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

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

Switching from tenofovir disoproxil fumarate to tenofovir alafenamide or dual therapy-based regimens in HIV-infected individuals with viral load ≤50 copies/mL: does estimated glomerular filtration rate matter?

Our aim was to evaluate the association between recent eGFR values and risk of switching from TDF to TAF or dual therapy (DT) in real life. HIV-positive patients achieving HIV-RNA ≤50 copies/mL for the first time after starting a TDF-based regimen were included. Kaplan-Meier (KM) curves and Cox regression models were used to estimate the time from TDF to switch to TAF or DT. 1486 participants were included: median (IQR) age 36 (30-42) years; baseline CKD-EPI eGFR 99.92 (86.47-111.4) mL/min/1.73m². We observed a consistently higher proportion of people with HIV-RNA ≤50 copies/mL who switched from TDF to TAF rather than to DT. By competing risk analysis, at 2 years from baseline, the probability of switching was 3.5% (95% CI 2.6-4.7%) to DT and 46.7% (42.8-48.5%) to TAF. A significantly higher probability of switching to TAF was found for patients receiving INSTI at baseline versus NNRTIs and PI/b [KM, 65.6% (61.7-69.4%) vs. 4.0% (1.8-6.1%) and 59.9% (52.7-67.2%), respectively; P < 0.0001]. eGFR <60 mL/min/1.73m² both as time-fixed covariate at baseline or as current value was associated with a higher risk of switching to DT [aHR 6.68 (2.69-16.60) and 8.18 (3.54-18.90); P < 0.001] but not to TAF-based cART [aHR 0.94 (0.39-2.31), P = 0.897; and 1.19 (0.60-2.38), P = 0.617]. Counter to our original hypothesis, current eGFR is used by clinicians to guide switches to DT but does not appear to be a key determinant for switching to TAF.

Consensus document of the Spanish Association for Study of the Liver on the treatment of hepatitis B virus infection (2020)

Hepatitis B virus (HBV) infection remains a global public health problem. HBV vaccination is the most effective tool to reduce the incidence of HBV disease. Despite there has not been new clinical developments for the treatment of chronic hepatitis B in the last few years, changing epidemiology and current insights on natural history, diagnostic tools and therapy indications make necessary an update of the former version of the consensus document of the Spanish Association for Study of the Liver on the treatment of hepatitis B infection published in 2012. The current document updates the management of chronic hepatitis B. The treatment of choice is the long-term administration of a nucleos(t)ide analogue with high barrier to resistance (entecavir, tenofovir or tenofovir alafenamide). Pegylated interferon may be an option in patients with non-advanced liver disease, but its applicability is limited due to the low efficacy and poor tolerability. All patients must be monitored for the risk of progression to advanced liver disease and development of hepatocellular carcinoma.

Renal proximal tubulopathy in an HIV-infected patient treated with tenofovir alafenamide and gentamicin: a case report

Background

The nucleotide reverse transcriptase inhibitor Tenofovir Alafenamide (TAF) is a novel pro-drug of tenofovir (TFV) and possesses a superior renal safety profile compared with tenofovir disoproxil fumerate (TDF). Due to unique pharmacokinetic characteristics, treatment with TAF is not associated with significant renal proximal tubular accumulation of TFV. TAF is associated with a lower risk of acute kidney injury, chronic kidney disease, proteinuria and renal proximal tubular dysfunction than treatment with TDF. No cases of Fanconi syndrome have been reported in clinical trials of TAF. It is unknown whether treatment with TAF can lead to accumulation of TFV in proximal tubular cells and cause nephrotoxicity under certain clinical circumstances.

Case presentation

Here we report the case of a patient on stable TAF-based antiretroviral therapy with for HIV-1 infection who developed proximal tubulopathy when treated with gentamicin for febrile neutropenia in the context of relapsed Hodgkin lymphoma. Eighteen days after commencing chemotherapy for relapsed Hodgkin lymphoma the patient presented to hospital with fevers, hypotension and neutropenia. The patient was commenced on piperacillin, tazobactam and gentamicin. Within 24 h the patient developed marked hypokalaemia and hypophosphataemia requiring intravenous replacement therapy. There was proteinuria, glycosuria and evidence of marked urinary electrolyte wasting, consistent with acute proximal tubular dysfunction. Eleven days after the gentamicin was stopped the serum biochemistry normalised. The urinary electrolyte wasting and proteinuria had improved, and the glycosuria had resolved.

Conclusion

This is the first case report to describe acute renal proximal tubulopathy in an HIV-infected patient treated with TAF and gentamicin. As the number of patients prescribed TAF outside the clinical trial setting increases, so too does the potential for previously unreported drug interactions and adverse events. Clinicians need to be aware of potential unreported adverse drug reactions as the use of TAF becomes increasingly common in clinical practice.

