Trends in the prescription of antiretroviral drugs and impact on plasma HIV-RNA measurements

Pyruvate dehydrogenase is a potential mitochondrial off-target for gentamicin based on in silico predictions and in vitro inhibition studies

During the drug development process, organ toxicity leads to an estimated failure of one-third of novel chemical entities. Drug-induced toxicity is increasingly associated with mitochondrial dysfunction, but identifying the underlying molecular mechanisms remains a challenge. Computational modeling techniques have proven to be a good tool in searching for drug off-targets. Here, we aimed to identify mitochondrial off-targets of the nephrotoxic drugs tenofovir and gentamicin using different in silico approaches (KRIPO, ProBis and PDID). Dihydroorotate dehydrogenase (DHODH) and pyruvate dehydrogenase (PDH) were predicted as potential novel off-target sites for tenofovir and gentamicin, respectively. The predicted targets were evaluated in vitro, using (colorimetric) enzymatic activity measurements. Tenofovir did not inhibit DHODH activity, while gentamicin potently reduced PDH activity. In conclusion, the use of in silico methods appeared a valuable approach in predicting PDH as a mitochondrial off-target of gentamicin. Further research is required to investigate the contribution of PDH inhibition to overall renal toxicity of gentamicin.

CYP2B6 516 G>T polymorphism and side effects of the central nervous system in HIV-positive individuals under Efavirenz treatment: Study of a sample from southern Brazil

This study aimed to identify the 516 G>T polymorphism of the CYP2B6 gene and evaluate its influence on central nervous system (CNS) side effect development in HIV-positive individuals undergoing Efavirenz (EFV) treatment in a population from southern Brazil. Additionally, we performed a survey on the clinical and epidemiological characteristics of our sample. In addition to medical records evaluation, whole blood of 89 individuals was analyzed for viral load, T lymphocyte count (CD4+ and CD8+), and the polymorphism. Considering the side effects of the CNS reported by individuals but without considering the genetic variables, no statistically significant association was noted between the adverse effects and the antiretroviral treatment (including or not EFV). In addition, no statistically significant difference was noted for the influence of genotype on the viral load or the number of T lymphocytes (CD4+ and CD8+) among individuals undergoing EFV treatment. This is the first study that investigated the impact of the 516 G>T polymorphism of the CYP2B6 gene among HIV-positive individuals from southern Brazil. Its clinical significance indicates the need for prospective studies in this population.

Brief Report: Effects of Tenofovir and Amphotericin B Deoxycholate Coadministration on Kidney Function in Patients Treated for Cryptococcal Meningitis

The effect of tenofovir and amphotericin coadministration on kidney function is poorly characterized. We measured creatinine during induction therapy and at 4 weeks after diagnosis in Ugandans undergoing cryptococcal meningitis therapy and classified as not receiving antiretroviral therapy (ART), receiving nontenofovir ART or receiving tenofovir-based ART. Longitudinal creatinine changes and grade 2-4 creatinine adverse events were evaluated across groups. Creatinine concentrations were similar across ART groups. At 4 weeks after diagnosis, creatinine was 0.25 mg/dL higher than at diagnosis, but similar across groups. Adverse event incidence was also similar across ART groups. Tenofovir and amphotericin coadministration did not increase the risk of kidney dysfunction.

Proximal tubular dysfunction and kidney injury associated with tenofovir in HIV patients: a case series

Background

Tenofovir disoproxil fumarate (TDF) may cause acute kidney injury and proximal tubular dysfunction. However, no detailed studies document urinary phosphate wasting as a marker of TDF-induced tubulopathy.

Methods

Records of HIV-infected patients with presumed TDF toxicity were reviewed. We describe the characteristics and clinical course of 15 patients who had documented elevated (>20%) fractional excretion of phosphate (FEphos).

Results

Patients were predominantly Caucasian and male (73 and 80%, respectively), with a mean age of 56 years (range 38–76). Of the 15 patients, 11 had a estimated glomerular filtration rate (eGFR) of >90 mL/min/1.73² at time of TDF initiation. The mean duration of TDF therapy prior to diagnosis of TDF toxicity was 64 months. Mean FEphos was 34% (range 20–62). The mean eGFR at TDF initiation was 104 mL/min/1.73 m² [standard deviation (SD) 17.0] with a gradual decline to 69 mL/min/1.73 m² (SD 19.0) by the time of TDF discontinuation. Of 10 patients with repeated FEphos after TDF discontinuation, 9 had improvement of their FEphos. Of these individuals, 6 had normalization of their FEphos. Estimated GFR improved in 12 patients after discontinuation of TDF, though importantly, none returned to their baseline eGFR.

Conclusions

Urinary phosphate wasting is a sensitive marker for TDF-induced proximal tubulopathy and is associated with unrecognized and permanent renal function decline. Tubular dysfunction can develop after years of TDF therapy in those with normal kidney function at the time of drug initiation. This suggests that continuing vigilance be maintained in all those on TDF.

Changing utilization of Stavudine (d4T) in HIV-positive people in 2006-2013 in the EuroSIDA study

OBJECTIVES

The long-term side effects of stavudine (d4T) led to recommendations in 2009 to phase out use of this drug. We aimed to describe temporal patterns of d4T use across Europe.

METHODS

Patients taking combination antiretroviral therapy (cART) in EuroSIDA with follow-up after 1 January 2006 were included in the study. cART was defined as d4T-containing [d4T plus at least two other antiretrovirals (ARVs) from any class] or non-d4T-containing (at least three ARVs from any class, excluding d4T). Poisson regression was used to describe temporal changes in the prevalence of d4T use and factors associated with initiating d4T.

