Update on tenofovir toxicity in the kidney

Reshaping an Acyclic Nucleoside Phosphonate into a Selective Anti-hepatitis B Virus Compound

Minor structural modifications of acyclic nucleoside phosphonates can dramatically affect their antiviral properties. This work discloses a shift in the selectivity spectrum of 3-hydroxy-2-(phosphonomethoxy)propyl (HPMP) nucleotides from herpesviruses toward hepatitis B virus (HBV) induced by their acyclic chain 2-substitution with a nonpolar group. Two series of racemic (R,S)-2-methyl-3-hydroxy-2-(phosphonomethoxy)propyl (MHPMP) and (R,S)-2-ethynyl-3-hydroxy-2-(phosphonomethoxy)propyl (EHPMP) nucleotides were initially synthesized. Among these, guanine-containing derivatives exhibited significant anti-HBV activities in the submicromolar range. Enantioenriched MHPMPG and EHPMPG analogues were subsequently obtained by Sharpless asymmetric epoxidation. The (S)-enantiomers possessed an 8- to 26-fold higher potency than the relative (R)-forms. A further comparison of the EC₉₀ values indicated that (S)-EHPMPG inhibited HBV replication more effectively than its 2-methyl analogue. A phosphonodiamidate prodrug of (S)-EHPMPG was thus prepared and found to exert a remarkably high anti-HBV activity (EC₅₀ = 9.27 nM) with excellent selectivity (SI₅₀ > 10,787), proving to be a promising candidate for anti-HBV drug development.

Mapping Adverse Outcome Pathways for Kidney Injury as a Basis for the Development of Mechanism-Based Animal-Sparing Approaches to Assessment of Nephrotoxicity

In line with recent OECD activities on the use of AOPs in developing Integrated Approaches to Testing and Assessment (IATAs), it is expected that systematic mapping of AOPs leading to systemic toxicity may provide a mechanistic framework for the development and implementation of mechanism-based in vitro endpoints. These may form part of an integrated testing strategy to reduce the need for repeated dose toxicity studies. Focusing on kidney and in particular the proximal tubule epithelium as a key target site of chemical-induced injury, the overall aim of this work is to contribute to building a network of AOPs leading to nephrotoxicity. Current mechanistic understanding of kidney injury initiated by 1) inhibition of mitochondrial DNA polymerase γ (mtDNA Polγ), 2) receptor mediated endocytosis and lysosomal overload, and 3) covalent protein binding, which all present fairly well established, common mechanisms by which certain chemicals or drugs may cause nephrotoxicity, is presented and systematically captured in a formal description of AOPs in line with the OECD AOP development programme and in accordance with the harmonized terminology provided by the Collaborative Adverse Outcome Pathway Wiki. The relative level of confidence in the established AOPs is assessed based on evolved Bradford-Hill weight of evidence considerations of biological plausibility, essentiality and empirical support (temporal and dose-response concordance).

Antiretroviral Therapy in Children and Adolescents: A Look Into Modern Single Tablet Regimens

Single tablet regimens (STRs) have simplified antiretroviral therapy (ART) over the years in the adult human immunodeficiency virus (HIV) population. However, there is still a prevalent need to simplify regimens in children and adolescents living with HIV. Finding the optimal regimen requires a multi-factorial approach due to their complex pharmacokinetic profiles throughout childhood and the challenges and limitations of medication non-adherence in the pediatric population. These challenges include pill size, available formulations, palatability, and caregiver health literacy, which can all affect the proper administration of medications. The complexity of this population implies the importance of customizing everyone's antiretroviral regimen so that the patient and family can successfully adhere to the therapy. The current recommendations for ART in the adult and pediatric populations are similar, yet the use of STRs are limited. The goal of this review was to assess current data on available STRs and determine their utility as ART in the pediatric population.

Real-World Single-Center Comparison of the Safety and Efficacy of Entecavir, Tenofovir Disoproxil Fumarate, and Tenofovir Alafenamide in Patients with Chronic Hepatitis B

INTRODUCTION

Chronic hepatitis B (CHB) is a major cause of chronic liver diseases and tenofovir disoproxil fumarate (TDF), tenofovir alafenamide (TAF), and entecavir (ETV) are recommended as primary treatments. This study aimed to evaluate the efficacy and safety of ETV, TDF, and TAF in a real-world clinical setting.

METHODS

In this retrospective cohort study, a total of 363 CHB patients who were treated with ETV (n = 163), TDF (n = 154), or TAF (n = 46) from July 2007 to September 2019 were enrolled.

RESULTS

Median patient age was 51 years and 66.4% of patients were male. Median duration of treatment with ETV, TDF, or TAF was 49.0 months (interquartile range, 27.0-74.0 months). In terms of safety, cholesterol was mildly increased in the ETV and TAF groups and significantly lowered in the TDF group than baseline (p < 0.001). There was no significant difference in liver cirrhosis-related complications among the 3 groups at 48 weeks (p = 0.235). Hepatitis B e antigen seroconversion, complete virological response, and alanine aminotransferase normalization at 48 weeks as measures of treatment efficacy were not significantly different among the 3 groups (p = 0.142, 0.538, and 0.520, respectively). There was also no significant difference in cumulative incidence rate of hepatocellular carcinoma (HCC) between the ETV and TDF groups (p = 0.894).

CONCLUSIONS

ETV, TDF, and TAF were safe antiviral agents and showed similar antiviral effect for CHB at 48 weeks. Cirrhosis-related complications and annual HCC incidence rates did not differ significantly between the ETV and TDF groups over the 48 week follow-up period.

Prognostic model for nephrotoxicity among HIV-positive Zambian adults receiving tenofovir disoproxil fumarate-based antiretroviral therapy

Persons living with HIV (PLWH) receiving tenofovir disoproxil fumarate (TDF)-based antiretroviral therapy (ART) risk suffering TDF-associated nephrotoxicity (TDFAN). TDFAN can result in short- and long-term morbidity, including permanent loss of kidney function, chronic kidney disease (CKD), and end-stage kidney disease (ESKD) requiring dialysis. Currently, there is no model to predict this risk or discern which patients to initiate TDF-based therapy. Consequently, some patients suffer TDFAN within the first few months of initiating therapy before switching to another suitable antiretroviral or a lower dose of TDF. In a prospective observational cohort study of adult Zambian PLWH, we modelled the risk for TDFAN before initiating therapy to identify individuals at high risk for experiencing AKI after initiating TDF-based therapy. We enrolled 205 HIV-positive, ART-naïve adults initiating TDF-based therapy followed for a median of 3.4 months for TDFAN at the Adult Infectious Disease Research Centre (AIDC) in Lusaka, Zambia. We defined TDFAN as meeting any of these acute kidney disease (AKD) criteria: 1) An episode of estimated glomerular filtration rate (eGFR)< 60ml/ min/1.73m2 within 3 months, 2) reduced eGFR by> 35% within 3 months or 3) increased serum creatinine by> 50% within 3 months. A total of 45 participants (22%) developed acute kidney disease (AKD) after TDF-based therapy. The development of AKD within the first 3 months of commencing TDF-based therapy was associated with an increase in baseline serum creatinine, age, baseline eGFR and female sex. We concluded that baseline characteristics and baseline renal function biomarkers predicted the risk for AKD within the first 3-months of TDF-based therapy.

