Polymorphisms of tenofovir disoproxil fumarate transporters and risk of kidney tubular dysfunction in HIV-positive patients: genetics of tenofovir transporters

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.

Proximal tubular dysfunction related to tenofovir in people living with HIV/AIDS: a pharmacogenetic study

OBJECTIVES

The purpose of this case-control study was to verify the association between single nucleotide polymorphisms (SNPs) in genes encoding drug transporters related to tenofovir disoproxil fumarate (TDF) and proximal renal tubular dysfunction (PRTD), and the association between PRTD and clinical characteristics.

METHODS

The 'cases' met the diagnostic criteria for PRTD, determined by the presence of two or more of the following abnormalities: non-diabetic glycosuria, metabolic acidosis, increased uric acid and phosphorus excretion, decreased tubular phosphorus reabsorption and β2-microglobulinuria. We analyzed eight SNPs in ABCC2, ABCC4, ABCC10 and SLC28A2 genes. Genotyping was performed using real-time PCR.

RESULTS

Of the 204 people living with HIV, 38 (18.6%) met the criteria for diagnosis of PRTD and 131 were male (64.2%), with a mean age of 49 years and a history of previous antiretroviral therapy for an average of 5 years. In the multivariate analysis, older individuals, TDF use, protease inhibitor, antihypertensives and anticonvulsants were associated with a risk of developing PRTD. Increased excretion of β2microglobulin was associated with the A/G genotype of rsCC8187710 from ABCC2 ( P  = 0.003) and the following genotypes of ABCC4 SNPs: A/G from rs1059751 ( P  = 0.023), G/G from rs1059751 ( P  = 0.030) and C/C of rs3742106 ( P  = 0.041). The increase in the fraction of excreted phosphorus was associated with the C/T genotype of SNCC rsP40037 from ABCC2 ( P  = 0.0041).

CONCLUSIONS

The results indicate an important relationship between SNPs associated with these markers and changes in proximal renal tubule function, and thus support their use as biomarkers for the early detection of PRTD risk.

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.

Prevalence and global trends of polypharmacy among people living with HIV: a systematic review and meta-analysis

Background:

There has been a rising prevalence of polypharmacy among people living with HIV (PLWH). Uncertainty however remains regarding the exact estimates of polypharmacy among these cohorts of patients.

Methods:

We conducted a systematic search of PubMed; EMBASE, CROI, Cochrane Database of Systematic Reviews; Science Citation Index and Database of Abstracts of Reviews of Effects for studies between 1 January 2000 and 30 June 2021 that reported on the prevalence of polypharmacy (ingestion of > 5 non-ART medications) among PLWH on antiretroviral therapy regimen (ART). Prevalence of polypharmacy among HIV-positive patients on ART with Clopper–Pearson 95% confidence intervals were presented. The heterogeneity between studies was evaluated using I2 and τ2 statistics.

Results:

One hundred ninety-seven studies were initially identified, 23 met the inclusion criteria enrolling 55,988 PLWH, of which 76.7% [95% confidence interval (CI): 76.4–77.1] were male. The overall pooled prevalence of polypharmacy among PLWH was 33% (95% CI: 25–42%) (I² = 100%, τ² = 0.9170, p < 0.0001). Prevalence of polypharmacy is higher in the Americas (44%, 95% CI: 27–63%) (I² = 100%, τ² = 1.0886, p < 0.01) than Europe (29%, 95% CI: 20–40%) (I² = 100%, τ² = 0.7944, p < 0.01).

Conclusion:

The pooled prevalence estimates from this synthesis established that polypharmacy is a significant and rising problem among PLWH. The exact interventions that are likely to significantly mitigate its effect remain uncertain and will need exploration by future prospective and systematic studies.

Registration:

PROSPERO: CRD42020170071

Plain Language Summary

Background: In people living with HIV (PLWH), what is the prevalence of polypharmacy and is this influenced by sociodemographic factors?

Methods and Results: In this systematic review and meta-analysis of 23 studies comprising 55,988 participants, we have for the first time found an estimated polypharmacy pooled prevalence of 33% among PLWH. There was a relatively higher pooled prevalence of polypharmacy among the America’s compared with European cohorts of PLWH.