Recovery of Tenofovir-induced Nephrotoxicity following Switch from Tenofovir Disoproxil Fumarate to Tenofovir Alafenamide in Human Immunodeficiency Virus-Positive Patients

Background

Tenofovir disoproxil fumarate (TDF)-induced nephrotoxicity is related to high plasma tenofovir concentrations. Tenofovir alafenamide (TAF) is a tenofovir prodrug with 90% lower plasma tenofovir concentrations. The aim of this study was to evaluate changes in tenofovir-induced nephrotoxicity in Human Immunodeficiency Virus (HIV)-positive patients who switched from TDF to TAF.

Materials and Methods

We identified all HIV-positive patients who switched from elvitegravir/cobicistat/emtricitabine/TDF to elvitegravir/cobicistat/emtricitabine/TAF at a tertiary hospital. We assessed tubulopathy and renal dysfunction before TDF administration, at the time TAF was used following at least 3 months of TDF use, and 3 months after TAF administration. Tubulopathy was defined by the presence of at least three abnormalities in fractional excretion of phosphate, fractional excretion of uric acid, urinary β2-microglobulin, urinary N-acetyl-β-D-glucosaminidase, glucosuria or proteinuria. Renal dysfunction was defined as decreased by more than 25% in the estimated glomerular filtration rate (eGFR) relative to baseline.

Results

In 80 patients, the mean eGFR was 96.8 mL/min/1.73 m² before administration of TDF, 81.2 (P <0.001) at the time of change to TAF, 90.9 (P <0.001) after TAF administration. Renal dysfunction occurred in 19 patients (23.8%) after TDF use for a median 15 months, 11 (57.9%) of these patients recovered from renal dysfunction after TAF administration. Six patients (7.5%) had tubulopathy before TDF administration, 36 (45.0%) after TDF administration (P <0.001), 12 (15.0%) after TAF administration (P = 0.002).

Conclusion

Tenofovir-induced nephrotoxicity in HIV-positive patients receiving TDF was mostly reversible after changing to TAF. Thus, TAF-containing regimens can be administered safely to HIV-positive patients with tenofovir-induced nephrotoxicity.

Barriers to the Wider Use of Pre-exposure Prophylaxis in the United States: A Narrative Review

Antiretroviral pre-exposure prophylaxis (PrEP) to prevent HIV transmission was first approved by the US Food and Drug Administration in 2012. Despite correlations of decreases in new HIV infections being greatest where PrEP has been deployed, the uptake of PrEP is lagging, particularly among populations with disproportionate HIV burden. This narrative review seeks to identify individual and systemic barriers to PrEP usage in the USA. A comprehensive search of recent literature uncovered a complex array of structural, social, clinical, and behavioral barriers, including knowledge/awareness of PrEP, perception of HIV risk, stigma from healthcare providers or family/partners/friends, distrust of healthcare providers/systems, access to PrEP, costs of PrEP, and concerns around PrEP side effects/medication interactions. Importantly, these barriers may have different effects on specific populations at risk. The full potential of PrEP for HIV prevention will not be realized until these issues are addressed. Strategies to achieve this goal should include educational interventions, innovative approaches to delivery of HIV care, financial support, and destigmatization of PrEP and PrEP users. Until then, PrEP uptake will continue to be suboptimal, particularly among those who need it most.

An expert review on the use of tenofovir alafenamide for the treatment of chronic hepatitis B virus infection in Asia

Asia has intermediate-to-high prevalence and high morbidity of hepatitis B virus (HBV) infection. The use of guideline-recommended nucleos(t)ide analogs with high barrier to resistance, such as entecavir (ETV), tenofovir disoproxil fumarate (TDF), and tenofovir alafenamide (TAF), is one of the key interventions for curbing HBV infection and associated morbidity in Asia. However, there are some challenges to the use of ETV and TDF; while ETV is associated with high resistance in lamivudine (LAM)-exposed (especially LAM-refractory) patients; bone and renal safety issues are a major concern with TDF. Hence, a panel of twenty-eight expert hepatologists from Asia convened, reviewed the literature, and developed the current expert opinion-based review article for the use of TAF in the resource-constrained settings in Asia. This article provides a comprehensive review of two large, phase 3, double-blind, randomized controlled trials of TAF versus TDF in HBeAg-negative (study 0108) and HBeAg-positive (study 0110) chronic HBV patients (> 70% Asians). These studies revealed as follows: (1) non-inferiority for the proportion of patients who had HBV DNA < 29 IU/mL; (2) significantly high rate of normalization of alanine aminotransferase levels; (3) no incidence of resistance; and (4) significantly better bone and renal safety, with TAF vs. TDF up to 144 weeks. Considering the benefits of TAF, the expert panel proposed recommendations for optimizing the use of TAF in Asia, along with guidance on specific patient groups at risk of renal or bone disease suitable for TAF therapy. The guidance provided in this article may help clinicians optimize the use of TAF in Asia.

