Lack of Evidence for an Effect of Lopinavir/Ritonavir on Tenofovir Renal Clearance

[Tenofovir nephrotoxicity]

Tenofovir is currently the only commercially available nucleotidic reverse-transcriptase inhibitor of human immunodeficiency virus (HIV). It is overall very well tolerated and is prescribed to millions of patients-without any specific monitoring in developing countries. However a significant nephrotoxicity has been described. Acute nephrotoxicity is well characterized. Tenofovir is excreted in urine by proximal tubular epithelial cells. In case of cytoplasmic accumulation, tenofovir inhibits mitochondrial DNA polymerase γ, which causes a dysfunction of the respiratory chain, and in turn an alteration of the energy-deprived cells. Fanconi syndrome is the clinical expression of tenofovir acute toxicity, with sometimes an associated acute kidney failure. These abnormalities are usually reversible, at least partially, when tenofovir is discontinued. Tenofovir chronic toxicity has been debated but seems now well established by several cohort studies, even though it pathophysiology has yet to be understood. It manifests as an accelerated glomerular filtration rate decline in treated patients with no other renal abnormalities. The identification of this chronic toxicity was probably blurred by multiple cofactors, usually excluded from clinical trials. Simple measures such as dose adaptation to kidney function, identification of risk factors, and plasmatic tenofovir concentration monitoring can help decrease the risk of nephrotoxicity.

An investigation of the pattern of kidney injury in HIV-positive persons exposed to tenofovir disoproxil fumarate: an examination of a large population database (MHRA database)

The potential for tenofovir to cause a range of kidney syndromes has been established from mechanistic and randomised clinical trials. However, the exact pattern of kidney involvement is still uncertain. We undertook a descriptive analysis of Yellow Card records of 407 HIV-positive persons taking tenofovir disoproxil fumarate (TDF) as part of their antiretroviral therapy regimen and submitted to the Medicines and Healthcare Products Regulatory Agency (MHRA) with suspected kidney adverse effects. Reports that satisfy defined criteria were classified as acute kidney injury, kidney tubular dysfunction and Fanconi syndrome. Of the 407 Yellow Card records analysed, 106 satisfied criteria for TDF-related kidney disease, of which 53 (50%) had features of kidney tubular dysfunction, 35 (33%) were found to have features of glomerular dysfunction and 18 (17%) had Fanconi syndrome. The median TDF exposure was 316 days (interquartile range 120–740). The incidence of hospitalisation for TDF kidney adverse effects was high, particularly amongst patients with features of Fanconi syndrome. The pattern of kidney syndromes in this population series mirrors that reported in randomised clinical trials. Cessation of TDF was associated with complete restoration of kidney function in up half of the patients in this report.

Tenofovir effect on the kidneys of HIV-infected patients: a double-edged sword?

Tenofovir disoproxil fumarate (TDF), the first nucleotidic inhibitor of HIV reverse transcription, became available in 2001. It has been extensively used worldwide and is now the most prescribed antiretroviral (ARV) drug. Its high antiviral activity and favorable metabolic profile are responsible for its success. Furthermore, TDF has been associated with other ARVs to form new combined antiretroviral treatments in only one tablet once-a-day, which increases treatment adherence. Fears of potential nephrotoxicity that tenofovir would have in common with two other drugs from the same family (adefovir, used to treat hepatitis B, and cidofovir, used to treat cytomegalovirus infections) were alleviated by the early clinical trials. Yet, in 2001, the first case of TDF-induced acute nephrotoxicity was published. Numerous cases have been published since then, and it is now established that TDF presents a tubular toxicity risk. Some facilitating factors have been identified, such as co-prescription of didanosine or boosted protease inhibitor, preexisting CKD, low body weight, and associated diabetes mellitus. Conversely, whether TDF is nephrotoxic in the long term is a highly debated question. Some studies suggest a decreased GFR when TDF is prescribed for a long period, while others indicate that TDF is safe for the kidneys even after many years of use. Here we review the differences in patient characteristics, study designs, and measured outcomes that can possibly explain these conflicting findings. We conclude with rational recommendation for appropriate TDF prescription.

Renal function in patients with HIV starting therapy with tenofovir and either efavirenz, lopinavir or atazanavir

BACKGROUND

Tenofovir is associated with reduced renal function, but it is not clear whether there is a greater decline in renal function when tenofovir is co-administered with a boosted protease inhibitor rather than with a nonnucleoside reverse transcriptase inhibitor (NNRTI).

METHODS

We calculated the estimated glomerular filtration rate (eGFR) for patients in the Swiss HIV Cohort Study. We estimated the difference in eGFR over time between first therapies containing tenofovir and either the NNRTI efavirenz or the protease inhibitors lopinavir (LPV/r) or atazanavir (ATV/r), both boosted with ritonavir.