Conclusion: Polypharmacy among PLWH is a rising morbidity that needs urgent intervention both at policy and patient levels of care.

What is polypharmacy in people living with HIV/AIDS? A systematic review

Polypharmacy in people living with HIV/AIDS (PLWHA) is a rising morbidity that exacts hefty economic burden on health budgets in addition to other adverse clinical outcomes. Despite recent advances, uncertainty remains around its exact definition in PLWHA. In this systematic review and Meta-analysis, we explored relevant databases (PUBMED, EMBASE, CROI) for studies evaluating polypharmacy in PLWHA from January 2000 to August 2021 to ascertain the exact numerical threshold that defines this morbidity. Two independent reviewers extracted and reviewed relevant variables for analyses. The review included a total of 31 studies involving n = 53,347 participants with a mean age of 49.5 (SD ± 17.0) years. There was a total of 36 definitions, with 93.5% defining polypharmacy as the concomitant use of 5 or more medications. We found significant variation in the numerical definition of polypharmacy, with studies reporting it as “minor” (N = 3); “major” (N = 29); “severe” (N = 2); “excessive” (N = 1); and “higher” (N = 1). Most studies did not incorporate a duration (84%) in their definition and excluded ART medications (67.7%). A plurality of studies in PLWHA have established that polypharmacy in this cohort of patients is the intake of ≥ 5 medications (including both ART and non-ART). To standardize the approach to addressing this rising morbidity, we recommend incorporation of this definition into national and international PLWHA treatment guidelines.

Drug toxicity in the proximal tubule: new models, methods and mechanisms

The proximal tubule (PT) reabsorbs most of the glomerular filtrate and plays an important role in the uptake, metabolism and excretion of xenobiotics. Some therapeutic drugs are harmful to the PT, and resulting nephrotoxicity is thought to be responsible for approximately 1 in 6 of cases of children hospitalized with acute kidney injury (AKI). Clinically, PT dysfunction leads to urinary wasting of important solutes normally reabsorbed by this nephron segment, leading to systemic complications such as bone demineralization and a clinical scenario known as the renal Fanconi syndrome (RFS). While PT defects can be diagnosed using a combination of blood and urine markers, including urinary excretion of low molecular weight proteins (LMWP), standardized definitions of what constitutes clinically significant toxicity are lacking, and identifying which patients will go on to develop progressive loss of kidney function remains a major challenge. In addition, much of our understanding of cellular mechanisms of drug toxicity is still limited, partly due to the constraints of available cell and animal models. However, advances in new and more sophisticated in vitro models of the PT, along with the application of high-content analytical methods that can provide readouts more relevant to the clinical manifestations of nephrotoxicity, are beginning to extend our knowledge. Such technical progress should help in discovering new biomarkers that can better detect nephrotoxicity earlier and predict its long-term consequences, and herald a new era of more personalized medicine.

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.

Do genetic variations in proximal tubule transporters influence tenofovir-induced renal dysfunction? An exploratory study in a Ghanaian population

OBJECTIVES

To assess associations between polymorphisms within genes encoding proximal tubule transporters implicated in tenofovir renal clearance and kidney tubular dysfunction (KTD), chronic kidney disease (CKD) and individual biochemical parameters.

PATIENTS AND METHODS

The study included a cohort of HIV-positive Ghanaians receiving regimens containing tenofovir disoproxil fumarate (n = 66) for at least 6 months prior to study enrolment. SNPs in ABCC10, ABCC2 and ABCC4 were selected for analysis based on previous published associations. All SNPs were genotyped by real-time PCR allelic discrimination. Creatinine clearance (CLCR), serum and urine creatinine concentrations and biochemical measures of KTD were assessed. Statistical significance was determined through univariate linear or binary logistical regression (P ≤ 0.05).

RESULTS

None of the SNPs evaluated was associated with CKD or KTD. A trend between body weight and higher incidence of CKD (P = 0.012, OR = 0.9) was observed. ABCC10 2843T>C (rs2125739) was significantly associated with lower log10 baseline creatinine (P = 0.001, β= -0.4), higher baseline CLCR (P = 0.008, β = 65.2) and lower CLCR after 1 year (P = 0.024, β= -26.6).

