TAF: a new, safer version of tenofovir?

Tenofovir alafenamide versus tenofovir disoproxil fumarate, coformulated with elvitegravir, cobicistat, and emtricitabine, for initial treatment of HIV-1 infection: two randomised, double-blind, phase 3, non-inferiority trials.

Sax PE, Wohl D, Yin MT, Post F, DeJesus E, Saag M, Pozniak A, Thompson M, Podzamczer D, Molina JM, Oka S, Koenig E, Trottier B, Andrade-Villanueva J, Crofoot G, Custodio JM, Plummer A, Zhong L, Cao H, Martin H, Callebaut C, Cheng AK, Fordyce MW, McCallister S, GS-US-292-0104/0111 Study Team. Lancet. 2015 Jun 27;385(9987):2606-15. doi: 10.1016/S0140-6736(15)60616-X. Epub 2015 Apr 15.

Background: Tenofovir disoproxil fumarate can cause renal and bone toxic effects related to high plasma tenofovir concentrations. Tenofovir alafenamide is a novel tenofovir prodrug with a 90% reduction in plasma tenofovir concentrations. Tenofovir alafenamide-containing regimens can have improved renal and bone safety compared with tenofovir disoproxil fumarate-containing regimens.

Methods: In these two controlled, double-blind phase 3 studies, we recruited treatment-naive HIV-infected patients with an estimated creatinine clearance of 50 mL per min or higher from 178 outpatient centres in 16 countries. Patients were randomly assigned (1:1) to receive once-daily oral tablets containing 150 mg elvitegravir, 150 mg cobicistat, 200 mg emtricitabine, and 10 mg tenofovir alafenamide (E/C/F/tenofovir alafenamide) or 300 mg tenofovir disoproxil fumarate (E/C/F/tenofovir disoproxil fumarate) with matching placebo. Randomisation was done by a computer-generated allocation sequence (block size 4) and was stratified by HIV-1 RNA, CD4 count, and region (USA or ex-USA). Investigators, patients, study staff, and those assessing outcomes were masked to treatment group. All participants who received one dose of study drug were included in the primary intention-to-treat efficacy and safety analyses. The main outcomes were the proportion of patients with plasma HIV-1 RNA less than 50 copies per mL at week 48 as defined by the US Food and Drug Administration (FDA) snapshot algorithm (pre-specified non-inferiority margin of 12%) and pre-specified renal and bone endpoints at 48 weeks. These studies are registered with ClinicalTrials.gov, numbers NCT01780506 and NCT01797445.

Findings: We recruited patients from Jan 22, 2013, to Nov 4, 2013 (2175 screened and 1744 randomly assigned), and gave treatment to 1733 patients (866 given E/C/F/tenofovir alafenamide and 867 given E/C/F/tenofovir disoproxil fumarate). E/C/F/tenofovir alafenamide was non-inferior to E/C/F/tenofovir disoproxil fumarate, with 800 (92%) of 866 patients in the tenofovir alafenamide group and 784 (90%) of 867 patients in the tenofovir disoproxil fumarate group having plasma HIV-1 RNA less than 50 copies per mL (adjusted difference 2.0%, 95% CI -0.7 to 4.7). Patients given E/C/F/tenofovir alafenamide had significantly smaller mean serum creatinine increases than those given E/C/F/tenofovir disoproxil fumarate (0.08 vs 0.12 mg/dL; p<0.0001), significantly less proteinuria (median % change -3 vs 20; p<0.0001), and a significantly smaller decrease in bone mineral density at spine (mean % change -1.30 vs -2.86; p<0.0001) and hip (-0.66 vs -2.95; p<0.0001) at 48 weeks.

Interpretation: Through 48 weeks, more than 90% of patients given E/C/F/tenofovir alafenamide or E/C/F/tenofovir disoproxil fumarate had virological success. Renal and bone effects were significantly reduced in patients given E/C/F/tenofovir alafenamide. Although these studies do not have the power to assess clinical safety events such as renal failure and fractures, our data suggest that E/C/F/tenofovir alafenamide will have a favourable long-term renal and bone safety profile.

Abstract access  [1]

Editor’s notes: Tenofovir alafenamide fumarate (TAF) is a new antiretroviral agent developed by Gilead Sciences and is closely related to tenofovir disoproxil fumarate (TDF).  TDF is widely used, highly potent, and safe in the majority of people but long-term use has been associated with small risks of decreased kidney function, chronic kidney disease, and decreased bone mineral density.  Both TAF and TDF are prodrugs of tenofovir but TAF achieves highly potent concentrations of tenofovir inside HIV-relevant immune cells with much lower plasma concentrations than TDF.  The lower plasma concentration of tenofovir associated with TAF is hypothesised to reduce the toxic effects with regards to kidney and bone health. TAF is also effective at the lower dose of 10-25 mg, compared with the standard TDF dose of 300mg per day.  This may translate into lower drug costs if the lower dose required means lower manufacturing costs.

The authors report the combined results of two phase III, non-inferiority studies comparing the safety and effectiveness of TAF with TDF, funded by Gilead Sciences. In both studies, TAF was co-formulated into one, once-a-day tablet with elvitegravir, cobicistat and emtricitabine. There was a high rate of virologic suppression with the TAF-containing regimen, which was non-inferior to the TDF regimen. Compared to TDF, TAF had significantly more favourable effects on renal and bone parameters, with smaller decreases in creatinine clearance and bone mineral density and smaller increases in proteinuria. The real-world clinical significance of these findings remains to be seen but TAF-containing regimens may offer meaningful safety and cost benefits over TDF regimens in the long-term. The favourable characteristics of TAF have also led to the development of a sustained-release subcutaneous TAF implant, which has recently been evaluated in dogs. A long-acting TAF implant could have translational potential as a candidate for HIV prophylaxis in vulnerable populations.

HIV Treatment [4], People living with HIV [5], treatment [6]
Asia [7], Latin America [8], Northern America [9], Oceania [10]
Australia [11], Austria [12], Belgium [13], Dominican Republic [14], France [15], Germany [16], Italy [17], Mexico [18], Netherlands [19], Portugal [20], Spain [21], Sweden [22], Switzerland [23], Thailand [24], United Kingdom of Great Britain and Northern Ireland [25], United States of America [26]
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