RESULTS

A total of 5850 patients receiving cART on 1 January 2006 were included in the current analysis, rising to 7768 patients on January 1 2013. During this time, the prevalence of d4T use fell from 11.2% to 0.7%, with an overall decline of 19% per 6 months [95% confidence interval (CI) 19-20%]. d4T use declined fastest in Northern Europe [26% (95% CI 23-29%) per 6 months], and slowest in Eastern Europe [17% (95% CI 16-19%) per 6 months]. In multivariable Poisson regression models, new d4T initiations decreased by 14% per 6 months [adjusted incidence rate ratio (aIRR) 0.86; 95% CI 0.80-0.91]. Factors associated with initiating d4T were residence in Eastern Europe (aIRR 4.31; 95% CI 2.17-9.98) versus other European regions and HIV RNA > 400 copies/mL (aIRR 3.11; 95% CI 1.60-6.02) versus HIV RNA < 400 copies/mL.

CONCLUSIONS

d4T use has declined sharply since 2006 to low levels in most regions; however, a low but persistent level of d4T use remains in Eastern Europe, where new d4T initiations post 2006 are also more common. The reasons for the regional differences may be multifactorial, but it is important to ensure that all clinicians treating HIV-positive patients are aware of the potential harmful effects associated with d4T.

Nonalbumin proteinuria predominates in biopsy-proven tenofovir nephrotoxicity

OBJECTIVE

Tenofovir disoproxil fumarate (TDF) nephrotoxicity is characterized by proximal renal tubular injury and dysmorphic mitochondria resulting in proteinuria, orthoglycemic glycosuria, and other markers of proximal tubular dysfunction. The objective of this study was to determine the pattern of proteinuria in patients with biopsy-proven TDF nephrotoxicity.

DESIGN

Retrospective chart review.

METHODS

Patients with biopsy-proven TDF nephrotoxicity were identified and their medical charts and biopsy reports were reviewed. Comparison was made with HIV-infected patients not on TDF who underwent kidney biopsy.

RESULTS

We identified 43 biopsy-proven cases of TDF nephrotoxicity; mean age 54.7 ± 0.4 years, 53% men, 42% whites. Thirty-seven cases reported proteinuria by dipstick of which only 60% had at least 2+ proteinuria. Twenty-seven patients had urine protein quantified by either 24-h collection or spot urine protein-to-creatinine ratio; median proteinuria was 1742 mg/day [interquartile range (IQR) 1200-2000 mg] and 1667 mg/g creatinine (IQR 851-1967 mg/g), respectively. Ten patients had concurrent urinary albumin measured, with a median 236 mg/g creatinine (IQR 137-343 mg/g). The mean urine albumin-to-urine protein ratio (uAPR) was 0.17 (IQR 0.14-0.19), confirming that TDF nephrotoxicity is primarily associated with nonalbumin proteinuria. Control cases had a uAPR of 0.65 (IQR 0.55-0.79) P < 0.001. Histopathology showed the predominance of proximal tubular injury with characteristic mitochondrial abnormalities.

CONCLUSION

In the largest published cohort of patients with biopsy-proven TDF nephrotoxicity, we show that low uAPR is a reliable feature of this disease. Because of the predominance of nonalbumin proteinuria, dipstick urinalysis may be unreliable in TDF nephrotoxicity.

Drug interactions and antiretroviral drug monitoring

Owing to the improved longevity afforded by combination antiretroviral therapy (cART), HIV-infected individuals are developing several non-AIDS-related comorbid conditions. Consequently, medical management of the HIV-infected population is increasingly complex, with a growing list of potential drug-drug interactions (DDIs). This article reviews some of the most relevant and emerging potential interactions between antiretroviral medications and other agents. The most common DDIs are those involving protease inhibitors or non-nucleoside reverse transcriptase inhibitors, which alter the cytochrome P450 enzyme system and/or drug transporters such as p-glycoprotein. Of note are the new agents for the treatment of chronic hepatitis C virus infection. These new classes of drugs and others drugs that are increasingly used in this patient population represent a significant challenge with regard to achieving the goals of effective HIV suppression and minimization of drug-related toxicities. Awareness of DDIs and a multidisciplinary approach are imperative in reaching these goals.

Trends in first-line antiretroviral therapy in Asia: results from the TREAT Asia HIV observational database

Background

Antiretroviral therapy (ART) has evolved rapidly since its beginnings. This analysis describes trends in first-line ART use in Asia and their impact on treatment outcomes.

Methods

Patients in the TREAT Asia HIV Observational Database receiving first-line ART for ≥6 months were included. Predictors of treatment failure and treatment modification were assessed.

