Tenofovir treatment at 30 mg/kg/day can inhibit cortical bone mineralization in growing rhesus monkeys (Macaca mulatta)

Effects of Tenofovir Disoproxil Fumarate on Bone Quality beyond Bone Density-A Scoping Review of the Literature

Tenofovir disoproxil fumarate (TDF) is a widely used pharmacological agent for the treatment of human immunodeficiency virus infection. While prolonged exposure to TDF has been associated with a decrease in bone mineral density (BMD) and increased fracture risk, limited discussion exists on its effects on various aspects of bone quality. This scoping review aims to provide a comprehensive overview of the impact of TDF on bone quality beyond BMD. A literature search was conducted using the PubMed and Scopus databases to identify studies investigating the effects of TDF on bone quality. Original research articles written in English, irrespective of study type or publication year, were included in the review. Seven articles met the inclusion criteria. Findings indicate that prolonged exposure to TDF adversely affects bone microarchitecture and strength, impeding fracture healing and skeletal microdamage repair. The observed effects suggest a complex interplay involving bone cell signalling, cytokines and bone remodelling processes as potential mechanisms underlying TDF's impact on bone quality. As a conclusion, TDF impairs bone remodelling and microarchitecture by influencing dynamic bone cell behaviour and signalling pathways. Future studies should delve deeper into understanding the intricate negative effects of TDF on bone and explore strategies for reversing these effects.

Juvenile Bone Toxicity: Study Considerations, Regulations, and Techniques for Assessment

Recommendations on study designs that adequately evaluate the in-life effects leading to juvenile bone toxicity, the various imaging modalities that can aid interpretation of the bone effects, biomarkers that may be useful, and regulatory issues were presented in this 2020 ACT symposium. The pathologies encountered in past studies were briefly mentioned. The first speaker covered study design and the numbers of juveniles that may be necessary to power the evaluation. Changes in the International Council for Harmonisation (IHC) guidelines were reviewed. The second speaker launched the rest of the symposium by describing the tools that may help assess juvenile bone toxicity, specifically those used to monitor bone toxicity, healing, and remodeling as they relate or drive the study design including model, species selection, and age. The third speaker addressed in more depth the micro-Computed Tomography (CT) applications in juvenile toxicology for evaluation of skeletal elements and bone growth in both embryo-fetal development (EFD) and pre and postnatal development (PPND) studies. Lastly, a regulatory perspective on strategies to assess juvenile bone toxicity and the concerns of the regulatory agency with respect to these potential changes in the juvenile population was addressed.

A retrospective analysis of bone loss in tenofovir-emtricitabine therapy for HIV PrEP

BACKGROUND

Tenofovir-Emtricitabine (TDF-FTC) is known to cause bone loss in about 1-3% of HIV treated patients. Current studies lack evidence in minority groups and long-term bone loss effects in PrEP patients.

SETTING

To address the risk of osteopenia/osteoporosis in patients on TDF-FTC therapy for HIV PrEP and to address the breakthrough incidence of HIV.

METHODS

A retrospective analysis was performed in Kaiser Permanente patients from 2012-2021. Patients on TDF-FTC for PrEP without any prior history of osteopenia/osteoporosis (N = 7698) were analyzed to determine the relationship between PrEP adherence and osteopenia/osteoporosis. Descriptive statistics and Cox proportional hazards model were used to compare and analyze patient characteristics between those who developed osteopenia/osteoporosis and those who didn't.

RESULTS

3% were found to have osteopenia/osteoporosis. Patients who developed osteopenia/osteoporosis were more likely to have a proportion of days covered (PDC) ratio ≥90%, older, had history of Hep B, DM, CVD, CKD, hypertension, and baseline eGFR ≥90 mL/min/1.73 m². Kaplan-Meier curve showed the event-free rate of osteopenia/osteoporosis decreased with time, with a greater reduction in patients with high adherence. Survival analysis showed only PDC of ≥90% was significantly associated with the risk of osteopenia/osteoporosis when adjusted. No incidence of HIV infection was detected.

CONCLUSIONS

This retrospective cohort analysis showed that TDF-FTC offered superior PrEP protection. Although high PrEP adherence ensured protection from HIV infection, it was significantly associated with a higher risk of developing osteopenia/osteoporosis. These findings suggest that routine check-ups for osteopenia/osteoporosis may be needed.

Bone Quality in Relation to HIV and Antiretroviral Drugs

PURPOSE OF REVIEW

People living with HIV (PLWH) are at an increased risk for osteoporosis, a disease defined by the loss of bone mineral density (BMD) and deterioration of bone quality, both of which independently contribute to an increased risk of skeletal fractures. While there is an emerging body of literature focusing on the factors that contribute to BMD loss in PLWH, the contribution of these factors to bone quality changes are less understood. The current review summarizes and critically reviews the data describing the effects of HIV, HIV disease-related factors, and antiretroviral drugs (ARVs) on bone quality.

RECENT FINDINGS

The increased availability of high-resolution peripheral quantitative computed tomography has confirmed that both HIV infection and ARVs negatively affect bone architecture. There is considerably less data on their effects on bone remodeling or the composition of bone matrix. Whether changes in bone quality independently predict fracture risk, as seen in HIV-uninfected populations, is largely unknown. The available data suggests that bone quality deterioration occurs in PLWH. Future studies are needed to define which factors, viral or ARVs, contribute to loss of bone quality and which bone quality factors are most associated with increased fracture risk.

Regulatory Perspectives on Juvenile Animal Toxicologic Pathology

The Society of Toxicologic Pathology's Annual Virtual Symposium (2021) included a session on "Regulatory Perspectives on Juvenile Animal Toxicologic Pathology." The following narrative summarizes the key concepts from the four talks included in this symposium session chaired by Drs Deepa Rao and Alan Hoberman. These encompass an overview of various global regulations impacting the conduct of juvenile animal studies in pharmaceutical drug development and chemical toxicity assessments in a talk by Dr Alan Hoberman. Given the numerous regulatory guidances and legal statutes that have covered the conduct of juvenile animal studies and the recent harmonization of these guidances for pharmaceuticals, Dr Paul Brown provided an update on the harmonization of these guidances for pharmaceuticals, in the recently finalized version of the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use S11 guidance document, "Nonclinical Safety Testing in Support of Development of Pediatric Medicines." The first two talks on regulations were followed by two talks focused on an evaluation of the postnatal development of two major organ systems relevant in juvenile animals. Dr Aurore Varela covered study design and endpoints impacting the skeletal system (bone), while Dr Brad Bolon presented a talk on the study design and conduct of neuropathology evaluations for the developing nervous system.