Prevalence of kidney injury in patients taking tenofovir based antiretroviral therapy at a primary health care clinic, in East Rand,Gauteng Province

Background: Tenofovir disoproxil fumarate (TDF) is currently one of the key medicines in the management of HIV-1 infection across the globe. Conversely, various studies indicate that TDF is associated with an increased risk of kidney injury. Furthermore, data from different studies indicate that clinically significant TDF-related kidney toxicity is uncommon, with an estimated incidence of reduction in creatinine clearance to below 50 ml/min ranging from 3% to 8%.Objective: This study investigated the prevalence of TDF-induced kidney injury, risk factors associated with the exacerbation of kidney injury, and reversibility of TDF-induced kidney injury in a South African cohort.Methods: A retrospective cross-sectional descriptive study was conducted, where quantitative data were collected through patient file reviews. Files of 600 patients initiated on TDF-based antiretroviral therapy (ART) were reviewed. The degree of kidney function was monitored using the eGFR at baseline, 3, 6, 12, and 36 months of TDF therapy. eGFR after TDF discontinuation was monitored to determine its reversibility. HIV parameters (CD4 count and viral load) were monitored to determine patients' immune response to treatment throughout the study. Comorbidities and other factors that affect kidney function were extracted from the patients' files.Results: Final sample comprised 413 files, 272 (65.9%) were females. Significant variability in the eGFR overtime was observed; 20 (5.9%) experienced mild-moderate kidney injury, four (1.2%) developed moderate-severe kidney injury and three (1%) had severe kidney injury. Significant association with decline in eGFR included high viral load, low CD4 count and long duration of treatment. Six (1.5%) patients were discontinued from TDF treatment and five patients of those fully recovered.Conclusions: TDF-induced kidney injury was uncommon in this setting and where it occurred was associated with full reversibility after discontinuation. Therefore, lack of resources in health-care settings in terms of frequent monitoring of renal function should not prevent prescribing TDF-based therapy.

Tenofovir alafenamide does not inhibit mitochondrial function and cholesterol biosynthesis in human T lymphoblastoid cell line

In clinical trials, the concentration of tenofovir diphosphate (TFV-DP) in peripheral mononuclear cells was 4 to 5-fold higher in individuals treated with tenofovir alafenamide (TAF) compared to individuals treated with tenofovir disoproxil fumarate (TDF). We hypothesized that the higher intracellular accumulation of TFV-DP could cause mitochondrial toxicity from either polymerase gamma (Pol-γ)-dependent or Pol-γ-independent mechanism(s). To test this hypothesis, we cultured human T lymphoblastoid cell line (CEM cells) for up to 12 days with TAF or TDF (multiplicities of C_max) to investigate the effects on mitochondrial function and respiration, and cholesterol biosynthesis. Both TAF and TDF treatments had no significant effect on cell growth, mitochondrial potential (ΔΨ), production of reactive oxygen species (ROS), and mitochondrial respiratory parameters. TAF had no statistically significant effect on expression of Pol-γ mRNA, mitochondria DNA (mtDNA) content, expression of proteins of the electron transport chain (ETC), and key genes of cholesterol biosynthesis. TDF had significant reduction in mtDNA content at 8xC_max, and statistically significant reduction in mRNA expression of squalene epoxidase (SQLE). Our findings do not support our hypothesis that the higher intracellular accumulation of TFV-DP in cells treated with TAF could cause mitochondrial dysfunction. In conclusion, our findings add to the emerging data that TAF may have a low potential for causing mitochondrial toxicity in HIV-infected individuals on TAF-containing regimens.

COVID-19: Therapeutics and Their Toxicities

SARS-CoV-2 is a novel coronavirus that emerged in 2019 and is causing the COVID-19 pandemic. There is no current standard of care. Clinicians need to be mindful of the toxicity of a wide variety of possibly unfamiliar substances being tested or repurposed to treat COVID-19. The United States Food and Drug Administration (FDA) has provided emergency authorization for the use of chloroquine and hydroxychloroquine. These two medications may precipitate ventricular dysrhythmias, necessitating cardiac and electrolyte monitoring, and in severe cases, treatment with epinephrine and high-doses of diazepam. Recombinant protein therapeutics may cause serum sickness or immune complex deposition. Nucleic acid vaccines may introduce mutations into the human genome. ACE inhibitors and ibuprofen have been suggested to exacerbate the pathogenesis of COVID-19. Here, we review the use, mechanism of action, and toxicity of proposed COVID-19 therapeutics.

An Improved Vascularized, Dual-Channel Microphysiological System Facilitates Modeling of Proximal Tubular Solute Secretion

A vascularized human proximal tubule model in a dual-channel microphysiological system (VPT-MPS) was developed, representing an advance over previous, single-cell-type kidney microphysiological systems. Human proximal tubule epithelial cells (PTECs) and human umbilical vein endothelial cells (HUVECs) were cocultured in side-by-side channels. Over 24 h of coculturing, PTECs maintained polarized expression of Na+/K+ ATPase, tight junctions (ZO-1), and OAT1. HUVECs showed the absence of ZO-1 but expressed endothelial cell marker (CD-31). In time-lapse imaging studies, fluorescein isothiocyanate (FITC)-dextran passed freely from the HUVEC vessel into the supporting extracellular matrix, confirming the leakiness of the endothelium (at 80 min, matrix/intravessel fluorescence ratio = 0.2). Dextran-associated fluorescence accumulated in the matrix adjacent to the basolateral aspect of the PTEC tubule with minimal passage of the compound into the tubule lumen observed (at 80 min, tubule lumen/matrix fluorescence ratio = 0.01). This demonstrates that the proximal tubule compartment is the rate-limiting step in the secretion of compounds in VPT-MPS. In kinetic studies with radiolabeled markers, p-aminohippuric acid (PAH) exhibited greater output into the tubule lumen than did paracellular markers mannitol and FITC-dextran (tubule outflow/vessel outflow concentration ratio of 7.7% vs 0.5 and 0.4%, respectively). A trend toward reduced PAH secretion by 45% was observed upon coadministration of probenecid. This signifies functional expression of renal transporters in PTECs that normally mediate the renal secretion of PAH. The VPT-MPS holds the promise of providing an in vitro platform for evaluating the renal secretion of new drug candidates and investigating the dysregulation of tubular drug secretion in chronic kidney disease.

Hepatitis B and renal function: A matched study comparing non-hepatitis B, untreated, treated and cirrhotic hepatitis patients

BACKGROUND & AIM

Renal impairment is associated with chronic hepatitis B (CHB). To overcome prior study design differences, we used propensity score matching to balance the non-CHB and CHB cohorts and generalized linear modelling (GLM, models using probit and logit linking functions for complex models) to evaluate the effect of CHB, treatment and cirrhosis on renal function.

METHODS

A retrospective cohort (1996-2017) from one U.S. university medical centre. Included patients had ≥12 months of serial creatinine laboratories and a baseline estimated glomerular filtration rate (eGFR, by the Modification of Diet in Renal Disease Study equation) ≥60 mL/min/1.73 m² . Propensity score matching was performed using age, sex, ethnicity, diabetes, hypertension and baseline eGFR. GLM was performed to generate adjusted mean eGFR over time.