Results

Data from 4662 eligible patients was analysed. Patients started ART in 2003–2006 (n = 1419), 2007–2010 (n = 2690) and 2011–2013 (n = 553). During the observation period, tenofovir, zidovudine and abacavir use largely replaced stavudine. Stavudine was prescribed to 5.8% of ART starters in 2012/13. Efavirenz use increased at the expense of nevirapine, although both continue to be used extensively (47.5% and 34.5% of patients in 2012/13, respectively). Protease inhibitor use dropped after 2004. The rate of treatment failure or modification declined over time (22.1 [95%CI 20.7–23.5] events per 100 patient/years in 2003–2006, 15.8 [14.9–16.8] in 2007–2010, and 11.6 [9.4–14.2] in 2011–2013). Adjustment for ART regimen had little impact on the temporal decline in treatment failure rates but substantially attenuated the temporal decline in rates of modification due to adverse event. In the final multivariate model, treatment modification due to adverse event was significantly predicted by earlier period of ART initiation (hazard ratio 0.52 [95%CI 0.33–0.81], p = 0.004 for 2011–2013 versus 2003–2006), older age (1.56 [1.19–2.04], p = 0.001 for ≥50 years versus <30years), female sex (1.29 [1.11–1.50], p = 0.001 versus male), positive hepatitis C status (1.33 [1.06–1.66], p = 0.013 versus negative), and ART regimen (11.36 [6.28–20.54], p<0.001 for stavudine-based regimens versus tenofovir-based).

Conclusions

The observed trends in first-line ART use in Asia reflect changes in drug availability, global treatment recommendations and prescriber preferences over the past decade. These changes have contributed to a declining rate of treatment modification due to adverse event, but not to reductions in treatment failure.

Tenofovir-induced nephrotoxicity: incidence, mechanism, risk factors, prognosis and proposed agents for prevention

OBJECTIVE

In this study, data regarding epidemiology, risk factors, pathogenesis and outcome of tenofovir-induced nephrotoxicity will be reviewed, and current and future approaches for prevention will be discussed.

METHOD

The data were collected by searching Scopus, PubMed, Medline, Science direct, Clinical trials and Cochrane database systematic reviews. The keywords used as search terms were "Tenofovir", "TDF", "NRTI", "Nephrotoxicity", "Renal failure", "Kidney damage", "HIV" and "AIDS".

RESULTS AND CONCLUSION

Several predisposing factors including elevated baseline SCr, concomitant nephrotoxic medications, low body weight, advanced age, tenofovir disoproxil fumarate (TDF) dose and duration of treatment and lower CD4 cell count were identified as risk factors for development of TDF-induced nephrotoxicity. Cellular accumulation through increased entry from the human organic anion transporters and decreased efflux into tubular lumen is main mechanism of nucleotide analogue antiviral induced nephrotoxicity. Renal function assessment and monitoring at baseline and during TDF treatment are the main approach of prevention of TDF-induced nephrotoxicity. Rosiglitazone may be helpful in patients presenting with TDF-induced nephrotoxicity. Pretreatment with melatonin prevented all known histological changes in proximal tubular mitochondira induced by TDF. Use of antioxidants with mitochondria-targeted properties such as MitoQ or Mito-CP may prevent proximal tubular mitochondrial against TDF damage. Vitamin E, ebselen, lipoic acid, plastoquinone, nitroxides, SOD enzyme mimetics, Szeto-Schiller (SS) peptides, and quercetin are other potential agents for prevention of TDF-induced nephrotoxicity. However, data regarding effectiveness of nephroprotective agents against TDF-induced nephrotoxicity are not conclusive. Before extrapolation of the preclinical evidence to clinical practice, these evidence should be confirmed in future human studies.

Long-term treatment with tenofovir: prevalence of kidney tubular dysfunction and its association with tenofovir plasma concentration

BACKGROUND

Monitoring of side effects of long-term HIV treatment has become increasingly important. Tenofovir disoproxil fumarate (TDF), a first-line treatment option, is associated with kidney tubular dysfunction (KTD). Our objective was to further investigate the prevalence and risk factors of KTD, in particular its association with TDF plasma concentration in HIV-infected patients treated with TDF for at least one year.

METHODS

An observational cross-sectional single-centre study was conducted. KTD was defined as the presence of at least two of the following criteria: urinary α1-microglobulin/creatinine ratio >15 mg/10 mmol; fractional excretion (FE) of phosphate >20% in the presence of hypophosphataemia; FE of uric acid >10% in the presence of hypouricaemia and glucosuria. Multivariate logistic regression was used to study which variable was associated with KTD.

RESULTS

A total of 161 HIV patients were included. Abnormalities in tubular function were observed in 101 patients (62.7%), while 17 patients (10.6%) fulfilled the definition of KTD. Urinary α1-microglobulin/creatinine ratio was the most sensitive parameter to detect KTD. Multivariate logistic regression showed TDF plasma concentration to be the only variable associated with KTD. Post hoc analysis showed a stronger association between the product of TDF plasma concentration and TDF exposure and KTD.

CONCLUSIONS

Parameters of KTD are frequently observed in patients on long-term TDF-containing combination antiretroviral therapy. KTD is associated with higher TDF plasma concentrations. A stronger association between the product of TDF plasma concentration and TDF exposure and KTD could suggest cumulative toxicity. A causative role for elevated TDF plasma concentration in development of KTD cannot be demonstrated in this cross-sectional analysis. Longitudinal research is needed to investigate the development and clinical relevance of KTD.

Common clinical conditions - age, low BMI, ritonavir use, mild renal impairment - affect tenofovir pharmacokinetics in a large cohort of HIV-infected women

OBJECTIVE

Tenofovir is used commonly in HIV treatment and prevention settings, but factors that correlate with tenofovir exposure in real-world settings are unknown.

DESIGN

Intensive pharmacokinetic studies of tenofovir in a large, diverse cohort of HIV-infected women over 24 h at steady state were performed and factors that influenced exposure [assessed by areas under the concentration-time curves (AUCs)] identified.