Tenofovir and Severe Symptomatic Hypophosphatemia

Tenofovir is a broadly used drug used for the treatment of human immunodeficiency virus (HIV). Although the initial results of the clinical trials supported the renal safety of Tenofovir, clinical use of it has caused a low, albeit a significant, risk of renal damage either in the form of AKI or CKD. The pathophysiology has been linked to the effect of this medication on the proximal tubular cell. Although the exact mechanism is unknown, studies have suggested that Tenofovir accumulates in proximal tubular cells which are rich in mitochondria. It is both filtered in the glomerulus and actively secreted in the tubules for elimination and is excreted unchanged in the urine. Studies have shown an active transportation of 20-30% of this drug into the renal proximal tubule (PCT) cells via the organic anion transporters in the baso-lateral membrane (primarily hOAT1, and OAT3 to a lesser extent) and ultimate excretion of the drug into the tubular lumen via the transporters in the proximal tubular apical membrane MRP4 and MRP2 (multidrug resistance-associated proteins 2 & 4). Subsequently, the mitochondrial injury caused by Tenofovir can lead to the development of Fanconi's syndrome which causes renal tubular acidosis, phosphaturia, aminoaciduria, glucosuria with normoglycemia, and tubular proteinuria. Here we present a case where Tenofovir treatment resulted in severe hypophosphatemia requiring hospitalization for parentral phosphate repletion.

Guides concerning tenofovir exposure via breastfeeding: A comparison of drug dosages by developmental stage

Tenofovir disoproxil fumarate (TDF) is a prodrug of tenofovir, and after being administered orally, it converts to tenofovir in the blood. With the increasing use of TDF in women for treatment and prevention of mother-to-child transmission (MTCT) of both human immunodeficiency virus (HIV) and hepatitis B virus (HBV), or the pre-exposure prophylaxis (PrEP) for HIV, many nursing mothers have to understand the risk of exposure to tenofovir via breastmilk and make the decision about breastfeeding while on TDF treatment. Despite the safety record of TDF in pregnancy, some guidelines recommend against its use during breastfeeding. In this paper, we compared the dosage levels of tenofovir exposure in fetuses, breastfed infants, and children receiving tenofovir treatment. We found that breastfed infants were exposed to only 0.5%-16% of the tenofovir dosage that fetuses experienced via placental transfer, and 0.01-0.04% of the recommended weight-adjusted therapeutic dose. The assessment of toxicity risk from the dose perspective is an important and natural way of addressing safety concerns about exposure to tenofovir via breastfeeding. Based on the safety data from fetuses and children with tenofovir exposure, and the comparatively negligible exposure dosage from breastfeeding, our study supports mothers on TDF treatment should be encouraged to breastfeed.

Osteoporosis-Related Fractures in HIV-Infected Patients Receiving Long-Term Tenofovir Disoproxil Fumarate: An Observational Cohort Study

Introduction

Patients with HIV infection may have a higher prevalence of osteoporosis and osteopenia, as well as an increased risk of bone fracture compared with non-HIV-infected individuals. Antiretroviral therapy is thought to be one of factors associated to osteoporosis-related bone fractures.

Objective

The aim of this study was to assess the effects of long-term exposure to tenofovir disoproxil fumarate (TDF) on the cumulative risk of osteoporosis-related bone fractures in Japanese patients with HIV infection.

Design

This observational cohort study comprised a joint HIV-related drug survey of patients treated with TDF between April 2004 and March 2013.

Methods

Thirty-five healthcare facilities in Japan participated in the survey. The incidence of osteoporosis-related fractures was extracted from all adverse events (AEs) using standardized Medical Dictionary for Regulatory Activities queries, and used to calculate the fracture rate per 10,000 patient-years (PY). Kaplan–Meier analysis was used to estimate the cumulative probability of fracture during the study period.

Results

A total of 3251 patients who received TDF or TDF/emtricitabine between April 2004 and March 2013 were analyzed in this study; 93.5% of patients were male. The fracture rate was 13.5 per 10,000 PY in males and 42.2 per 10,000 PY in females. The mean age for male patients with osteoporosis-related fracture was 43.2 years, whereas it was 65.7 years in female patients. The cumulative probability of osteoporosis-related fracture increased after ≥ 5 years of TDF exposure. The rate of hip fracture (95% confidence interval) was 7.2 (3.1–14.2) per 10,000 PY.

Conclusions

Among HIV-infected patients in Japan, treatment with TDF for ≥ 5 years increases the risk of bone fractures in younger men, in addition to that seen in older post-menopausal women.

Bone Toolbox: Biomarkers, Imaging Tools, Biomechanics, and Histomorphometry

Bone is a unique tissue with turnover, metabolic, and cellular activities that vary through development to aging and with a mineralized matrix in which the current state and the history of a bone coexist. Qualitative histopathology often lacks sensitivity to detect changes in bone formation, mineralization and resorption, which often requires chronic dosing to result in structural changes such as variation in bone mass and geometry. A large panel of modalities can be used to fully analyze the health of the skeleton, including biomarker evaluation in serum or urine, imaging techniques ranging from radiology to computed tomography, biomechanical testing, and undecalcified tissue processing with bone histomorphometry. The use of clinically relevant biomarkers provides an important noninvasive, sensitive, rapid, and real-time tool to monitor bone activity at the whole skeleton level when conducting safety assessments in a preclinical setting. Imaging modalities also allow in vivo longitudinal assessments with a powerful, noninvasive and clinically translatable tools to monitor drug effects. Different imaging modalities are used in the preclinical studies to evaluate the bone tissues: standard radiography, dual-energy X-ray absorptiometry, peripheral quantitative computed tomography (pQCT), micro-computed tomography, and high-resolution pQCT. Bone histomorphometry is an important tool that provides sensitive evaluation to detect effects of test articles on bone resorption, formation, mineralization, remodeling rates and growth to address a potential target- or class-related theoretical bone liability. Ultimately, the measurement of bone mechanical properties in pharmaceutical testing is critical to understand the potential effects of that pharmaceutical on bone health and fracture risk. Important considerations are required for including these different techniques in toxicology rodents and nonrodent studies, to actually integrate these into safety assessment.