RESULTS

Adjusted mean eGFR was significantly higher for non-CHB vs. untreated CHB patients (eGFR 87.4 vs. 85.6, P= 0.004, n = 580, median follow-up = 82 months). A significant difference in adjusted mean eGFR between untreated vs. entecavir (ETV)-treated CHB patients (eGFR 85.1 vs. 83.5, P= 0.02, n = 340, median follow-up = 70 months) was found among non-cirrhotic CHB. Among treated CHB, there was no difference in adjusted mean eGFR between non-cirrhotic vs. cirrhotic patients (eGFR 77.0 vs. 76.5; P= 0.66, n = 112, median follow-up = 58 months).

CONCLUSION

After PSM and GLM, the significant predictors for worsening renal function were age, hypertension and diabetes mellitus but not CHB, ETV or cirrhosis. However, given small sample size, data regarding the use of ETV in patients with cirrhosis should be interpreted with caution and requires additional investigation.

Dual antiretroviral therapy with tenofovir (TDF) and darunavir/ritonavir (DRV/RTV) in an HIV-1 positive patient: a case report, review, and meta-analysis of the literature on dual treatment strategies using protease inhibitors in combination with an NRTI

BACKGROUND

Here, we report the case of an HIV positive patient under a dual antiretroviral drug regimen with tenofovir disoproxil and darunavir/ritonavir with stable clinical, virological, and immunological response over 126 weeks. Dual antiretroviral therapy has the advantage of reduced toxicity and lower health care costs, treatment failure and fostering drug resistance are perceived risks. Optimal drug combinations and indication criteria for dual treatment remain controversial. Nevertheless, first clinical trials indicate non-inferiority for combinations of nucleoside reverse transcriptase inhibitors and protease inhibitors. This case presents the combination of tenofovir disoproxil in combination with a protease inhibitor as a new potential dual treatment regimen.

METHOD

We performed a systematic literature search and meta-analysis of trials comparing dual to triple ART.

RESULTS

Literature review revealed nine studies in which dual therapy with a protease inhibitor and an NRTI was compared to triple therapy. We performed a meta-analysis of six trials that reported a 48-week follow-up. In treatment-naïve patients as well when ART switch was assessed, there was no difference in the treatment success in patients with dual ART versus triple.

CONCLUSION

We conclude that dual therapy with a protease inhibitor and NRTI is safe and effective. The use of tenofovir in dual treatment as described in our case needs to be assessed in future clinical trials.

Development and validation of an LC-MS/MS assay for tenofovir and tenofovir alafenamide in human plasma and cerebrospinal fluid

A liquid chromatography with triple quadrupole mass spectrometry method was developed and validated for the determination of tenofovir and tenofovir alafenamide concentrations in human plasma and cerebrospinal fluid. Tenofovir and tenofovir alafenamide were extracted from matrix by solid phase extraction. The dried extraction eluents were dissolved in water for LC-MS/MS analysis. Separation was achieved with a Phenomenex Synergi 4 μm Polar-RP 80A column (50 × 2 mm) with a gradient elution of 0.1% formic acid in water and acetonitrile. The total run time was 5 min. Detection of analytes was achieved using electrospray ionization (positive mode) and triple quadrupole selected reaction monitoring. Standard curve concentrations ranged from 0.5 to 500 ng/mL for the plasma assay and 0.1-50 ng/mL for the cerebrospinal fluid assay. The intra- and inter-day accuracy and precision were less than 12% in low, medium, and high quality control samples for both matrices. The validated methods were applied to the analysis of plasma and cerebrospinal fluid samples of a patient undergoing tenofovir therapy which involved the switch from Stribild^® (elvitegravir 150 mg/cobicistat 150 mg/emtricitabine 200 mg/tenofovir disoproxil fumarate 300 mg) to Genvoya^® (elvitegravir 150 mg/cobicistat 150 mg/emtricitabine 200 mg/tenofovir alafenamide 10 mg).

Complications of Treatment in Youth with HIV

While combination antiretroviral therapy allows HIV-infected patients to have life expectancies similar to that of the general population, it may also contribute to the development of co-morbidities, such as cardiovascular disease and osteoporosis. Such complications could compromise long-term quality of life, especially in HIV-infected youth whose lifetime cumulative exposure to antiretrovirals is likely to be many decades. Recent studies continue to demonstrate abnormalities associated with antiretroviral therapy, although clinical manifestations are rare in this younger population, especially with modern antiretrovirals. The purpose of this paper is to review the most recent literature on complications of treatment in youth with HIV.

Tenofovir and adefovir down-regulate mitochondrial chaperone TRAP1 and succinate dehydrogenase subunit B to metabolically reprogram glucose metabolism and induce nephrotoxicity

Despite the therapeutic success of tenofovir (TFV) for treatment of HIV-1 infection, numerous cases of nephrotoxicity have been reported. Mitochondrial toxicity has been purported as the major target of TFV-associated renal tubulopathy but the underlying molecular mechanism remains unclear. In this report, we use metabolomics and proteomics with HK-2 cells and animal models to dissect the molecular pathways underlying nephropathy caused by TFV and its more toxic analog, adefovir (ADV). Proteomic analysis shows that mitochondrial chaperone TRAP1 and mtDNA replicating protein SSBP1 were significantly down-regulated in TFV and ADV treated HK-2 cells compared with controls. Transmission electron microscopy (TEM) revealed that TFV and ADV-treated HK-2 cells had accumulated glycogen, a phenotype that was also observed in mice treated with TFV and ADV. Analysis of the proteins in TCA cycle showed succinate dehydrogenase subunit B (SDHB) was nearly depleted in glucose oxidative phosphorylation pathway however certain enzymes in the glycolysis and glycogen synthesis pathway had elevated expression in TFV and ADV-treated HK-2 cells. These results suggest that TFV and ADV may cause mitochondrial dysfunction in renal tubular cells and reprogramming of glucose metabolism. The resulting glycogen accumulation may partially contribute to TFV and ADV induced renal dysfunction.

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.

Renal and Bone Adverse Effects of a Tenofovir-Based Regimen in the Treatment of HIV-Infected Children: A Systematic Review

INTRODUCTION

Tenofovir disoproxil fumarate (TDF)-containing regimens in the treatment of HIV-infected children have safety concerns with respect to renal and bone toxicity.

OBJECTIVE

The aim of this study was to systematically review and critically appraise the literature relating to the reported renal and bone adverse effects of TDF-based regimens in the treatment of HIV-infected children from 2 to 19 years old.

METHODS

Searches were performed using the Cochrane Central Register of Controlled Trials (CENTRAL), Cumulative Index to Nursing and Allied Health Literature (CINAHL), MEDLINE, OvidSP, ScienceDirect and Web of Science databases and platforms. All primary studies involving tenofovir use in HIV-infected children were sought. Studies that involved the use of TDF for pre- and post-exposure prophylaxis, and treatment of chronic hepatitis B virus infection were excluded. Data on study characteristics, participant's characteristics, therapeutic intervention and adverse effects were extracted using a piloted tool. In addition, pharmacovigilance data from the WHO Adverse Reaction database were included.

RESULTS

We identified 19 studies that reported the presence of renal and bone adverse effects of TDF and these included a total of 1100 study participants. The reports were in distinctly heterogeneous participant groups. A total of 287 renal and bone adverse effects were reported (250 renal and 37 bone adverse effects). Approximately 238 (21.6 %) participants were affected by these adverse effects. Of these, 15 participants stopped their TDF-containing regimen due to these adverse effects. In addition, the pharmacovigilance data from the WHO Adverse Reaction database reported 101 renal and bone adverse effects for patients whose indication was HIV/AIDS.

