis of tenofovir in Thai HIV-infected patients

AIM

To develop a population pharmacokinetic model and identify sources of variability, genetic and nongenetic factors, of tenofovir.

METHODS

The ABCC2 and ABCC4 polymorphisms were genotyped in 342 patients. A nonlinear mixed effects model was used to develop the population pharmacokinetic model and investigate the influence of these polymorphisms and other patient specific covariates on the pharmacokinetics of tenofovir.

RESULTS

The estimated glomerular filtration rate calculated by the Cockcroft and Gault equation, concomitant use of lopinavir/ritonavir and ABCC4 3463A>G polymorphism were associated with tenofovir apparent oral clearance (CL/F). The use of lopinavir/ritonavir decreased tenofovir CL/F by 25%. Patients carrying ABCC4 3463 AG or GG had a tenofovir CL/F 11% higher than those with genotype AA.

CONCLUSION

Renal function, co-medication and genetic variation impact the pharmacokinetics of tenofovir. These factors should be taken into consideration to guide the individual tenofovir disoproxil fumarate dosage regimen in Thai HIV-infected patients.

Drug interactions and the role of pharmacokinetic trials in guiding choices in first-line HIV therapy in low-income and middle-income countries

PURPOSE OF REVIEW

Low- and middle-income countries (LMICs) face specific challenges in the treatment of people living with HIV. Drug-drug interactions (DDIs) involving antiretrovirals (ARVs) are prevalent in all settings and have considerable potential to cause clinical harm to patients via toxicity or reduced efficacy of treatment. Differing comorbidities, endemic infections and traditional medicines may complicate ARV therapy (ART) in LMICs, which usually takes a public health approach in these settings, with fewer alternative regimens available. This review discusses the issues surrounding pharmacokinetic DDI studies and their application to ART in LMICs, with particular reference to first-line ART regimens.

RECENT FINDINGS

Pharmacokinetic studies with clinical endpoints are the gold standard for informing management of DDIs; however, data relevant to LMICs are sparse and of low quality. There is significant potential for clinically relevant DDIs between ARVs and antimalarials, antimycobacterials and drugs used in the treatment of neglected tropical diseases.

SUMMARY

Many pharmacokinetic studies are difficult to interpret in LMICs due to differences in patient factors including weight, disease state and genetic polymorphisms. DDI studies relevant to LMICs may also be lacking due to the neglected nature of relevant comorbidities. The ARVs currently available as first-line ART in LMICs are among those with highest propensity for DDIs.

Renal function in HIV/HBV co-infected and HBV mono-infected patients on a long-term treatment with tenofovir in real life setting

The human immunodeficiency virus (HIV)/hepatitis B virus (HBV) co-infection is likely to be associated with an increased risk of kidney disease, due to the additional factors that may affect renal function in the HIV population. We aimed to evaluate renal toxicity in HIV/HBV and HBV mono-infected patients on long-term therapy with tenofovir (TDF) and to explore the association of polymorphisms in ATP-binding cassette (ABCC)2, ABCC4, ABCC10 with the development of renal dysfunction. From September 2006 to November 2014, 44 HIV/HBV co-infected and 34 HBV mono-infected patients were commenced on TDF. Data of renal safety were retrospectively collected and analyzed. ABCC2, ABCC4 and ABCC10 genotypes were identified by real-time PCR. Over 60 months of observation, there was a significant increase in mean creatinine levels from baseline (P<.01) that was not significantly different between the two study groups. Moreover, a significant decline in estimated glomerular filtration rate (eGFR) was observed from baseline (P<.01), and it was significantly greater in HBV mono-infected than co-infected patients (P=.03). The distribution of ABCC2, ABCC4 and ABCC10 genotypes among a subgroup of 34 patients did not show significant association with eGFR decline <90 mL/min per 1.73 m² . Although our findings showed a statistically significant decrease in eGFR with long-term use of TDF, its clinical impact seems to be modest. The role of genetic factors to identify patients at greater risk for developing tenofovir-induced renal toxicity needs to be further investigated.

Clinical and genetic factors associated with kidney tubular dysfunction in a real-life single centre cohort of HIV-positive patients

Background

Tenofovir (TDF) is one of the most widely used antiretroviral drug. Despite the high degree of tolerability a small percentage of patients experienced alteration in tubular function during TDF use. Intracellular TDF disposition is regulated by ATP-binding cassette (ABC) drug efflux transporters and, a reduced transport activity may be implicated in accumulation of TDF into the cells. The aim of our study was to assess the major determinants of TDF associated tubular dysfunction (KTD) in a real-life setting including the usefulness of single-nucleotide polymorphisms (SNPs) mapping into ABCC2, ABCC4 and ABCC10 genes.