METHODS

HIV-infected women (n = 101) on tenofovir-based therapy underwent intensive 24-h pharmacokinetic sampling. Data on race/ethnicity, age, exogenous steroid use, menstrual cycle phase, concomitant medications, recreational drugs and/or tobacco, hepatic and renal function, weight, and BMI were collected. Multivariable models using forward stepwise selection identified factors associated with effects on AUC. Glomerular filtration rates (GFRs) prior to starting tenofovir were estimated by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation using both creatinine and cystatin-C measures.

RESULTS

The median (range) of tenofovir AUCs was 3350 (1031-13 911) ng × h/ml. Higher AUCs were associated with concomitant ritonavir use (1.33-fold increase, P = 0.002), increasing age (1.21-fold increase per decade, P = 0.0007), and decreasing BMI (1.04-fold increase per 10% decrease in BMI). When GFR was calculated using cystatin-C measures, mild renal insufficiency prior to tenofovir initiation was associated with higher subsequent exposure (1.35-fold increase when pre-tenofovir GFR <70 ml/min, P = 0.0075).

CONCLUSION

Concomitant ritonavir use, increasing age, decreasing BMI, and lower GFR prior to tenofovir initiation as estimated by cystatin C were all associated with elevated tenofovir exposure in a diverse cohort of HIV-infected women. Clinicians treating HIV-infected women should be aware of common clinical conditions that affect tenofovir exposure when prescribing this medication.

Resistance to the most recent protease and non-nucleoside reverse transcriptase inhibitors across HIV-1 non-B subtypes

OBJECTIVES

Limited data are available on resistance to etravirine, rilpivirine, darunavir and tipranavir in patients infected with HIV-1 non-B subtypes, in which natural polymorphisms at certain positions could influence the barrier and/or pathways to drug resistance.

METHODS

FASTA format sequences from the reverse transcriptase and protease genes recorded within the Spanish Drug Resistance database (ResRIS) were examined.

RESULTS

From 8272 genotypes derived from 5930 different HIV-1 patients included in ResRIS, 5276 genotypes had complete treatment information. Overall, 85% were from antiretroviral-experienced subjects and 7.5% belonged to HIV-1 non-B subtypes: CRF02_AG, C, F and G being the most prevalent variants. For etravirine, only G190A was more prevalent in B than non-B subtypes, whereas V90I and V179E were more frequent in non-B than B subtypes. For rilpivirine, V108I and Y188I were more frequent in B than non-B subtypes, whereas V90I was more prevalent in non-B subtypes. Despite these differences, the overall prevalence of resistance did not differ significantly when comparing etravirine or rilpivirine in B versus non-B subtypes (11.3% versus 7.4%, P = 0.13, and 10.5% versus 7.4%, P = 0.23, respectively). Despite more frequent natural polymorphisms in non-B than B subtypes at tipranavir resistance positions, the prevalence of tipranavir resistance was greater in B than non-B subtypes (11% versus 4.3%, P = 0.004), reflecting a greater antiretroviral exposure in the former. Darunavir resistance did not differ significantly when comparing B and non-B subtypes (5.8% versus 5.5%, P = 0.998).

CONCLUSIONS

The rate of resistance to the most recently approved protease and non-nucleoside reverse transcriptase inhibitors is low in antiretroviral-experienced patients, regardless of the HIV-1 subtype.

Tubulointerstitial nephropathies in HIV-infected patients over the past 15 years: a clinico-pathological study

BACKGROUND AND OBJECTIVES

The therapy and outcome of HIV infection have dramatically changed over the last 15 years, resulting in a change in renal complications. This study analyzed the characteristics of HIV-infected patients and biopsy-proven tubulointerstitial nephropathies to define disease patterns and therapeutic implications.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A clinico-pathologic retrospective study of 59 consecutive renal biopsies showing predominant tubular and/or interstitial lesions in HIV-infected patients referred to the nephrology department between 1995 and 2011 was performed. HIV-associated nephropathy and vascular diseases were excluded from the study.

RESULTS

Tubulointerstitial nephropathies accounted for 26.6% of 222 native renal biopsies performed in HIV-infected patients. Two pathologic groups were analyzed, tubulopathy and interstitial nephritis, which represented 49% and 51% of tubulointerstitial nephropathies, respectively. Most patients presented with AKI (76.3%) and high-grade proteinuria (57.7%). Drug-related nephrotoxicity was the leading cause (52.5%). Alternative etiologies included infections (15.2%), dysimmune disorders (8.5%), malignancies (3.4%), and chronic (10.2%) and acute (10.2%) tubulointerstitial nephropathies of undetermined origin. Tubulopathy was strongly associated with antiretroviral drug toxicity (75.9%) and mostly caused by tenofovir (55.2%), which was associated with proximal tubular dysfunction (87.5%), overt Fanconi's syndrome (37.5%), and nephrogenic diabetes insipidus (12.5%). Interstitial nephritis was associated with a broader spectrum of pathologic lesions and etiologies.

CONCLUSIONS

In this series, tubulointerstitial nephropathies accounted for 26.6% of renal diseases in HIV-infected patients. Considering the therapeutic implications of diagnoses of drug toxicity, infection, and dysimmune syndromes, this study underscores the importance of monitoring renal parameters in HIV-infected patients and points to the relevance of kidney biopsy to allow an accurate diagnosis.

Population pharmacokinetics of lopinavir/ritonavir (Kaletra) in HIV-infected patients

BACKGROUND

A relationship between plasma concentrations and viral suppression in patients receiving lopinavir (LPV)/ritonavir (RTV) has been observed. Therefore, it is important to increase our knowledge about factors that determine interpatient variability in LPV pharmacokinetics (PK).