Bictegravir, a novel integrase inhibitor for the treatment of HIV infection

Bictegravir (BIC), a second-generation integrase strand transfer inhibitor (INSTI) approved for HIV treatment in fixed-dose combination with emtricitabine and tenofovir alafenamide, has potent antiviral activity in vitro to wild-type virus and strains with resistance to first-generation INSTIs. As part of combination therapy, BIC's virologic suppression rates in clinical trials are comparable to those of first-line combination antiretroviral drug regimens. BIC has demonstrated a high genetic barrier to resistance development in vitro, can be administered with or without food, and has a bioavailability of > 70%. A median plasma half-life of 18 hours allows once-daily dosing. Clearance is primarily hepatic through cytochrome P450 3A4 (CYP3A4) oxidation and UDP-glucuronosyltransferase 1A1 (UGT1A1) glucuronidation. Thus, potent inducers of UGT1A1 and CYP3A4 (e.g., rifamycins/anticonvulsants) should be avoided due to significantly decreased BIC serum exposure. Chelation with polyvalent cations can decrease absorption; otherwise, drug-drug interactions are few. BIC is well tolerated; diarrhea, nausea and headache are the main adverse effects associated with its use.

Renal function change after switching tenofovir disoproxil fumarate for tenofovir alafenamide in the HIV-positive patients of a metropolitan sexual health service

Background

Tenofovir disoproxil fumarate (TDF) is widely used in the management of HIV-infection, but has been associated with renal impairment in a small proportion of patients. Tenofovir alafenamide (TAF), a novel prodrug of tenofovir, causes less renal impairment and can improve renal function in patients switched from TDF. The factors which predict improved renal function in patients switching from TDF to TAF have yet to be described.

Aim

To determine which patient factors are associated with an improvement in renal function following the switch from a TDF- to a TAF-based HIV antiretroviral regimen.

Methods

A retrospective analysis was performed of a cohort from a publicly funded sexual health clinic in Sydney, Australia. All HIV-positive clinic patients switched from a TDF- to TAF-containing regimen between January 2016 and August 2018 were eligible for inclusion. Laboratory results were obtained from patients’ electronic medical records. The statistical significance of differences between pre- and post-switch means was determined by paired t-tests, adjusted for baseline values, and associations between continuous variables by univariate linear regression.

Results

79 patients met inclusion criteria. The majority were male (89%), with a median age of 44 years (IQR: 34.5 to 53). Patients had a mean pre-switch estimated glomerular filtration rate (eGFR) of 95 ± 2 mL/min/1.73 m², and there was no significant change post-switch (p = 0.062). Pre-switch eGFR was a significant predictor of the magnitude of eGFR change after the switch (p < 0.001), but there was no significant association with age (p = 0.189), cumulative TDF exposure (p = 0.454) or baseline urinary protein to creatinine ratio (p = 0.814).

Conclusion

While there was no significant difference in mean eGFR, in patients switched from TDF to TAF, baseline eGFR was a significant predictor of the change in eGFR. This suggests that patients on TDF with poorer baseline renal function would benefit more from switching to TAF. Further study to explore this association is warranted.

Rates and predictors of switching to tenofovir alafenamide-containing ART in a nationwide cohort

Background

Tenofovir alafenamide (TAF)-containing combinations were introduced in Switzerland after October 2016 and are recommended over tenofovir disoproxil fumarate (TDF) in patients with osteoporosis or impaired renal function.

Methods

We included all participants of the Swiss HIV Cohort Study on TDF-containing antiretroviral therapy with follow-up visits after January 2016. We determined the proportion of switches from TDF to TAF overall, and among patients with risk factors for TDF toxicity, including osteoporosis, impaired renal function or marked proteinuria. We used multivariable logistic regression to explore predictors of switching from TDF to TAF.

Results

We included 5′012 patients, of whom 652 (13.0%) had risk factors for TDF toxicity. A switch from TDF to TAF was undertaken in 2′796 (55.8%) individuals overall, and in 465 (71.3%) with risk factors. Predictors of switching to TAF were male sex (adjusted odds ratio 1.27, 95% confidence interval 1.07–1.50), age > 50 years (1.43, 1.23–1.66) and the presence of risk factors for TDF toxicity (2.21, 1.77–2.75). In contrast, patients with a non-nucleoside reverse transcriptase inhibitor (NNRTI)-based single-pill regimen (0.11, 0.09–0.13), those treated in non-tertiary care centers (0.56, 0.46–0.70), as well as those with CD4 cell counts below 500/μL (0.77, 0.66–0.90) and with chronic hepatitis C infection (0.66, 0.54–0.80) were most likely to stay on TDF.

Conclusions

Over 50% of patients on TDF-containing therapy, including the majority of patients at risk for TDF toxicity, were switched to TAF within two years of its introduction in Switzerland. Individuals on NNRTI-based single-pill regimens were most likely to remain on TDF.