Bone mineral density reductions after tenofovir disoproxil fumarate initiation and changes in phosphaturia: a secondary analysis of ACTG A5224s

Background

It is unknown if the greater reductions in bone mineral density (BMD) associated with initiation of tenofovir disoproxil fumarate compared with abacavir in previously untreated HIV-infected participants in the ACTG A5224s clinical trial were associated with potentially worsening tenofovir-related phosphaturia.

Methods

We correlated changes in BMD at the hip and spine with changes in phosphaturia [transtubular reabsorption of phosphorus (TRP) and tubular maximum phosphate reabsorption per glomerular filtration rate (TmP/GFR)] from entry through week 96 in those initiating tenofovir ( n  =   134) versus abacavir ( n  =   135) with efavirenz or atazanavir/ritonavir in A5224s. We also correlated changes in BMD with tenofovir AUC measured between weeks 4 and 24.

Results

Changes in TRP and TmP/GFR through week 96 between the tenofovir and abacavir arms were not significantly different (both P  ≥   0.70) and did not differ with use of efavirenz versus atazanavir/ritonavir. There were no significant correlations between changes in either TRP or TmP/GFR and with either hip or spine BMD in the tenofovir arms. Tenofovir AUC was significantly correlated with changes in hip BMD, but not spine BMD, at week 24 ( r  =   -0.22, P  =   0.028) and week 48 ( r  =   -0.26, P  =   0.010), but not at week 96 ( r  =   -0.14, P  =   0.18).

Conclusions

Changes in phosphaturia were not different between the tenofovir and abacavir arms in A5224s. Changes in hip and spine BMD with tenofovir were not related to changes in phosphaturia. However, tenofovir exposure was weakly associated with changes in hip BMD through week 48.

A Direct Comparison of the Effects of the Antiretroviral Drugs Stavudine, Tenofovir and the Combination Lopinavir/Ritonavir on Bone Metabolism in a Rat Model

Antiretroviral (ARV) treatment may induce metabolic complications in HIV patients on long-term therapy that can affect bone health. In this study, the effects of the ARVs Stavudine (d4T), Tenofovir (TDF) and Lopinavir/ritonavir (LPV/r) on bone metabolism and lipodystrophy were directly compared in rats to negate the consequences of HIV-associated confounding factors. Healthy 12-14-week-old male Wistar rats (n = 40) were divided into four treatment groups and received an oral animal equivalent dose of either Stavudine (6.2 mg/kg/day), TDF (26.6 mg/kg/day), LPV/r (70.8 mg/kg/day) or water (Control 1.5 mL water/day) for a period of 9 weeks. Whole-body DXA measurements, a biomechanical three-point breaking test and histomorphometric analysis were performed on the femurs and tibias at the end of the treatment period. Stavudine monotherapy was found to be associated with decreased femoral bone mineral density that translated into reduced bone strength, whereas histomorphometric analysis demonstrated that Stavudine induces an imbalance in bone metabolism at tissue level, evident in higher resorption (eroded surfaces, osteoclast surfaces and osteoclast number) and lower formation parameters (osteoblast surfaces and osteoid surfaces). This was less clear in the rats treated with either TDF or LPV/r. Furthermore, both Stavudine and TDF treatment resulted in significant bone marrow adiposity, although no significant redistribution of body fat was noted in the treated rats compared to controls. The data from this study suggest that in the absence of HIV-associated factors, LPV/r is less detrimental to bone metabolism compared to Stavudine and TDF.

Bone Age and Mineral Density Assessments Using Plain Roentgenograms in Tenofovir-exposed Infants in Malawi and Brazil Enrolled in HIV Prevention Trials Network 057

BACKGROUND

Tenofovir disoproxil fumarate (TDF) use during pregnancy has been increasing, and studies linking bone toxicity with exposure to TDF have raised concern for its use in infants.

METHODS

Hand/wrist and spine radiographs were obtained at 3 days and 12 weeks of age in infants born to HIV-infected pregnant women enrolled in the HIV Prevention Trials Network 057 pharmacokinetic study of TDF conducted in Malawi and Brazil assigned to 3 TDF dosing cohorts. In cohort 1, mothers received 600 mg of TDF during labor. In cohort 2, infants received 4 mg/kg dose on days 0, 3 and 5. In cohort 3, a 900 mg maternal dose was given during labor, followed by a 6 mg/kg infant dose on days 0, 3 and 5 of life.

RESULTS

Across all 3 cohorts, 89 infants had radiographs performed at either time point, and 85 had radiographs performed at both time points. Metaphyseal lucency was present in 1 case in Brazil and 2 in Malawi. Fifteen percent of infants from Brazil and 9% of infants from Malawi presented bone age discrepancies. No other abnormalities were identified in Brazil, whereas in Malawi, there were 7 more cases of wrist osteopenia, 2 of spine osteopenia and 3 other abnormalities.

CONCLUSION

Bone abnormalities were not uncommon in the overall cohort of HIV-exposed infants. Because of very limited study drug exposure at the time of birth, it is unlikely that TDF was associated with these findings. Untreated maternal HIV disease and/or maternal nutritional status could potentially be related to fetal bone development. This association should be explored in future cohort studies.

Bone health and HIV in resource-limited settings: a scoping review

PURPOSE OF REVIEW

Sub-Saharan Africa and other resource-limited settings (RLS) bear the greatest burden of the HIV epidemic globally. Advantageously, the expanding access to antiretroviral therapy (ART) has resulted in increased survival of HIV individuals in the last 2 decades. Data from resource rich settings provide evidence of increased risk of comorbid conditions such as osteoporosis and fragility fractures among HIV-infected populations. We provide the first review of published and presented data synthesizing the current state of knowledge on bone health and HIV in RLS.

RECENT FINDINGS

With few exceptions, we found a high prevalence of low bone mineral density (BMD) and hypovitaminosis D among HIV-infected populations in both RLS and resource rich settings. Although most recognized risk factors for bone loss are similar across settings, in certain RLS there is a high prevalence of both non-HIV-specific risk factors and HIV-specific risk factors, including advanced HIV disease and widespread use of ART, including tenofovir disoproxil fumarate, a non-BMD sparing ART. Of great concern, we neither found published data on the effect of tenofovir disoproxil fumarate initiation on BMD, nor any data on incidence and prevalence of fractures among HIV-infected populations in RLS.