CONCLUSION

This systematic review summarises the reports of renal and bone adverse effects of a TDF-containing regimen in the treatment of HIV-infected children. Our findings suggest that the benefits of using TDF in children need to be balanced against the potential risk of toxicity.

Nucleotide Analogue-Related Proximal Renal Tubular Dysfunction during Long-Term Treatment of Chronic Hepatitis B: A Cross-Sectional Study

Background. There have been few reports of nucleotide analogue-related renal tubular dysfunction (RTD) in CHB patients. We assessed the prevalence and presentation of nucleotide analogue-related proximal RTD. Methods. A cross-sectional study was performed in CHB patients taking nucleotide analogues. Inclusion criteria were patients who were on adefovir or tenofovir as mono- or add-on therapy with lamivudine (LAM) >1 year. Serum and urine were collected. Fractional excretion of phosphate (FEPO₄), uric acid (FEUA), and potassium was calculated. Renal losses were defined based on the criteria: protein (24-hour urine protein >150 mg), glucose (glycosuria with normoglycemia), phosphate (FEPO₄ >18%), uric acid (FEUA >15%), potassium (renal potassium losses with hypokalemia), and bicarbonate (normal gap acidosis). Subclinical and overt proximal RTD were defined when 2 and ≥3 criteria presented. Results. Ninety-two patients were enrolled. The mean duration of nucleotide analogue taking was 55.1 ± 29.6 months. Proximal RTD was found in 24 (26.1%) patients (subclinical 15 (16.3%) and overt 9 (9.8%)). The severity of RTD was associated with the duration of nucleotide analogue (P = 0.01). Conclusions. The prevalence of proximal RTD in CHB patients taking nucleotide analogues was 26%. The severity of RTD was associated with the treatment duration. Comprehensive testing is necessary for early detecting nucleotide analogue-related nephrotoxicity.

Associations between plasma tenofovir concentration and renal function markers in HIV-infected women

Background

Tenofovir disoproxil fumarate (TDF) has been associated with kidney tubular dysfunction and reduced renal function. Limited studies were performed in Europe and Asia that related plasma tenofovir (TFV) concentration with renal function; no such studies to date have been performed on Africans.

Objective

To investigate the correlation between plasma tenofovir (TFV) concentration and certain renal function markers in HIV-infected women on TDF antiretroviral therapy (ART). These markers were also compared to a HIV-uninfected control group.

Methods

HIV-infected women (n = 30) on TDF-based ART were matched with 30 controls for age and body mass index. Renal markers analysed were estimated glomerular filtration rate (eGFR), creatinine clearance (CrCl), serum creatinine, albuminuria, glucosuria, serum urea, serum uric acid, urine sodium and maximum tubular reabsorption of phosphate. Baseline eGFR and CrCl data were obtained retrospectively for the HIV-infected women. Plasma TFV was assayed using a validated HPLC-MS/MS method. Stepwise regression, Mann-Whitney test, unpaired and paired t-tests were applied in the statistical analyses.

Results

TFV concentration was independently associated with albuminuria (adjusted r² = 0.339; p = 0.001) in HIV-infected women. In the adjusted (weight) analysis, eGFR (p = 0.038), CrCl (p = 0.032) and albuminuria (p = 0.048) were significantly higher in HIV-infected compared to the uninfected women, but eGFR was abnormally high in HIV-infected women. Both eGFR (p < 0.001) and CrCl (p = 0.008) increased from baseline to follow-up in HIV-infected women.

Conclusion

Plasma TFV concentration was associated with increased albuminuria in HIV-infected women in this sub-study. Both eGFR and CrCl were increased in HIV-infected women from baseline. These findings should be confirmed in larger studies, and hyperfiltration in HIV-infected women warrants further investigation.

Tenofovir-Associated Nephrotoxicity in Children with Perinatally-Acquired HIV Infection: A Single-Centre Cohort Study

BACKGROUND AND OBJECTIVE

In 2012, tenofovir disoproxil fumarate (TDF) was approved for use in children over 2 years of age at a dose of 8 mg/kg/day, and is the WHO recommended first-line therapy for children over 10 years of age or 35 kg in weight, at 300 mg daily. Whilst postmarketing experience of paediatric TDF is limited, prior off-licence use has occurred at our centre due to its tolerability, efficacy and resistance profiles. In this article we describe a single-centre experience of TDF nephrotoxicity in children aged <16 years.

METHODS

We conducted a retrospective case-note audit of children with perinatally-acquired HIV who ever received TDF-based antiretroviral therapy.

RESULTS

From 2001 to December 2013, 70 children [39 (56 %) females] ever received TDF. Median age at the start of TDF treatment was 12 years (interquartile range 10-14). Seven (10 %) children developed asymptomatic renal tubular leak with associated hypophosphataemia (3) and hypokalaemia (1), all resulting in TDF withdrawal and biochemical resolution. Comparison of the nephrotoxic group versus the rest of the cohort showed no significant differences for age, sex, antiretroviral regimen or CD4 count. Lower weight (p = 0.05) and initial dose of TDF received (p = 0.0048) were significantly associated with TDF-induced nephrotoxicity: median dose of TDF (7.8 mg/kg/day) compared with the remainder of the cohort (6.5 mg/kg/day). Concurrent use of protease inhibitors (PIs) with TDF may be a contributing factor to the development of nephrotoxicity (odds ratio 6; 95 % CI 0.7-54; p = 0.111).

CONCLUSION

Although all children with TDF-associated nephrotoxicity had biochemical resolution on drug withdrawal, renal monitoring of children receiving TDF is important, especially with the co-administration of PIs. Postmarketing surveillance is essential in the paediatric setting.

Lipid-based nutrient supplements containing vitamins and minerals attenuate renal electrolyte loss in HIV/AIDS patients starting antiretroviral therapy: A randomized controlled trial in Zambia

BACKGROUND & AIMS

Advanced HIV infection combined with undernutrition and antiretroviral therapy (ART) places HIV/AIDS patients at high risk of electrolyte abnormalities and increased morbidity and mortality. Here, in a sub-study of a large published randomized trial, we evaluated if nutritional supplements will help curtail renal electrolyte loss in HIV/AIDS patients starting ART.

METHODS

130 malnourished HIV-positive patients referred for ART received lipid-based nutrient supplements alone (LNS, n = 63) or together with vitamins and minerals (LNS-VM, n = 67). Serum and spot urine samples were collected and assayed for creatinine, potassium, magnesium and phosphate concentrations at baseline and after 12 weeks of ART, and fractional excretion and reabsorption were calculated using standard equations.