METHODS

The study, designed to develop and validate population PK models for LPV and RTV, involved 263 ambulatory patients treated with 400/100 mg of LPV/RTV twice daily. A database of 1110 concentrations of LPV and RTV (647 from a single time-point and 463 from 73 full PK profiles) was available. Concentrations were determined at steady state using high-performance liquid chromatography with ultraviolet detection. PK analysis was performed with NONMEM software. Age, gender, height, total body weight, body mass index, RTV trough concentration (RTC), hepatitis C virus coinfection, total bilirubin, hospital of origin, formulation and concomitant administration of efavirenz (EFV), saquinavir (SQV), atazanavir (ATV), and tenofovir were analyzed as possible covariates influencing LPV/RTV kinetic behavior.

RESULTS

Population models were developed with 954 drug plasma concentrations from 201 patients, and the validation was conducted in the remaining 62 patients (156 concentrations). A 1-compartment model with first-order absorption (including lag-time) and elimination best described the PK. Proportional error models for interindividual and residual variability were used. The final models for the drugs oral clearance (CL/F) were as follows: CL/F(LPV)(L/h)=0.216·BMI·0.81(RTC)·1.25(EFV)·0.84(ATV); CL/F(RTV)(L/h) = 8.00·1.34(SQV)·1.77(EFV)·1.35(ATV). The predictive performance of the final population PK models was tested using standardized mean prediction errors, showing values of 0.03 ± 0.74 and 0.05 ± 0.91 for LPV and RTV, and normalized prediction distribution error, confirming the suitability of both models.

CONCLUSIONS

These validated models could be implemented in clinical PK software and applied to dose individualization using a Bayesian approach for both drugs.

Nephrotoxicity of HAART

Highly active antiretroviral therapy (HAART) and other medical therapies for HIV-related infections have been associated with toxicities. Antiretroviral therapy can contribute to renal dysfunction directly by inducing acute tubular necrosis, acute interstitial nephritis, crystal nephropathy, and renal tubular disorders or indirectly via drug interactions. With the increase in HAART use, clinicians must screen patients for the development of kidney disease especially if the regimen employed increases risk of kidney injury. It is also important that patients with chronic kidney disease (CKD) are not denied the best combinations, especially since most drugs can be adjusted based on the estimated GFR. Early detection of risk factors, systematic screening for chronic causes of CKD, and appropriate referrals for kidney disease management should be advocated for improved patient care. The interaction between immunosuppressive therapy and HAART in patients with kidney transplants and the recent endorsement of tenofovir/emtricitabine by the Centers for Disease Control (CDC) for preexposure prophylaxis bring a new dimension for nephrotoxicity vigilance. This paper summarizes the common antiretroviral drugs associated with nephrotoxicity with particular emphasis on tenofovir and protease inhibitors, their risk factors, and management as well as prevention strategies.

Genetic variants of ABCC10, a novel tenofovir transporter, are associated with kidney tubular dysfunction

BACKGROUND

Tenofovir (TFV) causes kidney tubular dysfunction (KTD) in some patients, but the mechanism is poorly understood. Genetic variants in TFV transporters are implicated; we explored whether ABCC10 transports TFV and whether ABCC10 single-nucleotide polymorphisms (SNPs) are associated with KTD.

METHODS

TFV accumulation was assessed in parental and ABCC10-transfected HEK293 cells (HEK293-ABCC10), CD4(+) cells and monocyte-derived macrophages (MDMs). Substrate specificity was confirmed by cepharanthine (ABCC10 inhibitor) and small interfering RNA (siRNA) studies. Fourteen SNPs in ABCC10 were genotyped in human immunodeficiency virus-positive patients with KTD (n = 19) or without KTD (controls; n = 96). SNP and haplotype analysis was performed using Haploview.

RESULTS

TFV accumulation was significantly lower in HEK293-ABCC10 cell lines than in parental HEK293 cells (35% lower; P = .02); this was reversed by cepharanthine. siRNA knockdown of ABCC10 resulted in increased accumulation of TFV in CD4(+) cells (18%; P = .04) and MDMs (25%; P = .04). Two ABCC10 SNPs (rs9349256: odds ratio [OR], 2.3; P = .02; rs2125739, OR, 2.0; P = .05) and their haplotype (OR, 2.1; P = .05) were significantly associated with KTD. rs9349256 was associated with urine phosphorus wasting (P = .02) and β2 microglobulinuria (P = .04).

CONCLUSIONS

TFV is a substrate for ABCC10, and genetic variability within the ABCC10 gene may influence TFV renal tubular transport and contribute to the development of KTD. These results need to be replicated in other cohorts.

Differential effects of ethanol on spectral binding and inhibition of cytochrome P450 3A4 with eight protease inhibitors antiretroviral drugs

BACKGROUND

Cytochrome P450 3A4 (CYP3A4) is the most abundant CYP enzyme in the liver, which metabolizes approximately 50% of the marketed drugs including antiretroviral agents. CYP3A4 induction by ethanol and its impact on drug metabolism and toxicity is known. However, CYP3A4-ethanol physical interaction and its impact on drug binding, inhibition, or metabolism is not known, except that we have recently shown that ethanol facilitates the binding of a protease inhibitor (PI), nelfinavir, with CYP3A4. The current study was designed to examine the effect of ethanol on spectral binding and inhibition of CYP3A4 with all currently used PIs that differ in physicochemical properties.