SUMMARY

To date, the prevalence and squeal of metabolic bone diseases in RLS are poorly described. This review highlights important gaps in our knowledge about HIV-associated bone health comorbidities in RLS. This creates an urgent need for targeted research that can inform HIV care and management guidelines in RLS.

Maternal Tenofovir Disoproxil Fumarate Use in Pregnancy and Growth Outcomes among HIV-Exposed Uninfected Infants in Kenya

BACKGROUND

Tenofovir disoproxil fumarate (TDF) is commonly used in antiretroviral treatment (ART) and preexposure prophylaxis regimens. We evaluated the relationship of prenatal TDF use and growth outcomes among Kenyan HIV-exposed uninfected (HEU) infants.

MATERIALS AND METHODS

We included PCR-confirmed HEU infants enrolled in a cross-sectional survey of mother-infant pairs conducted between July and December 2013 in Kenya. Maternal ART regimen during pregnancy was determined by self-report and clinic records. Six-week and 9-month z-scores for weight-for-age (WAZ), weight-for-length (WLZ), length-for-age (LAZ), and head circumference-for-age (HCAZ) were compared among HEU infants with and without TDF exposure using t-tests and multivariate linear regression models.

RESULTS

Among 277 mothers who received ART during pregnancy, 63% initiated ART before pregnancy, of which 89 (32%) used TDF. No differences in birth weight (3.0 kg versus 3.1 kg, p = 0.21) or gestational age (38 weeks versus 38 weeks, p = 0.16) were detected between TDF-exposed and TDF-unexposed infants. At 6 weeks, unadjusted mean WAZ was lower among TDF-exposed infants (-0.8 versus -0.4, p = 0.03), with a trend towards association in adjusted analyses (p = 0.06). There were no associations between prenatal TDF use and WLZ, LAZ, and HCAZ in 6-week or 9-month infant cohorts.

CONCLUSION

Maternal TDF use did not adversely affect infant growth compared to other regimens.

Improvement in bone mineral density after switching from tenofovir to abacavir in HIV-1-infected patients with low bone mineral density: two-centre randomized pilot study (OsteoTDF study)

BACKGROUND

Tenofovir has been associated with a decrease in bone mineral density (BMD). However, data on changes in BMD after discontinuing tenofovir are lacking.

METHODS

We performed a two-centre randomized pilot study in virologically suppressed HIV-infected patients receiving tenofovir with osteopenia/osteoporosis (OsteoTDF study, ClinicalTrials.gov number NCT 01153217). Fifty-four patients were randomly assigned to switch from tenofovir to abacavir (n = 26) or to continue with tenofovir (n = 28). Changes in lumbar and total hip BMD were evaluated at Week 48 from baseline.

RESULTS

Five patients discontinued the study (three from the tenofovir group and two from the abacavir group). No significant differences were detected between the groups at Week 48 (P = 0.229 for total hip and P = 0.312 for lumbar spine). However, hip BMD improved by 2.1% (95% CI -0.6 to 4.7) (P = 0.043) in the abacavir group and 0.7% (95% CI -0.9 to 2.4) (P = 0.372) in the tenofovir group. Lumbar spine BMD varied by -0.7% (95% CI -3.8 to 3.3) (P ≤ 0.001) in the abacavir group and -1.2% (95% CI -3.8 to 0.4) (P < 0.001) in the tenofovir group.

CONCLUSIONS

Switching from tenofovir to abacavir led to a slight improvement in femoral BMD although no differences were detected between groups. Larger studies are necessary before firm recommendations can be made on the discontinuation of tenofovir in patients with a low BMD.

Randomized, placebo-controlled single-ascending-dose study to evaluate the safety, tolerability and pharmacokinetics of the HIV nucleoside reverse transcriptase inhibitor, BMS-986001, in healthy subjects

The objectives of this study were to evaluate the safety, tolerability and pharmacokinetics (PK) of BMS-986001 as a single oral dose in healthy male subjects. Sixty-four healthy male subjects were randomized to receive a single dose of BMS-986001 or placebo in this single-blind, placebo-controlled, sequential ascending-dose study. There were eight treatment groups (10, 30, 100, 300, 600, and 900 mg fed; and 100 and 300 mg fasted) of eight subjects each (BMS-986001 n = 6/placebo n = 2). BMS-986001 was well tolerated, with no serious adverse events (AEs), deaths, or discontinuations due to AEs reported. AEs were experienced by 14.6% of subjects receiving BMS-986001; however, these did not appear to be dose related and were not considered to be related to study drug. BMS-986001 was rapidly absorbed and exhibited a linear dose-exposure relationship across the dose range studied. PK appeared similar whether administered with or without food. Administration of BMS-986001 as a single dose was generally safe and well tolerated. A linear dose-exposure relationship was seen across all doses studied, with no apparent food effect. Further clinical development is warranted.

Development and validation of the first liquid chromatography-tandem mass spectrometry assay for simultaneous quantification of multiple antiretrovirals in meconium

A novel method for the simultaneous quantification of 16 antiretroviral (ARV) drugs and 4 metabolites in meconium was developed and validated. Quantification of 6 nucleoside/nucleotide reverse transcriptase inhibitors, 2 non-nucleoside reverse transcriptase inhibitors, 7 protease inhibitors, and 1 integrase inhibitor was achieved in 0.25 g of meconium. Specimen preparation included methanol homogenization and solid-phase extraction. Separate positive and negative polarity multiple reaction monitoring mode injections were required to achieve sufficient sensitivity. Linearity ranged from 10 to 75 ng/g up to 2500 ng/g for most analytes and 100-500 ng/g up to 25,000 ng/g for some; all correlation coefficients were ≥0.99. Extraction efficiencies from meconium were 32.8-119.5% with analytical recovery of 80.3-108.3% and total imprecision of 2.2-11.0% for all quantitative analytes. Two analytes with analytical recovery (70.0-138.5%) falling outside the 80-120% criteria range were considered semiquantitative. Matrix effects were -98.3-47.0% and -98.0-67.2% for analytes and internal standards, respectively. Analytes were stable (>75%) at room temperature for 24 h, 4 °C for 3 days, -20 °C for 3 freeze-thaw cycles over 3 days, and on the autosampler. Method applicability was demonstrated by analyzing meconium from HIV-uninfected infants born to HIV-positive mothers on ARV therapy. This method can be used as a tool to investigate the potential effects of in utero ARV exposure on childhood health and neurodevelopmental outcomes.