CONCLUSIONS

This study demonstrates an association of ABCC10 rs2125739 with indicators of declining renal function and builds on current knowledge of this interaction within a Ghanaian cohort.

Changing trends in lipid profile and biomarkers of renal function and bone metabolism before and after switching from tenofovir disoproxil fumarate to tenofovir alafenamide: a prospective observational study

Background

Antiretrovirals, including tenofovir, can suppress human immunodeficiency virus (HIV) infection but cannot completely eradicate it. Patients with HIV infection are administered antiretroviral drugs over a long term; thus, managing consequent adverse drug reactions, such as renal dysfunction and bone mineral loss, is important. Currently, highly sensitive biomarkers that can detect adverse drug reactions early have not been well studied.

Methods

This single-center, prospective, observational study explored changes in the biomarkers of renal function, bone metabolism, and lipid profile before and after switching from tenofovir disoproxil fumarate (TDF) to tenofovir alafenamide (TAF) in patients with HIV infection.

Results

All 31 enrolled patients had been treated with antiretrovirals for more than 5 years. The rate of proteinuria decreased significantly after starting TAF-containing antiretroviral regimen. The urinary liver-type fatty acid binding protein (L-FABP)/creatinine ratio was significantly decreased at 3 and 6 months after switching to TAF compared with that before switching to TAF (− 0.5 μg/g Cr at 3 months, and − 0.8 μg/g Cr at 6 months; p < 005 for both at 3 and 6 months). The urinary N-terminal telopeptide (NTx)/creatinine ratio decreased over the study period, and the ratios were significantly different between 3 and 6 months (− 11 nmol/mmol Cr at 3 months, − 15.2 nmol/mmol Cr at 6 months; p = 0.0069 at 3 months, p < 0.0001 at 6 months). Low density lipoprotein-cholesterol level significantly increased at 3 (+ 26 mg/dL) and 6 months (+ 13 mg/dL) compared with that at the baseline (p < 0.0001).

Conclusions

Switching from TDF to TAF decreased the levels of renal and bone biomarkers, such as urinary L-FABP and NTx, but increased low density lipoprotein-cholesterol levels. Future studies should evaluate if these biomarkers, such as urinary L-FABP and NTx, truly detect serious adverse drug reactions early.

The utility of kidney injury molecule-1 as an early biomarker of kidney injury in people living with HIV

There are increasing reports of antiretroviral therapy (ART) drug-related kidney dysfunction. Traditional markers of kidney dysfunction such as urine protein/creatinine ratio and estimated glomerular filtration rate (eGFR) have thus far proven ineffective at detecting some sub-clinical forms of ART-related kidney injury. This is a cross-sectional examination of 114 people living with HIV (PLWH), either naïve (N =104) or treatment experienced (N =10). Urinary kidney injury molecule-1 (KIM-1 ng/mg) thresholds were estimated using electrochemiluminescent assays from stored urine samples and normalised for urinary creatinine excretion (KIM-1/Cr). Correlation coefficients and predictors of kidney tubular injury were compared and derived for both adjusted and unadjusted urinary KIM-1/CR (ng/mg). In PLWH (both ART-naïve and treatment experienced) had a higher baseline unadjusted and adjusted median (≥3.7 ng/mg) and upper tertile (≥6.25 ng/mg) urinary KIM-1/Cr levels compared to either non-normal volunteers (0.39 ng/mg) or those with acute kidney injury in the general population (0.57 ng/mg). When upper tertile KIM-1/Cr (≥6.25 ng/mg) was utilised as a marker of kidney injury, eGFR (ml/min/1.73 m²), white Caucasian ethnicity, and protease inhibitor exposure were significantly associated with increased risk of kidney injury in multivariate analyses (odds ratio 0.91, confidence interval [CI] 0.68–0.98, P = 0.02; odds ratio 8.9, CI 1.6–48.6, p = 0.01; and odds ratio 0.05, CI 0.03–0.9, p =0.04, respectively). We found a significant degree of sub-clinical kidney injury (high unadjusted and adjusted KIM-1/Cr) in PLWH with normal kidney function (eGFR ≥60 ml/min/1.73 m²). We also found a higher baseline KIM-1/Cr (ng/mg) in our study cohort than reported both in normal volunteers and patients with kidney injury in the general population.