Unmet need in chronic hepatitis B management

Despite all these exciting developments, there remain some unmet needs in the management for patients with chronic hepatitis B (CHB). As majority of CHB patients are going to use oral nucleos(t)ide analogues (NAs) for decades, Safety profile of NAs is of no doubt an important issue. The newest nucleotide analogue tenofovir alafenamide is potent in terms of viral suppression, together with favourable renal and bone safety profile. Biochemical response as reflected by alanine aminotransferase (ALT) normalization is recently found to be prognostically important. Patients who achieved ALT normalization have reduced the risk of hepatic events by 49%. Functional cure as reflected by hepatitis B surface antigen seroclearance not only implies patients may stop NA treatment, it also confers to a reduced risk of hepatocellular carcinoma and other hepatic events. Hence functional cure should be the ultimate treatment goal in CHB patients. Preemptive antiviral treatment may reduce mother-to-child transmission of hepatitis B virus, especially if birth dose of vaccination cannot be given in the first two hours after delivery. Lastly, despite the currently first-line NAs have high-genetic barrier to drug resistance mutations, there are still are many patients who were previously treated with low barrier of resistance including lamivudine, telbivudine or adefovir dipivoxil which could lead to antiviral resistance and affecting the choice of NAs.

Tolerability of Current Antiretroviral Single-Tablet Regimens

The advent of protease inhibitors (PI) in the mid-nineties and its use as part of triple combinations revolutionized the management of HIV infection. Since then, progression to AIDS and AIDS-related deaths can be prevented. However, antiretroviral therapy based on PI has been discouraged for a while given its lower tolerability compared to alternative options; and only recent improvements in pharmacotherapy have renewed the interest for the newest agents within this class. First, the tolerability of the latest PI darunavir (DRV) and atazanavir is much better than for older PI, such as indinavir or lopinavir. Second, metabolic abnormalities and/or drug interactions associated to ritonavir boosting have been ameliorated using cobicistat. Third, adding safer accompanying nucleos(t)ides, such as tenofovir alafenamide (TAF), have minimized further toxicity concerns of PI. Finally, the unique barrier to resistance and new single-tablet regimen (STR) presentation makes DRV, especially attractive for long-term therapy. The recent coformulation of DRV, cobicistat, TAF, and emtricitabine (DRV/c/TAF/FTC) within a single pill to be given once daily (Symtuza^®) has positioned PI again at the frontline of HIV therapeutics. In this review, we discuss the results of studies that have assessed the efficacy and safety of the newest STR. In view of the current data, it seems worthy expanding the consideration of Symtuza® for a wider range of clinical scenarios, beyond the treatment of antiretroviral failures including first-line therapy and switching of otherwise virologically suppressed patients. The good tolerability and robust resistance profile should reward Symtuza^® and position it among the preferred contemporary STRs.

Nanoencapsulation introduces long-acting phenomenon to tenofovir alafenamide and emtricitabine drug combination: A comparative pre-exposure prophylaxis efficacy study against HIV-1 vaginal transmission

Daily oral antiretroviral (ARV) drugs for pre-exposure prophylaxis (PrEP) has proven efficacy for diverse groups of high-risk individuals. However, daily dosing regimen has augmented non-adherence. These experiments comparatively investigated the long-acting (LA) PrEP potency of subcutaneous (SubQ) administrated tenofovir alafenamide (TAF) and emtricitabine (FTC) loaded nanoparticles (NPs) to solution in humanized (hu) mice. TAF + FTC NPs and TAF + FTC solution (each drug at 200 mg/kg) were administered to hu-CD34-NSG mice (n = 3/time point) for plasma and tissue pharmacokinetic parameter estimation using LC-MS/MS. NP enhanced tissue ARV assimilation compared to plasma. The same dose was administered for PrEP efficacy in HIV-1 challenged hu-BLT mice (n = 5/group). The hu-BLT mice were vaginally challenged with a transmission-founder (T/F) virus at 5 × 10⁵ TCID₅₀ inoculation, on day 4, 7 and 14 post-SubQ treatments (PT) and were compared to infected-untreated-control hu-BLT mice. By 21 days PT, 100% TAF + FTC solution-treated and control-untreated mice were infected. However, TAF + FTC NPs resulted in significant (p = .0002) protection from HIV-1 (day 4: 80%, day 7 and 14: 60%, respectively) compared to control mice. This proof-of-concept study demonstrated detectable TAF/FTC vaginal levels among TAF + FTC NP-treated hu-BLT mice correlating with prolonged PrEP efficacy, thus establishing long-acting TAF + FTC NPs as a potential PrEP modality.