Bone turnover, osteoprotegerin/RANKL and inflammation with antiretroviral initiation: tenofovir versus non-tenofovir regimens

BACKGROUND

Bone mineral density decreases with antiretroviral therapy (ART) initiation, although the pathogenesis, including the role of tenofovir (TDF), is unclear. This study assessed changes in bone-turnover markers, osteoprotegerin (OPG), soluble receptor activator for nuclear factor-κβ ligand (sRANKL), and inflammation in subjects initiating TDF- versus non-TDF-containing regimens, and determined the relationship between bone turnover, OPG/sRANKL and inflammation.

METHODS

This was a longitudinal observational study comparing levels of bone turnover markers (C-terminal telopeptide of type I collagen [CTX] and osteocalcin [OC]), OPG, sRANKL and inflammatory cytokines (soluble tumour necrosis factor [TNF]-α receptor [sTNFR]-I, sTNFR-II and interleukin-6) prior to ART and 6-12 months after ART initiation with a TDF- versus non-TDF-containing regimen in HIV-infected subjects 18-50 years old.

RESULTS

A total of 87 subjects were enrolled (TDF n=44 and non-TDF n=43). Groups were similar except subjects on TDF had a lower CD4(+) T-cell nadir (P<0.01) and were more likely to receive a protease inhibitor (PI; P=0.03). At pre-ART, 35% and 1% of subjects had CTX and OC above the normal range, respectively. Both increased with ART initiation, whereas OPG, sRANKL and inflammatory markers significantly decreased. In multivariate models, increases in OC were associated with TDF use, PI use and pre-ART levels of sTNFR-I, whereas increases in CTX were associated with CD4(+) T-cell nadir <50 cell/mm³. Increases in bone markers were unrelated to pre-ART levels of OPG/sRANKL and changes in OPG/sRANKL after ART initiation.

CONCLUSIONS

TDF use, PI use, TNF-α activity and advanced HIV disease are associated with changes in bone turnover markers, underscoring the complicated interaction between ART, bone turnover, inflammation and immune status, which extend beyond the OPG/RANKL system.

Low CD4 count is associated with an increased risk of fragility fracture in HIV-infected patients

BACKGROUND

Low bone mineral density in HIV-infected patients is an increasingly recognized clinical problem. The aim of this study was to determine the incidence, prevalence, and risk factors for development of low trauma or fragility fractures in an HIV-infected population.

METHODS

A 1:2 matched case-control study was performed of HIV-infected patients attending the Alfred Hospital between 1998 and 2009. Controls were matched on gender, age, and duration of HIV infection.

RESULTS

The overall fracture incidence rate was 0.53 per 100 person-years [95% confidence interval (CI): 0.43 to 0.65] and period prevalence of 3.34 per 100 patients (95% CI: 2.66 to 4.13). There were 73 low trauma fractures in 61 patients. Patients were predominantly male (89%) with a mean age of 49.8 years. Independent risk factors for fragility fracture were a CD4 cell count <200 cells per microliter odds ratio (OR): 4.91 (95% CI: 1.78 to 13.57, P = 0.002), corticosteroids OR: 8.96 (95% CI: 1.55 to 51.88, P = 0.014) and anti-epileptic medications OR: 8.88 (95% CI: 1.75 to 44.97, P = 0.008). There were no significant associations between HIV viremia (P = 0.18), use of or class of antiretroviral medication, and risk of fracture. Eighty-eight percent of patients with fracture had established osteopenia or osteoporosis.

CONCLUSION

This is the largest clinical study to date of fragility fractures occurring in an HIV-infected population. The study found that risk of fracture was strongly associated with a low CD4 cell count, use of corticosteroids, and anti-epileptic medications. There were no associations between fracture risk and viral load, use of class, or duration of antiretroviral agent.

[Diagnosis and treatment of osteomalacia by the rheumatologist]

Osteomalacia is a metabolic bone disease characterized by an alteration of bone mineralization, frequently related to alterations in vitamin D or phosphate metabolism. The clinical symptoms, radiological and analytical findings of this process vary and may be confounded with other processes, especially osteoporosis. This article reviews the most frequent causes of osteomalacia, its diagnosis and therapeutic approaches.

Vitamin D status in children and young adults with perinatally acquired HIV infection

BACKGROUND & AIMS

To assess vitamin D (Vit-D) [serum 25-hydroxyvitamin D (25-OHD) concentrations] in children and young adults with perinatally acquired HIV compared to geographically similar healthy children.

METHODS

25-OHD in children and young adults with HIV was compared to a healthy group. Vit-D deficiency and insufficiency were defined as 25-OHD <11 ng/mL and 25-OHD <30 ng/mL, respectively.

RESULTS

Children with HIV (n = 81), mean age 13.8 ± 4.1 years, 48% female, 83% Black, were compared to healthy subjects (n = 372), mean age 12.4 ± 3.4 years, 51% female, 37% Black. For the HIV group, 84% were on HAART, 54% had plasma HIV RNA <400 cpm, and 35% had moderate to severe immunosuppression (CD4+ count <500 cells/mm). Vit-D deficiency/insufficiency was present in 36% and 89% of those with HIV, and 15% and 84% of the comparison group, respectively. Vit-D deficiency was more prevalent in those with HIV (unadjusted odds ratio: 3.25; 95% CI: 1.9-5.5). For both groups, prevalence of Vit-D deficiency increased with age, BMI Z-score, Black race, and in winter/spring months. Vit-D deficiency was associated with a greater degree of immunosuppression in the subjects with HIV.

CONCLUSIONS

Vit-D deficiency was increased in subjects with perinatally acquired HIV and may be associated with disease severity.