Methods

We retrospectively analyzed all HIV positive patients who were followed at the Infectious Diseases Unit, DIBIC Luigi Sacco, University of Milan from April 2013 to June 2016. All patients treated with TDF who underwent a genotypization for the functional variants mapping in ABCC2 rs717620 (−24 C > T), ABCC4 rs1751034 (3463 A > G) and ABCC10 rs2125739 (T > C) were evaluated. KTD was defined as the presence of urine phosphate wasting and/or proteinuria at 24 h urine analysis.

Results

One hundred fifty-eight patients were genotyped, of which 42 (26.6%) experienced signs of KTD. No statistical significant differences were observed among patients with or without KTD regarding age, gender, ethnicity and comorbidities (hypertension and diabetes). The percentage of patients with KTD was higher among those with “GG” genotype at rs1751034 of ABCC4 compared to patients without KTD [6 (14.3%) vs 4 (3.5%), p = 0.01]. No statistical significant differences were observed regarding the distribution of ABCC2 and ABCC10 SNPs. Carriers of “G” allele in homozygous status at rs1751034 of ABCC4 showed a significant association with KTD (Odds Ratio 4.67, 95% CI 1.25–17.46, p = 0.02) in bivariate analysis, but this association was lost in multivariable analysis. A significant association between bone diseases and KTD was observed (Odds Ratio 3.178, 95%CI 1.529–6.603, p = 0.002).

Conclusions

According to our results ABCC4 rs1751034 could be a genetic determinant of KTD; however validation studies are needed for therapy personalization. Noteworthy, a strong association between bone disease and KTD was also observed.

Tenofovir Disoproxil Fumarate Is a New Substrate of ATP-Binding Cassette Subfamily C Member 11

Tenofovir disoproxil fumarate (TDF), a nucleotide reverse transcriptase inhibitor, after conversion to tenofovir (TFV), is mainly eliminated by glomerular filtration and active tubular secretion. The major adverse effect of tenofovir is nephrotoxicity; however, the exact mechanism remains poorly understood. In this study, the ATP-binding cassette subfamily C member 11 (ABCC11; multidrug resistance protein 8 [MRP8]) transporter, which is abundant in proximal tubular cells, was demonstrated to act as an efflux transporter of tenofovir. Real-time PCR (RT-PCR) and indirect immunofluorescence assays were used to determine MRP8 overexpression in a continuous cell line. Tenofovir accumulations were assessed by cytotoxicity, cellular transport, and vesicular uptake assays. Substrate specificity was confirmed using MK-571, an MRP-specific inhibitor, and methotrexate, which served as a known substrate. Intracellular and intravesicular concentrations of tenofovir were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The 50% cytotoxic concentration (CC₅₀) of TDF in MRP8-overexpressing cells was 4.78 times higher than that of parental cells. Transport assays also showed that the intracellular accumulation of tenofovir in MRP8-overexpressing cells was 55 times lower than that in parental cells and was partly reversed by MK-571. Similarly, an "inside-out" vesicular uptake assay, using Sf9 inverted membrane vesicles to allow measuring of accumulation of the substrates into the vesicles, demonstrated a higher intravesicular concentration of tenofovir in MRP8-overexpressing vesicles than in Sf9 insect control vesicles. These effects were effectively reversed by increasing concentrations of the specific inhibitor MK-571. In conclusion, tenofovir is a new substrate of the MRP8 transporter. An alteration in the activity of this efflux pump may increase the intracellular accumulation of tenofovir in proximal renal tubular cells.

Population Pharmacokinetic Modeling of Tenofovir in the Genital Tract of Male HIV-Infected Patients

The aims of this study were to describe the blood plasma (BP) and seminal plasma (SP) pharmacokinetics of tenofovir (TFV) in HIV-1-infected men, to assess the role of genetic polymorphism in the variability of TFV transfer into the male genital tract, and to evaluate the impact of TFV SP exposure on seminal plasma HIV load (spVL). Men from the Evarist-ANRS EP 49 study treated with TFV as part of their antiretroviral therapy were included in the study. A total of 248 and 217 TFV BP and SP concentrations from 129 men were available for the analysis. For pharmacogenetic assessment, a total of 121 single nucleotide polymorphisms (SNP) were genotyped. Data were analyzed using a nonlinear mixed-effects modeling approach. TFV pharmacokinetics were best described by a two-compartment model for BP and by an effect compartment with different input and output constants for SP. TFV exposures (area under the concentration-time curve from 0 to 24 h [AUC_0-24]) were higher in SP than in BP (median AUC_0-24, 7.01 versus 2.97 mg · liter^-1 · h, respectively). The median (range) SP-to-BP AUC_0-24 ratio was 2.24 (0.53 to 34.13). After correction for multiple testing, none of the SNPs were significantly associated with the TFV transfer rate constant. The impact of the TFV SP AUC_0-24 or TFV SP-to-BP AUC_0-24 ratio on spVL was not significant (P = 0.808 and 0.768, respectively). This is the first population model describing TFV pharmacokinetics in the male genital tract. TFV SP concentrations were higher than BP concentrations. Despite TFV SP exposures being higher than BP exposures, an spVL was detectable for 12.2% of the men.