RESULTS

Eighteen (28.6%) patients from the LNS and 16 (23.9%) from LNS-VM groups died, most during the referral interval before starting ART. Phosphate excretion at baseline, was high in both LNS (mean ± SD: 1.2 ± 0.6 mg/mg creatinine) and LNS-VM (1.1 ± 0.8 mg/mg creatinine) groups relative to normal physiological ranges. Phosphate excretion remained high in the LNS group (1.1 ± 0.41 mg/mg creatinine) but significantly decreased in the LNS-VM group (0.6 ± 0.28 mg/mg creatinine; p < 0.001) after 12 weeks of ART. This difference is probably explained by increased renal tubular reabsorption of phosphate in the LNS-VM group (88.3 ± 5.7%) compared to the LNS group (76.6 ± 8.9%). The fractional excretion of potassium (FEK) was not significantly different at baseline between the two groups (p = 0.69) but the values were above normal physiological ranges (i.e. >6.4%) reflecting renal potassium wasting. However, FEK was significantly lowered in the LNS-VM group (6.2 ± 3.4%) but not in the LNS group (12.8 ± 4.7%) after 12 weeks of ART (p < 0.001). Finally, the fractional excretion of magnesium was not significantly different between the two groups at baseline (p = 0.68) and remained unchanged within normal physiological ranges at 12 weeks of ART (p = 0.82) in both groups.

CONCLUSIONS

The LNS-VM regimen appeared to offer protection against phosphate and potassium loss during HIV/AIDS treatment. This offers potential opportunities to improve care and support of poorly nourished HIV-infected patients in resource-limited settings.

TRIAL REGISTRATION

www.pactr.org ID number: PACTR201106000300631.

Kidney-on-a-Chip Technology for Drug-Induced Nephrotoxicity Screening

Improved model systems to predict drug efficacy, interactions, and drug-induced kidney injury (DIKI) are crucially needed in drug development. Organ-on-a-chip technology is a suitable in vitro system because it reproduces the 3D microenvironment. A kidney-on-a-chip can mimic the structural, mechanical, transport, absorptive, and physiological properties of the human kidney. In this review we address the application of state-of-the-art microfluidic culturing techniques, with a focus on culturing kidney proximal tubules, that are promising for the detection of biomarkers that predict drug interactions and DIKI. We also discuss high-throughput screening and the challenges for in vitro to in vivo extrapolation (IVIVE) that will need to be overcome for successful implementation.

Cycloartenyl Ferulate Inhibits Paraquat-Induced Apoptosis in HK-2 Cells With the Involvement of ABCC1

Nephrotoxicity induced by chemicals such as paraquat (PQ) is a common clinical phenomenon; therefore, searching for drugs with renal protective effect is of a great practical significance. Our previous investigation found that cycloartenyl ferulate (CF) can antagonize the cytotoxic effect of PQ, and recent studies also revealed a variety of bioactivities of CF. However, specific molecular mechanisms underlying the protective effect of CF have not been explored yet. HPLC detection of PQ content indicated that CF reduced PQ accumulation in HK-2 cells and thereby improved cell survival. Western blot results showed that both PQ and CF did not affect the expression of ABCB1; however, while PQ suppressed the expression of ABCC1, CF upregulated ABCC1 expression and thereby reversed the inhibitory effect of PQ on ABCC1 expression. Meanwhile, HK-2 cells did not express ABCG2. When the expression of ABCC1 was knocked down with siRNA, the inhibitory effect of CF on intracellular PQ accumulation was blocked. Further flow cytometric analysis showed that while PQ significantly induced the appearance of sub-G1 apoptotic peak in cells, CF evidently inhibited apoptosis. TUNEL-DAPI double-staining also detected that PQ significantly induced the occurrence of DNA fragmentation in cells, whereas CF effectively inhibited the effect of PQ. Further results showed that ABCC1 siRNA effectively abolished the protective effect of CF on PQ-induced apoptosis. Taken together, these data demonstrated that in HK-2 cells, CF could antagonize PQ-induced toxicity with the involvement of regulatiion of ABCC1 protein expression, which provides a new strategy for treatments of nephrotoxicity.

Kidney dysfunction associated with tenofovir exposure in human immunodeficiency virus-1-infected Taiwanese patients

BACKGROUND/PURPOSE

Tenofovir disoproxil fumarate (TDF) is associated with kidney tubular dysfunction, for which the risk may vary among patients of different ethnicities. Data are limited, however, on the association between renal function changes and TDF exposure in human immunodeficiency virus (HIV)-infected Taiwanese patients.

METHODS

Medical records of HIV-infected Taiwanese patients seeking HIV care at a university hospital from 2011 to 2014 were reviewed. The change of estimated glomerular filtration rate (eGFR) was compared between patients not receiving combination antiretroviral therapy (cART) and those starting cART with or without TDF. The determinants of annual eGFR changes and factors associated with greater annual eGFR decline in TDF-exposed patients were explored.

RESULTS

A total of 775 patients were included: 140 were cART-naïve, 393 received TDF-containing cART, and 242 received cART without TDF. Compared with cART-naïve patients, the annual eGFR decline was greater in TDF-exposed patients (0.57 ± 8.6 mL/min/1.73 m² and 2.7 ± 8.9 mL/min/1.73 m², p = 0.012). The annual eGFR decline between patients receiving cART with or without TDF was similar (2.7 ± 8.9 mL/min/1.73 m² and 1.8 ± 8.3 mL/min/1.73 m², p = 0.567). Diabetes was associated with worsening eGFR decline in all studied patients. TDF exposure correlated with an additional annual eGFR decline of 2.73 mL/min/1.73 m² (95% confidence interval 0.139-5.326, p = 0.039) in patients with CD4 count < 350 cells/μL. Among TDF-exposed patients, the factors associated with annual eGFR decline of > 3 mL/min/1.73 m² were higher baseline eGFR and lower CD4 counts.

CONCLUSION

Among HIV-infected Taiwanese patients, cART exposure correlated with the decline of renal function. However, TDF-exposed patients are more likely to have prominent eGFR decline, especially those with higher baseline eGFR, advanced HIV disease, and diabetes.

Drug-induced acid-base disorders

The incidence of acid-base disorders (ABDs) is high, especially in hospitalized patients. ABDs are often indicators for severe systemic disorders. In everyday clinical practice, analysis of ABDs must be performed in a standardized manner. Highly sensitive diagnostic tools to distinguish the various ABDs include the anion gap and the serum osmolar gap. Drug-induced ABDs can be classified into five different categories in terms of their pathophysiology: (1) metabolic acidosis caused by acid overload, which may occur through accumulation of acids by endogenous (e.g., lactic acidosis by biguanides, propofol-related syndrome) or exogenous (e.g., glycol-dependant drugs, such as diazepam or salicylates) mechanisms or by decreased renal acid excretion (e.g., distal renal tubular acidosis by amphotericin B, nonsteroidal anti-inflammatory drugs, vitamin D); (2) base loss: proximal renal tubular acidosis by drugs (e.g., ifosfamide, aminoglycosides, carbonic anhydrase inhibitors, antiretrovirals, oxaliplatin or cisplatin) in the context of Fanconi syndrome; (3) alkalosis resulting from acid and/or chloride loss by renal (e.g., diuretics, penicillins, aminoglycosides) or extrarenal (e.g., laxative drugs) mechanisms; (4) exogenous bicarbonate loads: milk-alkali syndrome, overshoot alkalosis after bicarbonate therapy or citrate administration; and (5) respiratory acidosis or alkalosis resulting from drug-induced depression of the respiratory center or neuromuscular impairment (e.g., anesthetics, sedatives) or hyperventilation (e.g., salicylates, epinephrine, nicotine).

Low Incidence of Renal Dysfunction among HIV-Infected Patients on a Tenofovir-Based First Line Antiretroviral Treatment Regimen in Myanmar

BACKGROUND

Since 2004, Médecins Sans Frontières-Switzerland has provided treatment and care for people living with HIV in Dawei, Myanmar. Renal function is routinely monitored in patients on tenofovir (TDF)-based antiretroviral treatment (ART), and this provides an opportunity to measure incidence and risk factors for renal dysfunction.