Tenofovir nephrotoxicity: 2011 update

Tenofovir is an acyclic nucleotide analogue reverse-transcriptase inhibitor structurally similar to the nephrotoxic drugs adefovir and cidofovir. Tenofovir is widely used to treat HIV infection and approved for treatment of hepatitis B virus. Despite initial cell culture and clinical trials results supporting the renal safety of tenofovir, its clinical use is associated with a low, albeit significant, risk of kidney injury. Proximal tubular cell secretion of tenofovir explains the accumulation of the drug in these mitochondria-rich cells. Tenofovir nephrotoxicity is characterized by proximal tubular cell dysfunction that may be associated with acute kidney injury or chronic kidney disease. Withdrawal of the drug leads to improvement of analytical parameters that may be partial. Understanding the risk factors for nephrotoxicity and regular monitoring of proximal tubular dysfunction and serum creatinine in high-risk patients is required to minimize nephrotoxicity. Newer, structurally similar molecular derivatives that do not accumulate in proximal tubules are under study.

Prevalence of bone mineral density abnormalities and related risk factors in an ambulatory HIV clinic population

Bone mineral density (BMD) abnormalities are observed frequently among human immunodeficiency virus (HIV)-infected patients. Risk factors for reduced BMD in the setting of HIV have been previously studied, but detailed antiretroviral treatment history is often not available. A cross-sectional observational study was conducted between 2005 and 2007 among unselected HIV-infected adults attending an ambulatory urban HIV clinic. Dual-energy X-ray absorptiometry (DXA) scans of lumbar spine and femoral neck, full laboratory profile, detailed questionnaire, and antiretroviral history were obtained. Univariate and multivariate logistic regression analyses were performed to investigate factors associated with BMD below the expected range for age. Two hundred ninety patients completed the study: 80% Caucasians, 89% males, with median age of 49 yr. Low BMD as assessed by Z-score was present in 19.7% of the patients. By multivariate analysis, only lower body mass index (BMI) was an independent risk factor for low BMD. Cumulative exposure to protease inhibitors, non-nucleosides, and individual nucleoside and nucleotide analogs were not independently associated with low BMD. In conclusion, a 19.7% prevalence of abnormal BMD by DXA scan was identified in an unselected group of HIV-infected adults. Lower BMI was independently associated with low BMD. No correlation was found between abnormal BMD and cumulative exposure to any antiretroviral agents.

Aging, human immunodeficiency virus, and bone health

Highly active antiretroviral therapy (HAART) has had a profound impact on improving the long-term prognosis for individuals infected with human immunodeficiency virus (HIV). HAART has been available for close to two decades, and now a significant number of patients with access to HAART are over the age of 50 years. Many clinical studies have indicated that HIV infection, as well as components of HAART, can increase the risk in these individuals to a variety of noninfectious complications, including a risk to bone health. There is a significant need for detailed mechanistic analysis of the aging, HIV-infected population regarding the risk of HIV infection and therapy in order to maintain bone health. Insights from basic mechanistic studies will help to shed light on the role of HIV infection and the components of HAART that impact bone health, and will help in identifying preventative countermeasures, particularly for individuals 50 years of age and older.

Growing up with HIV: children, adolescents, and young adults with perinatally acquired HIV infection

Tremendous success in the prevention and treatment of pediatric HIV in high-resource countries has changed the face of the epidemic. A perinatally HIV-infected child now faces a chronic disease rather than a progressive, fatal one. However, these successes pose new challenges as perinatally HIV-infected youth survive into adulthood. These include maintaining adherence to long-term, likely life-long therapy; selecting successive antiretroviral drug regimens, given the limited availability of pediatric formulations and the lack of pharmacokinetic and safety data in children; and overcoming extensive drug resistance in multi-drug-experienced children. Pediatric HIV care now focuses on morbidity related to long-term HIV infection and its treatment. Survival into adulthood of perinatally HIV-infected youth in high-resource countries encourages expansion of pediatric treatment programs in low-resource countries, where most HIV-infected children live, and provides important lessons about how the epidemic changes with increasing access to antiretroviral therapy for children.

Tenofovir treatment of primary osteoblasts alters gene expression profiles: implications for bone mineral density loss

There is strong clinical evidence that implicates tenofovir in the loss of bone mineral density during treatment of human immunodeficiency virus infection. In this study, we sought to test the hypothesis that tenofovir treatment of osteoblasts causes changes in the gene expression profile that would impact osteoblast function during bone formation. Primary osteoblasts were isolated and then treated with the tenofovir prodrug, tenofovir disoproxil fumarate (TDF). Total RNA from TDF-treated and untreated osteoblasts were extracted and used for microarray analysis to assess TDF-associated changes in the gene expression profile. Strikingly, the changes in gene expression profiles involved in cell signaling, cell cycle and amino acid metabolism, which would likely impact osteoblast function in bone formation. Our findings demonstrate for the first time that tenofovir treatment of primary osteoblasts results in gene expression changes that implicate loss of osteoblast function in tenofovir-associated bone mineral density loss.

Downregulation of Gnas, Got2 and Snord32a following tenofovir exposure of primary osteoclasts

Clinical observations have implicated the antiretroviral drug tenofovir with bone density loss during the management of HIV infection. The goal of this study was to investigate the in vitro effects of tenofovir exposure of primary osteoclasts in order to gain insights into the potential mechanisms for the drug-induced bone density loss. We hypothesized that tenofovir may alter the expression of key genes involved in osteoclast function. To test this, primary osteoclasts were exposed to physiologically relevant concentrations of the prodrug tenofovir disoproxil fumarate (TDF), then intensive microarray analysis was done to compare tenofovir-treated versus untreated cells. Specific downregulation of Gnas, Got2 and Snord32a were observed in the TDF-treated cells. The functions of these genes help to explain the basis for tenofovir-associated bone density loss. Our studies represent the first analysis of the effects of tenofovir on osteoclast gene expression and help to explain the basis of tenofovir-associated bone density loss in HIV-infected individuals.

Loss of bone mineral density after antiretroviral therapy initiation, independent of antiretroviral regimen

BACKGROUND

Decreased bone mineral density (BMD) has been described in HIV-infected patients initiating antiretroviral therapy (ART), but the contributions of ART and immunologic and/or virologic factors remain unclear.

METHODS

We compared total BMD changes over 96 weeks in 106 ART-naive HIV-infected subjects who were randomized to receive efavirenz (EFV) + zidovudine/lamivudine (n = 32) or lopinavir/ritonavir (LPV/r) + zidovudine/lamivudine induction (n = 74) for 24-48 weeks followed by LPV/r monotherapy. We also sought to identify factors associated with BMD loss, including markers of systemic inflammation [soluble tumor necrosis factor-alpha receptors (sTNFR I and II)].