METHODS

We performed type I and type II spectral binding with CYP3A4 at 0 and 20 mM ethanol and varying PIs' concentrations. We also performed CYP3A4 inhibition using 7-benzyloxy-4-trifluoromethylcoumarin substrate and NADPH at varying concentrations of PIs and ethanol.

RESULTS

Atazanavir, lopinavir, saquinavir, and tipranavir showed type I spectral binding, whereas indinavir and ritonavir showed type II. However, amprenavir and darunavir did not show spectral binding with CYP3A4. Ethanol at 20 mM decreased the maximum spectral change (δA(max)) with type I lopinavir and saquinavir, but it did not alter δA(max) with other PIs. Ethanol did not alter spectral binding affinity (K(D)) and inhibition constant (IC(50)) of type I PIs. However, ethanol significantly decreased the IC(50) of type II PIs, indinavir and ritonavir, and markedly increased the IC(50) of amprenavir and darunavir.

CONCLUSIONS

Overall, our results suggest that ethanol differentially alters the binding and inhibition of CYP3A4 with the PIs that have different physicochemical properties. This study has clinical relevance because alcohol has been shown to alter the response to antiretroviral drugs, including PIs, in HIV-1-infected individuals.

Incidence of liver cirrhosis in HIV-infected patients with chronic hepatitis B or C in the era of highly active antiretroviral therapy

BACKGROUND

Longitudinal assessment of liver fibrosis with transient elastometry (TE) in patients with chronic viral hepatitis is becoming routine clinical practice in many clinics, as this procedure is non-invasive, easy to perform and relatively inexpensive, allowing early detection of cirrhosis. Herein, we examine the incidence of cirrhosis, using TE assessment, in HIV-infected individuals with chronic hepatitis B or C receiving highly active antiretroviral therapy (HAART).

METHODS

A longitudinal study was performed on a cohort of HIV-infected patients with chronic hepatitis B or C who were followed since 2004 at Hospital Carlos III (Madrid, Spain) with periodic TE assessments. The primary outcome was the development of cirrhosis, defined as liver stiffness >12.5 KPa.

RESULTS

A total of 508 HIV-infected patients were examined, of whom 54 developed liver cirrhosis during a mean ±(SD) follow-up of 2.6 ±1.0 years (overall incidence was 41.13 cases per 1,000 person-years). The risk of developing cirrhosis was significantly higher in 297 HCV-RNA-positive patients (either untreated or non-responders to hepatitis C therapy) compared with 55 patients who had cleared HCV with therapy (odds ratio 3.73, 95% confidence interval 1.06-13.17; P=0.04). By contrast, the risk of developing cirrhosis was low and similar in 24 HIV-HBV-coinfected patients under long-term suppressive HBV therapy (mainly tenofovir disoproxil fumarate), 132 HIV-infected patients without chronic liver disease and those who had cleared HCV with therapy.

CONCLUSIONS

Development of liver cirrhosis in HIV-infected individuals in the HAART era is mainly associated with active HCV coinfection. The risk of developing cirrhosis is negligible in patients who cleared HCV with therapy, as well as in HIV-HBV-coinfected patients on long-term suppressive tenofovir disoproxil fumarate therapy.

Tenofovir-induced kidney disease: an acquired renal tubular mitochondriopathy

Tenofovir, used in combination with other antiretroviral agents, is an effective therapy for HIV infection. Although large clinical studies and post-marketing data support a benign renal profile for tenofovir, numerous cases of kidney injury raise concern for nephrotoxic potential. Early human studies and experimental evidence suggested that tenofovir itself was not associated with mitochondrial toxicity within the kidney. However, recent animal data demonstrate that tenofovir causes mitochondrial DNA depletion and mitochondrial toxicity. Herlitz et al. confirm the nephrotoxicity of tenofovir in humans. They describe its clinical consequences, histopathologic findings, and its mitochondrial toxicity in HIV+ patients.

Tenofovir nephrotoxicity: acute tubular necrosis with distinctive clinical, pathological, and mitochondrial abnormalities

Tenofovir, a widely prescribed antiretroviral medication for treatment of HIV-1 infection, is infrequently associated with renal dysfunction and biopsy findings of acute tubular necrosis. We examined the clinical and pathological findings in 13 cases of tenofovir nephrotoxicity (7 men and 6 women, mean age of 51.1±9.6 years). Patients received tenofovir therapy for a mean of 19.6 months (range, 3 weeks to 8 years; median 8 months). Nine patients presented with acute kidney injury, and four had mild renal insufficiency with subnephrotic proteinuria. Mean baseline serum creatinine was 1.3±0.3 mg/dl, reaching 5.7±4.0 mg/dl at the time of biopsy, with mean proteinuria of 1.6±0.3 g/day. Glycosuria was documented in seven patients, five of whom were normoglycemic. Renal biopsy revealed toxic acute tubular necrosis, with distinctive proximal tubular eosinophilic inclusions representing giant mitochondria visible by light microscopy. Electron microscopy showed mitochondrial enlargement, depletion, and dysmorphic changes. Clinical follow-up after tenofovir discontinuation was available for 11 of 13 patients (mean duration 13.6 months). Significant recovery of renal function occurred in all patients, including four who required transient hemodialysis. Our study shows that tenofovir nephrotoxicity is a largely reversible form of toxic acute tubular necrosis targeting proximal tubules and manifesting distinctive light microscopic and ultrastructural features of mitochondrial injury.