Taiwan consensus statement on the management of chronic hepatitis B

The experts of Taiwan Association for the Study of Liver (TASL) have actively participated and led the guidelines on hepatitis B virus (HBV) management by Asian Pacific Association for the Study of Liver (APASL) which is the first international association for the study of liver to publish the statement on HBV management before. However, there are more and more new data on the natural history and treatment of HBV infection in the past decade. These include new application of an old biomarker (quantitative HBsAg), clinical significance of HBV genotype and naturally occurring mutations, the role of non-invasive examination in evaluating severity of hepatic fibrosis, clinical significance of outcome calculators, new drug or new combination strategies towards more effective therapy and organ transplantation including liver and non-liver transplantation. It is time to publish the guidelines on HBV management of Taiwan. Hence, TASL have conducted an expert meeting to review, to discuss and to debate the relevant literatures, followed by draft the manuscript of HBV management guidelines and recommendations. The guidelines include general management, indications for fibrosis assessment, time to start or stop drug therapy, choice of drug to initiate therapy, when and how to monitor the patients during and after stopping drug therapy. Recommendations on the therapy of patients in special circumstances, including women in childbearing age, patients with antiviral drug resistance, concurrent viral infection, hepatic decompensation, patient receiving immune suppression or chemotherapy and patients in the setting of liver transplantation and hepatocellular carcinoma, are also included.

Incident hepatocellular carcinoma developing during tenofovir alafenamide treatment as a rescue therapy for multi-drug resistant hepatitis B virus infection: A case report and review of the literature

Tenofovir disoproxil fumarate (TDF) is a potent nucleotide analogue with high barrier to resistance, which is recommended for multi-drug resistant hepatitis B virus (HBV) infection. However, nephrotoxicity has been reported during TDF treatment, and tenofovir alafenamide (TAF), which has comparable efficacy to TDF and improves bone and renal safety, can be used as a replacement strategy. Herein, we describe a clinical case concerning a 60-year-old individual suffering liver cirrhosis and renal dysfunction, and being infected with multidrug-resistant HBV. When failing treatment with TDF, he received TAF as a rescue therapy. TAF effectively inhibited HBV replication without worsening renal function or serum phosphorus abnormality. Furthermore, hepatocellular carcinoma (HCC) occurred during TAF treatment despite controlling the viral load. The risk of HCC could not be eliminated and should be monitored during TAF treatment.

Long-acting parenteral combination antiretroviral loaded nano-drug delivery system to treat chronic HIV-1 infection: A humanized mouse model study

Human immunodeficiency virus (HIV) patients are often diagnosed in the chronic stage of HIV/AIDS. Combination antiretroviral therapy (cART) has improved quality of life for HIV-infected patients. Present study describes a novel long-acting parenteral formulation of combination antiretroviral (cARV) loaded nano-drugs for treating chronic HIV-1 (cHIV) in a humanized-BLT (hu-BLT) mice model. The cARV (elvitegravir+tenofovir alafenamide+emtricitabine; EVG+TAF+FTC) drugs (mimicking marketed Genvoya^® one-pill for HIV-treatment) were encapsulated in poly (lactic-co-glycolic acid) nanoparticles (NPs). To establish cHIV, hu-BLT mice were intravaginally challenged with HIV-1 and maintained for 15 weeks. Plasma viral load (pVL) was monitored by RT-PCR to confirm cHIV. Baseline pVL (week 15) was comparable between treated (n = 10) and control (n = 5) mice groups. Subsequently, treatment hu-BLT mice received 3 subcutaneous doses of cARV NPs (417 mg/kg per dose; n = 10), biweekly, and a fourth/terminal dose a week later. Prior to each treatment and on sacrifice (week 24), pVL was determined. Within three subcutaneous doses of cARV NPs, a non-detectable pVL was established (week 19) and continued until week 22. After the establishment of a non-detectable pVL (week 19-22), 4 treated-mice were sacrificed for tissue drug concentration determination by LC-MS/MS analysis. A considerable amount of cARV was detected at the HIV-infection target and reservoir organs. Subsequently, pVL rebounded comparable to control group by week 24, (7 weeks post-terminal dosage). The present study demonstrated cARV NPs augments sustained ARV efficacy in the cHIV humanized-mouse model. Therefore, cARV NPs could be a novel delivery system to treat cHIV patients, by overcoming drawbacks of conventional cART.

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

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

Rare emergence of drug resistance in HIV-1 treatment-naïve patients receiving elvitegravir/cobicistat/emtricitabine/tenofovir alafenamide for 144 weeks

BACKGROUND

The single tablet regimen (STR) composed of elvitegravir (E), cobicistat (C), emtricitabine (F), and tenofovir alafenamide (TAF) (E/C/F/TAF) was compared to the STR composed of E, C, F, and tenofovir disoproxil fumarate (TDF) (E/C/F/TDF) in 2 phase 3 studies in 1733 HIV-1 infected treatment-naïve adults. Superior efficacy of E/C/F/TAF compared to E/C/F/TDF was demonstrated at Week 144 with 84% treatment success compared to 80%, respectively, along with significantly better outcomes of bone and renal safety.