METHODS

We used routinely collected program data on all patients aged ≥15 years starting first-line TDF-based ART between January 2012 and December 2013. Creatinine clearance (CrCl) was assessed at base line and six-monthly, with renal dysfunction defined as CrCl < 50 ml/min/1.73 m2. We calculated incidence of renal dysfunction and used Cox regression analysis to identify associated risk factors.

RESULTS

There were 1391 patients, of whom 1372 had normal renal function at baseline. Of these, 86 (6.3%) developed renal dysfunction during a median time of follow-up 1.14 years with an incidence rate of 5.4 per 100 person-years: 78 had CrCl between 30-50 ml/min/1.73 m2 and were maintained on TDF-based ART, but 5 were changed to another regimen: 4 because of CrCl <30 ml/min/1.73 m2. Risk factors for renal dysfunction included age ≥45 years, diagnosed diabetes, underlying renal disease, underweight and CD4 count <200 cells/mm3. There were 19 patients with baseline renal dysfunction and all continued on TDF-based ART: CrCl stayed between 30-49 ml/min/1.73 m2 in five patients while the remainder regained normal renal function.

CONCLUSIONS

In a resource-poor country like Myanmar, the low incidence of renal toxicity in our patient cohort suggests that routine assessment of CrCl may not be needed and could be targeted to high risk groups if resources permit.

Meconium Tenofovir Concentrations and Growth and Bone Outcomes in Prenatally Tenofovir Exposed HIV-Uninfected Children

BACKGROUND

Maternal tenofovir disoproxil fumarate (TDF) treatment among HIV-infected pregnant women results in fetal tenofovir (TFV) exposure. Fetal TFV toxicity was demonstrated in animals, but most clinical investigations have not observed toxicity in humans.

METHODS

We evaluated HIV-exposed, uninfected infants in the Surveillance Monitoring for Antiretroviral Therapy Toxicities cohort of the Pediatric HIV/AIDS Cohort Study whose mothers were prescribed TDF for ≥ 8 third trimester weeks. Infant dual-energy X-ray absorptiometry scans were obtained at 0-4 weeks to measure whole body bone mineral content. Meconium TFV concentrations were quantified by liquid chromatography-tandem mass spectrometry.

RESULTS

Fifty-eight TFV-exposed infants had meconium TFV quantified. Detectable concentrations were 11-48,100 ng/g; 3 infants had undetectable concentrations. Maternal TDF prescription duration ranged from 8 to 41 gestational weeks; infant gestational ages were 36-41 weeks. Meconium TFV concentrations were not correlated with TFV exposure duration or timing and did not vary by concomitant prescription of protease inhibitors. Increased meconium TFV concentrations were associated with greater gestational ages (ρ = 0.29, P = 0.03) and lower maternal plasma HIV RNA before delivery (ρ = -0.29, P = 0.04). Meconium TFV concentrations were not associated with infant weight, length (n = 58) or bone mineral content (n = 49).

CONCLUSIONS

For the first time, we explored associations between meconium TFV concentrations and infant growth and bone measurements; we did not observe a meconium concentration-dependent relationship for these infant outcomes. These findings support other clinical research failing to show dose-response relationships for growth and bone outcomes among intrauterine TFV-exposed infants. High meconium TFV concentrations correlated with low maternal viral load, suggesting maternal TDF adherence significantly contributes to meconium TFV concentrations.

Trend of eGFR in an Italian cohort of mother-to-child HIV-infected patients exposed to tenofovir for at least 2 years

The aim of this study is to describe longitudinal changes in estimated glomerular filtration rate (eGFR) in a cohort of mother-to-child HIV-infected adolescents exposed to tenofovir dixoproxil fumarate (TDF) for at least 2 years. We retrospectively examined eGFR at starting TDF (T0), at 24 months (T2) and at the final assessment (T3). Twenty-nine patients were studied. The mean duration of TDF exposure was 67 months (24-123). At baseline, the mean eGFR was 152 ml/min/1.73 m(2) (105-227, SD, 33). There was a significant decrease of eGFR from a mean of 152 ml/min/1.73 m(2) (SD, 33) at T0 to 140 ml/min/1.73 m(2) (SD, 33) at T2 and 123 ml/min/1.73 m(2) (SD, 14) at T3. The decrease of eGFR was significant, with ΔGFR (T3-T0) of -29 ml/min/1.73 m(2) (SD, 30; p < 0.0001) and a mean ΔGFR per year of -6 and ml/min/1.73 m(2) (SD, 8).

CONCLUSION

We noted a long-term decline in eGFR in this small cohort of mother-to-child HIV-infected adolescents receiving TDF-containing cART, even if the lack of a control group and the small sample size are major limitations.

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

Tenofovir (TFV) is eliminated by renal excretion, which is mediated through multidrug-resistant protein 2 (MRP2) and MRP4, encoded by ABCC2 and ABCC4, respectively. Genetic polymorphisms of these transporters may affect the plasma concentrations of tenofovir. Therefore, the aim of this study was to investigate the influence of genetic and nongenetic factors on tenofovir plasma concentrations. A cross-sectional study was performed in Thai HIV-infected patients aged ≥18 years who had been receiving tenofovir disoproxil fumarate at 300 mg once daily for at least 6 months. A middose tenofovir plasma concentration was obtained. Multivariate analysis was performed to investigate whether there was an association between tenofovir plasma concentrations and demographic data, including age, sex, body weight, estimated glomerular filtration rate (eGFR), hepatitis B virus coinfection, hepatitis C virus coinfection, duration of tenofovir treatment, concomitant use of ritonavir-boosted protease inhibitors, and polymorphisms of ABCC2 and ABCC4. A total of 150 Thai HIV-infected patients were included. The mean age of the patients was 43.9 ± 7.2 years. The mean tenofovir plasma concentration was 100.3 ± 52.7 ng/ml. In multivariate analysis, a low body weight, a low eGFR, the concomitant use of ritonavir-boosted protease inhibitors, and the ABCC4 4131T → G variation (genotype TG or GG) were independently associated with higher tenofovir plasma concentrations. After adjusting for weight, eGFR, and the concomitant use of ritonavir-boosted protease inhibitors, a 30% increase in the mean tenofovir plasma concentration was observed in patients having the ABCC4 4131 TG or GG genotype. Both genetic and nongenetic factors affect tenofovir plasma concentrations. These factors should be considered when adjusting tenofovir dosage regimens to ensure the efficacy and safety of a drug. (This study has been registered at ClinicalTrials.gov under registration no. NCT01138241.).

Twenty-eight day safety, antiviral activity, and pharmacokinetics of tenofovir alafenamide for treatment of chronic hepatitis B infection

BACKGROUND & AIMS

Tenofovir alafenamide, a phosphonate prodrug of tenofovir with greater plasma stability than tenofovir disoproxil fumarate, provides efficient delivery of active drug to hepatocytes at reduced systemic tenofovir exposures.

METHODS

Non-cirrhotic, treatment-naïve subjects with chronic hepatitis B were randomized (1:1:1:1:1) to receive tenofovir alafenamide 8, 25, 40, or 120 mg, or tenofovir disoproxil fumarate 300 mg for 28 days and assessed for safety, antiviral response, and pharmacokinetics, followed-up by off-treatment for 4 weeks.