An update on the use of Atripla in the treatment of HIV in the United States

Atripla^® (Gilead Sciences Inc, Foster City, CA, USA and Bristol-Myers Squibb, New York City, NY, USA) is a coformulated single pill composed of efavirenz, emtricitabine, and tenofovir disoproxil, intended as a once-daily potent combination antiretroviral therapeutic agent. Its efficacy is equivalent to the 3 component drugs taken in a combination as single medications. The coformulated antiretroviral regimen can be quite effective in patients whose human immunodeficiency virus is sensitive to all 3 components of Atripla. However, women at risk of pregnancy, already pregnant, or nursing mothers should not take Atripla, due to the teratogenic potential of the efavirenz moiety. Adverse effects are similar to those seen with the constituent medications, including potential central nervous system effects and renal toxicity. Since its US Food and Drug administration approval, prescriptions for Atripla have increased steadily.

Trends over calendar time in antiretroviral treatment success and failure in HIV clinic populations

OBJECTIVE

Effective antiretroviral therapy (ART) has transformed the care of people with HIV, but it is important to monitor time trends in indicators of treatment success and antic future changes.

METHODS

We assessed time trends from 2000 to 2007 in several indicators of treatment success in the UK Collaborative HIV Cohort (CHIC) Study, and using national HIV data from the Health Protection Agency (HPA) we developed a model to project future trends.

RESULTS

The proportion of patients on ART with a viral load <50 HIV-1 RNA copies/mL increased from 62% in 2000 to 84% in 2007, and the proportion of all patients with a CD4 count <200 cells/microL decreased from 21% to 10%. During this period, the number of patients who experienced extensive triple class failure (ETCF) rose from 147 (0.9%) to 1771 (3.9%). The number who experienced such ETCF and had a current viral load >50 copies/mL rose fromz 118 (0.7%) to 857 (1.9%). Projections to 2012 suggest sustained high levels of success, with a continued increase in the number of patients who have failed multiple drugs but a relatively stable number of such patients experiencing viral loads >50 copies/mL. Numbers of deaths are projected to remain low.

CONCLUSIONS

There have been continued improvements in key indicators of success in patients with HIV from 2000 to 2007. Although the number of patients who have ETCF is projected to rise in the future, the number of such patients with viral loads >50 copies/mL is not projected to increase up to 2012. New drugs may be needed in future to sustain these positive trends.

HIV protease inhibitors: recent clinical trials and recommendations on use

BACKGROUND

HIV protease inhibitors (PIs) are potent antiretroviral drugs that represent a pivotal component of highly active antiretroviral therapy (HAART). PIs have evolved over the years to gain in potency, convenience, tolerability and genetic barrier to resistance.

OBJECTIVE

Updated summary of evidence-based information about the efficacy and safety of PIs on initial, simplification and rescue interventions in HIV patients.

METHODS

Review of available data reported in peer-reviewed journals, medical conferences and treatment guidelines.

RESULTS

Due to their characteristics, PIs are, and will remain, a cornerstone component in most lines of antiretroviral therapy. The antiviral activity, tolerability and convenience of PIs have improved significantly in recent years. Differences between compounds within this class may favour their use in specific situations, such as the friendly metabolic profile of atazanavir in patients with cardiovascular disease or the high genetic barrier of darunavir or tipranavir in heavily pretreated individuals with HIV.

Antiretroviral treatment in pregnancy: a six-year perspective on recent trends in prescription patterns, viral load suppression, and pregnancy outcomes

The aim of the study was to describe the recent trends in antiretroviral treatment in late pregnancy and the sociodemographic changes among pregnant women with HIV over the last 6 years. Data from the National Program on Surveillance on Antiretroviral Treatment in Pregnancy in Italy were grouped per calendar year, and changes in antiretroviral treatment, population characteristics, maternal immunovirologic status and newborn clinical parameters were analyzed. A total of 981 HIV-infected mothers who delivered between 2002 and 2008 were evaluated. The proportion of women receiving at least three antiretroviral drugs at delivery increased significantly from 63.0% in 2002 to 95.5% in 2007-2008, paralleled by a similar upward trend in the proportion of women who achieved complete viral suppression at third trimester (from 37.3 in 2002 to 80.9 in 2007-2008; p < 0.001). The co-formulation of zidovudine plus lamivudine remained the most common nucleoside backbone in pregnancy, even if a significant increase in the use of tenofovir plus emtricitabine was observed in more recent years. Starting from 2003, nevirapine prescription declined, paralleled by a significant rise in the use of protease inhibitors (PI), which were present in more than 60% of regimens administered in 2007-2008. Nelfinavir was progressively replaced by ritonavir-boosted PIs, mainly lopinavir. No significant changes in preterm delivery, Apgar score, birth weight, and birth defects were observed during the study period, and the rate of HIV transmission remained below 2%. These data demonstrate a significant evolution in the treatment of HIV in pregnancy. Constant improvements in the rates of HIV suppression were observed, probably driven by the adoption of stronger and more effective regimens and by the increasing options available for combination treatment.

Kidney tubular abnormalities in the absence of impaired glomerular function in HIV patients treated with tenofovir

BACKGROUND

Tenofovir (TDF) is the most widely prescribed antiretroviral drug. Kidney abnormalities are the main concern using the drug. As glomerular function is infrequently affected in patients treated with TDF, herein, we report the results of an extensive examination of tubular function.

