Sonia Rodriguez-Novoa

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 β2-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.

Influence of 516G>T Polymorphisms at the Gene Encoding the CYP450-2B6 Isoenzyme on Efavirenz Plasma Concentrations in HIV-Infected Subjects

We examined 516G>T polymorphisms at the gene encoding the cytochrome P450 in 100 human immunodeficiency virus-positive subjects who were receiving efavirenz (EFV). Elevated plasma EFV concentrations were found in 40% of subjects with the polymorphic homozygous genotype and 19% of subjects with the heterozygous genotype. Conversely, 20% of subjects with the wild-type genotype had subtherapeutic concentrations of EFV. CYP2B6-516 genotyping may help to identify subjects who have plasma EFV concentrations that are outside of the therapeutic range.

Genetic factors influencing atazanavir plasma concentrations and the risk of severe hyperbilirubinemia.

Background:Hyperbilirubinemia is frequently seen in patients treated with atazanavir (ATV). Polymorphisms at the uridin-glucoronosyl-transferase 1A1 (UGT1A1) and multidrug resistance 1 (MDR1) genes may influence, respectively, bilirubin and ATV plasma concentrations. Patients and methods:HIV-infected individuals receiving ATV 300 mg daily plus ritonavir 100 mg daily at one clinic were examined. ATV plasma concentrations were measured at steady state. MDR1-3435C>T and UGT1A1 polymorphisms were examined in DNA extracted from blood mononuclear cells. Results:A total of 118 patients (all Caucasian) were analysed. The median ATV plasma concentration was 465 ng/ml [interquartile range (IQR), 233–958]. MDR1-3435 genotypes were as follows: CC (32%), CT (47%) and TT (21%). CC patients showed higher ATV minimum concentration than those with CT/TT genotypes: 939 ng/ml (IQR, 492–1266) versus 376 ng/ml (IQR, 221–722) (P = 0.001). In multivariate analyses, having at least one T allele at MDR1-3435 was independently associated with lower ATV plasma concentrations (β: –427 [95% confidence interval (CI), −633 to −223]; P < 0.001). The proportion of patients with grade 3-4 hyperbilirubinemia varied with distinct UGT1A1 genotypes: 80% for 7/7, 29% for 6/7 and 18% for 6/6 (P = 0.012). In the multivariate analysis, having at least one 7 allele at UGT1A1 was independently associated with severe hyperbilirubinemia (odds ratio, 2.96; 95% CI, 1.29–6.78; P = 0.01). Conclusions:Polymorphisms at MDR1-3435 significantly influence ATV plasma concentrations, as does being Caucasian patients with CT/TT genotypes, having lower ATV levels, even using ritonavir boosting. On the other hand, although ATV plasma concentrations directly correlate with bilirubin levels, the risk of severe hyperbilirubinemia is further increased in the presence of the UGT1A1-TA7 allele.

Impairment in kidney tubular function in patients receiving tenofovir is associated with higher tenofovir plasma concentrations.

Tenofovir (TFV) is a nucleotide analogue active against HIV and hepatitis B virus. Although TFV rarely affects the glomerular function, abnormalities in the kidney tubular function appear to be quite common. The relationship between TFV exposure and kidney tubular dysfunction (KTD) was examined prospectively in 92 HIV-infected individuals. Median TFV plasma trough concentration was higher in patients with KTD than in the rest (182 vs. 106 ng/ml; P = 0.001). This dose-dependent effect further supports an involvement of TFV in KTD.

Renal toxicity associated with tenofovir use

Importance of the field: Tenofovir (TFV) is a nucleotide analogue widely used for the treatment of HIV infection. Despite its proven efficacy and safety, cases of kidney tubular dysfunction have increasingly been reported and concern exists about the risk of nephrotoxicity associated with the long-term use of TFV. Areas covered in this review: Evidences about the renal toxicity associated with TFV use as well as predictors are examined. The most relevant publications assessing TFV safety and those which have reported cases of tubular dysfunction were identified and carefully revised. What the reader will gain: Renal damage of clinical significance caused by TFV is uncommon in the short-mid-term. It occurs more frequently in subjects with underlying kidney conditions. TFV primarily results in kidney tubular dysfunction and less frequently in glomerular abnormalities. Kidney damage may progress over time under long-term TFV exposure but is reversible in most cases on drug discontinuation. Take home message: Severe renal damage associated with TFV use is uncommon and of multifactorial origin. However, mild tubular dysfunction is recognized in a substantial proportion of TFV-treated individuals and tends to increase with cumulative exposure.

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.