RESULTS

51 subjects were randomized and all completed study treatment. Groups were generally well matched (67% male, 57% Asian, 53% HBeAg-negative, mean HBV DNA approximately 6.0 log10 IU/ml) with HBV genotypes reflective of the population. No subject experienced an adverse event that was serious or severe (grade 3/4). Across the tenofovir alafenamide groups, similar mean changes in serum HBV DNA were found at Week 4 (-2.81, -2.55, -2.19, and -2.76 log10 IU/ml for the 8, 25, 40, and 120 mg groups, respectively) which were also comparable to the control (-2.68 log10 IU/ml for tenofovir disoproxil fumarate 300 mg). Kinetics of viral decline were also similar among groups. Tenofovir alafenamide pharmacokinetics were linear and proportional to the dose; doses⩽25 mg were associated with ⩾92% reductions in mean tenofovir area under the curve relative to tenofovir disoproxil fumarate 300 mg.

CONCLUSIONS

Tenofovir alafenamide was safe and well tolerated; declines in HBV DNA were similar to tenofovir disoproxil fumarate at all doses evaluated. Tenofovir alafenamide 25 mg has been selected for further hepatitis B clinical development.

Differences in nephrotoxicity risk and renal effects among anti-viral therapies against hepatitis B

BACKGROUND

Results are conflicting with respect to the renal effects of anti-viral agents used for hepatitis B virus infection.

AIM

To compare short and long-term renal effects in real-life settings and to determine risk factors for renal impairment during treatment.

METHODS

2221 treatment-naïve patients were enrolled. Among these, 895 (302 lamivudine, 27 telbivudine, 282 entecavir, 273 tenofovir and 11 adefovir initiated patients) had 'repeated measures' of creatinine (baseline, 1st, 6th, 12th and 24th month of treatment). Telbivudine and adefovir groups were excluded from further analysis because of the low number of patients. We calculated the glomerular filtration rate (GFR) using the Modification of Diet in Renal Disease (MDRD) formula at each time point. Hypophosphataemia was also recorded. Risk factors for renal impairment were analysed.

RESULTS

Tenofovir caused a decline in GFR at each time point when compared to baseline levels. However, lamivudine and entecavir did not change GFR. GFR-shifting from ≥90 to 60-89 mL/min/1.73 m(2) was comparable among groups. The proportion of patients whose baseline creatinine increased more than 25% was comparable among all anti-virals. GFR showed a decline in patients who switched from entecavir to tenofovir. One patient with compensated cirrhosis needed to change from tenofovir because of renal safety. Seven and three patients developed transient hypophosphataemia in the tenofovir and lamivudine groups, respectively.

CONCLUSIONS

Although tenofovir caused a decline in GFR, differences between the anti-viral agents do not appear to be so impressive. In patients with and without renal risk factors at baseline, there is no impact of anti-virals, including tenofovir.

Telaprevir enhances ribavirin-induced anaemia through renal function impairment

BACKGROUND

Alterations in renal function have been described with telaprevir (TVR). We examined the relationship between ribavirin (RBV) trough concentration (C), estimated glomerular filtration rate (eGFR) and severe anaemia, before and after TVR introduction in HIV-HCV-coinfected patients included in ANRS HC26 TelapreVIH study.

METHODS

69 HIV-HCV genotype-1 coinfected patients received 4 weeks of pegylated interferon (PEG-IFN)-α2a/RBV, followed by 12 weeks of TVR/PEG-IFN/RBV, then 32 to 56 weeks of PEG-IFN/RBV. RBV C was determined at week (W)4, W8 and W20/24. eGFR was estimated by the Modification of the Diet in Renal Disease (MDRD) equation. Severe anaemia was defined as haemoglobin <70 g/l, RBV dose reduction, prescription of erythropoietin or blood transfusion.

RESULTS

67 patients were analysed. eGFR remained normal between baseline (97.9 ml/min) and W4 (103.4 ml/min), declined to 86.3 ml/min at W8 (P<0.0001), stabilized until W16 and increased back to baseline level at W20 (98.4 ml/min). RBV C increased from 1.88 mg/l at W4 to 2.88 mg/l at W8 (P<0.0001), then decreased to 2.73 mg/l at week 20/24 (P=0.015). An inverse correlation was observed between W8 eGFR and W8 RBV C (r2=0.429; P=0.0005). RBV C≥3 mg/l was observed in 12% of patients at W4, 45% at W8 (P<0.0001) and 38% at W20/24 (P=0.0005). Severe anaemia was observed in 23.9% of patients at W4 and 45.3% at W8. RBV C≥3 mg/l at W8 (OR 7.7 [95% CI 2.2, 27.4]) and baseline haemoglobin <150 g/l (OR 6.4 [1.7, 23.8]) were independently associated with W8 severe anaemia.

CONCLUSIONS

Association of TVR to PEG-IFN/RBV was associated with a decrease in eGFR and increase in RBV C, leading to severe anaemia in 45% of patients.

Renal impairment in HIV-infected patients initiating tenofovir-containing antiretroviral therapy regimens in a Primary Healthcare Setting in South Africa

OBJECTIVE

Long-term use of tenofovir disoproxil fumarate is associated with declines in glomerular function and chronic kidney disease in HIV-infected patients. We aimed to assess the prevalence and incidence of renal impairment in a primary care setting in sub-Saharan Africa.

METHODS

We analysed data from 1092 HIV-infected patients initiating tenofovir at a primary care clinic in Cape Town, South Africa. Renal function was assessed for the first 12 months on ART by estimating glomerular filtration rate (eGFR) calculated using the Cockroft-Gault equation categorised into normal, mild, moderate and severe reduction in renal function based on values >90, 60-89, 30-59 and <30 ml/min/1.73 m(2) , respectively. Associations were assessed using logistic regression, and average GFR trajectory over time was modelled using linear mixed-effects models.

RESULTS

The cohort consisted of 62% women; median age was 34 years (IQR 29; 41 years). The majority had normal renal function pre-ART (79%), 19% had mildly reduced GFR, and 2% had moderate renal impairment. Older age, more advanced WHO stage and anaemia were independently associated with prevalent renal impairment. On average, estimated glomerular function improved over the first year on tenofovir [1.10 ml/min/1.73 m(2) average increase over 12 months (95% CI: 0.80; 1.40)]. Male gender, anaemia and immunosuppression (WHO Stage III/IV and CD4 cell counts <100 cells/mm(3) ) were associated with lower average eGFR levels over time. Overall, 3% developed eGFR <50 ml/min/1.73 m(2) during this period. Serum creatinine tests conducted before 4 months on ART had low predictive value for predicting change in eGFR after a year on ART.

CONCLUSION

Generally, renal function improved in HIV-infected adults initiating ART in this primary healthcare setting during the first year on ART. While monitoring of renal function is recommended in the first 4 months on ART, renal impairment appears uncommon during the first 12 months of tenofovir-containing ART in primary care populations.