METHODS

Cross-sectional study of plasma and 24 h urine markers of kidney tubulopathy (glucosuria, hyperaminoaciduria, hyperphosphaturia, hyperuricosuria and beta2-microglobulinuria) could be allocated in three groups: patients under a TDF-containing HAART; patients on HAART never exposed to TDF; and antiretroviral-naive individuals. Significant tubular damage was defined when at least two of these parameters were repeatedly present, being at least one part of the Fanconi syndrome criteria (glucosuria, hyperaminoaciduria and hyperphosphaturia). Glomerular function was assessed using creatinine clearance.

RESULTS

A total of 284 consecutive HIV patients were examined, 154 on TDF, 49 on other HAART regimens and 81 drug-naive. No significant differences in creatinine clearance were observed when comparing distinct groups. The proportion of patients with tubular damage in groups 1, 2 and 3 were 22, 6 and 12%, respectively. In a multivariate analysis [odds ratio (OR) {95% confidence interval (CI)} P], the only independent predictors of tubular dysfunction were TDF use (21.6, 4.1-113, <0.001) and older age (1.1 per year, 1.0-1.1, 0.01).

CONCLUSION

Exposure to TDF is associated with an increased risk over time of kidney tubular abnormalities in the absence of significant impaired glomerular function. Although long-term consequences of this tubulopathy are unknown, close monitoring of accelerated bone mineral loss and renal insufficiency are warranted. Periodic screening of tubular function parameters should be recommended to patients receiving TDF.

HIV-1 antiretrovirals induce oxidant injury and increase intima-media thickness in an atherogenic mouse model

A growing body of evidence suggests HIV patients are at a greater risk for developing atherosclerosis. However, clinical investigations have generated conflicting results with regard to whether antiretrovirals are independently involved in the development of HIV-associated atherosclerosis. By administering antiretrovirals in an atherogenic mouse model, we determined whether two commonly prescribed antiretrovirals, the protease inhibitor indinavir and the nucleoside reverse transcriptase inhibitor AZT, can induce premature atherosclerosis. C57BL/6 mice were administered an atherogenic diet+/-AZT, indinavir, or AZT plus indinavir for 20 weeks. Aortic intima-media thickness (IMT) and cross-sectional area (CSA) were determined. Compared to controls, treatment with AZT, indinavir or AZT plus indinavir, significantly increased aortic IMT and CSA. This suggests that antiretrovirals can directly exacerbate atherogenesis, in the absence of interaction with a retroviral infection. To elucidate the role of oxidant injury in the drug-induced initiation of atherosclerosis, a separate group of mice were treated for 2 weeks with an atherogenic diet+/-AZT, indinavir or AZT plus indinavir. Aortic reactive oxygen species (ROS) production and glutathione/glutathione disulfide (GSH/GSSG) ratios, as well as plasma levels of 8-isoprostanes (8-iso-PGF(2alpha)) and lipids were determined. At 2 weeks, aortic ROS was increased and GSH/GSSG ratios were decreased in all antiretroviral treatment groups. Plasma 8-iso-PGF(2alpha) was increased in the AZT and AZT plus indinavir-treated groups. At 20 weeks, increased ROS production was maintained for the AZT and indinavir treatment groups, and increased 8-iso-PGF(2alpha) levels remained elevated in the AZT treatment group. Cholesterol levels were moderately elevated in the AZT and AZT plus indinavir-treated groups at 2 but not 20 weeks. Conversely, indinavir treatment increased plasma cholesterol at 20 but not 2 weeks. Thus, though effects on plasma lipid levels occurred, with effects of the individual antiretrovirals variable across the treatment period, there was consistent evidence of oxidant injury across both early and late time points. Together with the known metabolic abnormalities induced by antiretrovirals, drug-induced oxidant production may contribute to the development of antiretroviral-associated atherosclerosis.

[Clinical utility of atazanavir]

Atazanavir (ATV) is a protease inhibitor (PI) in which its main qualities, compared to other PI are dosing convenience, good tolerability and excellent metabolic profile. These characteristics makes it more like a nonnucleoside than a PI, but with the increased genetic barrier common to PI. It is indicated in initial treatment, simplification treatment or a change due to toxicity and in first line rescue treatment. The administering of ATV boosted with ritonavir (300/100 mg/d) has been approved in Europe in all clinical situations. In naïve patients it has been combined with practically all the nucleoside analogue pairs and has shown to be as effective as lopinavir/ritonavir and even efavirenz. In the USA, this indication has been approved for almost 5 years and ATV has become the most prescribed PI, while the EMEA has approved it this year. ATV is an optimal drug to replace other antiretrovirals in simplification strategies or changes due to toxicity. In several studies it has been shown that, in patients with good virological control, it can LPV/r or another PI, the therapeutic efficacy being maintained, with excellent tolerance and an improved lipid profile, and decreasing the cardiovascular risk. This strategy is widely used in Spain. In this scenario some patients could benefit from non-boosted ATV treatment (400 mg/d). ATV is an effective and very attractive option in first line rescue treatments in which the virus shows little or no resistance to PI, as its simplicity and tolerability can improve problems with compliance, the main cause of therapeutic failure. In patients with moderate resistance to PI, ATV is as effective as LPV/r. The survival of patients with HIV infection is increasingly longer and factors such as tolerability, cardiovascular risk and the adaptability of the treatment to the lifestyle of the patient, become more important, therefore ATV must play an important role in the treatment of HIV-infection.