Tenofovir alafenamide (TAF), a new formulation that reaches higher levels in cells but allows for lower dosing, was as effective as the current tenofovir disoproxil fumarate (TDF) formulation but had less impact on markers of kidney function and bone turnover, researchers reported at the 53rd Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC 2013) this week in Denver.
Tenofovir (Viread, also in the Truvada, Atripla, Complera, and Stribild coformulations) is among the most widely used antiretroviral drugs, as it is highly effective and generally regarded as safe and well-tolerated. However, it can cause kidney toxicity in susceptible individuals and is associated with bone loss that begins soon after starting treatment. The long-term consequences of these side effects are a growing concern in light of guidelines recommending earlier treatment and expanding use of Truvada for pre-exposure prophylaxis (PrEP).
Gilead Sciences' new TAF formulation produces 5-fold higher concentrations of active tenofovir diphosphate in the cells that harbor HIV, but drug levels in the blood remain much lower compared with TDF. This enables reduced dosing that is expected to have less detrimental effects on the kidneys and bones.
Paul Sax from Brigham and Women's Hospital in Boston presented late-breaking results from a Phase 2 study (GS-US-292-0102) comparing TAF at 10 mg versus TDF at 300 mg, both as part of a single-tablet regimen that also includes the integrase inhibitor elvitegravir, cobicistat (a pharmacoenhancer or "booster"), and emtricitabine. The TDF-containing coformulation is marketed as Stribild; the TAF version is not yet approved. Given the apparent advantages of TAF, advocates have asked Gilead to request approval for the single agent as well as the new coformulation.
This double-blind, placebo-controlled trial included 170 previously untreated people with HIV who were randomly assigned (2:1) to receive the TAF or TDF coformulations once-daily for 48 weeks.
Almost all participants were men, more than two-thirds were white, nearly one-third were black, and the median age was about 35 years. The median baseline CD4 T-cell count was about 390 cells/mm3 (though about 15% had less than 200 cells/mm3) and the median viral load was approximately 40,000 copies/mL. At study entry they had normal kidney function with a median estimated glomerular filtration rate (eGFR) of 115 mL/min. People with hepatitis B or C coinfection were excluded.
they do it because TDF has a reputation for damaging kidney at higher rates then other drugs. That is why they lower the dose.
I don't think, basing dosing on HIV folks is the right way to go for HBV treatment strategies. HBV and HIV do not even compare in terms of damage that HIV does to the whole body at once.
And they may as well have made an improvement to the drug. So I think it is a good thing if they keep the same potency at lower dose. Because it is very true that how much of it is absorbed by cells that is what really counts..
no, tenofovir makes zero kidneys damage on hbv carriers so it is not useful, those with damaged kidneys already can combo tenofovir plus telbivudine because this combo improved kidneys function on damaged kidneys...as you can see you ll never know how these drug work from this combo
we dont know anything about this drug on hbv and drug makers dont work to cure but to keep income....
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