OBJECTIVES

Analyze the emergence of HIV-1 resistance in treatment-naïve adults receiving E/C/F/TAF for 144 weeks.

STUDY DESIGN

We conducted an integrated resistance analysis of the 2 Phase 3 studies, comprising pretreatment HIV-1 sequencing for all participants (N = 1733) and post-baseline HIV-1 resistance analysis for participants with virologic failure (HIV-1 RNA ≥400 copies/mL).

RESULTS

Primary resistance-associated mutations (RAMs) were observed pre-treatment in 7.4% (NRTI-RAMs), 18.1% (NNRTI-RAMs), and 3.3% (PI-RAMs) of enrolled subjects. Baseline HIV-1 subtype or pre-existing RAMs did not affect E/C/F/TAF treatment response at week 144. Virologic failure resistance analyses were conducted for 28/866 (3.2%) and 30/867 (3.5%) patients in the E/C/F/TAF and E/C/F/TDF arms, respectively. Over the 3-year study, the rate of resistance emergence remained low at 1.4% in each group (12/866 in E/C/F/TAF; 12/867 in E/C/F/TDF). Resistant virus emerged in 24 patients who developed resistance to antiretrovirals in the regimens (E/C/F/TAF: M184V/I [1.3%], INSTI-RAMs [0.9%], K65R/N [0.2%]; E/C/F/TDF: M184V/I [1.0%], INSTI-RAMs [0.9%], K65R/N [0.5%]).

CONCLUSIONS

Resistance emergence was rare (1.4%) with similar patterns of emergent mutations in both groups. M184V/I was the most prevalent RAM (1.2% overall).

Simultaneous determination of tenofovir alafenamide and its active metabolites tenofovir and tenofovir diphosphate in HBV-infected hepatocyte with a sensitive LC-MS/MS method

Tenofovir (TFV), a first-line anti-viral agent, has been prepared as various forms of prodrugs for better bioavailability, lower systemic exposure and higher target cells loading of TFV to enhance efficacy and reduce toxicity. TFV undergoes intracellular phosphorylation to form TFV diphosphate (TFV-DP) in target cell to inhibit viral DNA replication. Hence, TFV-DP is the key active metabolite that exhibits anti-virus activity, its intracellular exposure and half-life determine the final activity. Therefore, simultaneous monitoring prodrug, TFV and TFV-DP in target cells will comprehensively evaluate TFV prodrugs, both considering the stability of ester prodrug, and the intracellular exposure of TFV-DP. Thus we intended to develop a convenient general analytical method, taking tenofovir alafenamide (TAF) as a representative of TFV prodrugs. A sensitive LC-MS/MS method was developed, and TAF, TFV and TFV-DP were separated on a XSelect HSS T3 column (4.6mm×150mm, 3.5μm, Waters) with gradient elution after protein precipitation. The method provided good linearity for all the compounds (2-500nM for TFV and TAF; 20-5000nM for TFV-DP) with the correlation coefficients (r) greater than 0.999. Intra- and inter-day accuracies (in terms of relative error, RE<10.4%) and precisions (in terms of coefficient of variation, CV<14.1%) satisfied the standard of validation. The matrix effect, recovery and stability were also within acceptable criteria. Finally, we investigated the intracellular pharmacokinetics of TAF and its active metabolites in HepG2.2.15 cells with this method.

Efficacy and safety of emtricitabine/tenofovir alafenamide (FTC/TAF) vs. emtricitabine/tenofovir disoproxil fumarate (FTC/TDF) as a backbone for treatment of HIV-1 infection in virologically suppressed adults: subgroup analysis by third agent of a randomized, double-blind, active-controlled phase 3 trial<sup/>

BACKGROUND

FTC/TAF was shown to be noninferior to FTC/TDF with advantages in markers of renal and bone safety.

OBJECTIVE

To evaluate the efficacy and safety of switching to FTC/TAF from FTC/TDF by third agent (boosted protease inhibitor [PI] vs. unboosted third agent).

METHODS

We conducted a 48-week subgroup analysis based on third agent from a randomized, double blind study in virologically suppressed adults on a FTC/TDF-containing regimen who switched to FTC/TAF vs. continued FTC/TDF while remaining on the same third agent.

RESULTS

We randomized (1:1) 663 participants to either switch to FTC/TAF (N = 333) or continue FTC/TDF (N = 330), each with baseline third agent stratifying by class of third agent in the prior treatment regimen (boosted PI 46%, unboosted third agent 54%). At week 48, significant differences in renal biomarkers and bone mineral density were observed favoring FTC/TAF over FTC/TDF (p < 0.05 for all), with similar improvements in the FTC/TAF arm in those who received boosted PI vs. unboosted third agents. At week 48, virologic success rates were similar between treatment groups for those who received a boosted PI (FTC/TAF 92%, FTC/TDF 93%) and for those who received an unboosted third agent (97% vs. 93%).