Pharmacogenetic considerations in the treatment of HIV

After the introduction of highly active antiretroviral therapy in the 1990s, the perception of the diagnosis of HIV infection gradually shifted from a 'death sentence' to a chronic disease requiring long-term treatment. The host genetic variability has been shown to play a relevant role in both antiretroviral drugs bioavailability and adverse effects susceptibility. Knowledge about pharmacogenetics role in HIV infection treatment has largely increased over the last years, and is reviewed in the present report, as well as future perspectives for the inclusion of pharmacogenetics information in the directing of HIV infection treatment.

Plasma tenofovir trough concentrations are associated with renal dysfunction in Japanese patients with HIV infection: a retrospective cohort study

Background

Plasma tenofovir (TFV) trough concentrations may be relevant for tenofovir disoproxil fumarate (TDF)-induced renal dysfunction. The purpose of this study was to determine the association between plasma TFV trough concentrations and TDF-induced renal dysfunction in Japanese patients with human immunodeficiency virus (HIV) infection.

Methods

A 48-week, retrospective cohort study was performed with Japanese patients with HIV infection who started a TDF-containing combination antiretroviral therapy regimen. Plasma TFV trough concentrations were obtained at steady state. The following variables were included in the analysis: sex, age, body weight, body mass index (BMI), serum creatinine, CD4+ cell count, HIV-RNA, concomitant medications, comorbidities, plasma TFV trough concentrations, and estimated glomerular filtration rate (eGFR). For comparisons of variables, we used Mann-Whitney U tests or Fisher’s exact tests. Then, variables associated with renal dysfunction in the univariate analysis were entered into correlation analysis.

Results

The analysis included 11 patients. The rate of decrease in eGFR was significantly correlated with body weight (Spearman correlation = −0.645, p = 0.041), BMI (Spearman correlation = −0.682, p = 0.031), and plasma TFV trough concentrations (Spearman correlation = 0.709, p = 0.025).

Conclusions

Despite the small sample size, our findings suggest that higher plasma TFV trough concentrations may cause TDF-induced renal dysfunction. To prevent TDF-induced renal dysfunction, we propose that individual monitoring of plasma TFV trough concentrations should be performed in Japanese patients with HIV infection.

Electronic supplementary material

The online version of this article (doi:10.1186/s40780-016-0056-5) contains supplementary material, which is available to authorized users.

Key toxicity issues with the WHO-recommended first-line antiretroviral therapy regimen

INTRODUCTION

WHO recommends tenofovir, efavirenz, and lamivudine or emtricitabine for first-line antiretroviral therapy (ART) in adults, which replaced more toxic regimens using stavudine, zidovudine or nevirapine. Areas covered: We searched Pubmed to identify observational studies and randomized controlled trials reporting toxicity of these antiretrovirals published between 2011 and 2016, and hand-searched abstracts presented at major HIV conferences in 2015 and 2016, focusing on data from sub-Saharan Africa. Tenofovir's nephrotoxicity manifests as mild renal tubular dysfunction (common and of uncertain clinical significance), acute kidney injury (rare), and chronic declining glomerular filtration rate (common). African studies, which include high proportions of patients with renal dysfunction from opportunistic diseases, report population improvement in renal function after starting tenofovir-based ART. Tenofovir modestly decreases bone mineral density, and there is emerging data that this increases fracture risk. Efavirenz commonly causes early self-limiting neuropsychiatric toxicity and hypersensitivity rashes. Recent studies have highlighted its long-term neuropsychiatric effects, notably suicidality and neurocognitive impairment, and metabolic toxicities (dyslipidemia, dysglycemia, and lipoatrophy). We point out the challenges clinicians face in the recognition and attribution of adverse drug reactions. Expert commentary: Tenofovir and efavirenz are generally well tolerated, but both are associated with potentially serious toxicities. Pharmacovigilance systems in resource-limited settings with high HIV burden should be strengthened.

The Pharmacological and Physiological Role of Multidrug-Resistant Protein 4

Multidrug-resistant protein 4 (MRP4), a member of the C subfamily of ATP-binding cassette transporters, is distributed in a variety of tissues and a number of cancers. As a drug transporter, MRP4 is responsible for the pharmacokinetics and pharmacodynamics of numerous drugs, especially antiviral drugs, antitumor drugs, and diuretics. In this regard, the functional role of MRP4 is affected by a number of factors, such as genetic mutations; tissue-specific transcriptional regulations; post-transcriptional regulations, including miRNAs and membrane internalization; and substrate competition. Unlike other C family members, MRP4 is in a pivotal position to transport cellular signaling molecules, through which it is tightly connected to the living activity and physiologic processes of cells and bodies. In the context of several cancers in which MRP4 is overexpressed, MRP4 inhibition shows striking effects against cancer progression and drug resistance. In this review, we describe the role of MRP4 more specifically in both healthy conditions and disease states, with an emphasis on its potential as a drug target.