Phosphate homeostasis and disorders

Recent studies of inherited disorders of phosphate metabolism have shed new light on the understanding of phosphate metabolism. Phosphate has important functions in the body and several mechanisms have evolved to regulate phosphate balance including vitamin D, parathyroid hormone and phosphatonins such as fibroblast growth factor-23 (FGF23). Disorders of phosphate homeostasis leading to hypo- and hyperphosphataemia are common and have clinical and biochemical consequences. Notably, recent studies have linked hyperphosphataemia with an increased risk of cardiovascular disease. This review outlines the recent advances in the understanding of phosphate homeostasis and describes the causes, investigation and management of hypo- and hyperphosphataemia.

First-line monotherapies of tenofovir and entecavir have comparable efficacies in hepatitis B treatment

BACKGROUND

Hepatitis B virus (HBV) infection is a health problem worldwide. Current treatment options for chronic hepatitis B (CHB) are nucleoside or nucleotide analogues and pegylated interferons. Tenofovir and entecavir are much more commonly used as they have better efficacy, tolerability, and high genetic barriers to resistance.

AIM

The aim of this study was to assess the efficacies of tenofovir and entecavir in previously untreated CHB patients in a treatment cohort.

PATIENTS AND METHODS

We included CHB patients in a cohort including previously untreated HBeAg-positive and HBeAg-negative patients from 10 centers in Istanbul, Turkey. The patients were compared in terms of baseline characteristics, decrease in alanine transaminase (ALT), decrease in HBV-DNA to undetectable levels, HBeAg loss and anti-HBe development (among baseline HBeAg-positive patients), interventions to therapy because of lack of efficacy, side effects, severe side effects, and side effects that required change in treatment.

RESULTS

The study included 121 patients who were administered tenofovir and 130 patients who were administered entecavir. The majority of patients were men, with mild to moderate histology in both treatment groups. The mean duration of follow-up was 18 and 20 months for tenofovir and entecavir, respectively. Patients receiving both drugs showed comparable rates of HBeAg loss, rates of undetectable HBV-DNA levels, rates of ALT normalization, ALT decrease, and decrease in HBV-DNA. Both drugs were well tolerated.

CONCLUSION

This study shows that although the baseline characteristics did not match, tenofovir and entecavir sustained comparable virological efficacies. More patients discontinued entecavir during follow-up. Both drugs provided effective viral control, with few side effects.

Fibroblast growth factor 23 is elevated in tenofovir-related hypophosphatemia

In human immunodeficiency virus (HIV)-infected patients, tenofovir disoproxil fumarate (TDF) may cause hypophosphatemia leading to osteomalacia due to renal phosphate wasting. Fibroblast growth factor 23 (FGF23) may play a role in this setting. We present an HIV-infected patient with TDF-induced profound hypophosphatemia, Fanconi syndrome, osteomalacia, and bilateral hip fracture. Routine serum biochemistry was assessed by standard methods. The plasma FGF23 concentration was measured at Mayo Laboratories (Scottsdale, AZ, USA). Bone mineral density (BMD) was measured using a Hologic Discovery densitometer. At presentation, the patient's plasma C-terminal FGF23 was 2,760 reference units (RU)/mL (15 times upper limit of normal; reference interval [RI] ≤ 180 RU/mL), serum phosphate was 0.58 (RI 0.8-1.6 mmol/L), and TmPO4/GFR was 95%. DXA at the lumbar spine showed a Z score of -4.0. Vitamin D3 and oral phosphate were administered, and TDF was discontinued. After 4 months off TDF, lumbar spine BMD significantly increased by 12% (Z score -3.5); by 6 months the plasma C-terminal FGF23 declined to 1.8 times the upper limit of normal, and both urine and serum phosphate levels normalized. By its marked elevation and subsequent near normalization, FGF23 may be responsible for a component of the phosphate wasting syndrome in these patients. The time course of resolution was 6 months. As expected, with calcium, vitamin D, and phosphate management, BMD significantly improved with resolution of osteomalacia. Clinicians should be aware of this side effect of TDF and the time course of its resolution.

Urine retinol-binding protein 4: a functional biomarker of the proximal renal tubule

Measurement of retinol-binding protein 4 in urine (uRBP4) is arguably the most sensitive biomarker for loss of function of the human proximal renal tubule. Megalin- and cubilin-receptor-mediated endocytosis normally absorbs > 99% of the approximately 1.5 g/24 h of protein filtered by the renal glomerulus. When this fails there is "tubular proteinuria," comprising uRBP4, albumin, and many other proteins and peptides. This tubular proteinuria is a consistent feature of the renal Fanconi syndrome (FS) and measurement of uRBP4 appears to be an excellent screening test for FS. FS occurs in rare inherited renal diseases including cystinosis, Dent disease, Lowe syndrome, and autosomal dominant FS. Acquired FS occurs in paraproteinemias, tubulointerstitial renal disease, oncogenic osteomalacia, Chinese herbs nephropathy, and Balkan endemic nephropathy. Though poorly understood, FS may be associated with HIV disease and antiretroviral treatment; cadmium poisoning may cause FS. In addition to FS, uRBP4 measurement has a different role: the early detection of acute kidney injury. Urine RBP4 comprises several isoforms, including intact plasma RBP4, MW 21.07 kDa, and C-terminal truncated forms, des-L- and des-LL-RBP4, also probably plasma derived. In FS, uRBP4 levels are about 104-fold above the upper limit of normal and small increments are frequently seen in carriers of some inherited forms of FS and in acquired disease. The very high levels in disease, frequent assay nonlinearity, lack of defined calibrants, and multiple uRBP4 isoforms make accurate assay challenging; top-down mass spectrometry has brought advances. Assays for uRBP4 with defined molecular targets allowing good interlaboratory comparisons are needed.

Low prevalence of renal dysfunction in HIV-infected pregnant women: implications for guidelines for the prevention of mother-to-child transmission of HIV

OBJECTIVE

Emerging international guidelines for the prevention of mother-to-child transmission of HIV infection across sub-Saharan Africa call for the initiation of a triple-drug antiretroviral regimen containing tenofovir, a potentially nephrotoxic agent, in all HIV-infected pregnant women at the first antenatal clinic visit. While there are significant benefits to the rapid initiation of antiretroviral therapy (ART) in pregnancy, there are few data on the prevalence of pre-existing renal disease in HIV-infected pregnant women and in turn, the potential risks of this approach are not well understood.

METHODS

We analysed data on renal function in consecutive patients eligible for ART at a large primary healthcare clinic in Cape Town. All individuals were screened for renal dysfunction via serum creatinine and estimation of creatinine clearance via the Cockroft-Gault equation.

RESULTS

Over a 2-year period, 238 pregnant women, 1014 non-pregnant women and 609 men were screened to initiate ART. Pregnant women eligible were significantly younger, in earlier stages of HIV disease, had higher CD4 cell counts and lower HIV viral loads, than non-pregnant adults. The median serum creatinine in pregnant women (46 µmol/L) was significantly lower and the median creatinine clearance (163 ml/min/1.73 m(2) ) was significantly higher than other groups (P < 0.001 and P = 0.004, respectively). Fewer than 1% of pregnant women had moderate renal dysfunction before ART initiation, with no instances of severe dysfunction observed, compared to 7% moderate or severe renal dysfunction in non-pregnant women or men (P < 0.001).

CONCLUSION

Renal dysfunction in HIV-infected pregnant women is significantly less common than in other HIV-infected adults eligible for ART. The risks associated with initiating tenofovir immediately in pregnant women before reviewing serum creatinine results may be limited, and the benefits of rapid ART initiation in pregnancy may outweigh possible risks of nephrotoxicity.