RESULTS

After 96 weeks, the mean percent change from baseline in total BMD was -2.5% (LPV/r) and -2.3% (EFV) (P < 0.01 for within-group changes in either arm; P = 0.86 for between-group differences). No alteration in the rate of BMD change was observed upon simplification to LPV/r monotherapy. Although soluble tumor necrosis factor-alpha receptor II concentrations at baseline and 24 weeks were at least marginally associated with subsequent changes in BMD (P = 0.06 and P = 0.028, respectively), these associations were no longer significant after adjustment for CD4 T cell count. Subjects with lower baseline CD4 T cell count, non-black race, and higher baseline glucose demonstrated a higher risk for >5% decrease in BMD.

CONCLUSIONS

Similar decreases in BMD over 96 weeks occurred in ART-naive subjects receiving either EFV-based regimen or LPV/r-based regimen, which was not altered by simplification to LPV/r monotherapy and was unrelated to markers of tumor necrosis factor-alpha activity.

Evolution and predictors of change in total bone mineral density over time in HIV-infected men and women in the nutrition for healthy living study

BACKGROUND

Osteopenia is common in the era of effective antiretroviral therapy (ART), yet the etiology is unclear. We evaluated the association of host factors, disease severity, and ART to changes in total body bone mineral density (total BMD) over time in HIV-infected men (n = 283) and women (n = 96).

METHODS

Total BMD was measured annually by whole-body dual-energy absorptiometry (DXA), and medical, dietary, and behavioral history was collected. The median time from first to last DXA was 2.5 years (range 0.9-6.8 years). Using a repeated measures regression model, we identified variables independently associated with percent change in total BMD between consecutive DXA exams (n = 799 intervals), adjusted for age, race, sex, menopause, and smoking. We estimated percent change in total BMD over an average interval (1 year) standardized for representative levels of each determinant in males, premenopausal women, and postmenopausal women.

RESULTS

Median baseline age, CD4, and viral load were 42 years, 364 cells per cubic millimeter, and 2.7 log10 copies per milliliter, respectively. The estimated change in total BMD for those not on ART was -0.37% per year [95% confidence interval (CI) -0.76 to -0.02] for men, -0.08% per year (95% CI -0.49 to 0.33) for premenopausal women, and -1.07% per year (95% CI -1.86 to -0.28) for postmenopausal women. Greater loss of total BMD was associated with lower albumin, lower body mass index, prednisone/hydrocortisone use, tenofovir use, and longer duration of didanosine. Strength training and long duration of d4T and saquinavir prevented or mitigated bone loss. For those on ART for 3 years (not including the above agents), the rate of loss was -0.57% per year (95% CI -1.00 to -0.14) for men, -0.28% (95% CI -0.71 to 0.15) for premenopausal women, and -1.27% (95% CI -2.07 to -0.47) for postmenopausal women. Postmenopausal women had greater loss than premenopausal women and men.

CONCLUSIONS

Low body weight, low albumin, catabolic steroid use, and menopause may accelerate bone loss, and strength training may be protective. Tenofovir and didanosine may also have a deleterious effect on BMD.

Treatment of children with HIV infection

The treatment of pediatric HIV infection has seen vast improvements in terms of better long-term suppression of HIV replication and subsequent improvements in the longevity and quality of life in children. This has been realized, in part, by development of newer antiretroviral medications, better knowledge about the pharmaco-kinetics of these drugs in children, and improved insight on drug toxicities in children. This review will discuss some of the newer agents that may be available for children in the near future, in addition to new pharmacokinetic and toxicity data that are specific to the pediatric patient. New information on key vaccines that should be administered to children with HIV infection is also discussed.

Modulation of osteoclastogenesis induced by nucleoside reverse transcriptase inhibitors

Osteopenia is a common and debilitating side-effect of HAART, yet little is known concerning the effects of HAART on bone metabolism. We reported previously that zidovudine (AZT) stimulates osteoclastogenesis in vitro and causes osteopenia in mice. Here, we confirmed that the AZT-induced osteoclastogenesis is dependent on RANKL in that osteoclastogenesis is blocked by osteoprotegestin. Alendronate, which is used for the treatment of osteopenia and osteoporosis, failed to inhibit AZT-induced osteoclastogenesis in vitro. Osteoclastogenesis in vitro was not affected by tumor necrosis factor-alpha. Two other NRTI drugs, ddl and 3TC, also induced osteoclastogenesis in vitro and induced osteopenia in mice. The osteopenia was associated with an elevation of parameters of osteoclasts, but not with osteoblasts. Combinations of the NRTIs did not result in additive or synergistic effects in vitro or in vivo. Finally, AZT induced osteoclastogenesis of human osteoclast precursors in a RANKL-dependent manner. This in vitro osteoclastogenesis assay using human peripheral blood mononuclear cells could be useful in evaluating bone turnover and the risk of developing osteopenia in AIDS patients on HAART.

Tenofovir disoproxil fumarate and an optimized background regimen of antiretroviral agents as salvage therapy: impact on bone mineral density in HIV-infected children

OBJECTIVE

Tenofovir disoproxil fumarate, a nucleotide analog HIV reverse transcriptase inhibitor with demonstrated activity against nucleoside-resistant HIV, is approved for use in adults but not children. Metabolic bone abnormalities have been seen in young animals given high-dose tenofovir and HIV-infected adults that were treated with oral tenofovir disoproxil fumarate. However, tenofovir disoproxil fumarate is being used in children despite a lack of bone safety data. We hypothesized that, given the higher rate of bone turnover that is associated with normal skeletal growth, the potential for TDF-related bone toxicity may be greater in children than in adults.

METHODS

Fifteen highly antiretroviral-experienced HIV-infected children who were 8 to 16 years of age (mean +/- SD: 12 +/- 2) and required a change in therapy received tenofovir disoproxil fumarate 175 to 300 mg/m2 per day (adult dose equivalent) as part of highly active antiretroviral therapy for up to 96 weeks. Bone mineral density of the lumbar spine, femoral neck, and total hip by dual-energy x-ray absorptiometry and blood and urine markers of bone metabolism were measured at 0, 24, 48, 72, and 96 weeks.