RESULTS

Patients on a first therapy of tenofovir co-administered with efavirenz (n  = 484), LPV/r (n = 269) and ATV/r (n =  187) were followed for a median of 1.7, 1.2 and 1.3 years, respectively. Relative to tenofovir and efavirenz, the estimated difference in eGFR for tenofovir and LPV/r was -2.6 ml/min per 1.73 m [95% confidence interval (CI) -7.3 to 2.2) during the first 6 months of therapy, then followed by a difference of 0.0 ml/min per 1.73 m (95% CI -1.1 to 1.1) for each additional 6 months of therapy. Relative to tenofovir and efavirenz, the estimated difference in eGFR for tenofovir and ATV/r was -7.6 ml/min per 1.73 m (95% CI -11.8 to -3.4) during the first 6 months of therapy, then followed by a difference of -0.5 ml/min per 1.73 m (95% CI -1.6 to 0.7) for each additional 6 months of therapy.

CONCLUSION

Tenofovir with either boosted protease inhibitor leads to a greater initial decline in eGFR than tenofovir with efavirenz; this decline may be worse with ATV/r than with LPV/r.

Estimated glomerular filtration rate, chronic kidney disease and antiretroviral drug use in HIV-positive patients

OBJECTIVES

Chronic kidney disease (CKD) in HIV-positive persons might be caused by both HIV and traditional or non-HIV-related factors. Our objective was to investigate long-term exposure to specific antiretroviral drugs and CKD.

DESIGN

A cohort study including 6843 HIV-positive persons with at least three serum creatinine measurements and corresponding body weight measurements from 2004 onwards.

METHODS

CKD was defined as either confirmed (two measurements >or=3 months apart) estimated glomerular filtration rate (eGFR) of 60 ml/min per 1.73 m or below for persons with baseline eGFR of above 60 ml/min per 1.73 m or confirmed 25% decline in eGFR for persons with baseline eGFR of 60 ml/min per 1.73 m or less, using the Cockcroft-Gault formula. Poisson regression was used to determine factors associated with CKD.

RESULTS

Two hundred and twenty-five (3.3%) persons progressed to CKD during 21 482 person-years follow-up, an incidence of 1.05 per 100 person-years follow-up [95% confidence interval (CI) 0.91-1.18]; median follow-up was 3.7 years (interquartile range 2.8-5.7). After adjustment for traditional factors associated with CKD and other confounding variables, increasing cumulative exposure to tenofovir [incidence rate ratio (IRR) per year 1.16, 95% CI 1.06-1.25, P < 0.0001), indinavir (IRR 1.12, 95% CI 1.06-1.18, P < 0.0001), atazanavir (IRR 1.21, 95% CI 1.09-1.34, P = 0.0003) and lopinavir/r (IRR 1.08, 95% CI 1.01-1.16, P = 0.030) were associated with a significantly increased rate of CKD. Consistent results were observed in wide-ranging sensitivity analyses, although of marginal statistical significance for lopinavir/r. No other antiretroviral drugs were associated with increased incidence of CKD.

CONCLUSION

In this nonrandomized large cohort, increasing exposure to tenofovir was associated with a higher incidence of CKD, as was true for indinavir and atazanavir, whereas the results for lopinavir/r were less clear.

Renal function with use of a tenofovir-containing initial antiretroviral regimen

OBJECTIVES

To determine whether tenofovir disoproxil fumarate (TDF) is associated with renal dysfunction when used as part of an initial antiretroviral regimen and to assess the effect of ritonavir-boosted protease inhibitor (PI/r) coadministration on renal function in TDF-treated patients.

DESIGN

Analysis from a prospective observational cohort.

METHODS

: We compared all antiretroviral-naive patients with an estimated glomerular filtration rate (eGFR) of more than 50 ml/min per 1.73 m (modification of diet in renal disease equation) who initiated either TDF (n = 201) or any alternative nucleoside reverse transcriptase inhibitor (NRTI) (n = 231) after 1 January 2002.

RESULTS

Patients taking both TDF and NRTIs experienced an initial decline in eGFR during the first 180 days of therapy, but eGFR stabilized between 180 and 720 days. There was no difference between TDF and NRTI use in 25 or 50% decline in eGFR at 1 or 2 years or in change in eGFR at 6, 12, or 24 months. Those taking TDF and a PI/r had a greater median decline in eGFR than those taking TDF and a non-NRTI at 6 months (P = 0.01), with trends at 12 (P = 0.08) and 24 months (P = 0.08). There was no difference in median GFR decline between those on an NRTI and PI/r vs. an NRTI and non-NRTI.

CONCLUSION

Our data are consistent with results of clinical trials, which have shown no evidence of renal toxicity when TDF is used as part of an initial regimen. Our results support the use of TDF as a component of the initial antiretroviral regimen, and suggest that the eGFR should be monitored more closely when TDF is used with a PI/r.