CONCLUSIONS

In virologically suppressed patients switching to FTC/TAF from FTC/TDF, high rates of virologic suppression were maintained, while renal and bone safety parameters improved, regardless of whether participants were receiving a boosted PI or an unboosted third agent. FTC/TAF offers safety advantages over FTC/TDF and can be an important option as an NRTI backbone given with a variety of third agents.

Tenofovir alafenamide fumarate for the treatment of HIV infection

Tenofovir alafenamide fumarate is a recently developed prodrug of tenofovir, a nucleotide analogue reverse transcriptase inhibitor with potent inhibitory activity against HIV. The utility of a previously developed tenofovir prodrug, tenofovir disoproxil fumarate, had been hampered by renal and bone mineral adverse events. Tenofovir alafenamide fumarate overcomes the shortcomings of tenofovir disoproxil fumarate by delivering high intracellular concentrations of the parent drug, tenofovir, while substantially reducing systemic exposure. Tenofovir alafenamide fumarate is currently available as a component of three fixed-dose products: i) coformulation with emtricitabine; ii) coformulation with elvitegravir, cobicistat and emtricitabine; and iii) coformulation with rilpivirine and emtricitabine.

Tenofovir alafenamide, emtricitabine, elvitegravir, and cobicistat combination therapy for the treatment of HIV

INTRODUCTION

Tenofovir alafenamide (TAF) is a novel prodrug of the nucleotide analogue reverse-transcriptase inhibitor, tenofovir. TAF has been co-formulated with emtricitabine (FTC), elvitegravir (EVG) and the EVG metabolic enhancer, cobicistat (COBI) as a single-tablet regimen being the first TAF-containing antiretroviral combination available. Areas covered: This article summarizes the available information on the pharmacology of the novel compound TAF and overviews TAF/FTC/EVG/COBI use for HIV-1 infected patients, with specific focus on clinical efficacy and safety data. Information sources include peer-reviewed scientific literature, conference proceedings and publically available regulatory reports. Compared to tenofovir disoproxil fumarate, TAF results in higher concentrations of the active metabolite tenofovir diphosphate within lymphoid cells, whereas plasma tenofovir exposure is about 90% lower. The efficacy and safety of TAF/FTC/EVG/COBI in treatment-naïve HIV-infected patients has been assessed in phase-III randomized trials, showing non-inferior virological suppression in comparison with TDF/FTC/EVG/COBI, and significantly lower renal and bone toxicity. In addition, TAF/FTC/EVG/COBI has demonstrated efficacy and safety as a switching strategy in suppressed HIV-1 infected individuals, including those with mild or moderate renal impairment. Expert commentary: Approval of the single-tablet TAF/FTC/EVG/COBI regimen is an important advance in HIV therapy, as it is associated with very high efficacy and a better kidney and bone safety profile compared to TDF-containing regimens due to the incorporation of TAF.

Tenofovir alafenamide (TAF) does not deplete mitochondrial DNA in human T-cell lines at intracellular concentrations exceeding clinically relevant drug exposures

HIV-infected patients treated with certain nucleoside reverse transcriptase inhibitors (NRTIs) have experienced adverse effects due to drug-related mitochondrial toxicity. Tenofovir alafenamide (TAF) is a novel prodrug of the NRTI tenofovir (TFV) with an improved safety profile compared to tenofovir disoproxil fumarate (TDF). Prior in vitro studies have demonstrated that the parent nucleotide TFV has no significant effects on mtDNA synthesis. This study investigated whether clinically relevant TAF and TDF exposures affect mtDNA content in human lymphocytes. First, activated or resting peripheral blood mononuclear cells (PBMCs), as well as MT-2 and Jurkat T-cell lines, were continuously treated with ddC for 10 days to establish their susceptibility to mtDNA depletion. PBMCs had low sensitivity to NRTI-mediated mtDNA depletion in vitro. In contrast, ddC treatment of rapidly dividing MT-2 and Jurkat cells resulted in a dose-dependent decrease in mtDNA. Therefore, these two T-cell lines were selected for evaluating TAF and TDF treatment effects. MT-2 and Jurkat cells were pulse-treated with TAF or TDF every 24 h for 10 days to mimic pharmacologically relevant drug exposures. Pulse treatment of cells with 3.3 μM TAF or 1.1 μM TDF for 10 days resulted in 2- to 7-fold greater steady-state intracellular TFV-diphosphate (TFV-DP) levels than those observed clinically in TAF- or TDF-treated patients. At these concentrations, no significant TAF- (106.7% and 84.1% of control; p = 0.77 and 0.12 for MT-2 and Jurkat, respectively) or TDF- (100.6% and 91.0% of control; p = 0.91 and 0.37, respectively) associated reduction in mtDNA content was observed compared with untreated control cells. This study demonstrates that, despite delivering higher intracellular levels of TFV-DP than TDF, TAF does not inhibit mtDNA synthesis in vitro at concentrations exceeding the clinically relevant intracellular drug exposures. Thus, TAF has a low potential for mitochondrial toxicity in T-cells of HIV-infected patients.