RESULTS

Median z score (SD score compared with age, gender, and ethnicity-matched control subjects) of the lumbar spine, femoral neck, and total hip were decreased from baseline at 24 weeks and 48 weeks and then stabilized. Lumbar spine bone mineral apparent density (which estimates volumetric bone mineral density independent of bone size) z scores also decreased at 24 weeks. Absolute decreases in bone mineral density were observed in 6 children; the mean age of these children was significantly younger than the bone mineral density stable group (10.2 +/- 1.1 vs 13.2 +/- 1.8 years). The change in lumbar spine bone mineral density correlated with decreases in HIV plasma RNA during treatment. Metabolic markers of bone formation and resorption were variable. Two children in whom tenofovir disoproxil fumarate was discontinued because of bone loss that exceeded protocol allowances demonstrated partial or complete recovery of bone mineral density by 96 weeks.

CONCLUSIONS

Tenofovir disoproxil fumarate use in children seems to be associated with decreases in bone mineral density that, in some children, stabilize after 24 weeks. Increases in bone markers and calcium excretion suggest that tenofovir disoproxil fumarate may stimulate bone resorption. Bone turnover is higher in children than in older adolescents and adults because of skeletal growth, potentially explaining the greater effect seen in young children. Decreases in bone mineral density correlate with decreases in viral load and young age, suggesting that young responders may be at greater risk for bone toxicity.

Osteopenia and osteoporosis in patients with HIV: a review of current concepts

Since the advent of potent antiretroviral therapy in combination regimens, multiple epidemiologic studies have shown that osteopenia and osteoporosis are common among patients with HIV infection. However, there remain many areas of uncertainty about this potential complication, which can be confusing for the HIV clinician. This review summarizes the epidemiology, pathophysiology, suggested screening strategies, and management options of decreased bone mineral density in patients with HIV. Our aims are to review the available data, highlight controversial issues, and provide guidance for clinicians where supporting data are unavailable.

Tenofovir disoproxil fumarate and an optimized background regimen of antiretroviral agents as salvage therapy for pediatric HIV infection

OBJECTIVES

Highly active antiretroviral therapy has altered the course of HIV infection among children, but new antiretroviral agents are needed for treatment-experienced children with drug-resistant virus. Tenofovir disoproxil fumarate (DF) is a promising agent for use in pediatric salvage therapy, because of its tolerability, efficacy, and resistance profile. We designed this study to provide preliminary pediatric safety and dosing information on tenofovir DF, while also providing potentially efficacious salvage therapy for heavily treatment-experienced, HIV-infected children.

METHODS

Tenofovir DF, alone and in combination with optimized background antiretroviral regimens, was studied among 18 HIV-infected children (age range: 8.3-16.2 years) who had progressive disease with > or = 2 prior antiretroviral regimens, in a single-center, open-label trial. Tenofovir DF monotherapy for 6 days was followed by the addition of individualized antiretroviral regimens. Subjects were monitored with HIV RNA reverse transcription-polymerase chain reaction, flow cytometry, and routine laboratory studies; monitoring for bone toxicity included measurement of lumbar spine bone mineral density (BMD) with dual-energy x-ray absorptiometry. Subjects were monitored through 48 weeks.

RESULTS

Two subjects developed grade 3 elevated hepatic transaminase levels during monotherapy and were removed from the study. The remaining 16 subjects had a median of 4 antiretroviral agents (range: 3-5 agents) added to tenofovir DF. HIV plasma RNA levels decreased from a median pretreatment level of 5.4 log10 copies per mL (range: 4.1-5.9 log10 copies per mL) to 4.21 log10 copies per mL at week 48 (n = 15), with 6 subjects having < 400 copies per mL, including 4 with < 50 copies per mL. The overall median increases in CD4+ T cell counts were 58 cells per mm3 (range: -64 to 589 cells per mm3) at week 24 and 0 cells per mm3 (range: -274 to 768 cells per mm3) at week 48. The CD4+ cell responses among the virologic responders were high and sustained. The major toxicity attributed to tenofovir DF was a >6% decrease in BMD for 5 of 15 subjects evaluated at week 48, necessitating the discontinuation of tenofovir DF therapy for 2; all 5 subjects experienced >2 log10 copies per mL decreases in HIV plasma RNA levels.

CONCLUSIONS

Tenofovir DF-containing, individualized, highly active antiretroviral therapy regimens were well tolerated and effective among heavily treatment-experienced, HIV-infected children. Loss of BMD may limit tenofovir DF use among prepubertal patients.

Newer treatments for HIV in children

PURPOSE OF REVIEW

Several new antiretroviral agents have been introduced into pediatric and adult use. This review will summarize information about these new agents and other recent advances in the care of HIV-infected children.

RECENT FINDINGS

New drugs like tenofovir, emtricitabine, and enfuvirtide are being rapidly introduced into antiretroviral treatments for adult patients. In addition, some well-established drugs are being modified to make them more convenient (specifically didanosine and stavudine). Unfortunately, pediatric data lag for these new agents, in some cases because of complicated pharmacokinetics in children. At the same time, critical information on how to use established drugs like nelfinavir and efavirenz in younger children is slowly becoming available. Although antiretroviral treatment in children has often been initiated at standard doses of milligrams per kilogram, and susceptibility to drug was presumed in individuals without a previous history of exposure, recent data show that some primary infections are caused by drug-resistant virus, and there is a tremendous variability in serum drug levels in children. Researchers and clinicians should consider the role of baseline antiretroviral susceptibility testing and therapeutic drug monitoring to identify the optimal treatment for each child.

SUMMARY

New therapeutic options for children with HIV infection are becoming available as the pharmacokinetics and best strategies for use of newer drugs are studied.

Mitochondrial toxicity of NRTI antiviral drugs: an integrated cellular perspective

Highly active antiretroviral therapy (HAART) regimes based on nucleoside reverse transcriptase inhibitors (NRTIs) have revolutionized the treatment of AIDS in recent years. Although HAART can successfully suppress viral replication in the long term, it is not without significant toxicity, which can seriously compromise treatment effectiveness. A major toxicity that has been recognized for more than a decade is NRTI-related mitochondrial toxicity, which manifests as serious side effects such as hepatic failure and lactic acidosis. However, a lack of understanding of the mechanisms underlying mitochondrial toxicity has hampered efforts to develop novel drugs with better side-effect profiles. This review characterizes the pharmacological mechanisms and pathways that are involved in mitochondrial dysfunction caused by NRTIs, and suggests opportunities for future pharmacological research.