Influence of Liver Fibrosis Stage on Plasma Levels of Antiretroviral Drugs in HIV-Infected Patients with Chronic Hepatitis C

BACKGROUND Most antiretrovirals are metabolized in the liver, and lower dosing could be advisable in patients with severe liver insufficiency. METHODS Plasma drug levels were measured in hepatitis C virus (HCV)/human immunodeficiency virus (HIV)-coinfected patients receiving nevirapine (NVP), efavirenz (EFV), lopinavir/ritonavir (LPV/r), or atazanavir (ATV) with or without ritonavir. Liver fibrosis was measured using elastometry. RESULTS A total of 268 coinfected patients with compensated liver disease were analyzed. Mean plasma levels were 6.1 micro g/mL for NVP (35 patients), 2.8 micro g/mL for EFV (46 patients), 5.8 micro g/mL for LPV (56 patients), 0.4 micro g/mL for ATV (58 patients), and 0.7 micro g/mL for ATV/r (73 patients). Overall, drug levels were higher in patients with cirrhosis than in those without cirrhosis for EFV (median, 3.4 vs. 1.9 micro g/mL; P<.01) and NVP (median, 6.6 vs. 5.8 micro g/mL; P=.33). EFV plasma levels above the toxic threshold (>4 micro g/mL) were more frequent in patients with cirrhosis than in those without (31% vs. 3%; P<.001). The same trend was seen for NVP levels >8 micro g/mL (50% vs. 27%; P=.27). By contrast, plasma levels of protease inhibitors (PIs) did not differ significantly between patients with and those without cirrhosis. CONCLUSIONS Liver clearance of nonnucleoside reverse-transcriptase inhibitors, particularly EFV, is impaired in patients with cirrhosis. No similar effect is seen for PIs. Assessment of liver fibrosis by noninvasive tools may identify HCV/HIV-coinfected patients who might benefit from therapeutic drug monitoring to avoid drug overexposure.

Usefulness of monitoring ribavirin plasma concentrations to improve treatment response in patients with chronic hepatitis C

Ribavirin in combination with pegylated interferon alpha is the current standard treatment for chronic hepatitis C. Adequate exposure to ribavirin seems crucial for achieving the best virological response. However, anaemia is a frequent, dose-dependent limiting side effect of ribavirin use. Therefore, therapeutic drug monitoring of ribavirin plasma concentrations could be a useful tool for individualizing ribavirin dosing. Herein, we review the relationship between ribavirin plasma concentrations and both virological response and toxicity, in order to define an optimal therapeutic range for ribavirin.

Pharmacogenetics of tenofovir treatment

Tenofovir disoproxil fumarate (TDF) is a nucleotide analog used as part of HIV therapy. Its favorable profile in terms of high efficacy, low toxicity and once-daily dosing makes TDF one of the most attractive antiretroviral agents, and therefore, it is widely used. However, cases of kidney tubular dysfunction have been reported and concern exists regarding the long term use of TDF. Owing to the high interindividual variability in the presentation of kidney function abnormalities, research has recently focused on host genetic factors predisposing to TDF-associated renal dysfunction. Transporter proteins involved in the renal elimination of TDF, such as organic anion transporter 1 or multidrug resistant protein 2 or 4, seem to be involved importantly and several genetic polymorphisms in these proteins have been associated with an increased risk of kidney tubulopathy in patients treated with TDF. In this review, all relevant pharmacogenetic factors that may play a role in the risk of renal toxicity associated with the use of tenofovir are summarized.

Hepatic safety profile of raltegravir in HIV-infected patients with chronic hepatitis C

BACKGROUND Patients with chronic hepatitis C virus (HCV) infection experience antiretroviral-associated liver toxicity more frequently than HIV mono-infected persons. Herein, we report the hepatic safety profile of raltegravir in a relatively large group of HIV/HCV co-infected patients, a population that was poorly represented in the registrational studies. METHODS Prospective, observational study of all antiretroviral-experienced HIV-infected patients who initiated raltegravir from January 2006 to January 2009 at a reference HIV clinic. Clinical data, laboratory parameters and liver stiffness measured at baseline, week 4 and every 3 months thereafter were collected. Chronic hepatitis C was defined as positive serum HCV-RNA. Grade 1-4 hepatotoxicity was defined following the AIDS Clinical Trials Group definition for liver enzyme elevations (LEEs). A control group of patients who initiated protease inhibitors (PIs) or non-nucleoside reverse transcriptase inhibitors (NNRTIs) was examined similarly. RESULTS Data from 218 HIV-infected patients on raltegravir were analysed, 126 HIV mono-infected and 92 HIV/HCV co-infected patients. Any degree of LEEs occurred in 10 (7.9%) HIV mono-infected and 23 (25%) co-infected patients (relative risk 3.1; 95% confidence interval 2.9-3.4; P = 0.002). Severe hepatotoxicity (grade 3-4), however, was only seen in 3 (1.4%) patients, all co-infected with HCV. It occurred at months 1, 15 and 15, respectively. In all three subjects other reasons than raltegravir exposure most likely explained LEEs. Multivariate analysis revealed HCV co-infection as the only independent variable associated with any degree of hepatotoxicity on raltegravir (P = 0.03). Finally, the rate of LEEs in patients on raltegravir was lower than in those who were treated with PIs or NNRTIs. CONCLUSIONS LEEs are less frequent in patients treated with raltegravir than with other antiretroviral drug classes. However, HIV/HCV co-infected patients treated with raltegravir experienced LEEs more frequently than HIV mono-infected persons. In this series, LEEs in patients treated with raltegravir were uniformly mild and no cases of grade 3-4 hepatotoxicity could be directly attributed to the drug. These results reinforce the overall hepatic safety profile of raltegravir.