Equivalent Decline in Inflammation Markers with Tenofovir Disoproxil Fumarate vs. Tenofovir Alafenamide

Background

Initiation of antiretroviral therapy (ART) and subsequent virologic suppression reduces immune activation and systemic inflammation.

Methods

We examined longitudinal changes in biomarkers of monocyte activation (sCD14, sCD163), and systemic (IL-6, hsCRP, sTNFR-I and D-dimer) and vascular (Lp-PLA₂) inflammation in a subgroup (N = 100 per arm) of participants enrolled in a randomized, placebo-controlled trial comparing elvitegravir/cobicistat/emtricitabine/tenofovir alafenamide (E/C/F/TAF; TAF) to E/C/F/tenofovir disoproxil fumarate (E/C/F/TDF; TDF) in treatment-naïve adults.

Results

For 194 participants (TAF, 98; TDF, 96), baseline levels of biomarkers did not differ by treatment arm; there were no differences in biomarker values between groups at weeks 12, 24, or 48 (p > 0.05), except IL-6 at week 12 (p = 0.012). Among all participants (combining groups), there were statistically significant declines from baseline observed for D-dimer, sCD163, and sTNFR-1 by week 12 and IL-6 by week 24. The proportion of participants with Lp-LA₂ levels < 200 ng per mL (p = 0.250) or hsCRP levels < 3000 mg per L (p = 0.586) was unchanged through week 48.

Conclusions

We observed equivalent declines in biomarkers of monocyte activation and systemic inflammation in treatment-naïve adults treated with TAF or TDF for 48 weeks, suggesting that TAF and TDF have equivalent impact on immune activation and inflammation.

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Persons infected with HIV continue have residual immune activation and inflammation despite virologic suppression.

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Several markers of immune activation and inflammation are associated with mortality and cardiovascular disease (CVD).

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Decline in these markers is equivalent with tenofovir alafenamide and tenofovir disoproxil fumarate.

Biomarkers of immune activation and inflammation are associated with non AIDS–associated comorbidities and all-cause mortality. TDF decreased inflammatory markers associated with cardiovascular risk in treatment-naïve individuals. Studies have demonstrated that TAF is as efficacious at virologic suppression as TDF, and safer regarding renal and bone toxicity, but treatment differences in decline of immune activation and inflammation have not been explored. Results of our study suggest that TAF is equivalent to TDF in reducing markers of immune activation and inflammation associated with all-cause mortality, while providing an improved renal and bone safety profile compared with TDF.

Rare emergence of drug resistance in HIV-1 treatment-naïve patients after 48 weeks of treatment with elvitegravir/cobicistat/emtricitabine/tenofovir alafenamide

Tenofovir alafenamide (TAF), a novel prodrug of the NtRTI tenofovir (TFV), delivers TFV-diphosphate (TFV-DP) to target cells more efficiently than the current prodrug, tenofovir disoproxil fumarate (TDF), with a 90% reduction in TFV plasma exposure. TAF, within the fixed dose combination of elvitegravir /cobicistat / emtricitabine (FTC)/TAF (E/C/F/TAF), has been evaluated in one Phase 2 and two Phase 3 randomized, double-blinded studies in HIV-infected treatment-naive patients, comparing E/C/F/TAF to E/C/F/TDF. In these studies, the TAF-containing group demonstrated non-inferior efficacy to the TDF-containing comparator group with 91.9% of E/C/F/TAF patients having <50 copies/mL of HIV-1 RNA at week 48. An integrated resistance analysis across these three studies was conducted, including HIV-1 genotypic analysis at screening, and genotypic/phenotypic analysis for patients with HIV-1 RNA>400 copies/mL at virologic failure. Pre-existing primary resistance-associated mutations (RAMs) were observed at screening among the 1903 randomized and treated patients: 7.5% had NRTI-RAMs, 18.2% had NNRTI-RAMs, and 3.4% had primary PI-RAMs. Pre-treatment RAMs did not influence treatment response at Week 48. In the E/C/F/TAF group, resistance development was rare; seven patients (0.7%, 7/978) developed NRTI-RAMs, five of whom (0.5%, 5/978) also developed primary INSTI-RAMs. In the E/C/F/TDF group, resistance development was also rare; seven patients (0.8%, 7/925) developed NRTI-RAMs, four of whom (0.4%, 4/925) also developed primary INSTI-RAMs. An additional analysis by deep sequencing in virologic failures revealed minimal differences compared to population sequencing. Overall, resistance development was rare in E/C/F/TAF-treated patients, and the pattern of emergent mutations was similar to E/C/F/TDF.